JP2002221757A - Image formation optical system and projector using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a compact image formation optical system having high- performance by uniformalizing lengths of optical paths of color lights, respectively, in a color light separating optical system without using a relay optical or drawing around a complicated optical path, and also to obtain a projector using the same. SOLUTION: This image formation optical system is provide with dichroic mirrors 211, 212 which separate light from a light source 110 into red, green and blue color lights, mirrors 221, 222, 223, 224 which form mutually symmetrical optical paths by reflecting two color lights among those separated with the dichroic mirror on the same horizontal surface, and mirrors 231, 232, 233, 234 which form a protruded optical path by reflecting the last color light separated with the dichroic mirror orthogonally or parallel to the horizontal surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming optical system or a projector using the same.

[0002]

2. Description of the Related Art FIG. 6 is a plan view showing a known optical system in a projector. According to this, the projector 500 makes the illuminance distribution of the light emitted from the light source 510 uniform, and the liquid crystal panel 5 has a uniform polarization direction.
An illumination optical system 520 for causing the light to enter the 50R, 550G, and 550B, and a color light separation optical system 530 that separates the light beam W emitted from the illumination optical system 520 into red, green, and blue color light beams R, G, and B. And a relay optical system 540 that guides the blue light flux B among the respective color light fluxes separated by the color light separation optical system 530 to the corresponding liquid crystal panel 550B, and three liquid crystal panels 550R that modulate each color light flux according to given image information. , 550G, 550B, a cross dichroic prism 560 as a color light combining optical system for combining the modulated color light beams, and a projection lens 570 for enlarging and projecting the combined light beam on a projection surface.

The light beam from the illumination optical system 520 is separated into red, green, and blue light beams R, G, and B by a color light separation optical system 530, and then the corresponding liquid crystal panels 550R, 550G, and 550B. Incident on. In this case, if the optical path length of each color light in the color light separation optical system 530 is different, a difference occurs in the intensity of each color light incident on each liquid crystal panel, and when the respective color lights are combined, the color balance of the image is deteriorated or the projection is performed. Because the image on the surface may be dark,
For the blue luminous flux B having an optical path longer than the optical paths of the other color lights, the use of the relay optical system 540 is particularly used to prevent a reduction in light utilization efficiency due to light diffusion or the like.

Japanese Patent Application Laid-Open No. 5-66505 discloses that red,
A projector has been disclosed in which the optical path lengths of green, blue and blue light are repeatedly reflected in the horizontal direction by using a mirror and routed to thereby equalize the optical path lengths of the red, green, and blue light.

[0005]

However, in order to equalize the optical path lengths of the separated color lights, the color light using the relay optical system has its illuminance distribution inverted and color unevenness or the like is likely to occur. In addition, when the optical path of each color light is routed in the horizontal direction using a mirror, the optical path is generally long, so that there is a problem that illuminance is reduced. The present invention has been made to solve these problems, and without using a relay optical system or complicated optical path routing, the optical path length of each color light of the color light separation optical system is made equal, and a compact and high-performance It is an object of the present invention to obtain an image forming optical system and a projector using the same.

[0006]

SUMMARY OF THE INVENTION The present invention provides a light source, a color light separation optical system for separating light from the light source into a plurality of color lights, and a plurality of light sources for respectively modulating the color lights separated by the color separation optical system. In an image forming optical system including an electro-optical device and a color synthesizing optical system for synthesizing each color light modulated by the electro-optical device, an optical path of the color light separating optical system is a horizontal optical path and a vertical optical path. Are formed in combination with each other so that the optical path lengths of the respective color lights are equalized. In such an image forming optical system, the color light separating optical system includes, for example, optical paths of first and second color lights formed symmetrically in the same plane, and a central part of these optical paths, and On the other hand, it is possible to provide a configuration including an optical path of the third color light formed with a step. Further, such a color light separation optical system includes a dichroic mirror that separates light from a light source into red, green, and blue light, and two color lights of the color light separated by the dichroic mirror in the same horizontal plane. A mirror that reflects light to form a symmetric optical path, and a mirror that reflects the remaining one color light separated by the dichroic mirror perpendicularly and parallel to the plane to form a convex optical path. This can be realized by the configuration described above.

According to the above-described image forming optical system, the optical path length of each color light can be equalized while the optical path of each color light in the color light separating optical system is shorter than when the optical path is routed in a plane. Are reduced in size, and the brightness and color balance of the image are properly maintained. That is, it is possible to obtain a compact and high-performance image image forming optical system.

Further, the present invention provides a light source, a color light separation optical system for separating light from the light source into a plurality of color lights, and a plurality of electro-optical devices for modulating the color lights separated by the color separation optical system. A color synthesizing optical system for synthesizing each color light modulated by the electro-optical device, wherein at least one of the optical paths of each color light of the color light separation optical system is refracted into the optical path of at least one color light. By disposing media having different rates, the optical path lengths of the respective color lights are made equal. In such an image forming optical system, for example, the color light separating optical system includes an optical path of a first color light formed at the center and an optical path of a second and a third color light formed symmetrically with respect to the optical path. And the second and third
It is possible to make the refractive index of the optical path medium of the first color light larger than the refractive index of the optical path medium of the first color light. Further, such a color light separation optical system is configured to separate a light from a light source into red, green, and blue light, and to reflect two of the color lights separated by the dichroic mirror to reflect each other. A mirror formed in a symmetric optical path, a transparent body having a refractive index larger than air forming an optical path of the two color lights, and a space forming an optical path of the remaining one color light separated by the dichroic mirror. It can be realized by the configuration described above.

According to the above-described image forming optical system, the optical path length of each color light of the color separation optical system can be equalized while the optical path of each color light in the color light separation optical system can be shortened to the minimum necessary. The miniaturization of the forming optical system is further promoted, and the brightness and color balance of the image are properly maintained. That is, it is possible to obtain a compact and high-performance image image forming optical system. In the image forming optical system according to the aspect of the invention, it is preferable that a uniform illumination optical system that uniforms an illuminance distribution of light emitted from the light source is provided between the light source and the electro-optical device. If such a uniform illumination optical system is provided, it is possible to illuminate the electro-optical device with light having a uniform illuminance distribution, so that it is possible to further improve the color balance of an image. In the image forming optical system according to the aspect of the invention, it is preferable that a polarization conversion element that aligns light emitted from the light source into one type of polarized light is provided between the light source and the electro-optical device. . By providing such a uniform illumination optical system, it is possible to illuminate the electro-optical device with light having a uniform polarization direction. Therefore, in an image forming optical system including an electro-optical device that can use only one type of polarized light, such as a liquid crystal panel, the brightness of an image can be approximately doubled.

According to another aspect of the invention, a projector includes the above-described image forming optical system, and a projection lens for projecting an image formed by the image forming optical system. According to the present invention, since the image forming optical system as described above is employed, it is possible to obtain a small-sized projector having an appropriate brightness and color balance of an image. That is, a small-sized and high-performance projector can be obtained.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples.

A. FIG. 1 is a plan view showing an optical system of a projector incorporating an image forming optical system according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view at the center of FIG. The optical system of this projector includes an illumination optical system 100, a color light separation optical system 200,
Liquid crystal light valves 310R, 310G, 310B, cross dichroic prism 42 as color light combining means
0, and a projection lens 570.

The illumination optical system 100 includes, as shown in FIG.
A light source 110, first and second lens arrays 120 and 140 having a plurality of small lenses, a light blocking plate 150, a polarization conversion element array 160 (161 and 162), and a superimposing lens 170 are provided. Note that FIG. 3 shows only main components for describing the function of the illumination optical system 100 for ease of description. The light source 110 includes a light source lamp and a concave mirror. Radial light rays (radiated light) emitted from the light source lamp are reflected by the concave mirror and emitted in the direction of the first lens array 120 as substantially parallel light beams. The first lens array 120 is a lens array in which small lenses having a rectangular outline are arranged in a matrix of M rows in the vertical direction and 2N columns in the horizontal direction. From the center in the lateral direction of the lens, there are N rows to the left and N rows to the right. The external shape of each small lens viewed from the optical axis direction is set so as to be substantially similar to the shapes of the liquid crystal light valves 310R, G, and B. For example, if the aspect ratio (ratio between the horizontal and vertical dimensions) of the image forming areas of the liquid crystal light valves 310R, G, and B is 4: 3, the aspect ratio of each small lens is also set to 4: 3. The second lens array 140 has the same configuration as the first lens array 120. However, the second lens array 140 does not necessarily need to have the same configuration as the first lens array 120, and is omitted when the light emitted from the light source 110 has excellent parallelism. Is also possible.

As shown in FIG. 3, the polarization conversion element array 160 has two polarization conversion element arrays 161 and 162 arranged symmetrically with respect to the optical axis. These polarization conversion element arrays 161 and 162 have a function of converting an incident light beam into one type of linearly polarized light (for example, s-polarized light or p-polarized light) and emitting the same. FIG. 4 is a schematic diagram showing the operation of the polarization conversion element array 161. When non-polarized light (incident light having a random polarization direction) containing an s-polarized light component and a p-polarized light component is incident on the incident surface of the polarization conversion element array 161, the incident light is first transmitted to the polarization separation film 1.
66 separates the light into s-polarized light and p-polarized light. The s-polarized light is reflected almost vertically by the polarization splitting film 166,
The light is emitted after being further reflected by the reflection film 167. On the other hand, the p-polarized light passes through the polarization splitting film 166 as it is. A λ / 2 retardation plate 164 is disposed on the exit surface of the p-polarized light transmitted through the polarization separation film 166.
The polarized light is converted into s-polarized light and emitted. Therefore, most of the light that has passed through the polarization conversion element array 161 is emitted as s-polarized light. When light emitted from the polarization conversion element array 161 is desired to be p-polarized light, the λ / 2 retardation plate 164 may be disposed on the emission surface from which the s-polarized light reflected by the reflection film 167 is emitted. Good.
Further, as long as the polarization directions can be aligned, a λ / 4 retardation plate may be used, or a desired retardation plate may be provided on both the exit surfaces of the p-polarized light and the s-polarized light. The light shielding plate 150 is formed on a substantially rectangular plate-like body so that light is incident only on the light incident surface corresponding to the polarization separation film 166 among the light incident surfaces of the two polarization conversion element arrays 161 and 162. It has a configuration with an opening. Non-polarized light emitted from the light source 110 shown in FIG. 3 is divided into a plurality of partial light beams 102 by a plurality of small lenses of the first lens array 120 and a plurality of small lenses included in the second lens array 140. At the same time, the light is focused near the polarization separation films 166 of the two polarization conversion element arrays 161 and 162. The plurality of partial light beams incident on the two polarization conversion element arrays 161 and 162 are:
As described above, the light is converted into one type of linearly polarized light and emitted. The plurality of partial luminous fluxes emitted from the two polarization conversion element arrays 161 and 162 are superimposed on liquid crystal light valves 310R, 310G and 310B to be described later by the superimposing lens 170. As described above, according to the illumination optical system 100, the liquid crystal light valves 310R, G, and B can be uniformly illuminated by one type of polarized light.

The details of the color light separating optical system 200 are shown in FIGS. As shown in these figures, a first dichroic mirror 211 that reflects red light and transmits green light and a second dichroic mirror 21 that reflects blue light and transmits green light are provided at the entrance of the color light separating optical system 200.
2 are provided. In addition, dichroic mirror 2
Mirrors 223 and 224 for forming the optical path of the red light separated by 11 into a U-shape are arranged on the first dichroic mirror 211 side and the liquid crystal light valve 310R side, respectively. Furthermore, the dichroic mirror 212
The mirrors 221 and 222 for forming the optical path of the blue light separated by the U-shape into a U shape are provided by the second dichroic mirror 2.
12 side and the liquid crystal light valve 310B side. The optical paths of these red light and blue light are formed symmetrically. Further, the optical path length of the red light and the optical path length of the blue light are made equal. On the other hand, the optical path of the green light transmitted through and separated by the first and second dichroic mirrors 211 and 212 is located at the center of the optical path of the red light and the blue light, and as shown in FIG. Mirror 23
1, 232 and 233, 234 form a convex optical path. In the present embodiment, these mirrors 23
By changing the installation positions of 1, 232, 233, and 234, the path length of the convex portion is adjusted so that the optical path length of the green light becomes equal to the optical path length of the red light and the blue light.

Liquid crystal light valves 310R, 310G, 3
10B is disposed for each of red, green, and blue light, and includes a liquid crystal panel and polarizing plates provided on the light incident surface side and the light emission surface side. In FIGS. 1 to 5, the liquid crystal panel and the pair of polarizing plates are shown as being integrated, but the polarizing plate and the liquid crystal panel may be arranged separately.

The cross dichroic prism 420 is
It is a combination of four right-angle prisms, and a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are formed in an approximately X shape along the interface of the four right-angle prisms. ing. With these dielectric multilayer films, 3
The modulated lights of the colors are combined to form a combined light for projecting a color image.

Next, the function of the optical system of the projector configured as described above will be described.

The light beam emitted from the superimposing lens 170 and entering the color light separation optical system 200 firstly transmits a green light and reflects red light, and a second dichroic mirror 211 transmits green light and reflects blue light. 2
12, the light is separated into three color lights of red, green and blue.

The red light reflected by the first dichroic mirror 211 is, as shown in FIG.
4 and then reflected by the liquid crystal light valve 310R.
Incident on. The blue light reflected by the second dichroic mirror 211 is, as shown in FIG.
After being respectively reflected by the liquid crystals 1 and 222, the light enters the liquid crystal light valve 310B. Further, the green light transmitted through the first and second dichroic mirrors 211 and 212 is sequentially reflected by mirrors 231, 232 and 233 and 234 arranged vertically in two stages as shown in FIGS. 1 and 2. After that, the light enters the liquid crystal light valve 310G.

Liquid crystal light valves 310R, 310G, 3
Each of the liquid crystal panels constituting 10B has a function as an electro-optical device that modulates incident light in accordance with given image information (image signal), and each color light incident thereon receives the given image information. To form an image of each color light.

Further, each liquid crystal light valve 31
Each modulated light emitted from OR, 310G, and 310B is
The light enters the cross dichroic prism 420 and is synthesized, and the synthesized light is projected on the screen by the projection lens 570 to form a color image on the screen.

According to this embodiment, the optical path length of each color light of the color light separation optical system can be equalized while the optical path of each color light in the color light separation optical system can be made shorter than when the light path is routed in a plane. The system is made compact and the brightness and color balance of the image can be maintained properly. That is, it is possible to obtain a compact and high-performance image image forming optical system and a projector using the same.

B. Second Embodiment FIG. 5 is a plan view showing an optical system of a projector incorporating an image forming optical system according to a second embodiment of the present invention. This optical system has the same configuration as that of the first embodiment described above, except for the configuration of the color light separation optical system 200A. In the description of the present embodiment and FIG. 5, the same components as those of the first embodiment described above
The same reference numerals as those used in FIGS. 1 to 4 are used, and the detailed description is omitted. The speed of light depends on the refractive index of the medium through which the light travels. For example, if the refractive index of the medium is larger than air,
The speed of light traveling in the medium is faster than the speed of light traveling in air. As a result, the optical path length (optical distance) of light traveling through the medium can be considered to be shorter than the geometric distance. The present embodiment utilizes this property of light. In the present embodiment, a first dichroic mirror 211 that reflects red light and transmits green light and a second dichroic mirror 2 that reflects blue light and transmits green light are provided at the entrance of the color light separating optical system 200A.
12 are provided. Further, mirrors 223 and 224 for forming the optical path of the red light separated by the dichroic mirror 211 into a U-shape are arranged on the first dichroic mirror 211 side and the liquid crystal light valve 310R side, respectively. Furthermore, the dichroic mirror 21
Mirrors 221 and 222 for forming the optical path of the blue light separated by 2 in a U-shape are disposed on the second dichroic mirror 212 side and the liquid crystal light valve 310B side, respectively. The optical paths of these red light and blue light are formed symmetrically. Further, the optical path length of the red light and the optical path length of the blue light are made equal. On the other hand, the optical paths of the green light transmitted through the first and second dichroic mirrors 211 and 212 are linearly formed in a space 243 provided at the center of the red and blue light paths. I have.

In this example, the geometric distance of the light path of the green light is shorter than the geometric distance of the light path of the red light and the blue light, but the medium of the light path of the green light is air (having a refractive index of about 1). ), The optical path of red light or blue light is formed of glass with a refractive index larger than that of air, and the size of the glass is adjusted to reduce the optical path length of red light or blue light to that of green light. It is equal to the optical path length. In addition, as such a medium, a transparent substance such as sapphire, crystal, or water can be used in addition to glass. Further, any of a configuration in which these media form the entire optical path of red light and blue light or a configuration in which a part of the optical path is formed is possible.

According to the configuration of this embodiment, a medium having a large refractive index is used for the optical path, so that the optical path of each color light in the color light separation optical system can be shortened to the minimum necessary, while each color of the color separation optical system can be reduced. Since the optical path lengths of the light can be made equal, the image forming optical system can be configured more compactly, and the brightness and color balance of the image can be properly maintained. That is, it is possible to obtain a compact and high-performance image image forming optical system and a projector using the same.

The present invention is not limited to the above-described embodiment, but can be embodied in various modes without departing from the gist thereof. For example, the following modifications are possible. (1) In the above embodiment, the two lens arrays 120 and 140 that divide the light of the light source 110 into a plurality of partial light beams are used. However, the present invention can be applied to a projector that does not use such a lens array. It is. Also, instead of the two lens arrays 120 and 140, like these lens arrays, rod-shaped optics having a function of dividing the light from the light source 110 into a plurality of partial light beams and forming a plurality of condensed images. An element (a solid rod made of glass or a hollow rod constituted by a plurality of reflection mirrors) may be used. (2) In the above embodiment, the polarization conversion element array 160 that adjusts the light from the light source 110 to one type of polarized light is used.
The present invention can be applied to a projector that does not use a projector. (3) In the above embodiment, the first dichroic mirror 211 that reflects red light and transmits green light, and the second dichroic mirror 21 that reflects blue light and transmits green light
2 and these dichroic mirrors 2
11 and 212 are cross dichroic prisms 420
Similarly to the above, it may be formed as a dielectric multilayer film in the prism. (4) In the above embodiment, the light path of the green light is located at the center of the light path of the red light and the blue light, but the light path of the red light and the light path of the blue light are located at the center of the light paths of the other two color lights. It may be configured to be located. Such a configuration includes the first dichroic mirror 211 and the second dichroic mirror 21.
By changing the wavelength selection characteristic of No. 2, it can be easily realized. (5) In the above embodiment, an example in which the present invention is applied to a projector using a transmissive liquid crystal panel has been described. However, the present invention can also be applied to a projector using a reflective liquid crystal panel. It is possible. Further, as described later, the electro-optical device is not limited to a liquid crystal panel. Here, “transmission type” means that an electro-optical device such as a liquid crystal panel transmits light, and “reflection type” means that an electro-optical device such as a liquid crystal panel reflects light. It is a type. In a projector employing a reflection type electro-optical device, a dichroic prism is used as a color light separating means for separating light into three colors of red, green and blue, and synthesizes modulated three colors of light. And may also be used as a color light combining means that emits light in the same direction.

The electro-optical device for light modulation is not limited to a liquid crystal light valve using a liquid crystal panel, but may be, for example, a device using a micro mirror. Also, the prism that is a color light combining optical system is not limited to a dichroic prism in which two types of color selection surfaces are formed along the bonding surface of the four triangular prisms, but a dichroic prism with one type of color selection surface and a polarization type. It may be a beam splitter. Alternatively, the prism may be such that a light-selecting surface is arranged in a substantially hexahedral light-transmitting box and a liquid is filled therein.

Further, the projector includes a front projector for projecting from a direction in which a projected image is observed,
There is a rear projector that projects from the side opposite to the direction in which the projected image is observed, but the configuration described in the above embodiment can be applied to any of them.

[0030]

According to the present invention, the optical path length of each color light of the color light separation optical system can be made equal without using a relay optical system or a complicated and complicated optical path, so that a compact and high-performance image forming apparatus can be formed. An optical system and a projector using the same can be obtained.

[Brief description of the drawings]

FIG. 1 is an exemplary plan view showing an optical system of a projector incorporating an image forming optical system according to a first embodiment of the present invention.

FIG. 2 is a central sectional view of the optical system of FIG. 1;

FIG. 3 is a schematic diagram showing the operation of the illumination optical system.

FIG. 4 is a schematic view showing the operation of a polarizing element array.

FIG. 5 is a plan view showing an optical system of a projector incorporating the image forming optical system according to the second embodiment of the present invention.

FIG. 6 is a plan view showing an optical system of a known projector.

[Explanation of symbols]

 Reference Signs List 100 illumination optical system 110 light source 120 first lens array 140 second lens array 150 light shielding plate 160 polarization conversion element array 170 superimposing lens 200, 200A color light separation optical system 211 first dichroic mirror 212 second dichroic mirror 221, 222, 223 224 mirror 231, 232, 233, 234 mirror 241, 242 glass 243 space 310R, 310G, 310B liquid crystal light valve 420 cross dichroic prism 570 projection lens

Claims (9)

[Claims] A light source; a color light separation optical system for separating light from the light source into a plurality of color lights; a plurality of electro-optical devices for modulating the color lights separated by the color separation optical system; A color synthesizing optical system for synthesizing each color light modulated by the device, wherein an optical path of the color light separating optical system is formed by combining a horizontal optical path and a vertical optical path. An optical path length of each color light is equalized. 2. The color light separating optical system has an optical path of first and second color lights formed symmetrically in the same plane, and a step in the center of these optical paths with respect to the plane. The image forming optical system according to claim 1, further comprising an optical path of the third color light formed by forming. 3. A dichroic mirror for separating light from a light source into red, green, and blue light, and two of the color lights separated by the dichroic mirror.
A mirror that reflects two color lights in the same horizontal plane to form optical paths symmetrical to each other; and a convex optical path that reflects the remaining one color light separated by the dichroic mirror perpendicularly and parallel to the plane. The image forming optical system according to claim 2, further comprising: a mirror that forms: 4. A light source, a color light separation optical system for separating light from the light source into a plurality of color lights, a plurality of electro-optical devices for modulating the color lights separated by the color separation optical system, respectively, and the electro-optic. A color synthesizing optical system for synthesizing each color light modulated by the device, wherein a medium having a different refractive index in at least one color light optical path among the optical paths of each color light of the color light separation optical system. Wherein the optical path lengths of the respective color lights are made equal. 5. The color light separation optical system includes an optical path of a first color light formed in the center, and optical paths of second and third color lights formed symmetrically with respect to the optical path. 5. The image forming optical system according to claim 4, wherein the refractive index of the optical path medium of the second and third color lights is larger than the refractive index of the optical path medium of the first color light. 6. A dichroic mirror for separating light from a light source into red, green, and blue light, and two of the color lights separated by the dichroic mirror.
A mirror that reflects two color lights to form optical paths symmetric to each other, a transparent body that forms a light path of the two color lights and has a refractive index greater than that of air, and an optical path of the remaining one color light separated by the dichroic mirror The image forming optical system according to claim 5, further comprising: a space that forms 7. A uniform illumination optical system for equalizing an illuminance distribution of light emitted from the light source is provided between the light source and the electro-optical device. 7. The image forming optical system according to any one of 6. 8. A polarization conversion element for aligning light emitted from the light source into one type of polarized light is provided between the light source and the electro-optical device. 8. The image forming optical system according to any one of 7. 9. A projector comprising: the image forming optical system according to claim 1; and a projection lens configured to project an image formed by the image forming optical system.