CA2065584C

CA2065584C - Plate-like polarizing element, a polarizing conversion unit provided with the element, and a projector provided with the unit

Info

Publication number: CA2065584C
Application number: CA002065584A
Authority: CA
Inventors: Hideaki Mitsutake; Noritaka Mochizuki; Shigeru Kawasaki; Kazumi Kimura; Junko Shingaki
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1991-04-09
Filing date: 1992-04-08
Publication date: 1996-02-13
Anticipated expiration: 2012-04-08
Also published as: DE69221002D1; US5566367A; US6229646B1; ATE155898T1; EP0508413A2; EP0508413A3; JP3273955B2; EP0508413B1; CA2065584A1; JPH04310903A; DE69221002T2

Abstract

This specification discloses a plate-like polarizing element for converting light into polarized light having a plurality of units arranged along a common plane across the light, each of the units being provided with dividing means for dividing the light into reflected light and transmitted light whose planes of polarization are orthogonal to each other, varying means for varying the polarized state of at least one of the reflected light and the transmitted light to thereby make the planes of polarization of the two lights coincident with each other, and reflecting means for reflecting one of the reflected light and the transmitted light and directing it substantially in the same direction as the direction of travel of the other. The specification also discloses a polarizing conversion unit provided with such plate-like polarizing element, and a projector provided with such unit.

Description

1 A PLATE-LIKE POLARIZING ELEMENT, A POLARIZING
CONVERSION UNIT PROVIDED WITH THE ELEMENT, AND A PROJECTOR PROVIDED WITH THE UNIT

BACKGROUND OF THE INVENTION
Field of the Invention This invention relates to a plate-like polarizing element, a polarizing conversion unit provided with the element, and a projector provided with the unit.
Related Background Art As an apparatus for converting non-polarized light having a random plane of polarization into polarized light, an apparatus described in Japanese Laid-Open Patent Application No. 61-90584 is shown in Figure 1 of the accompanying drawings.
In this projector, non-polarized parallel light emerging from a condenser lens 104 enters a polarizing beam splitter 111, and P-polarized light Lp is intactly transmitted through the acting surface (evaporated film formed on an inclined surface on which two rectangular prisms are adhesively secured to each other3 llla of the polarizing beam splitter 111, while S-polarized light LS is upwardly reflected at a right angle and enters a total reflection prism 112. The S-polarized light LS is rightwardly reflected at a right angle by the total reflection prism 112, whereby it emerges from the total reflection prism 112 in the 2065~8~

1 same direction as the P-polarized light Lp transmitted through the polarizing beam splitter 111. The S-polarized light LS refers to rectilinearly polarized light having a plane of polarization parallel to the acting surface llla of the polarizing beam splitter 111, and the P-polarized light Lp refers to rectilinearly polarized light having a plane of polarization orthogonal to the S-polarized light Ls. A half wavelength ~late 113 is disposed on the emergence side of the total reflection prism 112, and the S-polarized light Ls which has emerged from the total reflection prism 112 is transmitted through the half wavelength plate 113, whereby the plane of polarization thereof is rotated by 90 and the S-polarized light LS is converted into P-polarized light Lp . Also, wedge type lenses 114 and 115 for changing optical path are disposed on the emergence sides of the polarizing beam splitter 111 and the half wavelength plate 113, respectively, and the P-polarized light Lp transmitted through the polarizing beam splitter 111 and the P-polarized light Lp converted by the half wavelength plate 113 have their optical paths changed, and intersect each other at a point PO on the incidence side surface of a liquid crystal light bulb 117 and become combined light.
Accordingly, in this projector, the liquid crystal light bulb 117 can be illuminated by both of the S-polarized light Ls and the P-polarized light 206-~58~

l Lp separated by the polarizing beam splitter 111.
However, the above-described projector of Japanese Laid-Open Patent Application No. 61-90584 requires the large polarizing beam splitter 111 and total reflection prism 112, and this leads to the disadvantage that the entire apparatus becomes bulky and heavy.

SUMMARY OF THE INVENTION
It is the object of the present invention to provide a plate-like polarizing element which can cause non-polarized light emitted from a light source to enter an image generator without any loss and can contribute to the compactness of a projector, a projector, a polarizing conversion unit provided with the element, and a projector provided with the unit.
The plate-like polarizing element of the present invention comprises a plurality of units each having~
a dividing portion for dividing incident light into reflected light and transmitted light whose planes of polarization are orthogonal to each other, a reflect-ing portion for reflecting one of said reflected light and said transmitted light and directing it substantially in the same direction as the direction of travel of the other, and a modulating portion for varying the plane of polarization of at least one of said reflected light and said transmitted light to thereby make the planes of polarization of the two coincident with each 1 other, said units being juxtaposed.
The polarizing conversion unit of the present invention has the plate-like polarizing element of the present invention, and conversion means provided on the incidence side of the plate-like polarizing element for converting non-polarized light into non-polarized light of a fence-like pattern or converting non-polarized light into non-polarized light of lattice-like pattern.
The projector of the present invention is such that the illuminating optical system thereof has the polarizing conversion unit of the present invention, or the image generator thereof has three generators for generating red, green and blue images, respectively, lS and the illuminating optical system has a color resolving system for resolving non-polarized light into red, green and blue non-polarized lights, and the polarizing conversion unit of the present invention provided in the optical path of the non-polarized light of each color.
Or the image generator has three generators for generating rèd, green and blue images, respectively, and the illuminating optical system has a color resolving system for resolving non-polarized light into red, green and blue non-polarized lights, and the polarizing conversion units of the present invention provided in the common optical path of two of non-polarized ~_ - 5 -1 lights of three colors and the optical path of non-polarized light of the other color, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows the construction of the essential portions of a projector according to the prior art.
Figure 2 is a construction view of the unit 20 of a plate-like polarizing element showing a first embodiment of the plate-like polarizing element of the present invention.
Figure 3 is a fragmentary view showing an example of the construction of a plate-like polarizing element constructed by juxtaposing a plurality of units 20 shown in Figure 2.
Figure 4 is a fragmentary view showing another example of the construction of a plate-like polarizing element constructed by juxtaposing a plurality of units 20 shown in Figure 2.
Figure 5 is a construction view of the unit 20a of a plate-like polarizing element showing a second embodiment of the plate-like polarizing element of the present invention.
Figure 6 is a construction view of the unit 30 of a plate-like polarizing element showing a third embodiment of the plate-like polarizing element of the present invention.
Figure 7 is a construction view of the unit -l 30a of a plate-like polarizing element showing a fourth embodiment of the plate-like polarizing element of the present invention.
Figure 8 is a construction view of the unit 30b of a plate-like polarizing element showing a fifth embodiment of the plate-like polarizing element of the present invention.
Figure 9 is a perspective view showing a_portion of a first embodiment of the polarizing conversion unit of the present invention.
Figure 10 illustrates the operation of a both-surface lenticular lens 42 shown in Figure 9.
Figure 11 is a schematic construction view showing a first embodiment of the projector of the present invention.
Figure 12 is a schematic construction view showing a second embodiment of the projector of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
Some embodiments of the present invention will hereinafter be described with reference to the drawings.
Figure 2 is a construction view of the unit 20 of a plate-like polarizing element showing a first embodiment of the plate-like polarizing element of the present invention.

The unit 20 of the plate-like polarizing element ~_ _ 7 1 of the present embodiment comprises a first incidence side prism 211 having the shape of a triangle pole of right-angled triangular cross-section, first and second emergence side prisms 221 and 222 having the same shape as the first incidence side prism 211 and disposed adjacent to the first incidence side prism 211 with their inclined surfaces in contact with one another, a second incidence side prism 212 having a half of the shape of the first incidence side prism 211 and disposed on that side of the first emergence side prism 221 opposite to the first incidence side prism 211 with their inclined surfaces in contact with each other, and a third incidence side prism 213 having the same shape of the second incidence side prism 212 and disposed on that side of the second emergence side prism 222 opposite to the first incidence side prism 211 with their inclined surfaces in contact with each other, and the three incidence side prisms 211 - 213 and the two emergence side prisms 221 and 222 together constitute a plane parallel plate. On the surface of contact between the first incidence side prism 211 and the first emergence side prism 221, a first quarter wavelength plate 231 is provided on the first incidence side prism 211 side, and first polarization separation acting film 241 is provided on the first emergence side prism 221 side. Further, on the surface of contact between the first incidence side prism 21 ~_ - 8 1 and the second emergence side prism 222, a second quarter wavelength plate 232 is provided on the first incidence side prism 211 side, and second polarization separation acting film 242 is provided on the second emergence side prism 222 side. A first total reflection mirror 251 is formed on the surface of contact between the second incidence side prism 212 and the first emergence side prism 221, and a second total reflection mirror 252 is formed on the surface of contact between the third incidence side prism 213 and the second emergence side prism 222. The first and second polarization separation acting films 241 and 242 have the charac-teristic of reflecting S-polarized light having a plane of polarization parallel to the film surface and transmitting therethrough P-polarized light having a plane of polarization perpendicular to the film surface. Also, the first and second quarter wavelength plates 231 and 232 act on light incident at an incidence angle of 45 like first and second incident lights Pl and P2, and the directions of the optical axis thereof are selected so as to convert S-polarized light into circularly polarized light.
That is, in the unit 20 of the plate-like polarizing element of the present embodiment, the surface of contact between the first incidence side prism 211 and the first emergence side prism 221 and the surface of contact between the first incidence _ _ 9 _ 1 side prism 211 and the second emergence side prism 222 function as a pair of polarizing dividing surfaces having substantially the same angles of inclination wïth respect to non-polarized light (first and second incident lights Pl and P2) and facing each other so that the reflected light from one of them (first and second S-polarized lights LSl and LS2) may travel toward the other, and the first and second polarization separation acting films 241 and 242 function as a dividing portion which divides the incident light into reflected light (first and second S-polarized light LSl and LS2) and transmitted light (first and second P-polarized lights Lpl and Lp2) whose planes of polariza-tion are orthogonal to each other. Also, the first lS and second total reflection mirrors 251 and 252 function as a reflecting portion which reflects one (first and second S-polarized lights LSl and LS2) of the reflected light and the transmitted light) and directs it substantially in the same direction as the direction of travel of the other (first and second P-polarized lights Lpl and Lp2). Further, the first and second quarter wavelength plates 231 and 232 function as a modulating portion which varies the plane of polariza-tion of at least one (first and second S-polarized lights LSl and LS2) of the reflected light and the transmitted light to thereby make the planes of polarization of the two lights coincident with each 20~5584 l other.
The operation of the unit 20 of the plate-like polarizing element of the present embodiment will now be described.
The first incident light Pl having a random plane of polarization which is incident at an incidence angle of 45 with respect to the surface of contact between the first incidence side prism 21l and the first emergence side prism 221 is divided into first P-polarized light Lpl and first S-polarized light LSl by the first P-polarized light Lpl which is transmitted through the first quarter wavelength plate 23l and thereafter enters the first polarization separation acting film 241 and has a plane of polarization perpendicular to the film surface being transmitted through the first polarization separation acting film 241 and the first S-polarized light LSl which has a plane of polarization paralle to the film surface being reflected rightwardly at a right angle by the first polarization separation acting film 24l. The first P-polarized light Lpl emerges from the exit surface of the first emergence side prism 22l. On the other hand, the first S-polarized light LSl is transmitted through the first quarter wavelength plate 23l and is thereby converted into circularly polarized light, whereafter it is transmitted through the second quarter wavelength plate 232 and is thereby converted into 2065~84 1 first converted P-polarized light Lpl having a plane of polarization perpendicular to the film surface of the second polarization separation acting film 242.
The first converted P-polarized light Lpl is transmit-ted through the second polarization separation actingfilm 242, whereafter it is reflected upwardly at a right angle by the second total reflection mirror 252 and emerges from the exit surface of the second emergence side prism 222 in the same direction as the direction of travel of the first P-polarized light Lpl ~
Also, the second incident light P2 having a random plane of polarization which is incident at an incidence angle of 45 with respect to the surface of contact between the first incidence side prism 21 and the second emergence side prism 222 is divided into second P-polarized light Lp2 and second S-polarized light LS2 by the second P-polarized light Lp2 which is transmitted through the second quarter wavelength plate 232 and thereafter enters the second polarization separation acting film 242 and has a plane of polariza-tion perpendicular to the film surface being transmitted through the second polarization separation acting film 242 and the second S-polarized light LS2 which has a plane of polarization parallel to the film surface being reflected leftwardly at a right angle by the second polarization separation acting film 242. The 206558~

1 second P-polarized light Lp2 emerges from the exit surface of the second emergence side prism 222. On the other hand, the second S-polarized light LS2 is transmitted through the second quarter wavelength plate 232 and is thereby converted into circularly polarized light, whereafter it is transmitted through the first quarter wavelength plate 231 and is thereby converted into second converted P-polarized light Lp2 hav'ng a plane of polarization perpendicular to the film surface of the first polarization separation acting film 241. The second converted P-polarized light Lp2 is transmitted through the first polarization separation acting film 241, whereafter it is reflected upwardly at a right angle by the first total reflection mirror 251 and emerges from the exit surface of the first emergence side prism 221 in the same direction as the direction of travel of the second P-polarized light Accordingly, the unit 20 of the plate-like polarizing element of the present embodiment can convert the first and second incident lights Pl and P2 incident on the first incidence side prism 211 into the first and second P-polarized lights Lpl and Lp2 and the first and second converted P-polarized lights Lpl and Lp2 without any loss and can cause them to emerge from the whole exit surface.

206558~

1 Description will now be made of the material of each constituent of the unit 20 of the plate-like polarizing element of the present embodiment.
The first, second and third incidence side prisms 211 - 213 and the first and second emergence side prisms 221 and 222 can be formed of glass or plastic, but to keep the separating function of the first and second polarization separation acting films 241 and 242 optimal, those prisms may preferably be formed of glass having a great degree of freedom of refractive index selection. Also, a combination of plane parallel plates is possible instead of using prisms, but in such case, the transmittance of P-polarized light is inferior to the case where prisms are used. The first and second quarter wavelength plates 231 and 232 can be formed of a crystalline material such as mica or rock crystal, dilated high molecular film, low molecular liquid crystal having a predetermined thickness and oriented with the molecular axes thereof uniformized in a predetermined direction, side chain type high molecular liquid crystal or low molecular liquid crystal dispersed in high molecules.
The first and second polarization separation acting films 241 and 242 can be formed of conventional optical multilayer film, but use can be made of any material having a polarization separation characteristic such as cholesteric liquid crystal. As the first and second `_ 1 total reflection mirrors 251 and 252, use may be made of aluminum evaporated mirrors, or the second and third incidence side prisms 212 and 213 can be eliminated and those inclined surfaces of the first and second emergence side prisms 221 and 222 which are opposite to the first incidence side prism 211 can be made into air boundary surfaces to thereby form total reflection surfaces.
This unit 20 can be made thinner and lighter in weight than the combination of the polarizing beam splitter 111 and the total reflection prism 112 shown in Figure 1, and thus leads to the possibility of realizing a compact and light-weight projector.
To construct a much thinner and lighter-weight polarizing element, the unit 20 can be made compact and a plurality of such units can be juxtaposed.
The polarizing element shown in Figure 2, as compared with a polarizing element as shown later in Figure 5 wherein wavelength plate is disposed parallel to the incident light, has the effect that no middle omission occurs to the emergent light. This is because if the wavelength plate is disposed parallel to the incident light, it is apparent that middle omission will occur correspondingly to the thickness of the wavelength plate.
An example of the construction in which a plurality of units 20 shown in Figure 2 are juxtaposed 1 to construct a plate-like polarizing element is a plate-like polarizing element 41 as shown in Figure 3 wherein a plurality of units 20 are laterally juxtaposed. Another example of the construction is a plate-like polarizing element 41a as shown in Figure 4 wherein adjacent ones of rows each comprising a plurality of units 20 laterally juxtaposed are arranged with the pitch thereof shifted by one half. In ~he plate-like polarizing elements 41 and 41a shown in Figures 3 and 4, respectively, the incidence side prisms which provide the connecting surfaces of adjacent units (the second incidence side prism 212 and the third incidence side prism 213 shown in Figure 1) may be constructed integrally with each other.
Figure 5 is a construction view of the unit 20a of a plate-like polarizing element showing a second embodiment of the plate-like polarizing element of the present invention.
The difference of the unit 20a of the plate-like polarizing element of the present embodiment from the unit 20 of the plate-like polarizing element shown in Figure 2 is that instead of the first and second quarter wavelength plates 231 and 232, a half wavelength plate 26 is provided intermediately of the surface of contact between the first incidence side prism 211 and the first emergence side prism 221 and the surface of contact between the first incidence side prism 211 '~ -1 and the second emergence side prism 222.
In the unit 20a of the plate-like polarizing element of the present embodiment, the first incident light Pl is divided into first P-polarized light Lpl and first S-polarized light LSl by the first P-polarized light Lpl being transmitted through the first polariza-tion separation acting film 241 and the first S-polarized light being reflected rightwardly at a right angle by the first polarization separation acting film 241. The first P-polarized light Lpl emerges from the exit surface of the first emergence side prism 221. On the other hand, the first S-polarized light LSl has its plane of polarization rotated by 90 by being transmitted through the half wavelength plate 26 and is converted into first converted P-polarized light Lpl . The first converted P-polarized light Lpl is transmitted through the second polarization separation acting film 242, whereafter it is reflected upwardly at a right angle by the second total reflection mirror 252 and emerges from the exit surface of the second emergence side prism 222 in the same direction as the direction of travel of the first P-polarized light Lpl. The second incident light P2 is divided into second P-polarized light Lp2 and second S-polarized light LS2 by the second P-polarized light Lp2 being transmitted through the second polarization separation acting film 242 and the second S-polarized light LS2 206558~

1 being reflected leftwardly at a right angle by the second polarization separation acting film 242. The second P-polarized light Lp2 emerges from the exit surface of the second emergence side prism 222. On the other hand, the second S-polarized light LS2 has its plane of polarization rotated by 90 by being transmitted through the half wavelength plate 26 and is converted into second converted P-polarized light Lp2*. The second converted P-polarized light Lp2 is transmitted through the first polarization separation acting film 241, whereafter it is reflected upwardly at a right angle by the first total reflection mirror 251 and emerges from the exit surface of the first emergence side prism 221 in the same direction as the direction of travel of the second P-polarized light Lp2. Accordingly, the unit 20a of the plate-like polarizing element of the present embodiment also can convert the first and second incident lights Pl and P2 incident on the first incidence side prism 211 into the first and second P-polarized lights Lpl and Lp2 and the first and second converted P-polarized lights Lpl and Lp2 without any loss and cause them to emerge from the whole exit surface. The half wavelength plate 26 may be provided anywhere between the surface of contact between the first incidence side prism 211 and the first emergence side prism 221 and the surface of contact between the first incidence side prism 211 206558~

1 and the second emergence side prism 222.
Figure 6 is a construction view of the unit 30 of a plate-like polarizing element showing a third embodiment of the plate-like polarizing element of the present invention.
The unit 30 of the plate-like polarizing element of the present embodiment is of a construction in which a dividing portion (polarization separation acting film 34) is disposed obliquely with respect to non-polarized light (incident light P), a reflecting portion(total reflection film 35) is disposed parallel to the dividing portion and as a modulating portion, a half wavelength plate 36 is disposed in the optical path of reflected light (S-polarized light Ls), lS particularly the optical path of the reflected light (S-polarized light Ls) reflected by the reflecting portion (total reflection film 35).
That is, the unit 30 of the plate-like polarizing element of the present embodiment comprises a first glass member 311 of parallelogrammatic cross-sectional shape and second and third glass members 312 and 313 of right-angled triangular cross-sectional shape arranged adjacent to the both sides of the first glass member 311 with the inclined surfaces thereof in contact with one another, and the three glass members 311 - 313 together constitute a plane parallel plate. Total reflection film 35 is provided on the surface of contact 206558~
~" ".

1 between the first glass member 311 and the second glass member 312, and polarization separation acting film 34 is provided on the surface of contact between the first glass member 311 and the third glass member 313.
Further, a half wavelength plate 36 is provided on the exit surface of the first glass member 311 (that surface of the first glass member which is opposite to the surface on which the incident light P is incident).
The polarization separation acting film 34 has a characteristic of reflecting S-polarized light having a plane of polarization parallel to the film surface and transmitting therethrough P-polarized light having a plane of polarization perpendicular to the film surface.
Also, the half wavelength plate 36 acts on light incident at an incidence angle of 90. Accordingly, in the unit 30 of the plate-like polarizing element of the present embodiment, the polarization separation acting film 34 functions as a dividing portion which divides the incident light into reflected light (S-polarized light Ls) and transmitted light (P-polarized light Lp) whose planes of polarization are orthogonal to each other. Also, the total reflection film 35 functions as a reflecting portion which reflects one (S-polarized light Ls) of the reflected light and the transmitted light and directs it substantially in the same direction as the direction of travel of the other (P-polarized light Lp). Further, the half wavelength plate 36 20655g~

1 functions as a modulating portion which varies the plane of polarization of at least one (S-polarized light Ls) of the reflected light and the transmitted light to thereby make the planes of polarization of the two lights coincident with each other.
The operation of the unit 30 of the plate-like polarizing element of the present embodiment will now be described.
The incident light P having a random plane of polarization which is incident on the film surface of the polarization separation acting film 34 at an incidence angle of 45 is divided into P-polarized light Lp and S-polarized light Ls by the P-polarized light Lp which has a plane of polarization perpendicular to the film surface being transmitted through the polarization separation acting film 34 and the S-polarized light LS which has a plane of polarization parallel to the film surface being reflected leftwardly at a right angle by the polarization separation acting film 34. The P-polarized light Lp emerges from the exit surface of the third glass member 313 (that surface of the third glass member which is opposite to the surface on which the incident light P is incident).
On the other hand, the S-polarized light Ls is reflected upwardly at a right angle by the total reflection film 35 and emerges from the exit surface of the second glass member 312 in the same direction as the direction - 21 - 206558~

1 of travel of the P-polarized light Lp, whereafter it is transmitted through the half wavelength plate 36, whereby it has its plane of polarization rotated by 90 and is converted into P-polarized light Lp .
Accordingly, the unit 30 of the plate-like polarizing element of the present embodiment can convert the incident light P incident on the first glass member 311 into the P-polarized light Lp and the converted P-polarized light Lp without any loss and cause them to emerge from the whole exit surface. In the present embodiment, polarization separation acting film can also be used in lieu of the total reflection film 35.
Examples of the construction in which a plurality of units 30 shown in Figure 6 are juxtaposed to construct a plate-like polarizing element include the examples shown in Figures 3 and 4 wherein the units 30 are juxtaposed like the units 20 shown in Figure 2. The unit 30 shown in Figure 6 can be constructed by juxtapos-ing a plurality of glass members of parallelogrammatic cross-sectional shape when constructing a plate-like polarizing element and therefore, has the effect that it is more excellent in workability than the unit 20 shown in Figure 2. The unit 30 shown in Figure 6 can be constructed by juxtaposing a plurality of glass members of parallelogrammatic cross-sectional shape when constructing a plate-like polarizing element and therefore, has the effect that it is more excellent 206558~

_ 1 in workability than the unit 20 shown in Figure 2.
That is, the unit 30 can be easily made by alternately laminating glass plates having polarization separation acting film 34 provided on one surface thereof and glass plates having total reflection film 35 (for example, aluminum evaporated film) provided on one surface thereof, severing them along a cross-section of 45, optically polishing the severed surfaces, and thereafter adhesively securing a half wavelength plate 36 thereto.
Figure 7 is a construction view of the unit 30a of a plate-like polarizing element showing a fourth embodiment of the plate-like polarizing element of the present invention.
The difference of the unit 30a of the plate-like polarizing element of the present embodiment from the unit 30 of the plate-like polarizing element shown in Figure 6 is that a half wavelength plate 36 is disposed between polarization separation acting film 34 (a dividing portion) and total reflection film 35 (a reflecting portion).
In the unit 30a of the plate-like polarizing element of the present embodiment, the incident light P is divided into P-polarized light Lp and S-polarized light LS by the P-polarized light Lp being transmitted through the polarization separation acting film 34 and the S-polarized light Ls being reflected leftwardly 206558~

1 at a right angle by the polarization separation acting film 34. The P-polarized light Lp emerges from the exit surface of the third glass member 313. On the other hand, the S-polarized light Ls has its plane of polarization rotated by 90 by being transmitted through the half wavelength plate 36 and is converted into P-polarized light Lp , whereafter it is reflected upwardly at a right angle by the total reflectio~ film 35 and emerges from the exit surface of the second glass member 312 in the same direction as the direction of travel of the P-polarized light Lp. Accordingly, the unit 30a of the plate-like polarizing element of the present embodiment can convert the incident light P incident on the first glass member 311 into the P-polarized light Lp and the converted P-polarized light Lp without any loss and cause them to emerge from the whole exit surface.
Figure 8 is a construction view of the unit 30b of a plate-like polarizing element showing a fifth embodiment of the plate-like polarizing element of the present invention.
The difference of the unit 30b of the plate-like polarizing element of the present embodiment from the unit 30 of the plate-like polarizing element shown in Figure 6 is that the half wavelength plate 36 is adhesively secured to the exit surface of the third glass member 313 which is the optical path of transmitted 20~558~

1 light (P-polarized light Lp).
In the unit 30b of the plate-like polarizing element of the present embodiment, the incident light P is divided into P-polarized light Lp and S-polarized light LS by the P-polarized light Lp being transmitted through the polarization separation acting film 34 and the S-polarized light Ls being reflected leftwardly at a right angle by the polarization separation acting film 34. The P-polarized light Lp emerges from the exit surface of the third glass member 313, whereafter it is transmitted through the half wavelength plate 36 and thereby has its plane of polarization rotated by 90 and is converted into S-polarized light LS
and emerges. On the other hand, the S-polarized light Ls is reflected upwardly at a right angle by the total reflection film 35 and emerges from the exit surface of the second glass member 312 in the same direction as the direction of travel of the converted S-polarized light Ls . Accordingly, the unit 30b of the plate-like polarizing element of the present embodiment can convert the incident light P incident on the first glass member 311 into the S-polarized light Ls and the converted S-polarized light Ls without any loss and cause them to emerge from the whole exit surface.
In the present embodiment, polarization separa-tion acting film can be used in lieu of the total reflection film 35.

1 Again in the embodiments of Figures 6, 7 and 8, a single unit can be used as the polarizing element instead of a plurality of units being juxtaposed. In such case, a member for absorbing or reflecting the light travelling toward the second glass member 312 can be disposed on the entrance side of the second glass member 312, or light condensing means for directing the light travelling toward the second glass member 312 to the first glass member 311 can be disposed.
If this is done, the polarizing element, i.e., the unit 30, can be made to have substantially the same width as the width of the illuminating light beam, and there can be realized a polarizing element of about half the size of the conventional polarizing element shown in Figure 1 in each of the direction of the optical axis and a direction perpendicular to the optical axis.
Figure 9 is a perspective view showing a portion of a first embodiment of the polarizing conversion unit of the present invention.
The polarizing conversion unit 40 of the present embodiment comprises the plate-like polarizing element 41 shown in Figure 3, and a both-surface lenticular lens 42 which is provided on the incidence side of the plate-like polarizing element 41 and which is converting means for converting non-polarized light into non-polarized light of a lattice-like pattern.
The plate-like polarizing element 41 is disposed so 206S58~

1 as to be substantially orthogonal to the optical axis of non-polarized light of a lattice-like pattern emerging from the both-surface lenticular lens 42, and transmits the non-polarized light of a lattice-like pattern therethrough and converts it intosubstantially dense polarized-light. Also, as shown in Figure 10, on the incidence side surface of the both-surface lenticular lens 42 for incident lights Pl - P3 (non-polarized lights), convergence acting surfaces 431 ~ 433 comprising positive power lenses having the function of converging the incident lights Pl - P3 are provided at the same pitch as the units 201 - 203 of the plate-like polarizing element 41.
Also, on the emergence side surface of the both-surface lenticular lens 42 for the incident lights Pl - P3, divergence acting surfaces 441 ~ 443 comprising negative power lenses having the function of causing the converged incident lights Pl - P3 to diverge and become parallel lights are provided so as to be opposed to the first incidence side prisms 211 (see Figure 2) of the units 201 - 203. Further, non-acting surfaces 451 and 452 which are flat surfaces are provided between the divergence acting surfaces 441 ~ 443.
Accordingly, incident lights Pl - P3 incident on the entrance surface of the both-surface lenticular lens 42 perpendicularly thereto are converged by the convergence acting surfaces 431 ~ 433, whereby as shown 1 in Figure 10, they do not enter the non-acting surfaces 451 and 452 but enter only the divergence acting surfaces 441 ~ 443, whereafter they are made into parallel lights by the divergence acting surfaces 441 ~ 443 and emerge therefrom and therefore, the light emerging from the both-surface lenticular lens 42 becomes non-polarized light of a lattice-like pattern. This non-polarized light of a lattice-like pattern is converted into polarized light by the plate-like polarizing element 41, whereafter it emerges from the whole of the exit surfaces of the units 201 - 203. By making the absolute value of the focal length of the divergence acting surfaces 441 ~ 443 half the focal length of the convergence acting surfaces 431 ~ 433, the beam width of the non-polarized light of a lattice-like pattern emerging from the both-surface lenticular lens 42 can be made half the pitch of the convergence acting surfaces 431 ~ 433. Also, by providing absorbent film on the non-acting surfaces 451 and 452~ the adverse effect by irregular reflection or the like can be mitigated.
The polarizing conversion unit 40 of the present embodiment has the following advantages:
(1) Since the incident lights Pl - P3 are converted into non-polarized lights of a lattice-like pattern by the both-surface lenticular lens 42 and are caused to enter the units 201 - 203 of the plate-like 206558~

1 polarizing element 41, the sizes of the units 201 - 203 can be made small. Also, to make the sizes of the units 201 - 203 of the plate-like polarizing element 41 further smaller, the pitch of the convergence acting surfaces 431 ~ 433 of the both-surface lenticular lens 42 can be made small and the number of divisions of the lattice-like pattern can be increased.
(2) Even if the light source is one having a finite diameter, the incident lights Pl - P3 enter the first and second polarization separation acting films 241 and 242 of the units 201 - 203 of the plate-like polarizing element 41 without fail and therefore, the utilization efficiency of the light and the degree of polarization of the emergent light can be improved.
Particularly, the reflectance of the first and second polarization separation acting films 241 and 242 for S-polarized light can be relatively easily made 100%
and therefore, the degree of polarization of the emergent light can be kept high.

(3) The first, second and third incidence side prisms 211 - 213 and the first and second emergence side prisms 221 and 222 which are the constituents of the units 201 - 203 of the plate-like polarizing element 41 can be made identical in shape and size and therefore, in the process of manufacture, the kinds of parts can be decreased and low cost can be achieved.

Particularly, the kinds of the prisms which occupy 2065S8~

1 a great rate in terms of cost can be decreased and therefore, the effect of low cost is very great.
When the ease of molding and optical charac-teristics such as transmittance, etc. are taken into account, the both-surface lenticular lens 42 may be one provided by extrusion-molding or compression-molding an acryl plate. However, where the heat resisting property is particularly required, it is preferable to use one provided by compression-molding or polish-molding a glass member. Also, the both-surface lenticular lens 42 may be constructed by unitary molding, or may be constructed by cementing one-surface lenticular lenses together. Also, where the light source has a finite diameter, the ratio between the light beam presence area and the light beam absence area of the non-polarized light of a lattice-like pattern can be made 1:1 by making the absolute value of the focal length of the divergence acting surfaces 441 - 443 less than half the focal length of the convergence acting surfaces 431 ~ 433.
The polarizing conversion unit 40 of the present embodiment is constructed by the use of the plate-like polarizing element 41 shown in Figure 3 and the both-surface lenticular lens 42, but alternatively, it may be constructed by the use of a plate-like polarizing element comprising the units 20a, 30, 30a, 30b shown in Figures 5 - 8 and a both-surface lenticular 206s58~

1 lens.
A second embodiment of the polarizing conversion unit of the present invention will now be described.
The polarizing conversion unit of the present embodiment comprises the plate-like polarizing element 41a shown in Figure 4, and a both-surface fly-eye lens which is converting means for converting non-polarized light into non-polarized light of a two-dimensional lattice-like pattern provided on the entrance side Of the plate-like polarizing element 41a. In the polarizing conversion unit of the present embodiment, the incident light is vertically and horizontally divided by the both-surface fly-eye lens, whereafter it is caused to enter the first incidence side prism 211 Of each unit 201 - 205 of the plate-like polarizing element 41a. Again in the present embodiment, the polarizing conversion unit may be constructed by the use of a plate-like polarizing element comprising the units 20a, 30, 30a, 30b shown in Figures 5 - 8 and a both-surface fly-eye lens.
Figure 11 is a schematic construction view showing a first embodiment of the projector of the present invention.
The projector of the present embodiment differs from the projector shown in Figure 1 in that it uses the polarizing conversion unit 40 shown in Figure 9 as an illuminating optical system for converting the 1 parallel white light (non-polarized light) from a first condenser lens 64 into white rectilinearly polarized light. In the projector of the present embodiment, a second condenser lens 65 for condensing the white rectilinearly polarized light from the polarizing conversion unit 40 into the pupil of a projection lens 68 is provided between the polarizing conversion unit 40 and a liquid crystal light bulb 66.
Accordingly, the projector of the present embodiment illuminates the liquid crystal light bulb 66 by the use of the polarizing conversion unit 40 which is the polarizing conversion unit of the present invention and therefore, white light (non-polarized light) emitted from a light source 61 can be caused to enter the liquid crystal light bulb 66 without any loss and the distance from the light source 61 to the liquid crystal light bulb 66 can be made short and thus, the projector can be made compact.
Figure 12 is a schematic construction view showing a second embodiment of the projector of the present invention.
The projector of the present embodiment comprises a light source 71 emitting non-polarized light (white light), a reflecting mirror 72, a heat cut filter 73, a first condenser lens 74, an illuminating optical system for converting the non-polarized light from the light source into polarized light, an image generating 1 portion for generating an image by modulating the polarized light in conformity with a video signal, and a projecting optical system for projecting system is comprised of a color resolving system comprising a first resolving dichroic mirror 81, a second resolving dichroic mirror 82 and a resolving and reflecting mirror 83 for resolving the white light which is non-polarized light into red, green and blue non-polarized lights, respectively, polarizing conversion units 40R~ 40G
and 40B provided in the optical paths of the respective non-polarized lights and similar in construction to the polarizing conversion unit 40 shown in Figure 9, a condenser lens 75R for red, a condenser lens 75G
for green and a condenser lens 75B for blue. The image generating portion comprises a liquid crystal light bulb 76R for red, a liquid crystal light bulb 76G for green and a liquid crystal light bulb 76B for blue which are three generators for generating red, green and blue images, respectively. Further, the projecting optical system comprises a first combining dichroic mirror 84, a combining and reflecting mirror 85, a second combining dichroic mirror 86 and a projection lens 78.
In the projector of the present embodiment, red non-polarized light PR is reflected upwardly at a right angle by the first resolving dichroic mirror 81, blue non-polarized light PB of cyan non-polarized 1 light PG + PB transmitted through the first resolving dichroic mirror 81 is transmitted through the second resolving dichroic mirror 82 and green non-polarized light PG is reflected upwardly at a right angle by the second resolving dichroic mirror 82, whereby parallel white light PR + PG + PB emerging from the first condenser lens 74 which is non-polarized light is resolved into red, green and blue non-polarized lights PR, PG and PB. The red non-polarized light PR is reflected leftwardly at a right angle by the resolving and reflecting mirror 83, whereafter it enters the polarizing conversion unit 40R for red and is converted thereby into red polarized light. The green non-polarized light PG is reflected by the second resolving dichroic mirror 82, whereafter it enters the polarizing conversion unit 40G for green and is converted thereby into green polarized light. Further, the blue non-polarized light PB is transmitted through the second resolving dichroic mirror 82, whereafter it enters the polarizing conversion unit 40B for blue and is converted thereby into blue polarized light.
The red polarized light enters the liquid crystal light bulb 76R for red through the condenser lens 75R
for red, and has its plane of polarization rotated in conformity with the red component of a color video signal, whereby it is modulated and becomes a light beam including both of P-polarized light and S-polarized 206558~
_ 1 light, and is further converted into rectilinearly polarized red image light R by a polarizing plate 77R for red. Likewise, the green polarized light is converted into green image light G modulated by the action of the liquid crystal light bulb 76G for green and a polarizing plate 77G for green in conformity with the green component of the color video signal, and the blue polarized light is converted into blue image light B modulated by the action of the liquid crystal light bulb 76B for blue and a polarizing plate 77B for blue in conformity with the blue component of the color video signal.
The red image light R and the green image light G are combined by the first combining dichroic mirror 84 and converted into yellow image light R
+ G , whereafter it enters the second combining dichroic mirror 86. The blue image light B is reflected upwardly at a right angle by the combining and reflecting mirror 85, whereafter it enters the second combining dichroic mirror 86. The yellow image light R + G
is transmitted through the second combining dichroic mirror 86 and the blue image light B is reflected leftwardly at a right angle by the second combining dichroic mirror 86, whereby the yellow image light R + G and the blue image light B are combined and converted into white image light R + G + B modulated in conformity with the color video signal. The white 206558~

1 image light R + G + B is enlarged and projected onto a screen (not shown) by the projection lens 78 and thus, a color image is displayed on the screen.
The projector of the present embodiment has a polarizing conversion unit for each of red, green and blue non-polarized lights PR, PG and PB and thus, has the following effects:
(1) Since it is difficult to make the wavelength dependency of the quarter wavelength plate and polariza-tion separation acting film (see Figure 2) used ineach of the polarizing conversion unit 40R for red, the polarizing conversion unit 40G for green and the polarizing conversion unit 40B for blue zero, it can more improve to use red, green and blue non-polarized lights PR, PG and PB as the incident light than to use wide-band non-polarized light like parallel white light PR + PG + PB as the incident light.
(2) Generally, the light source 71 has a finite diameter and therefore, white light emitted from the light source 71 always has a finite angle of expanse.
If the beam diameter of light haviny a finite angle of expanse is compressed by some optical system, the angle of expanse will become greater in inverse propor-tion to the compression ratio of the beam diameter.
25 Accordingly, in the prior-art projector shown in Figure 1, the light condensing efficiency onto the liquid crystal light bulb 117 will be reduced by an increase 206558~

1 in the angle of expanse of light even if the beam diameter of light having a finite angle of expanse is compressed, because the distance between the polarizing conversion unit and the liquid crystal light bulb 117 is great. On the other hand, in the projector of the present embodiment, thin planar polarizing conversion units are used and therefore, these polarizing conversion units can be installed in proximity to the liquid crystal light bulbs and thus, the reduction in the light condensing efficiency onto the liquid crystal light bulb 117 by an increase in the angles of expanse of the red, green and blue non-polarized lights PR, PG and PB.

2065S8~

1 A third embodiment of the projector of the present invention will now be described.
The projector of the present embodiment differs from the projector shown in Figure 12 in that it has a polarizing conversion unit for cyan provided between the first resolving dichroic mirror 81 and the second resolving dichroic mirror 82 (i.e., in the common optical path of the green non-polarized light PG and the blue non-polarized lisht PB), in lieu of the polarizing conversion unit 40~ for green and the polarizing conversion unit 40B for blue.
Where a plurality of polarizing conversion units are used, it is better from the viewpoints of the utilization efficiency of the light emitted from the light source and the suppression of the occurrence of color irregularity to dispose the polarizing conversion units at optically equivalent positions (positions equivalent in the direction of travel, amplitude, etc. of the light) and therefore, it is desirable to construct the projector like that shown in Figure 12, but where preference is given to the curtailment of the number of parts, even if the projector is constructed like that of the present embodiment to thereby decrease the number of polarizing conversion units, the utilization efficiency of light can be more improved than in the prior-art projector and the entire apparatus can be made compact.

1 In the projector shown in Figure 12, as the polarizing conversion units 40R~ 40G and 40B for respective colors, use may be made of ones each comprising a combination of a plate-like polarizing element consisting of the unit 20a, 30, 30a, 30b shown in Figures 5 - 8 and a both-surface lenticular lens, or ones each comprising a combination of the plate-like polarizing element 41a ahown in Figure 4 and a both-surface fly-eye lens. The construction of the projector of the present invention is not restricted to the construction shown in Figure 12, but in a projector as described in Japanese Laid-Open Patent Application No. 62-S9919 wherein white light is resolved into respective color lights by the use of respective color filters and the respective color lights modulated by a liquid crystal light bulb are combined by a cube prism, the polarizing conversion unit 40 shown in Figure 9 may be disposed for each of the color filters. Also, in a projector as described in Japanese Laid-Open Patent Application No. 62-1391 wherein white light is resolved into respective color lights by a first cube prism and the color lights modulated by a reflection type liquid crystal light bulb are combined by a second cube prism, the polarizing conversion unit 40 shown in Figure 9 may be disposed on the exit surface of the first cube prism for each color light.

206SS8~
__ - 39 -l As described above, the present invention has the following effects.
The polarizing element of the present invention can be made small in the size thereof for the direction of travel of the incident light and a direction perpen-dicular to the direction of travel of the incident light. Also, the polarizing element of the present invention can be made compact and by juxtaposing a plurality of such elements, the size thereof for the direction of travel of the incident light can be made much smaller. The polarizing conversion unit of the present invention can cause the incident light to enter, without any loss, the plate-like polarizing element of the present invention having between units an area in which the incident light is intercepted when a plurality of polarizing elements are juxtaposed, and can convert the incident light into polarized light without any loss by the plate-like polarizing element and cause it to emerge therefrom and therefore, can improve the utilization efficiency of light. Further, the projector of the present invention can convert non-polarized light emitted from the light source into polarized light without any loss by the polarizing conversion unit and can therefore improve the utiliza-tion efficiency of light and can make the distancebetween the polarizing conversion unit and the image generator small, and this leads to the compactness of the entire apparatus.

Claims

1. A plate-like polarizing element for converting light into polarized light, having a plurality of units (20; 20a) arranged along a common plate substantially perpendicular to a direction of incident light (P1, P2), wherein each of said units (20; 20a) is provided with a dividing means for dividing said light (P1, P2) into reflected light (LS1, LS2) and transmitted light (Lp1, Lp2) whose planes of polarization are orthogonal to each other, varying means (231, 232; 26) for varying the polarized state of said reflected light (LS1, LS2) so as to make the plane of polarization thereof coincident with said transmitted light (Lp1, Lp2), and reflecting means (251, 252) for reflecting said reflected light (LS1, LS2) and directing it substantially in the same direction of travel of the transmitted light (Lp1, Lp2), characterized in that said dividing means comprises a pair of polarization separation acting surfaces (241, 242) arranged obliquely in the optical path of the incident light (P1, P2) so as to face each other with one end of one of them being in contact with one end of the other, and said varying means comprises a means (231, 232; 26) adapted to make the plane of polarization of said reflected light (LS1, LS2) coincident with said transmitted light (Lp1, Lp2) before said reflected light (LS1, LS2) reaches said polarization separation acting surfaces (241, 242).

2. A plate-like polarizing element according to Claim 1, wherein said varying means comprises a half-wavelength plate (26) arranged between said polarization separation acting surfaces (241, 242).

3. A plate-like polarizing element according to Claim 1, wherein said varying means comprises two quarter-wavelength plates (231, 232) each being arranged on one of said polarization separation acting surfaces (241, 242), so as to face each other.

4. A plate-like polarizing element according to Claim 1, 2 or 3, wherein said reflecting means comprises reflecting surfaces (251, 252) arranged substantially perpendicular to the adjacent one of said polarization separation acting surfaces (241, 242) with one end of said reflecting surfaces (251, 252) being in contact with said adjacent polarization separation acting surface (241, 242).

5. A polarizing conversion unit (40) comprising a plate-like polarizing element according to any one of the preceding Claims 1 to 4, and further comprising a converting means (42) provided at the light incidence side of said common plate for dividing said incident light (P1, P2, P3) into a plurality of partial lights, condensing each of said partial lights and converting it into light of a lattice-like pattern, each of said partial lights corresponding to one of said units (20; 20a).

6. A polarizing conversion unit (40) according to Claim 5, wherein said plate-like polarizing element is disposed substantially orthogonal to the optical axis of said light of lattice-like pattern emerging from said converting means (42), and transmits said light of lattice-like pattern therethrough and converts it into substantially dense polarized light.

7. A polarizing conversion unit (40) according to Claim 6, wherein said converting means (42) is a both-surface fly-eye lens.

8. A polarizing conversion unit (40) according to Claim 6, wherein said converting means (42) is a both-surface lenticular lens.

9. A projector comprising a polarizing conversion unit (40) according to any one of the preceding claims, further comprising an illuminating means (61-64; 71-74) for emitting light into said conversion unit, an image generator (65, 66, 67; 75, 76, 77) for modulating polarized light in conformity with a video signal to generate an image, and a projecting optical system (68; 78) for projecting said image.

10. A projector according to Claim 9, further comprising a color resolving system (81, 82) for resolving the light emitted by said illuminating means (61-64; 71-74) into red, blue, and green lights (PR, PG, PB), at least two of said plate-like polarizing elements provided in the common optical path of two of said lights of three colors and the remaining optical path, respectively, and three image generators (75, 76, 77) for modulating polarized red, blue, and green light in conformity with a video signal to generate red, blue, and green images (R*, G*, B*), respectively.

11. A plate-like polarizing element for converting light into polarized light, comprising:
a plurality of units arranged along a common plane across said light;
each of said units comprising:
dividing means for dividing said light into reflected light and transmitted light whose planes of polarization are orthogonal to each other, wherein said dividing means comprises a pair of polarization separation acting surfaces obliquely provided in the optical path of said light so as to face each other and disposed with one end of one of them being in contact with one end of the other;
varying means for varying the polarized state of at least one of said reflected light and said transmitted light to thereby make the planes of polarization of said two lights coincident with each other, wherein said varying means comprises a pair of quarter wavelength plates provided on said pair of polarization separation acting surfaces; and reflecting means for reflecting one of said reflected light and said transmitted light and directing it substantially in the same direction as the direction of travel of the other, wherein said reflecting means comprises a pair of reflecting surfaces disposed so as to interpose said pair of polarization separation acting surfaces therebetween and reflecting said reflected light from one of said pair of polarization separation acting surfaces through said pair of quarter wavelength plates and the other polarization separation acting surface.

12. A plate-like polarizing element for converting light into polarized light, comprising:
a plurality of units arranged along a common plane across said light;
each of said units comprising:
dividing means for dividing said light into reflected light and transmitted light whose planes of polarization are orthogonal to each other, wherein said dividing means is provided obliquely with respect to the optical path of said light;
reflecting means for reflecting one of said reflected light and said transmitted light and directing it substantially in the same direction as the direction of travel of the other wherein said reflecting means is disposed parallel to said dividing means; and varying means for varying the polarized state of at least one of said reflected light and said transmitted light to thereby make the planes of polarization of said two lights coincident with each other, wherein said varying means comprises a half wavelength plate and is disposed in the optical path of said reflected light between said dividing means and said reflecting means, and said half wavelength plate is provided with said common plane so as to be substantially perpendicular to said common plane such that one end of said half wavelength plate lies in contact with said dividing means and the other end of said half wavelength plate lies in contact with said reflecting means.

13. A polarizing conversion unit, comprising:
a plate-like polarizing element for converting light into polarized light, said plate-like polarizing element comprising a plurality of units arranged along a common plane across said light;
each of said units comprising:
dividing means for dividing said light into reflected light and transmitted light whose planes of polarization are orthogonal to each other, wherein said dividing means comprises a pair of polarization separation acting surfaces obliquely provided in the optical path of said light so as to face each other and disposed with one end of one of them being in contact with one end of the other;
varying means for varying the plane of polarization of at least one of said reflected light and said transmitted light to thereby make the planes of polarization of said two lights coincident with each other, wherein said varying means comprises a pair of quarter wavelength plates provided on said pair of polarization separation acting surfaces;
reflecting means for reflecting one of said reflected light and said transmitted light and directing it substantially in the same direction as the direction of travel as the other, wherein said reflecting means comprises a pair of reflecting surfaces disposed so as to interpose said pair of polarization separation acting surfaces therebetween and reflecting said reflected light from one of said pair of polarization separation acting surfaces through said pair of quarter wavelength plates and the other polarization separation acting surface; and converting means provided on the light incidence side of said plate-like polarizing element for dividing said light into a plurality of partial lights, condensing each of said partial lights and converting it into light of a lattice-like pattern, each of said partial lights of a lattice-like pattern corresponding to each of said units.

14. A polarizing conversion unit comprising:
a plate-like polarizing element for converting light into polarized light, said plate-like polarizing element comprising a plurality of units arranged along a common plane across said light;
each of said units comprising:
dividing means for dividing said light into reflected light and transmitted light whose planes of polarization are orthogonal to each other, wherein said dividing means is provided obliquely with respect to the optical path of said light;
reflecting means for reflecting one of said reflected light and said transmitted light and directing it substantially in the same direction as the direction of travel as the other, said reflecting means is disposed in parallel with said dividing means;
varying means for varying the plane of polarization of at least one of said reflected light and said transmitted light to thereby make the planes of polarization of said two lights coincident with each other, wherein said varying means comprises a half wavelength plate and is disposed in the optical path of said reflected light between said dividing means and said reflecting means, and said half wavelength plate is provided so as to be substantially perpendicular to said common plane such that one end of . . . . . . . . . . . .

said half wavelength plate lies in contact with said dividing means and the other end of said half wavelength plate lies in contact with said reflecting means.

15. A polarizing conversion unit according to Claim 13, wherein said plate-like polarizing element is disposed so as to be substantially orthogonal to the optical axis of said light of a lattice-like pattern emerging from said converting means, and transmits said light of a lattice-like pattern therethrough and converts it into substantially dense polarized light.

16. A polarizing conversion unit according to Claim 15, wherein said converting means is a both-surface fly-eye lens.

17. A polarizing conversion unit according to Claim 15, wherein said converting means is a both-surface lenticular lens.

18. A polarizing illuminating apparatus comprising:
illuminating means for emitting light;
a plate-like polarizing element for converting said light into polarized light, said plate-like polarizing element comprising a plurality of units arranged along a common plane across the light from said illuminating means;
each of said units comprising:
dividing means for dividing the light from said illuminating means into reflected light and transmitted light whose planes of polarization are orthogonal to each other, wherein said dividing means comprises a pair of polarization separation acting surfaces obliquely provided in the optical path from said illuminating means so as to face each other and disposed with one end of one of them being in contact with one end of the other;
varying means for varying the plane of polarization of at least one of said reflected light and said transmitted light to thereby make the planes of polarization of said two lights coincident with each other, wherein said varying means comprises a pair of quarter wavelength plates provided on the illuminating means sides of said pair of polarization separation acting surfaces;
reflecting means for reflecting one of said reflected light and said transmitted light and directing it substantially in the same direction as the direction of travel of the other, wherein said reflecting means comprises a pair of reflecting surfaces disposed so as to interpose said pair of polarization separation acting surfaces therebetween and reflecting said reflected light from one of said pair of polarization separation acting surfaces through said pair of quarter wavelength plates and the other polarization separation acting surface; and converting means provided on the light incidence side of said plate-like polarizing element for dividing said light into a plurality of partial lights, condensing each of said partial lights and converting it into light of a lattice-like pattern, each of said partial lights of a lattice-like pattern corresponds to each of said units.

19. A polarizing illuminating apparatus comprising:
illuminating means for emitting light;
a plate-like polarizing element for converting said light into polarized light, said plate-like polarizing element comprising a plurality of units arranged along a common plane across the light from said illuminating means;
each of said units comprising:
dividing means for dividing the light from said illuminating means into reflected light and transmitted light whose planes of polarization are orthogonal to each other, wherein said dividing means is provided obliquely with respect to the optical path from said illuminating means;

reflecting means for reflecting one of said reflected light and said transmitted light and directing it substantially in the same direction as the direction of travel of the other, wherein said reflecting means is disposed parallel to said dividing means;
varying means for varying the plane of polarization of at least one of said reflected light and said transmitted light to thereby make the planes of polarization of said two light coincident with each other, wherein said varying means comprises a half wavelength plate and is disposed in the optical path of said reflected light, wherein said half wavelength plate is disposed in the optical path between said dividing means and said reflecting means and said half wavelength plate is provided so as to be substantially perpendicular to said common plane such that one end of said half wavelength plate lies in contact with said dividing means and the other end of said half wavelength plate lies in contact with said reflecting means; and converting means provided on the light incidence side of said plate-like polarizing element for dividing said light into a plurality of partial lights, condensing each of said partial lights and converting it into light of a lattice-like pattern, each of said partial lights of a lattice-like pattern corresponds to each of said units.

20. A projector comprising:
illuminating means for emitting light;
a plate-like polarizing element for converting the light from said illuminating means into polarized light, said plate-like polarizing element comprising a plurality of units arranged along a common plane across the light from said illuminating means;
each of said units comprising:
dividing means for dividing the light from said illuminating means into reflected light and transmitted light whose planes of polarization are orthogonal to each other, wherein said dividing means comprises a pair of polarization separation acting surfaces obliquely provided in the optical path from said illuminating means so as to face each other and disposed with one end of one of them being in contact with one end of the other;
varying means for varying the plane of polarization of at least one of said reflected light and said transmitted light to thereby make the planes of polarization of said two lights coincident with each other, wherein said varying means comprises a pair of quarter wavelength plates provided on the illuminating means side of said pair of polarization separation acting surfaces;
reflecting means for reflecting one of said reflected light and said transmitted light and directing it substantially in the same direction as the direction of travel of the other, wherein said reflecting means comprises a pair of reflecting surfaces disposed so as to interpose said pair of polarization separation acting surfaces therebetween and reflecting said reflected light from one of said pair of polarization separation acting surfaces through said pair of quarter wavelength plates and the other polarization separation acting surface;
converting means provided on the light incidence side of said plate-like polarizing element for dividing said light into a plurality of partial lights, condensing each of said partial lights and converting it into light of a lattice-like pattern, each of said partial lights of a lattice-like pattern corresponding to each of said units;
an image generator for modulating said polarized light in conformity with a video signal to thereby generate an image; and a projecting optical system for projecting said image.

21. A projector comprising:
illuminating means for emitting light;

a plate-like polarizing element for converting the light from said illuminating means into polarized light, said plate-like polarizing element comprising a plurality of units arranged along a common plane across the light from said illuminating means;
each of said units comprising:
dividing means for dividing the light from said illuminating means into reflected light and transmitted light whose planes of polarization are orthogonal to each other, wherein said dividing means comprises a pair of polarization separation acting surfaces obliquely provided in the optical path from said illuminating means so as to face each other and disposed with one end of one of them being in contact with one end of the other;
varying means for varying the plane of polarization of at least one of said reflected light and said transmitted light to thereby make the planes of polarization of said two lights coincident with each other, wherein said varying means comprises a half wavelength plate installed between said pair of polarization separation acting surfaces;
reflecting means for reflecting one of said reflected light and said transmitted light and directing it substantially in the same direction as the direction of travel of the other, wherein said reflecting means comprises a pair of reflecting surfaces disposed so as to interpose said pair of polarization separation acting surfaces therebetween and reflecting said reflected light from one of said pair of polarization separation acting surfaces through said half wavelength plate and the other polarization separation acting surface;
converting means provided on the light incidence side of said plate-like polarizing element for dividing said light into a plurality of partial lights, condensing each of said partial lights and converting it into light of a lattice-like pattern, each of said partial lights of a lattice-like pattern corresponding to each of said units;

an image generator for modulating said polarized light in conformity with a video signal to thereby generate an image; and a projecting optical system for projecting said image.

22. A projector according to Claim 21, wherein said half wavelength plate is disposed intermediately of the optical path between said pair of polarization separation acting surfaces.

23. A projector comprising:
illuminating means for emitting light;
a plate-like polarizing element for converting the light from said illuminating means into polarized light, said plate-like polarizing element comprising a plurality of units arranged along a common plane across the light from said illuminating means;
each of said units comprising:
dividing means for dividing the light from said illuminating means into reflected light and transmitted light whose planes of polarization are orthogonal to each other, wherein said dividing means is provided obliquely with respect to the optical path from said illuminating means;
reflecting means for reflecting one of said reflected light and said transmitted light and directing it substantially in the same direction as the direction of travel of the other, wherein said reflecting means is disposed parallel to said dividing means;
varying means for varying the plane of polarization of at least one of said reflected light and said transmitted light to thereby make the planes of polarization of said two lights coincident with each other, wherein said varying means comprises a half wavelength plate and is disposed in the optical path of said reflected light between said dividing means and said reflecting means and said half wavelength plate is provided so as to be substantially perpendicular to said common plane such that one end of said half wavelength plate lies in contact with said dividing means and the other end of said half wavelength plate lies in contact with said reflecting means;
converting means provided on the light incidence side of said plate-like polarizing element for dividing said light into a plurality of partial lights, condensing each of said partial lights and converting it into light of a lattice-like pattern, each of said partial lights of a lattice-like pattern corresponding to each of said units;
an image generator for modulating said polarized light in conformity with a video signal to thereby generate an image; and a projecting optical system for projecting said image.

24. A projector according to Claim 20, wherein said plate-like polarizing element is disposed so as to be substantially orthogonal to the optical axis of said light of a lattice-like pattern emerging from said converting means, transmits said light of a lattice-like pattern therethrough and converts it into substantially dense polarized light.

25. A projector according to Claim 24, wherein said converting means is a both-surface fly-eye lens.

26. A projector according to Claim 24, wherein said converting means is a both-surface lenticular lens.

27. A projector provided with having:
illuminating means emitting light;
a color resolving system for resolving said light from said illuminating means into red, green and blue lights;

plate-like polarizing elements provided in the optical paths of said red, green and blue lights, respectively, for converting said lights into polarized lights, each of said plate-like polarizing elements comprising a plurality of units arranged along a common plane across the light from said illuminating means;
each of said units being provided with:
dividing means for dividing the light from said illuminating means into reflected light and transmitted light whose planes of polarization are orthogonal to each other;
varying means for varying the plane of polarization of at least one of said reflected light and said transmitted light to thereby make the planes of polarization of said two lights coincident with each other;
reflecting means for reflecting one of said reflected light and said transmitted light and directing it substantially in the same direction as the direction of travel of the other;
converting means provided on the light incidence side of each of said plate-like polarizing elements for dividing said light into a plurality of partial lights, condensing each of said partial lights and converting it into light of a lattice-like pattern, each of said lights of a lattice-like pattern corresponding to each of said units;
three image generators for modulating said red, green and blue polarized lights in conformity with a video signal to thereby generate red, green and blue images, respectively; and a projecting optical system for projecting said images.

28. A projector according to Claim 27, wherein said dividing means is a pair of polarization separation acting surfaces obliquely provided in the optical path from said illuminating means so as to face each other and disposed with one end of one of them being in contact with one end of the other, said varying means is a pair of quarter wavelength plates provided on the illuminating means side of said pair of polarization separation acting surfaces in parallelism to said pair of polarization separation acting surfaces, and said reflecting means is a pair of reflecting surfaces disposed so as to interpose said pair of polarization separation acting surfaces therebetween and reflecting said reflected light from one of said pair of polarization separation acting surfaces through said pair of quarter wavelength plates and the other polarization separation acting surface.

29. A projector according to Claim 27, wherein said dividing means is a pair of polarization separation acting surfaces obliquely provided in the optical path from said illuminating means so as to face each other and disposed with one end of one of them being in contact with one end of the other, said varying means is a half wavelength plate installed between said pair of polarization separation acting surfaces, and said reflecting means is a pair of reflecting surfaces disposed so as to interpose said pair of polarization separation acting surfaces therebetween and reflecting said reflected light from one of said pair of polarization separation acting surfaces through said half wavelength plate and the other polarization separation acting surface.

30. A projector according to Claim 29, wherein said half wavelength plate is disposed intermediately of the optical path between said pair of polarization separation acting surfaces.

31. A projector according to Claim 27, wherein said dividing means is provided obliquely with respect to the optical path from said illuminating means, said reflecting means is disposed parallel to said dividing means, and said varying means is a half wavelength plate and is disposed in the optical path of said reflected light.

32. A projector according to Claim 31, wherein said half wavelength plate is disposed in the optical path of said reflected light reflected by said reflecting means.

33. A projector according to Claim 31, wherein said half wavelength plate is disposed in the optical path between said dividing means and said reflecting means.

34. A projector according to Claim 27, wherein said dividing means is provided obliquely with respect to the optical path from said illuminating means, said reflecting means is disposed parallel to said dividing means, and said varying means is a half wavelength plate and is disposed in the optical path of said transmitted light.

35. A projector according to Claim 27, wherein said plate-like polarizing elements are disposed so as to be substantially orthogonal to the optical axis of said light of a lattice-like pattern emerging from said converting means, transmit said light of a lattice-like pattern therethrough and convert it into substantially dense polarized light.

36. A projector according to Claim 35, wherein said converting means is a both-surface fly-eye lens.

37. A projector according to Claim 35, wherein said converting means is a both-surface lenticular lens.

38. A projector provided with having:
illuminating means emitting light;

a color resolving system for resolving said light from said illuminating means into red, green and blue lights;
two plate-like polarizing elements provided in the common optical path of two of said lights of three colors and the other optical path, respectively, for converting said lights into polarized lights, each of said plate-like polarizing elements comprising a plurality of units arranged along a common plane across the light from said illuminating means;
each of said units being provided with:
dividing means for dividing the light from said illuminating means into reflected light and transmitted light whose planes of polarization are orthogonal to each other;
varying means for varying the plane of polarization of at least one of said reflected light and said transmitted light to thereby make the planes of polarization of said two lights coincident with each other;
reflecting means for reflecting one of said reflected light and said transmitted light and directing it substantially in the same direction as the direction of travel of the other;
converting means provided on the light incidence side of each of said plate-like polarizing elements for dividing said light into a plurality of partial lights, condensing each of said partial lights and converting it into light of a lattice-like pattern, each of said partial lights of a lattice-like pattern corresponding to each of said units;
three image generators for modulating said red, green and blue polarized lights in conformity with a video signal to thereby generate red, green and blue images, respectively; and a projecting optical system for projecting said images.

39. A polarizing element for converting light into polarized light, comprising:
a pair of polarization separation acting surfaces obliquely provided in the optical path of said light so as to face each other and disposed with one end of one of them being in contact with one end of the other, each of said polarization separation acting surfaces dividing said light into reflected light and transmitted light whose polarized states differ from each other;
a pair of quarter wavelength plates provided on said pair of polarization separation acting surfaces and making the polarized state of said reflected light coincident with the polarized state of said transmitted light; and a pair of reflecting surfaces disposed so as to interpose said pair of polarization separation acting surfaces therebetween and reflecting said reflected light from one of said pair of polarization separation acting surfaces through said pair of quarter wavelength plates and the other polarization separation acting surface and directing it substantially in the same direction as said transmitted light.

40. A polarizing illuminating apparatus comprising:
illuminating means emitting light a pair of polarization separation acting surfaces obliquely provided in the optical path of said light so as to face each other and disposed with one end of one of them being in contact with one end of the other, each of said polarization separation acting surfaces dividing said light into reflected light and transmitted light whose polarized states differ from each other;
a pair of quarter wavelength plates provided on said pair of polarization separation acting surfaces and making the polarized state of said reflected light coincident with the polarized state of said transmitted light; and a pair of reflecting surfaces disposed so as to interpose said pair of polarization separation acting surfaces therebetween and reflecting said reflected light from one of said pair of polarization separation acting surfaces through said pair of quarter wavelength plates and the other polarization separation acting surface and directing it substantially in the same direction as said transmitted light.

41. A projector comprising:
illuminating means emitting light;
a pair of polarization separation acting surfaces obliquely provided in the optical path of said light so as to face each other and disposed with one end of one of them being in contact with one end of the other, each of said polarization separation acting surfaces dividing said light into reflected light and transmitted light whose polarized states differ from each other;
a pair of quarter wavelength plates provided on said pair of polarization separation acting surfaces and making the polarized state of said reflected light coincident with the polarized state of said transmitted light;
a pair of reflecting surfaces disposed so as to interpose said pair of polarization separation acting surfaces therebetween and reflecting said reflected light from one of said pair of polarization separation acting surfaces through said pair of quarter wavelength plate and the other polarization separation acting surface and directing it substantially in the same direction as said transmitted light;
an image generator for modulating said reflected light and said transmitted light in conformity with a video signal to thereby generate an image; and a projecting optical system for projecting said image.

42. A polarizing conversion unit according to Claim 14, wherein said plate-like polarizing element is disposed so as to be substantially orthogonal to the optical axis of said light of a lattice-like pattern emerging from said converting means, transmits said light of a lattice-like pattern therethrough and converts it into substantially dense polarized light.

43. A polarizing conversion unit according to Claim 42, wherein said converting means is a both-surface fly-eye lens.

44. A polarizing conversion unit according to Claim 42, wherein said converting means is a both-surface lenticular lens.

45. A polarizing illuminating apparatus according to Claim 19, wherein said plate-like polarizing element is disposed so as to be substantially orthogonal to the optical axis of said light of a lattice-like pattern emerging from said converting means, transmits said light of a lattice-like pattern therethrough and converts it into substantially dense polarized light.

46. A polarizing illuminating apparatus according to Claim 45, wherein said converting means is a both-surface fly-eye lens.

47. A polarizing illuminating apparatus according to Claim 45, wherein said converting means is a both-surface lenticular lens.

48. A projector according to Claim 23, wherein said plate-like polarizing element is disposed so as to be substantially orthogonal to the optical axis of said light of a lattice-like pattern emerging from said converting means, transmits said light of a lattice-like pattern therethrough and converts it into substantially dense polarized light.

49. A projector according to Claim 48, wherein said converting means is a both-surface fly-eye lens.

50. A projector according to Claim 48, wherein said converting means is a both-surface lenticular lens.

51. A plate-like polarizing element for converting light into polarized light comprising:
a plurality of units arranged along a common plane across the light;
each of said units comprising:
dividing means for dividing the light into reflected light and transmitted light whose planes of polarization are orthogonal to each other, wherein said dividing means comprises a pair of polarization separation acting surfaces obliquely provided in the optical path so as to face each other and disposed with one end of one of them being in contact with one end of the other;
varying means for varying the plane of polarization of at least one of said reflected light and said transmitted light to thereby make the planes of polarization of said two lights coincident with each other, wherein said varying means comprises a half wavelength plate installed between said pair of polarization separation acting surfaces; and reflecting means for reflecting one of said reflected light and said transmitted light and directing it substantially in the same direction as the direction of travel of the other, wherein said reflecting means comprises a pair of reflecting surfaces disposed so as to interpose said pair of polarization separation acting surfaces therebetween and reflecting said reflected light from one of said pair of polarization separation acting surfaces through said half wavelength plate and the other polarization separation acting surface.

52. A polarizing conversion unit for converting light to polarized light comprising:
a plate-like polarizing element for converting the light into polarized light, said plate-like polarizing element comprising a plurality of units arranged along a common plane across the light;
each of said units comprising:
dividing means for dividing the light into reflected light and transmitted light whose planes of polarization are orthogonal to each other, wherein said dividing means comprises a pair of polarization separation acting surfaces obliquely provided in the optical path so as to face each other and disposed with one end of one of them being in contact with one end of the other;
varying means for varying the plane of polarization of at least one of said reflected light and said transmitted light to thereby make the planes of polarization of said two lights coincident with each other, wherein said varying means comprises a half wavelength plate installed between said pair of polarization separation acting surfaces;
reflecting means for reflecting one of said reflected light and said transmitted light and directing it substantially in the same direction as the direction of travel of the other, wherein said reflecting means comprises a pair of reflecting surfaces disposed so as to interpose said pair of polarization separation acting surfaces therebetween and reflecting said reflected light from one of said pair of polarization separation acting surfaces through said half wavelength plate and the other polarization separation acting surface; and converting means provided on the light incidence side of said plate-like polarizing element for dividing said light into a plurality of partial lights, condensing each of said partial lights and converting it into light of a lattice-like pattern, each of said partial lights of a lattice-like pattern corresponding to each of said units.

53. A polarizing unit according to Claim 52, wherein said plate-like polarizing element is disposed so as to be substantially orthogonal to the optical axis of said light of a lattice-like pattern emerging from said converting means, transmits said light of a lattice-like pattern therethrough and converts it into substantially dense polarized light.

54. A polarizing unit according to Claim 53, wherein said converting means is a both-surface fly-eye lens.

55. A polarizing unit according to Claim 53, wherein said converting means is a both-surface lenticular lens.

56. A polarizing illuminating apparatus comprising:
illuminating means for emitting light;
a plate-like polarizing element for converting the light from said illuminating means into polarized light, said plate-like polarizing element comprising a plurality of units arranged along a common plane across the light from said illuminating means;
each of said units comprising:
dividing means for dividing the light from said illuminating means into reflected light and transmitted light whose planes of polarization are orthogonal to each other, wherein said dividing means comprises a pair of polarization separation acting surfaces obliquely provided in the optical path from said illuminating means so as to face each other and disposed with one end of one of them being in contact with one end of the other;
varying means for varying the plane of polarization of at least one of said reflected light and said transmitted light to thereby make the planes of polarization of said two lights coincident with each other, wherein said varying means comprises a half wavelength plate installed between said pair of polarization separation acting surfaces;

reflecting means for reflecting one of said reflected light and said transmitted light and directing it substantially in the same direction as the direction of travel of the other, wherein said reflecting means comprises a pair of reflecting surfaces disposed so as to interpose said pair of polarization separation acting surfaces therebetween and reflecting said reflected light from one of said pair of polarization separation acting surfaces through said half wavelength plate and the other polarization separation acting surface; and converting means provided on the light incidence side of said plate-like polarizing element for dividing said light into a plurality of partial lights, condensing each of said partial lights and converting it into light of a lattice-like pattern, each of said partial lights of a lattice-like pattern corresponding to each of said units.

57. A polarizing illuminating apparatus according to Claim 56, wherein said plate-like polarizing element is disposed so as to be substantially orthogonal to the optical axis of said light of a lattice-like pattern emerging from said converting means, transmits said light of a lattice-like pattern therethrough and converts it into substantially dense polarized light.

58. A polarizing illuminating apparatus according to Claim 57, wherein said converting means is a both-surface fly-eye lens.

59. A polarizing illuminating apparatus according to Claim 57, wherein said converting means is a both-surface lenticular lens.

60. A projector according to Claim 21, wherein said plate-like polarizing element is disposed so as to be substantially orthogonal to the optical axis of said light of a lattice-like pattern emerging from said converting means, transmits said light of a lattice-like pattern therethrough and converts it into substantially dense polarized light.

61. A projector according to Claim 60, wherein said converting means is a both-surface fly-eye lens.

62. A projector according to Claim 60, wherein said converting means is a both-surface lenticular lens.