JP2006251121A - Optical element, optical modulation device using the same, and projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized optical element capable of performing efficient color separation of incident light. <P>SOLUTION: In the light which is made obliquely incident for the optical axis OA of a micro lens 13, blue color is transmitted by a blue color selective transmission part 16 arranged on an outgoing surface 30 of a quartz glass plate 12 and remaining components are reflected. Reflection light is reflected to a position different from the first blue color selective transmission part 16 by a reflection part 19 disposed between a color filter 50 and a microlens 13 and a green color is transmitted by a green color selective transmission part 17. Likewise, the reflection light is made incident to a red color selective transmission part 18 by a reflection part 19 and red color is transmitted. Accordingly, the small-sized optical element permits efficient color separation. Further, by the use of one optical element 10, color separation can be performed and the miniaturization of an optical system can be also permitted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical element for color-separating incident light, an optical modulation device using the same, and a projector.

  A projector or the like uses a liquid crystal light valve, which is an optical modulation device that adjusts the amount of light transmitted from a light source for each pixel. In order to perform color display, it is necessary to use an optical element for color separation in combination with a liquid crystal light valve. Here, when an absorption type color filter made of a dye or the like is used as the optical element, the amount of transmitted light is reduced by absorption. In addition, there is a problem that the life of a liquid crystal light valve that is close by the deterioration of the dye due to light absorption and the heat generation of the color filter is shortened.

Therefore, in the projector, the light from the light source is separated into red, green, and blue by combining a selective transmission filter made of a dielectric multilayer film that transmits the transmission component and reflects the components other than the transmission component. Then, after adjusting the amount of transmitted light with three liquid crystal light valves corresponding to the respective colors, a method of combining red, green and blue again and projecting is widely used.
However, this method increases the number of parts and makes it difficult to reduce the size of the optical system. In order to solve this problem, a method using one liquid crystal light valve and a selective transmission filter has been studied.

As a method using a large selective transmission filter, a method is known in which color separation is performed using three selective transmission filters having different angles with respect to light from a light source (see, for example, Patent Document 1). In this method, red, green, and blue reflected by each selective transmission filter enter the microlens array provided on the incident light side of the liquid crystal light valve at different angles for each color, Concentrate on the pixel corresponding to the color. Based on the image information, the amount of transmitted light is adjusted by the pixel for each color.
In addition, a color filter that combines a small selective transmission part according to the pixel of the liquid crystal light valve is formed on the incident light side, and the light reflected by the color filter is reflected again toward the color filter near the light source to reduce the incident light amount. A method of ensuring is known (see, for example, Patent Document 2).
Furthermore, there is also known a method in which a microlens array and a microprism are provided for each pixel on the incident light side of the liquid crystal light valve, and the incident light is separated into red, green and blue by a selective transmission portion formed on the microprism. (For example, see Patent Document 3).

Japanese Patent Laid-Open No. 9-114023 (page 6, paragraph numbers [0046] to [0053], FIG. 1) JP-A-9-159987 (page 3, paragraph numbers [0010] [0018], FIG. 2) JP-A-11-338379 (pages 5 to 6, paragraph numbers [0029] to [0031], FIG. 2)

In Patent Document 1, light from a light source is incident on a liquid crystal light valve by changing the angle for each component by a large selective transmission filter. The large selective transmission filter is disposed away from the liquid crystal light valve, and each optical element is not positioned on a straight line. Therefore, there is a problem that it is difficult to adjust and downsize the optical system.
Further, in Patent Document 2, a mirror for reflecting the reflected light from the color filter again in the vicinity of the light source is necessary, which increases the number of components and makes it difficult to downsize the optical system. In addition, since the distance from the reflecting mirror to the liquid crystal light valve is long, there is a problem that the amount of incident light is lost and the light use efficiency does not increase.
Further, in Patent Document 3, a complicated process of forming the microprism and the selective transmission portion is required, and the accuracy of the microprism is required, and it is difficult to improve the utilization efficiency of incident light.

  An object of the present invention is to provide a small optical element that can efficiently color-separate incident light, an optical modulation device using the same, and a projector.

  The optical element of the present invention is an optical element for color-separating the light collected by the microlens of the microlens array, and the light collected by making light incident obliquely with respect to the optical axis of the microlens. A color filter having a selective transmission part for color separation is disposed on the light emission surface, and the light reflected by the selective transmission part between the color filter and the microlens array is directed again to the selective transmission part. A reflection part for reflection is provided.

According to the present invention, light is incident at an angle with respect to the optical axis of the microlens, so that the light is collected at a position shifted from the optical axis of the microlens. The condensed light reaches the color filter arranged on the exit surface. The color filter has a plurality of selective transmission portions that transmit different colors, and the transmission components are transmitted by the selective transmission portions, and the remaining components are reflected. The reflected light is reflected at an angle with respect to the optical axis. The reflected light is reflected again at a position different from that of the first selective transmission part by the reflection part provided between the color filter and the microlens array. If a selective transmission part that selectively transmits a color different from that of the first selective transmission part is arranged at that position, a different transmission component is transmitted. That is, by combining different selective transmission parts, incident light is color-separated and emitted from the emission surface.
Therefore, in the present invention, incident light is incident obliquely and color separation is performed using reflection between the microlens and the color filter, so that the optical element for color separation is thin and small. In addition, since the selective transmission portions are formed side by side in the same plane to form a color filter, the color filter can be easily created and is thin. Further, color separation is performed by one optical element, and the optical system can be miniaturized.

In the present invention, it is preferable that the color filter is formed on the other surface side of the bonding surface of the transparent plate bonded to the microlens array to the microlens array.
In the present invention, a color filter is formed on the exit surface of the transparent plate. Therefore, it is only necessary to form a color filter by forming a plurality of selective transmission portions on a plane, and the selective transmission portions can be formed with high accuracy by a simple process. Further, if the reflecting portion is formed on the surface opposite to the exit surface of the transparent plate, it is easy to align with the selective transmission portion at the time of formation, and the distance between the selective transmission portion and the reflection portion can be kept constant. Therefore, the incident light is efficiently color-separated.

In the aspect of the invention, it is preferable that the reflection portion is formed with a light transmission portion for allowing the light collected by the microlens to pass through the color filter.
In the present invention, the light transmitting portion formed in the reflecting portion serves as a diaphragm, and the light collected by the microlens reaches the selective transmitting portion determined by the color filter. Therefore, the transmitted light can be used effectively and color separation can be performed efficiently.

In the present invention, it is preferable that a micro lens is formed in the light transmitting portion.
In this invention, the light condensed by the microlens is converted into parallel light in the same direction as the incident light by the microlens. Therefore, light leakage and stray light until reaching the selective transmission part are reduced, and color separation is performed efficiently.

In the present invention, it is preferable that the aperture of the micro lens is 1/3 or less of the aperture of the micro lens.
In the present invention, since the light collected by the microlens is divided into 1/3 or less, the incident light is color-separated into the three primary colors necessary for color display.

The light modulation device of the present invention includes the above-described optical element.
According to this invention, since the light modulation device is integrally provided with a small optical element for color separation, the amount of transmitted light of each color component is adjusted by one light modulation device. Therefore, the number of parts is reduced.

A projector according to the present invention includes the above-described light modulation device.
According to the present invention, since the light modulation device and the optical element for color separation are integrated, the optical system is arranged on a straight line, and the projector is downsized.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic plan view showing a projector 1 according to this embodiment.
In FIG. 1, a projector 1 includes an illumination optical system 100, an optical element 10 for color-separating incident light, a liquid crystal light valve 20 as an optical modulator that adjusts the amount of transmitted light for each pixel, and projection. And a lens system 150.

  The illumination optical system 100 includes a light source 110, a first lens array 120, a second lens array 130, and a collimator lens 140. The illumination optical system 100 is an integrator optical system for uniformly illuminating the optical element 10.

The light source 110 includes a light source lamp 111 as a radiation light source and a concave mirror 112 that emits light emitted from the light source lamp 111 as parallel light.
As the light source lamp 111, an ultrahigh pressure mercury lamp is used. The concave mirror 112 is preferably a parabolic mirror.

In the first lens array 120, a plurality of small lenses 121 are arranged in a matrix. On the other hand, a plurality of small lenses 131 are arranged in the second lens array 130 so as to correspond to the plurality of small lenses 121. The parallel light emitted from the light source 110 is divided into a plurality of partial lights corresponding to the small lenses 121 by the first lens array 120 and condensed so as to enter each small lens 131 of the second lens array 130. Is done. Each partial light emitted from the small lens 131 is collimated by the collimator lens 140. The optical element 10 is illuminated with uniform brightness.
If a polarization beam splitter (not shown) is added to the illumination optical system 100 to align the polarization direction of the parallel light emitted from the light source 110, only one polarizing plate is required for the liquid crystal light valve 20. The amount of light transmitted through the liquid crystal light valve 20 increases.

The optical element 10 and the liquid crystal light valve 20 are aligned so that the color-separated light enters each pixel of the liquid crystal light valve 20, and are bonded together with an adhesive. The collimator lens 140 is arranged at an angle θ with respect to the parallel light emitted from the collimator lens 140.
Note that the optical element 10 and the liquid crystal light valve 20 may not be bonded together with an adhesive, and may be disposed close to each other. In this case, conduction of heat generated in the optical element 10 to the liquid crystal light valve 20 can be prevented.

FIG. 2 is a schematic perspective view of the optical element 10 according to the present embodiment.
In FIG. 2, the optical element 10 includes a microlens array 11 and a quartz glass plate 12 as a transparent plate. These are bonded together with a transparent adhesive.
In the microlens array 11, microlenses 13 are regularly formed in a matrix. Here, in FIG. 2, the number of microlenses 13 is shown as a schematic number. Actually, one-third of the number of pixels of the liquid crystal light valve 20 is arranged, and one microlens 13 corresponds to three pixels of the liquid crystal light valve 20.

3 is a schematic cross-sectional view of the optical element 10 according to the present embodiment, and FIG. 4 is a schematic plan view of the optical element 10 viewed from the microlens array 11 side.
The microlens array 11 includes a microlens 13 and a microlens 14. The microlens 13 is disposed on the incident light side, and the microlens 14 is disposed on the quartz glass plate 12 side.

The thickness of the microlens array 11 is set to a distance until incident light incident at an angle θ with respect to the optical axis OA of the microlens 13 is condensed to an area of approximately 1/3 of the opening area of the microlens 13. ing. In FIG. 3, blue (B) of incident light is indicated by a two-dot chain line, green (G) is indicated by a one-dot chain line, and red (R) is indicated by a solid line. Further, the angle θ shown in FIG. 3 is the same as the angle θ shown in FIG.
The micro lens 14 is provided at a place where incident light is collected by the micro lens 13. The light collected by the micro lens 14 is made parallel to the incident light.
Here, the micro lens 14 is formed of a material having a refractive index different from that of the micro lens 13. For example, if the refractive index of the adhesive that bonds the microlens array 11 and the quartz glass plate 12 is different from the refractive index of the microlens 13, the shape of the microlens 14 is the same as that of the microlens 14 in a corresponding place in advance. The microlens 14 can also be formed by providing a depression and filling the depression with an adhesive simultaneously with the adhesion.

The quartz glass plate 12 includes a color filter 50 and a reflection unit 19. The color filter 50 includes a blue selective transmission unit 16, a green selective transmission unit 17, and a red selective transmission unit 18 corresponding to one microlens 13.
The light collimated with the incident light by the micro lens 14 travels through the quartz glass plate 12. On the emission surface 30 from which the parallel light is emitted from the quartz glass plate 12, a blue selective transmission portion 16 having an area substantially the same as the area collected by the microlens 13 is disposed. In the blue selective transmission part 16, blue is transmitted, and green and red other than blue are reflected at a reflection angle θ of the same angle as the incident angle θ. The reflected blue color and red color proceed to the reflection part 19 provided on the surface of the quartz glass plate 12 facing the emission surface 30.

The reflection part 19 is formed with a light transmission part 15 for allowing the light collected by the microlens 13 to pass through the color filter 50. In the present embodiment, the minute lens 14 is formed in the light transmitting portion 15, but the minute lens 14 may be omitted.
In FIG. 3, the reflection part 19 is formed to have an area twice that of the blue selective transmission part 16. In addition, the area ratio in this embodiment is not limited to these.
Blue and red are reflected at the reflection angle θ by the half area portion of the reflection portion 19 and proceed to the emission surface 30 again. The green selective transmission portion 17 is disposed on the emission surface 30 where blue and red reach, and green is transmitted and red is reflected at the reflection angle θ. The red color is again reflected at the reflection angle θ by the reflecting portion 19 and returns to the emission surface 30. In this place, a red selective transmission portion 18 is disposed, and the red color is transmitted.
The blue selective transmission part 16, the green selective transmission part 17, and the red selective transmission part 18 are arranged side by side, and the combined area is formed in the same area as the opening of the microlens 13 and enters the microlens 13. The transmitted light is transmitted through these three filters.
In consideration of chromatic aberration due to the optical path difference, it is preferable to first selectively transmit blue, which is light with a short wavelength and a large refractive power (long focal length).

  Further, the incident angle θ of the incident light is preferably 2 to 20 °. If the angle is smaller than 2 °, the distance required for color separation (thickness of the quartz glass plate 12) becomes long. If the angle is larger than 20 °, the distance in the horizontal direction between the microlens array 11 and the quartz glass plate 12 becomes large. Become.

5A shows the spectral characteristics of the blue selective transmission section 16, FIG. 5B shows the spectral characteristics of the green selective transmission section 17, and FIG. 5C shows the spectral characteristics of the red selective transmission section 18. The horizontal axis indicates the wavelength, and the vertical axis indicates the transmittance.
The blue selective transmission part 16 transmits light with a wavelength of about 400 nm to 500 nm, the green selective transmission part 17 transmits light with a wavelength of about 500 nm to 600 nm, and the red selective transmission part 18 has a wavelength of about 600 nm to 700 nm. Transmits light of wavelength.

  These selective transmission portions 16, 17, and 18 are formed of a dielectric multilayer film. A so-called lift-off method can be used as a method of forming the selective transmission portions 16, 17, and 18. Specifically, a resist or metal film (aluminum, copper, etc.) patterned in advance is formed on the quartz glass plate 12 at a portion other than the portion where the blue selective transmission portion 16 is formed. After that, a dielectric multilayer film is formed on the entire surface, and the dielectric multilayer film other than the portion where the blue selective transmission portion 16 is formed is removed together with a resist or the like by etching, whereby the blue selective transmission portion 16 is formed at a predetermined position. Is formed. Each filter is formed by repeating this procedure for each dielectric multilayer film formation. The resist or the like to be formed should have the same film thickness as that of the dielectric multilayer film.

  The dielectric multilayer film is formed by alternately laminating a low refractive index material and a high refractive index material according to a design film thickness. As the membrane configuration, a well-known permselective filter membrane configuration can be used. For example, the blue selective transmission part 16 uses tantalum oxide as a high refractive index material, and silicon dioxide as a low refractive index material, and a total of 38 layers of tantalum oxide and silicon dioxide are alternately stacked in order from the quartz glass plate 12 side. Is obtained. The film thickness of the blue selective transmission part 16 was 3.1 μm.

Here, tantalum oxide, titanium oxide, niobium oxide, or the like can be used as the high refractive index substance, and silicon dioxide or magnesium fluoride can be used as the low refractive index substance.
These materials can be formed by a reactive sputtering method, an ion plating method, or an ion assist method. The film formation temperature is a low temperature (150 ° C. at which the resist does not damage when a resist is used. The following film formation is performed.

As the reflection unit 19, a cold mirror made of a dielectric multilayer film is used which can obtain high reflection in the visible light region and can design reflection characteristics according to the incident angle of incident light. For example, if the design is such that only visible light is reflected and infrared rays are transmitted, the infrared rays reaching the liquid crystal light valve 20 are blocked, and the temperature rise of the liquid crystal light valve 20 can be prevented.
Similar to the selective transmission filter, the cold mirror is formed of a combination of a high refractive index material and a low refractive index material. What is necessary is just to form by the film | membrane structure obtained by design.
The reflection part 19 may be a mirror of an aluminum or silver metal film that can be easily etched.
In addition, the reflection part 19 may be provided in the microlens array 11, and may be provided in the quartz glass plate 12. FIG. Providing the quartz glass plate 12 facilitates alignment with the microlens array 11.

  The transmitted light amount of the color separated by the optical element 10 is adjusted by the action of each pixel based on the image information, and is projected as an image on the screen SC through the projection lens system 150.

According to this embodiment, there are the following effects.
(1) When light is incident obliquely with respect to the optical axis OA of the microlens 13, the light is collected at a position shifted from the optical axis OA of the microlens 13. The condensed light is transmitted by the blue selective transmission portion 16 disposed on the emission surface 30 of the quartz glass plate 12 and the rest is reflected. The reflected light is reflected at an angle θ with respect to the optical axis OA. The reflected light is reflected at a position different from the first blue selective transmission section 16 by the reflection section 19 provided between the color filter 50 and the microlens 13, and the first blue selective transmission section 16 is at that position. If different green selective transmission parts 17 are arranged, green is transmitted. The remaining components are also reflected in the same manner, and enter the red selective transmission unit 18 by the reflection unit 19, and the red color is transmitted. Therefore, color separation can be performed efficiently over a short distance. Further, color separation is performed by one optical element 10, and the optical system can be miniaturized.

(2) The color filter 50 is formed on the emission surface 30 of the quartz glass plate 12. Therefore, a plurality of selective transmission portions 16, 17, and 18 can be formed on a plane, and the selective transmission portions 16, 17, and 18 can be formed with a simple and accurate process.

(3) The light condensed by the microlens 13 can be converted into parallel light in the same direction as the incident light by the microlens 14, and light leakage and stray light until reaching the blue selective transmission section 16 are reduced and efficiency is reduced. Good color separation.

(4) The light transmitting portion 15 formed in the reflecting portion 19 serves as a diaphragm, and the light condensed by the microlens 13 selectively reaches the color filter 50. Therefore, the light path can be easily controlled by the light transmitting portion 15, and the light can be guided to the predetermined selective transmitting portion, and color separation can be performed efficiently.

(5) Since the light condensed by the microlens 13 is divided into 1/3 or less, the incident light can be separated into three primary colors (R, G, B) necessary for color display.

(6) Since the liquid crystal light valve 20 includes the small optical element 10 for color separation, the amount of transmitted light of each color component can be adjusted with one liquid crystal light valve 20. Therefore, the number of parts can be reduced.

(7) Since the liquid crystal light valve 20 and the optical element 10 for color separation are integrated, the optical system can be arranged on a straight line, and the projector 1 can be downsized.

It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
[Modification 1]
For example, in the above embodiment, color separation is performed using three types of filters, but in the present invention, color separation may be performed using two types of filters.
6A and 6B show two types of spectral characteristics. (A) shows the same spectral characteristics of the blue selective transmission section 16 as in the embodiment, and (B) shows the spectral characteristics of the blue and green selective transmission sections 40.
The same blue selective transmission part 16 as in the embodiment is arranged at the same position as in the embodiment, and the blue and green selective transmission parts 40 are arranged at the same position as the green selection transmission part 17. And nothing is arranged in the place where the red selective transmission portion 18 was provided. Even in such a configuration, when incident light reaches the blue and green selective transmission section 40, blue is transmitted and the blue component is eliminated, only green is transmitted and red is reflected. The red color is reflected by the reflecting portion 19 and passes through the exit surface 30 as it is. In such a configuration, since the number of selective transmission portions is small, the processing can be facilitated.

The selective transmission part is not limited to one that transmits blue, green, and red, but can be selected depending on the application.
In addition, in the above-described embodiment, only an example of a front type projector that performs projection from the direction in which the screen SC is observed has been described. It can also be applied to other projectors.

Further, the best configuration, method and the like for carrying out the present invention have been disclosed in the above description, but the present invention is not limited to this. That is, the invention has been illustrated and described primarily with respect to particular embodiments, but may be configured for the above-described embodiments without departing from the scope and spirit of the invention. Various modifications can be made by those skilled in the art in terms of materials, quantity, and other detailed configurations.
Therefore, the description limited to the shape, material, etc. disclosed above is an example for easy understanding of the present invention, and does not limit the present invention. The description by the name of the member which remove | excluded the limitation of one part or all of such restrictions is included in this invention.

  The present invention can be used not only for a projector but also for a display device using a color filter such as a direct-view liquid crystal device.

1 is a schematic plan view showing a projector according to an embodiment of the invention. 1 is a schematic perspective view showing an optical element according to an embodiment of the present invention. 1 is a schematic cross-sectional view showing an optical element according to an embodiment of the present invention. 1 is a schematic plan view showing an optical element according to an embodiment of the present invention. The graph which shows the spectral characteristic concerning embodiment of this invention. The graph which shows the spectral characteristic concerning the modification of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Projector, 10 ... Optical element, 11 ... Micro lens array, 12 ... Quartz glass plate as a transparent plate, 13 ... Micro lens, 14 ... Micro lens, 15 ... Translucent part, 16 ... Blue selective transmission part, 17 ... Green selective transmission part, 18 ... Red selective transmission part, 19 ... Reflection part, 20 ... Liquid crystal light valve as an optical modulator, 30 ... Emission surface, 50 ... Color filter, OA ... Optical axis.

Claims (7)

An optical element for color-separating light collected by a microlens of a microlens array,
A color filter having a selective transmission portion that is incident obliquely with respect to the optical axis of the micro lens and separates the collected light is disposed on the light exit surface,
An optical element, characterized in that a reflection unit is provided between the color filter and the microlens array to reflect light reflected by the selective transmission unit again toward the selective transmission unit. The optical element according to claim 1,
The optical element, wherein the color filter is formed on the other surface side of the bonding surface of the transparent plate bonded to the microlens array to the microlens array. The optical element according to claim 1 or 2,
The optical element, wherein the reflection part is formed with a light transmission part for allowing the light collected by the microlens to pass through the color filter. The optical element according to claim 3.
An optical element, wherein a microlens is formed in the light transmitting part. The optical element according to claim 4,
The aperture of the micro lens is 1/3 or less of the aperture of the micro lens. An optical modulation device comprising the optical element according to any one of claims 1 to 5. A projector comprising the optical modulation device according to claim 6.

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