JP2006349714A - Illuminator and projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact illuminator using a compact light source, and achieving the facilitation of the control of an incidence angle on an object to be illuminated and also restraint of loss and heat generation, and to provide a projector using the illuminator. <P>SOLUTION: Light beams made incident on polarized light conversion devices 61, 63 and 65 from respective light source units 21a, 23a and 25a are distributed within a range of about ±20° with a system optical axis SA as center because of using LEDs 21f, 23f and 25f. Therefore, by making the design values of multilayered films of polarized light separation films 61a1, 63a and 65a fit to the wavelength of each color, the polarized light separation characteristic dedicated to each color is given, and tolerance to the distribution of the incidence angle is made large. Thus, illuminating light is efficiently taken out as a whole. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an illumination device for illuminating a liquid crystal light valve and other light modulation devices, and a projector incorporating the illumination device.

  As a first projector, a light source lamp is disposed on one end side of the rod integrator, and a polarization separating prism member is disposed on the other end side of the rod integrator, and the polarization directions of a pair of polarized light passing through the prism member are matched. Then, there exists what illuminates by superimposing the illumination area by combining with a lens (see Patent Document 1).

  As a second projector, there is a projector that restricts light source light to a specific polarization direction with a polarizing filter and guides it to the optical path of each color with a polarizing beam splitter (see Patent Document 2). In this projector, a narrow-band phase difference plate that rotates the polarization direction with a specific color is provided before and after the polarization beam splitter to easily achieve color separation and color synthesis.

As a third projector, a liquid crystal display element for red light is illuminated by an R color LED array and a waveguide block, and a liquid crystal display element for green light is illuminated by a G color LED array and a waveguide block. There is one that illuminates a liquid crystal display element for blue light using a B-color LED array and a waveguide block (see Patent Document 3).
JP 2002-268008 A JP 2000-2284228 A Japanese Patent Laid-Open No. 2000-112031

  However, in the first and second projectors described above, a lamp that generates white light is used as the light source, so that the light source is easily increased in size and is not easily maintained.

  In the first projector, since the prism member is disposed at the exit of the rod integrator, it is necessary to combine the polarized light emitted from the prism. For this reason, there exists a problem that the spread range of the incident angle to the light modulation device that is the illumination object differs depending on the direction, and a problem that the periphery of the light modulation device is enlarged.

  Further, the second projector has a large light loss due to the polarizing filter, and there is a possibility that heat generation of the polarizing filter becomes a problem.

  Further, since the third projector uses the light of the LED array as it is without polarization, the loss of light amount is large, and heat generation of the liquid crystal display element may become a problem. Although it is conceivable to provide a polarization conversion element composed of a polarizing beam splitter or the like between the LED array and the waveguide block, the angle range of the light flux from the LED array usually tends to be widened. Due to the characteristics of the general-purpose polarizing beam splitter, the polarization conversion efficiency is lowered.

  Accordingly, the present invention provides a small illuminating device using a small light source, an illuminating device that can easily control an incident angle to an object to be illuminated, and has little loss and heat generation, and a projector using the illuminating device. The purpose is to do.

  The present invention also provides a small illuminating device using a small light source, an illuminating device that can efficiently use light source light with high polarization conversion efficiency, and a projector using the same. With the goal.

  In order to solve the above problems, an illumination device according to the present invention includes: (a) a light source for each color that generates, for example, each color light having a peak in a different predetermined wavelength region as a light source light; and (b) a light source for each color. For each color having polarization separation characteristics adapted to the wavelength of each emitted color light, and separating each color light which is randomly polarized light into first linearly polarized light and second linearly polarized light whose polarization directions are orthogonal to each other And a polarization conversion device for each color that includes a phase element for each color that aligns the polarization directions of the first linearly polarized light and the second linearly polarized light for each color.

  In the illumination device, in the polarization conversion device, each color light is separated into the first and second linearly polarized light whose polarization directions are orthogonal to each other by the polarization separation film for each color, and the first and second phase elements for each color Since the polarization direction of the second linearly polarized light is aligned for each color, efficient polarization conversion of the light source light is possible, and bright illumination is possible. Here, the polarization separation film for each color provided in the polarization conversion device has polarization separation characteristics adapted to the wavelength of each color light emitted from the light source for each color, thus improving the polarization conversion efficiency for each color individually As a whole, brighter illumination is possible.

  Further, according to a specific aspect or aspect of the present invention, the illumination device further includes a uniformizing optical system that is arranged in a front stage and / or a rear stage of the polarization conversion device and divides each color light into partial light beams and superimposes them. In this case, uniform bright polarized light can be obtained.

  In another aspect of the present invention, the polarization separation characteristics of the polarization separation film for each color are set in consideration of the range of the incident angle of each color light to the polarization separation film. In this case, polarization conversion with less loss adapted to the incident angle range of each color light is possible, and the polarization conversion efficiency is increased for light source light from a light source such as an LED that tends to have a relatively wide angle range of emitted light flux. be able to.

  In another aspect of the present invention, the polarization separation film for each color is formed of a dielectric multilayer film. In this case, highly efficient polarization conversion using the interference phenomenon is possible.

  The projector according to the present invention includes (a) the above-described illumination device, (b) a light modulation device for each color that modulates each color light that has passed through the polarization conversion device according to image information, and (c) each color light device. A light combining optical system for combining and emitting the image lights of the respective colors modulated by the light modulation device; and (d) a projection optical system for projecting the image light combined through the light combining optical system.

  Since the projector uses the illumination device as described above, the light modulation device for each color is illuminated with bright illumination light whose polarization conversion efficiency is individually improved for each color while reducing the size of the illumination device. And a high-luminance color image can be projected.

  FIG. 1 is a block diagram conceptually illustrating the structure of a projector according to an embodiment of the invention. The projector 10 includes an illumination device 20, a light modulation unit 30, a projection lens 40, and a control device 50. Here, the illumination device 20 includes a blue light illumination device 21, a green light illumination device 23, a red light illumination device 25, and a light source driving device 27. The light modulator 30 outputs drive signals to the three liquid crystal display panels 31, 33, and 35 that are light modulators, the cross dichroic prism 37 that is a light combining optical system, and the liquid crystal display panels 31, 33, and 35. And an element driving device 38.

  In the illumination device 20 described above, the blue light illumination device 21 includes a blue light source unit 21a, a polarization conversion device 61, and a rod integrator 21c. The blue light source unit 21a is a blue light source, and the rod integrator 21c is a blue uniformizing optical system.

  Among these, the blue light source unit 21a includes a plurality of LEDs 21f, which are light emitting elements called solid light sources or semiconductor light sources, mounted on the circuit board 21g in an appropriate two-dimensional array (for example, a matrix array). Each of the LEDs 21f has a condensing lens array 21b in which lens elements for beam shaping are individually arranged. Each LED 21f generates blue light included in the category of blue (B) among the three primary colors. The blue light extracted from the LED 21f, that is, the first light source light LB passes through the condenser lens array 21b and then enters the incident end of the polarization converter 61, that is, the incident port IP1. At this time, the blue light from each LED 21f is appropriately diverged by each lens element constituting the condenser lens array 21b, and is converted into an elliptical or rectangular cross-section beam gathered at a predetermined position. That is, the blue light from each LED 21f is collected as a whole at a rectangular incident port IP1 provided in the polarization converter 61, and is incident on the incident port IP1 without omission.

  The polarization converter 61 is disposed on the emission side of the blue light source unit 21a so as to face the light source unit 21a, and aligns the polarization direction of the incident first light source light LB. The polarization conversion device 61 is formed by bonding a right triangle prism and a parallelogram prism. The polarization separation film 61a sandwiched between the prisms and the blue light source unit 21a side of the parallelogram prism. A reflection film 61b is formed, and a wave plate 61d disposed on the rod integrator 21c side of these prisms. The polarization separation film 61a and the reflection film 61b are dielectric multilayer films formed by vapor deposition on the slopes of the respective prisms, and are disposed in a state inclined by 45 ° with respect to the system optical axis SA. The former polarization separation film 61a transmits a linearly polarized light component in a specific direction and reflects a linearly polarized light component in a direction orthogonal to the blue light, which is a random polarized light from the blue light source unit 21a. Two linearly polarized light components orthogonal to each other are efficiently separated. The latter reflection film 61b completely reflects one linearly polarized light component reflected by the polarization separation film 61a and bends the optical path. The reflective film 61b can be replaced with a metal film deposition mirror. The wave plate 61d is a phase element formed of a half-wave plate and has a component orthogonal to the linearly polarized light component reflected by the reflective film 61b and emitted from the parallelogram prism in the direction of the system optical axis SA. Convert to linearly polarized light component.

  The operation of the polarization conversion device 61 will be described more specifically. In the polarization conversion device 61, the polarization separation film 61a is one first linearly polarized light (in this case, of the first and second linearly polarized light included in the first light source light LB that is blue light from each LED 21f). P-polarized light is transmitted and the other second linearly polarized light (in this case, S-polarized light) is reflected. The reflected second linearly polarized light has its optical path bent by the latter reflecting mirror, and is emitted in the direction of emission of one first linearly polarized light, that is, the direction along the system optical axis SA. One of the first and second linearly polarized light thus emitted (in this case, the second linearly polarized light) is polarized and converted by the wave plate 61d provided on the light beam exit surface of the polarization conversion device 61. The polarization directions of all polarized light beams are aligned. In this case, a wave plate 61d for converting the second linearly polarized light into the first linearly polarized light is provided on the exit port OP2 side of the exit ports OP1 and OP2 constituting the light exit surface of the polarization conversion device 61. The polarization conversion device 61 can efficiently convert the first light source light LB incident on the incident port IP1 into only the first linearly polarized light (in this case, P-polarized light) and emit the light from both the emission ports OP1 and OP2. By using such a polarization conversion device 61, the light beam emitted from the blue light source unit 21a can be aligned with a polarized light beam in one direction. The utilization factor of the light source light to be used can be improved. The wavelength plate 61d can be provided not on the exit port OP2 side but on the adjacent exit port OP1 side.

  The rod integrator 21c is a homogenizing optical system made of a rectangular columnar transparent member extending along the system optical axis SA, has a rectangular cross section perpendicular to the system optical axis SA, and is an exit port OP1 provided in the polarization conversion device 61. , OP2 and an incident port IP3. The first illumination light that is incident from the incident port IP3, passes through the rod integrator 21c, and exits from the exit port OP3, which is the exit end thereof, passes through the first polarizing filter 26a that is disposed to face the exit port OP3. Of these, it enters the liquid crystal display panel 31 for blue light. As a result, the irradiated area (effective pixel area in which image information is formed) on the liquid crystal display panel 31 is uniformly illuminated with blue light.

  The pair of exit ports OP1 and OP2 of the polarization converter 61 are substantially the same as or smaller than the exit port OP3 of the rod integrator 21c, and the first light source light LB from the polarization converter 61 is converted into the rod. It can be coupled to the integrator 21c without leakage. Further, the cross-sectional shape and size of the rod integrator 21c can be changed along the system optical axis SA, and the shapes of the entrance port IP3 and the exit port OP3 do not have to be matched.

  The green light illumination device 23 includes a green light source unit 23a, a polarization conversion device 63, and a rod integrator 23c. Among these, the green light source unit 23a has the same structure as the blue light source unit 21a, but each LED 23f on the circuit board 23g emits green light included in the green (G) category among the three primary colors. Each of the second light source lights LG generated and made of green light is incident on the incident port IP1 of the polarization conversion device 63 without any leakage through the condenser lens array 23b. The polarization conversion device 63 has the same structure as the polarization conversion device 61, and includes a polarization separation film 63a, a reflection film 63b, and a wavelength plate 63d. The second illumination light LG that has passed through the polarization conversion device 63 is efficiently converted into single-component linearly polarized light by polarization separation, optical path bending, and polarization switching, similar to the polarization conversion device 61, and its emission ports OP1, The light is incident on the incident port IP3 of the rod integrator 23c arranged opposite to OP2 without leakage. The second illumination light LG that has passed through the rod integrator 23c is homogenized without loss by wavefront division and superposition, and the green color of the light modulation unit 30 passes through the first polarizing filter 26b that is disposed opposite to the emission port OP3. The light enters the liquid crystal display panel 33 for light. Thereby, the irradiated area on the liquid crystal display panel 33 is illuminated uniformly with green light.

  The red light illumination device 25 includes a red light source unit 25a, a polarization conversion device 65, and a rod integrator 25c. Among these, the red light source unit 25a has the same structure as the blue light source unit 21a, but each LED 25f on the circuit board 25g emits red light included in the red (R) category among the three primary colors. The third light source light LR generated by the red light is incident on the incident port IP1 of the polarization converter 65 without omission through the condenser lens array 25b. The polarization conversion device 65 has the same structure as the polarization conversion device 61, and includes a polarization separation film 65a, a reflection film 65b, and a wavelength plate 65d. The third illumination light LR that has passed through the polarization conversion device 65 is efficiently converted into single-component linearly polarized light by polarization separation, optical path bending, and polarization switching, as in the case of the polarization conversion device 61, and its emission port. The light is incident on the incident port IP3 of the rod integrator 25c arranged opposite to OP1 and OP2 without leakage. The third illumination light LR that has passed through the rod integrator 25c is uniformized without loss by wavefront division and superposition, and the red color of the light modulation unit 30 passes through the first polarizing filter 26c that is disposed opposite to the emission port OP3. The light enters the liquid crystal display panel 35 for light. Thereby, the irradiated area on the liquid crystal display panel 35 is uniformly illuminated by the red light.

  Each of the liquid crystal display panels 31, 33, and 35 is a light transmission type light modulation device, and by switching the polarization direction of illumination light in units of pixels in accordance with an image signal input from the outside, each liquid crystal display panel 31, Illumination light from each of the color light illumination devices 21, 23, 25 incident on 33, 35 is two-dimensionally modulated. On the incident side of each liquid crystal display panel 31, 33, 35, first polarizing filters 26 a, 26 b, 26 c are arranged facing the incident surface, and each liquid crystal display panel 31, 33, 35 has a degree of polarization. Illumination can be achieved by an enhanced polarization component. In addition, second polarizing filters 36a, 36b, and 36c are arranged on the exit side of the liquid crystal display panels 31, 33, and 35 so as to face the exit surface, and pass through the liquid crystal display panels 31, 33, and 35. Only the polarization component in the direction orthogonal to the specific direction can be read out. Here, the first polarizing filter 26a, the liquid crystal display panel 31, and the second polarizing filter 36a constitute a liquid crystal light valve for blue, and the first polarizing filter 26b, the liquid crystal display panel 33, and the second polarizing filter 36b The first polarizing filter 26c, the liquid crystal display panel 35, and the second polarizing filter 36c constitute a red liquid crystal light valve. That is, the illumination light from the color light illuminating devices 21, 23, and 25 incident on the liquid crystal display panels 31, 33, and 35 is intensity-modulated two-dimensionally by the liquid crystal display panels 31, 33, and 35, respectively. The image lights of the respective colors that have passed through the liquid crystal display panels 31, 33, and 35 are combined by the cross dichroic prism 37 and emitted from one side surface thereof. The image of the combined light emitted from the cross dichroic prism 37 is incident on the projection lens 40 which is a projection optical system, and is projected on a screen (not shown) at an appropriate magnification. That is, the projector 10 projects a color image obtained by combining the images of the respective colors (blue, green, and red) formed on the liquid crystal display panels 31, 33, and 35 on the screen as a moving image or a still image.

  2 and 3 are graphs for explaining the transmission characteristics of the polarization separation film 61 a provided in the polarization conversion device 61. In FIG. 2, the horizontal axis indicates the wavelength, and the vertical axis indicates the transmittance of P-polarized light. In FIG. 3, the horizontal axis indicates the wavelength, and the vertical axis indicates the transmittance of S-polarized light. In both graphs, the transmittance is plotted at an incident angle (specifically, 36.7 °, 42 °, 45 °, 47.7 °, 53 °) around ± 20 ° centered on 45 °. . As is apparent from the graph, the polarization separation film 61a can efficiently transmit the P-polarized light and can reflect the S-polarized light efficiently at the wavelength in the blue region (450 nm ± 20 to 30 nm). .

  The process of designing the polarization separation characteristics of the polarization separation film 61a as described above will be described. The first light source light LB incident on the polarization conversion device 61 from the blue light source unit 21a is distributed in a range of about ± 20 ° around the system optical axis SA. That is, the incident angle of the first light source light LB incident on the polarization separation film 61a is distributed in a range of about ± 20 ° with 45 ° being the center. In addition, when the LED 21f of the blue light source unit 21a is replaced with a lamp light source having a high luminance and a light emitting point, the incident angle distribution is about ± 10 °, but it is not easy to prepare a light source of each color. Such problems and the increase in the size of the light source are problems. On the other hand, when the LED 21f is used for the blue light source unit 21a, the distribution of the incident angles spreads to about ± 20 °. However, the blue light source can be prepared individually and easily, and the light source can be miniaturized. As shown in FIGS. 2 and 3, with respect to the increase in the incident angle, the design value of the multilayer film of the polarization separation film 61a is adapted to the wavelength in the blue region, so that the polarization separation characteristic dedicated to blue is given. And the tolerance for the distribution of incident angles can be increased. Note that the polarization separation characteristic of the polarization separation film 61a can be optimized in consideration of the distribution range of incident angles in the specific design.

  4 and 5 are graphs for explaining the transmission characteristics of the polarization separation film 63 a provided in the polarization conversion device 63. In FIG. 4, the vertical axis represents the transmittance of P-polarized light, and in FIG. 5, the vertical axis represents the transmittance of S-polarized light. In both graphs, the transmittance is plotted at an incident angle (specifically, 36.7 °, 42 °, 45 °, 47.7 °, 53 °) around ± 20 ° centered on 45 °. . As is apparent from the graph, the polarization separation film 63a can efficiently transmit the P-polarized light and can reflect the S-polarized light efficiently at the wavelength in the green region (530 nm ± 20 to 30 nm). .

  In the case of the green light source unit 23a that constitutes the polarization conversion device 63, the LED 23f is used, and the distribution of the incident angle spreads to about ± 20 °. By being adapted to the above, it is possible to have a polarization separation characteristic exclusively for green, and to increase the tolerance for the distribution of incident angles. Note that the polarization separation characteristics of the polarization separation film 63a can be optimized as appropriate in consideration of the distribution range of the incident angles in the specific design.

  6 and 7 are graphs for explaining the transmission characteristics of the polarization separation film 65 a provided in the polarization conversion device 65. In FIG. 6, the vertical axis represents the transmittance of P-polarized light, and in FIG. 7, the vertical axis represents the transmittance of S-polarized light. In both graphs, the transmittance is plotted at an incident angle (specifically, 36.7 °, 42 °, 45 °, 47.7 °, 53 °) around ± 20 ° centered on 45 °. . As is apparent from the graph, the polarization separation film 65a can efficiently transmit the P-polarized light and can efficiently reflect the S-polarized light at the red wavelength (630 nm ± 20 to 30 nm). .

  In the case of the light source unit 25a for red light constituting the polarization conversion device 65, the LED 25f is used, and the distribution of incident angles spreads to about ± 20 °, but the design value of the multilayer film of the polarization separation film 65a is set to the wavelength in the red region. By being adapted to the above, it is possible to have a polarization separation characteristic exclusively for red, and to increase the tolerance for the distribution of incident angles. Note that the polarization separation characteristics of the polarization separation film 65a can be optimized as appropriate in consideration of the distribution range of incident angles in specific design.

  FIG. 8A conceptually shows the transmission characteristics of the polarization separation films 61a, 63a, and 65a shown in FIGS. 2, 4, and 6 collectively, and the incident angles are 45 ° -10 ° and 45 °. In the case of 45 ° + 10 °, the light source lights LB, LG, LR that can be extracted by the transmission component are shown. FIG. 8B conceptually shows the transmission characteristics of the polarization splitting film 65a shown in FIGS. 3, 5, and 7 collectively, and the incident angles are 45 ° -10 °, 45 °, 45 In the case of + 10 °, the light source lights LB, LG, and LR that can be extracted by the reflection component are shown. It can be seen that the illumination light can be efficiently extracted as a whole by setting the polarization separation characteristics of the polarization separation films 61a, 63a and 65a for each color.

  FIG. 9 shows a comparative example in which all the polarization separation films 61a, 63a, and 65a have the same polarization separation characteristic. FIG. 9A corresponds to FIG. 8A, and FIG. 9B corresponds to FIG. 8B. When the polarization separation characteristics of the polarization separation films 61a, 63a, and 65a are not set for each color, it is difficult to design the polarization separation characteristics to a target value in a wide wavelength range, so that the use efficiency of illumination light is reduced. I can see that it gets worse.

  Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments. For example, the illuminating device 20 is not limited to the blue light illuminating device 21, the green light illuminating device 23, and the red light illuminating device 25, but can be a color light illuminating device having two or more colors of other wavelengths. In the above, the use efficiency of light can be increased by using the polarization conversion device adapted to the wavelength corresponding to the polarization conversion devices 61, 63, 65 described above.

  In the above embodiment, the polarization separation films 61a, 63a, 65a are incorporated in the polarization conversion devices 61, 63, 65. However, instead of the polarization separation films 61a, 63a, 65a, organic polarization films or wire grid polarizers are used. Etc. can also be used.

1 is a block diagram conceptually illustrating an optical system of a projector according to an embodiment. It is a graph explaining the P polarization | polarized-light transmission characteristic of the polarization separation film for blue. It is a graph explaining the S polarization | polarized-light transmission characteristic of the polarization separation film for blue. It is a graph explaining the P polarization | polarized-light transmission characteristic of the polarization separation film for green. It is a graph explaining the S polarization | polarized-light transmission characteristic of the polarization separation film for green. It is a graph explaining the P polarization transmission characteristic of the polarization separation film for red. It is a graph explaining the S polarization | polarized-light transmission characteristic of the polarization separation film for red. (A), (b) is the conceptual diagram which put together the permeation | transmission characteristic of the polarization separation film of each color. (A), (b) is the conceptual diagram which put together the transmission characteristic of the polarization separation film of a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 ... Illuminating device, 20 ... Illuminating device, 21a ... Light source unit for blue light, 21b ... Condensing lens array, 21c ... Rod integrator, 23 ... Green light illuminating device, 23a ... Light source unit for green light, 23b ... Condensing lens Array, 23c ... Rod integrator, 25b ... Condensing lens array, 26a ... First polarizing filter, 27 ... Light source driving device, 31, 33, 35 ... Liquid crystal display panel, 37 ... Cross dichroic prism, 38 ... Element driving device, 40 ... Projection lens 61, 63, 65 ... Polarization conversion device, 61a, 63a, 65a ... Polarization separation film, 61b ... Reflection film, 61c ... Wave plate, LB, LG, LR ... Light source light, 21f, 23f, 25f ... LED SA ... System optical axis

Claims (5)

A light source for each color that generates each color light as a light source light;
A first linearly polarized light and a second straight line having polarization separation characteristics adapted to the wavelengths of the respective color lights emitted from the light sources for the respective colors and having the polarization directions orthogonal to each other, which are random polarized lights. Polarization conversion for each color, including a polarization separation film for each color that is separated into polarized light, and a phase element for each color that aligns the polarization directions of the first linearly polarized light and the second linearly polarized light for each color Equipment,
A lighting device comprising:   The illumination device according to claim 1, further comprising a uniformizing optical system that is arranged in a front stage and / or a rear stage of the polarization conversion device and divides and superimposes the respective color lights into partial light beams.   3. The polarization separation characteristic of the polarization separation film for each color is set in consideration of an incident angle range of each color light to the polarization separation film. The lighting device according to one item.   4. The illumination device according to claim 1, wherein the polarization separation film for each color is formed of a dielectric multilayer film. 5. The lighting device according to any one of claims 1 to 4,
A light modulation device for each color that modulates each color light that has passed through the polarization conversion device according to image information;
A light combining optical system for combining and emitting image light of each color modulated by the light modulation device for each color;
A projection optical system for projecting the image light combined through the light combining optical system;
A projector comprising:

Images