JP2004361982A - Projection type display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection type display device which has small color unevenness and illuminance unevenness, and, moreover, has high illumination efficiency. <P>SOLUTION: The projection type display device 1 comprises an illumination optical system 2A, a color separation system 4, three liquid crystal panels 5R, 5G, 5B, a light guide system 9 which is arranged on the optical path of the luminous flux G having the longest optical path length, a dichroic prism 6, and a projection lens 7 which projects the luminous flux on a screen 8. The lighting optical system 2A is equipped with a uniform illumination element 3 which converts the luminous flux into uniform rectangular luminous flux. Since the uniform lighting optical element for suppressing the color unevenness and illuminance unevenness is built into the illumination optical system, the projection type display device having small color unevenness and illuminance unevenness, and, moreover, high lighting efficiency can be obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention separates a light beam from a light source into three color light beams of red, blue, and green, modulates each of these color light beams according to video information through a modulation unit, and re-modulates the modulated light beam of each color after the modulation. The present invention relates to a projection display device that synthesizes and projects an enlarged image on a screen via a projection lens.

  The projection display apparatus includes a light source lamp, a color separating unit that separates a light beam from the light source lamp into three color light beams, three light valves that modulate the separated three color light beams, and a light valve that has been modulated. It is composed of a color synthesizing means for re-synthesizing the color luminous flux and a projection lens for enlarging and displaying an optical image obtained by the synthesis on a screen. A liquid crystal panel is generally used as a light valve.

U.S. Pat. No. 5,098,184

  As a conventional projection type display device having this configuration, a projection display device in which a uniform illumination optical element called an optical integrator is incorporated in a light source portion thereof is known. For example, Patent Literature 1 discloses a projection display device in which the optical integrator is incorporated. In this publication, a configuration in which dichroic mirrors are arranged in an X shape is described as a color synthesizing means. Usually, it is composed of a dichroic mirror having a dielectric multilayer film formed on a glass plate.

  As described above, the projection display apparatus including the mirror combining system in which the color combining means is configured by the dichroic mirror has the following problems. That is, the dichroic mirror is an optical element that is not rotationally symmetric with respect to the center axis of the projection lens. For this reason, astigmatism occurs in the image on the screen, and the MTF (Modulation Transfer Function) characteristic indicating the transfer characteristic of the projection optical system deteriorates. As a result, the image quality is blurred and the sharpness is reduced. Deterioration of the MTF characteristic is not so problematic when the size of the liquid crystal panel is large relative to the number of pixels, that is, when the pixel pitch is large. However, when the pixel pitch is small as in the case of a liquid crystal panel using a polysilicon TFT as a switching element, it cannot be ignored.

  Further, as a conventional projection type display device, a type having a prism combining system in which a color combining means is constituted by a dichroic prism is known. The dichroic prism is an optical element that is rotationally symmetric with respect to the central axis of the projection lens. Therefore, the aberration generated by the prism can be easily removed by the design of the projection lens. Generally, the MTF characteristic in the projection display device having the prism combining system has the above-mentioned mirror combining system. It is better than the one that you have. Therefore, it is suitable when a liquid crystal panel having a small pixel pitch is used as a light valve.

  Further, as a conventional projection display device, for example, there is one disclosed in US Pat. No. 4,943,154. This device is configured to suppress a decrease in light quantity and color unevenness by interposing a light transmission unit including a relay lens, a field lens, and the like in an optical path of color light having the longest optical path length.

  However, in this device, although the light amount of the color light having the longest optical path length is not reduced, since the brightness distribution of the light beam is rotated by 180 degrees by the relay lens, if the original brightness distribution is not axially symmetric, Non-axisymmetric color unevenness occurs in the display on the screen, and the display quality deteriorates. If the brightness distribution of the luminous flux is axisymmetric, such color unevenness does not occur, but in reality, it is caused by a shift in the mounting position of the light source lamp and slight asymmetry of the light source lamp and its reflecting mirror. Normally, the brightness distribution becomes non-axisymmetric.

  Here, in the projection display device, there is a demand for increasing the illuminance of the projected image, eliminating the color unevenness and the illuminance unevenness, and obtaining an image quality close to a CRT direct-view image. For this purpose, it is preferable to use a prism combining system having good transfer characteristics as the color combining system. Further, it is preferable to illuminate the liquid crystal panel with uniform brightness and efficiently by using an optical integrator in a light source portion. However, when the optical path length of each color light in the color separation system is different, if the optical integrator is used as it is, the decrease in the light amount of the color light assigned to the longest optical path and the change in the illuminance distribution become remarkable. The image appears as uneven color or a change in color temperature. Therefore, the effect of the integrator cannot be sufficiently exhibited. Furthermore, when an optical integrator is used for the light source portion, the conventional technology cannot be used as it is. That is, in the illumination using the optical integrator, the divergent light flux from the surface light source located at a finite position (the light flux emission surface of the integrator) from the liquid crystal panel illuminates the liquid crystal panel. This is because it is basically different from the case where it can be regarded as the illumination from the point light source existing in.

  An object of the present invention is to propose a projection display device capable of forming a projection image of superior quality without uneven illuminance and uneven color as compared with the above-mentioned conventional projection display device.

  Another object of the present invention is to propose an inexpensive projection display device capable of forming a high-quality projected image.

  A further object of the present invention is to propose a projection display device capable of forming a projection image having higher illuminance than the conventional one.

  Still another object of the present invention is to propose a compact projection display device capable of forming a high-quality projected image.

  Still another object of the present invention is to propose a projection display device having a configuration suitable for use as a front projection type.

  In order to achieve the above object, a projection display device according to the present invention includes a light source, a color separation unit that separates a white light beam emitted from the light source into three color light beams, and modulates the separated light beam of each color. Three light valves, and light guiding means disposed on the optical path of the light beam having the longest optical path length among the light beams of each color separated by the color separating means and incident on each of the three light valves, A projection type display device having a color synthesizing unit for synthesizing a modulated light beam of each color modulated through the light valve, and a projection lens for projecting the synthesized modulated light beam on a screen, wherein the light source and the color separating unit are provided. And a uniform illumination optical unit that converts a white light beam from the light source into a uniform rectangular light beam and emits it toward the color separation unit, and emits a light beam of each color in the color separation unit. A light condensing lens, wherein the light converging means comprises three condensing lenses for converting a divergent light beam from the uniform illumination optical means into a substantially parallel light beam, wherein the color synthesizing means is a dichroic prism; Is characterized in that the color light passing through is green light. In the projection display apparatus of the present invention having this configuration, the light valve is illuminated by using the uniform illumination optical means, and a condensing lens is arranged in the optical path of each color light to convert the divergent light flux into a parallel light flux and to guide the light. Green light is passed through the means. Therefore, according to the present invention, it is possible to form a brighter and higher quality projected image with uniform illuminance distribution and without color unevenness.

  Here, as the light guide means, one having an incident-side reflecting mirror, an outgoing-side reflecting mirror, and at least one lens can be used.

  Further, the light guide means has one intermediate lens, and the focal length of the intermediate lens is set within a range of about 0.9 to 1.1 times the optical path length of the light guide means. Is preferred.

  Further, the light guide means is provided between the incident lens disposed on the incident side of the incident side reflector, the output side lens disposed on the output side of the output side reflector, and the incident side and the output side reflector. In this case, the focal lengths of the input and output lenses are set within a range of about 0.5 to 0.7 times the optical path length of the light guide means. It is desirable to set and set the focal length of the intermediate lens within a range of about 0.25 to 0.4 times the optical path length of the light guide means to suppress aberration.

  Further, in this case, if the above-mentioned incident lens and the above-mentioned condensing lens for entering the parallel light beam toward this incident lens are formed as a single lens, the optical system can be made compact accordingly. It is preferred. Here, when a single lens is used, it is preferable to use an aspheric lens in order to suppress aberration around the lens.

  Further, as the light guide means, an incident-side triangular prism disposed on the incident side and bending the optical path by 90 degrees, an output-side triangular prism disposed on the output side and bending the optical path by 90 degrees, and disposed between these triangular prisms And a light guide member provided with the light guide member.

  Here, a square prism can be used as the light guide member. Further, it is preferable to apply an anti-reflection coating to the interface between the triangular prism and the quadrangular prism. Further, it is preferable that the total reflection surface of the triangular prism is coated with a metal film or a dielectric multilayer film.

  Next, a liquid crystal panel can be used as the light valve. In this case, it is preferable to set the pixel pitch of the liquid crystal panel to about 50 μm or less to increase the definition of the projected image.

  On the other hand, as the uniform illumination optical unit, a unit having at least one lens plate in which a plurality of lenses are arranged in a plane perpendicular to the main axis of the output light of the light source lamp can be adopted. In this case, it is preferable that the number of lens divisions in one direction on the lens plate is between about 3 and about 7.

  Here, as uniform illumination optical means, a first lens plate, a second lens plate, and a reflecting mirror interposed therebetween may be provided, and the optical path may be bent at a right angle, for example. .

  Further, it is preferable to arrange the polarization conversion means in the uniform illumination optical means. This polarization conversion means is composed of a polarization separation element for separating random polarized light from a light source lamp into two linearly polarized lights of P and S waves, and a polarization plane rotation element for matching the polarization planes of the two separated polarized lights. You. By using this polarization conversion means, the efficiency of use of the light emitted from the light source lamp can be increased, and accordingly, the illuminance of the projected image can be increased.

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

FIG. 1 shows an optical system of a projection display apparatus according to Embodiment 1 of the present invention. The projection display apparatus 1 of the present example includes a light source 2, an illumination optical system 2 </ b> A including a uniform illumination optical element 3, and a light beam W emitted from the illumination optical system 2 </ b> A via the uniform illumination optical element 3. A color separation optical system 4 for separating red, green, and blue light fluxes R, G, and B; three liquid crystal panels 5R, 5G, and 5B as light valves for modulating each color light flux; It has a color synthesizing optical system 6 for re-synthesizing and a projection lens 7 for enlarging and projecting the synthesized luminous flux on a screen 8. The light guide system 9 guides the green light flux G to the corresponding liquid crystal bulb 5G among the color light fluxes separated by the color separation optical system 4.

  The light source 2 according to the present embodiment includes a light source lamp 21 and a curved reflecting mirror 22. As the light source lamp 21, a halogen lamp, a metal halide lamp, a xenon lamp, or the like can be used. Although details will be described later, the uniform illumination optical system 3 includes a first lens plate 31 and a second lens plate 32 arranged on a plane perpendicular to the central optical axis 1a of the illumination optical system.

The color separation optical system 4 includes a blue-green reflecting dichroic mirror 401, a blue reflecting dichroic mirror 402, and a reflecting mirror 403. The light beam W is first reflected by the blue-green reflection dichroic mirror 401 at a right angle to the blue light beam B and the green light beam G contained therein, and travels toward the blue reflection dichroic mirror 402.
The red light beam R passes through the mirror 401, is reflected at a right angle by the rear reflecting mirror 403, and is emitted from the red light emitting unit 404 to the color combining optical system side. The blue and green light beams B and G reflected by the mirror 401 are reflected only at a right angle by the blue reflection dichroic mirror 402 at the blue light beam B, and are emitted from the blue light emission unit 405 to the color combining optical system side. You. The green light flux G that has passed through the mirror 402 is emitted from the green light emission part 406 toward the light guide system 9. In this example, the distances from the light emitting portions of the uniform illumination optical element 3 to the light emitting portions 404, 405, and 406 of the respective color light beams in the color separation optical system 4 are all set to be equal.

  Here, in this example, condensing lenses 101, 102, and 103 made of plano-convex lenses are arranged on the emission sides of the emission sections 404, 405, and 406 of the color light beams of the color separation optical system 4, respectively. Therefore, the light beams of the respective colors emitted from the respective emission portions are incident on these condenser lenses 101 to 103 and are collimated.

  The red and blue luminous fluxes R and B of the color luminous fluxes R, G and B after being collimated are incident on the liquid crystal panels 5R and 5B disposed immediately after the condenser lenses 101 and 102 and are modulated. , Video information corresponding to each color light is added. That is, these liquid crystal panels are subjected to switching control by driving means (not shown) in accordance with video information, thereby modulating each color light passing therethrough. As such a driving unit, a known unit can be used as it is, and a description thereof will be omitted in this embodiment. On the other hand, the green luminous flux G is guided to the corresponding liquid crystal panel 5G via the light guide system 9, where it is similarly modulated according to video information. The liquid crystal panel of this example uses a pixel TFT using a polysilicon TFT as a switching element and having a pixel pitch of 50 μm or less.

  The light guide system 9 in this example includes an entrance-side reflection mirror 91, an exit-side reflection mirror 92, and an intermediate lens 93 disposed therebetween. In this example, the focal length of the intermediate lens 93 is set equal to the total optical path length of the light guide system 9. This focal length can be set within a range of about 0.9 to about 1.1 times the total optical path length of the light guide system. Here, the light path length of each color light beam, that is, the distance from the light source lamp 21 to each liquid crystal panel is the longest for the green light beam G, and therefore, the loss of the light amount of this light beam is the largest. However, by interposing the light guide system 9 as in this example, the loss of the light amount can be suppressed. Note that the color light beam that passes through the light guide system 9 may be a red or blue light beam. However, in general, in a normal projection display device, the amount of green light is larger than the amount of other colors, so that it is preferable to assign a green light flux to an optical path passing through the light guide system 9. However, when priority is given to brightness and image quality uniformity over color balance, a blue light flux having low visibility and relatively inconspicuous illuminance may be assigned to the light guide system 9.

Next, each color light beam modulated through each of the liquid crystal panels 5R, 5G, and 5B enters the color combining optical system 6, where it is recombined. In this example, the color synthesizing optical system 6 is configured using a dichroic prism. As the color combining optical system 6, a mirror combining system having a configuration in which dichroic mirrors are arranged in an X shape can be used.
However, in a projection display device including a mirror combining system in which the color combining optical system is configured by a dichroic mirror, the dichroic mirror is an optical element that is not rotationally symmetric with respect to the center axis of the projection lens. For this reason, astigmatism occurs in the image on the screen, and the MTF (Modulation Transfer Function) characteristics of the projection optical system deteriorate. As a result, the image quality is blurred and the sharpness is reduced. Deterioration of the MTF characteristic is not so problematic when the size of the liquid crystal panel is large relative to the number of pixels, that is, when the pixel pitch is large. However, when the pixel pitch is small as in a liquid crystal panel using a polysilicon TFT as a switching element as in this example, it cannot be ignored. In this example, since a dichroic prism is used as the color synthesizing optical system 6, it is possible to avoid such a problem.

  This will be described with reference to FIG. This figure shows the MTF characteristics of the projection display device including the prism combination system of the present example and the projection display device when the color combination system is a mirror combination system. In this figure, the horizontal axis represents the spatial frequency (1 in / mm) indicating the fineness of the pixels of the liquid crystal panel, and the vertical axis represents the MTF (%). The solid line indicates the characteristics of the projection optical system provided with the prism combining system. The thick solid line is the characteristic at the center of the screen, and the thin solid line is the characteristic at the periphery of the screen. Similarly, a broken line indicates a characteristic in a projection optical system having a mirror combining system. The thick broken line is the characteristic at the center of the screen, and the thin broken line is the characteristic at the periphery.

  The MTF characteristic of the projection lens alone deteriorates due to the occurrence of astigmatism because the mirror is inserted at an angle of 45 degrees in the mirror combining system. As in this example, in a liquid crystal panel using a polysilicon TFT as a switching element and having a pixel pitch of 50 μm or less, an MTF characteristic of 30% or more is required when the spatial frequency is 20 (1 in / mm). However, when the mirror combining system is used, it can be seen that sufficient MTF characteristics cannot be obtained at the periphery of the screen. On the other hand, when a prism combining system is used as in this example, aberration generated by the prism can be removed by designing the projection lens, and it can be seen that there is no deterioration in MTF characteristics.

  In the apparatus of the present embodiment, the light beams of the respective colors are combined in a color combining system including a dichroic prism to obtain an optical image, and the optical image is enlarged and projected on a screen 8 by a projection lens 7. As the projection lens, a lens close to a telecentric system is preferable.

(Illumination optical system)
As an example suitable for the uniform illumination optical element 3 in the illumination optical system of the present example, there is an integrator lens generally used for an exposure machine. FIG. 3A shows a basic structure when used in a projection display device. As shown in this figure, the uniform illumination optical element 3 is composed of a first lens plate 31 and a second lens plate 32. The first lens plate 31 has a configuration in which a plurality of rectangular lenses 301 are arranged in a matrix. Similarly, the second lens plate 32 has a configuration in which rectangular lenses 302 are arranged in a matrix. The shape of each rectangular lens 301 of the first lens plate 31 is similar to the shape of the liquid crystal panel to be illuminated. The images of these rectangular lenses 301 are superimposed and formed on the liquid crystal panel by the corresponding rectangular lenses of the rectangular lenses 302 constituting the second lens plate 32. Therefore, the liquid crystal panel is illuminated with uniform illuminance and with almost no color unevenness.

  In this example, rectangular lenses are arranged in each of the lens plates 31 and 32 so as to form a matrix of 4 rows × 3 columns. The maximum number of divisions in the vertical or horizontal direction is preferably in the range of about 3 to 7. Further, the first lens plate 31 and the second lens plate 32 do not always need to be separated. By reducing the size of each rectangular lens and increasing the number of divisions of the incident light beam, the lens plates 31 and 32 can be made closer. Furthermore, it is also possible to temporarily integrate one lens.

  Here, with reference to FIG. 5, the relationship between the number of divisions by the rectangular lenses of the lens plates 31 and 32 constituting the uniform illumination optical element 3 and the color unevenness will be described. In the graph of FIG. 5, the horizontal axis indicates the number of divisions of the first and second lens plates (integrator lenses), and the vertical axis indicates color unevenness. The difference in color between the two points is indicated as a difference on the U′V ′ chromaticity coordinates. The smaller the value indicating the color unevenness, the smaller the degree of the color unevenness. The value indicated by the broken line in the figure is the maximum color unevenness determined to be acceptable as the color unevenness.

  As can be seen from this graph, it is preferable that the number of divisions is three or more. However, from the viewpoint of manufacturing, increasing the number of divisions leads to an increase in cost. Therefore, a practical number of divisions ranges from about 3 to about 7.

  Next, FIG. 3B shows another configuration example of the first lens plate 31 and the second lens plate 32 that constitute the uniform illumination optical confectionery 3. Also in the example shown in this figure, each lens plate is formed of a rectangular lens plate having the same dimensions. However, in the arrangement state of the rectangular lenses, the number of divisions in the vertical direction is 7, and in the horizontal direction, the upper and lower rows are divided into three, the central three rows are divided into five, and the rows between these are divided into four. It is divided.

  As shown in FIG. 4, the uniform illumination optical element 3 includes a first lens plate 31 composed of a plurality of cylindrical lenses 301 ′ and a second lens plate 32 composed of a plurality of cylindrical lenses 302 ′. There is also a method of configuring using this. In this case, the illuminance is made uniform in only one direction, and the central illuminance of the illumination target becomes higher than in the cases of FIGS. 3A and 3B. In this case, since the lens configuration is relatively simple, it is easy to reduce the thickness.

  Next, with reference to FIG. 6A, an operation in the case where the liquid crystal panels 5R, 5G, and 5B are illuminated using the uniform illumination optical element 3 having the above configuration will be described. As described above, a light source close to a point such as a halogen lamp, a metal halide lamp, or a xenon lamp is used as the light source lamp 21 constituting the light source 2. The luminous flux from the lamp is reflected by the reflecting mirror 22. An elliptical surface can be used as the reflecting surface shape of the reflecting mirror 22. In this case, the first focal point is made to coincide with the light emitting portion of the light source lamp 21, and the second focal point is set to the liquid crystal panel 5 (5R, 5G, 5B). To the center position of. As a result, the light beam reflected by the reflecting mirror 22 goes to the center of the liquid crystal panel 5. In this case, the second lens plate 32 is positioned so that the center of each rectangular lens 302 of the second lens plate 32 is located on a line from the center of each rectangular lens 301 of the first lens plate 31 toward the center of the liquid crystal panel 5. Of the lens plate 32, that is, the size of each rectangular lens 302 constituting the lens plate is set smaller than that of the first lens plate.

  Each rectangular lens 301 of the first lens plate 31 focuses a light beam on the center of each rectangular lens 302 of the corresponding second lens plate 32. Each rectangular lens 302 of the second lens plate 32 superimposes the image of the lens of the corresponding rectangular lens 301 on the side of the first lens plate on the display area 5A of the liquid crystal panel 5 (the area indicated by oblique lines in the figure). Image. Since the image of the light emitting portion of the light source lamp 21 is thus formed at the center of each rectangular lens 302 of the second lens plate 32, the entire second lens plate 32 functions as a secondary light source. Therefore, for example, the principal ray 303 of the light beam incident on the end of the display area 5A of the liquid crystal panel 5 coincides with a line segment connecting the center of the second lens plate 32 and the end of the display area 5A. That is, since the illuminating light beam to the liquid crystal panel 5 is divergent light from the second lens plate 32, it is necessary to collimate the divergent light in order to make parallel light incident on the liquid crystal panel 5. For this purpose, in this example, condenser lenses 101, 102, 103 are arranged. What is the focal length of this condenser lens? It is set equal to the distance b between the second lens plate 32 and the condenser lens. In this example, a plano-convex lens is used as the condenser lens with the convex surface facing the liquid crystal panel 5 side. The convex surface may be arranged so as to face the second lens plate. Instead of a plano-convex lens, a biconvex lens or a Fresnel lens can also be used. By arranging the condenser lenses 101, 102, and 103 in this way, the principal ray of the light beam emitted through the liquid crystal panel 5 becomes parallel to the central axis 1a of the entire illumination system.

  Next, FIG. 6B shows a modification of the illumination optical system. In this example, a paraboloid is used as a reflection surface of the reflection mirror 22 of the light source 2. In this case, since the focus of the paraboloid is made to coincide with the light emitting portion of the light source lamp 21, the light flux reflected by the reflecting mirror 22 becomes a light flux substantially parallel to the central axis 1a of the illumination system. Therefore, the uniform illumination optical element 3 used in this case is composed of the first lens plate 31 'and the second lens plate 32' having the same dimensions, and the focal length of the rectangular lens forming each lens plate is also large. equal. Each rectangular lens 302 'of the second lens plate 32' forms an image of the corresponding rectangular lens of the first lens plate 31 'at infinity. Therefore, in this case, an image that can be formed at infinity is formed on the display area 5A of the liquid crystal panel 5 by adding the lens 306. The focal length of the lens 306 is set to be equal to the distance between the lens and the liquid crystal panel 5. Note that the lens 306 can be integrated with the second lens plate 32.

  When the number of divisions of the lens plates 31 and 32 by the rectangular lenses is relatively small, the distance between the lens plates can be made relatively large, and as shown in FIG. A mirror 33 can be interposed. In this case, there is an advantage that the volume occupied by the uniform illumination optical element is reduced to about の of that of the previous example. Further, as shown in this figure, the arrangement of all the optical systems can be approximated to a square, which contributes to downsizing of the entire apparatus.

(Light guide system)
As described above, the light guide system 9 of the present embodiment includes the two reflecting mirrors 91 and 92 and the intermediate lens 93 disposed therebetween. Another configuration example of the light guide system applicable to this embodiment will be described below.

  First, the light guide system 9A shown in FIG. 7 has a configuration in which the intermediate lens 93 is omitted from the light guide system 9 of this example.

  Next, in the light guide system 9B shown in FIG. 8A, in addition to the configuration of the light guide system 9 of the present example, an incident lens 94 is added to the incident portion side and an output lens 95 is provided to the output portion side. Is added.

The operation of the light guide system 9B having this configuration will be described with reference to FIG. In the figure, for the sake of simplicity, a pair of reflecting mirrors 91 and 92 is shown as a linear system in which it is omitted. As shown in the figure, the intermediate lens 93 is located exactly at the center of the entire optical path of the light guide system 9B. If the total optical path length is 2a, the focal length of the intermediate lens 93 is set to be substantially equal to a / 2. is there. Therefore, the intermediate lens 93 forms an image of the object 96 on the incident side of the light guide system 9B as an inverted image 97 on the emission side of the light guide system.
That is, the illuminance distribution on the incident side is transmitted by being rotated 180 degrees on the exit side. However, in this example, since the illumination optical system including the uniform illumination optical element 3 is used, the illuminance distribution is substantially symmetric with respect to the rotation of 180 degrees. Therefore, even if the illuminance distribution is rotated or inverted in this manner, color unevenness of the display does not occur.

  On the other hand, the incident lens 94 has a focal length equal to the distance a to the intermediate lens 93, and directs the principal ray 9 a of the light flux G passing through the condenser lens 103 and becoming parallel to the center of the intermediate lens 93. Therefore, an image of the second lens plate 32 on the emission side of the uniform illumination optical element 3 is formed at the center of the intermediate lens 93. The focal length of the exit lens 95 is also set to be equal to a, and the principal ray of the light beam diverging from the center of the intermediate lens 93 is emitted in parallel. As shown in the drawing, the incident lens 94 is a plano-convex lens, and the convex surface side is arranged toward the incident side, thereby reducing the spherical aberration of the lens. The exit lens 95 is also a plano-convex lens, and is disposed so that the convex side faces the exit side.

  The focal lengths of the input lens and the output lens may be set within a range of about 0.5 to about 0.7 times the total optical path length (2a) of the light guide system 9B. Further, the focal length of the intermediate lens is preferably slightly longer than 全 of the total optical path length (2a), from the viewpoint of reducing spherical aberration, and is in the range of about 0.25 to about 0.4 times. Should be set to.

  FIG. 9A shows a modification of the light guide system 9B. In the light guide system 9C shown in this figure, the incident lens 94 in the light guide system 9B is a lens 97 that is integrated with the condenser lens 103 disposed in front of the light path direction. The focal length of the lens 97 is set to a value obtained by adding the refractive powers of the incident lens 94 and the condenser lens 103. That is, as shown in FIG. 9B, it is set to ab / (a + b). This lens 97 is preferably a biconvex lens in order to reduce spherical aberration. In FIG. 9B, the intermediate lens 93 is shown as being composed of two plano-convex lenses 931 and 932. As shown in the figure, in this case, the focal length of each of the plano-convex lenses 931 and 932 is set to a. Further, by arranging the convex surfaces of the lenses facing each other, the spherical aberration can be extremely reduced as compared with a single biconvex lens. As a result, the illuminance distribution on the entrance side of the light guide system can be transmitted to the exit side very accurately.

  Next, FIG. 10 shows a modification of the light guide system 9C. In the light guide system 9D shown in the figure, the lens 97 integrated in the light guide system 9C is an aspheric lens 98. By using the aspherical lens 98 in this way, it is possible to further reduce spherical aberration as compared with the case of using a biconvex lens. Therefore, the illuminance distribution on the incident side of the light guide system can be transmitted to the exit side extremely accurately.

(Effect of Embodiment 1)
As described above, in the projection display apparatus 1 of the present embodiment, the one having the uniform illumination optical element 3 is used as the illumination optical system, and the dichroic prism which is an axially symmetric optical element is used as the color synthesis optical system. I'm using Therefore, it is possible to realize a projection display device with less color unevenness and illuminance unevenness and high illumination efficiency. In addition, since a color synthesis system including a dichroic prism is used, the focal length of the projection lens can be shortened, and a large-screen display can be performed at a short distance. Therefore, if the configuration of this example is applied to a rear projector, the depth can be shortened, and the device can be made compact.

  In addition, since the focal lengths of the intermediate lens, the entrance lens, and the exit lens, which are the optical elements constituting the light guide system, are set to appropriate values, the occurrence of color unevenness of the color light beam passing therethrough and the loss of light amount This can also reduce the occurrence of color unevenness and illuminance unevenness of the projected image, and can form a bright image.

  Furthermore, when the configuration in which the incident lens and the condenser lens in the light guide system are adopted is adopted, the number of constituent elements can be reduced, so that the optical system can be made compact and inexpensive. When the integrated lens is an aspherical lens, the optical system can be made compact and the spherical aberration can be reduced.

  On the other hand, in this example, the number of divisions in the uniform illumination optical element is in the range of 3 to 7, and the pixel pitch of the liquid crystal panel is set to 50 μm or less. Generation can be suppressed, and therefore, a projection display device that can form a projection image with high image quality can be realized.

FIG. 11 shows a projection display apparatus according to Embodiment 2 of the present invention. The projection display apparatus 100 of the present embodiment is the same as the projection display apparatus 1 of the first embodiment except for the configuration of the light guide system. Therefore, corresponding portions are denoted by the same reference numerals, and description thereof will be omitted.

  The light guide system 9E in the projection display device 100 of the present example includes a triangular prism 901 on the incident side, a triangular prism 902 on the exit side, and a quadrangular prism 903 arranged therebetween.

  The operation of the light guide system 9E of this example will be described with reference to FIG. The light beam collimated by the condenser lens 103 is perpendicularly incident on the incident surface 904 of the triangular prism 901, is reflected by the total reflection surface 905, and exits from the exit surface 906. The total reflection surface 905 may be simply a glass or plastic optical flat surface. However, when the incident light beam includes a light beam having an angle that is not totally reflected, it is preferable to coat a metal film such as aluminum or silver. Instead, a dielectric multilayer reflective film may be coated. As shown in the drawing, the entrance surface 904 and the exit surface 906 have a function of guiding light by total reflection, and therefore need to be an interface between air and a glass material, and cannot be bonded to an adjacent optical element. Therefore, all five surfaces of the triangular prism 901 need to be optically flat surfaces, and in some cases, it is necessary to apply an anti-reflection coating to the entrance surface 904 and the exit surface 906. In particular, it is preferable to apply an anti-reflection coating to the interface with the adjacent quadrangular prism 903.

  The square prism 903 has optical flat surfaces on all six surfaces, and the four surfaces 907 parallel to the main axis of the passing light beam guide the light beam by total reflection. The exit-side triangular prism 902 has the same configuration as the incident-side triangular prism 901. The emitted light beam enters the display unit 5A of the liquid crystal panel 5G.

  In order to increase the light flux transmission rate, the shape of the entrance surface 904 of the triangular prism 901 and the shape of the exit surface of the triangular prism 902 are made substantially the same as the rectangular shape of the display unit 5A of the liquid crystal panel 5G. Here, the uniform illumination optical element 3 of the illumination optical system includes, as shown in FIG. 3, first and second lens plates 31 and 32 in which rectangular lenses are arranged in a matrix. Therefore, the incident surface 904 of the triangular prism 901 on the incident side is almost uniformly illuminated according to its rectangular shape. The three prisms are transmitted to the display unit 5A of the liquid crystal panel 5G while maintaining the amount of incident light flux, the parallelism, and the uniform brightness distribution. The emission-side triangular prism 902 and the liquid crystal panel 5G need to be arranged close to each other, but if there is a distance that cannot be ignored, a prism or lens for guiding light may be additionally arranged.

  With the projection display device of the present embodiment configured as described above, the same effects as those of the first embodiment can be obtained. Note that, instead of the square prism 903 of the light guide system in the present example, for example, a cylindrical light guide member formed by combining four reflecting mirrors may be used.

  Note that the square prism 903 in FIG. 11B may be a cylindrical light guide system including four reflecting mirrors 903 'as shown in FIG. 12A. Although the reflectance of the light guide surface is slightly lower, the function is the same. Further, as shown in FIG. 12B, the light guide system may be constituted by two upper and lower reflectors 911 and 912 and two reflectors 913 and 914 for bending the optical path. In this case, the incident light beam cannot be transmitted without loss, but the loss amount can be reduced by shortening the focal length of the lens 103 somewhat. In this case, since the illuminance distribution cannot be preserved, this method is suitable for a uniform illumination optical element using a cylindrical lens as shown in FIG.

FIG. 16 shows a projection display apparatus according to Embodiment 3 of the present invention. The projection display apparatus 500 of this example is the same as the above-described first embodiment except for the configuration of the light guide system. Therefore, corresponding portions are denoted by the same reference numerals, and description thereof will be omitted.

The light guide system 9F in the projection display device 500 of the present example includes a field lens 921 on the incident side, a field lens 922 on the exit side, and a concave mirror 923.
The condenser lens 103 near the entrance of the light guide system 9F and the field lens 921 can be integrated and replaced with a single lens.

  A light guide system 9G having this configuration is shown in FIG. The integrated lens 924 is composed of an eccentric biconvex lens as shown in the figure.

  FIG. 18A shows a specific configuration of the light guide system 9F. Assuming that the distance between the concave mirror 923 at the center of the optical path and the field lens 921 or the field lens 922 is a, the focal length of the concave mirror 923 is substantially equal to a / 2. The curved shape of the concave mirror 923 is a spherical surface or an elliptical surface. Therefore, the concave mirror 923 forms an image of the object 802 at the incident portion on the emission portion as a reflected image 803, and in fact, the illuminance distribution at the incidence portion is inverted and output at the emission portion. The focal lengths of the field lenses 921 and 922 are equal to a, and the optical axis 801 of each lens coincides with the center of both. The incident-side field lens 921 collects the parallel light flux from the condenser lens 103 at the center of the concave mirror 923. The emission-side field lens 922 refracts the light beam reflected from the concave mirror 923 so as to be a light beam perpendicular to the liquid crystal panel 5G.

  Note that the light guide system 9F can be configured as shown in FIG. In the light guide system 9H shown in this figure, the two field lenses 921 and 922 in the light guide system 9E described above are constituted by a single lens 806, and the concave mirror 923 is replaced with a plane mirror 804. 2 distance. Further, a plane mirror 805 is arranged perpendicular to the optical axis 807 of the lens 806. The parallel light beam incident on the light guide system 9H passes through the end of the lens 806, is reflected by the plane mirror 804, and converges at the center of the plane mirror 805. The light beam reflected from the plane mirror 805 is reflected by the plane mirror 804, passes through the end of the lens 806, and vertically enters the display unit 5A of the liquid crystal panel 5G. It is the center of the lens 806 that forms the image of the object 802 at the entrance as an inverted image 803 of the exit, and the light beam passes through the center of the lens 806 twice. It is the same as having passed. The configuration of this example has an advantage that the size is smaller than in the case of the above-described light guide system 9F.

FIG. 13 shows a projection display apparatus according to Embodiment 4 of the present invention. The projection type display device 200 of this embodiment is devised to compactly store the optical system in its case 201. The optical system in this example includes an illumination optical system 2B, a color separation optical system 4, light bubbles 5R, 5G, and 5B, a color combining optical system 6, a projection lens 7, and a light guide system 9D. . Among them, the color separation optical system 4, the light valves 5R, 5G, 5B, the color combining optical system 6, and the projection lens 7 are the same as those in the device 100 of the first embodiment. The light guide system 9D is the same as that shown in FIG. Therefore, corresponding portions in these portions are denoted by the same reference numerals, and descriptions of those portions will be omitted.

In the apparatus 200 of the present example, in order to make the central axis 1a of the light emitted from the illumination optical system 2B and the optical axis 7a of the projection lens 7 parallel, the illumination optical system 2B uses Is bent at a right angle.
The illumination optical system 2B has a configuration including a polarization conversion system 11.

  That is, the illumination optical system 2B of the present example includes the light source 2 including the lamp 21 and the reflecting mirror 22, the polarization conversion element 11 disposed on the output side, and the uniform illumination optical element 3A disposed on the output side. ing.

  As shown in FIG. 14, the polarization conversion element 11 of the present example includes a polarization beam splitter 111, a reflecting mirror 112, and a λ / 2 phase difference plate 113. The random polarized light 114 emitted from the light source 2 is separated into two linearly polarized lights of P-polarized light 115 and S-polarized light 116 by a polarization beam splitter 111 which is a polarization separation element. Since the polarization splitting function of the polarization beam splitter 111 has an incident angle dependence, a light source provided with a lamp having a short arc length capable of emitting light with excellent parallelism is suitable. The separated P-polarized light 115 passes through the λ / 2 retardation plate 113, which is a polarization plane rotation element, so that the polarization plane is rotated 90 degrees to become S-polarized light. On the other hand, the S-polarized light 116 is merely bent in its optical path by the prism-type reflecting mirror 112 and is emitted as it is as S-polarized light. In this example, the reflecting mirror 112 is formed as, for example, an evaporated film of aluminum and has a higher reflectance of S-polarized light than P-polarized light. Therefore, the reflecting mirror 112 bends the optical path of S-polarized light. As the reflecting mirror 112, besides the prism type, a general flat type reflecting mirror may be used. By passing through the polarization conversion element 11 having this configuration, the random polarized light 114 from the light source is emitted as S-polarized light. In this example, the P-polarized light is converted to the S-polarized light. However, the S-polarized light may be converted to the P-polarized light, and the P-polarized light may be emitted from the polarization conversion element 11.

  Next, the uniform illumination element 3A arranged on the emission side of the polarization conversion element 11 has a first lens plate 31 arranged on a plane perpendicular to the main axis of the emitted S-polarized light 116, and a first lens plate 31 orthogonal to the first lens plate 31. A second lens plate 32 is disposed in a state of being bent, and a reflecting mirror 33 is disposed between the lens plates 31 and 32 to bend the optical path at a right angle. The configurations of the first lens plate and the second lens plate are the same as those in the first embodiment. As described above, the light beam incident on the uniform illumination element 3A is bent at a right angle, and exits therefrom. The emitted white S-polarized light beam is separated by the color separation optical system 4 into primary color light beams. The separated light beams of the respective colors are combined in a color combining optical system 6 composed of a dichroic prism, and are enlarged and projected on a screen 8 via a projection lens 7.

  As described above, in the device 200 of the present example, the optical path is formed so that the direction of the projection light is parallel and opposite to the emission direction of the illumination optical system 2B, and the case on the rear side of the light source 2 is formed. Inside 201, a cooling fan 12 for suppressing heat generation by the light source lamp 21 is arranged.

  Therefore, in the apparatus 200 of this example, during use, the warm air used for cooling is discharged in the same direction as the projection light. For this reason, when the projection display device is a front projection type and an image is displayed and observed on a reflective screen, the observer is usually behind the device. Therefore, there is an advantage that the viewing of the observer is not hindered by the noise of the cooling fan or the warm air blown out therefrom. In addition, even in a case where the apparatus is installed in a place where the installation space is relatively small, such as an audio rack, since the air is exhausted from the front, there is no problem that the exhaust is trapped in the surroundings, which is convenient.

  Further, in the device 200 of this example, the illumination optical system 2B includes the polarization conversion element 11. Therefore, the randomly polarized light emitted from the light source is converted into a specific linearly polarized light, and the two light beams after the conversion are effectively superimposed and coupled with almost no divergence loss and emitted. Therefore, a bright illumination optical system that emits only polarized light with high efficiency can be realized. Further, in this example, since the emitted polarized light beam is passed through the uniform illumination optical element 3A, color unevenness and illuminance unevenness generated in the light source are suppressed, and illumination light with high uniformity can be obtained. it can.

5. As described above, the projection display apparatus according to the embodiment includes a uniform illumination optical element in the illumination optical system, a dichroic prism in the color synthesis system, and a color separation system. In the light path of the color light beam having the longest light path length, a light guide system is arranged, and the divergent light beams of each color separated through the color separation system are irradiated to the light valve as parallel light beams through the condenser lens. The above configuration is adopted. Therefore, the uniform illumination optical element suppresses color unevenness and illuminance unevenness of the light from the light source, and the color synthesizing system is a prism synthesizing system that generates less color unevenness and illuminance unevenness than the mirror synthesizing system. The occurrence of uneven color and the like is small. In addition, light of a color light beam having a long optical path length is transmitted through the light guide system in a state where there is almost no light amount loss, and a parallel light beam is irradiated to the light valve by the condenser lens, so that the light amount loss is small and the lighting efficiency is reduced. Is improved. Therefore, according to the above-described embodiment, it is possible to realize a projection display device with less color unevenness and illuminance unevenness and higher illumination efficiency than the related art.

  In the above embodiment, the focal length of the lens which is a component of the light guide system is set to an appropriate value, or a prism is used as the light guide system. According to this configuration, since color unevenness and light amount loss in the light guide system can be suppressed, a projected image with less color unevenness and high illumination efficiency can be formed.

  Further, in the above embodiment, a dichroic prism, which is a rotationally symmetric element with respect to the central axis of the projection optical system, is used as a color synthesis system, and a liquid crystal panel having a small pitch of about 50 μm or less is used as a light valve. are doing. Therefore, according to the above embodiment, a projection image with high resolution can be formed, and the entire device can be reduced in size using a liquid crystal panel such as a polysilicon TFT, which can be easily reduced in size.

  Further, in the above embodiment, since the number of divisions of the lens plate constituting the uniform illumination optical element is set in the range of 3 to 7, it is possible to form a projection image in which color unevenness is suppressed.

  Further, in the above embodiment, since the configuration in which the illumination optical system includes the polarization conversion element is employed, the divergence loss of the luminous flux emitted from the light source lamp can be suppressed, and a bright projection image can be formed.

  On the other hand, in the projection display device of the present invention, an optical path is configured so that the projection light can be emitted in a direction parallel to the direction of the light emitted from the illumination optical system in a direction opposite to the direction in which the projection light is emitted. A configuration in which cooling means for a light source lamp is disposed on the side of the device case to be used. According to this configuration, when used as a front projector, the cooling means is located on the side opposite to the side where the observer of the projected image is located, and exhaust air therefrom blows to the side opposite to the observer. Be sent out. Therefore, there is an advantage that the noise of the cooling means and the exhaust air therefrom do not disturb the observer.

  On the other hand, according to the above-described embodiment, in addition to the above-described respective effects, since the back focus of the projection lens of the optical system is short, large-screen projection over a short distance is easy. Therefore, a projection display device suitable for presentation use and home theater use at home can be realized. Also, since the back focus of the projection lens is short, a bright F-number and a small projection lens can be realized with a small number of lenses, and the cost of the apparatus can be reduced.

FIG. 1 is a schematic configuration diagram illustrating a configuration of an optical system of a projection display apparatus according to a first embodiment of the present invention. 4 is a graph showing a relationship between a pixel density and a transfer characteristic (MTF) of a liquid crystal panel used as a light valve in a projection display device. FIGS. 2A and 2B are schematic perspective views showing the configurations of first and second lens plates constituting the uniform illumination optical element of FIG. 1, respectively. FIG. 2 is a schematic perspective view illustrating a configuration of first and second lens plates constituting the uniform illumination optical element of FIG. 1. 5 is a graph showing the relationship between the number of divisions of a lens plate of a uniform illumination optical element and color unevenness. (A) and (B) are explanatory views for explaining the function of a uniform illumination optical element. It is a schematic structure figure showing a modification of a light guide system in Example 1 of the present invention. (A) and (B) are a schematic block diagram showing another modification of the light guide system in the first embodiment of the present invention, and an explanatory diagram showing the operation thereof. FIGS. 6A and 6B are a schematic configuration diagram showing still another modified example of the light guide system according to the first embodiment of the present invention, and an explanatory diagram showing its operation. It is a schematic block diagram which shows the modification of the light guide system shown to FIG. 9 (A). 1A and 1B are a schematic configuration diagram showing an optical system of a projection display apparatus according to an embodiment of the present invention, and an explanatory diagram showing a light guide system thereof. (A) and (B) are explanatory views showing a modification of FIG. 11 (B). FIG. 9 is a schematic configuration diagram illustrating an optical system and a cooling fan of a projection display device according to a fourth embodiment of the present invention. FIG. 14 is an explanatory diagram illustrating a configuration of a polarization conversion element incorporated in the illumination optical system of FIG. 13. FIG. 4 is a schematic configuration diagram illustrating a modification of the uniform illumination optical element in FIG. 1. FIG. 9 is a schematic configuration diagram illustrating a projection display device according to a third embodiment of the present invention. FIG. 9 is a schematic configuration diagram illustrating a modification of the projection display device according to the third embodiment of the present invention. (A) is an explanatory view showing the light guide system of FIG. 16. FIG. 19B is an explanatory view showing a modification of the light guide system shown in FIG.

Claims (8)

A light source; a color separation unit that separates a white light beam emitted from the light source into light beams of three colors; three light valves that modulate the light beams of the separated colors; and a light valve that is separated by the color separation unit. Among the light beams of each color incident on each of the light valves, a light guide unit disposed on the optical path of the light beam having the longest optical path length, and a color for synthesizing the modulated light beam of each color modulated via the light valve In a projection display device having a combining unit and a projection lens that projects the combined modulated light beam on a screen,
Uniform illumination optical means interposed in the optical path between the light source and the color separation means, converts the white light flux from the light source into a uniform rectangular light flux and emits the light toward the color separation means,
And three condensing lenses that are respectively arranged in the light beam emitting units that emit light beams of the respective colors in the color separation unit and convert the divergent light beam from the uniform illumination optical unit into a substantially parallel light beam.
The color combining means is a dichroic prism,
The projection display device, wherein the color light passing through the light guide is green light.   2. The projection display device according to claim 1, wherein the light guide unit includes an incident-side reflecting mirror, an emitting-side reflecting mirror, and at least one lens.   The light guide means according to claim 1, wherein the light guide means is disposed on an incident side and bends an optical path by 90 degrees, an output side triangular prism is disposed on an outgoing side and bends an optical path by 90 degrees, and A projection display device comprising: a light guide member disposed therebetween.   4. The projection display device according to claim 1, wherein the light valve is a liquid crystal panel, and a pixel pitch of the liquid crystal panel is about 50 μm or less.   5. The uniform illumination optical unit according to claim 1, wherein the uniform illumination optical unit includes at least one lens plate having a configuration in which a plurality of lenses are arranged in a plane perpendicular to a main axis of output light of the light source. A projection type display device comprising:   6. The projection display device according to claim 5, wherein the number of lens divisions in one direction in the lens plate is between about 3 and about 7.   7. The uniform illumination optical unit according to claim 1, wherein the uniform illumination optical unit includes a first lens plate, a second lens plate, and a reflecting mirror interposed therebetween. Projection type display device. In any one of claims 1 to 7, the uniform illumination optical unit further includes a polarization conversion unit, and the polarization conversion unit converts random polarized light from the light source into a P wave and an S wave. A projection display device, comprising: a polarization separation element that separates two linearly polarized lights; and a polarization plane rotation element that matches the polarization planes of the two separated polarized lights.

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