WO2008115011A1

WO2008115011A1 - Projector with laser lighting source

Info

Publication number: WO2008115011A1
Application number: PCT/KR2008/001564
Authority: WO
Inventors: Ka Hyun Hur; Jin Woo Bae
Original assignee: Iljindsp Co., Ltd.
Priority date: 2007-03-20
Filing date: 2008-03-20
Publication date: 2008-09-25
Also published as: KR20080085584A

Abstract

The present invention generally relates to a projector using a laser light source, and as a projector using a laser light source including at least one laser light source in the present invention, comprising: a focusing lens for focusing light radiated from the light source; a light modulator for converting the light radiated from the light source into an image; a beam shaper located between the focusing lens and the light modulator, and for converting light emitted from the focusing lens into a shape of an active area of the light modulator; condensing lenses located between the beam shaper and the light modulator, and for condensing light emitted from the beam shaper; and a projection lens for expansively projecting the image emitted by the light modulator.

Description

PROJECTOR WITH LASER LIGHTING SOURCE

Technical Field

[1] The present invention generally relates to a projector with laser lighting source, and more specifically, to a projector using a laser light source which has a lens structure for properly forming light radiated from the laser light source according to an active area shape of a light modulator. Background Art

[2] In order to commercialize a portable projector smaller than the palm size of the hand or a projector capable of being embedded in a notebook, a projector of small size with low power consumption should be developed. To miniaturize the size of the projector, a single -board type projector form should be applied as simplifying a structure of an optical system used therefor.

[3] In addition, an excellent light source for power consumption should be used to accomplish the projector with low power consumption. The most suitable light source for the projector with low power consumption contains a laser light source or an LED(Light Emitting Diode). The laser light source is known as an efficient light source which emits light of high brightness even with low power.

[4] However, a projector using the above light source should change a beam shape according to the shape of an active area of a light modulator before the light emitted from the light source is incident on the light modulator which converts the light into an image. An element performing the above function is called a 'beam shaper', and a prior beam shaper was used by passing uniform parts only, which were identical with the shape of the light modulator, as blocking other non-uniform parts after expanding the light source. Since the prior beam shaper blocks the other non-uniform parts, light efficiency may deteriorate, and it is hard to obtain uniform light. Disclosure of Invention

Technical Problem

[5] It is therefore an object of the present invention to provide a project with laser light source having a lens structure which uniformly forms light radiated from a low-power light source into an active area shape of a light modulator as minimizing light loss. Technical Solution

[6] In order to accomplish the above object, a projector using a laser light source including at least one laser light source, comprising: a focusing lens for focusing light radiated from the light source; a light modulator for converting the light radiated from the light source into an image; a beam shaper located between the focusing lens and the light modulator, and for converting light emitted from the focusing lens into a shape of an active area of the light modulator; condensing lenses located between the beam shaper and the light modulator, and for condensing light emitted from the beam shaper; and a projection lens for expansively projecting the image emitted by the light modulator.

Advantageous Effects

[7] In the past, when light irradiated from a light source was formed, relatively uniform partial light only of the diffused light was used while the rest of the light was blocked.

But, in the present invention, light irradiated from a light source is used by being expanded and condensed, thereby realizing good light efficiency. Also, a lot of lenses which are less than 2mm are used as beam shapers to easily form beams. [8] Particularly, the present invention has suggested a lens structure consisting of a beam shaper and a focusing lens suitable for a small-sized projector using a light source which consumes less than 50OmW power for one color.

Brief Description of the Drawings [9] The advantages of the invention wil become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings, in which: [10] Fig. 1 is a projector using a laser light source of one embodiment in accordance with the present invention; [11] Fig. 2 is a sectional view of a fly's eye lens as a representative example of a beam shaper; [12] Fig. 3 is a projector using a laser light source as one embodiment in accordance with the present invention; [13] Fig. 4 is a projector using laser light sources as one embodiment in accordance with the present invention; [14] Fig. 5 is a format diagram of a single-board type projector using laser light sources as one embodiment in accordance with the present invention; and [15] Fig. 6 is a format diagram of a single-board type projector using laser light sources as one embodiment in accordance with the present invention. [16] *** Reference List ***

[17] 10: light source 1OR: light source R

[18] 1OG: light source G 1OB: light source B

[19] 12: LED light source 20, 2OR, 2OG, 2OB: focusing lenses

[20] 30: beam shaper 50: oscillator

[21] 61,63: condensing lenses 70: light modulator

[22] 80: projection lens Mode for the Invention

[23] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown.

[24] Fig. 1 is a projector using a laser light source of one embodiment in accordance with the present invention. The projector using the laser light source comprises a light source(lθ), a focusing lens(20), a beam shaper(30), condensing lenses(61,63), a light modulator(70), and a projection lens(80).

[25] As a representative example of the light source(lθ) having low emission energy characteristics, there exists an LED (Light Emitting Diode) light source and a laser light source called as a laser diode. More specifically, 6 laser diodes in which one emission energy is 6OmW are used in combination type as a laser diode R, and for a laser diode B, 2 laser diodes in which one emission energy is 20OnW are used in combination type or 6 to 8 laser diodes in which one emission energy is 5OnW are used in combination type. The light sources which are less than the above size and emission energy should be equipped to be easily applied to a small-sized portable projector of roughtly mobile phone size.

[26] It is desirable that the light source(lθ) sequentially irradiates R/G/B lights.

Supposing the overall time for irradiating one frame is "T", the sequential irradiation of the R/G/B light source(lθ) means that the light source R is irradiated during T/3 time, the light source G is irradiated during successive T/3 time, and the light source B is irradiated during successive T/3 time after the irradiation time of the light source G.

[27] The focusing lens(20) focuses light radiated from the light source(lθ) on the beam shaper(30). Since light radiated to the light source(lθ) consisting of a laser diode is diffused in oval distorted shape, the focusing lens (20) performs a function of expanding the overal shape and a function of focusing the diffused/radiated light on an incident surface of the beam shaper. Thus, compared to a prior method of passing uniform parts only, which are identical with a shape of a light modulator, as blocking non-uniform parts after expanding light radiated from a light source, light efficiency gets better.

[28] If a laser light source is used as the light source(lθ), light emitted from the laser light source will have an oval shape in which a minor axis angle is about ±20 to ±30 while a major axis angle is about ±7 to ±10. And, if the laser light source is used for a display device, it is desirable to convert the oval shape radiated from the laser light source into a parallel light. In the present invention, it is possible to add a collimation lens between the light source(lθ) and the light modulator(70) for the above conversion.

[29] A beam shape of the light focused by the focusing lens (20) is transformed by the beam shaper(30). The reason for transforming the beam shape is to realize good light efficiency by forming an incident beam shape so that the incident beam shape is suitable for an incident surface shape of the light modulator(70). As a representative example of the beam shaper(30), there exists a fly's eye lens and a light pipe. Fig. 2 illustrates an example of the fly's eye lens having a type consisting of plural small-sized spheric or aspheric lens bodies on a substrate. Like shown in Fig. 2, the fly's eye lens is equipped with the plural small-sized lens bodies on a transparent substrate, and wherein it is desirable that a diameter(D) of a small-sized lens body is in the range of 50um to 20mm. In this case, the diameter of the small-sized lens body means the size of a diameter in a small-sized spheric lens body, while a diameter of a small-sized lens body consisting of a polygon such as a rectangular convex lens shape or a hexagonal convex lens shape means the length of the longest diagonal line among diagonal lines shown in the corresponding small-sized lens body. If the diameter of the above small- sized lens body is smaller than 50um, check-pattern types caused by coherence of laser are shown within a beam, and if the diameter is larger than 2mm, it is not available to obtain uniform light and to form a clear image from the light modulator. Consequently, the lens body cannot be used as a beam shaper.

[30] The small-sized lens body included in the fly's eye lens can be realized in various shapes. For instance, rectangular convex lens, hexagonal convex lens, and circular shapes can be possible, but desirably, it is recommended to form the lens body in the same shape as the shape of the light modulator(more exactly, a valid screen shape of the light modulator). For example, if the valid screen shape of the light modulator is a square shape, the shape of the small-sized lens body is set to the square shape, thereby minimizing light loss.

[31] In particular, it is shown that if various diameters of small-sized lens bodies are used in combination type without configuring the small-sized lens bodies in the same diameter, check-pattern types caused by coherence can be more effectively reduced. That is, it is shown that when the various diameters of the small-sized lens bodies are combined together, coherence can be effectively removed even though small-sized lens bodies whose diameters are out of the range of 50um to 2mm are included in less than 20%, approximately, on the basis of the size of the overall small-sized lens bodies.

[32]

[33] Though Fig. 1 illustrates that one sheet of the fly's eye lens(30) is used, it is desirable to use two sheets of fly's eye lenses(30) which are confronted together.

[34] The condensing lenses(61,63) are lenses for condensing the light formed by the beam shaper(30) into the light modulator(70), generally comprise two sheets of the lenses, and control a distance between the two lenses to exactly accomplish condensing property. [35] The light modulator(70) means an element which forms an image by selectively transmitting or blocking the incident light or changing a light path. A representative example of the light modulator(70) includes a DMD(Digital Micromirror Device), a liquid crystal display device, and an LCOS. The DMD is an element used for a DLP(Digital Light Processing) projector by using digital mirrors arrayed in matrix type as many as the number of pixels through a driving method employing a field sequential method. The DLP is a projector for realizing an image and gradation by reflecting light irradiated from a light source on a screen by controlling a light path with the use of a digital mirror. The liquid crystal display device is an element for forming an image by selectively turning on/off a liquid crystal. There is a direct vision type, a projection type, and a reflection type as a projector using the liquid crystal display device. The direct vision-type projector uses a method of directly observing an image generated when light emitted from a backlight behind the liquid crystal display device passes through a liquid crystal panel, and the projection-type projector uses a method of observing an image reflected on a screen by projecting the image on the screen after expanding the image generated as passing through the liquid crystal display device with the use of a projection lens. The reflection-type projector is in almost the same structure as the projection type, but it expansively projects reflected light on a screen by forming a reflection film on a lower substrate. The LCOS (Liquid Crystal on Silicon) is a sort of reflective-type liquid crystal display, being an optical element for operating a lower substrate of both-sided substrates of a prior liquid crystal display device, in reflective type by using a silicon substrate instead of employing transparent glass. A small square existing inside the light modulator(70) in Fig. 1 displays a valid screen area of the light modulator(70).

[36] The projection lens(80) is formed by using plural lenses, and expansively projects the image formed by the light modulator(70) on a screen (not shown).

[37]

[38] Fig. 3 is a projector using a laser light source as one embodiment in accordance with the present invention. The projector using the laser light source comprises a light source(lθ), a focusing lens(20), a beam shaper(30), an oscillator(50), condensing lenses(61,63), a light modulator(70), and a projection lens(80). The projector suggested in Fig. 3 has a difference from the projector of the embodiment of Fig. 1, from a point of view that the oscillator(50) is attached to the beam shaper(30). When laser passes through or is diffused in an optical system, phase patterns make special interference patterns called speckles. Since the interference patterns usually offset each other, noise or a speckled screen is generated as a consequence. So, it is impossible to clearly observe the speckled screen, and such a phenomenon is more deteriorated if 3 lasers such as R/G/B colors are used, resulting in damage to the screen to be displayed. In order to remove the above speckled screen, it is desirable to allow light radiated from the laser light source(lθ) to pass through a diffuser before the light reaches the light modulator(70). The same effect can be realized by oscillating the beam shaper(30) with the oscillator(50) instead of the diffuser.

[39] The diffuser is an optical element consisting of a diffusing element and a driving element which rotates or vibrates the diffusing element, and prevents interference between patterns caused by the laser light source by diffusing speckles with the use of the diffuser. If the diffusing element of the diffuser is quickly rotated or vibrated, it appears that the speckles are gone. Such a phenomenon comes from integration time of a human being's eyes for a moving object. So, if the eyes move more quickly than a time capable of sensing the speckles, the speckles are not shown to the human being's eyes.

[40]

[41] Fig. 4 is a projector using laser light sources as one embodiment in accordance with the present invention. The projector using the laser light sources comprises a light source R(IOR), a light source G(IOG), a light source B(IOB), focusing lenses(20R, 2OG, 20B), dichroic mirrors(40R, 4OG, 40B), a beam shaper(30), condensing lenses(61,63), a light modulator(70), and a projection lens(80). The projector suggested in Fig. 4 has a difference from the projector of the embodiment of Fig. 1, from a point of view that the light source R(IOR), the light source G(IOG), the light source B(IOB), the three sheets of the focusing lenses(20R, 2OG, 20B), and the three sheets of the dichroic mirrors(40R, 4OG, 40B) are used.

[42] After the three light sources(10R, 1OG, 10B) are focused by the respective focusing lenses(20R, 2OG, 20B), they are incident on the beam shaper(30) by being reflected or transmitted by the respective dichroic mirrors(40R, 4OG, 40B). The dichroic mirror (40R) reflects a red light irradiated from the light source R(IOR), and it is possible to use a general mirror which reflects all of visible ray areas instead of using the dichroic mirror (40R). The dichroic mirror (40G) reflects a green light irradiated from the light source G(IOG) as transmitting lights of the rest of wavelength areas, and the dichroic mirror (40B) transmits a blue light irradiated from the light source B(IOB) as reflecting lights of the rest of the wavelength areas. Light focused by the light modulator(30) is progressed in the same way as the projector of Fig. 1.

[43]

[44] Fig. 5 is a format diagram of a single-board type projector using laser light sources as one embodiment in accordance with the present invention. Since a configuration of the projector of Fig. 5 is similar to that of Fig. 4, different parts only from the embodiment of Fig. 4 will be described. It is illustrated that the projector of Fig. 5 employs 2 laser light sources(10R, 10G) as light sources and uses an LED(12) as a remaining blue light source. Though it is available to use an LED light source as a light source for any of R/G/B lights, it is desirable to use a relatively high-priced B light as the LED light source. After the two laser light sources (1OR, 10G) pass through the respective focus lenses(20R, 20G), they are incident on the beam shaper(30) by being reflected or transmitted by the respective dichroic mirrors(40R, 40G). The dichroic mirror(40R) reflects a red laser light irradiated from the laser light source(lOR), and it is available to use a general mirror which reflects all of visible ray areas instead of using the dichroic mirror(40R). The dichroic mirror(40G) transmits a green laser light irradiated from the laser light source(lOG), and reflects a light of a remaining wavelength area.

[45] A B light irradiated from the LED (12) is reflected by the dichroic mirror(40B). A certain type which transmits the R/G lights as reflecting the B light is used as the dichroic mirror(40B). A focusing lens(20B) for focusing the B light irradiated from the LED (12) on the dichroic mirror (40B) can be additionally equipped between the LED (12) and the dichroic mirror(40B). The B light reflected by the dichroic mirror(40B) is beam-shaped by the beam shaper(30), and is converted into an active area shape of the light modulator. Light focused by the light modulator(30) is progressed in the same way as the projector of Fig. 1.

[46]

[47] Fig. 6 is a format diagram of a single-board type projector using laser light sources as one embodiment in accordance with the present invention. Since a configuration of the projector of Fig. 6 is similar to that of Fig. 5, different parts from a configuration of the embodiment of Fig. 5 will be described. The projector of Fig. 6 is characterized that a B light comprised as an LED (12) and a dichroic mirror (40B) are located between condensing lenses(61,63). A certain type which transmits R/G lights as reflecting the B light is used as the dichroic mirror(40B). It is possible to further comprise a focusing lens(20B) for focusing the B light irradiated from the LED(12) on the dichroic mirror (40B) between the LED (12) and the dichroic mirror(40B).

[48]

[49] In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.

Claims

[I] A projector with laser light source including at least one laser light source, comprising: a focusing lens for focusing light radiated from the light source; a light modulator for converting the light radiated from the light source into an image; a beam shaper located between the focusing lens and the light modulator, and for converting light emitted from the focusing lens into a shape of an active area of the light modulator; condensing lenses located between the beam shaper and the light modulator, and for condensing light emitted from the beam shaper; and a projection lens for expansively projecting the image emitted by the light modulator. [2] The projector of claim 1, wherein the beam shaper consists of a fly's eye lens including plural small-sized lens bodies whose diameter is between 50um and

2mm. [3] The projector of claim 2, wherein the diameter of the small-sized lens bodies refers to a diameter in case of small-sized circular lens bodies, and is defined as the length of the longest diagonal line among diagonal lines shown in small-sized polygonal lens bodies in case of the small-sized polygonal lens bodies. [4] The projector of claim 1 or 2, wherein the light source sequentially irradiates three primary R/G/B colors. [5] The projector of claim 1, wherein the light source consists of a laser light source

R for irradiating an R light, a laser light source G for irradiating a G light, and a laser light source B for irradiating a B light. [6] The projector of claim 1, wherein at least one of the light sources which irradiate the R/G/B lights consists of an LED light source. [7] The projector of claim 5 or 6, wherein the focusing lens consists of three sheets for individually focusing the R/G/B light sources, and dichroic mirrors are equipped between the focusing lens and the light modulator. [8] The projector of claim 1 or 2, wherein the light modulator consists of a selected one of a liquid crystal display device, an LCoS, and a DMD. [9] The projector of claim 1 or 2, wherein an oscillator or a diffuser is further comprised. [10] The projector of claim 2, wherein the plural small-sized lens bodies are mixed with lens bodies of various sizes.

[I I] The projector of claim 1 or 2, wherein a shape of the small-sized lens bodies is the same as a valid screen shape of the light modulator.