JP3895907B2 - Rear projection display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a rear projection display device that projects image light obliquely on the back of a screen and observes the image from the front of the screen.
[0002]
[Prior art]
  An example of a conventional rear projection display device is shown in FIGS. FIG. 9 is a cross-sectional view illustrating a schematic configuration of a conventional rear projection display device, and FIG. 10 is a top view illustrating a schematic configuration of a projection unit in the rear projection display device of FIG. In the following description, a description will be made using a coordinate system in which the width direction of the rectangular screen 170 is the x axis, the height direction of the screen 170 is the y axis, and the direction perpendicular to the screen 170 is the z axis.
[0003]
  In this rear projection display device, as shown in FIG. 9, a projection unit 120 is disposed in a housing 110. A projection lens 130 is disposed at the light exit of the projection unit 120. A reflection mirror 160 is disposed on the back surface of the housing 110, and a transmissive diffusion screen 170 is disposed on the front surface of the housing 110. Then, the image light enlarged and projected from the projection unit 120 via the projection lens 130 is reflected by the reflection mirror 160 and then irradiated from the back surface side of the diffusion screen 170, and the image is displayed from the front surface side of the diffusion screen 170. Observed.
[0004]
  As shown in FIG. 10, the projection unit 120 includes a white light source 121 including a lamp 121 a and a reflector 121 b, and white light emitted from the white light source 121 is displayed in three colors by dichroic mirrors 122 and 123. Separated. The first dichroic mirror 122 selectively reflects red component light (hereinafter referred to as red light) out of white light emitted from the lamp 121a and transmits other color component light. The second dichroic mirror 123 selectively reflects green component light (hereinafter referred to as green light). Of the light transmitted through the first dichroic mirror 122, green light is selectively reflected by the second dichroic mirror 123 and guided to the green liquid crystal panel 127g. The remaining blue component light (hereinafter referred to as blue light) transmitted through the second dichroic mirror 123 is guided to the blue liquid crystal panel 127b by the second and third reflection mirrors 125 and 126. The red light reflected by the first dichroic mirror 122 is guided to the red liquid crystal panel 127 r by the first reflecting mirror 124.
[0005]
  The color lights modulated by the liquid crystal panels 127r, 127g, and 127b are combined by the dichroic prism 128 and emitted toward the projection lens 130.
[0006]
  At this time, the incident directions of the color lights modulated by the liquid crystal panels 127r, 127g, and 127b with respect to the dichroic prism 128 are set in consideration of the color reproducibility of the dichroic prism 128. That is, the light reflected by the dichroic prism 128 is S-polarized light and the transmitted light is P-polarized light.
[0007]
  Here, S-polarized light refers to linearly polarized light perpendicular to a plane in which the oscillation direction of the electric vector of light incident on the sample surface includes the normal of the sample surface and the normal of the wavefront that is the traveling direction of the light. P-polarized light is linearly polarized light in which the vibration direction of the electric vector of light incident on the sample surface is included in the incident surface (a surface including the normal line standing on the sample surface and the traveling direction of light).
[0008]
  Specifically, among the light incident on the dichroic prism 128, the red light is set to S polarization with respect to the bonding surface 128x. That is, a component having a polarization direction perpendicular to the xz plane is reflected by the bonding surface 128x. The green light is set to P-polarized light with respect to the bonding surfaces 128x and 128y. That is, a component having a polarization direction parallel to the xz plane is transmitted through the joint surfaces 128x and 128y. Further, the blue light is set to S polarization with respect to the bonding surface 128y. That is, a component having a polarization direction perpendicular to the xz plane is reflected by the bonding surface 128y. In this manner, red light, green light, and blue light are color-synthesized.
[0009]
  Then, the color-combined video light is irradiated from the projection lens 130 to the back side of the screen 170 via the reflection mirror 160.
[0010]
  In recent years, an apparatus for irradiating image light obliquely to the screen 170 has been proposed for the purpose of reducing the thickness of the rear projection display apparatus having such a configuration. When the projection unit 120 described above is used for such oblique projection, the polarization direction of the projected image light with respect to the screen 170 is orthogonal to the polarization direction with respect to the dichroic prism 128. That is, the red component is P-polarized light, the green component is S-polarized light, and the blue component is P-polarized light.
[0011]
  By the way, irradiating the screen 170 with the image light obliquely causes the light to enter the acrylic resin from the air with a certain incident angle from the vertical incidence. FIG. 6 is a graph showing the reflectance characteristics of light incident on the acrylic resin from the air. As shown in FIG. 6, when image light is applied to the screen 170 from an oblique direction, the light component P-polarized with respect to the screen 170 has a reduced reflectance on the screen 170, whereas On the other hand, the light component S-polarized light tends to increase the reflectance at the screen 170.
[0012]
  Moreover, the graph shown in FIG. 8 represents the human specific luminous efficiency characteristic. As shown in FIG. 8, the human eye's specific luminous sensitivity is the highest in the vicinity of a wavelength of 555 nm corresponding to green, and tends to feel green light brighter than red light and blue light.
[0013]
  For this reason, when oblique projection is performed using the conventional projection unit 120, the reflectance of the brightest green light on the screen 170 is increased, and not only the brightness is lowered as a whole, but also the image quality due to reflection of reflected light is increased. There was a problem of causing a drop.
[0014]
[Problems to be solved by the invention]
  By the way, irradiating the screen 170 with the image light obliquely causes the light to enter the acrylic resin from the air with a certain incident angle from the vertical incidence. FIG. 6 is a graph showing the reflectance characteristics of light incident on the acrylic resin from the air. As shown in FIG. 6, when image light is applied to the screen 170 from an oblique direction, the light component P-polarized with respect to the screen 170 has a reduced reflectance on the screen 170, whereas On the other hand, the light component S-polarized light tends to increase the reflectance at the screen 170.
[0015]
  Moreover, the graph shown in FIG. 8 represents the human specific luminous efficiency characteristic. As shown in FIG. 8, the human eye's specific luminous sensitivity is the highest in the vicinity of a wavelength of 555 nm corresponding to green, and tends to feel green light brighter than red light and blue light.
[0016]
  For this reason, when oblique projection is performed using the conventional projection unit 120, the reflectance of the brightest green light on the screen 170 is increased, and not only the brightness is lowered as a whole, but also the image quality due to reflection of reflected light is increased. There was a problem of causing a drop.
[0017]
  The present invention has been made in view of such problems, and is a rear projection type capable of increasing the luminance and improving the image quality by improving the utilization efficiency of image light projected obliquely with respect to the screen. An object is to provide a display device.
[0018]
  One aspect of the present invention is a light source lamp, color separation means for separating light emitted from the light source lamp into red light, green light, and blue light, and a red liquid crystal panel that optically modulates the red light. A green liquid crystal panel for optically modulating the green light, a blue liquid crystal panel for optically modulating the blue light, and the red light and the green liquid crystal panel modulated by the red liquid crystal panel. A dichroic prism that combines the modulated green light and the blue light modulated by the blue liquid crystal panel; and a projection unit that projects the image light synthesized by the dichroic prism from an oblique direction with respect to the screen. In the rear projection display device, the dichroic prism reflects the red light toward the projection unit and transmits the green light toward the projection unit. A joining surface that has a joining surface and a joining surface that reflects the blue light toward the projection unit and transmits the green light toward the projection unit, and reflects the red light toward the projection unit. The junction surface that is irradiated with the red light in the S-polarization direction and reflects the blue light toward the projection means has the blue light in the S-polarization direction with respect to the junction surface. The joint surface that is irradiated and reflects the red light to the projection means side and the joint surface that reflects the blue light to the projection means side are irradiated with the green light in the P-polarization direction with respect to the joint surface, A narrow-band retardation plate that rotates the polarization direction of the green light is provided on the side from which the image light is emitted from the dichroic prism, and the narrow-band retardation plate is irradiated with the image light. In the direction of P-polarized light And summarized in that aligning the polarization direction of all of the image light.
[0019]
  Against the screenWhen projecting image light from an oblique direction, reflection on the screen is reduced by setting the polarization direction of the color components of all image light irradiated on the screen to the P-polarization direction component with respect to the surface irradiated with the screen. In addition, it is possible to increase the luminance and reduce the double image due to the reflected light reflected on the screen.
[0021]
[0022]
[0023]
[0024]
[0025]
[0026]
[0027]
[0028]
[0029]
[0030]
[0031]
[0032]
[0033]
[0034]
[0035]
[0036]
[0037]
[0038]
[0039]
[0040]
[0041]
  The present invention also provides:The maximum value i-max and the minimum value i-min of the angle formed between the normal line of the screen back surface and the principal ray of the image light irradiated on the screen back surface, and the P-polarization direction with respect to the surface irradiated with the screen What is necessary is just to comprise so that the angle (alpha) from which the reflectance with respect to the said screen back surface in the reflectance characteristic of the light used as a component may satisfy | fill i-min <(alpha) <i-max.
[0042]
  With this configuration,P-polarization direction component with respect to the illuminated surface of the screenIs irradiated on the back surface of the screen in a range including an angle α at which the reflectance to the screen is lowest with respect to the normal line on the back surface of the screen.
[0043]
  Also,The maximum value j-max and minimum value j-min of the angle formed between the normal of the screen surface and the principal ray of image light irradiated on the screen surface, and the P-polarization direction with respect to the surface irradiated with the screen What is necessary is just to comprise so that the angle (beta) in which the reflectance with respect to the said screen surface becomes the minimum in the reflectance characteristic of the light used as a component may satisfy | fill j-min <(beta) <j-max.
[0044]
  With this configuration,P-polarization direction component with respect to the illuminated surface of the screenThe screen surface is irradiated in a range including an angle β at which the reflectance on the back surface of the screen is lowest with respect to the normal line on the back surface of the screen.
[0045]
  Specifically, the screen includes a Fresnel lens, and the screen surface is an inclined surface of a ring-shaped protrusion in the Fresnel lens.
[0046]
[0047]
[0048]
[0049]
[0050]
[0051]
[0052]
[0053]
[0054]
[0055]
[0056]
[0057]
[0058]
[0059]
[0060]
[0061]
[0062]
DETAILED DESCRIPTION OF THE INVENTION
  The rear projection display according to the embodiment of the present invention will be described below with reference to the drawings. In the following description, a coordinate system is used in which the width direction of the rectangular screen 7 is the x axis, the height direction of the screen 7 is the y axis, and the direction perpendicular to the screen 7 is the z axis.
[0063]
  In this embodiment, FIGS. 1 and 2 show a schematic configuration of a rear projection display device, FIG. 1 is a cross-sectional view, and FIG. 2 is a front view. 3 and 4 show a schematic configuration of the projection unit in the rear projection display device of FIG. 1, FIG. 3 is a top view, and FIG. 4 is a side view thereof. FIG. 5 is an enlarged sectional view showing the configuration of the screen in the rear projection display device of FIG. 6 is a graph representing the reflectance characteristics of light incident on the acrylic resin from the air, FIG. 7 is a graph representing the reflectance characteristics of light incident on the acrylic resin from the air, and FIG. 8 represents the human relative luminous sensitivity characteristics. It is a graph.
[0064]
  As shown in FIG. 1, the rear projection display device in this example includes a projection unit 2 that generates image light, a screen 7 on which the image light is projected to form an image, and a projection unit 2 that emits the image light. First to fourth mirrors 3 to 6 for guiding image light to a screen 7 and a housing 1 for holding them together are provided.
[0065]
  The first to third mirrors 3 to 5 constitute an imaging system. The first mirror 3 has an aspherical concave shape, and the second and third mirrors 4 and 5 each have an aspherical convex shape. Astigmatism of image light is caused by the shape of each mirror of the imaging system. And aberrations such as coma are corrected and the image is enlarged. The image light emitted from the projection unit 2 is sequentially reflected by the first to third mirrors 3 to 5 and then irradiated to the fourth mirror 6 disposed on the back surface of the housing 1. The image light irradiated on the flat plate-like fourth mirror 6 is irradiated obliquely from below to the back surface of the screen 7 disposed in the front opening of the housing 1 to form an image.
[0066]
  As shown in FIG. 3, the projection unit 2 is a so-called three-plate type. The light source 21 includes a reflector 21b and a metal halide lamp 21a, and white light emitted from the light source 21 is separated into three colors by dichroic mirrors 22 and 23. The first dichroic mirror 22 selectively reflects red light out of white light emitted from the metal halide lamp 21a and transmits light of other color components. The second dichroic mirror 23 selectively reflects green light and transmits light of other color components.
[0067]
  The white light emitted from the metal halide lamp 21a is reflected by the reflector 21a, and after removing ultraviolet rays and infrared rays by a UV / IR filter (not shown), an angle of 45 degrees with respect to the first dichroic mirror 22 Irradiated with. The red light reflected by the first dichroic mirror 22 is guided by the first reflecting mirror 24 to the first liquid crystal panel 27r for red. The light transmitted through the first dichroic mirror 122 is applied to the second dichroic mirror 23 at an angle of 45 degrees. Of the light transmitted through the first dichroic mirror 122, the green light is selectively reflected by the second dichroic mirror 123 and guided to the second liquid crystal panel 127g for green. The remaining blue light transmitted through the second dichroic mirror 23 is guided to the third liquid crystal panel 27b for blue by the second and third reflection mirrors 25 and 26. Further, the blue light transmitted through the second dichroic mirror 23 is sequentially reflected by the second and third mirrors 25 and 26, and then irradiated to the third liquid crystal panel 27b.
[0068]
  The red light guided to the first liquid crystal panel 27r for red is optically modulated in accordance with red video information and then incident on the main surface 28r of the dichroic prism 28 for color synthesis. Further, the green light guided to the second liquid crystal panel 27g for green is optically modulated according to the green video information by the second liquid crystal panel 27g, and then the dichroic prism for color synthesis. 28 is incident on the main surface 28g. On the other hand, the blue light guided to the third liquid crystal panel 27b for blue is optically modulated in accordance with the blue video information by the third liquid crystal panel 27b, and then the dichroic prism 28 for color synthesis. Is incident on the main surface 28b.
[0069]
  Of the red light incident from the main surface 28r of the dichroic prism 28, S-polarized light, that is, a component having a polarization direction perpendicular to the xz plane, is reflected by the joint surface 28x with respect to the joint surface 28x. In addition, among the green light incident from the main surface 28g of the dichroic prism 28, P-polarized light with respect to the joint surfaces 28x and 28y, that is, a component having a polarization direction parallel to the xz plane is transmitted through the joint surfaces 28x and 28y. . Further, of the blue light incident from the main surface 28b of the dichroic prism 28, S-polarized light, that is, a component having a polarization direction perpendicular to the xz plane, is reflected by the joint surface 28y with respect to the joint surface 28y.
[0070]
  As described above, the dichroic prism 28 synthesizes each color light optically modulated in accordance with the color information of each color in each liquid crystal panel 27r, 27g, 27b. The color-combined video light is emitted from the main surface 28c of the dichroic prism 28, and the polarization direction is rotated by 90 degrees by the λ / 2 phase difference plate 29, and the light is given to the imaging system.
[0071]
  In the image light emitted from the main surface 28c of the dichroic prism 28, red light is S-polarized with respect to the joint surface 28x, green light is P-polarized with respect to the joint surfaces 28x and 28y, and blue light is with respect to the joint surface 28y. S-polarized light. Then, the polarization direction is rotated by 90 degrees by the λ / 2 phase difference plate 29, respectively, so that red light is P-polarized with respect to the joint surface 28x, green light is S-polarized light with respect to the joint surfaces 28x and 28y, and blue light is emitted. P-polarized light is applied to the bonding surface 28y.
[0072]
  As shown in FIG. 1, the image light transmitted through the λ / 2 phase difference plate 29 is sequentially reflected by the first to third mirrors 3 to 5 constituting the imaging system, and then the rear surface of the housing 1. The fourth mirror 6 arranged in the position is irradiated. Aberrations such as astigmatism and coma in the image light are corrected and the image is enlarged by the shape of each mirror in the imaging system.
[0073]
  Then, the image light applied to the flat plate-like fourth mirror 6 is applied to the back surface of the screen 7 obliquely from below. At this time, the image light irradiated on the back surface of the screen 7 has red light in the S-polarized direction with respect to the screen 7, that is, a polarization direction perpendicular to the yz plane. The green light is P-polarized with respect to the screen 7, that is, a polarization direction parallel to the yz plane. Further, the blue light is S-polarized with respect to the screen 7, that is, a polarization direction perpendicular to the yz plane. The yz plane corresponds to a vertical cross section of the screen 7.
[0074]
  As shown in FIG. 5, the screen 7 includes a Fresnel lens screen 71 made of acrylic resin and a lenticular lens screen 72, and the image light reflected by the fourth mirror 6 is reflected on the Fresnel lens screen 71. The back surface 71a is irradiated.
[0075]
  At this time, the angle i formed between the normal A to the back surface 71a of the Fresnel lens screen 71 and the principal ray of the image light applied thereto is the upper corners C1 and C2 of the Fresnel lens screen 71 (see FIG. 1). The maximum i-max is reached, and the minimum i-min is obtained at the lower end central portion C3 (see FIG. 1). Here, the first to fourth mirrors 3 to 6 are designed so that i-max is 58.27 degrees and i-min is 32.27 degrees.
[0076]
  FIG. 6 is a graph showing the reflectance characteristics of light incident on the acrylic resin from the air. Here, the refractive index of air is 1.00, and the refractive index of acrylic resin is 1.492. When the image light is irradiated obliquely onto the screen 170, the light is incident from the air with an incident angle on the acrylic resin.
[0077]
  By the way, as shown in FIG. 6, the reflectance of the light irradiated to the acrylic resin which comprises the Fresnel lens screen 71 from the air is the light irradiated to an acrylic resin, and the acrylic resin in the part irradiated with the light. It changes according to the angle formed with the normal line, that is, the incident angle θ1. As indicated by a broken line in the figure, the reflectance characteristic S of light in the polarization direction perpendicular to the plane including the light irradiated to the acrylic resin and the normal line of the acrylic resin in the portion irradiated with the light is represented by an angle θ1. As the value increases, the reflectance tends to increase. On the other hand, as shown by the solid line, the reflectance characteristic P of the light in the polarization direction parallel to the plane including the light irradiated to the acrylic resin and the normal line of the acrylic resin in the portion irradiated with the light is expressed as the angle The reflectance tends to decrease as θ1 approaches α, which takes a minimum value. The angle α at which the minimum value is obtained is an angle at which the P component of the reflected light becomes 0 and the reflected light becomes completely plane polarized light. The incident angle at such an angle is called a polarization angle. The polarization angle α is as shown in the following equation 1 when the refractive indexes on both sides of the boundary are n1 and n2.
[0078]
    (Equation 1)
  tan α = n2 / n1
[0079]
  Specifically, the angle α when light is incident on the acrylic resin from the air is approximately 56 degrees from the above formula.
[0080]
  For this reason, of the image light irradiated on the back surface 71a of the Fresnel lens screen 71, the reflectance of the red light and blue light, which are S-polarized light with respect to the screen 7, on the back surface 71a of the Fresnel lens screen 71 is shown by a broken line in FIG. As shown in FIG. 4, the reflectance of the light irradiated in parallel with the normal A of the screen 7 is higher and the light use efficiency is reduced, but the image light irradiated on the back surface 71a of the Fresnel lens screen 71 The reflectance of green light, which is P-polarized light with respect to the screen 7, on the back surface 71 a of the Fresnel lens screen 71 is the reflectance of light irradiated parallel to the normal A of the screen 7, as shown by the solid line in FIG. 6. And the light utilization efficiency increases.
[0081]
  In general, it is known that green light greatly affects the brightness in human vision compared to red light and blue light. That is, the human eye feels the brightest light with a wavelength of 555 nm corresponding to green (high visibility). Visibility in each wavelength region with reference to the visibility for a wavelength of 555 nm corresponding to green is as shown in FIG. According to the figure, assuming that the visibility for green is 1, the visibility at a wavelength of 630 nm corresponding to red is about 0.265, and the visibility at a wavelength of 470 nm corresponding to blue is about 0.091.
[0082]
  As described above, when the image light is irradiated obliquely on the screen 7, since the visibility of the green light is significantly higher than that of the red light and the blue light, the red light and the blue light are S-polarized with respect to the screen 7. Therefore, it is possible to increase the luminance that is increased by setting the green light as P-polarized light with respect to the screen 7 and to increase the luminance as a whole. Further, with this increase in brightness, the amount of light reflected by the back surface 71a of the Fresnel lens screen 71 is reduced, so that double images due to reflection of reflected light can be reduced, and image quality can be improved. Become. Preferably, all color components may be P-polarized with respect to the screen 7.
[0083]
  In addition, since the angle i between the principal ray of the image light irradiated on the screen 7 and the normal A of the screen 7 is set to satisfy the following formula 2, the light utilization efficiency of the P-polarized component itself is improved. Therefore, it is possible to further increase the brightness.
[0084]
    (Equation 2)
i-min <α <i-max
[0085]
  Next, the image light transmitted through the back surface 71a of the Fresnel lens screen 71 is refracted at an angle k1 according to Snell's law on the back surface 71a, and then a projection formed in a ring shape on the exit side of the Fresnel lens screen 71. The inclined surface 71b is irradiated.
[0086]
  At this time, the angle j formed between the normal B to the inclined surface 71b of the Fresnel lens screen 71 and the principal ray of the image light irradiated thereon is the maximum j− on the inclined surface 71b of each protrusion of the Fresnel lens screen 71. The angle of the inclined surface 71b is set to be an angle of max and minimum j-min. Here, the inclination angle τ of each inclined surface 71b is set so that j-max is 38.36 degrees and j-min is 22.57 degrees.
[0087]
  By the way, as shown in FIG. 7, the reflectance of light emitted from the acrylic resin constituting the Fresnel lens 71 into the air is normal to the acrylic resin at the portion where the light travels inside the acrylic resin and the light is emitted. It changes in accordance with the angle θ2 formed by. As indicated by a broken line in the figure, the reflectance characteristic S ′ of the light in the polarization direction perpendicular to the plane including the light traveling in the acrylic resin and the normal line of the acrylic resin in the portion where the light is emitted is expressed by the angle θ2 As the value increases, the reflectance tends to increase. On the other hand, as indicated by the solid line in the figure, the reflectance characteristic P ′ of the light in the polarization direction parallel to the plane including the light traveling in the acrylic resin and the normal line of the acrylic resin in the portion where the light is emitted. Indicates a tendency for the reflectance to decrease as the angle θ2 approaches the polarization angle β at which the angle θ2 takes a minimum value. Specifically, the angle β when light is emitted from the acrylic resin into the air is approximately 34 degrees from Equation 1 above.
[0088]
  For this reason, out of the image light irradiated on the inclined surface 71b of the ring-shaped protrusion on the emission side of the Fresnel lens screen 71, the reflectance of the S-polarized red light and blue light on the inclined surface 71b of the screen 7 is high. As shown by the broken line S ′ in FIG. 7, the reflectance of light irradiated in parallel with the normal B of the inclined surface 71 b is higher and the light use efficiency is lowered, but the inclined surface 71 b is irradiated. Of the image light, the reflectance of green light, which is P-polarized light, with respect to the screen 7 on the inclined surface 71b is light that is irradiated in parallel with the normal B of the inclined surface 71b, as indicated by the solid line P ′ in FIG. Therefore, the light utilization efficiency increases.
[0089]
  Therefore, as in the case where the image light is irradiated from the air to the back surface 71a of the Fresnel lens screen 71, the green light is emitted from the luminance which is reduced by the red light and the blue light being S-polarized with respect to the screen 7. By increasing the luminance of the screen 7 by using the P-polarized light, it is possible to increase the luminance, and it is possible to increase the luminance as a whole. Furthermore, since the reflected light on the inclined surface 71b of the Fresnel lens screen 71 is reduced, the double image generated by the reflected light can be reduced, and the image quality can be improved. Preferably, all color components may be P-polarized light.
[0090]
  In addition, since the angle j formed by the principal ray of the image light irradiated on the inclined surface 71b of the screen 7 and the normal B of the inclined surface 71b is set to satisfy the following equation 3, the light of the P-polarized component itself The use efficiency can be improved, and it is possible to further increase the brightness.
[0091]
    (Equation 3)
j-min <β <j-max
[0092]
  The image light transmitted through the inclined surface 71b of the Fresnel lens screen 7 is refracted by the inclined surface 71b at an angle k2 according to Snell's law, and then irradiated to the lenticular lens screen 72 to form an image by its diffusion action. Is done.
[0093]
  In the present embodiment, the case where the image light is irradiated obliquely from below the screen 7 has been described. However, the image light may be irradiated from an oblique side of the screen 7. In this case, the green light may be adjusted so as to be P-polarized with respect to the screen 7, that is, the polarization direction parallel to the xz plane.
[0094]
  In the present embodiment, the case where the polarization direction of the green light is adjusted to be parallel to the yz plane has been described. Preferably, however, the principal ray of the image light and the image light are irradiated. It is better to adjust so as to be parallel to a plane including the normal line in the portion.
[0095]
  In this embodiment, the λ / 2 phase difference plate 29 is used to adjust the polarization direction of the green light so that it changes from the S polarization to the P polarization with respect to the screen 7. A narrow-band phase plate that selectively adjusts the screen 7 from S-polarized light to P-polarized light may be used. In this case, since the polarization directions of the red light and the blue light do not change, it is possible to adjust so that all the image light is P-polarized with respect to the screen 7.
[0096]
  Further, in the present embodiment, the imaging system is constituted by the first to third mirrors 3 to 5, but it goes without saying that the same effect can be obtained even in a lens system.
[0097]
【The invention's effect】
  According to the present invention, when irradiating image light obliquely to the screen,By making the polarization direction of the color components of all image light irradiated on the screen the P-polarization direction component with respect to the surface irradiated with the screen, reflection on the screen can be reduced and high brightness can be achieved. In addition, a double image due to reflection of reflected light on the screen can be reduced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a schematic configuration of a rear projection display device according to an embodiment of the present invention.
FIG. 2 is a front view of the same.
FIG. 3 is a top view illustrating a schematic configuration of a projection unit in the rear projection display device of FIG. 1;
FIG. 4 is a side view of the same.
5 is a partially enlarged cross-sectional view showing a schematic configuration of a screen in the rear projection display device of FIG. 1. FIG.
FIG. 6 is a graph showing the reflectance characteristics of light incident on an acrylic resin from the air.
FIG. 7 is a graph showing the reflection characteristics of light emitted from an acrylic resin into the air.
FIG. 8 is a graph showing a human specific luminous efficiency characteristic.
FIG. 9 is a cross-sectional view illustrating a schematic configuration of a conventional rear projection display device.
FIG. 10 is a top view illustrating a schematic configuration of a projection unit in the rear projection display device of FIG. 9;
[Explanation of symbols]
  1 housing
  2 Projection unit
  29 λ / 2 retardation plate
  3 First reflection mirror
  4 Second reflection mirror
  5 Third reflection mirror
  6 Fourth reflection mirror
  7 screens
  71 Fresnel lens screen
  72 Lenticular Lens Screen

Claims (1)

A light source lamp; color separation means for separating light emitted from the light source lamp into red light, green light, and blue light; a red liquid crystal panel that optically modulates the red light; and the green light optically. A green liquid crystal panel to modulate; a blue liquid crystal panel to optically modulate the blue light; the red light modulated by the red liquid crystal panel; the green light modulated by the green liquid crystal panel; A rear projection display device comprising: a dichroic prism that synthesizes the blue light modulated by a blue liquid crystal panel; and a projection unit that projects the image light synthesized by the dichroic prism from an oblique direction with respect to a screen. There,
The dichroic prism reflects the red light to the projection means side, transmits a green light to the projection means side, reflects the blue light to the projection means side, and reflects the green light. A joining surface that is transmissive to the projection means side;
The joint surface that reflects the red light toward the projection unit is irradiated with the red light in the S-polarization direction with respect to the joint surface.
The blue light in the S-polarized direction is irradiated to the bonding surface that reflects the blue light toward the projection unit,
The bonding surface that reflects the red light toward the projection unit and the bonding surface that reflects the blue light toward the projection unit are irradiated with the green light in the P-polarization direction with respect to the bonding surface.
On the side from which the image light is emitted from the dichroic prism, a narrow band phase plate that rotates the polarization direction of the green light is provided,
The rear projection display device, wherein the narrow-band phase difference plate aligns the polarization directions of all the image lights in the P-polarization direction with respect to the irradiation surface of the screen irradiated with the image light.

Images