JP3613256B2 - Projection display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention separates the luminous flux from the light source into three color luminous fluxes of red, blue and green, modulates each of these colored luminous fluxes according to the video information through the modulation means, and re-modulates the modulated luminous flux of each color after modulation. The present invention relates to a projection display device that combines and projects an enlarged image on a screen via a projection lens.
[0002]
[Background]
The projection display device includes a light source lamp, color separation means for separating the light flux from the light source into three color light fluxes, three light valves for modulating the separated three color light fluxes, and It comprises color synthesizing means for recombining the color beams and a projection lens for enlarging and displaying the light image obtained by the synthesis on the screen. A liquid crystal panel is generally used as the light valve.
[0003]
As a conventional projection type display device having this configuration, a light source portion in which a uniform illumination optical element called an optical integrator is incorporated is known. For example, U.S. Pat. No. 5,098,184 discloses a projection display device incorporating this optical integrator. In addition, this publication describes a configuration in which dichroic mirrors are arranged in an X shape as color combining means. Usually, it is composed of a dichroic mirror in which a dielectric multilayer film is formed on a glass plate.
[0004]
As described above, the projection display apparatus having the mirror composition system in which the color composition means is constituted by the dichroic mirror has the following problems. That is, the dichroic mirror is a non-rotationally symmetric optical element with respect to the central 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 lowered. The deterioration of the MTF characteristics is not so much a problem when the size of the liquid crystal panel is large with respect to the number of pixels, that is, when the pixel pitch is large. However, if the pixel pitch becomes small as in the case of a liquid crystal panel using a polysilicon TFT as a switching element, it cannot be ignored.
[0005]
Further, as a conventional projection display device, a type having a prism composition system in which a color composition 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 this prism can be easily removed by designing the projection lens. In general, the MTF characteristic in the projection display device having the prism synthesis system includes the mirror synthesis system described above. It is superior to that. Therefore, it is suitable when a liquid crystal panel having a small pixel pitch is used as a light valve.
[0006]
Further, as a conventional projection display device, for example, there is one disclosed in US Pat. No. 4,943,154. This apparatus is configured to suppress a reduction in light quantity and color unevenness by interposing a light transmission means composed of a relay lens, a field lens, etc. in the optical path of the color light having the longest optical path length.
[0007]
However, in this apparatus, although the light amount of the color light having the longest optical path length is not reduced, the brightness distribution of the light beam is rotated by 180 degrees by the relay lens, so when 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 axially symmetric, such color unevenness will not occur, but in reality, it is caused by a shift in the mounting position of the light source lamp and a slight asymmetry of the light source lamp and its reflecting mirror. In general, the brightness distribution is non-axisymmetric.
[0008]
Here, in the projection display device, it is desired to increase the illuminance of the projected image, eliminate the unevenness in color and illuminance, and obtain an image quality close to that of a CRT direct view image. For this purpose, it is preferable to use a prism synthesis system with good transfer characteristics as the color synthesis system. In addition, it is preferable to illuminate the liquid crystal panel with uniform brightness and efficiency by using an optical integrator for the light source portion. However, if 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 amount of color light allocated to the longest optical path will decrease, and the change in illuminance distribution will become noticeable. Appears as an uneven color or a change in color temperature in the image. For this reason, the effect of an integrator cannot fully be exhibited. Furthermore, when an optical integrator is used for the light source portion, the conventional technology cannot be used as it is. In other words, in illumination using an optical integrator, divergent light from a surface light source existing at a finite position (light emission surface of the integrator) from the liquid crystal panel illuminates the liquid crystal panel. This is because it is fundamentally different from the case where it can be regarded as illumination from a point light source existing in.
[0009]
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, uneven color, etc., as compared with the conventional projection display device described above.
[0010]
Another object of the present invention is to propose an inexpensive projection display device capable of forming a high-quality projection image.
[0011]
Furthermore, an object of the present invention is to propose a projection display device capable of forming a projected image with higher illuminance than in the prior art.
[0012]
Still another object of the present invention is to propose a compact projection display device capable of forming a high-quality projection image.
[0013]
Furthermore, another object of the present invention is to propose a projection display device having a configuration suitable for use as a front projection type.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, a projection display device according to the present invention includes a light source, color separation means for separating a light beam emitted from the light source into three color light beams, and modulating light beams of each separated color. Of the light beams of the respective colors separated by the color separation means and incident on the three modulation means, the color separation means of the light flux having a longer optical path length than the other color light, and the modulation means A light guide unit disposed on an optical path between them, a color combining unit that combines the modulated light beams of the respective colors modulated via the modulation unit, and a projection lens that projects the combined modulated light beam on the screen. In the projection display apparatus, a uniform illumination optical unit that is inserted in an optical path between the light source and the color separation unit, converts a light beam from the light source into a uniform rectangular light beam, and emits the light toward the color separation unit. In the color separation means Each of the three condensing lenses disposed in the light beam emitting section for emitting the color light flux and converting the divergent light flux from the uniform illumination optical means into a substantially parallel light flux. Among these, the condensing lens disposed in the light beam emitting portion of the light beam having a longer optical path length than the other color light of the color separation means emits the substantially parallel light beam toward the light guide means, and further, the color Combining means comprises a dichroic prism, and as the light guiding means, an incident side triangular prism that is arranged on the incident side and bends the optical path by 90 degrees, an output side triangular prism that is arranged on the output side and bends the optical path by 90 degrees, and these It is characterized by adopting a structure including a light guide member disposed between the triangular prisms. In the projection display device of the present invention having this configuration, the modulation means is illuminated using the uniform illumination optical means, and a condensing lens is arranged in the optical path of each color light to make the divergent light beam into a parallel light beam. The colored light is passed through the light guide means. Therefore, according to the present invention, it is possible to form a projected image with a uniform illuminance distribution, no color unevenness, and brighter and higher quality than the conventional one.
[0015]
Here, it is preferable that the shapes of the incident surface of the incident side triangular prism and the output surface of the output side triangular prism are substantially the same as the shape of the display unit of the modulation means, and a rectangular prism is used as the light guide member. it can. The incident side triangular prism, the square prism, and the output side triangular prism are respectively between the exit surface of the incident side triangular prism and the incident surface of the square prism, and between the exit surface of the square prism and the entrance of the output side triangular prism. It is preferable that there is a gap between the surface and the non-reflective coating is preferably applied to the interface between the triangular prism and the quadrangular prism. Furthermore, it is preferable to coat the total reflection surface of the triangular prism with a metal film or a dielectric multilayer film.
[0016]
Next, a liquid crystal panel can be used as the modulation means. In this case, it is preferable to increase the definition of the projected image by setting the pixel pitch of the liquid crystal panel to about 50 μm or less.
[0017]
On the other hand, as the uniform illumination optical means, it is possible to adopt a configuration having at least one lens plate having a configuration 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. In this case, the number of lens divisions in one direction on the lens plate is preferably between about 3 and about 7.
[0018]
In general, it is preferable that the color light passing through the light guide unit is green light having a larger light quantity than other color lights. Alternatively, it is preferable that the color light that passes through the light guide unit is blue light that is relatively inconspicuous in the influence on the image quality due to the change in the light amount.
[0019]
Here, as the uniform illumination optical means, the first lens plate, the second lens plate, and the reflecting mirror interposed between them may be provided, and the optical path may be bent, for example, at a right angle. .
[0020]
Furthermore, 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 that separates random polarization from the light source lamp into two linear polarizations of P wave and S wave, and a polarization plane rotation element that matches the polarization planes of the two separated polarizations. The If this polarization conversion means is used, the utilization efficiency of the light emitted from the light source lamp can be increased, and the illuminance of the projected image can be increased accordingly.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0022]
1. Reference example
FIG. 1 shows an optical system of a projection display device according to a reference example of the present invention. The projection display device 1 of this example includes an illumination optical system 2A composed of a light source 2, a uniform illumination optical element 3, and a light beam W emitted from the illumination optical system 2A via the uniform illumination optical element 3. A color separation optical system 4 that separates red, green, and blue color beams R, G, and B, three liquid crystal panels 5R, 5G, and 5B as light valves that modulate the color beams, and a modulated color beam. A color synthesizing optical system 6 for recombining and a projection lens 7 for enlarging and projecting the synthesized light flux on a screen 8 are provided. Moreover, it has the light guide system 9 which guides the green light beam G to the corresponding liquid crystal bulb 5G among the color light beams separated by the color separation optical system 4.
[0023]
The light source 2 of this example includes a light source lamp 21 and a curved reflecting mirror 22, and a halogen lamp, a metal halide lamp, a xenon lamp, or the like can be used as the light source lamp 21. Although the details of the uniform illumination optical system 3 will be described later, the uniform illumination optical system 3 includes a first lens plate 31 and a second lens plate 32 disposed on a plane perpendicular to the central optical axis 1a of the illumination optical system.
[0024]
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. First, in the blue-green reflecting dichroic mirror 401, the blue light beam B and the green light beam G contained therein are reflected at right angles, and the light beam W is directed toward the blue reflecting 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 beam emitting portion 404 to the color synthesis optical system side. The blue and green light beams B and G reflected by the mirror 401 are reflected by the blue reflection dichroic mirror 402 only at a right angle, and emitted from the blue light beam emitting portion 405 to the color synthesis optical system side. The The green light beam G that has passed through the mirror 402 is emitted from the green light beam emitting portion 406 toward the light guide system 9. In this example, the distances from the light beam emitting portions of the uniform illumination optical element 3 to the light beam emitting portions 404, 405, and 406 of each color light beam in the color separation optical system 4 are all set to be equal. Here, in this example, condensing lenses 101, 102, and 103 each including a plano-convex lens are disposed on the emission side of the emission portions 404, 405, and 406 of each color light beam of the color separation optical system 4, respectively. Therefore, each color light beam emitted from each emission part is incident on these condenser lenses 101 to 103 and is collimated.
[0025]
Of the color beams R, G, and B after being collimated, the red and blue light beams R and B are incident on the liquid crystal panels 5R and 5B disposed immediately after the condenser lenses 101 and 102 and modulated. Video information corresponding to each color light is added. That is, in these liquid crystal panels, switching control is performed in accordance with video information by a driving unit (not shown), thereby modulating each color light passing therethrough. As such driving means, known means can be used as they are, and description thereof is omitted in this example. On the other hand, the green light beam G is guided to the corresponding liquid crystal panel 5G through the light guide system 9, and is similarly modulated according to the video information. The liquid crystal panel of this example uses a TFT having a pixel pitch of 50 μm or less using a polysilicon TFT as a switching element.
[0026]
The light guide system 9 in this example includes an incident-side reflecting mirror 91, an emitting-side reflecting 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. The 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, the green light beam G is the longest, and therefore the light amount loss of this light beam is the largest. However, the light loss can be suppressed by interposing the light guide system 9 as in this example. The color light beam that passes through the light guide system 9 may be a red or blue light beam. However, generally, in a normal projection display device, the amount of green light is larger than the amount of light of other colors, so it is preferable to assign the green light beam to the optical path passing through the light guide system 9. However, when priority is given to brightness and uniformity of image quality over color balance, a blue luminous flux with low visibility and relatively less noticeable illuminance unevenness may be assigned to the light guide system 9.
[0027]
Next, each color beam modulated through the respective liquid crystal panels 5R, 5G, and 5B is incident on the color synthesis 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 synthesis optical system 6, a mirror synthesis system having a configuration in which dichroic mirrors are arranged in an X shape can be used. However, in a projection display device having a mirror composition system in which the color composition optical system is configured by a dichroic mirror, the dichroic mirror is a non-rotationally symmetric optical element with respect to the central 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 lowered. The deterioration of the MTF characteristics is not so much a problem when the size of the liquid crystal panel is large with respect to the number of pixels, that is, when the pixel pitch is large. However, if the pixel pitch is small as in the case of 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 synthesis optical system 6, it is possible to avoid such an adverse effect.
[0028]
This point will be described with reference to FIG. This figure shows the MTF characteristics of the projection display apparatus having the prism composition system of this example and the projection display apparatus when the color composition system is a mirror composition system. In this figure, the horizontal axis represents the spatial frequency (1ine / mm) indicating the fineness of the pixels of the liquid crystal panel, and the vertical axis represents MTF (%). A solid line is a characteristic in a projection optical system including a prism synthesis 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 is a characteristic in the projection optical system provided with the mirror composition system. A thick broken line is a characteristic at the center of the screen, and a thin broken line is a characteristic at the periphery.
[0029]
The MTF characteristic of the projection lens alone is deteriorated due to astigmatism because the mirror is inserted at an angle of 45 degrees in the mirror synthesis 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 at a spatial frequency of 20 (1 in / mm). However, when the mirror synthesis 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 the prism synthesis system is used as in this example, the aberration generated by the prism can be removed by the design of the projection lens, so that it is understood that there is no deterioration of the MTF characteristics.
[0030]
In the apparatus of this example, light beams of respective colors are synthesized in a color synthesis system composed of a dichroic prism to obtain an optical image, and this optical image is enlarged and projected on the screen 8 by the projection lens 7. A projection lens that is close to a telecentric system is preferable.
[0031]
(Illumination optics)
As an example of the uniform illumination optical element 3 in the illumination optical system of this example, there is an integrator lens generally used in an exposure machine. FIG. 3A shows a basic configuration when used in a projection display device. As shown in this figure, the uniform illumination optical element 3 includes 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 image of each rectangular lens 301 is superimposed and formed on the liquid crystal panel by the corresponding rectangular lens of each rectangular lens 302 constituting the second lens plate 32. Therefore, the liquid crystal panel is illuminated with uniform illuminance and almost no color unevenness.
[0032]
In this example, rectangular lenses are arranged in each of the lens plates 31 and 32 so as to form a 4 × 3 matrix. The maximum number of divisions in the vertical or horizontal direction is preferably in the range of about 3 to 7. The first lens plate 31 and the second lens plate 32 are not necessarily separated. By reducing the size of each rectangular lens and increasing the number of divided incident light beams, the lens plates 31 and 32 can be brought closer to each other. Furthermore, it is possible to integrate a single lens.
[0033]
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 represents the number of divisions of the first and second lens plates (integrator lenses), the vertical axis represents color unevenness, and the central portion (one place) and the peripheral portion (4 on the screen 8). The difference in color between the two points is displayed as a difference on the U′V ′ chromaticity coordinates. The smaller the value indicating the color unevenness, the smaller the color unevenness. In the figure, the value indicated by the broken line is the maximum color unevenness determined to be acceptable as color unevenness.
[0034]
As can be seen from this graph, the number of divisions is preferably 3 or more. However, from the viewpoint of manufacturing, increasing the number of divisions leads to high costs. Therefore, a practical number of divisions ranges from about 3 to about 7.
[0035]
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 composed of rectangular lens plates 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 four. It is divided.
[0036]
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 using and configuring. The illuminance in this case is made uniform only in one direction, and the central illuminance of the illumination target is higher than in the cases of FIGS. In this case, since the lens configuration is relatively simple, it is easy to reduce the thickness.
[0037]
Next, with reference to FIG. 6 (A), the effect | action in illuminating liquid crystal panel 5R, 5G, 5B using the uniform illumination optical element 3 of said structure is demonstrated. As the light source lamp 21 constituting the light source 2, as described above, a light emitting source close to a point such as a halogen lamp, a metal halide lamp, or a xenon lamp is used. Also, 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, and in this case, the first focus is made to coincide with the light emitting part of the light source lamp 21, and the second focus is set to the liquid crystal panel 5 (5R, 5G, 5B). Match the center position of. As a result, the reflected light beam of the reflecting mirror 22 goes toward the center of the liquid crystal panel 5. In this case, the second lens plate 302 is centered on the line extending from the center of each rectangular lens 301 of the first lens plate 31 toward the center of the liquid crystal panel 5. The size 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.
[0038]
Each rectangular lens 301 of the first lens plate 31 concentrates the light flux at 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 rectangular lens 301 on the side of the corresponding first lens plate on the display area 5A of the liquid crystal panel 5 (area shown by diagonal lines in the figure). Let me image. Since the image of the light emitting part 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. Accordingly, 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 illumination light flux 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 the parallel light incident on the liquid crystal panel 5. For this purpose, condensing lenses 101, 102, and 103 are arranged in this example. 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 disposed with a convex surface facing the liquid crystal panel 5 is used as the condenser lens. You may arrange | position in the state which orient | assigned the convex surface to the 2nd lens plate side. Instead of a plano-convex lens, a biconvex lens or a Fresnel lens can also be used. Thus, by arranging the condensing lenses 101, 102, 103, 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.
[0039]
Next, FIG. 6B shows a modification of the illumination optical system. In this example, a paraboloid is used as the reflecting surface of the reflecting mirror 22 of the light source 2. In this case, since the focal point of the paraboloid coincides with the light emitting portion of the light source lamp 21, the light beam reflected by the reflecting mirror 22 becomes a light beam 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 constituting each lens plate is also the same. 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, the lens 306 is added to form an image that should be infinite on the display area 5A of the liquid crystal panel 5. The focal length of the lens 306 is set to be equal to the distance between this lens and the liquid crystal panel 5. The lens 306 can also be integrated with the second lens plate 32.
[0040]
In addition, when the division | segmentation number by the rectangular lens of each lens plate 31 and 32 is comparatively small, the distance between each lens plate can be made comparatively large, and as FIG. 15 shows, between each lens plate, reflection is carried out. A mirror 33 can be interposed. In this case, there is an advantage that the volume occupied by the uniform illumination optical element is about ½ of the previous example. Further, as shown in this figure, the arrangement of all the optical systems can be made close to a square, contributing to the miniaturization of the entire apparatus.
[0041]
(Light guide system)
As described above, the light guide system 9 of this example 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 example will be described below.
[0042]
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.
[0043]
Next, in addition to the configuration of the light guide system 9 of this example, the light guide system 9B shown in FIG. 8A has an incident lens 94 added to the incident part side and an output lens 95 on the output part side. It is the structure which added.
[0044]
With reference to FIG. 8B, the operation of the light guide system 9B having this configuration will be described. In the drawing, for ease of explanation, the pair of reflecting mirrors 91 and 92 is shown as a straight line system. As shown in the figure, the intermediate lens 93 is located at the exact 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 approximately equal to a / 2. is there. Accordingly, the intermediate lens 93 forms an image of the object 96 on the incident side of the light guide system 9B as a reverse image 97 on the exit side of the light guide system. In other words, the illuminance distribution on the incident side is transmitted by rotating 180 degrees on the exit side. However, since the illumination optical system including the uniform illumination optical element 3 is used in this example, the illuminance distribution is almost symmetrical with respect to the rotation of 180 degrees. Therefore, even if the illuminance distribution is rotated or reversed in this way, display color unevenness does not occur.
[0045]
On the other hand, the incident lens 94 has the focal length equal to the distance a to the intermediate lens 93 and directs the principal ray 9 a of the light beam G that has passed through the condenser lens 103 and becomes 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 thereof 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 arranged so that the convex surface side faces the exit side.
[0046]
Note that the focal lengths of the entrance lens and the exit 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. The focal length of the intermediate lens is preferably slightly longer than ¼ of the total optical path length (2a) from the viewpoint of reducing spherical aberration, and is within a range of about 0.25 to about 0.4 times. Should be set.
[0047]
FIG. 9A shows a modification of the light guide system 9B. In the light guide system 9 </ b> C shown in this figure, the incident lens 94 in the light guide system 9 </ b> B is a lens 97 that is integrated with the condenser lens 103 disposed in front of the optical 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 lengths of the plano-convex lenses 931 and 932 are set to a. Further, by arranging the convex surfaces of the respective lenses so as to face each other, the spherical aberration can be extremely reduced as compared with the case of one biconvex lens. As a result, it is possible to transmit the illuminance distribution on the incident side of the light guide system to the emission side very accurately.
[0048]
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 aspherical lens 98. By using the aspherical lens 98 in this way, spherical aberration can be further reduced as compared with the case of using a biconvex lens. Therefore, it is possible to transmit the illuminance distribution on the incident side of the light guide system to the emission side very accurately.
[0049]
(Effect of reference example)
As described above, in the projection display apparatus 1 of the present example, an illumination optical system including the uniform illumination optical element 3 is used, and the color synthesis optical system includes a dichroic prism that is an axially symmetric optical element. I use it. Therefore, it is possible to realize a projection display device with little color unevenness and illuminance unevenness and high illumination efficiency. In addition, since a color composition system comprising a dichroic prism is used, the focal length of the projection lens can be shortened, and a large screen display at a short distance is possible. Therefore, if the configuration of this example is applied to a rear projector, the depth can be shortened, so that the apparatus can be made compact.
[0050]
In addition, since the focal lengths of the intermediate lens, incident lens, and output lens, which are optical elements that make up the light guide system, are set to appropriate values, the occurrence of color unevenness in the color light flux that passes through this lens and the loss of light quantity This can also reduce the occurrence of uneven color, uneven illuminance, and the like in the projected image, and it is possible to form a bright image.
[0051]
Furthermore, when the configuration in which the incident lens and the condenser lens in the light guide system are integrated is adopted, the number of components can be reduced, and accordingly, the optical system can be made compact and inexpensive. Further, when the integrated lens is an aspheric lens, the optical system can be made compact and the spherical aberration can be reduced.
[0052]
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. Therefore, it is possible to realize a projection display device that can suppress the occurrence and thus can form a projected image with high image quality.
[0053]
2. First embodiment
FIG. 11 shows a projection display apparatus according to the first embodiment of the present invention. The projection display device 100 of this example is the same as the projection display device 1 of the reference example described above except for the configuration of the light guide system. Accordingly, corresponding parts are denoted by the same reference numerals, and description thereof is omitted.
[0054]
The light guide system 9E in the projection display apparatus 100 of the present example includes an incident side triangular prism 901, an output side triangular prism 902, and a quadrangular prism 903 disposed therebetween.
[0055]
The function 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 incident on the incident surface 904 of the triangular prism 901 perpendicularly, is reflected by the total reflection surface 905, and is emitted from the emission surface 906. Total reflection surface 905 may simply be an optical flat surface made of glass or plastic. However, when the incident light beam includes a light beam having such an angle that it is not totally reflected, it is preferable to coat a metal film such as aluminum or silver. Alternatively, a dielectric multilayer reflective film may be coated. As shown in the figure, the incident surface 904 and the exit surface 906 have a light guiding function 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, the triangular prism 901 requires that all five surfaces be optically flat surfaces, and in some cases, it is necessary to apply a dereflection coating to the incident surface 904 and the output surface 906. In particular, an antireflection coating is preferably applied to the interface with the adjacent quadrangular prism 903.
[0056]
In the quadrangular prism 903, all of the six surfaces are optically flat surfaces, and the four surfaces 907 parallel to the principal axis of the light beam passing therethrough guide the light beam by total reflection. The triangular prism 902 on the output side has the same configuration as the triangular prism 901 on the incident side. The emitted light beam is incident on the display unit 5A of the liquid crystal panel 5G.
[0057]
In order to increase the transmissivity of the luminous flux, the shape of the incident surface 904 of the triangular prism 901 and the shape of the output 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 first and second lens plates 31 and 32 in which rectangular lenses are arranged in a matrix as shown in FIG. Accordingly, the incident surface 904 of the incident side triangular prism 901 is illuminated substantially uniformly according to the rectangular shape. The three prisms are transmitted to the display unit 5A of the liquid crystal panel 5G while maintaining the light quantity, parallelism, and uniform brightness distribution of the incident light flux. Although the triangular prism 902 on the emission side and the liquid crystal panel 5G need to be arranged close to each other, if there is a distance that cannot be ignored, a prism or lens for guiding light may be additionally arranged.
[0058]
With the projection display device of this example configured as described above, it is possible to obtain the same effect as that of the reference example described above. In addition, instead of the light guide quadrangular prism 903 in this example, for example, a light guide member formed into a cylindrical shape by combining four reflecting mirrors may be used.
[0059]
Note that the quadrangular prism 903 in FIG. 11B may be a cylindrical light guide system including four reflecting mirrors 903 ′ as shown in FIG. Although the reflectivity of the light guide surface is slightly lower, the function is the same. In addition, as shown in FIG. 12B, the light guide system may be composed of two upper and lower reflecting plates 911 and 912 and two reflecting mirrors 913 and 914 for bending the optical path. In this case, the incident light flux cannot be transmitted without loss, but the loss amount can be reduced by reducing the focal length of the lens 103 somewhat. In this case, since the illuminance distribution cannot be preserved, the method is suitable for a uniform illumination optical element using a cylindrical lens as shown in FIG.
[0060]
3. Second embodiment
FIG. 16 shows a projection display apparatus according to the second embodiment of the present invention. The projection display apparatus 500 of this example is the same as the reference example described above except for the configuration of the light guide system. Accordingly, corresponding parts are denoted by the same reference numerals, and description thereof is omitted.
[0061]
The light guide system 9 </ b> F in the projection display apparatus 500 of this example includes an incident-side field lens 921, an exit-side field lens 922, and a concave mirror 923. The condensing lens 103 in the vicinity of the incident portion of the light guide system 9F and the field lens 921 can be integrated and replaced with a single lens.
[0062]
A light guide system 9G having this configuration is shown in FIG. The integrated lens 924 is composed of a decentered biconvex lens as shown in the figure.
[0063]
A specific configuration of the light guide system 9F is shown in FIG. When the distance from the concave mirror 923 at the center of the optical path to 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 surface shape of the concave mirror 923 is a spherical surface or an elliptical surface. Accordingly, the concave mirror 923 forms an image of the object 802 at the incident portion as a reflected image 803 on the emission portion, and actually 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 axes 801 of the respective lenses coincide with each other at the center. 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 exit-side field lens 922 refracts the reflected light beam from the concave mirror 923 so as to be a light beam perpendicular to the liquid crystal panel 5G.
[0064]
Note that the light guide system 9F can also 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 are configured by a single lens 806, the concave mirror 923 is replaced with a plane mirror 804, and the lenses 806 to a / It is arranged at a distance of 2. Further, a plane mirror 805 is disposed perpendicular to the optical axis 807 of the lens 806. The parallel light flux incident on the light guide system 9H passes through the end of the lens 806, is reflected by the plane mirror 804, and gathers 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 enters the display unit 5A of the liquid crystal panel 5G perpendicularly. The image of the object 802 at the entrance is formed as the inverted image 803 of the exit at the center of the lens 806, and the light beam passes through the center of the lens 806 twice. It becomes the same as having passed. The configuration of this example has an advantage that the size is smaller than that of the light guide system 9F.
[0065]
4). Third embodiment
FIG. 13 shows a projection display apparatus according to the third embodiment of the present invention. The projection display apparatus 200 of the present example is devised for compactly storing the optical system in the 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 synthesis optical system 6, a projection lens 7, and a light guide system 9D. . Among these, the color separation optical system 4, the light valves 5R, 5G, and 5B, the color synthesis optical system 6, and the projection lens 7 are the same as those in the apparatus 100 of the reference example. The light guide system 9D is the same as that shown in FIG. Therefore, the same code | symbol is attached | subjected to the site | part corresponding in these parts, and description of those each site | part is abbreviate | omitted.
[0066]
In the apparatus 200 of this example, in order to make the central axis 1a of the emitted light from the illumination optical system 2B parallel to the optical axis 7a of the projection lens 7, the illumination optical system 2B includes the light source lamp 21. The direction of the emitted light is bent at a right angle. The illumination optical system 2B has a configuration including a polarization conversion system 11.
[0067]
That is, the illumination optical system 2B of this example is composed of the light source 2 composed of the lamp 21 and the reflecting mirror 22, the polarization conversion element 11 disposed on the exit side, and the uniform illumination optical element 3A disposed on the exit side. ing.
[0068]
As shown in FIG. 14, the polarization conversion element 11 of this 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 light 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 separation function of the polarization beam splitter 111 has an incident angle dependency, a light source provided with a short arc length lamp capable of emitting light with excellent parallelism is suitable. The separated P-polarized light 115 passes through a λ / 2 phase difference plate 113 which is a polarization plane rotation element, and thereby the polarization plane is rotated 90 degrees to become S-polarized light. On the other hand, the S-polarized light 116 is only 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, for example, as an evaporated film of aluminium, and has a higher reflectance of S-polarized light than that of P-polarized light. Therefore, the optical path of S-polarized light is bent by the reflecting mirror 112. As the reflecting mirror 112, in addition to 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, P-polarized light is converted to S-polarized light. Conversely, S-polarized light may be converted to P-polarized light, and P-polarized light may be emitted from the polarization conversion element 11.
[0069]
Next, the uniform illumination element 3A disposed on the exit side of the polarization conversion element 11 includes a first lens plate 31 disposed on a plane perpendicular to the main axis of the emitted S-polarized light 116, and orthogonal thereto. The second lens plate 32 is disposed in a state where the optical path is formed, and the reflecting mirror 33 is disposed between the lens plates 31 and 32 and bends the optical path at a right angle. The configurations of the first lens plate and the second lens plate are the same as in the reference example. Thus, the light beam incident on the uniform illumination element 3A is bent at a right angle and emitted from here. The emitted white S-polarized light beam is separated into a primary color light beam by the color separation optical system 4. The separated light fluxes of the respective colors are combined in a color combining optical system 6 composed of a dichroic prism, and enlarged and projected onto a screen 8 via a projection lens 7.
[0070]
Thus, in the apparatus 200 of this 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 back side of the light source 2 is formed. In 201, a cooling fan 12 for suppressing heat generation by the light source lamp 21 is arranged.
[0071]
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 on a reflection screen for observation, the observer is usually behind the device. Therefore, there is an advantage that the viewer's viewing is not hindered by the noise of the cooling fan or the warm air blown from the noise. Also, when installing in a place where there is relatively little room for installation, such as an audio rack, since the exhaust is from the front, there is no problem that the exhaust is confined to the surroundings.
[0072]
Moreover, in the apparatus 200 of this example, the illumination optical system 2B includes the polarization conversion element 11. Therefore, the random polarized light emitted from the light source is converted into the specific linearly polarized light, and the two converted light beams are effectively superimposed and output with almost no divergence loss. Therefore, a bright illumination optical system that emits only polarized light with high efficiency can be realized. Furthermore, in this example, since the emitted polarized light beam is allowed to pass through the uniform illumination optical element 3A, color unevenness and illuminance unevenness generated in the light source are suppressed, and highly uniform illumination light can be obtained. it can.
[0073]
5. Effects of the above reference examples and examples
As described above, the projection display apparatuses according to the reference examples and the examples include the uniform illumination optical element in the illumination optical system, the dichroic prism in the color synthesis system, and the most in the color separation system. A light guide system is arranged in the optical path of the color light beam having a long optical path length, and the divergent light beam of each color separated through the color separation system is irradiated to the light valve as a parallel light beam through the condenser lens. The configuration is adopted. Therefore, the uniform illumination optical element suppresses the color unevenness and illuminance unevenness of the light from the light source, and the color composition system is a prism composition system that generates less color unevenness and illuminance unevenness than the mirror composition system. There is little occurrence of uneven color. In addition, the light beam with a long optical path length is transmitted through the light guide system with almost no light loss, and the collimating lens irradiates the light flux with a parallel light beam. Is improved. Therefore, according to the above reference examples and examples, it is possible to realize a projection display device with less color unevenness and illuminance unevenness and higher illumination efficiency than in the past.
[0074]
Further, in the above reference examples and embodiments, the focal length of a lens that 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, color unevenness and light amount loss in the light guide system can be suppressed, so that a projection image with little color unevenness and high illumination efficiency can be formed.
[0075]
Further, in the above reference examples and embodiments, a dichroic prism that is a rotationally symmetric element with respect to the central axis of the projection optical system is used as a color composition system, and a liquid crystal with a small pixel pitch of about 50 μm or less as a light valve. The panel is used. Therefore, according to the reference example and the embodiment, it is possible to form a projection image with a good resolution, and it is possible to reduce the size of the entire apparatus using a liquid crystal panel such as a polysilicon TFT that can be easily reduced in size.
[0076]
In the above reference example and example, the number of divisions of the lens plate constituting the uniform illumination optical element is set in the range of 3 to 7, so that a projection image with suppressed color unevenness can be formed. Can do.
[0077]
Furthermore, in the above reference examples and examples, since the illumination optical system has a configuration including a polarization conversion element, the divergence loss of the light flux emitted from the light source lamp can be suppressed, and a bright projected image can be formed. it can.
[0078]
On the other hand, in the projection display device of the present invention, the optical path is configured so that the projection light can be emitted in the opposite direction and parallel to the traveling direction of the emission light from the illumination optical system, and the projection light is emitted. A configuration is adopted in which cooling means for the light source lamp is arranged on the device case side. According to this configuration, when the projector is 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 the exhaust from there is blown to the side opposite to the side of the observer. It will be. Therefore, there is an advantage that the noise of the cooling means and the exhaust from the cooling means do not disturb the observer.
[0079]
On the other hand, according to the reference example and the embodiment, in addition to the effects described above, the back focus of the projection lens of the optical system is short, so that it is easy to project a large screen over a short distance. Therefore, it is possible to realize a projection display device suitable for presentation use and home home theater use. In addition, since the back focus of the projection lens is short, a bright projection lens having a small F number and a small number of lenses can be realized, and the cost of the apparatus can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a configuration of an optical system of a projection display device according to a reference example of the present invention.
FIG. 2 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. 3A and 3B are schematic perspective views showing the configurations of first and second lens plates constituting the uniform illumination optical element of FIG. 1, respectively.
4 is a schematic perspective view showing a configuration of first and second lens plates constituting the uniform illumination optical element of FIG. 1. FIG.
FIG. 5 is a graph showing the relationship between the number of divisions of the lens plate of the uniform illumination optical element and the color unevenness.
6A and 6B are explanatory diagrams for explaining the function of the uniform illumination optical element. FIG.
FIG. 7 is a schematic configuration diagram showing a modification of the light guide system in the reference example of the present invention.
FIGS. 8A and 8B are a schematic configuration diagram showing another modification of the light guide system in the reference example of the present invention, and an explanatory diagram showing its function. FIGS.
FIGS. 9A and 9B are a schematic configuration diagram showing still another modified example of the light guide system in the reference example of the present invention, and an explanatory diagram showing its function. FIGS.
FIG. 10 is a schematic configuration diagram showing a modification of the light guide system shown in FIG.
FIGS. 11A and 11B are a schematic configuration diagram illustrating an optical system of a projection display apparatus according to an embodiment of the present invention, and an explanatory diagram illustrating a light guide system thereof. FIGS.
FIGS. 12A and 12B are explanatory views showing a modification of FIG. 11B.
FIG. 13 is a schematic configuration diagram showing an optical system and a cooling fan of a projection display apparatus according to a third embodiment of the present invention.
14 is an explanatory diagram showing a configuration of a polarization conversion element incorporated in the illumination optical system of FIG.
15 is a schematic configuration diagram showing a modification of the uniform illumination optical element in FIG. 1. FIG.
FIG. 16 is a schematic configuration diagram showing a projection display apparatus according to a second embodiment of the present invention.
FIG. 17 is a schematic configuration diagram showing a modification of the projection display apparatus according to the second embodiment of the present invention.
FIG. 18A is an explanatory diagram showing the light guide system of FIG. (B) is explanatory drawing which shows the modification of the light guide system shown to FIG. 18 (A).

Claims (9)

A light source, color separation means for separating the light flux emitted therefrom into three color light fluxes, three modulation means for modulating the separated light fluxes of each color, and the three color separation means separated by the color separation means. A light guide unit disposed on an optical path between the color separation unit and the modulation unit of a light beam having a longer optical path length than other color light among the light beams of the respective colors incident on the modulation unit, and the modulation unit. In a projection display apparatus having color combining means for combining modulated light beams of respective colors modulated in the above manner and a projection lens for projecting the combined modulated light beams on a screen,
Uniform illumination optical means that is inserted in an optical path between the light source and the color separation means, converts a light beam from the light source into a uniform rectangular light beam, and emits the light toward the color separation means;
Three condensing lenses that are respectively arranged in light beam emitting portions for emitting light beams of the respective colors in the color separation means and convert the divergent light beams from the uniform illumination optical means into substantially parallel light beams,
Among the three condensing lenses, the condensing lens arranged in the light beam emitting portion of the light beam having a longer optical path length than the other color light of the color separating means directs the substantially parallel light beam to the light guiding means. Exit
The color composition means is a dichroic prism,
The light guide means is disposed between the triangular prisms, the incident side triangular prism that is disposed on the incident side and bends the optical path by 90 degrees, the output triangular prism that is disposed on the output side and bends the optical path by 90 degrees, and A light guide member,
A projection display device characterized by that. 2. The projection display device according to claim 1, wherein the shape of the entrance surface of the entrance-side triangular prism and the exit surface of the exit-side triangular prism are substantially the same as the shape of the display section of the modulation means. 3. The projection display device according to claim 1, wherein the light guide member is a quadrangular prism. 4. The incident side triangular prism, the quadrangular prism, and the output side triangular prism are between the exit surface of the incident side triangular prism and the entrance surface of the square prism, and of the quadrangular prism. A projection display device , wherein a gap is provided between an exit surface and an entrance surface of the exit side triangular prism. 5. The projection display device according to claim 4, wherein an anti-reflection coating is applied to an interface between the triangular prism and the quadrangular prism. 6. The projection display device according to claim 1, wherein a coating of a metal film is applied to a total reflection surface of the triangular prism. 6. The projection display device according to claim 1, wherein the total reflection surface of the triangular prism is coated with a dielectric multilayer film. 8. The uniform illumination optical unit according to claim 1, wherein the uniform illumination optical means includes at least one lens plate having a plurality of lenses arranged in a plane perpendicular to a main axis of output light of the light source. Projection type display device characterized by having a configuration. 9. The uniform illumination optical unit according to claim 1, further comprising a polarization conversion unit, wherein the polarization conversion unit converts random polarization from the light source into two waves, a P wave and an S wave. A projection display device comprising: a polarization separation element that separates linearly polarized light; and a polarization plane rotation element that matches the polarization planes of the two separated polarizations.

Images