JP3506142B1 - Projection display device - Google Patents

Abstract

An object of the present invention is to realize a device with less color unevenness and illuminance unevenness and high illumination efficiency. SOLUTION: The projection display device 1 has an illumination optical system 2A.
And a color separation system 4 and three liquid crystal panels 5R, 5G and 5B.
, A light guide system 9 disposed on the optical path of the light beam G having the longest optical path length, a dichroic prism 6, and a projection lens 7 for projecting the light beam on a screen 8. The illumination optical system 2A includes a uniform illumination optical element 3 that converts a light beam into a uniform rectangular light beam. Since the illumination optical system incorporates a uniform illumination optical element for suppressing color unevenness and illuminance unevenness, it is possible to realize a device with less color unevenness and illuminance unevenness and high illumination efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention separates a light flux from a light source into three color light fluxes of red, blue and green, modulates each of these color light fluxes in accordance with image information through a modulator, and after modulating the information. The present invention relates to a projection display device that re-synthesizes the modulated light beams of the respective colors and enlarges and projects them on a screen via a projection lens.

[0002]

2. Description of the Related Art A projection display device includes a light source lamp, color separation means for separating a light beam from the light source into three color light beams, three light valves for modulating the separated three color light beams, and a modulation device. It is composed of a color synthesizing means for re-synthesizing the colored light fluxes after being formed, and a projection lens for enlarging and displaying the optical image obtained by the synthesis. A liquid crystal panel is generally used as the light valve.

As a conventional projection type display device of this structure, there is known a light source part in which a uniform illumination optical element called an optical integrator is incorporated. For example, U.S. Pat. No. 5,098,184 discloses a projection type display device in which this optical integrator is incorporated. In addition, this publication describes a structure in which dichroic mirrors are arranged in an X shape as a color synthesizing means. Usually, it is composed of a dichroic mirror in which a dielectric multilayer film is formed on a glass plate.

The projection type display device having the mirror combining system in which the color combining means is composed of the dichroic mirror as described above has the following problems. That is, the dichroic mirror becomes an optical element that is non-rotationally symmetric 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) showing the transfer characteristics of the projection optical system.
r Function) characteristics are deteriorated. As a result, the image quality is blurred and the sharpness is lowered. The deterioration of the MTF characteristics is not so serious 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, if the pixel pitch becomes small, such as in the case of a liquid crystal panel using a polysilicon TFT as a switching element, it cannot be ignored.

As a conventional projection type display device, there is known a type having a prism combining system in which the color combining means is constituted by a dichroic prism. The dichroic prism is an optical element that is rotationally symmetrical with respect to the central axis of the projection lens. Therefore, the aberration generated by this prism can be easily removed by the design of the projection lens, and in general, the MTF characteristic of the projection type display device having the prism combining system has the above-mentioned mirror combining system. It is superior to the ones that 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. In this device, a light transmitting means including a relay lens, a field lens, etc. is interposed in the optical path of the color light having the longest optical path length so as to suppress the decrease of the light quantity and the color unevenness.

However, in this apparatus, although the light quantity of the color light having the longest optical path length is not reduced, the brightness distribution of the luminous flux is rotated by 180 degrees by the relay lens, so that the original brightness distribution is not axisymmetric. However, 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 the displacement of the mounting position of the light source lamp and the slight asymmetry of the light source lamp and its reflecting mirror. , The brightness distribution is usually non-axisymmetric.

Here, in the projection type display device, it is required to increase the illuminance of the projected image and eliminate the color unevenness and the illuminance unevenness to obtain an image quality close to that of an image viewed directly on a CRT. To do this, the color synthesis system
It is preferable to use a prism combining system having good transfer characteristics. It is also preferable to use an optical integrator in the light source portion to illuminate the liquid crystal panel with uniform brightness and efficiently. 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 light quantity reduction of the color light assigned to the longest optical path and the change of the illuminance distribution become remarkable, which causes Color irregularities and changes in color temperature appear in the image. Therefore, the effect of the integrator cannot be fully exerted. Furthermore, when an optical integrator is used for the light source portion, the conventional technique cannot be used as it is. That is, in the illumination using the optical integrator, the divergent light flux from the surface light source existing at a finite position (light flux emission surface of the integrator) from the liquid crystal panel illuminates the liquid crystal panel, and thus the infinite distance as in the conventional configuration is used. 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 type display device capable of forming a projection image of a higher quality without unevenness in illuminance, color unevenness, etc., as compared with the conventional projection type display device described above. .

It is another object of the present invention 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 type display device capable of forming a projected image with higher illuminance than the conventional one.

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

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

[0014]

In order to achieve the above-mentioned object, a projection type display device of the present invention comprises a light source, a color separation means for separating a light beam emitted from the light source into three color light beams, and a separation device. Of the three light modulating means for modulating the light flux of each color and the light flux of each color separated by the color separation means and incident on each of the three light modulating means, a light flux having a longer optical path length than the other color light Projection type having a light guide means arranged on the optical path, a color combining means for combining the modulated light fluxes of the respective colors modulated through the modulation means, and a projection lens for projecting the combined modulated light flux on a screen In the display device, a first lens plate having a plurality of first lenses, a second lens plate having a plurality of second lenses provided corresponding to the plurality of first lenses, the first lens plate and the On the optical path between the second lens plate And a reflecting mirror for bending an optical path, wherein an image of the light source is formed on the plurality of second lenses, and an image of the plurality of first lenses is formed by the plurality of corresponding second lenses. Uniform illuminating optical means for superimposing an image on the modulating means and a luminous flux emitting portion for emitting luminous flux of each color in the color separating means are respectively arranged to convert a divergent luminous flux from the uniform illuminating optical means into a substantially parallel luminous flux. And three light-collecting lenses, the color synthesizing means is a dichroic prism, and the light guiding means includes an incident side reflecting mirror, an emitting side reflecting mirror, and at least one.
A plurality of lenses, and an optical path is formed so that the direction of the projection light from the projection lens is parallel and opposite to the traveling direction of the emitted light of the light source. The cooling means for the light source is arranged in the device case on the side of the emission direction of the, and the exhaust port of the cooling means is formed on the side surface of the case on the side of the emission direction of the projection light.

According to this configuration, since the cooling unit is located on the side opposite to the viewer of the projected image, there is an advantage that the noise and exhaust gas generated here do not interfere with the viewer. Further, the uniform illuminating optical means is used to illuminate the modulating means, and a condenser lens is arranged in the optical path of each color light to make a divergent light flux into a parallel light flux, and one color light is passed through the light guiding means. Therefore, according to the present invention, it is possible to form a projection image that is brighter and higher in quality than conventional ones, with a uniform illuminance distribution and no color unevenness.

[0016]

[0017]

[0018]

[0019]

[0020]

The number of the first lens and the second lens in one direction of the first and second lens plates is preferably between about 3 and 7.

It is preferable that the color light passing through the light guide means is generally green light, which has 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, which is relatively unnoticeable to the image quality due to the change in the light amount.

[0023]

Furthermore, it is preferable to dispose polarization conversion means in the uniform illumination optical means. This polarization conversion means is composed of a polarization separation element for separating the random polarization from the light source lamp into two linear polarizations of P wave and S wave, and a polarization plane rotation element for matching the polarization planes of the two separated polarizations. It By using this polarization conversion means, the utilization efficiency of the light emitted from the light source lamp can be improved, and accordingly, the illuminance of the projected image can be increased.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

1. Reference Example FIG. 1 shows an optical system of a projection display apparatus according to a reference example of the present invention. The projection display device 1 of this example includes a light source 2
And an illumination optical system 2A composed of a uniform illumination optical element 3
And the luminous flux W emitted from the illumination optical system 2A through the uniform illumination optical element 3 is divided into red, green and blue luminous fluxes R, G,
A color separation optical system 4 for separating into B, and three liquid crystal panels 5R, 5G, 5B as light valves for modulating each color light flux.
And a color combining optical system 6 for re-combining the modulated color light fluxes,
It has a projection lens 7 for enlarging and projecting the combined light flux on a screen 8. Further, it has a light guide system 9 for guiding the green light flux G among the respective color light fluxes separated by the color separation optical system 4 to the corresponding liquid crystal valve 5G.

The light source 2 of this example comprises 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. The uniform illumination optical system 3, which will be described in detail later, is composed of 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 comprises a blue-green reflection dichroic mirror 401, a blue reflection dichroic mirror 402 and a reflection mirror 403. The light flux W is first reflected by the blue-green reflection dichroic mirror 401 at right angles to the blue light flux B and the green light flux G contained therein, and travels toward the blue reflection dichroic mirror 402 side.
The red light flux R passes through this mirror 401, is reflected at a right angle by a rear reflecting mirror 403, and emits a red light flux 404.
Is emitted from the color synthesizing optical system side. The blue and green luminous fluxes B and G reflected by the mirror 401 are reflected at a right angle by the blue reflection dichroic mirror 402, and are emitted from the emitting portion 405 of the blue luminous flux to the color combining optical system side. It The green luminous flux G that has passed through this mirror 402 is emitted from the emitting portion 406 of the green luminous flux toward the light guide system 9 side. In this example, the distances from the light emitting portions of the uniform illumination optical element 3 to the light emitting portions 404, 405, 406 of the respective color light beams in the color separation optical system 4 are set to be equal.

Here, in this example, the color separation optical system 4
On the exit sides of the exit sections 404, 405, and 406 for the respective colored light fluxes, the condensing lens 101 formed of a plano-convex lens,
102 and 103 are arranged. Therefore, the light fluxes of the respective colors emitted from the respective emission portions are collected by the condenser lenses 1
It is incident on 01 to 103 and collimated.

The red and blue light fluxes R, B of the respective color light fluxes R, G, B after being collimated are collected by the condenser lens 10.
The liquid crystal panels 5R, 5 arranged immediately after 1, 102
It is incident on B and is modulated, and image information corresponding to each color light is added. That is, these liquid crystal panels are subjected to switching control in accordance with image information by a driving unit (not shown), whereby the respective color lights passing therethrough are modulated. As such driving means, known means can be used as they are, and the description thereof will be omitted in this example. On the other hand, the green light flux G is guided to the corresponding liquid crystal panel 5G via the light guide system 9, and here, similarly, it is modulated in accordance with the image information. The liquid crystal panel of this example uses a polysilicon TFT as a switching element and has a pixel pitch of 50 μm or less.

The light guide system 9 in this example is an incident side reflection mirror 9.
1 and the exit side reflecting mirror 92, and an intermediate lens 93 arranged between them. 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, regarding the optical 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, as in this example, the light amount loss can be suppressed by interposing the light guide system 9. The color light flux that passes through the light guide system 9 may be a red or blue light flux. However, in general, 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 allocate the green light flux to the optical path passing through the light guide system 9. However, if priority is given to brightness and uniformity of image quality over color balance, a blue light flux having low luminosity and relatively inconspicuous illuminance unevenness may be assigned to the light guide system 9.

Next, the respective color luminous fluxes which have been modulated through the respective liquid crystal panels 5R, 5G and 5B are incident on the color synthesizing optical system 6 and are re-synthesized there. In this example, the color combining optical system 6 is configured by using a dichroic prism. As the color combining optical system 6, it is also possible to use a mirror combining system having a configuration in which dichroic mirrors are arranged in an X shape.
However, in a projection display device having a mirror combining system in which the color combining optical system is composed of dichroic mirrors, the dichroic mirror is an optical element that is non-rotationally symmetric with respect to the central axis of the projection lens. Therefore, astigmatism occurs in the image on the screen, and the MTF of the projection optical system is increased.
(Modulation Transfer Func
function) is deteriorated. As a result, the image quality is blurred and the sharpness is lowered. The deterioration of the MTF characteristic is caused when the size of the liquid crystal panel is larger than the number of pixels, that is,
When the pixel pitch is large, it does not matter so much.
However, if the pixel pitch becomes 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 the dichroic prism is used as the color synthesizing optical system 6, it is possible to avoid such an adverse effect.

This point will be described with reference to FIG. This figure shows the MTF characteristics of the projection display device including the prism combining system of this example and the projection display device when the color combining system is the mirror combining 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 the MTF (%). The solid line is the characteristic of the projection optical system including the prism combining system. The thick solid line is the characteristic of the central part of the screen, and the thin solid line is the characteristic of the peripheral part of the screen. Similarly, the broken line is the characteristic of the projection optical system including the mirror combining system. The thick broken line is the characteristic of the central part of the screen, and the thin broken line is the characteristic of its peripheral part.

The MTF characteristic of the projection lens alone is deteriorated by the astigmatism occurring in the mirror combining system because the mirror is inserted at an angle of 45 degrees. As in the present example, in a liquid crystal panel using a polysilicon TFT as a switching element and having a pixel pitch of 50 μm or less, the spatial frequency is 20.
At (1 ine / mm), MTF characteristics of 30% or more are required. However, it is understood that when the mirror combining system is used, sufficient MTF characteristics cannot be obtained in the peripheral portion of the screen. On the other hand, when the prism combining 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 can be seen that the MTF characteristic is not deteriorated.

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

(Illumination Optical System) As an element suitable for 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. Figure 3 shows the basic configuration when used in a projection display device.
It is shown in (A). 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, and similarly, the second lens plate 32 also has 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 of these rectangular lenses 301 is changed by the corresponding rectangular lens of each rectangular lens 302 forming the second lens plate 32.
An image is superimposed and formed on the liquid crystal panel. Therefore, the liquid crystal panel is illuminated with a 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 necessarily have to be separated. The lens plates 31 and 32 can be brought closer to each other by reducing the size of each rectangular lens and increasing the number of divisions of the incident light beam. Furthermore, it is also possible to integrate it into one lens plate.

Here, the relationship between the number of divisions by the rectangular lenses of the lens plates 31 and 32 forming the uniform illumination optical element 3 and the color unevenness will be described with reference to FIG. In the graph of FIG. 5, the horizontal axis represents the number of divisions of the first and second lens plates (integrator lenses), and the vertical axis represents the color unevenness, with the central portion (one place) and the peripheral portion (4) on the screen 8. Location)
The difference in color between the two is displayed 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 that is judged to be acceptable as color unevenness.

As can be seen from this graph, the number of divisions is 3
The above is preferable. However, from the viewpoint of manufacturing, increasing the number of divisions leads to higher cost. Therefore, the practical number of divisions is in the range of 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 form the uniform illumination optical element 3. Also in the example shown in this figure, each lens plate is composed of rectangular lenses of the same size. However, in the arrangement state of the rectangular lenses, the number of divisions in the vertical direction is 7, in the horizontal direction, the upper and lower rows are 3 divisions, the central 3 rows are 5 divisions, and the rows between them are 4 divisions. It is divided.

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

Next, referring to FIG. 6 (A), liquid crystal panels 5R, 5G, and
The operation of illuminating 5B will be described. As the light source lamp 21 that constitutes the light source 2, a light source close to a point such as a halogen lamp, a metal halide lamp, or a xenon lamp is used as described above. Further, the luminous flux emitted from the lamp is reflected by the reflecting mirror 22. An elliptical surface can be used as the shape of the reflecting surface of the reflecting mirror 22, and in this case, the first focal point is aligned with the light emitting portion of the light source lamp 21, and the second focal point is the liquid crystal panel 5 (5R, 5G, 5B). Match the center position of. As a result, the reflected light flux of the reflecting mirror 22 is reflected by the liquid crystal panel 5.
Head towards the center of. In this case, the first lens plate 31
The rectangular lenses 30 of the second lens plate 32 are arranged on a line from the center of each rectangular lens 301 to the center of the liquid crystal panel 5.
The size of the second lens plate 32, that is, the size of each rectangular lens 302 forming this lens plate is set smaller than that of the first lens plate side so that the center of 2 is located.

Each rectangular lens 301 of the first lens plate 31
Is each rectangular lens 302 of the corresponding second lens plate 32.
Concentrate the light flux at the center of. Each rectangular lens 302 of the second lens plate 32 superimposes the image of the corresponding lens of the rectangular lens 301 on the side of the first lens plate on the display area 5A (hatched area in the figure) of the liquid crystal panel 5. Make them image.
At the center of each rectangular lens 302 of the second lens plate 32,
Since the image of the light emitting portion of the light source lamp 21 is formed in this manner, the entire second lens plate 32 functions as a secondary light source. Therefore, for example, the chief ray 303 of the light flux incident on the end of the display area 5A of the liquid crystal panel 5 is transmitted by the second lens plate 32.
It coincides with the line segment connecting the center of and the end of the display area 5A. That is, the illumination light flux to the liquid crystal panel 5 is transmitted to the second lens plate 3
Since the divergent light is from 2, the divergent light needs to be parallelized in order to make the parallel light incident on the liquid crystal panel 5. For this purpose, in this example, the condenser lenses 101,
102 and 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 having a convex surface facing the liquid crystal panel 5 is used as the condenser lens. You may arrange | position in the state which turned the convex surface toward the 2nd lens plate side. A biconvex lens or a Fresnel lens can be used instead of the plano-convex lens. By disposing the condenser lenses 101, 102, and 103 in this way, the principal ray of the light flux 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 parabolic surface is used as the reflecting surface of the reflecting mirror 22 of the light source 2. In this case, the focal point of the paraboloid is made to coincide with the light emitting portion of the light source lamp 21, so that 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 the same as the first lens plate 3 having the same size.
The focal lengths of the rectangular lenses that are composed of 1 ′ and the second lens plate 32 ′ and that compose each lens plate are also the same. Second
Each rectangular lens 302 ′ of the lens plate 32 ′ of No. 3 forms an image of the rectangular lens of the corresponding first lens plate 31 ′ at infinity. Therefore, in this case, the lens 306 is added to form an image on the display area 5A of the liquid crystal panel 5, which is supposed to be infinity. 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 may 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. In addition, it is possible to interpose the reflecting mirror 33. In this case, there is an advantage that the volume occupied by the uniform illumination optical element is about 1/2 of that in the case of the previous example.
Further, as shown in this figure, the arrangement of all optical systems can be made close to a square, which contributes to downsizing of the entire apparatus.

(Light Guide System) As described above, the light guide system 9 of this embodiment is composed of two reflecting mirrors 91 and 92 and an intermediate lens 93 arranged between them. Another configuration example of the light guide system applicable to this example will be described below.

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

Next, the light guide system 9B shown in FIG.
In addition to the structure of the light guide system 9 of this example, an entrance lens 94 is added to the entrance part side thereof, and an exit lens 95 is added to the exit part side thereof.

The operation of the light guide system 9B having this configuration will be described with reference to FIG. In the figure, a pair of reflecting mirrors 91 and 92 are omitted and shown as a linear system for ease of explanation. As shown in the figure, the intermediate lens 93 is located exactly in the center of the entire optical path of the light guide system 9B, and the total optical path length is 2
If it is a, the focal length of the intermediate lens 93 is set to be substantially equal to a / 2. Therefore, the intermediate lens 9
3 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. That is, the illuminance distribution on the incident side is transmitted after being rotated 180 degrees on the emitting side. However, in this example, since the illumination optical system including the uniform illumination optical element 3 is used, the illuminance distribution is 180
It is almost symmetrical with respect to the rotation of degree. Therefore, even if the illuminance distribution is rotated or reversed in this way, display color unevenness does not occur.

On the other hand, the focal length of the entrance lens 94 is equal to the distance a to the intermediate lens 93, and the condenser lens 10
The principal ray 9a of the light flux G which has passed through 3 and becomes parallel is directed to the center of the intermediate lens 93. Therefore, an image of the second lens plate 32 on the exit side of the uniform illumination optical element 3 is formed at the center of the intermediate lens 93. Further, the focal length of the emitting 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. The incident lens 94 is a plano-convex lens as shown in the figure, and is arranged with its convex surface side facing the incident side.
This reduces the spherical aberration of the lens. The exit lens 95 is also a plano-convex lens, and is arranged such that its convex surface side faces the exit side.

The focal lengths of the entrance lens and the exit lens may be set within the 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 1/4 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. You can set it to.

FIG. 9A shows a modification of the above-mentioned 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 arranged in front of the optical path direction. The focal length of the lens 97 is set to a value obtained by adding the refracting powers of the entrance lens 94 and the condenser lens 103. That is, as shown in FIG. 9B, it is set to ab / (a + b). The lens 97 is preferably a biconvex lens in order to reduce spherical aberration. Note that, in FIG. 9B, the intermediate lens 93 is shown in a state of 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, spherical aberration can be made extremely small as compared with the case where one biconvex lens is used. 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 used as an aspherical lens 98. By using the aspherical lens 98 in this way, compared to the case where a biconvex lens is used,
Further, spherical aberration can be reduced. Therefore, it is possible to transmit the illuminance distribution on the incident side of the light guide system to the emitting side very accurately.

(Effects of Reference Example) As described above, in the projection display apparatus 1 of this example, the one including the uniform illumination optical element 3 is used as the illumination optical system, and the color combining optical system is used. A dichroic prism that is an axially symmetric optical element is used. Therefore, it is possible to realize a projection display device that has less color unevenness and uneven illuminance and high illumination efficiency. Further, since the color synthesizing system including the dichroic prism is used, the focal length of the projection lens can be shortened and a large screen display can be performed in 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.

Further, 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 color unevenness of the color light flux passing therethrough is generated. , Light loss can be reduced, which also
It is possible to suppress the occurrence of color unevenness, illuminance unevenness, and the like in the projected image, and it is possible to form a bright image.

Further, an entrance lens in the light guide system,
When the configuration in which the condenser lens is integrated is adopted, the number of constituent elements can be reduced, and accordingly, 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 spherical aberration can be reduced.

On the other hand, in the present example, the number of divisions in the uniform illumination optical element is set in the range of 3 to 7 and the pixel pitch of the liquid crystal panel is set to 50 μm or less, so that unevenness in color of the projected image It is possible to suppress the occurrence of blurring and the like, and thus it is possible to realize a projection display device capable of forming a projected image with high image quality.

2. First Embodiment FIG. 11 shows a projection display device according to the first embodiment of the present invention. The projection display apparatus 100 of this example is the same as the projection display apparatus 1 of the reference example described above except for the configuration of its light guide system. Therefore, corresponding parts are designated by the same reference numerals, and the description thereof will be omitted.

The light guide system 9E in the projection display apparatus 100 of this example is composed of an incident side triangular prism 901, an outgoing side triangular prism 902, and a quadrangular prism 903 arranged between them.

Referring to FIG. 11B, the light guide system 9E of this example.
Explain the function of. The light beam collimated by the condenser lens 103 is vertically incident on the incident surface 904 of the triangular prism 901, is reflected by the total reflection surface 905, and is emitted from the exit surface 906.
Exit from. The total reflection surface 905 may simply be an optical flat surface made of glass material or plastic. However, when the incident light flux contains a light ray having an angle such that the light flux is not totally reflected, it is preferable to coat a metal film of aluminum, silver, or the like. Alternatively, a dielectric multilayer reflective film may be coated. Incident surface 904 and exit surface 906
As shown in the figure, since has a function of guiding light by total reflection, it needs to be an interface between air and a glass material and cannot be bonded to an adjacent optical element. Therefore, in the triangular prism 901, it is necessary that all five surfaces are optically flat surfaces, and in some cases, the entrance surface 904 and the exit surface 906 need to be subjected to antireflection coating.
In particular, it is preferable to apply an antireflection coating to the interface with the adjacent rectangular prism 903.

In the quadratic prism 903, all six surfaces are optically flat surfaces, and the four surfaces 907 parallel to the principal axis of the passing light beam guide the light beam by total reflection. The exit side triangular prism 902 is an entrance side triangular prism 901.
It has the same configuration as. The emitted light flux enters the display unit 5A of the liquid crystal panel 5G.

In order to increase the transmissivity of the luminous flux, 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 determined by the display portion 5A of the liquid crystal panel 5G.
It is almost the same as the rectangular shape. Here, the uniform illumination optical element 3 of the illumination optical system includes, as shown in FIG. 3, first and second lens plates 3 in which rectangular lenses are arranged in a matrix.
It is composed of 1 and 32. Therefore, the incident surface 904 of the triangular prism 901 on the incident side is illuminated almost uniformly according to its rectangular shape. The three prisms are transmitted to the display unit 5A of the liquid crystal panel 5G while maintaining the light quantity of the incident light flux, the parallelism, and the uniform brightness distribution. The triangular prism 902 on the emission side 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 type display device of this example having the above-described structure, it is possible to obtain the same effect as that of the above-mentioned reference example. Instead of the square prism 903 of the light guide system in this example, for example, a light guide member having a tubular shape by combining four reflecting mirrors may be used.

The rectangular prism 90 of FIG. 11B is used.
Reference numeral 3 denotes four reflecting mirrors 903 ′ as shown in FIG.
It may be a cylindrical light guide system. The reflectance of the light guide surface is slightly lower, but the function is the same. Further, as shown in FIG. 12B, the light guide system may be composed of two upper and lower reflection plates 911 and 912 and two reflection 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 shortening the focal length of the lens 103 to some extent. 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.

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

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

A light guide system 9G having this construction is shown in FIG. The integrated lens 924 is composed of a decentered biconvex lens as shown in the figure.

FIG. 18 shows a specific structure of the above light guide system 9F.
It shows in (A). When 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 a / 2.
Is almost equal to. The curved surface 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 emitting portion as a reflected image 803, and the illuminance distribution at the incident portion is actually inverted and output at the emitting 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 their centers. The field lens 921 on the incident side converts the parallel light flux from the condenser lens 103 into a concave mirror 92.
Collect in the center of 3. Field lens 922 on exit side
Refracts the light flux reflected from the concave mirror 923 so as to become a light flux perpendicular to the liquid crystal panel 5G.

The light guide system 9F can also be constructed as shown in FIG. 18 (B). Light guide system 9H shown in this figure
Then, the two field lenses 921 and 922 in the light guide system 9E described above are configured by one lens 806, and the concave mirror 923 is replaced with the plane mirror 804, and the lens 806 is replaced.
It is located at a distance of a / 2 from. In addition, the lens 80
A plane mirror 805 is arranged perpendicular to the optical axis 807 of No. 6.
The parallel light flux entering the light guide system 9H passes through the end of the lens 806, is reflected by the plane mirror 804, and is collected at the center of the plane mirror 805. The light flux reflected from the plane mirror 805 is reflected by the plane mirror 804, then passes through the end of the lens 806, and vertically enters the display unit 5A of the liquid crystal panel 5G. It is the central portion of the lens 806 that forms the image of the object 802 at the entrance portion as the inverted image 803 at the exit portion.
Since the light beam passes through the center of No. 6 twice, it is the same as having passed through the lens whose focal length is a / 2. The configuration of this example has an advantage that the size is smaller than that of the above-described light guide system 9F.

4. Third Embodiment FIG. 13 shows a projection display device according to the third embodiment of the present invention. The projection type display device 200 of this example is designed so that the optical system can be compactly housed in the case 201. The optical system in this example is the illumination optical system 2
B, 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. Of these, the color separation optical system 4, the light valves 5R, 5G, 5B, the color combination optical system 6,
The projection lens 7 is the same as in the device 100 of the reference example. The light guide system 9D is the same as that shown in FIG. Therefore, corresponding parts in these parts are designated by the same reference numerals, and the description of each part will be omitted.

In the apparatus 200 of this example, the illumination optical system 2B is arranged so that the central axis 1a of the light emitted from the illumination optical system 2B and the optical axis 7a of the projection lens 7 are parallel to each other.
In, the direction of the light emitted from the light source lamp 21 is bent at a right angle. Further, the illumination optical system 2B is
It has a configuration including a polarization conversion system 11.

In other words, the illumination optical system 2B of this example has a light source 2 composed of a lamp 21 and a reflecting mirror 22, a polarization conversion element 11 arranged on the exit side, and a uniform illumination optical element 3A arranged on the exit side. It consists of

As shown in FIG. 14, the polarization conversion element 11 of this example has a polarization beam splitter 111 and a reflecting mirror 112.
And a λ / 2 retardation film 113. The randomly 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 the 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 dependency, a light source having a lamp with a short arc length capable of emitting light with excellent parallelism is suitable. The separated P-polarized light 115 passes through the λ / 2 phase difference plate 113, which is a polarization-plane rotating element, so that the polarization plane is rotated by 90 degrees to become S-polarized light. On the other hand, the S-polarized light beam 116 is simply bent in its optical path by the prism type reflection mirror 112, and is emitted as it is as S-polarized light. In this example, the reflecting mirror 112 is formed as, for example, a vapor-deposited film of aluminum, and has a higher reflectance for S-polarized light than P-polarized light. Therefore, the optical path for S-polarized light is bent by the reflecting mirror 112. As the reflecting mirror 112, in addition to the prism type, a general plane type reflecting mirror may be used. The random polarized light 114 from the light source is emitted as S-polarized light by passing through the polarization conversion element 11 having this configuration. In this example, P-polarized light is converted into S-polarized light, but conversely, S-polarized light may be converted into 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 emits the S-polarized light 1
A first lens plate 31 arranged on a plane perpendicular to the main axis of 16, a second lens plate 32 arranged in a state orthogonal to the first lens plate 31, and arranged between these lens plates 31, 32, It is composed of a reflecting mirror 33 for bending 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 reference example. In this way, the light flux that has entered the uniform illumination element 3A is bent at a right angle and exits from here. The emitted white S-polarized light flux is separated into primary-color light fluxes by the color separation optical system 4. The separated light fluxes of the respective colors are combined in the color combining optical system 6 including a dichroic prism, and enlarged and projected on the screen 8 via the projection lens 7.

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

Therefore, in the apparatus 200 of this example, the air used for cooling and warmed during the use is discharged in the same direction as the projection light. For this reason, when this projection display device is a front projection type and an image is displayed on a reflective screen for observation, the observer is usually behind the device. Therefore, there is an advantage that the viewer's viewing is not disturbed by the noise of the cooling fan or the warm air blown from it. Further, even when the apparatus is installed in a place where the installation space is relatively small, such as an audio rack, since the exhaust air is from the front, the problem of exhaust air being trapped in the surroundings does not occur, which is convenient.

In addition, in the apparatus 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 converted light beams are effectively combined and emitted with almost no divergence loss. Therefore, it is possible to realize a bright illumination optical system that emits only polarized light with high efficiency. Furthermore, in this example, since the emitted polarized light flux is passed through the uniform illumination optical element 3A, color unevenness and illuminance unevenness occurring in the light source are suppressed, and illumination light with high uniformity can be obtained. it can.

5. Effects of Reference Examples and Examples As described above, the projection display devices according to the reference examples and examples include the uniform illumination optical element in the illumination optical system, and the dichroic prism in the color combining system. Further, a light guide system is arranged in the optical path of the color light flux having the longest optical path length in the color separation system, and the divergent light flux of each color separated through the color separation system is collimated through a condenser lens. As a result, the light valve is used for irradiation. Therefore, the uniform illumination optical element suppresses the color unevenness and illuminance unevenness of the light from the light source, and the color combining system is a prism combining system in which the occurrence of color unevenness and illuminance unevenness is less than that of the mirror combining system. There is little occurrence of color unevenness. In addition, since the light of the color light flux having a long optical path length is transmitted through the light guide system in a state where there is almost no light quantity loss, and the parallel light flux is applied to the light valve by the condenser lens.
The light loss is small and the illumination efficiency is improved. Therefore, according to the above-mentioned reference examples and examples, it is possible to realize a projection display device having less color unevenness and illuminance unevenness and higher illumination efficiency than in the past.

In the above-mentioned reference examples and examples, the focal length of the lens, which is a constituent element 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, it is possible to suppress color unevenness and light amount loss in the light guide system, and thus it is possible to form a projected image with little color unevenness and high illumination efficiency.

Further, in the above-mentioned reference examples and examples, a dichroic prism, which is an element rotationally symmetric with respect to the central axis of the projection optical system, is used as a color combining system, and the light valve has a small pixel pitch of about 50 μm or less. I am using a pitch LCD panel. Therefore, according to the above-described reference examples and examples, it is possible to form a projection image with a high resolution and to downsize the entire device by using a liquid crystal panel such as a polysilicon TFT which can be easily downsized.

Further, in the above-mentioned reference examples and examples, since the number of divisions of the lens plate constituting the uniform illumination optical element is set within the range of 3 to 7, it is possible to obtain a projected image in which color unevenness is suppressed. Can be formed.

Furthermore, in the above-mentioned reference examples and examples,
Since the illumination optical system is provided with the polarization conversion element, the divergence loss of the luminous flux emitted from the light source lamp can be suppressed and a bright projected image can be formed.

On the other hand, in the projection display device of the present invention, the direction of travel of the light emitted from the illumination optical system is
The optical path is configured so that the projection light can be emitted in the opposite direction and in the parallel direction, and the configuration is such that cooling means for the light source lamp is arranged on the side of the device case from which the projection light is emitted. 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 gas from the cooling means blows to the side opposite to the side of the observer. Be issued. Therefore, there is an advantage that the noise of the cooling means and the exhaust gas from the cooling means do not disturb the observer.

On the other hand, according to the above-mentioned reference examples and examples,
In addition to the above-mentioned effects, the back focus of the projection lens of the optical system is short, which facilitates short-distance large-screen projection. Therefore, it is possible to realize a projection display device suitable for presentations and home home theaters. Moreover, since the back focus of the projection lens is short, a bright F-number and a bright projection lens can be realized with a small number of lenses, and the cost of the apparatus can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of an optical system of a projection display apparatus according to a first reference example of the present invention.

FIG. 2 is a pixel density and a transfer characteristic (MTF) of a liquid crystal panel used as a light valve in a projection display device.
It is a graph which shows the relationship with.

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.

FIG. 4 is a first part of the uniform illumination optical element of FIG.
FIG. 3 is a schematic perspective view showing the configuration of a second lens plate.

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 views for explaining the function of the uniform illumination optical element.

FIG. 7 is a schematic configuration diagram showing a modification of the light guide system in the first reference example of the present invention.

8A and 8B are a schematic configuration diagram showing another modification of the light guide system in the first reference example of the present invention, and an explanatory diagram showing its operation.

9A and 9B are a schematic configuration diagram showing still another modified example of the light guide system in the first reference example of the present invention, and an explanatory diagram showing the operation thereof.

FIG. 10 is a schematic configuration diagram showing a modified example of the light guide system shown in FIG. 9 (A).

11A and 11B are schematic configuration diagrams showing an optical system of a projection display apparatus according to a second reference example of the present invention;
It is explanatory drawing which shows its light guide system.

12 (A) and (B) are explanatory views showing a modified example of FIG. 11 (B).

FIG. 13 is a schematic configuration diagram showing an optical system and a cooling fan of the projection type display device according to the example of the invention.

14 is an explanatory diagram showing a configuration of a polarization conversion element incorporated in the illumination optical system of FIG.

FIG. 15 is a schematic configuration diagram showing a modified example of the uniform illumination optical element in FIG.

FIG. 16 is a schematic configuration diagram showing a projection display device according to a third reference example of the present invention.

FIG. 17 is a schematic configuration diagram showing a modified example of the projection display apparatus according to the third reference example of the present invention.

18A is an explanatory diagram showing the light guide system of FIG. 16. FIG. 18B is an explanatory diagram showing a modified example of the light guide system shown in FIG.

Continuation of the front page (56) Reference JP-A-2-113412 (JP, A) JP-A-5-34825 (JP, A) JP-A-4-318534 (JP, A) JP-A-3-210550 (JP , A) Japanese Patent Laid-Open No. 3-111806 (JP, A) Japanese Patent Laid-Open No. 2-163729 (JP, A) Actual Kai 1-94985 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) G03B 21/00 G02B 19/00 G02B 27/18

Claims (3)

(57) [Claims] 1. A light source, a color separation means for separating a light beam emitted from the light source into light beams of three colors, three modulating means for modulating the separated light beams of respective colors, and the color separation means. Of the light flux of each color incident on each of the three modulating means, the light guide means disposed on the optical path of the light flux having a longer optical path length than the other color light, and each of the colors modulated through the modulating means. In a projection display device having a color synthesizing means for synthesizing the modulated light flux and a projection lens for projecting the synthesized modulated light flux on a screen, a first lens plate having a plurality of first lenses, and a plurality of the first lenses. A second lens plate having a plurality of second lenses provided corresponding to the lenses; and a reflecting mirror arranged on the optical path between the first lens plate and the second lens plate for bending the optical path. And a plurality of second lenses An image of the light source is formed on the uniform illumination optical means for superimposing an image of the plurality of first lenses on the modulating means by the corresponding plurality of second lenses, and the color separating means. The color synthesizing means is a dichroic prism, and each of the color synthesizing means is a dichroic prism which is disposed in a light flux emitting portion for emitting a light flux of each color and which converts a divergent light flux from the uniform illumination optical means into a substantially parallel light flux. Yes, the light guide unit includes an incident-side reflecting mirror, an emitting-side reflecting mirror, and at least one lens, and is projected from the projection lens in the traveling direction of the emitted light of the light source. An optical path is formed so that the directions of light are parallel and opposite to each other. Cooling means for the light source is arranged in the device case on the side of the emission direction of the projection light. How to emit Of being formed on the side of the case side, a projection display device, characterized in that. 2. The projection display device according to claim 1, wherein the number of the first lens and the second lens in one direction on the first and second lens plates is between about 3 and 7. . 3. The uniform illumination optical means according to claim 1 or 2, further comprising polarization conversion means, wherein the polarization conversion means converts the randomly polarized light from the light source into two waves, a P wave and an S wave. A projection display device comprising a polarization splitting element for splitting into linearly polarized light and a polarization plane rotating element for matching the polarization planes of two split polarized lights.