JP2005266115A - Projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projector with which desired white balance is attained without significantly attenuating G light with an ND filter, etc. while reducing attenuation of R light and B light as much as possible. <P>SOLUTION: The projector is constituted so that illumination light in G color to be led to a third optical path OP3 is dimmed to some extent via relay lenses LL1, LL2, etc. in a color separation optical system 23. In addition, in a cross dichroic prism 27, image light in R color which goes straight and passes the cross dichroic prism is somewhat dimmed by penetrating both dielectric multi-layer films 27a, 27b. Thus, in the color separation optical system 23, the strongest illumination light of G color is automatically dimmed and in the cross dichroic prism 27, the second strongest illumination light of R color is automatically dimmed and luminance of the image light in each of colors RGB becomes a balanced state as a whole. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a projector that projects a color image using a liquid crystal display panel or other light modulation device.

  In a conventional projector, in general, white light from a white light source is divided by a pair of dichroic mirrors to obtain illumination light of each color of RGB. These RGB illumination lights are used to illuminate each color liquid crystal display panel, and the modulated light that has passed through each color liquid crystal display panel is synthesized by a light synthesis member called a cross dichroic prism and projected as a color image (Patent Document) 1).

  In such a projector, the R light is guided to an optical path reflected by one dielectric multilayer film in the cross dichroic prism, and the B light is an optical path reflected by the other dielectric multilayer film in the cross dichroic prism. The G light is guided to an optical path that passes through both dielectric multilayer films in the cross dichroic prism. At this time, the optical path of the R light reaching the liquid crystal display panel is longer than the optical path of the B light and the G light reaching the liquid crystal display panel due to the shape limitation of the cross dichroic prism, so that the optical path difference is compensated. A relay lens is inserted. At this time, the wavelength characteristic of the high-pressure mercury lamp has a strong peak in G color, and in order to prevent the white image from becoming greenish due to this, it is not suitable for applications such as home theater and projection TV. Therefore, it is necessary to achieve a desired color tone by disposing an ND filter on the G color optical path or increasing the modulation degree of the G color liquid crystal display panel.

In addition, in order to suppress the influence of the light amount loss in the relay lens or the like, the B light instead of the G light is configured to travel straight through the cross dichroic prism, and the G light instead of the B light passes through a long optical path provided with the relay lens or the like. In some cases, the structure may be guided (see Patent Document 2).
JP 2003-287804 A Japanese Patent No. 3254680

  However, in the former projector, the weakest R light may be attenuated by a relay lens or the like, so that the target white balance is not necessarily achieved only by attenuation of the G color.

  In the latter projector, the attenuation of the R light can be reduced, but the B light that is weaker than the normal G light may be attenuated by going straight through and passing through the cross dichroic prism.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a projector that can achieve a desired white balance without reducing attenuation of R light and B light as much as possible and without greatly reducing G light with an ND filter or the like. And

  In order to solve the above problems, a projector of the present invention includes (a) first to third color illumination light, the third color light amount is larger than the first and second color light amounts, and the second A light source that emits light source light such that the light amount of the color is greater than the light amount of the first color; and (b) among the light source light emitted from the light source, The second color illumination light is guided to the first and second optical paths, respectively, and the third color light source light is passed as the third color illumination light through the relay lens system having an optical path longer than the first and second optical paths. A light splitting means for guiding to the third optical path; and (c) illuminating with the first to third color illumination lights emitted from the light splitting means, respectively, and modulating the first to third color illumination lights respectively. A first to a third light modulation device for forming modulated light of the first to third colors; A light modulation device having a built-in sudichroic mirror, reflecting the first and third color modulated light with the pair of cross dichroic mirrors, and transmitting the second color modulated light with the pair of cross dichroic mirrors And (e) a projection optical system that forms a projection image of the image light synthesized by passing through the light synthesizing member.

  In the projector, the light splitting means guides the third color illumination light having a larger light quantity than the first and second color illumination lights to the third optical path that passes through the relay lens system longer than the first and second optical paths. The relative intensity of the third color can be naturally reduced by utilizing the fact that the illumination light of the third color is attenuated by the relay lens system or the like. Further, since the light combining member reflects the first and third color modulated light and transmits the second color modulated light by the pair of cross dichroic mirrors, the second color modulated light is transmitted by the pair of cross dichroic mirrors. Utilizing the attenuation over others, the relative intensity of the second color can be naturally reduced to approach the degree of the first or third color. Therefore, it is possible to balance the relative intensities of the modulated light of the first to third colors without particularly providing a light reducing optical system such as a filter, and it is possible to easily achieve a desired white balance for the projected image. it can.

  In a specific aspect of the present invention, in the projector, the light source is a white light source, the first color illumination light is B light, the second color illumination light is R light, and the third color illumination light is G light. In general, a general-purpose lamp light source for a projector having sufficient luminance often has the weakest B light and the strongest G light. Therefore, the color balance of such a lamp light source is adjusted by a light dividing means or a light combining member. It can be corrected automatically.

  In another specific embodiment of the present invention, the light source is either a mercury lamp or a metal halide lamp. In this case, the color balance of the mercury lamp and the metal halide lamp can be corrected as appropriate.

  Moreover, in another specific aspect of the present invention, the color temperature of the projected image is not less than 4000K and not more than 12000K. In this case, it is possible to adapt the white balance of the projected image to uses such as a home theater and a projection TV that place importance on the hue without wasting illumination light.

  In another specific embodiment of the present invention, the photosynthetic member is a cross dichroic prism. In this case, the photosynthetic member becomes an integral member, and stable and good photosynthesis is possible.

  FIG. 1 is a diagram illustrating an optical system of a projector according to an embodiment of the invention. The projector 10 is emitted from a light source device 21 that generates light source light, a color splitting optical system 23 that is a light splitting unit that splits the light source light from the light source device 21 into three colors of RGB, and the color splitting optical system 23. The light modulation unit 25 illuminated by the illumination light of each color, the cross dichroic prism 27 that is a light synthesis member for synthesizing the modulated light of each color from the light modulation unit 25, and the image light that has passed through the cross dichroic prism 27 are screened. And a projection lens 29 which is a projection optical system for projecting to (not shown).

  Here, the light source device 21 includes a light source lamp 21a, a pair of fly-eye optical systems 21d and 21e, a polarization conversion member 21g, and a superimposing lens 21i. Here, the light source lamp 21a is a white light source composed of a high-pressure mercury lamp, for example, and includes a concave mirror for collimating the light source light. Such a high-pressure mercury lamp generates light source light composed of RGB colors, of which the G color has the strongest peak and the amount of G light is the largest. Further, the light amount of the R color is somewhat larger than the light amount of the B color. That is, the light source light tends to be green rather than completely white. The pair of fly-eye optical systems 21d and 21e is composed of a plurality of element lenses arranged in a matrix, and these element lenses divide the light source light from the light source lamp 21a and individually collect and diverge the light. The polarization conversion member 21g converts the light source light emitted from the fly-eye optical system 21e into, for example, only the S-polarized component perpendicular to the paper surface of FIG. The superimposing lens 21i appropriately converges the illumination light that has passed through the polarization conversion member 21g as a whole, and enables superimposing illumination on the light modulation devices of the respective colors provided in the light modulation unit 25. That is, the illumination light that has passed through the fly-eye optical systems 21d and 21e and the superimposing lens 21i passes through the color splitting optical system 23, which will be described in detail below. The light valves 25a to 25c are uniformly superimposed and illuminated.

  The color division optical system 23 includes first and second dichroic mirrors 23a and 23b, three field lenses 23f, 23g, and 23h, and reflection mirrors 23m, 23n, and 23o, and constitutes an illumination device together with the light source device 21. . The first dichroic mirror 23a reflects B light and transmits R light and G light among the three colors of RGB. The second dichroic mirror 23b reflects R light and transmits G light out of the two colors of incident RG. In the color splitting optical system 23, white light source light from the light source device 21 is incident on the first dichroic mirror 23a. The B light reflected by the first dichroic mirror 23a is guided to the first optical path OP1 with, for example, S-polarized light, and enters the field lens 23f for adjusting the incident angle via the reflecting mirror 23m. Further, the R light transmitted through the first dichroic mirror 23a and reflected by the second dichroic mirror 23b is guided to the second optical path OP2 while being, for example, S-polarized, and enters the field lens 23g. Further, the G light that has passed through the second dichroic mirror 23b is guided to the third optical path OP3 as S-polarized light, for example. Is incident on a field lens 23h for adjusting the angle. Here, relay lenses LL1 and LL2 which are relay lens systems are incorporated in the third optical path OP3, and the aberration and magnification of the illumination light in the third optical path OP3 set longer than the first and second optical paths OP1 and OP2. Are corrected, however, such relay lenses LL1 and LL2 and reflection mirrors 23n and 23o cause light attenuation. Such dimming is unavoidable in the color-splitting optical system 23 having the arrangement shown in FIG. 1, but by using this in reverse, the color balance of the image light can be adjusted.

  The light modulation unit 25 includes three liquid crystal light valves 25a, 25b, and 25c into which three colors of illumination light respectively enter, and three sets of polarizing filters 25e that are disposed so as to sandwich the liquid crystal light valves 25a, 25b, and 25c. 25f and 25g. The B light guided to the first optical path OP1 enters the irradiated surface of the liquid crystal light valve 25a via the field lens 23f. The R light guided to the second optical path OP2 enters the irradiated surface of the liquid crystal light valve 25b via the field lens 23g. The G light guided to the third optical path OP3 enters the irradiated surface of the liquid crystal light valve 25c through the field lens 23h. Each of the liquid crystal light valves 25a to 25c is a non-light emitting type light modulation device for modulating the spatial intensity distribution of the incident illumination light, and the three color lights respectively incident on the liquid crystal light valves 25a to 25c are The polarization state is adjusted in units of pixels in accordance with drive signals or image signals input as electric signals to the liquid crystal light valves 25a to 25c. At that time, the polarization filters 25e to 25g adjust the polarization direction of the illumination light incident on the liquid crystal light valves 25a to 25c, and modulate the predetermined polarization direction from the light emitted from the liquid crystal light valves 25a to 25c. Light is extracted.

  The cross dichroic prism 27 is a light combining member, and incorporates a dielectric multilayer film 27a for reflecting R light and a dielectric multilayer film 27b for reflecting B light in an orthogonal state. One dielectric multilayer film 27a is a dichroic mirror that reflects image light on a shorter wavelength side than the boundary wavelength between B color and G color (for example, 500 nm), and the other dielectric multilayer film 27b is composed of B color and G color. This is a dichroic mirror that reflects image light in a wavelength range from a boundary wavelength of color (for example, 500 nm) to a boundary wavelength of G and R (for example, 580 to 585 nm). Thus, the cross dichroic prism 27 incorporates a pair of dielectric multilayer films 27a and 27b in a crossed state as a cross dichroic mirror. The cross dichroic prism 27 reflects the R light from the liquid crystal light valve 25a by the dielectric multilayer film 27a and emits the G light from the liquid crystal light valve 25b via the dielectric multilayer films 27a and 27b. The B light from the liquid crystal light valve 25c is reflected by the dielectric multilayer film 27b and emitted to the left in the traveling direction. As described above, the image lights incident from the three side surfaces of the cross dichroic prism 27 are combined and emitted from the remaining side surfaces. The image light synthesized and emitted by the cross dichroic prism 27 is projected as a color image on a screen (not shown) at an appropriate magnification through a projection lens 29. In addition, regarding the straight-traveling optical path that transmits the both dielectric multilayer films 27a and 27b in the cross dichroic prism 27, the transmission loss increases compared to the optical path reflected by either of the dielectric multilayer films 27a and 27b. Tend. Such dimming is unavoidable, but color balance can be adjusted by using this dimming.

  Hereinafter, the operation of the projector 10 according to the present embodiment will be described. The light source light from the light source device 21 is color-divided by the first and second dichroic mirrors 23a and 23b provided in the color-dividing optical system 23, and is incident on the corresponding liquid crystal light valves 25a to 25c as illumination light. Each of the liquid crystal light valves 25a to 25c is modulated by an image signal from the outside and has a two-dimensional refractive index distribution, and modulates illumination light in a two-dimensional space in units of pixels. As described above, the illumination light, that is, the image light modulated by the liquid crystal light valves 25 a to 25 c is combined by the cross dichroic prism 27 and then enters the projection lens 29. The image light incident on the projection lens 29 is projected on a screen (not shown). At this time, in the color division optical system 23, the G-color illumination light guided to the third optical path OP3 is dimmed to some extent by passing through the relay lenses LL1, LL2, etc., so that the other light path, for example, the first optical path OP1. The amount of illumination light is the same as that of the B-color light to be guided. Further, in the cross dichroic prism 27, the R-color image light that travels straight through and passes through the dielectric multilayer films 27a and 27b is somewhat attenuated, so that, for example, the dielectric multilayer via the first optical path OP1. The luminance is about the same as the B-color image light reflected by the film 27a. As a result, the luminance of the RGB color image light emitted from the cross dichroic prism 27 is balanced as a whole. At this time, since it is not necessary to actively provide an ND filter or the like in the illumination light path or image light path of any color, the brightness of the image can be increased. Further, since it is not necessary to adjust the transmittance of each of the liquid crystal light valves 25a to 25c to reduce the opening, there is no deterioration in contrast.

  FIG. 2 is a graph for explaining the relationship between the color temperature of the image light (after passing through the screen) projected by the projector 10 of FIG. 1 and the light use efficiency. In the graph, the horizontal axis indicates color temperature (K), and the vertical axis indicates light utilization efficiency (%). In order to adjust the color temperature, the utilization efficiency of G light was adjusted with respect to R and B light. In the graph, the mark “×” corresponds to the present embodiment, and the G light enters the cross dichroic prism 27 via the relay lenses LL1 and LL2 and is combined by reflection, and the R light passes through the cross dichroic prism 27. Synthesized. The mark “▲” corresponds to the first comparative example. G light enters the cross dichroic prism 27 via the relay lenses LL1 and LL2, is combined by reflection, and B light passes through the cross dichroic prism 27. Are synthesized. Further, the mark “■” corresponds to the second comparative example. R light enters the cross dichroic prism 27 via the relay lenses LL1 and LL2, is combined by reflection, and G light passes through the cross dichroic prism 27. Are synthesized. The mark “♦” corresponds to the third comparative example. B light enters the cross dichroic prism 27 via the relay lenses LL1 and LL2 and is combined by reflection, and G light passes through the cross dichroic prism 27. Are synthesized.

  As is apparent from the above graph, it can be seen that in the range of the color temperature of the projected image from 4000 to 12000 (K), the light utilization efficiency of the example indicated by the x mark is the highest compared to the others. That is, the G light is bent by the cross dichroic prism 27 along a long path via the relay lenses LL1 and LL2, the R light is transmitted through the cross dichroic prism 27 along a relatively short path, and the B light is crossed along a relatively short path. It can be seen that the optical path configuration of the embodiment bent at 27 has the highest use efficiency of the light source light.

  As described above, the present invention has been described according to the embodiment, but the present invention is not limited to the above embodiment. For example, the light source lamp 21 a of the light source device 21 is not limited to a high-pressure mercury lamp, and a metal halide lamp or the like can be used. In this case, the G-color illumination light is automatically dimmed in the color division optical system 23. Then, in the cross dichroic prism 27, the R illumination light is automatically reduced, and the luminance of the image light of each color RGB is balanced as a whole.

It is a figure explaining the projector of an embodiment. It is a graph explaining the relationship between the color temperature of image light and light utilization efficiency.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Projector, 21 ... Light source device, 21a ... Light source lamp, 21d, 21e ... Fly eye optical system, 21g ... Polarization conversion member, 21i ... Superimposing lens, 23 ... Color division optical system, 23a, 23b ... Dichroic mirror, 25 ... Light modulator, 25a, 25b, 25c ... Liquid crystal light valve, 25e, 25f, 25g ... Polarizing filter, 27 ... Cross dichroic prism, 27a, 27b ... Dielectric multilayer film, 29 ... Projection lens, OP1 ... First optical path, OP2 ... second optical path, OP3 ... third optical path

Claims (5)

A light source that includes illumination light of the first to third colors, the light amount of the third color is larger than the light amounts of the first and second colors, and the light amount of the second color is larger than the light amount of the first color A light source that emits light;
Of the light source light emitted from the light source, the first and second color light source lights are led to the first and second optical paths as the first and second color illumination lights, respectively, and the third color light source light, A light splitting means for guiding the third color illumination light to the third optical path having a longer optical path than the first and second optical paths and passing through the relay lens system;
The first to third color illumination lights emitted from the light splitting means are respectively illuminated, and the first to third color illumination lights are modulated to form first to third color modulated lights. First to third light modulation devices;
By incorporating a pair of orthogonal cross dichroic mirrors, reflecting the first and third color modulated light with the pair of cross dichroic mirrors, and transmitting the second color modulated light with the pair of cross dichroic mirrors A light combining member that combines the modulated light of the first to third colors that has passed through the light modulation device;
A projector comprising: a projection optical system that forms a projection image of image light synthesized by passing through the light synthesis member.   The light source is a white light source, the first color illumination light is B light, the second color illumination light is R light, and the third color illumination light is G light. The projector according to claim 1.   The projector according to claim 1, wherein the light source is one of a mercury lamp and a metal halide lamp.   The projector according to any one of claims 1 to 3, wherein a color temperature of the projected image is not less than 4000K and not more than 12000K. The projector according to claim 1, wherein the light combining member is a cross dichroic prism.

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