KR20010040483A - Projection televisions with mirrors incident on holographic screens - Google Patents

Abstract

The projection television receiver 10 has a screen 22 having a three-dimensional hologram 26 on the film substrate to collect light over a range of incident angles and redirect the light further forward. Vertical / horizontal holograms have a variable gain over the viewing area of ± 40 °, and vertical viewing areas of ± 20 ° can be accumulated. The image projecting tubes 14,16,18 reflect the image along an optical path that projects the image onto at least one mirror 20 and converges on the screen at a throw angle [phi].

Description

[0001] PROJECTION TELEVISIONS WITH MIRRORS INCIDENT ON HOLOGRAPHIC SCREENS [0002]

Experiments performed at the vertical viewing angle with the maximum luminance show that the color shift is due to the white image formed at the center of the projection screen by the image projected from the red, green and blue projection tubes when viewing the horizontal plane at different angles Is defined as the degree to which the ratio of red / blue or green / blue is changed.

The problem of color movement arises because at least three image projectors are required for each different color image, e.g. red, blue and green images. The projection screen receives the image from the at least three projectors on the first side and displays the image on the second side with a controlled optical dispersion for all images being displayed. One projector among the projectors, generally at the center of the array of projectors, has a first optical path, typically a green projector, which tends to be nearly perpendicular to the screen. At least two projectors each having an optical path that converges to a first optical path from a direction in which each of the red and blue projectors located on the opposite side with respect to the green projector at the center on the arrangement is not vertical, Defines the angle of incidence. The color shift is because the red and blue projectors each have a non-perpendicular relationship to the screen and the green projector. Due to the color shift, the hue appears different at every position on the screen. A condition in which the above-mentioned difference in color tone is great is usually called a poor white uniformity. The smaller the color shift, the better the white uniformity.

Color shifts are expressed in numeric units, with smaller numbers indicating less color shift and better white uniformity. According to a conventional method, the values for the red, green and blue luminances are varied from 5 to 10 degrees from about -60 to about +60 degrees from various horizontal viewing angles, typically about -40 to +40 degrees, Respectively. The positive and negative angles respectively represent the horizontal viewing angle corresponding to the right and left of the center of the screen. These measurements are made at the maximum vertical viewing angle. The red, green and blue data are normalized to 0 at 0 °. The following equations (1) and (2), or both equations are calculated at each angle.

Where? Is an arbitrary angle in the range of the horizontal viewing angle, C (?) Is the color shift at the angle?, Red (?) Is the red luminance level at the angle? And green ([theta]) is the green luminance level at the angle [theta]. The maximum of these values is the color shift of the screen.

In general, the color shift should not be greater than 5, and nominally for the production of commercially acceptable screens. The limitations on the engineering side and the production side sometimes require somewhat larger color shifts than 5, but the performance of such color shifting is undesirable and usually results in lower-quality images with poor white uniformity Lt; / RTI >

Screens for projection television receivers are typically manufactured by an extrusion process using several types of rollers, which are used to determine the surface morphology of the thermoplastic sheet. This formation process corresponds to an arrangement of lenticular elements, commonly referred to as lenticules and color lenslets. The color shifting elements may be formed on one side of the same sheet, or on both sides, or may be formed only on one side of a different sheet, which may be permanently bonded as a stack, And can be installed adjacent to each other to function as a part. In many designs, the surface of one of the screen surfaces consists of a Fresnel lens that provides diffusion of light. Prior art attempts to reduce color shift and improve white uniformity have focused exclusively on the two aspects of the screen. One of them is the aspect and the arrangement of the lenticular element. Another aspect is to what extent the screen material or a portion thereof is doped with light diffusing particles that control the diffusion of light. The following patent specifications illustrate these efforts.

In U.S. Patent Nos. 4,432,010 and 4,536,056, a projection screen includes a light transmission lens-type thin plate having an incident surface and an exit surface. The incidence plane is characterized by a horizontally spreading lens shape, which corresponds to a ratio (Xv / R1) of the radius of curvature R1 of a portion close to the lenticulated depth Xv axis to a range of 0.5 to 1.8 do. This form extends along the optical axis to form a non-spherical input lens type lens.

Normally, a screen having a double-sided lens type lens is used. Such a screen has cylindrical entrance lenticular elements on the incident surface of the screen and has a cylindrical lens type lens element formed on the exit surface of the screen and a light absorbing layer formed on a portion of the exit surface on which light does not converge Lt; / RTI > The incident lens type lens element and the exit lens type lens element each have a circular, elliptical or hyperbolic shape expressed by the following equation (3).

Where C is the principal curvature and K is the conic constant.

Or the lenticular element has a curve to which a term of higher order than the second order is added.

In a screen using such a double-sided lens-type lens, the positional relationship between the incident lens and the exit lens, or between the lens-like elements forming the lenses, is specified. For example, U.S. Patent No. 4,443,814 discloses that an incident lens and an exit lens are arranged such that one lens surface comes to the focus of another lens. Japanese Patent No. 58-59436 discloses that the eccentricity of the incident lens is approximately the same as the reciprocal of the reflection index for the material constituting the lens-like lens. In U.S. Patent No. 4,502,755, two lens-type lens thin plates having a double-sided surface are combined so that the optical axis planes of the respective lens-like lenses are perpendicular to each other, and the incidence lens and the exit lens are asymmetric about the optical axis Thereby forming a lens-like lens having the double-sided surface. U.S. Patent No. 4,953,948 discloses that the position where the light converges only in the valley portion of the incident lens must be offset toward the viewing side from the surface of the exit lens so that the difference in tolerance and thickness for the misalignment of the optical axis may become larger, Can be made smaller.

In addition to the various methods for reducing color shift or white non-uniformity, methods for improving the performance of the projection screen are intended to brighten the image and ensure a reasonable viewing area in both horizontal and vertical directions. A summary of such a number of methods is disclosed in U.S. Patent No. 5,196,960, which is incorporated herein by reference in its entirety, including an incidence lens layer having an incidence lens and a lens surface in which the light of the incidence lens converges, Wherein the incident lens layer and the outgoing lens layer are each formed of a substantially transparent thermoplastic resin, and at least the outgoing lens layer is formed of a fine And there is a difference in the light diffusing particles between the incident lens layer and the emitting lens layer. The plurality of incident lenses is a cylindrical lens. The outgoing lens includes a plurality of outgoing lens layers, and each outgoing lens has a lens surface at a position where the light of each lens in the incident lens layer converges or at a position where the incident lens is located. The light absorption layer is also formed at a position where the light of the outgoing lens layer does not converge. The fabrication of such a screen is said to provide not only ease of fabrication by the extrusion process, but also reduced color shift, brighter images and a sufficiently horizontal viewing angle.

Over the years there have been considerable advances in the field of projection television production, but improvements have been minimal at best. Moreover, it failed to exceed any standards. Referred to herein as an angle a, is defined as an angle of incidence defined by the geometry of the image projector, generally greater than 0 ° and less than or equal to 10 ° or 11 °. The size of the image projector and / or its lens essentially makes it impossible to make the angle [alpha] close to 0 [deg.]. The best possible color movement performance in a range of angles? That is less than about 10 or 11 is about 5, as determined by Equations (1) and (2). The best color shifting performance achieved in a range of angles greater than about 10 or 11 is not commercially acceptable. In fact, a projection-type television set having an angle? Larger than 10 degrees or 11 degrees is not known.

A small angle? Results in severe and undesirable results. A very large cabinet depth is required to accommodate the projection television receiver. The reason for increasing the depth is that it is necessary to directly accommodate the light path with a small incidence angle alpha. For an image projector and an optical element of a given size, the angle of incidence can be reduced only by storing the optical path between the image projector or its lens and the screen. The technique of reducing the size of the projection television cabinet generally depends on a mirror that warps the longer optical path. Even if a mirror is used in the range of the possible incident angles, since there is a lower limit, the success of the color movement due to the above-mentioned efforts is also limited.

Polaroid Inc. is a member of DMP-128 Has been sold as a photo polymer, which can be made into a three-dimensional hologram using the method owned by Polaroid. The holographic manufacturing method is shown in part in U.S. Patent No. 5,576,853. Holographic photopolymers are commonly used to record photographic images by dividing coherent light into an illumination beam and a reference beam. The illumination beam illuminates an object. A beam reflected from the object and a reference beam passing through the object illuminate the photopolymer medium, which includes a deployable photothermographic photographic composition. The light waves of the two beams cause reinforcement and destructive interference, resulting in a sinusoidal peak locally exhibiting the photographic composition and a null standing wave pattern that does not reveal such a configuration locally. When the photographic medium was developed, a corresponding interference pattern was recorded in the medium. By irradiating the medium with a coherent reference beam, the image of the object is reproduced and can be seen in a range of apparent angles.

The interference pattern of the recorded hologram representing a specific photographic object is complicated because light from all the points irradiated on the object causes interference with the reference beam at all points on the hologram. By recording an image of a colorless " object ", a colorless hologram can be made, in which the interference pattern becomes more regular. In that case, the interference pattern will be in the form of a diffraction grating, but the spacing or resolution of the diffraction grating is very good when compared to the spacing of the projection screens provided with the lenticular elements of great size, To refract or refract light.

A three-dimensional holographic screen of a projection television is Polaroid's DMP-128 It is one of the many proposals made while trying to pioneer the market for photolithographic holographic products. The proposal is based on the benefits that Polaroid has expected in terms of greater luminance and resolution, smaller fabrication costs, lower weight and resistance to friction that is more likely to be received during the transport of the two-part screen. Polaroid has not limited any particular holographic arrangement for large holographic elements capable of configuring such a holographic projection television screen and has not even limited the use of any type of holographic or other type of holographic projection screen I did not even consider the problem.

Despite years of intensive development to provide a projection television with an overall color shift of less than 5 and even much smaller than 5 and a color shift of about 5 for an angle alpha greater than 10 or 11 degrees, No progress has been made in solving the problem of color shift, except that there is a slight change in the shape and position of the lens portion and diffuser in the screen. Furthermore, despite the fact that there is no relation with the color movement, there is no attempt to provide a projection type television equipped with a three-dimensional holographic screen, despite the proposal that three-dimensional holograms are useful for projection type screens. Can be installed in very small cabinets, and the long-standing need for a projection television receiver with significantly improved color movement performance remains unmet.

The projection type television set according to the configuration of the invention disclosed herein shows that the performance of the color movement is considerably improved, and the size of the color movement is in the range of 10 or 11, It is a value less than or equal to 2 that can be achieved. Also, the performance of the color movement is very good, and a commercially acceptable projection television receiver having an incidence angle of up to 30 degrees can be provided in a smaller cabinet. These elements are further increased in accordance with the present invention including one or more mirrors to extend the length of the optical path. The performance of the color movement with respect to the receiver having the large angle a as described above is superior to that of the conventional receiver having the color shift of 5 and a small angle a, 2 < / RTI >

These results are achieved by abandoning all of the techniques of the injection molded lens screen. Instead, the projection-type television set according to the configuration of the present invention may be a Mylar And a screen formed by a three-dimensional hologram formed on a substrate of a polyethylene film such as a polyimide film.

Such a three-dimensional holographic screen has been developed for its predicted advantages in terms of greater luminance and resolution, lower fabrication cost, lower weight and resistance to friction which is susceptible to two-part screen movement during movement. The discovery of the color shifting performance of the 3D holographic screen is the result of testing to determine if the optical properties of the 3D screen are at least as good as the conventional screen. The color transfer performance of the three-dimensional holographic screen is surprisingly low as measured by Equations (1) and (2). All of the obstacles that have limited the prior art improvements to the gradual steps have been removed. Also, smaller cabinets with a projection geometry featuring a larger incidence angle alpha can now be developed.

A projection television having unexpected properties associated with a 3D holographic screen according to the configuration of the invention disclosed herein includes at least three image projectors for each image of different colors; Comprising a projection screen formed by a three dimensional hologram on a substrate for receiving an image from a projector on a first side and displaying the image on a second side with controlled light diffusion for all images displayed, Wherein each image projector has a predetermined projection axis and the image projector is comprised of two adjacent image projectors having a projection convergence axis that defines an angle of incidence alpha and wherein the three dimensional hologram, The color shift of the screen is less than or equal to about 5 for all angles of incidence in a range greater than 0 degrees and less than or equal to about 30 degrees, Is obtained from at least one of the equations (1) and (2).

In the foregoing equations (1) and (2),? Is an arbitrary angle within the range of the horizontal viewing angle, C (?) Is the color shift at the? Angle, red (?) Is the red luminance level at the? blue ([theta]) is the blue luminance level at the angle [theta] and green ([theta]) is the green luminance level at the [theta] angle. The color shift of the screen can be expected to be less than 5, or for example less than or equal to about 4, 3 or even 2.

In terms of known disturbances at an incident angle of about 10 or 11, the color shift of the screen is less than about 2 for all angles of incidence corresponding to a first subrange of incidence angle greater than 0 and less than or equal to about 10 And the color shift of the screen is less than or equal to approximately 5 for all incident angles corresponding to a second dependent range of incident angles greater than approximately 10 and less than or equal to 30 degrees.

The screen also includes a light transmitting reinforcement made of an acrylic material in a layer having a thickness in the range of about 2 to 4 mm. The substrate includes a waterproof film that is highly durable and transparent, such as a polyethylene terephthalate resin film. The substrate may be a film having a thickness in the range of 1 to 10 mils. A thickness of about 7 mils is found in providing adequate support for the three-dimensional hologram. The thickness of the film is independent of performance. The thickness of the three-dimensional hologram is in the range of approximately 20 microns or less. According to a feature of the invention, the projection television may comprise at least one mirror along the optical path between the screen and the image projector. The image projectors individually or collectively project their respective images onto a mirror to reflect the images onto the first side of the screen and define a projection angle with respect to an axis perpendicular to each image. The projection screen collects and redirects the image reflected on the projection screen by a mirror such that the image displayed on the second side of the screen is directed at an angle of the display relative to an axis perpendicular to the screen, Deg.] To 5 [deg.]. The holographic screen collects incident light beyond the range of incident angles and emits light closer to a line orthogonal to the axis of the right angle.

According to another feature of the present invention, the color shifting operation of the projection screen can be further improved by spotting a plurality of holographic screen elements and / or collimating elements. For example, the holographic screen may be later placed by a vertical / horizontal linear Fresnel lens to obtain the desired deviation in optical transmission characteristics across the range of vertical or horizontal audiovisual. Alternatively, or in addition, a plurality of holographic screen elements having a variation ratio in optical transmission characteristics over a range of audiovisual can be stacked. According to a practical embodiment, at least two holographic elements are stacked, one providing a predetermined rate of variation over a vertical range, and the other providing a predetermined rate of variation over a horizontal range. In the method, the brightness of the image across the range of usable viewing angles is adjusted and optimized to use all available brightness. In addition, since the linearly varying device can be produced at a lower price than the circularly changing device, laminating the holographic device and / or the aiming device can accommodate various operating areas at an economical price. For example, a linearly varying Fresnel element may be embossed or roller extruded at a cost of 25% of the cost of the circular fresnel. Similarly, a linearly changing holographic master is less complex and less expensive than a circular one that defines the rate of change in two dimensions.

The present invention relates to the field of projection television receivers, and more particularly to a receiver having a projection source oriented in at least one mirror direction for directing light to the back of the holographic screen. The holographic screen collects light over a range of incident angles and redirects the collected light more horizontally to an axis orthogonal to the screen. Holographic screens combined with one or more mirrors enable significantly reduced color shift, improved brightness, and significantly reduced cabinet depth.

There is shown a diagram according to one preferred embodiment of the present invention. It is to be understood that the invention is not to be limited to the disclosed embodiments, but is capable of modifications and variations within the spirit and scope of the appended claims. In the drawings,

1 is a schematic diagram of a projection television according to the configuration of the invention disclosed herein;

2 is a simplified illustration of a projection television structure useful for illustrating the configuration of the present invention;

3 is a side elevational view of a projection screen reinforced in accordance with the configuration of the present invention;

4 schematically shows an optional embodiment of a projection screen with two additional holograms with gain variation for each of the viewing angles, horizontal and vertical.

FIG. 5 is a graph showing the ratio of the maximum white luminance as a horizontal viewing angle using a horizontal-change type holographic element with and without stacked vertical-changing holographic elements.

6 is a schematic illustration of an alternative embodiment with a holographic and collimating screen layer of a laminate.

Fig. 7 is another drawing that simplifies the projection television structure useful for explaining the configuration of the present invention; Fig.

8 is a graph showing the luminance measured over a vertical viewing range of ± 20 ° with respect to the projection angle φ _v at a point in the center of the screen on vertical planes of 10 °, 20 ° and 30 °, as a percentage of maximum white luminance.

Fig. 9 is another drawing that simplifies the projection television structure useful for explaining the configuration of the present invention; Fig.

10 is a graph showing the red / green and red / blue color shifts measured over a horizontal viewing range of +/- 40 degrees with respect to the projection angle of phi _h in a horizontal plane of 0 DEG.

Figure 11 is a graph showing the luminance of the screen, measured over a horizontal viewing range of ± 40 ° to the projection angle φ from point _h in the center of the screen on the horizontal plane of the 0 °, as a percentage of the maximum white luminance.

Figure 12 is a graph showing the red / green and red / blue color shifts measured over a horizontal viewing range of +/- 40 degrees with respect to the projection angle of phi _h in a horizontal plane of 15 degrees.

13 is a graph showing the brightness of the screen measured as a percentage of the maximum white luminance over a horizontal viewing range of +/- 40 DEG with respect to the projection angle phi _h at a point in the center of the screen on a horizontal plane of 15 DEG.

14 is a graph showing the red / green and red / blue color shifts measured over a horizontal viewing range of +/- 40 degrees with respect to the projection angle of phi _h in a horizontal plane of 30 degrees.

15 is a graph showing the brightness of the screen measured as a percentage of the maximum white luminance over a horizontal viewing range of +/- 40 DEG with respect to the projection angle phi _h at a point in the center of the screen on a horizontal plane of 30 DEG.

Figure 16 is a graph showing the red / green and red / blue color shifts measured over a horizontal viewing range of +/- 40 degrees with respect to the projection angle of phi _h in a horizontal plane of 45 degrees.

17 is a graph showing the brightness of the screen measured as a percentage of the maximum white luminance over a horizontal viewing range of +/- 40 DEG with respect to the projection angle phi _h at a point in the center of the screen on a 45 DEG horizontal plane.

FIG. 18 is another diagram that simplifies a projection television structure useful for explaining the configuration of the present invention; FIG.

1 schematically shows a projection television receiver 10. The set of projection cathode ray tubes 14, 16, 18 provides images of red, green and blue, respectively. Each of the lenses 15, 17, and 19 is provided in the cathode ray tube. The projected image is reflected by the mirror (20) onto the projection screen (22). Additional mirrors may be used depending on the structure of the particular optical path. The green cathode ray tube 16 projects an image of green along the optical path 32, which in this example is in its normal direction to the screen 22. That is, the center line of the optical path is perpendicular to the screen. The red and blue cathode ray tubes have respective optical paths 34 and 36 which converge toward the first optical path 32 in a direction other than a right angle and define an incident angle alpha. Such an angle of incidence causes a problem of color shift.

The screen 22 includes a three dimensional hologram 26 disposed on a substrate 24. The hologram 26 is a print for a master hologram that mainly forms a diffraction pattern that adjusts the distribution of light energy coming from the three projectors 14,16,18, / RTI > and / or < / RTI > height. In a preferred embodiment, the hologram is a " central focused " hologram that tends to direct the incident light back onto the hologram from a range of angles of incidence to make the light more straight forward. The screen receives an image from the projector on a first incident surface 28 and displays the image on a second exit surface 30 through controlled light diffusion of all images being displayed. The substrate is preferably a waterproof film that is highly durable and transparent, such as a polyethylene terephthalate resin film. Such films include Mylar Available from EI Du Pont de Nemours & Co. under the trademark < RTI ID = 0.0 > EI du Pont de Nemours & Co. < / RTI > The thickness of the film plate is in the range of 1 to 10 mils, which is approximately 0.001 to 0.01 inches, or 25.4 to 254 microns. It has been known that a film having a thickness of about 7 mils is provided as a suitable support for a three dimensional hologram disposed thereon. The thickness of the film generally does not affect the performance or color transfer performance of the screen, and films of different thicknesses can be used. The thickness of the three-dimensional hologram 26 is approximately 20 microns or less.

A three dimensional holographic screen is available from at least two sources. Polaroid uses its proprietary wet chemical process to form a three-dimensional hologram on its DMP-128 photopolymerizable material. The process includes forming a scattering holographic pattern on the photopolymerizable material, which may include a change in screen gain over a range of horizontal and / or vertical viewing angles. The master hologram can be fabricated by exposing a photomultiplied holographic media to interference light, which includes a beam reflected from a reference beam and a pattern on the plane, and the pattern on the plane corresponds to the desired gain variation, .

A preferred embodiment of a three-dimensional holographic screen used in a projection television receiver described and claimed herein was constructed by a wet chemical process of Polaroid Inc. according to the following experiment.

Horizontal Half Viewing Angle: 38 ° ± 3 °,

Vertical half viewing angle: 10 ° ± 1 °,

Screen gain: ≥8,

Color shift: ≤3,

Here, the horizontal and vertical viewing angles are measured in a conventional manner, and the gain of the screen is measured perpendicular to the screen, and the luminous intensity from the light source toward the back side of the viewing side and the luminance toward the viewer from the front side of the viewing side And the color shift is measured as described above. Summary As described in one section, the considerable color movement performance of a 3D holographic projection screen is completely unpredictable.

Figure 2 is a simplified projection television illustrating the performance of color shifting and omitting mirrors and lenses. The optical axes 34 and 36 of the red and blue cathode ray tubes 14 and 18 are symmetrically arranged at an incident angle of? With respect to the optical axis of the green cathode ray tube 16. [ The minimum depth D of the cabinet is determined by the distance between the screen 22 and the rear edge of the cathode ray tube. It will be appreciated that the smaller the angle of incidence α, the closer the cathode ray tubes are to each other and / or the cathode ray tubes must be further away from the screen in order to provide a clearance for these cathode ray tubes. These obstacles can not be avoided at sufficiently small angles α. This undesirably increases the minimum depth D of the cabinet. Conversely, the larger the angle?, The closer the cathode ray tubes are to the screen 22, thereby reducing the minimum depth D of the cabinet.

On the viewing screen of the screen 22, two horizontal half viewing angles -β and + β are displayed. At the same time, the total horizontal viewing angle 2? Is determined. The half-view angle is typically in the range of +/- 40 degrees to +/- 60 degrees. The plurality of specific viewing angles [theta] are within each half angle, and the color movement at that angle [theta] can be measured and determined according to Equations 1 and 2 described above.

Looking at the faces of the known obstacles at an incident angle of approximately 10 or 11, the color shift of the three-dimensional holographic screen is approximately equal to or less than 2, which means that for an incident angle greater than 0 DEG and less than or equal to about 10 DEG Wherein the color shift of the screen is less than or equal to about 5, which is greater than or equal to about 10 and less than or equal to about 30, in a second subrange for an incident angle less than or equal to 30 It applies to all angles of incidence. A color shift less than or equal to about 2, such as in the first subrange, can be achieved in a second subrange of greater incidence.

With reference to Figure 3, the substrate 24 comprises the above- And the like. The photopolymerizable material is supported on the film layer 24, and a three-dimensional hologram 26 is formed from the photopolymerizable material. As a suitable photopolymerizable material, DMP-128 .

For example, the screen 22 may further include a light transmission stiffener 38 made of an acrylic material such as polymethylmethacrylate (PMMA). Polycarbonate materials may also be used. The stiffener 38 is currently a layer having a thickness in the range of about 2 to 4 mm. The screen 22 and the stiffener 38 are attached to each other through the mutual boundary 40 between the holographic layer 26 and the stiffener 38. Adhesive radiation and / or thermal bonding techniques may be used. The surface 42 of the reinforcing layer can be treated by at least one of a dyeing and anti-glare coating and an anti-scratch coating.

Different optical lenses or a lenticular configuration are provided on the various surfaces of the screen and / or the layers constituting the screen, which is advantageous over conventional projection screens, without compromising the improved color transfer performance of the three-dimensional holographic projection screen Control the aspect of the projection screen that affects the performance characteristics other than the color movement performance as is known for the < Desc / Clms Page number 3 > Figure 4 shows such a first variant, in which at least two holograms are superimposed or stacked. As shown in this embodiment, the first hologram having the horizontal gain variation over the viewing area of ± 40 ° overlaps with the second hologram having the vertical gain variation over the area of ± 20 °. The gain variation appears shaded in the figure, but when not illuminated, the actual holographic components appear to diffuse over their surface. The result of overlapping the horizontal and vertical gain changing holograms is nearly identical to the centralized hologram, but the brightness level changes at different rates over the horizontal and vertical sections because the horizontal section is substantially larger than the vertical section.

FIG. 5 is a graph showing the screen luminance measured over a horizontal viewing interval of ± 40 ° at the center of the screen as a percentage of the maximum white luminance. The two lines on the graph show the brightness when using only the horizontally varying hologram and the brightness when using the horizontally and vertically varying holograms overlapping. The change in the horizontal luminance with the overlapping hologram is almost equal to or slightly improved from that of the horizontal hologram alone.

In making holographic screens for various performance ranges, it is difficult to create screens that simultaneously achieve the desired performance characteristics. The overlapping step allows for individual adjustment of different requirements, such as vertical and horizontal changes in the gain plane and the aspect ratio of the screen (width rather than height). This configuration is not limited to two overlapping holograms, but is applied, for example, to additional overlapping holograms that control other features of optical transmission through the screen.

Figure 6 shows that a centralized hologram with horizontal and vertical gain changes overlaps the linear Fresnel 29, 31 resulting in horizontal and rotated vertical aiming. This embodiment has an excellent cost relationship because the linear Fresnel can be embossed at low cost compared to the circular Fresnel or the roller can protrude. The circular Fresnel can be considered to represent 60% of the conventional screen cost. The linear Fresnel costs 25% of the cost of the original Fresnel. Therefore, a 30% cost reduction is possible (ie 25% + 25%) * 60% = 30%}. In the case of the above-described horizontal and rotational holograms, the linear Fresnel can be changed as needed over horizontal and / or vertical viewing intervals, for example, changing the focal length regardless of the vertical and horizontal sections. The two superimposed linear Fresnel can be placed at any position after the holographic component.

Another feature of the present invention is the ability to fabricate a rear projection television in which the thickness of the cabinet is sufficiently reduced. In particular, the rear projection television of the present invention may include a plurality of image projectors, none of which has a projection axis coincident with the vertical axis of the screen. Rather, in view of the present invention, there is provided a rear projection television in which each image projector in the television is provided with a projection axis for determining a projection angle [phi] over the vertical axis of the screen. Since the television of the present invention can correct the projection angle [phi] by up to 30 degrees, the image displayed on the screen will be adjusted to the angle of the display with respect to the vertical axis of the screen, and the angle of the display is in the range of 0 [deg.] To 5 [ It is.

For example, the television arrangement of the present invention facilitates sufficiently reducing the depth of the required cabinet because it can accommodate a projection angle that includes a maximum upper angle. Figure 7 contains the projected image on the mirror 20 by the screen 22 and the γ _v angle as that by the projection type cathode ray tube (14, 16, 18), towards on the vertical plane up to top angle φ _v in the vertical plane And reflects the light onto the projection screen 22 at an angle to the projection screen 22. The screen 22 is adjusted to a display angle &thetas; _v between 0 DEG and 5 DEG, preferably between 3 DEG and 5 DEG, on the vertical plane, such that the image transmitted through the screen is readjusted, Is reflected onto the screen 22 at a projection angle that includes a maximum upper angle φ _v of 10 ° to 30 °, preferably 15 ° to 30 °, most preferably at least 15 °.

This configuration of the present invention is tested for three different projection angles φ _v , 10 °, 20 ° and 30 °. In particular, the light is reflected on the back side of the screen 22 at a given projection angle? _V while the measurements are made on the intensity of the light transmitted through the screen 22 at different viewing angles. The results of these tests are shown in the form of graphs in FIG. 8 is a graph showing the luminance measured for a vertical viewing range of ± 20 ° at the center position of the screen as a percentage of the maximum white luminance.

Another feature of the present invention is the ability to use the mirror 20 to easily manipulate the projection angle, including the maximum lateral approach angle. Figure 9 shows a mirror 20 directed at an angle of the screen 22 and γ _{h on} a horizontal plane where the image projected by the projection cathode ray tube 16 onto the mirror 20 is projected at a maximum lateral approach angle and is reflected onto the projection screen 22 at a projection angle including? _h . The screen 22 is adjusted to a display angle &thetas; _h between 0 DEG and 5 DEG, preferably between 3 DEG and 5 DEG, such that the image transmitted through the screen 22 is readjusted Is reflected onto the screen 22 at a projection angle that includes a maximum lateral angle of approach? _H of 10 to 30, preferably 15 to 30, most preferably at least 15.

This aspect of the invention is carried out the test for the four angles of each other up to the side approach angle φ _h i.e., 0 °, 15 °, 30 °, 45 °. In particular, the light is reflected back of the screen 22 at a given projection angle phi _h , while the measurement is of the intensity of the light transmitted through the screen 22 as a function of the horizontal viewing angle and the intensity of the red / green and red / It is done for strength. The results of these tests are shown in the form of graphs in FIGS. 10-17. In particular, Figures 10 and 11 are graphs of the red / green and red / blue color shifts measured for a horizontal viewing range of ± 40 ° at the center position of the screen with respect to an angle φ _h of 0 °, respectively, A graph showing the screen luminance measured for the viewing range as a percentage of the maximum white luminance. Figures 12 and 13 are graphs of the red / green and red / blue color shifts measured for a horizontal viewing range of +/- 40 [deg.] From the center position of the screen for an angle [phi] _h of 15 [ Is a graph showing the measured screen luminance as a percentage of the maximum white luminance. Figures 14 and 15 are graphs of the red / green and red / blue color shifts measured for a horizontal viewing range of ± 40 ° from the center position of the screen for an angle φ _h of 30 ° respectively and a horizontal viewing range of ± 40 ° Is a graph showing the measured screen luminance as a percentage of the maximum white luminance. Figures 16 and 17 are graphs of the red / green and red / blue color shifts measured for a horizontal viewing range of ± 40 ° from the center position of the screen for an angle φ _h of 45 °, and a horizontal viewing range of ± 40 ° Is a graph showing the measured screen luminance as a percentage of the maximum white luminance.

In yet another variation of the configuration of the present invention, each individual projection cathode ray tube cooperates with at least one individual mirror, wherein each individual mirror reflects each image reflected by the mirror on the back side of the screen To be focused generally at the same point of view. Figure 18 shows a preferred embodiment of a variant of the invention in which the mirrors 20 in the present invention are replaced by mirrors 50, The mirrors 50, 55 and 60 are respectively oriented so that the images are projected by the projection cathode ray tubes 14, 16 and 18, respectively, by reflecting light along the optical axis which is focused at the center of the screen 22. The idea of the present invention and in particular the holographic screen is that the optical axes of the mirrors allow mirrors (50, 55, 60) that do not need to be close to the screen (22) at most right angles. Rather, by using the teachings of the present invention, the image reflected by the mirrors 50, 55, 60 onto the screen 22 can be projected from 0 to 30, preferably from 15 to 30, most preferably from about 15 It is incident on the mirrors at an angle.

These and other features of the present invention will be apparent to those skilled in the art from the description herein provided that it is possible to design and produce a rear projection screen television having a cabinet size smaller than the cabinet size .

The invention, which has been described with reference to the above-described exemplary embodiments and additional embodiments, will now be apparent to those skilled in the art. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (20)

A plurality of image projectors 14, 16, 18 for each image of different colors, each having a projection axis - a predetermined two adjacent image projectors define a pair of image projectors, each pair of image projectors defining an incident angle And has a projection axis. At least one hologram (26) disposed on a double-printed substrate (24) over at least a single optical transmission panel (38), the method comprising: receiving an image from the projector on a first side A projection screen 22 for displaying the displayed image so as to be optically distributed; Along the optical path between the projectors 14, 16, 18 and the projection screen 22, By directing an image from the projector to be reflected onto the first side and defining a projection angle for an axis perpendicular to the screen for each image, the projection screen redirects the reflected image on the projection screen, At least one mirror (20) for directing the image displayed on the side to a display angle that is an angle ranging from 0 [deg.] To 5 [deg.] With respect to an axis perpendicular to the screen, The screen 22 forms an optical arrangement and an interference arrangement that varies horizontally and vertically over the clock, and the screen has an optical arrangement of approximately 5 degrees for all of the incident angles in a range greater than 0 degrees and less than about 30 degrees As determined by the maximum value obtained from at least one of the following explanations, Here,? Is an arbitrary angle within the horizontal viewing angle range, C (?) Is the color shift at the? Angle, red (?) Is the red luminance level at the? , And green ([theta]) is the green luminance level at the B angle And a display unit for displaying the projection image. The projection television of claim 1, wherein the projection angle is in the range of 0 ° to 30 °. The projection television of claim 1, wherein the projection angle is in the range of 0 ° to 15 °. The projection television of claim 1, wherein the projection angle is at least 15 degrees. 2. The projection system of claim 1, wherein the at least one mirror (20) is directed between the plurality of image projectors (14,16,18) and the projection screen (22) television. 6. The projection television of claim 5, wherein the projection angle comprises a maximum angle from 10 [deg.] To 30 [deg.]. 6. The projection television of claim 5, wherein the projection angle comprises a maximum angle from 15 to 30 degrees. 6. The projection television of claim 5, wherein the projection angle comprises a maximum angle of at least 15 degrees. The apparatus of claim 1, wherein said at least one mirror (20) is oriented between said plurality of image projectors (14,16, 18) and projection screen (22) such that said projection angle comprises a maximum lateral angle of approach It is a projection television. 10. The projection television of claim 9, wherein the projection angle comprises a maximum lateral approach angle of from 10 [deg.] To 30 [deg.]. 10. The projection television of claim 9, wherein the projection angle comprises a maximum lateral approach angle from 15 to 30 degrees. 10. The projection television of claim 9, wherein the projection angle comprises a maximum lateral approach angle of at least 15 degrees. The projection television of claim 1, wherein said at least one mirror (20) comprises at least one individual mirror for each individual image projector (14, 16, 18) in said plurality of image projectors. The projection television of claim 1, wherein the screen (22) comprises at least two holograms stacked on top of one another, the hologram having independent variation in optical properties across the field of view. The projection television of claim 1, wherein the screen comprises at least one Fresnel element doubled on the at least one hologram. 16. The projection television of claim 15, comprising at least two Fresnel elements (29, 31) stacked on the back side of the hologram and having a dual-illuminated collimation effect. 17. The projection television of claim 16, wherein said at least two Fresnel elements (29, 31) have optical properties that vary across respective vertical and horizontal ranges of field of view. 18. The projection television of claim 17, wherein the at least two Fresnel elements (29, 31) have varying focal lengths over respective vertical and horizontal ranges of field of view. The projection television of claim 1, wherein the substrate (24) comprises a polyethylene terephthalate resin film. The projection television of claim 1, wherein the three-dimensional hologram (26) has the following performance characteristics. Horizontal Half Viewing Angle: 38 ° ± 3 ° Vertical half viewing angle: 10 ° ± 1 ° Screen gain: ≥8 Color shift: ≤3