JP3651484B2 - Illumination device and projection device - Google Patents

Description

  The present invention relates to an illumination device for illuminating a spatial light modulation device and other display devices, and a projection device that projects an image using the spatial light modulation device and the illumination device.

  It has been proposed to illuminate a light valve such as an LCD using a light source device incorporating a plurality of types of LED elements having different emission wavelengths (see Patent Document 1). In this light source device, the luminance of a specific color is enhanced by combining light beams from a pair of different types of LED elements having slightly different emission wavelengths with a dichroic mirror.

JP 2001-42431 A

  However, in the light source device, due to the characteristics of the dichroic mirror, the center wavelength of the pair of light beams emitted from the pair of different types of LED elements cannot be made closer to a predetermined value or more. That is, since the dichroic mirror for color synthesis usually has different cutoff frequencies for P-polarized light and S-polarized light, a pair of dissimilar LED elements are arranged on both outer sides of a wavelength region sandwiched between a pair of cutoff frequencies corresponding to both polarized lights. It is necessary to set the emission center wavelength. Such a wavelength range may reach about 50 nm, and the center wavelength difference between a pair of light beams to be combined becomes large, and the color purity of a specific color obtained after combining decreases.

  Therefore, an object of the present invention is to provide an illumination device or the like that can improve luminance without lowering color purity.

  In order to solve the above-described problems, an illumination device according to the present invention includes a light source device having first and second light sources that generate first and second illumination lights having different peak wavelengths, and first and second illumination lights. A combining unit that combines and emits the first and second illumination lights when incident, and a polarization conversion unit that converts the second illumination light into linearly polarized light in a predetermined direction and enters the combining unit. Prepare.

  In the illuminating device, since the polarization conversion means converts the second illumination light into linearly polarized light in a predetermined direction and makes it incident on the multiplexing means, the multiplexing characteristic of the multiplexing means is polarization dependent with respect to the wavelength of the second illumination light. Even if it has a property, the polarized light according to the characteristic can be entered into the multiplexing means. Thereby, the 1st and 2nd illumination light can be combined efficiently, and the brightness | luminance improvement of the illumination light finally obtained by multiplexing can be aimed at. Here, “polarization dependence” means that characteristics such as multiplexing efficiency by the multiplexing means differ depending on the polarization state of the incident light such as the polarization direction.

  In a specific aspect of the illumination device, the multiplexing unit is an optical multiplexing / branching element that utilizes transmission and reflection of light, and the peak wavelength of the second illumination light is transmitted or reflected by the optical multiplexing / branching element with respect to linearly polarized light in a predetermined direction. The first edge wavelength and the second edge wavelength transmitted or reflected by the optical coupling / branching element with respect to linearly polarized light in the direction orthogonal to the predetermined direction are set in a difference generation region. In this case, even if there is a difference generation region where the difference between the edge wavelengths for both the S and P polarizations is not negligible in the transmission / reflection characteristics of the optical combining / branching element, the luminance can be improved by combining the compensation. .

  In another specific aspect of the illumination device, the center wavelength of the first illumination light is set in the vicinity of the difference generation region outside the difference generation region. In this case, since the wavelength difference between the first illumination light and the second illumination light can be reduced, illumination light having substantially the same color and high luminance can be generated.

  In still another specific aspect of the illumination device, the multiplexing unit is a dichroic mirror. In this case, efficient multiplexing is possible with an optical element having a simple structure.

  In still another specific aspect of the illumination device, the first and second light sources are solid light sources. Here, the “solid light source” is a concept including an LED, an EL element, an LD, and the like. In this case, the luminance of the specific wavelength light can be increased while the light source control is easy.

Further, in still another specific aspect of the illumination device, the polarization conversion means includes a rod integrator on which light emitted from the second light source is incident, a reflective polarizing plate disposed at an emission end of the rod integrator, Reflecting means for returning the return light from the reflective polarizing plate that has passed through the rod integrator to the incident end of the rod integrator.
In this case, since the return light reflected by the reflective polarizing plate is also reused by the reflecting means or the like, the second illumination light that is linearly polarized light in a predetermined direction can be efficiently extracted without waste.

  In still another specific aspect of the illumination device, the polarization conversion means is disposed on the exit side of the pair of polarization beam splitters on which the light emitted from the second light source sequentially enters and the subsequent polarization beam splitter. A wave plate. In this case, the second illumination light having a high degree of polarization can be efficiently extracted without waste.

  In still another specific aspect of the illumination device, the first and second illumination lights belong to any one of the three primary colors. In this case, the luminance of any of the three primary colors can be easily increased without degrading the pure chromaticity.

The projection device according to the present invention includes the above-described illumination device, a spatial light modulation device illuminated by the illumination device, and a projection lens that projects an image of the spatial light modulation device.
Here, the “spatial light modulation device” is an optical device typified by, for example, a liquid crystal light valve, and has a concept including a digital mirror device and the like.

  In the projection device, since the above-described illumination device is incorporated, the first and second illumination lights can be efficiently combined, and the luminance of the illumination light finally obtained by the combination can be improved. An image having high brightness can be projected.

  In addition, another projection device according to the present invention provides a third and a fourth light source that respectively generate a third and a fourth illumination light belonging to two other colors different from the first and second illumination lights among the three primary colors. The first and second illumination lights and the third illumination light when the above-described illumination device, the first and second illumination lights, the third illumination light, and the fourth illumination light respectively enter , Three spatial light modulators that individually modulate the fourth illumination light, a light combining member that combines and emits the modulated light from each of the spatial light modulators, and three spatial lights combined through the light combining member A projection lens for projecting an image of the modulation device.

  Since the above-described illumination device is incorporated in the projection device, the first and second illumination lights can be efficiently combined, and the luminance of the three primary colors of illumination light finally obtained by the combination is improved. It is possible to project a color image having high luminance using three spatial light modulators.

  In a specific aspect of the projection apparatus, the spatial light modulation device is a liquid crystal light valve. In this case, a high-definition and high-definition image can be projected by a small device.

[First Embodiment]
FIG. 1 is a block diagram conceptually illustrating the structure of the projection apparatus according to the first embodiment. The projection device, that is, the projector 10 includes an illumination device 20, a light modulation device 30, and a projection lens 40. Here, the illumination device 20 includes a G light illumination device 21, a B light illumination device 23, and an R light illumination device 25. The light modulation device 30 includes three liquid crystal light valves 31, 33, and 35 that are spatial light modulation devices, and a cross dichroic prism 37 that is a light combining member.

  In the illuminating device 20, the G light illuminating device 21 includes a first and second light sources 21a and 21b that generate a pair of illuminating lights whose center wavelengths are extremely approximate, and a concave surface that condenses the illuminating light from these light sources 21a and 21b. A reflecting mirror 21d, a dichroic mirror DM that is a multiplexing unit that combines illumination light from both light sources 21a and 21b, and a polarization conversion unit that converts illumination light from the second light source 21b into predetermined polarized light. A polarization conversion unit PC. Here, both the light sources 21a and 21b and the pair of concave reflecting mirrors 21d constitute a light source device.

The first and second light sources 21a and 21b are both LEDs that are also called solid-state light sources, and generate G1 light and G2 light that are included in the green (G) category of the three primary colors but have slightly different center wavelengths. The first illumination light IG1 from the first light source 21a is collected without waste by the concave reflecting mirror 21d, enters the dichroic mirror DM, is reflected by the dichroic mirror DM, and enters the rod lens 21f.
On the other hand, the second illumination light IG2 from the second light source 21b is recovered without waste by the concave reflecting mirror 21d and enters the polarization conversion unit PC. The second illumination light IG2 converted into only P-polarized light by the polarization converter PC is incident on the dichroic mirror DM, is transmitted therethrough, and is incident on the rod lens 21f after being combined with the first illumination light IG1. To do. The first and second illumination lights IG1 and IG2 incident on the rod lens 21f are made uniform by the rod lens 21f and incident on the liquid crystal light valve 31 for G light constituting the light modulation device 30. The rod lens 21f is also called a rod integrator, and is a cylinder or a prism having a side surface as a reflection surface. Light beams having various incident angles incident on the rod lens 21f are wavefront-divided and overlapped to be output.

  FIG. 2 is a diagram illustrating the structure of the polarization conversion unit PC. This polarization conversion unit PC includes a quarter-wave plate 52 for changing the polarization state and a reflective polarizing plate 53 for extracting a specific polarization component. Here, the reflection-type polarizing plate 53 is also called a grid-type polarizer, and is formed by periodically forming stripes of Al or the like on a light-transmitting substrate at a pitch of about several hundreds of nm. Only the polarized light in the direction can be selectively transmitted and the rest can be reflected, and there is almost no loss due to absorption.

  The second illumination light IG2 emitted in the front direction from the second light source 21b enters the quarter wavelength plate 52 from one end P1 thereof. Further, the second illumination light IG2 emitted from the second light source 21b in the side surface direction is also reflected by the concave reflecting mirror 21d serving as the reflecting means and enters one end P1 of the quarter-wave plate 52. The light incident from one end P <b> 1 then passes through the reflective polarizing plate 53. By passing through the quarter wavelength plate 52, the linearly polarized light component of the second illumination light IG2 is converted into circularly polarized light. Moreover, by passing through the reflective polarizing plate 53, only the P-polarized light in the second illumination light IG2 selectively passes. The second illumination light IG2 reflected by the reflective polarizing plate 53 is mainly only S-polarized light. However, the second illumination light IG2 is converted into circularly-polarized light by passing through the quarter-wave plate 52, and the concave reflecting mirror 21d. Returned to The second illumination light IG2 reflected by the concave reflecting mirror 21d is incident on the quarter-wave plate 52 and the reflective polarizing plate 53 again. Such re-incident light is converted from circularly polarized light to P-polarized light by the quarter-wave plate 52 and efficiently passes through the reflective polarizing plate 53. As is clear from the above description, the second illumination light IG2 incident on the dichroic mirror DM from the reflective polarizing plate 53 is obtained by converting the light from the second light source 21b into only P-polarized light with high efficiency. .

  Here, although the dichroic mirror DM will be described in detail below, the first illumination light IG1 is reflected almost 100%, and the P-polarized second illumination light IG2 is also transmitted with high efficiency. , 21b can be combined with extremely low loss. At this time, since the wavelengths of both illumination lights IG1 and IG2 are close, it is possible to provide a solid G light source with high purity and high brightness. Further, since both the light sources 21a and 21b are arranged on the optical axis, the characteristics of the illumination light from both the light sources 21a and 21b can be made to be incident on the liquid crystal light valve 31, and the illumination light from the liquid crystal light valve 31 can be incident. Can improve the efficiency of use.

FIG. 3 is a graph for explaining the characteristics of the dichroic mirror DM shown in FIG. In the graph, the horizontal axis indicates the wavelength (nm) and the vertical axis indicates the transmittance (%).
Although this dichroic mirror DM is a high-pass filter, its main surface is inclined by 45 ° with respect to the optical axis, so that the transmittance has polarization dependency. That is, the first edge wavelength λE1 (10% transmission) corresponding to the transmission end of P-polarized light is about 490 nm, and the second edge wavelength λE2 (10% transmission) corresponding to the transmission end of S-polarized light is about 525 nm. In this graph, the luminance distributions of the first and second illumination lights IG1 and IG2 from the first and second light sources 21a and 21b are superimposed and displayed in arbitrary units (vertical axis). As is clear from the graph, the center wavelength λG1 of the first illumination light IG1 is set on the shorter wavelength side than the first edge wavelength λE1. Further, the center wavelength λG2 of the second illumination light IG2 is set in a difference generation region where the transmittance is different between the first edge wavelength λE1 and the second edge wavelength λE2, that is, between P-polarized light and S-polarized light.
Thereby, the first illumination light IG1 from the first light source 21a is reflected almost 100% by the dichroic mirror DM. On the other hand, since the second illumination light IG2 from the second light source 21b is converted into P-polarized light with high efficiency via the polarization conversion unit PC, it passes through the dichroic mirror DM at a high rate.

  The first and second illumination lights IG1 from the first light source 21a pass through the dichroic mirror DM, and the second illumination light IG2 from the second light source 21b is reflected by the dichroic mirror DM. It is also possible to combine illumination light. In this case, the center wavelength λG2 of the second illumination light IG2 remains set between the pair of edge wavelengths λE1 and λE2, but the center wavelength λG1 ′ of the first illumination light IG1 ′ is the second edge wavelength λE2. Is set to the longer wavelength side. Accordingly, the first illumination light IG1 'from the first light source 21a is transmitted through the dichroic mirror DM at a high rate. On the other hand, the second illumination light IG2 from the second light source 21b is converted into S-polarized light instead of P-polarized light through the polarization conversion unit PC whose arrangement direction is changed, and is almost 100% reflected by the dichroic mirror DM. As a result, both illumination lights IG1 'and IG2 from both light sources 21a and 21b can be combined with extremely low loss, and the liquid crystal light valve 31 for G light can be illuminated with high luminance.

  Returning to FIG. 1, the B light illumination device 23 includes a third light source 23a, a concave reflecting mirror 23d, and a rod lens 23f. The third light source 23a is an LED that generates B light included in the category of blue (B) among the three primary colors. The third illumination light IB from the third light source 23a is collected without waste by the concave reflecting mirror 23d and enters the rod lens 23f. The third illumination light IB incident on the rod lens 23 f is made uniform by the rod lens 23 f and enters the liquid crystal light valve 33 for B light in the light modulation device 30.

  The R light illumination device 25 includes a fourth light source 25a, a concave reflecting mirror 25d, and a rod lens 25f. The fourth light source 25a is an LED that generates R light included in the category of red (R) among the three primary colors. The fourth illumination light IR from the fourth light source 25a is collected without waste by the concave reflecting mirror 25d and enters the rod lens 25f. The fourth illumination light IR incident on the rod lens 25f is made uniform by the rod lens 25f and enters the liquid crystal light valve 35 for R light in the light modulator 30.

  Light from each of the illuminating devices 21, 23, 25 incident on the liquid crystal light valves 31, 33, 35 is two-dimensionally modulated by the liquid crystal light valves 31, 33, 35, respectively. The light of each color that has passed through the liquid crystal light valves 31, 33, and 35 is combined by the cross dichroic prism 37 and emitted from one side surface thereof. The combined light image emitted from the cross dichroic prism 37 is incident on the projection lens 40 and projected onto a screen (not shown) provided outside the projector 10 at an appropriate magnification. That is, the projector 10 projects an image obtained by synthesizing the RGB images formed on the liquid crystal light valves 31, 33, and 35 on the screen as a moving image or a still image. Although not shown, an appropriate polarizing plate is provided at appropriate positions around the liquid crystal light valves 31, 33, 35 to illuminate and read the liquid crystal light valves 31, 33, 35 with polarized light. Arranged in an appropriate state.

  According to the projector 10 of the first embodiment described above, the first and second illumination lights IG1 and IG2 are efficiently combined using the dichroic mirror DM and the polarization conversion unit PC. The luminance can be improved while maintaining the pure chromaticity of the G color illumination light.

[Second Embodiment]
Hereinafter, the projector according to the second embodiment will be described. The structure of this projector is almost the same as that of the first embodiment shown in FIG. 1, but the characteristic of the dichroic mirror is a low-pass filter.

FIG. 4 is a graph illustrating the characteristics of the dichroic mirror DM incorporated in the projector 10 according to the second embodiment. This dichroic mirror DM also has a polarization dependency on the transmittance, the first edge wavelength λE1 (10% transmission) corresponding to the transmission end of P-polarized light is about 520 nm, and the first edge wavelength corresponding to the transmission end of S-polarized light. The two edge wavelength λE2 (10% transmission) is about 490 nm. In this graph, the luminance distributions of the first and second illumination lights IG1 and IG2 from the first and second light sources 21a and 21b are superimposed and displayed in arbitrary units (vertical axis). As is clear from the graph, the center wavelength λG1 of the first illumination light IG1 is set on the longer wavelength side than the first edge wavelength λE1. The center wavelength λG2 of the second illumination light IG2 is set between the first edge wavelength λE1 and the second edge wavelength λE2. Thereby, the first illumination light IG1 from the first light source 21a is reflected almost 100% by the dichroic mirror DM.
On the other hand, since the second illumination light IG2 from the second light source 21b is converted into P-polarized light with high efficiency via the polarization conversion unit PC, it passes through the dichroic mirror DM at a high rate.

  In the above description, the first and second illumination lights IG1 and IG2 are combined by a configuration in which the first illumination light IG1 is reflected by the dichroic mirror DM and the second illumination light IG2 is transmitted through the dichroic mirror DM. However, as described in FIG. 3, the first illumination light IG1 ′ from the first light source 21a is transmitted through the dichroic mirror DM, and the second illumination light IG2 from the second light source 21b is reflected by the dichroic mirror DM. Even with such a configuration, the first and second illumination lights IG1 ′ and IG2 can be combined. In this case, the center wavelength λG2 of the illumination light IG2 remains set between the pair of edge wavelengths λE1 and λE2, but the center wavelength λG1 ′ of the illumination light IG1 ′ is shorter than the second edge wavelength λE2. Set to the side. Thereby, the first illumination light IG1 'from the first light source 21a is transmitted through the dichroic mirror DM at a high rate. On the other hand, the second illumination light IG2 from the second light source 21b is converted into S-polarized light instead of P-polarized light through the polarization conversion unit PC, and is reflected almost 100% by the dichroic mirror DM. As a result, both illumination lights IG1 and IG2 from both light sources 21a and 21b can be combined with extremely low loss.

[Third Embodiment]
Hereinafter, the projector according to the third embodiment will be described. The structure of this projector is almost the same as that of the first embodiment shown in FIG. 1, but the structure of the polarization converter is different.

  FIG. 5 is a diagram illustrating the structure of the polarization conversion unit PC in the projector according to the third embodiment. The polarization conversion unit PC includes a pair of polarization beam splitters 151a and 151b for extracting a polarization component, and a half-wave plate 152 for changing the polarization state. The second illumination light IG2 emitted in the front direction from the second light source 21b is incident on the front polarization beam splitter 151a. Further, the second illumination light IG2 emitted from the second light source 21b in the side surface direction is also reflected by the concave reflecting mirror 21d and enters the front polarizing beam splitter 151a. The second illumination light IG2 incident on the polarization beam splitter 151a passes through the polarization plane PP and is converted into S-polarized light. On the other hand, the P-polarized light reflected by the polarization plane PP is reflected by the polarization plane PP of the adjacent polarization beam splitter 151b and enters the half-wave plate 152. Since the P-polarized light incident on the half-wave plate 152 is converted to S-polarized light, as a result, the second illumination light IG2 emitted from the polarization conversion unit PC is almost completely only S-polarized light. For the sake of simplicity, the drawing shows a state where only the polarization conversion unit PC is viewed from the side for convenience, and therefore the second illumination light IG2 actually incident on the dichroic mirror DM is only P-polarized light. .

  As described above, the second illumination light IG2 that enters the dichroic mirror DM via the polarization conversion unit PC is obtained by efficiently converting the light from the second light source 21b into only P-polarized light. That is, both illumination lights IG1 and IG2 from both light sources 21a and 21b can be combined with extremely low loss. At this time, since the wavelengths of both illumination lights IG1 and IG2 are close, it is possible to provide a solid G light source with high purity and high brightness.

[Fourth Embodiment]
Hereinafter, the projector according to the fourth embodiment will be described. Although the structure of this projector is similar to that of the first embodiment shown in FIG. 1, the G light illumination device includes three light sources having different center wavelengths, and the illumination light from these three light sources is paired with a pair of dichroic mirrors. Combine.

  FIG. 6A is a block diagram illustrating a first configuration example of the G light illumination device, and FIG. 6B is a block diagram illustrating a second configuration example of the G light illumination device.

  In the case of the G light illuminating device 221 shown in FIG. 6A, the dichroic mirror DM2 reflects the illumination light having the center wavelength λ1 from the light source device 261a composed of an LED light source and a concave reflecting mirror. In addition, the illumination light having the center wavelength λ2 from the light source device 261b having the same structure but further having a polarization conversion element for converting to P-polarized light is reflected by the dichroic mirror DM1 and transmitted to the dichroic mirror DM2. Further, the illumination light having the center wavelength λ3 from the light source device 261c further including a polarization conversion element for P polarization conversion is transmitted to the dichroic mirror DM1 and the dichroic mirror DM2. As described above, the illumination light emitted from the dichroic mirror DM2 has high luminance as a result of combining the illumination light from the light source devices 261a, 261b, and 261c. The pair of dichroic mirrors DM1 and DM2 have reflection / transmission characteristics described below, and enables the illumination lights having the center wavelengths λ1, λ2, and λ3 to be combined.

  FIG. 7 is a graph for explaining the transmission characteristics of the dichroic mirrors DM1, DM2 used in the projector according to the fourth embodiment. As is apparent from the graph, both dichroic mirrors DM1 and DM2 are high-pass filters, but the edge wavelength of the dichroic mirror DM1 is longer than the edge wavelength of the dichroic mirror DM2. In both dichroic mirrors DM1 and DM2, the edge wavelength of the P-polarized light indicated by the dotted line is shifted to the shorter wavelength side than the edge wavelength of the S-polarized light indicated by the solid line. The center wavelength λ1 of the illumination light from the light source device 261a is set to a shorter wavelength side than the edge wavelength of the P-polarized light of the dichroic mirror DM2. The central wavelength λ2 of the illumination light from the light source device 261b is set between the P-polarized and S-polarized edge wavelengths of the dichroic mirror DM2 and shorter than the edge wavelength of the P-polarized light of the dichroic mirror DM1. Yes. Further, the center wavelength λ3 of the illumination light from the light source device 261c is set between the P-polarized and S-polarized edge wavelengths of the dichroic mirror DM1 and longer than the S-polarized edge wavelength of the dichroic mirror DM2. Yes.

  In the case of the G light illuminating device 321 in the second configuration example shown in FIG. 6B, dichroic S-polarized illumination light with a center wavelength λ2 from the light source device a composed of an LED light source, a concave reflecting mirror, and a polarization conversion element is dichroic. Reflected by the mirror DM2. Further, the S-polarized illumination light having the center wavelength λ3 from the light source device 361b having the same structure is reflected by the dichroic mirror DM1 and transmitted to the dichroic mirror DM2. Further, the illumination light having the center wavelength λ4 from the light source device 361c having no polarization conversion element is transmitted through the dichroic mirror DM1 and the dichroic mirror DM2. As described above, the illumination light emitted from the dichroic mirror DM2 has high luminance as a result of combining the illumination light from each of the light source devices 361a, 361b, 361c. The pair of dichroic mirrors DM1 and DM2 have the reflection and transmission characteristics shown in FIG. 7, and in particular, the center wavelength λ4 of the illumination light from the light source device 361c is longer than the edge wavelength of the S-polarized light of the dichroic mirror DM1. Is set to the side.

  In the projector according to the fourth embodiment described above, illumination light from three different light source devices 261a, 261b, 261c (or light source devices 361a, 361b, 361c) can be coupled coaxially, and thus a high-intensity monochromatic solid. A light source can be provided.

[Fifth Embodiment]
FIG. 8 is a block diagram illustrating a projector according to the fifth embodiment. A projector 410 according to the fifth embodiment is a modification of the projector 10 according to the first embodiment, and uses a digital mirror device (DMD) instead of a liquid crystal light valve.

  The projector 410 includes an illumination device 420, a digital mirror device 430 that is a light modulator and is also called a tilt mirror device, and a projection lens 40. Here, the illumination device 420 includes a light source device for G light 421, a light source device for B light 423, a light source device for R light 425, a cross dichroic prism 427, and a rod lens 428.

  In this illumination device 420, the G light source device 421 condenses the first and second light sources 21a and 21b that generate a pair of illumination light having approximate center wavelengths, and the illumination light from these light sources 21a and 21b. The concave reflecting mirror 21d, the dichroic mirror DM that is a multiplexing unit that combines the illumination light from both the light sources 21a and 21b, and the polarization conversion unit that converts the illumination light from the second light source 21b into predetermined polarized light. And a polarization conversion unit PC. The first illumination light IG1 from the first light source 21a is collected without waste by the concave reflecting mirror 21d, enters the dichroic mirror DM, is reflected by the dichroic mirror DM, and enters the cross dichroic prism 427. On the other hand, the second illumination light IG2 from the second light source 21b is recovered without waste by the concave reflecting mirror 21d and enters the polarization conversion unit PC. The second illumination light IG2 converted into substantially P-polarized light by the polarization conversion unit PC is incident on the dichroic mirror DM, is transmitted therethrough, and is incident on the cross dichroic prism 427 in a state of being combined with the first illumination light IG1. .

The light source device for B light 423 includes a third light source 23a and a concave reflecting mirror 23d.
The third illumination light IB from the third light source 23a is collected without waste by the concave reflecting mirror 23d and enters the cross dichroic prism 427.

The R light source device 425 includes a fourth light source 25a and a concave reflecting mirror 25d.
The fourth illumination light IR from the fourth light source 25a is collected without waste by the concave reflecting mirror 25d and enters the cross dichroic prism 427.

  In the cross dichroic prism 427, the illumination lights IG1, IG2, IB, IR from the respective light source devices 421, 423, 425 are combined, and in the rod lens 428, the illumination lights IG1, IG2, IB, IR are made uniform.

  The RGB combined light emitted from the rod lens 428 is uniformly projected on the digital mirror device 430 through the lens 429a and the mirror 429b. At this time, the digital mirror device 430 can be illuminated uniformly by appropriately adjusting the position and focal length of the lens 429a.

  The digital mirror device 430 has a known structure and has a number of micromirrors arranged in a two-dimensional matrix and constituting pixels, an actuator that individually adjusts the attitude of these micromirrors, and a control that controls the operation of the actuator. The circuit is integrally formed on the substrate. By inputting an appropriate image signal to the digital mirror device 430, reflected light from the micromirror corresponding to each pixel may or may not enter the pupil of the projection lens 40. An image corresponding to the image signal input to 430 is projected on a screen (not shown).

FIG. 9 is a diagram for explaining the operation of one frame in the projector 410 of the fifth embodiment. 9A shows the frame period, FIG. 9B shows the G gradation expression signal, FIG. 9C shows the B gradation expression signal, and FIG. 9D shows the R gradation expression signal. FIG. 9E shows a clock signal. The G gradation expression signal in FIG. 9B corresponds to the G gradation expression period GK, and the first and second light sources 21a and 21b shown in FIG. Further, the B gradation expression signal in FIG. 9C corresponds to the B gradation expression period BK, and the third light source 23a in FIG. The R gradation expression signal in FIG. 9D corresponds to the R gradation expression period RK, and the fourth light source 25a in FIG. 8 is lit only during this period. The G gradation expression period GK shown in FIG. 9B is divided into ⁿ unit times (2 ⁰ , 2 ¹ , 2 ² ,..., 2 ⁽ⁿ⁻¹⁾ ) corresponding to the n-bit image intensity. Has been.
For example, when the image signal of a specific pixel of G light has the maximum value, the specific micromirror of the digital mirror device 430 is turned on in all of the n unit times, that is, in almost the entire G gradation expression period GK. On the other hand, when the image signal of the specific pixel of G light is the minimum value, the corresponding micromirrors are turned off in all of the n unit times, that is, in almost all the G gradation expression period GK. By such a method, the ON / OFF time of the micromirror is adjusted according to the G color intensity signal in each pixel during the G gradation expression period GK. Similarly, the B gradation expression period BK and the R gradation expression period RK are also divided into n unit times, and the ON / OFF time of the micromirror is adjusted according to the intensity signal of each color.

  According to the projector 410 described above, the two illumination lights IG1 and IG2 from the two light sources 21a and 21b corresponding to the G color can be combined with an extremely low loss and can be incident on the digital mirror device 430. Not only can the brightness of the image be increased, but also the gradation representation periods GK, BK, and RK of the G, B, and R colors can be set to relatively approximate values, and the control of the digital mirror device 430 is compared. Simple and well-balanced.

  In the fifth embodiment described above, the dichroic mirror DM is not limited to a high-pass filter but can be a low-pass filter. In addition, the first illumination light IG1 is reflected and the second illumination light IG2 is transmitted to combine the two, but the first illumination light IG1 is transmitted and the second illumination light IG2 is reflected to combine the two. It is also possible to do.

  Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments. For example, in the projector 10 according to the first embodiment, the light modulation device 30 includes the transmissive liquid crystal light valves 31, 33, and 35. However, the light modulation device 30 may include a reflective liquid crystal element. Further, the liquid crystal light valve may be a light writing type liquid crystal light valve.

  Moreover, although the said embodiment demonstrated the case where the brightness | luminance of G light was raised by combining a pair of G1 light and G2 light with which a wavelength approximates, wavelength is also approximated about the other colors R and B. A pair of light source lights can be combined into one illumination light.

It is a figure which shows the structure of the projector which concerns on 1st Embodiment. It is a figure explaining the structure of the polarization conversion element of FIG. It is a graph explaining the characteristic of a dichroic mirror. The characteristics of the dichroic mirror of the second embodiment will be described. It is a figure explaining the structure of the polarization conversion element of 3rd Embodiment. (A), (b) is a figure explaining 4th Embodiment. It is a graph explaining the transmission characteristic of a dichroic mirror. It is a figure which shows the structure of the projector which concerns on 5th Embodiment. (A)-(e) is a figure explaining operation | movement of the apparatus of FIG.

Explanation of symbols

10 projector, 20 illumination device, 21 G light illumination device, 21a first light source, 21b second light source, 23 B light illumination device, 23a third light source, 25 R light illumination device, 25a fourth light source, 30 light modulation device, 31, 33, 35 Liquid crystal light valve, 37 Cross dichroic prism, 40 projection lens, 52 wavelength plate, 53 reflective polarizing plate, DM dichroic mirror, PC polarization conversion element, λE1 first edge wavelength, λE2 second edge wavelength, λG1 , ΛG2 Center wavelength

Claims (7)

A light source device having first and second light sources that respectively generate first and second illumination lights having different peak wavelengths;
A multiplexing means for combining and emitting the first and second illumination lights when the first and second illumination lights are incident;
Polarization conversion means for converting the second illumination light into linearly polarized light in a predetermined direction and making it incident on the multiplexing means,
The illumination device according to claim 1, wherein the first and second illumination lights belong to one of the three primary colors.   The multiplexing means is an optical multiplexing / branching element that utilizes transmission and reflection of light, and a peak wavelength of the second illumination light is a first edge wavelength of transmission or reflection by the optical multiplexing / branching element with respect to linearly polarized light in the predetermined direction. 2. The illumination according to claim 1, wherein a difference generation region is set between the second edge wavelength of transmission or reflection by the optical coupling / branching element with respect to linearly polarized light orthogonal to the predetermined direction. apparatus.   The illumination device according to claim 2, wherein a central wavelength of the first illumination light is set in the vicinity of the difference generation region outside the difference generation region.   The lighting device according to any one of claims 1 to 3, wherein the multiplexing unit is a dichroic mirror.   The lighting device according to any one of claims 1 to 4, wherein the first and second light sources are solid-state light sources.   The polarization conversion means includes a pair of polarization beam splitters on which light emitted from the second light source sequentially enters, and a wave plate disposed on the emission side of the subsequent polarization beam splitter. The illumination device according to any one of claims 1 to 5. The lighting device according to any one of claims 1 to 6,
A spatial light modulator illuminated by the illumination device;
A projection apparatus comprising: a projection lens that projects an image of the spatial light modulator.

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