JP2007163832A - Screen and back projection type display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission type screen with which a continuous and smooth image can be obtained and a thin type back projector equipped with the screen. <P>SOLUTION: Partial projection light which is reflected and inverted by a reflecting surface Re of a reflecting prism 1 is inverted again by a lens 3 as an inversion part, so a partial image that the partial projection light represents is projected on a display surface Sf as a positive-directional partial image before incidence on the reflecting surface Re. Consequently, an image is parted by a plurality of reflecting surfaces Re, partial images are made uniform to a positive direction through two-time image inversion by the reflecting surfaces Re and lenses 3, so no different image is formed between successive partial images. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a transmissive screen and a rear projection display device including the screen.

  The transmissive screen projects an image of projection light incident from the back onto a display surface in front of the screen. Such a transmission screen is often used in a rear projection display device (hereinafter also referred to as a “rear projector”) including a screen and a projection device that projects projection light within one individual.

FIG. 10 is a side sectional view showing a schematic configuration of a conventional rear projector.
The conventional rear projector 300 includes a projection device 31, a mirror 32 that reflects the projection light L emitted from the projection device, a transmission screen 33 on which the projection light L reflected by the mirror 32 is incident, and the like. It was.
The projection light L is a light beam that represents an image with the optical axis Lc as a substantially center. After being reflected by the mirror 32, the optical axis Lc forms an incident angle θ with respect to the perpendicular from the screen 33 surface. The light enters the back surface Sb and projects an image on the display surface Sf.
Such a conventional rear projector has a feature that a large screen can be easily obtained by adjusting the magnification of the projection light, but is substantially perpendicular to the screen (incident angle θ≈0 °). Since the projection light is incident, the depth Th becomes long due to an optical system such as a reflection mirror, which makes it difficult to reduce the thickness.

FIG. 11 is an enlarged cross-sectional view in the vicinity of the center of a conventional transmission screen.
In order to solve the above problems, transmission screens such as those disclosed in Patent Documents 1 to 3 have been proposed. The screen 20 increases the incident angle θ of the projection light L to the screen by providing a plurality of reflecting prisms on the back surface Sb of the screen 20.
Specifically, the reflecting prism 21 includes an incident surface In that is a transparent plane and a reflecting surface Re that is a total reflection surface, and the projection light L incident from the incident surface In is reflected by the reflecting surface Re. Reflected to the display surface Sf side of the screen 20. Since FIG. 11 is a cross section of a substantially central portion of the screen, the projection light L is described as being incident substantially perpendicularly to the incident surface In.
This makes it possible to project an image on the display surface Sf of the screen 20 even when the incident angle θ of the projection light L is large.
10 has a lamp as a light source, a light modulation element for modulating substantially white light emitted from the lamp into modulated light representing an image, and expands the modulated light to be emitted as projection light. It includes a projection lens (both not shown). Here, since the projection light L is an enlarged image of the modulated light modulated by a plurality of pixels in the form of a lattice of light modulation elements, for example, as shown by pixels a and b in FIG. It can be captured as a bundle of light representing a plurality of images corresponding to pixels.

JP-A-57-109481 JP 60-173533 A JP-A-6-27535

However, in the conventional screen 20 as shown in Patent Documents 1 to 3, when an image corresponding to one pixel straddles the two reflecting prisms 21, the image is reflected between the two reflecting surfaces Re and divided. There is a problem that images of adjacent pixels are mixed.
For example, in the case of the pixel a in FIG. 11, the image of the pixel a is divided into an image a1 and an image a2, and is reflected by the corresponding reflecting surface Re to form a projected image on the display surface Sf of the screen 20. However, the image b1 of the pixel b has entered between the image a1 and the image a2. This occurs because the top and bottom of the image is inverted due to reflection by the reflection surface Re, and the image b1 reflected by the same reflection surface Re as the image a2 comes under the image a2. Yes.
Further, this phenomenon is not limited to the pixels a and b, but may occur in all the pixels constituting the projection light L incident on the screen 20.
As described above, the image displayed on the conventional screen 20 has a problem in that it is difficult to see because the continuity is poor and the resolution is lowered.

  In order to solve the above-described problems, an object of the present invention is to provide a transmissive screen capable of obtaining a continuous and smooth image and a thin rear projector including the screen.

  In order to achieve the above object, according to the screen of the present invention, a transmissive screen comprising a back surface on which projection light from a projection device is incident and a display surface on which an image by the projection light is projected. Inversion provided as a pair for each of a plurality of reflecting portions provided on the back surface that reflects the projection light toward the display surface side and a plurality of reflecting portions that reversely invert the partial projection light reflected and inverted by the reflecting portion. A section.

According to this configuration, since the reflected partial projection light is inverted again by the inverting unit, the partial image represented by the partial projection light is displayed on the display surface as a partial image in the positive direction before entering the reflecting unit. Projected.
Therefore, unlike a conventional screen in which different images enter between successive partial images due to only one reflection by the reflecting surface, the screen of the present invention can prevent an image from being divided by a plurality of reflecting surfaces. Since the partial images are arranged in the positive direction by the image reversal performed twice by the reflection surface and the reversal unit, different images do not enter between successive partial images.
Therefore, according to the present invention, it is possible to provide a transmissive screen capable of obtaining a continuous and smooth image.

  According to the screen of the present invention, each of the plurality of reflecting portions is a reflecting prism having an incident surface on which projection light is incident and a reflecting surface that totally reflects the incident projection light toward the display surface, The pair of inversion portions is preferably a lens provided between each reflection prism and the display surface.

According to this configuration, since the inverting unit is a lens provided between the pair of reflecting prisms and the display surface, the partial projection light that is inverted by reflection by the reflecting surface of the reflecting prism is refracted by the lens. Is reversed again and is displayed on the display surface as a partial image in the positive direction.
Therefore, according to the present invention, it is possible to provide a transmissive screen capable of obtaining a continuous and smooth image.

  According to the screen of the present invention, each of the plurality of reflecting portions is a reflecting prism having an incident surface on which projection light is incident and a first reflecting surface that totally reflects the incident projection light toward the display surface. The pair of inversion parts is preferably a second reflection surface that totally reflects the partial projection light reflected by the reflection surface toward the display surface.

According to this configuration, since the inversion unit is the second reflection surface that reflects the partial projection light reflected by the reflection surface toward the display surface, the partial projection light inverted by the reflection by the first reflection surface of the reflection prism. Is reflected again by the second reflecting surface and is projected on the display surface as a partial image in the positive direction.
Therefore, according to the present invention, it is possible to provide a transmissive screen capable of obtaining a continuous and smooth image.

  According to the screen of the present invention, the reflecting prism preferably has a second reflecting surface in addition to the incident surface and the first reflecting surface.

According to this configuration, since the reflecting prism has the second reflecting surface in addition to the incident surface and the first reflecting surface, the reflecting portion and the inverting portion are configured as an integral reflecting prism.
Therefore, the screen can be configured simply.
Therefore, according to the present invention, it is possible to provide a transmission screen capable of obtaining a continuous and smooth image with a simple configuration.

  According to the screen of the present invention, it is preferable that the incident surface includes a curved surface.

According to this configuration, since the incident surface includes a curved surface, the partial projection light can be condensed or diffused by adjusting the curvature of the curved surface.
Therefore, desired brightness and viewing angle of the display surface can be obtained.
Therefore, according to the present invention, it is possible to provide a transmissive screen that displays a bright and easy-to-see image.

  According to the screen of the present invention, in the first reflection surface and the second reflection surface, it is preferable that either one of the reflection surfaces or both the reflection surfaces include a curved surface.

According to this configuration, one of the first reflecting surface and the second reflecting surface, or both reflecting surfaces are configured to include a curved surface, and therefore, partial projection is performed by adjusting the curvature of the curved surface. Light can be collected or diffused.
Therefore, desired brightness and viewing angle of the display surface can be obtained.
Therefore, according to the present invention, it is possible to provide a transmissive screen that displays a bright and easy-to-see image.

  The screen according to the present invention is a light shielding mask having a plurality of openings that block external light incident from the display surface and allow partial projection light to pass between the plurality of inversion portions and the display surface. It is preferable that a light shielding plate is further provided.

According to this configuration, the light shielding plate that is a light shielding mask having a plurality of openings that blocks external light incident from the display surface and allows partial projection light to pass between the plurality of inversion portions and the display surface. Further, since the light is incident, the external light incident from the display surface of the screen is absorbed by the light shielding plate, and the reduction in contrast can be suppressed.
Therefore, according to the present invention, it is possible to provide a transmissive screen from which a sharp and clear image can be obtained.

  According to the screen of the present invention, on the display surface side of the light shielding plate, there is provided a diffusion plate that is a flat plate constituting the display surface and diffuses the projection light emitted from the opening of the light shielding plate. Is preferred.

According to this configuration, on the display surface side of the light shielding plate, there is provided a diffusion plate that diffuses the projection light emitted from the opening of the light shielding plate, which is a flat plate constituting the display surface. The partial projection light condensed by the lens of each part is diffused by the diffusion plate, and a continuous image with uniform brightness is projected on the display surface.
Therefore, according to the present invention, it is possible to provide a transmissive screen capable of obtaining a continuous and smooth image.

  In order to achieve the above object, according to the rear projection display device of the present invention, the screen described above, a projection device that emits projection light representing an image, and the reflected light is incident on the rear surface of the screen. And an incident angle that is an angle formed by an optical axis that is substantially the center of the projection light and a perpendicular from the screen surface forms a predetermined acute angle.

According to this configuration, since the incident angle, which is the angle formed by the optical axis that is the approximate center of the projection light, and the perpendicular from the screen surface forms a predetermined acute angle, the incident angle is approximately “0 °”. Compared to the conventional rear projection display device, the rear projection display device can be made thinner.
Furthermore, the rear projection display device of the present invention includes a transmissive screen that can obtain a continuous and smooth image even when the incident angle of the projection light is a predetermined angle smaller than a right angle.
Therefore, according to the present invention, it is possible to provide a thin rear projection display device capable of obtaining a continuous and smooth image.

  According to the rear projection display device of the present invention, the projection device includes a light source unit that generates light, and light modulation that generates modulated light representing an image by modulating light emitted from the light source unit according to an image signal. And a projection unit that expands the modulated light generated by the light modulation element and emits the light as projection light. The light modulation element is a transmissive liquid crystal panel, a reflective liquid crystal panel, a tilt reflective mirror device, or a laser. It is preferably either a scanning optical element or a spontaneous light modulation element array.

In a projection apparatus that magnifies and projects modulated light according to an image signal, a transmissive liquid crystal panel, a reflective liquid crystal panel, a tilt reflective mirror device, or a laser scanning optical element is used as a light modulation element that generates modulated light. Alternatively, a spontaneous light modulation element array is often used. This is because the light emitted from the light source device can be efficiently converted into modulated light representing an image by using these light modulation elements.
According to this configuration, the projection apparatus includes a light modulation element of any one of a transmission type liquid crystal panel, a reflection type liquid crystal panel, a tilt reflection mirror device, a laser scanning optical element, or a spontaneous light modulation element array. Thus, the light emitted from the light source unit can be efficiently converted into modulated light representing an image.
Therefore, a vivid projection image can be obtained.
Therefore, it is possible to provide a rear projection display device that can obtain a vivid projection image.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(Embodiment 1)
<Outline of rear projector>
FIG. 1 is a schematic configuration diagram of a rear projector in an embodiment of the present invention.
A rear projector 100 that is a rear projection display device expands projection light L representing an image emitted from a built-in projection device 11 and projects the image onto a transmissive screen 13 provided.
The rear projector 100 includes a mirror 12 and the like in addition to the projection device 11 and the screen 13.
The mirror 12 is a substantially flat plane mirror provided substantially parallel to the screen 13, and totally reflects the projection light L radiated from the projection device 11 and makes it incident on the back surface Sb of the screen 13. The mirror 12 is configured by forming a highly reflective thin film layer such as aluminum or a dielectric multilayer film layer on the surface of a hard synthetic resin such as an acrylic resin.
The mirror 12 is not limited to being provided to be substantially parallel to the screen 13 as long as the projection light L can be incident on the screen. Further, for example, a configuration with a plurality of sheets or a curved mirror may be used.
The projection light L totally reflected by the mirror 12 enters the back surface Sb of the screen 13 and projects an image on the display surface Sf of the screen 13. Here, the projection light L is incident such that an incident angle θ, which is an angle formed by the optical axis Lc, which is substantially the center of the projection light L, and the perpendicular from the screen 13 is a predetermined acute angle. The predetermined acute angle is an angle smaller than a right angle, and the incident angle θ as a specific predetermined acute angle is preferably 50 to 80 °.

<Projector overview>
FIG. 2 is a schematic configuration diagram centering on the optical unit of the projection apparatus.
The projection device 11 separates the light W emitted from the lamp 51, which is a light source, into three primary color components of red light R, green light G, and blue light B, and a liquid crystal for each color light as a light modulation element for each color light. This is a so-called “liquid crystal three-plate projector” that modulates the light valve 65R, 65G, 65B according to the image signal and enlarges and projects the full-color modulated light synthesized again by the projection lens 68.
The projection device 11 includes an optical unit 50, a circuit unit 70, and the like.
The lamp 51 is a lamp capable of obtaining high brightness such as a high-pressure mercury lamp, a metal halide lamp, and a halogen lamp.

<Outline of optical section>
In addition to the lamp 51, the liquid crystal light valves 65R, 65G, and 65B and the projection lens 68, the optical unit 50 includes an integrator 52, a polarization conversion element 53, reflection mirrors 54, 56, 59, 61, and 67, and a red light transmission dichroic. The reflecting mirror 55, a blue light transmitting dichroic reflecting mirror 57, relay lenses 58 and 60, a cross dichroic prism 66, and the like are included.
The integrator 52 has a configuration in which optical systems in which small lenses having a substantially rectangular outline as viewed from the illumination optical axis direction are arranged in a matrix form face each other, and the illuminance distribution of the light W from the lamp 51 is substantially uniform. To. Similarly, a configuration using a lot integrator having a function of making the illuminance distribution uniform may be used.
The polarization conversion element 53 is an optical element that converts light composed of two types of polarization components whose illuminance distribution is made uniform by the integrator 52 into one type of polarized light that can be modulated by the liquid crystal light valves 65R, 65G, and 65B. is there. Thereby, the utilization efficiency of light is improved.

The reflection mirror 54 reflects the light W converted into one type of polarized light by the polarization conversion element 53 toward the red light transmitting dichroic mirror 55 side.
The red light transmitting dichroic mirror 55 is an optical element including a dielectric multilayer film that reflects green light G and blue light B and transmits red light R, transmits red light R, and transmits green light G and blue light. B is reflected to the blue light transmitting dichroic mirror 57 side.
The reflection mirror 56 reflects the red light R transmitted through the red light transmission dichroic mirror 55 and makes it incident on the liquid crystal light valve 65R.
The blue light transmitting dichroic mirror 57 is an optical element including a dielectric multilayer film that transmits the blue light B and reflects the green light G. The blue light transmitting dichroic mirror 57 transmits the blue light B and reflects the green light G. The reflected green light G enters the liquid crystal light valve 65G.

The blue light B transmitted through the blue light transmitting dichroic mirror 57 is reflected by the reflecting mirror 59 via the relay lens 58 and further reflected by the reflecting mirror 61 via the relay lens 60, and then is reflected on the liquid crystal light valve 65B. Incident.
The relay lenses 58 and 60 have an action of preventing the attenuation of the light amount, and prevent the attenuation of the blue light B that passes through the optical path longer than the optical paths of the red light R and the green light G.
The cross dichroic prism 66 synthesizes modulated light representing an image for each color light emitted from the three liquid crystal light valves 65R, 65G, and 65B by two cross dichroic films 66a and 66b provided in a substantially X shape. Modulated light representing a full color image is emitted.
The cross dichroic film 66a is a dielectric multilayer film that reflects red light R and transmits green light G and blue light B, and the cross dichroic film 66b reflects blue light B and reflects red light R and green light. It is a dielectric multilayer film that transmits light G.

The reflection mirror 67 reflects the modulated light combined by the cross dichroic prism 66 to the projection lens 68 side.
The projection lens 68 as a projection unit is composed of a plurality of lenses, and emits projection light having a wide angle of modulated light to the upper surface side of the projection device 11. The emitted projection light is incident on the reflection mirror 12 of FIG. The reflection mirror 67 may be provided in the projection lens 68.
The modulated light modulated by the liquid crystal light valves 65R, 65G, and 65B having a plurality of pixels corresponding to the inherent resolution and the projection light obtained by enlarging the modulated light represent portions of the plurality of pixels. It can be captured as a bundle of projection light. For example, when the resolution is XGA (1024 × 768), the partial projection light corresponding to 786,432 pixels and when the resolution is SXGA (1280 × 1024) can be captured as a bundle of light beams.

<Outline of circuit section>
Next, an outline of the circuit unit 70 of the projection device 11 will be described.
The circuit unit 70 is suitable for displaying on the liquid crystal light valves 65R, 65G, and 65B by applying a plurality of image processing to an image signal representing an input image, and a power supply unit that supplies power to each unit of the rear projector 100. An image processing unit for generating the image signal, a liquid crystal driver for driving each liquid crystal light valve by the image signal generated by the image processing unit, and a control unit for controlling the functions of each unit and the entire rear projector 100 (not shown) )) Is included.
In addition to the scaling function that adjusts the resolution without changing the screen shape of the image, the image processing by the image processing unit is caused by the large incident angle of the projected light on the screen (also referred to as “tilt angle”). A trapezoid correction process for correcting trapezoidal distortion of a projected image to be performed is also included.

<< Schematic configuration of first screen >>
FIG. 3 is an enlarged cross-sectional view of the vicinity of the center portion of the first screen in the embodiment of the present invention. For comparison with the conventional screen 20 in FIG. 11, the same components will be described with the same reference numerals.
The first screen 13 includes a plurality of reflecting prisms 1, a lens 3 as a reversing unit provided as a pair, a condenser lens 4, a diffusion plate Dif, a light shielding plate Sh, and the like.

The reflecting prism 1 as a reflecting portion includes an incident surface In and a reflecting surface Re that is a reflecting portion.
The incident surface In is a plane provided substantially perpendicular to the projection light L, and guides the incident projection light L to the reflection surface Re.
The reflecting surface Re is a plane set so that the projection light L incident from the incident surface In exceeds the critical angle, and reflects the incident projection light L to the lens 3 side. Moreover, the structure which makes a total reflection surface by providing highly reflective thin film layers, such as aluminum and a dielectric multilayer, may be sufficient.
The lens 3 is a cylindrical lens provided integrally with the reflecting prism 1, and refracts the projection light L reflected by the reflecting surface Re at the interface and emits it to the condenser lens 4 side. Since the lens 3 is a cylindrical lens, it has a function of returning partial projection light representing a partial image inverted by reflection on the reflection surface Re to a positive partial image by a one-dimensional refraction action.
The plurality of reflecting prisms 1 and the lenses 3 are integrally formed as a prism array 5.
As a material of the prism array 5, for example, an acrylic resin having excellent optical characteristics and molding processability is used. The resin is not limited to an acrylic resin, and may be a polycarbonate resin, an olefin resin, or a styrene resin as long as it is a transparent synthetic resin for optical use. The prism array 5 can be formed by extrusion molding, heat pressing, or injection molding of these synthetic resins.

Here, an aspect of an image represented by the continuous pixel a and pixel b between the reflection surface Re and the diffusion plate Dif will be described.
The image represented by the pixel a is divided into an image a1 and an image a2, and is reflected by the corresponding reflecting surface Re. At this time, since the image a2 is reflected together with the image b1 of the adjacent pixel b, the image after being reflected by the reflecting surface Re is inverted, and the image a2 is displayed in the upper order and the image b1 is displayed in the lower order. Yes.
The partial projection light in the order of the image a <b> 2 on the upper side and the image b <b> 1 on the lower side is inverted again by the refraction of the lens 3 and enters the condenser lens 4.
The condensing lens 4 is a cylindrical lens, condenses the partial projection light from the lens 3 to be enlarged, and emits it as a light beam substantially perpendicular to the display surface Sf. The plurality of condensing lenses 4 are configured as an integral sheet-like condensing lens array 6 made of the same transparent synthetic resin for optics as that of the prism array 5.
The diffusing plate Dif constituting the display surface Sf is a sheet-like member configured by uniformly dispersing a light diffusing agent on a transparent base material such as an acrylic resin, and the partial projection light incident from the condenser lens 4 Is diffused to a certain range of the display surface Sf. The certain range in which the partial projection light is diffused is about the size corresponding to the pixel corresponding to the partial projection light in the image displayed on the display surface Sf.

The images displayed on the display surface Sf in this way are the image a1, the image a2, the image b1, and the image b2 from below, and are continuous images in the order of the partial projection light before entering the back surface Sb.
Further, between the prism array 5 and the condenser lens array 6, a light shielding plate Sh is provided with a portion through which a plurality of partial projection lights pass as openings. The light shielding plate Sh is an all black light shielding mask and absorbs external light incident from the display surface Sf.
As for the planar shape of the prism array 5, it is preferable that the prism array 5 constitutes a circular Fresnel lens having the approximate center of the screen 13 as the center of a concentric circle when the screen 13 is viewed from the front. Alternatively, horizontal and vertical linear Fresnel lenses having an action obtained by resolving the refractive action of the circular Fresnel lens in the horizontal and vertical directions may be configured. In this case, the lens 3 and the condenser lens 4 are provided along the planar shape of the prism array 5.

<< Schematic configuration of screens of different modes >>
FIG. 4 is an enlarged cross-sectional view in the vicinity of the central portion of a different aspect of the first screen in the embodiment of the present invention. In addition, the same number is attached | subjected about the component same as the screen 13, and the overlapping description is abbreviate | omitted.
Here, a screen 14 having a simplified configuration of the screen 13 will be described with reference to FIG.
The screen 14 is a screen in which the condensing lens array 6 including the condensing lens 4 is omitted from the configuration of the screen 13.
The screen 14 includes a plurality of reflecting prisms 1, a lens 3 as an inverting portion provided as a pair, a diffusion plate Dif as a diffusion layer, a light shielding plate Sh, and the like.

The reflecting prism 1 that is a reflecting portion and the lens 3 that is a cylindrical lens are the same as described with reference to the screen 13, and are configured as an integral prism array 5.
The diffusion plate Dif is also the same diffusion plate as described in the first screen 13.
The light shielding plate Sh has the same configuration as that described in the first screen 13, but is provided between the prism array 5 and the diffusion plate Dif.

Here, an aspect of an image represented by the continuous pixel a and pixel b between the reflection surface Re and the diffusion plate Dif will be described.
The image represented by the pixel a is divided into an image a1 and an image a2, and is reflected by the corresponding reflecting surface Re. At this time, since the image a2 is reflected together with the image b1 of the adjacent pixel b, the image after being reflected by the reflecting surface Re is inverted, and the image a2 is displayed in the upper order and the image b1 is displayed in the lower order. Yes.
The partial projection light in the order of the image a <b> 2 on the upper side and the image b <b> 1 on the lower side is inverted again by the refraction of the lens 3 and enters the diffusion plate Dif.
The diffusing plate Dif is installed at a position where the partial projection light emitted from the lens 3 is incident when the size of the partial projection light is enlarged to approximately the same size as when the light is incident on the lens 3 from the reflecting surface Re. . For this reason, the partial projection light is diffused in the diffusion plate Dif before being further magnified, and an image is displayed on the display surface Sf.
The images displayed on the display surface Sf in this way are the image a1, the image a2, the image b1, and the image b2 from below, and are continuous images in the order of the partial projection light before entering the back surface Sb.

《Visual dependency adjustment mode》
Fig.5 (a) is explanatory drawing of the 1st clear vision direction aspect in the screen of this invention. FIG.5 (b) is explanatory drawing of the 2nd clear vision direction aspect in the screen of this invention.
Here, the clear viewing direction aspect on the screen 13 will be described with reference to FIGS.

In the description of the screen 13 in FIG. 3, the projection light L has been described as being incident substantially perpendicularly to the incident surface In of the reflecting prism 1, but the present invention is not limited to this.
In the substantially central portion of the screen 13 in FIG. 5A, the projection light L is incident on the incident surface In of the reflecting prism 1 substantially perpendicularly as described with reference to FIG. Partial projection light is incident on. Due to this and the blending degree of the diffusing agent in the diffusing plate Dif, the partial projection light in the central portion of the screen 13 is more forward (z-axis) than the vertical direction (y-axis direction) of the screen as indicated by the diffusion range Cen It is greatly diffused in the negative direction.

Further, in consideration of the visual dependency of the observer M in the direction facing the screen 13, the upper part of the screen 13 diffuses the partial projection light to the front more than the vertical direction of the screen, similarly to the diffusion range Cen, It is preferable to diffuse slightly downward (in the negative y-axis direction).
Further, the incident angle of the projection light on the upper portion of the screen 13 is larger than the incident angle θ at the center of the screen because the projection light L is incident while being emitted.
For this reason, in the upper part of the screen 13, by adjusting the angles of the incident surface In and the reflecting surface Re, a partial projection light incident at an angle larger than the incident angle θ is in a range as indicated by the diffusion range Top. Has spread.

Similarly, in the lower part of the screen 13, it is preferable that the partially projected light is diffused to the front more than the vertical direction of the screen as in the diffusion range Cen, and slightly diffused upward (y-axis positive direction).
The incident angle of the projection light at the lower part of the screen 13 is smaller than the incident angle θ at the center of the screen because the projection light L is incident while being emitted.
For this reason, in the lower part of the screen 13, by adjusting the angles of the incident surface In and the reflecting surface Re, the partial projection light incident at an angle smaller than the incident angle θ is in a range indicated by the diffusion range Dow. Has spread.
In addition, here, the upper portion, the central portion, and the lower portion of the screen 13 have been described. For example, it is adjusted so as to face the direction of the viewpoint of the observer M facing the position of about 4 to 7 m from the screen 13.
Although the detailed description is omitted, the degree of diffusion in the left-right direction (x-axis direction) of the screen 13 is greatly diffused in the left-right direction rather than the front direction in any of the upper, central, and lower portions of the screen 13. ing. This is performed, for example, by adjusting the mixing ratio of the diffusing agent in the diffusing plate Dif, and the visual dependency of the screen 13 from the left-right direction is improved.

As described above, by adjusting the degree of diffusion of the projection light L on the screen 13, in the case of the observer M whose viewpoint is substantially opposite to the screen 13 in FIG. 5A, the diffusion range Cen and the diffusion range Top. The diffused light indicated by the arrow in the diffusion range Dow is observed.
Similarly, in the case of an observer M who has a viewpoint at a position where the screen 13 of FIG. 5B is looked up slightly, the diffused light indicated by the arrows in the diffusion range Cen, the diffusion range Top, and the diffusion range Dow is observed. It will be.
As described above, when the observer is in front of the screen 13, the visual dependence can be improved by the large diffusion in the forward direction wherever the observer is.
The reflection angle of the projection light L may be adjusted by making the incident surface In and the reflective surface Re curved. Moreover, the structure which makes either one a curved surface may be sufficient. Further, it may be performed in combination with the angle adjustment of the incident surface In or the reflective surface Re.
In addition, although demonstrated using the screen 13 here, the screen 14 (FIG. 4) provided with the same prism array 5 can also be comprised similarly.

As described above, according to the present embodiment, the following effects can be obtained.
(1) Since the inverted partial image represented by the partial projection light reflected by the reflecting surface Re of the reflecting prism 1 is inverted again by the lens 3 as the inverting unit, the partial image is incident on the reflecting surface Re. The image is displayed on the display surface Sf as a previous partial image in the positive direction.
Therefore, according to the screens 13 and 14 of the present invention, even if the image is divided by the plurality of reflection surfaces Re, the partial image is adjusted in the positive direction by the image reversal twice by the reflection surface Re and the lens 3. Therefore, different images do not enter between successive partial images.
Accordingly, it is possible to provide the transmission screens 13 and 14 that can obtain a continuous and smooth image.

(2) Since the inverting unit is the lens 3 provided between the pair of reflecting prism 1 and the display surface Sf, the partial projection light inverted by the reflection by the reflecting surface Re of the reflecting prism 1 is the lens. The image is inverted again by the refraction of 3, and is displayed on the display surface Sf as a partial image in the positive direction.
Accordingly, it is possible to provide the transmission screens 13 and 14 that can obtain a continuous and smooth image.

(3) Since the display surface Sf is further provided with a diffusion plate Dif for diffusing the partial projection light emitted from the condenser lens 4 or the lens 3, the incident partial projection light is respectively diffused by the diffusion plate Dif. As a result, an image that is diffused, continuous, and uniform in brightness is displayed on the display surface Sf.
Accordingly, it is possible to provide the transmission screens 13 and 14 that can obtain a continuous and smooth image.

(4) A light shielding plate Sh that is a light shielding mask having a plurality of openings that blocks external light from the display surface Sf and allows partial projection light to pass therethrough is further provided between the prism array 5 and the diffusion plate Dif. Therefore, the external light incident from the display surface Sf is absorbed by the light-shielding plate Sh, and a reduction in image contrast can be suppressed.
Accordingly, it is possible to provide the transmission screens 13 and 14 that can obtain a sharp and clear image.

(5) Since the incident surface In or the reflecting surface Re of the reflecting prism 1 can be configured to include a curved surface, the partial projection light can be condensed or diffused by adjusting the curvature of the curved surface. it can.
Therefore, the projection light emitted from the display surface Sf of the screen can be directed toward the observer's viewpoint or can be condensed.
Accordingly, it is possible to provide the transmission screens 13 and 14 for projecting bright and easy-to-see images.

(6) Since the incident angle θ of the optical axis with respect to the vertical line from the screen 13 surface of the rear projector 100 forms a predetermined acute angle, the mirror 12 can be installed substantially parallel to the screen, and the depth Th can be made thin.
Furthermore, the rear projector 100 includes a transmissive screen 13 or 14 that can obtain a continuous and smooth image even when the incident angle θ of the projection light is an acute angle.
Therefore, it is possible to provide a thin rear projector 100 that can obtain a continuous and smooth image.

(7) In the circuit unit 70 of the projection display device 11, in addition to the scaling function for adjusting the resolution without changing the screen shape of the image, the incident angle of the projection light on the screen is an acute angle (also referred to as “tilt angle”). An image processing unit that performs image processing including trapezoidal correction processing for correcting trapezoidal distortion of the projected image due to the fact that
Therefore, it is possible to provide the rear projector 100 capable of projecting an image having no distortion that matches the rectangular screen even when the incident angle of the projection light is an acute angle.

(Embodiment 2)
<< Schematic configuration of second screen >>
FIG. 6 is a schematic configuration diagram of a second screen according to the second embodiment of the present invention.
The second screen 15 is a screen having a configuration suitable as the screen of the rear projector 100. Here, a schematic configuration of the screen 15 will be described with reference to FIG.
In addition, the same number is attached | subjected about the component same as the screen 13 of Embodiment 1, and the overlapping description is abbreviate | omitted.

The screen 15 includes a plurality of reflecting prisms 8, a diffusion plate Dif, a light shielding plate Sh, and the like.
The reflecting prism 8 as a reflecting portion is made of an optical transparent synthetic resin, and includes an incident surface In, a reflecting surface Re that is a first reflecting surface, and a reflecting surface 7 that is a second reflecting surface. Each of the resins described in the first embodiment can be used as the optical transparent synthetic resin, but an acrylic resin is employed here as a suitable example.
The incident surface In is a plane provided at a predetermined angle with respect to the projection light L, and after refracting the incident projection light L, guides it to the reflection surface Re.
The reflecting surface Re is a plane set so that the projection light L incident from the incident surface In exceeds the critical angle, and reflects the incident projection light L toward the reflecting surface 7 side. Moreover, the structure which makes a total reflection surface by providing highly reflective thin film layers, such as aluminum and a dielectric multilayer film layer, may be sufficient.
The reflection surface 7 that is the reversal part is a plane that is set so that the projection light L reflected from the reflection surface Re exceeds the critical angle, and reflects the incident projection light L to the diffusion plate Dif. Moreover, the structure which makes a total reflection surface by providing highly reflective thin film layers, such as aluminum and a dielectric multilayer, may be sufficient.

The projection light L incident at an incident angle θ from the incident surface In is refracted at the interface of the incident surface In, then reflected by the reflecting surface Re toward the reflecting surface 7, and reflected again by the reflecting surface 7. The light enters the diffusion plate Dif substantially perpendicularly.
Here, an aspect of an image represented by the continuous pixel a and pixel b between the reflection surface Re and the diffusion plate Dif will be described.
The image represented by the pixel a is divided into an image a1 and an image a2, and is reflected by the corresponding reflecting surface Re. At this time, since the image a2 is reflected together with the image b1 of the adjacent pixel b, the image after being reflected by the reflecting surface Re is inverted, and the image a2 is displayed in the upper order and the image b1 is displayed in the lower order. Yes.
The partial projection light in the order of the image a <b> 2 on the upper side and the image b <b> 1 on the lower side is inverted again by the reflection on the reflection surface 7 and enters the diffusion plate Dif.

The diffusing plate Dif constituting the display surface Sf is a sheet-like member configured by uniformly dispersing a light diffusing agent on a transparent base material such as an acrylic resin, and allows incident partial projection light to be incident on the display surface Sf. Spread over a certain range. The certain range in which the partial projection light is diffused is about the size corresponding to the pixel corresponding to the partial projection light in the image displayed on the display surface Sf.
The images displayed on the display surface Sf in this way are the image a1, the image a2, the image b1, and the image b2 from below, and are continuous images in the order of the partial projection light before entering the back surface Sb.
Further, between the plurality of reflecting prisms 8 and the diffusing plate Dif, there is provided a light shielding plate Sh having openings through which a plurality of partial projection lights pass. The light shielding plate Sh is an all black light shielding mask and absorbs external light incident from the display surface Sf.

《Reflecting prism design example》
FIG. 7 is a diagram showing one design mode of the reflecting prism in the second screen.
Here, a suitable design example of the reflecting prism 8 in the second screen 15 will be described with reference to FIG.

The projection light L enters from the incident surface In of the reflecting prism 8, is reflected by the reflecting surface Re, is reflected again by the reflecting surface 7, and then enters the diffusion plate Dif substantially perpendicularly.
Here, the reflection angle from the reflection surface 7 to the diffusion plate Dif is set to “β”, and the reflection angle from the reflection surface Re to the reflection surface 7 is set to “2β”.
Further, the angle formed by the vertical line from the intersection point p between the incident surface In and the reflection surface Re and the projection light L is set to “α”. The relationship between the angle α and the incident angle θ is expressed by equation (h).

前述した通り、入射角度θは、５０〜８０°が好適であることから、対応する角度αは、１０〜４０°となる。
反射プリズム８に要求される光学特性は、角度αが、１０〜４０°の範囲内の投写光Ｌを拡散板Ｄｉｆへ略垂直に入射させることである。
以下、この目的とする光学特性を得るために、交点ｐからの鉛直線と、入射面Ｉｎとが成す角度δを求める。
屈折の法則（「スネルの式」ともいう）により、入射面Ｉｎにおける投写光Ｌの屈折関係は、式（ｉ）で表される。なお、反射プリズム８の屈折率は「ｎ」、空気の屈折率は、１．０とする。

As described above, since the incident angle θ is preferably 50 to 80 °, the corresponding angle α is 10 to 40 °.
The optical characteristic required for the reflecting prism 8 is that the projection light L having an angle α in the range of 10 to 40 ° is incident on the diffusion plate Dif substantially perpendicularly.
Hereinafter, in order to obtain the desired optical characteristics, an angle δ formed by the vertical line from the intersection point p and the incident surface In is obtained.
According to the law of refraction (also referred to as “Snell's formula”), the refraction relationship of the projection light L at the incident surface In is expressed by the formula (i). The refractive index of the reflecting prism 8 is “n”, and the refractive index of air is 1.0.

式（ｉ）を、角度δを求める式に展開すると式（ｊ）となる。

When formula (i) is expanded into a formula for obtaining angle δ, formula (j) is obtained.

反射プリズム８の材質をアクリル樹脂として、屈折率ｎ＝１．４９を代入し、式（ｊ）により角度αが１０°のときの角度δを求めると、約「８．１９°」となる。
同様に、角度αが４０°のときの角度δを求めると、約「４３．３３°」となる。

When the material of the reflecting prism 8 is made of acrylic resin and the refractive index n = 1.49 is substituted and the angle δ when the angle α is 10 ° is obtained by the equation (j), it is about “8.19 °”.
Similarly, the angle δ when the angle α is 40 ° is approximately “43.33 °”.

In this way, the reflecting prism 8 corresponding to a suitable incident angle θ can be realized. Similarly to the description in FIGS. 5A and 5B of the first embodiment, by adjusting the reflection angle β from the reflection surface 7 to the diffusion plate Dif in the upper portion, the central portion, and the lower portion of the screen 15, Visual dependence can be improved.
The reflection angle β may be adjusted by making the incident surface In and the reflective surface Re curved. Moreover, the structure which makes either one a curved surface may be sufficient. Further, it may be performed in combination with the angle adjustment of the incident surface In or the reflective surface Re.

As described above, according to the present embodiment, the following effects can be obtained in addition to the corresponding effects of the first embodiment.
(1) The reflection surface 7 that is the reversing part is a second reflection surface that reflects the partial projection light reflected by the reflection surface Re that is the first reflection surface toward the display surface Sf. The partial projection light inverted by the reflection by the surface Re is reflected again by the reflection surface 7 and is projected on the display surface Sf as a partial image in the positive direction.
Therefore, it is possible to provide a transmissive screen 15 that can obtain a continuous and smooth image.

(2) Since the reflecting prism 8 has the reflecting surface 7 in addition to the incident surface In and the reflecting surface Re, the reflecting portion and the inverting portion are configured as an integral reflecting prism 8.
Therefore, the screen 15 can be configured simply.
Accordingly, it is possible to provide a transmissive screen 15 that can obtain a continuous and smooth image with a simple configuration.

(3) Since the incident surface In, the reflecting surface Re, or the reflecting surface 7 of the reflecting prism 8 can be configured to include a curved surface, the partial projection light is refracted and collected by adjusting the curvature of the curved surface. Can be light or diffuse.
Therefore, the visual dependency of the screen 15 can be improved.
Accordingly, it is possible to provide a transmissive screen 15 that projects a bright and easy-to-view image.

(4) The screen 15 is suitable for the rear projector 100 because a continuous and smooth image can be obtained even when the incident angle θ of the projection light is a predetermined angle smaller than a right angle.
When the screen 15 is adapted to the rear projector 100, the mirror 12 can be installed substantially parallel to the screen 15, and the depth Th can be reduced.
Therefore, it is possible to provide a thin rear projector 100 that can obtain a continuous and smooth image.

  Note that the present invention is not limited to the above-described embodiment, and various modifications and improvements can be added to the above-described embodiment. A modification will be described below.

(Modification 1)
FIG. 8 is a diagram showing a different mode of the first screen 13 in FIG. 3, and FIG. 9 is a diagram showing a mode of the condensing lens.
Here, with reference to FIGS. 8 and 9, a method of manufacturing the screen 33 having different forms of the screen 13 and the condensing lens array 46 of the screen 33 will be described with reference to FIG. 3 as appropriate.
The screen 33 includes the prism array 5, the condensing lens array 46, the diffusion plate Dif, and the like. The screen 33 differs from the first screen 13 only in the configuration of the condenser lens array 46.
The condenser lens array 46 includes a plurality of condenser lenses 41 and a light shielding plate Sh. The condenser lens 41 is a cellular cylindrical lens, and its function is the same as that of the condenser lens 4 of the screen 13. In addition, the function of the light shielding plate Sh is the same as that of the light shielding plate Sh of the screen 13.

The condensing lenses 41 are independent of each other, and are configured in a nail shape with a cylindrical lens as a head as shown in FIG. The condenser lens 41 can be easily manufactured by emission molding. In addition, since a plurality of condensing lenses 41 can be faced on a mold used for emission molding, a large number of condensing lenses 41 can be molded by one molding.
The light shielding plate Sh is provided adjacent to the diffusion plate Dif, and a plurality of holes into which the foot portions 41f of the condenser lens 41 are inserted are opened. The light shielding plate Sh can be easily manufactured by pressing or etching a light shielding sheet made of metal or synthetic resin.
The condensing lens array 46 is configured by inserting a foot portion 41f of the condensing lens 41 into the opening of the light shielding plate Sh.
The planar shape of the lens at the head of the condenser lens 41 is not limited to a quadrangle, and may be any shape that can be spread on the light shielding plate Sh without a gap, and may be a hexagon, for example.
With such a configuration, it is possible to provide a transmissive screen 33 provided with a condensing lens array 46 having an inexpensive and simple configuration and capable of obtaining a continuous and smooth image.

(Modification 2)
This will be described with reference to FIG. In each of the above-described embodiments, the projection device 11 modulates the color light according to the image signal by the liquid crystal light valves 65R, 65G, and 65B for each color light as the light modulation element, and recombines the full-color modulated light by the projection lens 68. Although described as a liquid crystal three-plate projector that performs enlarged projection, the present invention is not limited to this.
For example, the projection device 11 is configured to use a single-plate liquid crystal light valve in which red, green, and blue color filters are regularly arranged in a lattice pattern and can emit a full-color modulated light by one sheet. May be. Further, a configuration using a reflective liquid crystal display device or a tilt mirror device may be used. Note that, for example, in the case of a configuration using a tilt mirror device, the configuration of the optical unit 50 is different from the configuration of FIG. 2 depending on the light modulation element used, such that the polarization conversion element 53 is not necessary. Become.
Further, it may be a projection device having a configuration using a laser scanning optical system having a light modulation function, a spontaneous light modulation element array, or the like.
Even if it is these structures, the effect similar to each said embodiment can be acquired.

1 is a schematic configuration diagram of a rear projector in an embodiment. The schematic block diagram centering on the optical part of a projection apparatus. FIG. 3 is an enlarged cross-sectional view in the vicinity of the center portion of the first screen in the first embodiment. The expanded sectional view of the center part vicinity of a different form of a 1st screen. (A) Explanatory drawing of the 1st clear vision direction aspect in a screen, (b) Explanatory drawing of the 2nd clear vision direction aspect in a screen. FIG. 6 is a schematic configuration diagram of a second screen in the second embodiment. The figure which shows the design aspect of the reflecting prism in a 2nd screen. The figure which shows the different aspect of the 1st screen. The figure which shows the one aspect | mode of a condensing lens. FIG. 6 is a side sectional view showing a schematic configuration of a conventional rear projector. The expanded sectional view in the center part vicinity of the conventional transmissive screen.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,8 ... Reflection prism as a reflection part, 3 ... Lens as an inversion part, 4,41 ... Condensing lens, 5 ... Prism array, 6,46 ... Condensing lens array, 7 ... Inversion part and 2nd reflection Reflective surface as a surface, 11, 31 ... projection device, 12 ... mirror, 13, 14, 15 ... screen, 51 ... lamp as light source unit, 65R, 65G, 65B ... liquid crystal light valve as light modulation element, 68 ... Projection lens as projection unit, 100 ... rear projector as rear projection display, Dif ... diffusion plate as diffusion layer, In ... incident surface, Sh ... light shielding plate, Sf ... display surface, Sb ... rear surface, L ... projection Light, Lc: Optical axis, Re: Reflecting surface as the first reflecting surface, θ: Incident angle.

Claims (10)

A transmissive screen including a back surface on which projection light from a projection device is incident and a display surface on which an image of the projection light is projected;
A plurality of reflecting portions provided on the back surface for reflecting the projection light toward the display surface;
A screen, comprising: a reversing unit provided as a pair for each of the plurality of reflecting units for reversing the partially projected light reflected and reversed by the reflecting unit. Each of the plurality of reflection units is a reflection prism having an incident surface on which the projection light is incident and a reflection surface that totally reflects the incident projection light toward the display surface,
The screen according to claim 1, wherein the pair of inversion parts is a lens provided between each of the reflecting prisms and the display surface. Each of the plurality of reflection units is a reflection prism having an incident surface on which the projection light is incident and a first reflection surface that totally reflects the incident projection light to the display surface side,
2. The screen according to claim 1, wherein the pair of inversion units is a second reflection surface that totally reflects the partial projection light reflected by the reflection surface toward the display surface.   The screen according to claim 3, wherein the reflecting prism includes the second reflecting surface in addition to the incident surface and the first reflecting surface.   The screen according to claim 3, wherein the incident surface includes a curved surface. In the first reflecting surface and the second reflecting surface,
The screen according to any one of claims 3 to 5, wherein one of the reflection surfaces or both of the reflection surfaces includes a curved surface.   A light shielding plate, which is a light shielding mask having a plurality of openings that blocks external light incident from the display surface and allows the partial projection light to pass therethrough, is further provided between the plurality of inversion portions and the display surface. The screen according to any one of claims 1 to 6, wherein the screen is provided.   The diffusion plate for diffusing projection light emitted from the opening of the light shielding plate is provided on the display surface side of the light shielding plate, which is a flat plate constituting the display surface. Item 8. The screen according to Item 7. A screen according to any one of claims 1 to 8,
A projection device that emits projection light representing an image;
A mirror unit that reflects the projection light and enters the back surface of the screen, and
A rear projection display device, wherein an incident angle, which is an angle formed by an optical axis that is substantially the center of the projection light, and a perpendicular from the screen surface forms a predetermined acute angle. The projection device is generated by a light source unit that generates light, a light modulation element that generates modulated light representing an image by modulating light emitted from the light source unit according to an image signal, and the light modulation element A projection unit for enlarging the modulated light and emitting it as the projection light,
The light modulation element is any one of a transmissive liquid crystal panel, a reflective liquid crystal panel, a tilt reflection mirror device, a laser scanning optical element, or a spontaneous light modulation element array. The rear projection display device described.

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