JP2007025309A - Projection video display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection video display device, wherein a chromaticity value is improved by improving the conventional color separation unit. <P>SOLUTION: In the projection video display device, the color separation unit has an incident plate provided with an aperture to transmit the light from a light source and an integrator, and a color separation surface is arranged on the emitting side of the integrator so as to be nearly in parallel to the emitting surface of the integrator, and a plurality of dichroic mirrors to transmit only the color light of a prescribed wavelength region and to reflect the color light of the other wavelength region are included. Also, the first dichroic mirror is arranged on the emitting surface of the first polarization separating prism, the second dichroic mirrors are arranged on both surfaces of the first polarization separating prism and the second polarization separating prism, and the third dichroic mirror is arranged on the emitting surface of the second polarization separating prism. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a projection apparatus that projects an image on a screen using an image display element, for example, an optical unit such as a liquid crystal projector apparatus, a reflective image display projector apparatus, a projection type rear projection television, or a projection type image display. The present invention relates to a technique for scanning color light separated by a color separation unit on an image display element.

  Conventionally, after passing light from a white light source through an integrator means, a polarization beam splitter (hereinafter referred to as PBS), a collimator lens, a strip-shaped (band-shaped) R light using a plurality of dichroic mirrors, B Light and G light (hereinafter referred to as color bars) are separated, and each separated color light is irradiated to different places of the light valve at the same time using a rotating polyhedron, and each color light is strip-shaped. There is known a single-plate projection display apparatus in which the irradiation area is sequentially moved in a certain direction on the light valve (also referred to as “scan” or “scroll”). This type of technology is described in, for example, Japanese Patent Application Laid-Open No. 2004-170549 and US Patent Publication No. 2003/095213.

  In such a scanning (scrolling) projection display device, the location of the three strip-shaped illumination areas corresponding to each color light formed on the light valve is scrolled by the rotating polyhedron. For example, in the projection type display device disclosed in US Patent Publication No. 2003/095213, as shown in FIG. 1, strip-shaped three color lights are adjacent to each other using a color separator composed of a dichroic prism. In this way, scrolling is simultaneously performed by rotationally driving one lens array wheel. Further, in the scanning projection display device disclosed in Japanese Patent Application Laid-Open No. 2004-170549, as shown in FIGS. 1 and 3, the rotating polyhedrons arranged in the respective optical paths of the color-separated three-color lights are used. Each color light is scrolled individually.

US Patent Publication 2003/095213 JP 2004-170549 A

  In the technology of US Patent Publication No. 2003/095213, the size of each lens constituting the lens array wheel is comparable to that of a liquid crystal display element. If the lens array wheel is half the size in order to make it compact, it is necessary to double the angular velocity, and rotational driving becomes difficult.

  Further, in the technology disclosed in US Patent Publication No. 2003/095213, the color separation surface of the color separator is relative to the optical axis of the rod prism for uniformizing the light from the light source reflected by the elliptical mirror. It is arranged obliquely with respect to the optical axis of the illumination optical system. With this arrangement, the incident angle is included with a light ray angle greatly deviating from 45 degrees, and there is a problem that the overall wavelength separation characteristic for the entire light flux on the color separation surface deteriorates.

  In general, in an illumination optical system, a spatial spread in which a light beam that can be effectively handled exists can be expressed as a product of an area and a solid angle (Eometric: Extent). The product of the area and the solid angle is stored in the optical system. Here, consider the light beam incident on the rod prism from the light source. The substantially white light beam incident on the rod prism is condensed on the incident surface of the rod prism disposed in the vicinity of the second focal position of the elliptical mirror, and the condensing area of the incident light beam is small. The solid angle increases. That is, the angle of incident light with respect to the optical axis increases. The angle of this incident ray is almost conserved within the rod prism. Therefore, the light beam emitted from the rod prism to the color separator includes a light beam having an incident angle greatly deviated from 45 degrees with respect to the color separation surface of each dichroic prism constituting the color separator. .

  FIG. 4 schematically shows the color separation surface of the color prism and the light flux. As shown on the left side of FIG. 4 (1), when the range of the incident light beam angle θ formed with the optical axis increases, that is, when the light beam incident angle on the color separation surface (dichroic mirror surface) deviates more than 45 degrees, As shown in FIG. 4B, the overall wavelength separation characteristic for the entire light flux on the color separation surface deteriorates. Here, the deterioration of the wavelength characteristic means that the change of the transmittance with respect to the wavelength before and after the half-value wavelength where the transmittance is 50% cannot be made steep. For example, when blue and green are considered, blue and green cannot be separated at a specified wavelength, and there is a problem that part of blue is mixed with green, and conversely, part of green is mixed with blue.

Further, the color separator disclosed in US Patent Publication No. 2003/095213 does not consider the alignment of polarized light. Therefore,
Also in the technique disclosed in Japanese Patent Application Laid-Open No. 2004-170549, a dichroic mirror is used as a color separation unit and is arranged at 45 degrees with respect to the optical axis. As shown in FIG. 1, since the lens array is used as the integrator means for making the light quantity distribution uniform, the area of the light beam incident on the dichroic mirror is large, and the solid angle is reduced by the etendue described above. . Therefore, since the range of the incident angle of the light beam to the dichroic mirror is small, there is almost no deterioration of the wavelength separation characteristic. Therefore, in the technique disclosed in Japanese Patent Application Laid-Open No. 2004-170549, there is no problem of deterioration of wavelength separation characteristics in the dichroic mirror arranged at 45 degrees with respect to the optical axis. However, when a plurality of rotating polyhedrons are arranged, there is a problem that the projection type image display device becomes large due to the size of the rotating polyhedron, and the use of a normal lens array increases the luminous flux, and the rotating polyhedron. There is a problem that it becomes necessary to increase the size of the apparatus in accordance with the luminous flux, and the entire apparatus becomes large. Furthermore, when the relative positions of the three strip-shaped illumination areas are shifted, there are areas where a plurality of colored lights are irradiated simultaneously, or conversely, there are areas where none of the colored lights are irradiated. High precision control is required.

  Another object of the present invention is to improve light utilization efficiency in a color separation unit having a polarization conversion element.

  Another object of the present invention is to improve color separation characteristics and reduce color mixing in a projection display apparatus or color separation unit.

  According to the present invention, in the projection display apparatus, the color separation unit includes an incident plate provided with an opening that transmits light from a light source and an integrator, and is substantially parallel to the output surface of the integrator on the output side of the integrator. And a plurality of dichroic mirrors that transmit only colored light in a predetermined wavelength range and reflect colored light in other wavelength ranges.

  Also, a first dichroic mirror is disposed on the exit surface of the first polarization separation prism, a second dichroic mirror is disposed on both the exit surfaces of the first polarization separation prism and the second polarization separation prism, and the second A third dichroic mirror is disposed on the exit surface of the polarization separation prism.

  It is possible to provide a projection-type image display device that has excellent color separation performance and little color mixing.

  Hereinafter, the best mode of the present invention will be described with reference to the drawings. In each figure, elements having common functions are denoted by the same reference numerals, and description of elements once described is omitted.

  Hereinafter, the color separation unit according to the first embodiment and the projection type image display apparatus including the color separation unit and using one rotating polyhedron will be described with reference to FIGS. 1 to 3.

  FIG. 1 is a schematic configuration diagram of a color separation unit as a main part of the present embodiment, FIG. 2 is a schematic configuration diagram of a projection type video display apparatus according to the present embodiment, and FIG. 3 is a color separation according to an incident angle on a color separation surface. It is a figure explaining the difference in a characteristic.

  First, the configuration of the scanning projection display apparatus according to this embodiment will be described with reference to FIGS.

  In FIG. 2, the substantially white light beam emitted from the light source unit 1 composed of the light source 11 and the reflector 12 (in this figure, an elliptical reflector) is incident on the color separation unit 2 a disposed near the second focal position of the reflector 12. The light is focused and incident.

  As shown in FIG. 1, the color separation unit 2a includes, in order from the incident side, an incident aperture plate 22 having a total reflection surface 222 in an inner surface region other than the incident aperture 221 having an optical incident aperture 221; A wave plate 23, a light pipe 24, which is an integrator element that makes the light amount distribution uniform, a polarization conversion element 21 that aligns the polarization direction of the light flux from the light pipe 24 with a predetermined polarization direction, and light from the polarization conversion element 21 A dichroic mirror 26 that is a color separation element that separates the color bars into three strips of different color light (for example, R light, G light, and B light) arranged in the Y-axis direction (direction perpendicular to the paper surface of FIG. 2). Have.

  The polarization conversion element 21 includes a first polarizing prism 211 that transmits P-polarized light and reflects S-polarized light, and a second polarizing prism 212 that reflects S-polarized light. Further, in the color separation unit 2a of FIG. 1, the exit surface of the light pipe 24 and the entrance surface of the first polarizing prism 211 have substantially the same area. Alternatively, the light emitted from the emission surface of the light pipe 24 first enters the first polarizing prism 211 first.

  The light beam, which is substantially white natural light incident on the optical incident aperture 221 of the incident aperture plate 22 from the light source unit 1, passes through the quarter-wave plate 23, but in the case of natural light, it remains natural light even after passing through. is there. The light flux that has passed through the quarter-wave plate 23 is repeatedly reflected on the side surface of the light pipe 24, whereby the light quantity distribution is made uniform. Then, the light beam made uniform by the light pipe 24 enters the polarization conversion element 21, and its polarization state is aligned with a predetermined polarization state (here, P-polarized light).

  The polarization conversion element 21 includes a first polarization separation prism 211 and a second polarization separation prism 212 arranged in the Y-axis direction, and a half-wave plate 213. The first polarization separation prism 211 is arranged on the side where the light beam from the light pipe 24 is incident, and the second polarization separation prism 212 is on the negative direction side of the Y axis of the first polarization separation prism 211 (lower side in FIG. 1). Has been placed. The half-wave plate 213 is provided on the emission side of the second polarization separation prism 212a via the dichroic mirror 26.

  Among the light beams incident on the polarization conversion element 21 from the light pipe 24, the P-polarized light beam is transmitted through the first polarization separation prism 211, and the S-polarized light beam is reflected by the first polarization separation prism 211 to be polarized. To separate. The reflected S-polarized light is reflected again by the second polarization separation prism 212, changes the traveling direction to the previously separated P-polarized light direction (Z-axis direction), and passes through the half-wave plate 213. By passing through the half-wave plate 213, S-polarized light is converted to P-polarized light, so that all light is converted to P-polarized light. The P-polarized light referred to here is P-polarized light separated by a polarization separation surface having a normal line in the YZ plane. For the polarization separation surfaces of the first PBS 51 and the second PBS 52 having a normal line in the XZ plane of FIG. S-polarized light. Details of color separation and light recycling (reuse of reflected light) by the dichroic mirror 26 will be described later with reference to FIG.

  The color bar of the three separated color lights (polarization state is S polarization) is further improved in purity of the S polarization state by the polarizing plate 81 that transmits the S polarization through the reduction optical system 31 and the optical path bending mirror 32. , Enters the first PBS 51. The S-polarized light beam (color bar) incident on the first PBS 51 is reflected by the polarization separation surface and travels toward the rotating polyhedron 4. The S-polarized light beam emitted from the first PBS 51 passes through the quarter-wave plate 82, is converted into circularly polarized light, and enters the rotating polyhedron 4 via the reduction optical system 33. In the process, the color bars of the three color lights formed on the exit surface S25 of the color prism 25 are mapped by the reduction optical systems 31 and 33 in the space before the rotating polyhedron 4 to form a space image (not shown). Is done.

  This aerial image is reflected by the reflecting surface 41 on the surface of the rotating polyhedron 4 and turns the optical path. By passing through the quarter-wave plate 82 again, the circularly polarized light is converted to P-polarized light, so that it passes through the first PBS 51 this time. The light beam transmitted through the first PBS 51 is converted into S-polarized light by the half-wave plate 83. Then, the S-polarized light beam incident on the second PBS 52 is reflected by the polarization separation surface and enters the video display element 6. In this process, the aerial image formed in the space in front of the rotating polyhedron 4 forms a specular image (not shown) on the reflecting surface 41 of the rotating polyhedron 4, and the specular image is formed by the magnifying optical system 33 (here, the light beam). Since the direction is reversed, it functions as a magnifying optical system) and is mapped onto the video display element 6.

  Although the reduction optical system and the enlargement optical system have been described here, there is no problem in the mapping relationship even when the enlargement optical system and the reduction optical system are combined, but by using the combination of the reduction optical system and the enlargement optical system, a rotating polyhedron Since the aerial image formed in the vicinity of the four reflecting surfaces 41 can be reduced, there is an advantage that the rotating polyhedron 4 can be reduced.

  The light beam reflected by each pixel of the image display element 6 is converted into P-polarized light when the voltage to each pixel is ON. This time, the light beam is transmitted through the second PBS 52 and screened by the projection lens 7 (not shown). The projection is enlarged. When the voltage for each pixel is OFF, the polarization state is S-polarized light, which is reflected again by the polarization plane of the second PBS 52, and the light beam is not projected on the screen or the like. Reference numeral 84 denotes a polarizing plate that transmits P-polarized light.

  Here, the outline of the scanning action by the rotating polyhedron 4 will be described below. When an object (aerial image) is placed in front of the reflecting surface 41, a mirror image (not shown) is formed on the back side of the reflecting surface 41 at the same distance as the distance from the reflecting surface 41 to the object. By the way, since the reflecting surface 41 is disposed on the surface of the rotating polyhedron 4, the angle of the reflecting surface 41 is changed by the rotation of the rotating polyhedron 4. For example, when the reflecting surface 41 rotates by θ, the reflected light changes by 2θ by twice that amount. At this time, the reflected light overlaps with the emitted light as if it were emitted from different positions in the specular image. Therefore, if the angle of the reflection surface 41 is continuously changed, continuous light rays are emitted from different positions of the specular image. That is, by changing the angle of the reflecting surface 41, light scanning (scrolling) can be realized.

  Next, the color separation action by the dichroic mirror 26 will be described with reference to FIG. The dichroic mirror 26 may be composed of a plurality of dichroic mirrors, or may be composed of one dichroic mirror having a plurality of types of separation surfaces. In the present embodiment, a description will be given assuming that a plurality of types of dichroic mirrors are used. That is, the dichroic mirror 26 includes a red dichroic mirror 261 that transmits only red light (R light) and reflects other color light, and a blue dichroic mirror 262 that transmits only blue light (B light) and reflects other color light. And a green dichroic mirror 263 that transmits only green light (G light) and reflects other color light. The dichroic mirror 26 is disposed on the exit surface S21 of the first polarization separation prism 211 and the second polarization separation prism 212, and the blue dichroic mirror 262 is disposed in a central region obtained by dividing the exit surface S21 into approximately three parts in the Y-axis direction. The red dichroic mirror 261 is located in the end region of the first polarization separation prism 211 (upper side of the blue dichroic mirror 262 in FIG. 1), and the end region of the second polarization separation prism 212 (blue dichroic mirror in the view of FIG. 1). A green dichroic mirror 263 is arranged on the lower side of H.262.

  Of the white light that has passed through the light pipe 24 and entered the polarization conversion element 21, the P-polarized light beam passes through the first polarization separation prism 211. The P-polarized red light reaching the red dichroic mirror 261 disposed on the exit surface of the first polarization separation prism 211 and the P-polarized blue light reaching the blue dichroic mirror 262 are respectively red dichroic mirror 261 and blue dichroic mirror 261. The light passes through the quick mirror 262. On the other hand, among the P-polarized light, green light, red light reaching the blue dichroic mirror 262, and blue light reaching the red dichroic mirror 261 are reflected by the dichroic mirror 26, respectively. The reflected light again passes through the first polarization separation prism 211, passes through the light pipe 24, passes through the quarter-wave plate 23, and is reflected again by the total reflection surface 222 of the incident aperture plate 22. Then, by passing through the quarter-wave plate 23 again, the previous P-polarized light is converted to S-polarized light, and enters the polarization conversion element 21 through the light pipe 24.

  The S-polarized light beam incident on the polarization conversion element 21 is first reflected by the first polarization separation prism 211 and the second polarization separation prism 212. Further, the S-polarized blue light reaching the blue dichroic mirror 262 and the S-polarized green light reaching the green dichroic mirror 263 are transmitted through the blue dichroic mirror 262 and the green dichroic mirror 263, respectively. The S-polarized red light, the green light reaching the blue dichroic mirror 262, and the blue light reaching the green dichroic mirror 263 are reflected by the dichroic mirror 26, respectively. The reflected light is reflected again by the second polarization separation prism 212 and the first polarization separation prism 211, passes through the light pipe 24, passes through the ¼ wavelength plate 23, and is further reflected by the total reflection surface 222 of the incident aperture plate 22. . Then, by passing through the quarter wavelength plate 23 again, the previous S-polarized light is converted to P-polarized light.

  Thus, each color light that has not passed through the dichroic mirror 26 is repeatedly reflected between the dichroic mirror 26 and the incident aperture plate 22, and the polarization state is changed by reciprocating the quarter-wave plate 23 in this process. The P-polarized light and the S-polarized light are switched, and the color separation action for the P-polarized light and the S-polarized light described above is repeated. That is, the P-polarized color light reflected by the dichroic mirror region (region formed by a part of the red dichroic mirror 261 and the blue dichroic mirror 262) 264 disposed on the exit surface of the first polarization separation prism 211 is Becomes S-polarized color light and enters a dichroic mirror region (region formed by a part of the blue dichroic mirror 262 and the green dichroic mirror 263) 265 disposed on the exit surface of the second polarization separation prism 212. On the other hand, the S-polarized color light reflected by the dichroic mirror region 265 then becomes P-polarized color light and enters the dichroic mirror region 264. In this way, the color light reflected by the dichroic mirror 26 is inverted by the action of the polarization conversion element 21 and the quarter-wave plate 23, and the dichroic mirror areas that are re-incident are alternately inverted, and during this time, the predetermined dichroic mirror is transmitted. Color separation.

  Specifically, the P-polarized green light reflected by the red dichroic mirror 261 passes through the quarter-wave plate 23 twice, so that it becomes S-polarized color light and reaches the dichroic mirror region 265 side. . Similarly, the S-polarized red light reflected by the green dichroic mirror 263 passes through the quarter-wave plate 23 twice, so that it becomes P-polarized color light and reaches the dichroic mirror region 264 side. The same applies to the P-polarized blue light reflected by the red dichroic mirror 261 and the S-polarized blue light reflected by the green dichroic mirror 263.

  Color light that has been reciprocated twice, for example, P-polarized color light reflected at an arbitrary point in the dichroic mirror region 264, becomes P-polarized light while reciprocating between the quarter-wave plate 23 and the dichroic mirror 26 twice. Then, the light enters the dichroic mirror region 264 again. However, since the light beam reflected at the arbitrary point in the dichroic mirror region 264 includes various angular components, it is not necessarily dispersed by the light quantity distribution uniformizing action of the light pipe 24 disposed in the intermediate optical path. It does not re-enter the same point. That is, all the twice reflected light beams are not reflected by the same dichroic mirror as before. Therefore, for example, when the P-polarized blue light reflected by the red dichroic mirror 261 reciprocates twice between the quarter-wave plate 23 and the dichroic mirror 26 and re-enters the dichroic mirror region 264, the blue light A part of the light enters the blue dichroic mirror 262 and is transmitted therethrough.

  Next, wavelength separation characteristics of the color separation unit shown in FIG. 1 will be described with reference to FIG.

  FIG. 3 is a diagram showing the relationship between the incident light angle and the wavelength separation characteristic with respect to the polarization separation film. As described with reference to FIG. 5, when a light ray enters from the range of 45 ° ± θ with respect to the normal line of the color separation surface, the film is designed in the range of 2θ, so that the transmission with respect to the wavelength at the half-value wavelength is performed. The rate change will be smooth. At this time, the color separation is also gentle separation, and the chromaticity value of the single color after separation is deteriorated.

  On the other hand, as shown in FIG. 3A, when a light beam having an incident angle θ is incident on a vertically arranged color separation surface, the light beam is incident from a range of ± θ with respect to the normal line of the color separation surface. . Therefore, since the film is designed in the range of θ because it is rotationally symmetric, the characteristics as shown in FIG. 3B, that is, the change in transmittance with respect to the wavelength at the half-value wavelength can be sharpened. At this time, the color separation also becomes steep separation, and the chromaticity value of the single color after separation becomes good.

  In the case of the color separator disclosed in US Patent Publication No. 2003/095213, the incident size of the color separation unit is about 1/3 of the emission size of the color separation unit. On the other hand, in the case of the color separation unit 2a of FIG. 1, the incident size of the color separation unit 2a is ½ the area of the emission size of the color separation unit 2a. Thus, the ratio of the incident size to the output size in the color separation unit 2a of FIG. 1 is larger than the ratio of the color separator disclosed in US Patent Publication No. 2003/095213. Therefore, with the color separation unit of FIG. 1 and the color separator disclosed in US Patent Publication No. 2003/095213, the condensing area of the incident light beam from the light source unit 1 to the color separation unit and the color separation unit In the color separation unit 2a shown in FIG. 1, the area ratio of the incident aperture 221 to the area of the incident aperture plate 22 can be reduced. As described above, in the color separation unit 2a of FIG. 1, a part of the light flux returned to the incident aperture plate 22 escapes from the incident aperture 221 to the light source unit 1 side, but is reflected by the dichroic mirror 26 and incident. The light flux that leaks through the opening 221 to the light source unit 1 side can be reduced.

  As described above, a total reflection surface is provided inside the light pipe incident surface, a polarization converter and a color separation element are provided on the light pipe emission surface side, and light reflected by the color separation element is transmitted from the light pipe emission surface. It is configured to re-enter the light pipe. With such a configuration, light can be reused in a color separation unit having a polarization conversion function.

  In the color separation unit of FIG. 1, the light emitted from the light pipe is separated into polarized light by the first polarizing prism and the second polarizing prism, and the dichroic mirror disposed substantially parallel to the two prism emitting surfaces. Since color separation and light reflection are performed in this case, it is possible to reduce the influence of the incident angle dependency as compared with the case where color separation is performed using a dichroic mirror or prism arranged at 45 degrees.

  Further, by adopting a configuration in which the dichroic mirror is disposed substantially parallel to the emission surfaces of the first polarization prism and the second polarization prism, the combined area of the emission surfaces of the first polarization prism and the second polarization prism, and the dichroic It is possible to make the exit areas of the mirrors equal. Accordingly, the ratio of the incident plate area of the color separation unit to the emission area of the color separation unit is increased, and the color reuse rate can be improved.

  Further, in the color separation unit 1a of FIG. 1, the incident surface of the first polarizing prism is adjacent to the entire exit surface of the light pipe, and all the light emitted from the light pipe is first incident on the first polarizing prism. Light reflected by the prism (S-polarized light) is incident on the second polarizing prism. Therefore, even if the light reflected by the dichroic mirror 26 is reflected by the green dichroic mirror 263, it reenters the light pipe via the polarizing prism in the order of the second polarizing prism and the first polarizing prism. Thus, the incident surface when re-entering the light pipe can be the entire surface of the light pipe exiting light. The re-incident light is reflected by the total reflection mirror inside the entrance aperture plate of the light pipe and is incident again on the first polarizing prism, so that the influence of the incident angle dependency on the polarizing prism can be reduced. It is.

  In the color separation unit 2a shown in FIG. 1, the half-wave plate 213 is disposed after the dichroic mirror 26. However, in terms of optical function, the dichroic mirror 26 may be disposed after the half-wave plate 213. Good. Further, instead of the second polarizing prism 212, a prism having a mirror surface may be substituted. Furthermore, an integrator such as a rod prism may be used instead of the light pipe.

  Next, returning to FIG. 1, the arrangement order of the colored light will be described.

  In general, the energy of a high-pressure mercury lamp used in a projection-type image display device has the least amount of blue light component, then the smallest red light component, and conversely, the largest amount of green light component It is. Therefore, it is effective to place the blue dichroic mirror 262 for blue light at a location close to the optical axis of the reduction optical system 31 shown in FIG.

  Each monochromatic light (for example, red light, green light, and blue light) is synthesized to obtain white light. However, as shown in Table 1, the energy ratio of each monochromatic color in the synthesized light (white light) is green. The light energy is the largest, followed by red light and finally blue light. The above-mentioned "high-pressure mercury lamp has the least amount of blue light component" means that the blue light of the light source is compared with the energy ratio of red light, green light and blue light normalized by the ratio shown in Table 1. It means that the energy ratio is small.

  The data in Table 1 is an example of color design that can be calculated by performing the four basic calculations by multiplying the wavelength characteristics of the light source by the visibility and the spectral transmittance characteristics of each optical component. Thus, in the calculation of the chromaticity value, the energy ratio of red light, green light, and blue light may be maintained at a predetermined ratio. However, since the contrast performance is defined by the ratio of the luminous flux amount between the voltage ON state and the voltage OFF state of the image display element 6, the green light voltage with the largest energy ratio is required in order to obtain good contrast performance. It is important to cut off the light when OFF. That is, it is important to increase the degree of polarization (extinction ratio) of the color bar of green light emitted after color separation by the color separation unit 2a.

  Therefore, as shown in FIG. 1, it is effective to arrange the green dichroic mirror 263 corresponding to the green light on the optical path that passes through the first polarization separation prism 211 and the second polarization separation prism 212. That is, in FIG. 1, among the natural light L20 incident on the first polarization separation prism 211 from the light pipe 24, the S-polarized green light L20SG is reflected and further reflected by the second polarization separation prism 212, and the S-polarization light is reflected. It becomes S-polarized green light L21SG with an increased degree of polarization (extinction ratio), passes through the green dichroic mirror 263, and is converted by the half-wave plate 213 from S-polarized light to P-polarized light and emitted. That is, since the green light has passed through the first polarization separation prism and the second polarization separation prism, the degree of polarization of the green light transmitted through the green dichroic mirror 263 is increased. In this way, the degree of polarization (extinction ratio) of green light is increased, and an improvement in contrast can be expected.

  As described above, in order to prioritize the blue light transmission rate, the blue dichroic mirror 262 corresponding to the blue light is shifted to the green light at the middle position where it is emitted from the first polarization separation prism 212 and the second polarization separation prism 212. The corresponding green dichroic mirror 263 is disposed at a position where it exits from the second polarization separation prism 212, and the red dichroic mirror 261 corresponding to the remaining red light is disposed at a position where it directly exits from the first polarization separation prism 211.

  Next, another example of the color separation unit will be described with reference to FIG.

  The color separation unit 2b shown in FIG. 5 is a color separation unit in consideration of the peripheral light amount ratio. In other words, in the case where the color distribution is not symmetrical about the optical axis 100 of the illumination optical system, the variation in the light amount distribution caused by the difference in the incident angle at which each color light enters the polyhedral rotating body is taken into consideration. Details are disclosed in Japanese Patent Application No. 2005-137987. Accordingly, in consideration of the peripheral light amount ratio, for example, the red dichroic prisms 251a and 251a ′, the green dichroic prisms 252a and 252a ′, the blue dichroic prism 253a, and the like are symmetrical about the optical axis 100 of the illumination optical system. It is necessary to arrange 253a ′.

  The polarization conversion element of the color separation unit 2b shown in FIG. 5 is obtained by arranging the polarization conversion elements 21 of FIG. 1 symmetrically about the optical axis 100 in the Y-axis direction. That is, first, the first polarizing prisms 211a and 211b that transmit P-polarized light and reflect S-polarized light are arranged above and below the optical axis as a center. The first polarizing prism 211a has a polarization action surface so that the reflection direction of S-polarized light is on the Y-axis. The first polarizing prism 211b is provided with a polarization action surface so that the reflection direction of S-polarized light is in the Y-axis downward direction. Outside the first polarizing prisms 211a and 211b, second polarizing prisms 212a and 212b that reflect S-polarized light and transmit P-polarized light are respectively disposed.

  A dichroic mirror is disposed adjacent to the second polarizing prism. For example, the green dichroic mirror 261a, the red dichroic mirror 262a, the blue dichroic mirror 263a, b, the red dichroic mirror 262b, and the green dichroic mirror 261b are arranged in this order from the top in the Y-axis direction. The green dichroic mirror 261a to the blue dichroic mirror 263a are adjacent to the emission surfaces of the first polarizing prism 211a and the second polarizing prism 212b. Similarly, the blue dichroic mirror 263b to the green dichroic mirror 261b are adjacent to the emission surfaces of the first polarizing prism 211b and the second polarizing prism 212b. Further, half-wave plates 213a and 213b are arranged at positions corresponding to the emission surfaces of the second polarizing prisms 212a and 212b on the outer side. With such a configuration, it becomes possible to arrange blue light at a position close to the optical axis of the reduced illumination system. In addition, for green light, the energy level of blue light can be brought close to the energy level of other color lights by passing through the first polarizing prisms 211a and 211b and the second polarizing prisms 212a and 212b.

  In the example of FIG. 5, the light pipe exit surface and the incident surfaces of the two first polarizing prisms 211a and 211b coincide with each other, so that the light reflected by the dichroic prisms 251 to 253 is re-input to the light pipe. The angle becomes equal to or greater than a predetermined angle, which may affect the angle dependency when light re-reflected by the total reflection plate 22 re-enters the first polarizing prisms 211a and 211b. However, with the configuration shown in FIG. 4, the light incident on the polarization conversion element 21 ′ from the light pipe 24 is aligned in polarization, separated in color, and emitted in a symmetrical color arrangement with the optical axis 100 as the center. In this way, it is possible to improve the color separation characteristics depending on the incident angle in the same manner as in FIG.

  Further, in the case of the color separation unit of FIG. 5, the ratio of the area of the incident surface to the area of the exit surface of the polarization conversion element 21 ′ is ½, and the area ratio of the incident aperture 221 to the area of the incident aperture plate 22 is reduced. It becomes possible to do.

  In the example of FIG. 5, the first polarizing prisms 211a and 211b are arranged so as to be sandwiched between the second polarizing prisms 212a and 212b with the optical axis as the center. However, the present invention is not limited to this, and the first polarizing prism and the second polarizing prism are arranged. It is good also as a structure which arrange | positions alternately. In that case, the light emitted from the light pipe is incident on, for example, the first polarizing prism 211a and the second polarizing prism 212a, and a half-wave plate may be provided so as to face the second polarizing prism 212a.

It is an example of the schematic block diagram of a color separation unit. It is an example of the schematic block diagram of a projection type video display apparatus. It is a figure explaining the difference in the color separation characteristic by the incident angle to a color separation surface. It is a figure explaining the color separation characteristic by the incident angle to the conventional color separation surface. It is another example of the schematic block diagram of a color separation unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Light source unit, 11 ... Light source, 12 ... Reflector, 2a, 2b ... Color separation unit, 21 ... Polarization conversion element, 21 '... Polarization conversion element, 211 ... 1st polarization separation prism, 212 ... 2nd polarization separation prism, 213 ... 1/2 wavelength plate, 22 ... incident aperture plate, 221 ... incident aperture, 222 ... total reflection surface, 23 ... ¼ wavelength plate, 24 ... light pipe, 25 ... color prism, 26 ... dichroic mirror, 261 ... Red dichroic mirror, 262 ... Blue dichroic mirror, 263 ... Green dichroic mirror, 264, 265 ... Dichroic mirror region, 31, 33 ... Reduction optical system, 32 ... Optical path bending mirror, 33 ... Enlarging optical system (shared optical path) DESCRIPTION OF SYMBOLS 4 ... Rotation polyhedron, 51 ... 1st PBS, 52 ... 2nd PBS, 6 ... Image display element, 7 ... Projection lens, 8 DESCRIPTION OF SYMBOLS 1 ... Polarizing plate, 82 ... 1/4 wavelength plate, 83 ... 1/2 wavelength plate, 84 ... Polarizing plate.

Claims (4)

A white light source that emits a visible light beam;
A color separation unit that enters the visible light beam and emits the light as a plurality of color lights;
An image display element that is irradiated with the plurality of color lights and modulates the color light according to a video signal of a color corresponding to the color of the emitted color light;
A scanning unit for moving the irradiation positions of the plurality of color lights on the image display element in a certain direction;
A projection device that projects a plurality of color lights modulated by the image display element as a color image;
The color separation unit is
An optical integrator for homogenizing the visible light beam, an optical aperture having an incident aperture plate through which the visible light beam is transmitted, and an optical integrator having a first exit surface for emitting the uniformed visible light beam,
A dichroic mirror that transmits colored light in a predetermined wavelength region and reflects colored light in other wavelength regions in a uniform visible light beam, wherein the first emission surface and each separation surface are arranged substantially parallel to each other A first separation surface that transmits color light in the red wavelength region, a second separation surface that transmits color light in the blue wavelength region that is disposed across the first separation surface, and a green wavelength region. A dichroic mirror having a third separation surface that transmits color light;
A projection-type image display apparatus comprising: a polarization conversion element that converts a uniform visible light beam incident on the dichroic mirror or a plurality of color lights emitted from the dichroic mirror into predetermined polarized light. A white light source that emits a visible light beam;
A color separation unit that enters the visible light beam and emits the light as a plurality of color lights;
An image display element that is irradiated with the plurality of color lights and modulates the color light according to a video signal of a color corresponding to the color of the emitted color light;
A scanning unit for moving the irradiation positions of the plurality of color lights on the image display element in a certain direction;
A first mapping optical system that maps the plurality of color lights in the vicinity of the scanning unit;
A second mapping optical system for mapping a plurality of color lights reflected by the scanning unit onto the image display element;
A projection device that projects a plurality of color lights modulated by the image display element as a color image;
The color separation unit is
An optical integrator for homogenizing the visible light beam, an optical aperture having an incident aperture plate through which the visible light beam is transmitted, and an optical integrator having a first exit surface for emitting the uniformed visible light beam,
A dichroic mirror that transmits colored light in a predetermined wavelength region and reflects colored light in a wavelength region other than the uniformed visible light beam, and is disposed on the optical axis of the first mapping optical system. A first separation surface that transmits color light in a blue wavelength range, in which the first emission surface and each separation surface are arranged substantially in parallel, and a red wavelength range that is arranged across the first separation surface. A dichroic mirror having a second separation surface that transmits color light and a third separation surface that transmits color light in the green wavelength range;
A projection-type image display apparatus comprising: a polarization conversion element that converts a uniform visible light beam incident on the dichroic mirror or a plurality of color lights emitted from the dichroic mirror into predetermined polarized light. In the projection type video display device according to claim 1 or 2,
The polarization conversion element is:
A first polarization separation prism that reflects the first polarized light and transmits the second polarized light;
A second polarization separation prism that enters the first polarized light separated by the first polarization separation prism and aligns the emission direction of the first polarization light with the emission direction of the second polarization light;
A half-wave plate disposed to face the exit surface of the second polarization separation prism;
The projection-type image display device, wherein the third separation surface receives light emitted from the second polarization separation prism. A white light source,
An image display element that forms an optical image according to an image signal from the light emitted from the white light source;
A color separation unit that separates a visible light beam emitted from the white light source into light of a plurality of colors;
Scanning means for moving light of a plurality of colors emitted from the emission surface of the color separation unit on the video display element;
A first mapping optical system for mapping the color bar separated by the color separation unit in the vicinity of the scanning means;
A second mapping optical system for mapping the color bar scanned by the scanning means onto the image display element;
In a projection-type image display device comprising a projection device that projects light emitted from the image display element as a color image,
The color separation unit is arranged in order from the incident side.
An entrance aperture for entering the emitted light of the white light source is formed, and an entrance aperture plate having a total reflection surface in a region other than the entrance aperture on the exit side surface of the color separation unit;
A quarter wave plate,
A light pipe having a uniform light quantity distribution;
A first polarization separation prism that contacts the light pipe, reflects the first polarized light, and transmits the second polarized light;
A second polarization separation prism that enters the first polarized light separated by the first polarization separation prism and aligns the emission direction of the first polarization light with the emission direction of the second polarization light;
A plurality of dichroic mirrors that transmit color light in a predetermined wavelength region from white light and reflect color light in other wavelength regions, and transmit red light on the exit surface of the first polarization separation prism and transmit light in other wavelength regions; A red dichroic mirror that reflects colored light, a blue dichroic mirror that transmits blue light on both the emission surfaces of the first polarization separation prism and the second polarization separation prism and reflects color light in other wavelength ranges, A dichroic mirror in which green dichroic mirrors that transmit green light and reflect color light in other wavelength ranges are arranged on the exit surface of the polarization separation prism;
A projection-type image display device comprising a half-wave plate facing the exit surface of the second polarization separation prism.

Images