WO2000034826A1

WO2000034826A1 - Rear-projection three-dimensional imaging system

Info

Publication number: WO2000034826A1
Application number: PCT/US1998/026664
Authority: WO
Inventors: Gerald R. Black; Wade R. Waterman; Rick J. Wright
Original assignee: Black Gerald R; Waterman Wade R; Wright Rick J
Priority date: 1998-12-08
Filing date: 1998-12-16
Publication date: 2000-06-15
Also published as: AU1999199A

Abstract

A system for providing simulated three-dimensional viewing from a conventional movie screen, television, or computer monitor which enables the viewer to select either two-dimensional or three-dimensional viewing. The system comprises a video projector (20), a prism (30), a pair of optical filters, a reflecting mirror (50), and a viewing screen (60). The prism separates projected light from the source into two separate images. A film of polarized material is placed proximate to the prism so that the two images are linearly polarized orthogonally to one another. The two images are then directed to a mirror that is preferably polarized and then directed to a video screen. A pair of glasses containing lenses having polarizers parallel to the polarizations of respective images are provided.

Description

REAR-PROJECTION THREE-DIMENSIONAL IMAGING SYSTEM

FIELD OF USE

The present invention relates to a system for transmitting a three-dimensional image onto a video screen, and more particularly, to convert a two-dimensional image to a three- dimensional image in a rear-projection video system.

BACKGROUND OF THE INVENTION

Two-dimensional displays are commonly used in television receivers, computer interfaces, instrumentation and visual display units.

Several factors are present in a two-dimensional display which provide the viewer with a perception of depth, such as shadow, size, perspective and the obscuring of far objects by close ones. However, a most important factor is missing: the difference between the views seen by the two eyes. The essential problem to be solved to produce a satisfactory, universal three-dimensional image display system is the production of two independent images to the eyes of a viewer, which are combined in the brain to produce depth perception.

While it is believed that in order to project true and natural three-dimensional images, two cameras and two projectors are required, simulated three-dimensional viewing provides a major advance from conventional two-dimensional viewing.

When simply produced, three-dimensional image display has a vast number of potential applications, such as home entertainment- theatre entertainment, and medical applications. What is needed is a system to convert a display system having the prerequisite imaging capability between a full resolution, two dimensional viewing mode and a three- dimensional viewing mode in a convenient and cost effective manner.

The added cost and complexity of true three-dimensional imaging in commercial video applications has led to the development of illusionary or pseudo-stereoscopic techniques and systems which manipulate a two-dimensional image to generate an illusion of three- dimension viewing. These systems represent a compromise between providing all of the necessary hardware and control required for true three-dimensional viewing, but require the viewer to synthesize three dimensions, when, in fact, only two-dimensional information is provided. Such systems generally split the two-dimensional image into two temporally offset versions of the image then, using glasses with special lenses, force each eye to see only one of the offset images, since human eyes are naturally horizontally displaced, horizontally displaced images are most effective.

With true three-dimensional perception, the separation of the eyes of the viewer introduces parallax into the observed scene. Part of the parallax contribution results in an offset of one image relative to the other such that an object at the center of the scene will be displaced to the right of the center for the left eye and to the left of the center for the right eye. Various degrees of horizontal offset will occur at various distances such that closer objects will be more offset than objects which are further away.

An artificial offset may be introduced in a two-dimensional image by simultaneously presenting an identical image in two slightly different horizontal positions to both eyes. Such a technique, causes the eyes to converge at a plane in space which is different from the true plane of projection, resulting in the perception of a three-dimensional image.

Electronic means are effective in modifying a two-dimensional image so as to achieve an illusion of three-dimension viewing, but such an "active" approach adds significantly to the sophistication of the image viewing apparatus. Although a scene need not be recorded in three-dimensional, the circuitry required to adjust horizontal and vertical dimensions and brightness, is nevertheless complex, and. although these functions may be performed external to the receiver, the greatest advantage is realized by performing such functions internal to the receiver, thus increasing the sophistication and cost of a consumer item.

Therefore, although such systems are available for creating three-dimensional images from a two-dimensional image, the circuitry involved may be beyond the means of a large class of consumers. If a less complex approach were available to derive geometrically offset versions of a two-dimensional image, it provides advantages of affordability and reliability. In rear-projection video, such a system that is fully compatibility with either a single projection lens or multiple projection lens color images.

What is needed is a system that will provide simulated three-dimensional viewing from a conventional real-projected movie screen, television, or computer monitor, a system that enables the viewer to select either two-dimensional or three-dimensional viewing; the three-dimensional viewing being visible across a wide range of viewer positions, and a system that is cost-effective, reliable, and easy to install.

SUMMARY OF THE INVENTION

The present invention provides a simple and reliable means for imparting three- dimensional images with a conventional rear-projection video image, the system being applicable to both single lens and multi-lens type systems. One preferred embodiment of the system comprises a video projector, a prism, a pair of optical filters, a reflecting mirror, and a viewing screen.

The video image is projected through a lens assembly, comprising a prism member and a film of polarized material. The image projected by the monitor through lens appears as a single two-dimensional image on surface. With this prism member disposed in the path of the projected image, two images are produced on the surface, these two images being horizontally displaced from one another, the projections. The prism separates the projected light source into two separate images, the two images having substantially uniform brightness.

A film-like material serves as a filter and. is positioned upon both sections of the prism. The film of polarized material is placed proximate to the wedge so that the two images is linearly polarized in accordance with the polarization of the film layer. The light which does not pass through prism member is polarized with a different layer of polarizing material so that this image is linearly polarized at right angles to the displaced other.

The prism members divide the projected video image into two versions of the image which are horizontally displaced from one another. A pair of optical filters, preferably linear polarizing filters having their axes of polarization at right angles to one another, are positioned with one in each path of the two projected images. A pair of glasses is worn by the viewer, the glasses including a matching set of filters, so that each eye sees only one of the horizontally displaced images. The system is not limited to the use of linear polarizing filters, as circular polarizers, oppositely colored filters, and any other type of light modifying device may be used so long as each eye sees substantially only one of the two displaced images. The filters are preferably layers of a polarizing material, and these filters and prism members are placed on a supporting frame which is operatively connected to a mechanical or electrical translation device, thus enabling a viewer to introduce and remove the three-dimensional effect.

Switching means enable the conversion of from two-dimensional viewing to three- dimensional viewing and back again. The switch is needed to create and filter the displaced images may be made operative or inoperative, thus enabling a viewer to watch either a simulated three-dimensional image using the glasses or a two-dimensional image without the glasses. In either case, both eyes see a continuous image, not time-shared as in the active raster-scan switching techniques previously described. The two images are then directed into a mirror that is preferably polarized and then projected through a video screen surface. The screen for providing is preferably polarized, the screen having substantially uniform brightness along the entire viewing surface. The screen comprises a Fresnel lens and a viewing screen. The Fresnel lens enhances center to edge brightness, thereby imparting uniformity of brightness across the surface of the screen. A laminated two-ply imaging screen is preferred. Both the lens and the viewing screen are preferably polarized.

hi the embodiment employing a prism member, a single wedge is preferably disposed horizontally across a portion of the projected beam. Alternatively, two wedges may be used, these being inserted either into diagonally opposite quadrants of the projected or partially covering top and bottom halves of the projected image. Such arrangements tend to more evenly distribute the light associated with the redirected beam, thus providing a set of displaced images exhibiting more uniform brightness. Alternatively, a filter, optically graded along a path extending radially outwardly from its central axis, may be inserted into the path of the projected image, thereby attenuating the light more toward its center and less around its periphery.

A pair of glasses are worn by each viewer to perceive three-dimension viewing. One lens of the glasses contains a linear polarizer with its axis of polarization parallel to that of one of the images, whereas the other lens of the glasses contains a polarizer with its axis of polarization parallel to that of the other image. As such, one eye sees only one of the images, while the other eye sees only the other.

For a more complete understanding of the optical system of the present invention, reference is made to the following detailed description and accompanying drawings in which the presently preferred embodiments of the invention are shown by way of example. As the invention may be embodied in many forms without departing from spirit of essential characteristics thereof, it is expressly understood that the drawings are for puφoses of illustration and description only, and are not intended as a definition of the limits of the invention. Throughout the description, like reference numbers refer to the same component throughout the several views.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE. 1 discloses a side view of the preferred embodiment of the rear-projection three-dimensional imaging system of the present invention as positioned within a rear- projection video system:

FIGURE 2 discloses a top view of another preferred embodiment of the rear-projection three-dimensional imaging system of the present invention, with the viewer positioned in front of the screen wearing the polarized glasses;

FIGURE 3 is an isometric view of the viewing glasses used in the rear- projection three- dimensional imaging system of the present invention, showing the oppositely angled polarization of the individual lenses;

FIGURE 4 discloses the combination of the cathode ray tube projections and the prism assemblies in another preferred embodiment of the rear-projection three-dimensional imaging of the present invention, the assemblies being used to split the image for three- dimensional viewing;

FIGURE 5 discloses another top view of one preferred embodiment of the rear-projection three-dimensional imaging system of the present invention, with the viewer positioned in front of the screen wearing the polarized glasses, detailing that the polarity of the individual lenses of the viewing glasses match the polarity of the individual sections of the prisms; FIGURE 6 discloses yet another top view of another preferred embodiment of the rear- projection three-dimensional imaging system of the present invention, showing the three cathode ray tubes, the prisms, the mirror and the images seen by the individual eyes of the viewer;

FIGURE 7 discloses yet another top view of the preferred embodiment of the rear- projection three-dimensional imaging system of FIGURE 6. but highlighting the light images reflected from the polarized viewing screen and the images seen by the individual eyes of the viewer;

FIGURE 8 discloses a preferred embodiment of the edges of the Fresnel lens and the viewing screen for use with the rear-projection three-dimensional imaging system of the present invention;

FIGURE 9 discloses another preferred embodiment of the Fresnel lens for use with the rear-projection three-dimensional imaging system of the present invention; and

FIGURE 10 discloses a preferred embodiment of the mirror for use the rear-projection three-dimensional imaging system of the present invention.

DETAILED DESCRIPTION OF THE PREFER-RED EMBODIMENT

Referring now to the drawing, FIGURE 1 discloses a first preferred embodiment of the rear-projection three-dimensional imaging system of the present invention. The system 10 comprises a projector 20, a lens assembly 25 comprising a prism member 30 and a pair of optical filters 40, a reflecting mirror 50, and a viewing screen 60.

The video image is projected through the lens assembly 25, comprising a prism member 30 and a pair of filters 40. The filters 40 comprise a film of polarized material. The image projected by the projector 20 through the lens assembly 25 appears as a single two- dimensional image on surface. In accordance with the present invention, however, the prism member 30 is disposed in the path of the projected image. This prism member 30 is constructed of a material substantially transparent to the projected image, such as optical glass or plastic. With this prism member 30 disposed in the path of the projected image, two images are produced on the surface, these two images being horizontally displaced from one another (see for example U.S. Patent 4,905,076 and U.S. Patent No. 5,594,843). The prism member 30 is positioned between the projector 20 and the viewing screen 60. The prism member 30 separates the projected light source into two separate images, the two images having substantially uniform brightness. The slope of the wedge portion 32 of the prism is preferably about between 1.4 and 5.2 degrees, depending upon the positioning of the viewing screen 60 and the mirror 50 relative to the prism members 30.

A film-like material 42 and 44 is disposed upon both sections of the prism 34 and 35. The film is preferably polarized material and is placed proximate to the wedge so that one of the two images is linearly polarized in accordance with the polarization of the film layer. The light which does not pass through prism section 34 passes through prism section 35, that is, the light forming projection and creating image, is polarized with a different layer of polarizing material so that this image is linearly polarized at right angles to the displaced other. Although the axes of polarization for the two images are vertical, horizontal, diagonal or any angle so long as the two axes are substantially normal to one another. The film is commercial available from Polaroid, and the specification is HN-35 sliced. The film is preferably secured to the prism by thermal bonding or clear adhesive material.

The two images are then directed into a mirror 50 as seen in FIGURE 6, The mirror 50 is preferably a projection grade glassless mirror, used in video rear projection systems being the optical equivalent or better than glass, while being functionally superior. The mirrors are commercially available from the Mirrorlite Company, with a type PGR or PGX designation. The panel comprises a rigid foam panel disposed within a frame aluminum extrusion. The panel is a tough, thin transparent plastic film coated with a reflecting material and tensioned on a rigid, stable support structure. The film is inert and always in tension, thereby distributing forces evenly throughout thereby forming a flat reflective surface (see FIGURE 10).

The viewing screen 60 is preferably polarized, the viewing screen 60 having substantially uniform brightness along its viewing surface. In the preferred embodiment, a Fresnel-type lenticular panel 62 is disposed behind the viewing screen 60 for purposes of uniform diffusion although other types of high quality lenticular panels may be used, hi one preferred embodiment, the rear-projection imaging system of the present invention 10 the viewing screen comprises two distinct optical elements: (a) a Fresnel lens 62; and (b) a screen panel 64. The Fresnel lens 62 as seen in FIGURE 9, enhances center to edge brightness, thereby imparting uniformity of brightness across the surface of the screen 60. A laminated two-ply imaging screen 64 is preferred. The first ply 65 is a diffusive material which contains suspended particles in a host material. The particles are preferably of a different refractive index than the host, and act as lensets. The Fresnel lens 62 enhances center to edge brightness and uniformity, and the Fresnel lens collimates incoming light and hot spots. Both the horizontal and vertical viewing angles can be adjusted and can be asymmetric. The Fresnel lens 62 and the viewing panel are preferably polarized, and are both commercially available from Fresnel Optics of Rochester, New York. Also, see for example U.S. Patent 5,069,813 (Patel) and U.S. Patent No. 5,614,941.

Referring now to FIGURE 7, the images are then projected through the screen surface for viewing. A pair of glasses are worn by each viewer to perceive three-dimension viewing from the projected images once the prism member and filters are introduced into the path the glasses 70 being shown in FIGURE 3. One lens 72 of the glasses contains a linear polarizer with its axis of polarization parallel to that of one of the images, whereas the other lens of the glasses contains a polarizer with its axis of polarization parallel to that of the other image. As such, one eye sees only one of the images, while the other eye sees only the other. In this way, three-dimension viewing is perceived by the viewer as the two images, horizontally displaced from one another, are mentally combined. As depicted in FIGURE 5, the left lens of the glasses 72 matches the non-displaced image and the right lens 74 matches the images seen by the two eyes may be reversed from that depicted in any of the figures contained herein, as it is only necessary that each eye sees only one of the two images.

To get good extinction of alternate fields in the right and left eyes of a viewer wearing suitably polarized glasses 70, the planes of polarization of alternate fields are preferably parallel and perpendicular to the plane of incidence of the mirror of the receiver. A variety of polarized glasses are commercially available from numerous sources, including Reel 3-D Enterprises. The glasses are already produced with the standard "V-position" polarization - the axis of the right viewing lens is 45 degrees to the right, while the axis of the left viewing lens is 45 degrees to the left. The projector polarizers must be adjusted to these angles.

Turning now to FIGURE 4, an array of prisms members 30 are shown that separate the adjacent image elements of the object plane to the right and left eyes, as shown. The lens assembly 25 separates elements such that the right eye sees element and the left eye sees element. Similarly, lens assembly separates elements such that element is seen by the left eye and element is seen by the right eye. Similar separation is performed by lens assembly on image elements. If an entire array of lens assemblies is placed in front of a two- dimensional object plane, the right and left eyes perceive two different perspective views of the two-dimensional image and the perception of depth.

Additionally, although the prism member 30 and polarizers 40 are shown as being disposed forwardly of projection lens 20, they may be located between the source of the projected image and the lens assembly or within the lens assembly itself, and in any order relative to one another so long as the two horizontally displaced images are produced upon a viewing surface. The prism members and polarizing filters are mounted to form a single physical unit so that these elements may be moved into the path of the projected image so as to create a three-dimensional effect, and out of the path so that a viewer may see a conventional two-dimensional picture. These elements can be positioned into and out of the optical path bath rotating means or sliding means, either manual or preferably automatically by the use of a switch in a remote controller.

The preferred embodiment includes a single prism member horizontally disposed across the projected beam. The right and left ends of the prism member need not extend past the outer perimeter of the beam. Additionally, although the wedges are shown with their thicker portions being leftward in the figure and sloping toward their thinner portions rightwardly, the direction of slope may be reversed wherein the thicker portions are toward the right. It is only necessary that the sloping be consistent relative to all the prism members used. Moreover, since it is only the degree of slope and not specific thicknesses which matter, one of the two wedges may be generally thicker or thinner so long as the slope of all the prism members is the same.

So long as the system of the present invention 10 creates two images which are horizontally displaced from one another, three-dimension viewing will be perceived from a two-dimensional image when the glasses 70 are worn. As such, the system 10 may generate a single horizontally displaced image and a non-displaced image, or it may generate two images which are horizontally displaced relative to the two-dimensional image, so long as the resulting two images are horizontally displaced from one another. The areas covered by the prism members 30 are linearly polarized in a first direction, whereas the remaining areas are linearly polarized along an axis which is normal to that associated with the prism members.

In conventional projection video systems, each image is formed on a tube with dimensions on the order of several inches. For example, tubes having a five inch diagonal are common. The image formed on this tube is subject to non-uniform brightness due to the requirement that such tubes incorporate a flat face plate upon which the image is formed. Additionally, the relatively large size of the image formed on each screen surface contributes to non-uniform light collection by the lens, which results in the most efficient collection being proximate to the center of the image. Intensity falls off rapidly near the edge of the tube and, most significantly near the corners. Assuming the intensity fall off follows an inverse square law on both sides of the lens, the non-uniformity of the resulting brightness increases non-linearly as the projection angle increases.

The need for convergence correction becomes more important when more than one light redirection device is used as is common in projection television systems utilizing a plurality of single-color beams. In the case of multiple projections, the image redirection device associated with each beam may preferably be designed independently of the other redirection devices to ensure convergence of the color with which each redirection device is associated. For example, if prism members are used as the image redirection devices, one or more geometrical properties of each prism member may be adjusted so that the final horizontally displaced images maintain optimal convergence. Among the geometrical properties of a prism member which may be adjusted are its angle of slope, thickness and cross sectional area.

With the lens assembly 25 covering the projection lens 20, each single-color projection lens 20 is covered by a prism member 30 which include the filters 40, thus creating three separate displaced and non-displaced projections which converge as two full-color displaced and non-displaced images on screen. The system 10 and components of the present invention are compatible with high-definition television and digital television since the sharper the original two-dimensional image, the better is the simulated three- dimensional image.

Throughout this application, various United States Patents are referenced by patent number and inventor. The disclosures of these Patents in their entireties are hereby incoφorated by reference into this specification in order to more fully describe the state of the art to which this invention pertains.

It is evident that many alternatives, modifications, and variations of the optical system of the present invention will be apparent to those skilled in the art in light of the disclosure herein. It is intended that the metes and bounds of the present invention be determined by the appended claims rather than by the language of the above specification, and that all such alternatives, modifications, and variations which form a conjointly cooperative equivalent are intended to be included within the spirit and scope of these claims.

Claims

1. A rear-projection video system enabling viewing in two dimensions in a first mode and viewing in three dimensions in a second mode, the system comprising:

(a) a screen for viewing the three dimensional viewing, the screen being polarized, the screen having substantially uniform brightness along a viewing surface;

(b) a transparent member positioned between a projector and a screen, the member separating the projected light source into two separate image, the two images having substantially uniform brightness;

(c) a pair of optical filters, the first optical filter being disposed between the first image and the screen, the second optical filter being disposed between the second optical filter and the screen; and

(d) viewing glasses having a pair of lenses, the lenses having a differing axes of polarity from each other.

2. A rear-projection video system enabling viewing in two dimensions in a first mode and viewing in three dimensions in a second mode, the system comprising:

(b) a transparent member positioned between a projector and a screen, the member separating the projected light source into two separate image, the two images having substantially uniform brightness; (c) a pair of optical filters, the first optical filter being disposed between the first image and the screen, the second optical filter being disposed between the second optical filter and the screen;

(d) a mirror positioned between the transparent member and the viewing screen, the mirror being polarized;

(e) viewing glasses having a pair of lenses, the lenses having a differing axes of polarity from each other.

3. A rear-projection video system enabling viewing in two dimensions in a first mode and viewing in three dimensions in a second mode, the system comprising:

(a) a screen member for viewing the three dimensional viewing, the screen member being polarized, the screen member having substantially uniform brightness along a viewing surface, the screen member including a Fresnel-type lens;

4. A rear-projection video system enabling viewing in two dimensions in a first mode and viewing in three dimensions in a second mode, the system comprising: (a) a screen for viewing the three dimensional viewing, the screen being polarized, the screen having substantially uniform brightness along a viewing surface;

(c) a pair of optical filters, the first optical filter being disposed between the first image and the screen, the second optical filter being disposed between the second optical filter and the screen, the first optical filter being polarized at an angle between 42 and 47 degrees, the second optical filter being polarized in an opposing direction that is substantially normal to the polarization angle of the first filter; and

(d) viewing glasses having a pair of lenses, the lenses having differing axes of polarity, the polarity of the first lens matching the polarity of the first filter, and the polarity of the second lens matching the polarity of the second filter.

5. A prism enabling the separation of a light source into two images, the prism comprising:

(a) the prism being transparent, the prism having an upper surface that is nonparallel with a lower surface, the prism having a first section and a second section, an upper surface of the prism in the first section forming an angle with a lower surface of the prism;

(b) a first film-like material disposed upon the first section of the prism, the first film material having a first polarity, a second film material disposed upon the second section of the prism, the second film material having a polarity that is substantially normal to the polarity of the first film material; whereby the film material is stretched and secured to the prism by a super-bonding material.

6. A prism enabling the separation of a light source into two images, the prism comprising:

(a) the prism being transparent, the prism having an upper surface that is nonparallel with a lower surface, the prism having a first section and a second section, an upper surface of the prism in the first section forming an angle with a lower surface of the prism in the range of between 1.4 and 5.2 degrees;

(b) a first film-like material disposed upon the first section of the prism, the first film material having a first polarity, a second film material disposed upon the second section of the prism, the second film material having a polarity that is substantially normal to the polarity of the first film material, the first film-like material being secured to the first section of the prism by bonding, the second film-like material being secured to the second section of the prism by bonding.

7. A video screen for use in a rear-projection video system enabling three-dimensional viewing, the three-dimensional viewing including an image separator that provides a first and second image, the image separator being polarized, the system requiring the use of viewing glasses to see the three-dimensional viewing, the viewing glasses being polarized, the video screen being polarized and having light diffusing means that provides uniform brightness across the surface of the screen.

8. A video screen for use in a rear-projection video system enabling three-dimensional viewing, the three-dimensional viewing including an image separator that provides a first and second image, the image separator being polarized, the system requiring the use of viewing glasses to see the three-dimensional viewing, the viewing glasses being polarized, the video screen being a unitary panel that includes light diffusing properties that provides uniform brightness across the surface of the screen, the video screen being a Fresnel-type lens.

9. A mirror for use in a rear-projection video system enabling three-dimensional viewing, the three-dimensional viewing including an image separator that provides a first and second image, the image separator being polarized, the system requiring the use of viewing glasses to see the three-dimensional viewing, the first and second image being reflected into a glassless mirror, the mirror having polarized surface, the mirror being inert and stretched to form a flat reflective surface.