JP2004252489A - Rear projection type display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rear projection type display device whose luminance is made higher by improving use efficiency of video light projected on a screen obliquely from below. <P>SOLUTION: The rear projection type display device is equipped with: a light source lamp; a color separating means of separating the light emitted by the light source lamp into a plurality of color components; a plurality of liquid crystal panels which optically modulate the respective color components separated by the color separating means; a color composing means of putting together the respective color components modulated by those liquid crystal panels; and a projecting means of projecting the video light composed by the color composing means on the screen 7 obliquely from below. The rear projection type display device selectively makes, out of the video light composed by the color composing means, a color component having a polarizing direction orthogonal to a vertical cross section of the screen 7 of the video light composited by the color compositing means into P-polarized light relative to the screen by using a narrow-band phase difference plate. Consequently, reflection on the screen 7 can be reduced. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a rear-projection display device that projects image light obliquely to the rear surface of a screen and observes an image from the front surface of the screen.

  9 and 10 show an example of a conventional rear projection display device. FIG. 9 is a 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 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 will be described.

  As shown in FIG. 9, the rear projection display device includes a housing 110 and a projection unit 120 disposed therein. A projection lens 130 is arranged at a light exit of the projection unit 120. A reflection mirror 160 is disposed on the rear surface inside the housing 110, and a transmissive diffusion screen 170 is disposed on the front surface of the housing 110. Then, the image light that is 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 side of the diffusion screen 170, and the image is projected from the front side of the diffusion screen 170. To be observed.

  Further, as shown in FIG. 10, the projection unit 120 includes a white light source 121 including a lamp 121a and a reflector 121b, and the white light emitted from the white light source 121 is converted into three colors by dichroic mirrors 122 and 123. Is separated into The first dichroic mirror 122 selectively reflects red component light (hereinafter, referred to as red light) of the white light emitted from the lamp 121a, and transmits other color component lights. 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 liquid crystal panel 127g for green. 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 liquid crystal panel 127r for red by the first reflection mirror 124.

  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.

  At this time, the incident direction of each color light modulated by each of the liquid crystal panels 127r, 127g, and 127b to the dichroic prism 128 is 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, and the light transmitted is P-polarized.

  Here, the S-polarized light refers to linearly polarized light perpendicular to a plane in which the vibration direction of the electric vector of the light incident on the sample surface includes the normal to the sample surface and the normal to the wavefront that is the traveling direction of the light. The P-polarized light refers to linearly polarized light in which the direction of vibration of the electric vector of light incident on the sample surface is included in the incident surface (a plane including the normal to the sample surface and the traveling direction of the light).

Specifically, red light of the light incident on the dichroic prism 128 is set to S-polarized light with respect to the joint 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 passes through the bonding surfaces 128x and 128y. Further, the blue light is set to S-polarized light 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. Thus, the red light, the green light and the blue light are color-combined.

  Then, the color-combined image light is emitted from the projection lens 130 to the back side of the screen 170 via the reflection mirror 160.

  In recent years, a device that irradiates the screen 170 with image light obliquely has been proposed in order to reduce the thickness of the rear projection display device having such a configuration. When the above-described projection unit 120 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.

  By irradiating the screen 170 with image light obliquely, light is incident on the acrylic resin from the air at a certain incident angle from 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 the screen 170 is irradiated with image light obliquely, light of a component that becomes P-polarized light with respect to the screen 170 has a reduced reflectance on the screen 170, whereas On the other hand, the component light that becomes S-polarized light tends to increase the reflectance on the screen 170.

  The graph shown in FIG. 8 represents the human's relative luminous efficiency characteristics. As shown in FIG. 8, the relative luminous efficiency of the human eye is highest around a wavelength of 555 nm corresponding to green, and tends to feel green light brighter than red light and blue light.

  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 increases, and not only does the overall brightness decrease, but also the image quality due to the reflection of reflected light. There has been a problem that it causes a decrease.

  The present invention has been made in view of such a problem, and a rear projection type that can achieve high luminance and image quality by improving the utilization efficiency of video light projected obliquely to a screen. It is an object to provide a display device.

  The present invention relates to a light source lamp, a color separation unit that separates light emitted from the light source lamp into a plurality of color components, and a plurality of liquid crystal panels that perform optical modulation on each color light separated by the color separation unit. A color synthesizing unit for synthesizing each color light modulated by the liquid crystal panel; and a projection unit for projecting the image light color-synthesized by the color synthesizing unit onto the screen from obliquely above or below. And adjusting a color component in a polarization direction orthogonal to the vertical section of the screen in the image light combined by the color combining means to be selectively parallel to the vertical section of the screen by a narrow band retarder. The polarization directions of all the color components of the image light applied to the screen are parallel to a vertical section of the screen.

  When projecting image light obliquely from above or below the screen, the angle between the principal ray of light incident on the screen and the normal to the screen is greater in the vertical direction than in the horizontal direction. For this reason, by making the polarization direction of the green component of the image light having high relative luminous efficiency to the human eye parallel to the vertical cross section of the screen, the amount of light lost by reflecting the image light to the back surface of the screen is reduced. .

  Specifically, of the image light combined by the color combining means, the color component in the polarization direction orthogonal to the vertical section of the screen is selectively made parallel to the vertical section of the screen by the narrow-band retarder. It is characterized by comprising a polarization direction adjusting means for making an adjustment as needed.

  With such a configuration, the color component in the polarization direction orthogonal to the vertical section of the screen in the image light combined by the color combining means is selectively parallel to the vertical section of the screen. Adjusted.

  Further, the present invention provides a light source lamp, a color separation unit for separating light emitted from the light source lamp into a plurality of color components, and a plurality of liquid crystals for optically modulating each color light separated by the color separation unit. A panel, a color synthesizing means for synthesizing each color light modulated by these liquid crystal panels, and a projection means for projecting the image light color-synthesized by the synthesizing means from an oblique side to a screen, and Of the image light synthesized by the synthesizing means, the color component in the polarization direction orthogonal to the horizontal cross section of the screen is adjusted by a narrow band retarder to be selectively parallel to the horizontal cross section of the screen, The polarization directions of all color components of the image light applied to the screen are parallel to the horizontal cross section of the screen.

  When projecting image light from an oblique side to the screen, the angle between the principal ray of light incident on the screen and the normal to the screen is greater in the horizontal direction than in the vertical direction. For this reason, by making the polarization direction of the green component of the image light, which has high relative luminous efficiency to the human eye, parallel to the horizontal cross section of the screen, the amount of light that is lost by reflecting the image light to the back surface of the screen is reduced. .

  Specifically, of the image light combined by the color combining means, the color component in the polarization direction orthogonal to the horizontal section of the screen is selectively made parallel to the horizontal section of the screen by the narrow band retarder. It is characterized by comprising a polarization direction adjusting means for making an adjustment as needed.

  With such a configuration, of the image light synthesized by the color synthesizing means, the color component in the polarization direction orthogonal to the horizontal section of the screen is selectively parallel to the horizontal section of the screen. Adjusted.

  In addition, the present invention provides a light source lamp, a color separation unit that separates light emitted from the light source lamp into a plurality of color components, and a plurality of liquid crystal panels that perform optical modulation on each color light separated by the separation unit. And a color combining means for combining the respective color lights modulated by the liquid crystal panel, and a projection means for projecting the image light combined by the color combining means onto the screen from an oblique direction. A display device, wherein a polarization direction of at least a green component of image light emitted to the screen is parallel to a plane including the image light emitted to the screen and a normal to the screen. And

  When projecting image light obliquely to the screen, the angle between the principal ray of light incident on the screen and the screen normal is the maximum in a plane that includes the image light irradiated on the screen and the screen normal. It becomes. Therefore, the polarization direction of the green component of the image light, which has a high relative luminous efficiency to the human eye, is parallel to a plane including the image light irradiated on the screen and the normal to the screen, so that the image light can be reflected on the rear surface of the screen. The amount of light reflected and lost is reduced.

  Specifically, polarization direction adjustment for adjusting the polarization direction of at least the green component of the image light applied to the screen so as to be parallel to a plane including the image light applied to the screen and the normal to the screen. Means is provided.

  With such a configuration, if the green component of the image light synthesized by the color synthesizing unit is not parallel to a plane including the image light irradiated on the screen and the normal of the screen, the polarization The direction is adjusted by the direction adjusting means so as to be parallel to a plane including the image light irradiated on the screen and the normal line of the screen.

  Preferably, the polarization directions of all the color components of the image light applied to the screen should be parallel to the horizontal section of the screen.

  Specifically, of the image light combined by the color combining means, a color component in a polarization direction orthogonal to a plane including the image light irradiated on the screen and the screen normal is selectively parallel to the plane. A polarization direction adjusting means for adjusting the polarization direction.

  With such a configuration, of the image light synthesized by the color synthesizing means, a color component in a polarization direction orthogonal to a plane including the image light applied to the screen and the normal to the screen is selectively formed. The adjustment is made so as to be parallel to a plane including the image light irradiated on the screen and the normal line of the screen.

  Specifically, the polarization direction adjusting means is formed of a phase difference plate.

  Further, the projection means includes a plurality of aspherical mirrors that function as lenses.

  ADVANTAGE OF THE INVENTION According to this invention, when irradiating image light obliquely to a screen, at least the green component is made into P-polarized light with respect to a screen, the reflection in a screen can be reduced and high luminance is achieved. In addition to this, double images due to reflection of reflected light on the screen can be reduced, and image quality can be improved.

  A rear projection display according to an 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.

  In this embodiment, FIGS. 1 and 2 show a schematic configuration of a rear projection display device. FIG. 1 is a sectional view, and FIG. 2 is a front view. 3 and 4 show a schematic configuration of a projection unit in the rear projection type display device shown in FIG. 1. FIG. 3 is a top view and FIG. 4 is a side view of the same. FIG. 5 is an enlarged cross-sectional view illustrating a configuration of a screen in the rear projection display device of FIG. FIG. 6 is a graph showing a reflectance characteristic of light incident on the acrylic resin from the air, FIG. 7 is a graph showing a reflection characteristic of light incident on the acrylic resin from the air, and FIG. It is a graph.

  As shown in FIG. 1, the rear projection display device in the present example has a projection unit 2 that generates image light, a screen 7 on which the image light is projected to form an image, and a light that is emitted from the projection unit 2. The apparatus includes first to fourth mirrors 3 to 6 for guiding image light to a screen 7 and a housing 1 for integrally holding these.

  The first to third mirrors 3 to 5 constitute an imaging system. The first mirror 3 has an aspheric concave shape, the second and third mirrors 4 and 5 each have an aspheric convex shape, and the astigmatism of the image light depends on the shape of each mirror of the imaging system. Aberrations such as and aberration are corrected, and the image is enlarged. Then, the image light emitted from the projection unit 2 is sequentially reflected by the first to third mirrors 3 to 5, and then is applied to the fourth mirror 6 arranged on the back surface of the housing 1. The image light applied to the flat fourth mirror 6 is applied obliquely from below to the back surface of the screen 7 arranged in the front opening of the housing 1 to form an image.

  As shown in FIG. 3, the projection unit 2 is a so-called three-panel 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 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 other color components.

The white light emitted from the metal halide lamp 21a is reflected by the reflector 21a, and the UV / IR filter (not shown) removes the ultraviolet light and the infrared light. Irradiated with The red light reflected by the first dichroic mirror 22 is guided by the first reflection 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, 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 applied to the third liquid crystal panel 27b.

  The red light guided to the first liquid crystal panel 27r for red is subjected to optical modulation according to the red image information, and then enters the main surface 28r of the dichroic prism 28 for color synthesis. The green light guided to the second liquid crystal panel 27g for green is subjected to optical modulation according to green image information by the second liquid crystal panel 27g, and then to a dichroic prism for color synthesis. The light is incident on a 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. To the main surface 28b.

  Then, 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 bonding surface 28x with respect to the bonding surface 28x. Also, of the green light incident from the main surface 28g of the dichroic prism 28, P-polarized light, that is, a component having a polarization direction parallel to the xz plane is transmitted through the bonding surfaces 28x and 28y with respect to the bonding surfaces 28x and 28y. . Further, of the blue light incident from the main surface 28b of the dichroic prism 28, a component having S polarization, that is, a component having a polarization direction perpendicular to the xz plane, is reflected by the bonding surface 28y with respect to the bonding surface 28y.

  As described above, the respective color lights optically modulated in accordance with the color information of the respective colors by the respective liquid crystal panels 27r, 27g, and 27b are color-synthesized by the dichroic prism 28. The color-combined image 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 retardation plate 29, and the light is given to the imaging system.

  Image light emitted from the main surface 28c of the dichroic prism 28 is such that red light is S-polarized with respect to the bonding surface 28x, green light is P-polarized with respect to the bonding surfaces 28x and 28y, and blue light is with respect to the bonding surface 28y. S-polarized light. Then, the polarization directions are rotated by 90 degrees by the λ / 2 retardation plate 29, and red light is P-polarized light with respect to the bonding surfaces 28x, green light is S-polarized light with respect to the bonding surfaces 28x and 28y, and blue light is P-polarized light is applied to the bonding surface 28y.

  As shown in FIG. 1, the image light transmitted through the λ / 2 phase difference plate 29 is sequentially reflected by first to third mirrors 3 to 5 constituting an image forming system, and then is reflected on the rear surface of the housing 1. Is irradiated on the fourth mirror 6 disposed at the second position. Aberrations such as astigmatism and coma of image light are corrected by the shape of each mirror of the imaging system, and an image is enlarged.

  Then, the image light applied to the flat fourth mirror 6 is applied to the back surface of the screen 7 from obliquely below. At this time, the image light applied to the back surface of the screen 7 is such that the red light is S-polarized with respect to the screen 7, that is, the polarization direction is perpendicular to the yz plane. In addition, the green light becomes P-polarized light with respect to the screen 7, that is, the polarization direction is parallel to the yz plane. Further, the blue light is S-polarized with respect to the screen 7, that is, the polarization direction is perpendicular to the yz plane. The yz plane corresponds to a vertical section of the screen 7.

  As shown in FIG. 5, the screen 7 includes a Fresnel lens screen 71 made of an acrylic resin and a lenticular lens screen 72, and the image light reflected by the fourth mirror 6 is applied to the Fresnel lens screen 71. Irradiated on the back surface 71a.

At this time, the angle i 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 at the upper corners C1 and C2 of the Fresnel lens screen 71 (see FIG. 1). It becomes the maximum i-max, and becomes the minimum i-min at the lower end center portion C3 (see FIG. 1). Here, the first to fourth mirrors 3 to 6 are designed such that i-max is 58.27 degrees and i-min is 32.27 degrees.

  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. Irradiating the screen 170 with image light obliquely causes light to enter the acrylic resin from the air at an incident angle.

  By the way, as shown in FIG. 6, the reflectance of the light radiated to the acrylic resin constituting the Fresnel lens screen 71 from the air is determined by the light radiated to the acrylic resin and the acrylic resin in the portion irradiated with the light. It changes according to the angle made with the normal, that is, the incident angle θ1. As shown by the dashed line in the figure, the reflectance characteristic S of the light in the polarization direction perpendicular to the plane including the light irradiated on the acrylic resin and the normal line of the acrylic resin in the part irradiated with the acrylic resin is represented by the angle θ1. Shows a tendency that the reflectance increases as the value increases. 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 on the acrylic resin and the normal line of the acrylic resin in the portion irradiated with the acrylic resin is represented by the angle The reflectivity tends to decrease as θ1 approaches the minimum value α. The angle α at which the minimum value is obtained is the angle at which the P component of the reflected light becomes 0 and the reflected light becomes perfect plane polarized light. The incident angle at such an angle is called a polarization angle. The polarization angle α is expressed by the following equation (1), where n1 and n2 are the refractive indices on both sides of the boundary.

(Equation 1)
tan α = n2 / n1

  Specifically, the angle α when light enters the acrylic resin from the air is approximately 56 degrees according to the above equation.

  For this reason, of the image light applied to the back surface 71a of the Fresnel lens screen 71, the reflectance of the back surface 71a of the Fresnel lens screen 71 of S-polarized red light and blue light with respect to the screen 7 is indicated by a broken line in FIG. As shown by, the reflectivity of light emitted in parallel with the normal A of the screen 7 becomes higher and the light use efficiency decreases, but the image light emitted to the back surface 71a of the Fresnel lens screen 71 The reflectance of the rear surface 71a of the Fresnel lens screen 71 of the P-polarized green light with respect to the screen 7 is the reflectance of the light radiated in parallel with the normal A of the screen 7 as shown by a solid line in FIG. And light utilization efficiency increases.

  In general, it is known that green light has a large effect on brightness in human vision as compared with red light and blue light. In other words, the human eye feels light having a wavelength of 555 nm corresponding to green as the brightest (high visibility). FIG. 8 shows the luminosity factor in each wavelength region based on the luminosity factor for the wavelength 555 nm corresponding to green. According to the figure, assuming that the visibility for green is 1, the visibility at a wavelength of 630 nm corresponding to red is approximately 0.265, and the visibility at a wavelength of 470 nm corresponding to blue is approximately 0.091.

As described above, when the screen 7 is irradiated with the image light obliquely, since the visibility of the green light is significantly higher than the red light and the blue light, the red light and the blue light are s-polarized to the screen 7. By increasing the green light to the P-polarized light with respect to the screen 7, the luminance that rises can be made larger than the luminance that falls as a result of the above, and the overall luminance can be increased. Further, with the increase in brightness, the back surface 7 of the Fresnel lens screen 71
The amount of light reflected at 1a is reduced, and a double image due to reflection of reflected light can be reduced, so that image quality can be improved. Preferably, all the color components need only be P-polarized light with respect to the screen 7.

  Further, since the angle i between the principal ray of the image light applied to the screen 7 and the normal A of the screen 7 is set so as to satisfy the following expression 2, the light use efficiency of the P-polarized light component itself is improved. It is possible to further increase the luminance.

(Equation 2)
i-min <α <i-max

  Next, the image light transmitted through the back surface 71a of the Fresnel lens screen 71 is refracted at the back surface 71a at an angle k1 according to Snell's law, and then formed into a ring-shaped projection on the emission side of the Fresnel lens screen 71. Is irradiated on the inclined surface 71b.

  At this time, the angle j between the normal line B to the inclined surface 71b of the Fresnel lens screen 71 and the principal ray of the image light applied thereto is j-max on the inclined surface 71b of each projection of the Fresnel lens screen 71. The angle of the inclined surface 71b is set so that the angle is max and the minimum is j-min. Here, the inclination angle τ of each inclined surface 71b is set such that j-max is 38.36 degrees and j-min is 22.57 degrees.

  By the way, as shown in FIG. 7, the reflectance of the light emitted from the acrylic resin constituting the Fresnel lens 71 into the air is, as shown in FIG. 7, the light traveling in the acrylic resin and the normal line of the acrylic resin in the portion where the light is emitted. And changes in accordance with the angle θ2 formed by As shown by the dashed 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 represented by the angle θ2. Shows a tendency that the reflectance increases as the value increases. On the other hand, as shown by a solid line in the figure, the reflectance characteristic P ′ of light in a polarization direction parallel to a plane including the light traveling in the acrylic resin and the normal line of the acrylic resin in a portion where the light is emitted is shown. Shows a tendency that the reflectance decreases as the angle θ2 approaches the polarization angle β at which it takes a minimum value. Specifically, when light is emitted from the acrylic resin to the air, the angle β is approximately 34 degrees from the above equation (1).

  For this reason, of the image light applied to the inclined surface 71 b 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, which are S-polarized light, on the inclined surface 71 b with respect to the screen 7 is reduced. As shown by a broken line S ′ in FIG. 7, the reflectance is higher than the reflectance of light irradiated in parallel with the normal B of the inclined surface 71b, and the light is emitted to the inclined surface 71b although the light use efficiency is reduced. Among the image light, the reflectance of the green light, which is P-polarized light, on the inclined surface 71b with respect to the screen 7 is the light irradiated in parallel with the normal B of the inclined surface 71b as shown by a solid line P 'in FIG. And the light use efficiency increases.

  Therefore, similar to the case where the image light is emitted from the air to the back surface 71a of the Fresnel lens screen 71, the green light is converted to the green light from the luminance that is reduced by converting the red light and the blue light to the S-polarized light with respect to the screen 7. By using P-polarized light with respect to the screen 7, the luminance that increases can be made larger, and it is possible to achieve higher luminance as a whole. Further, since the reflected light on the inclined surface 71b of the Fresnel lens screen 71 is reduced, a double image caused by the reflected light can be reduced, and the image quality can be improved. Preferably, all the color components need only be P-polarized light.

Further, since the angle j between the principal ray of the image light applied to the inclined surface 71b of the screen 7 and the normal B of the inclined surface 71b is set so as to satisfy the following expression 3, the light of the P-polarized component itself is set. Efficiency can be improved, and higher luminance can be achieved.

(Equation 3)
j-min <β <j-max

  Then, the image light transmitted through the inclined surface 71b of the Fresnel lens screen 7 is refracted on the inclined surface 71b at an angle k2 according to Snell's law, and is irradiated on the lenticular lens screen 72, and an image is formed by the diffusion action. Is done.

  Note that, in the present embodiment, a case has been described in which the image light is emitted obliquely below the screen 7, but the image light may be emitted obliquely from the screen 7. In this case, the green light may be adjusted so as to be P-polarized light, that is, a polarization direction parallel to the xz plane with respect to the screen 7.

  Further, in the present embodiment, the case where the polarization direction of the green light is adjusted so as to be parallel to the yz plane has been described, but preferably, the principal ray of the image light and the image light are irradiated. It is better to make adjustments so as to be parallel to a plane including the normal line at the part where the light is emitted.

  Further, in the present embodiment, the polarization direction of the green light is adjusted using the λ / 2 retardation plate 29 so that the polarization direction of the green light is changed from the S polarization to the P polarization with respect to the screen 7. A narrow-band retarder 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 all of the image light to be P-polarized light with respect to the screen 7.

  Furthermore, in the present embodiment, the image forming system is constituted by the first to third mirrors 3 to 5, but it is needless to say that the same effect can be obtained by using a lens system.

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. FIG. 4 is a side view of the same. FIG. 5 is a partially enlarged sectional view showing a schematic configuration of a screen in the rear projection display device of FIG. FIG. 6 is a graph showing the reflectance characteristics of light incident on the acrylic resin from the air. FIG. 7 is a graph showing a reflection characteristic of light emitted from the acrylic resin into the air. FIG. 8 is a graph showing the human's relative luminous efficiency characteristics. 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.

Explanation of reference numerals

REFERENCE SIGNS LIST 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 screen 71 Fresnel lens screen 72 lenticular lens screen

Claims (3)

A light source lamp, a color separation unit for separating light emitted from the light source lamp into a plurality of color components, a plurality of liquid crystal panels for optically modulating each color light separated by the color separation unit, and A color synthesizing means for synthesizing each color light modulated by the above, and a projection means for projecting the image light color-synthesized by the color synthesizing means on the screen from obliquely above or obliquely below,
Of the image light synthesized by the color synthesizing means, the color component in the polarization direction orthogonal to the vertical cross section of the screen is adjusted by a narrow band retarder to be selectively parallel to the vertical cross section of the screen, A rear-projection display device, wherein polarization directions of all color components of the image light applied to the screen are parallel to a vertical section of the screen. A light source lamp, a color separation unit for separating light emitted from the light source lamp into a plurality of color components, a plurality of liquid crystal panels for optically modulating each color light separated by the color separation unit, and A color synthesizing unit for synthesizing the respective color lights modulated by, and a projection unit for projecting the image light color-synthesized by the synthesizing unit to the screen from an oblique side,
Of the image light synthesized by the color synthesizing means, the color component in the polarization direction orthogonal to the horizontal cross section of the screen is adjusted by a narrow band retarder to be selectively parallel to the horizontal cross section of the screen, A rear projection display device, wherein the polarization directions of all color components of the image light applied to the screen are parallel to a horizontal section of the screen. The rear projection type display device according to claim 1, wherein the projection unit includes a plurality of aspherical mirrors that function as a lens.

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