Illumination device and projector

Abstract

To provide a high-efficiency illumination device and projector.SOLUTION: An illumination device of the present invention comprises: a first light source unit that emits first light in a first wavelength range; a second light source unit that emits second light in a second wavelength range different from the first wavelength range; a light composition element that combines the first light and second light to emit composite light; a diffusion member that diffuses the composite light emitted from the light composition element; and a concave mirror that condenses the composite light emitted from the light composition element and makes the condensed composite light incident on the diffusion member.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a lighting device and a projector.

Background Art

[0002] For the purpose of improving the performance of projectors, projectors equipped with lighting devices using laser light sources, which are light sources with a wide color gamut and high efficiency, have been proposed. Patent Document 1 below discloses a lighting device including a light source device including a blue laser, a green laser, and a red laser, a condensing optical system that condenses the light emitted from the light source device, and a diffusion plate that diffuses the light emitted from the condensing optical system.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent Document 1 discloses a configuration in which light emitted from lasers of respective colors is synthesized to generate white synthesized light, and then the synthesized light is focused on a diffusion plate using one condenser lens. However, in the configuration in which the synthesized light is focused using one condenser lens, the spot size of the synthesized light on the diffusion plate becomes large. As a result, there arises a problem that the light utilization efficiency in the optical system after the diffusion plate decreases.

Means for Solving the Problems

[0005] In order to solve the above problems, an illumination device according to one aspect of the present invention includes a first light source unit that emits first light in a first wavelength band, a second light source unit that emits second light in a second wavelength band different from the first wavelength band, a light combining element that combines the first light and the second light and emits combined light, a diffusing member that diffuses the combined light emitted from the light combining element, and a concave mirror that condenses the combined light emitted from the light combining element and makes the condensed combined light incident on the diffusing member.

[0006] A projector according to one aspect of the present invention includes an illumination device according to one aspect of the present invention, a light modulation device that modulates light including the combined light emitted from the illumination device according to image information, and a projection optical device that projects the light modulated by the light modulation device.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0008] [First Embodiment] Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. The projector of this embodiment is an example of a liquid crystal projector including an illumination device using a laser diode. In each of the following drawings, for the sake of easy viewing of each component, the scale of the dimensions may be made different depending on the component.

[0009] The projector 10 of this embodiment is a projection-type image display device that displays a color image on a screen (projection surface) SCR. The projector 10 includes three light modulation devices corresponding to each color light of red light LR, green light LG, and blue light LB. The projector 10 includes a laser diode as a light-emitting element of the light source device, from which high-brightness and high-output light can be obtained.

[0010] FIG. 1 is a schematic configuration diagram of the projector 10 of this embodiment. As shown in FIG. 1, the projector 10 includes an illumination device 700, a color separation light guide optical system 200, a red light light modulation device 400R, a green light light modulation device 400G, a blue light light modulation device 400B, a synthesis optical system 500, and a projection optical device 600. The red light light modulation device 400R, the green light light modulation device 400G, and the blue light light modulation device 400B form image light by modulating the light including the combined light LW emitted from the illumination device 700 according to image information. The projection optical device 600 projects the image light onto the screen SCR (projection surface).

[0011] FIG. 2 is a schematic configuration diagram of the illumination device 700. As shown in FIG. 2, the illumination device 700 includes a blue light source unit 20, a green light source unit 30, a red light source unit 40, a light combining element 50, a concave mirror 60, a diffusion device 70, a collimator optical system 80, a double-sided multi-lens array 90, and a superimposing lens 100.

[0012] In the following description, the axis along the emission direction of each color light LB, LR from the blue light source unit 20 and the red light source unit 40 is defined as the X-axis, the axis along the emission direction of the combined light LW from the illumination device 700 is defined as the Y-axis, and the axis perpendicular to the X-axis and the Y-axis is defined as the Z-axis. Also, an axis parallel to the X-axis passing through the focus point P on the diffusion surface 71a of the diffusion plate 71 is defined as the optical axis AX1, and an axis parallel to the Y-axis passing through the focus point P on the diffusion surface (the central axis of the combined light LW emitted from the diffusion plate 71) is defined as the optical axis AX2.

[0013] The blue light source unit 20 includes a blue laser diode array 21 and a first collimator lens array 22. The blue light source unit 20 of the present embodiment corresponds to the first light source unit in the claims.

[0014] The blue laser diode array 21 has a plurality of blue laser diodes 211 arranged in an array. The blue laser diode 211 emits a blue beam LB0 in the +X direction in the first wavelength band. The first wavelength band is, for example, 455 nm ± 10 nm. The number and arrangement of the blue laser diodes 211 are not particularly limited.

[0015] The first collimator lens array 22 is provided on the light emission side of the blue laser diode array 21. The first collimator lens array 22 has a plurality of collimator lenses 221 provided corresponding to each of the plurality of blue laser diodes 211. The collimator lens 221 is composed of a convex lens. The collimator lens 221 collimates the blue beam LB0 emitted from the blue laser diode 211. Hereinafter, the plurality of blue beams LB0 emitted from the first collimator lens array 22 are collectively referred to as blue light LB. Therefore, the blue light LB is parallel light collimated by the first collimator lens array 22. The blue light LB of the present embodiment corresponds to the first light in the claims.

[0016] The green light source unit 30 includes a green laser diode array 31 and a second collimator lens array 32. The green light source unit 30 of the present embodiment corresponds to the second light source unit in the claims.

[0017] The green laser diode array 31 has a plurality of green laser diodes 311 arranged in an array. The green laser diode 311 emits a green beam LG0 in the +Y direction in the second wavelength band. The second wavelength band is, for example, 535 nm ± 10 nm. The number and arrangement of the green laser diodes 311 are not particularly limited.

[0018] The second collimator lens array 32 is provided on the light emission side of the green laser diode array 31. The second collimator lens array 32 has a plurality of collimator lenses 321 provided corresponding to each of the plurality of green laser diodes 311. The collimator lens 321 is composed of a convex lens. The collimator lens 321 collimates the green beam LG0 emitted from the green laser diode 311. Hereinafter, the plurality of green beams LG0 emitted from the second collimator lens array 32 are collectively referred to as green light LG. Therefore, the green light LG is parallel light collimated by the second collimator lens array 32. The green light LG of the present embodiment corresponds to the second light in the claims.

[0019] The red light source unit 40 includes a red laser diode array 41 and a third collimator lens array 42. The red light source unit 40 of the present embodiment corresponds to the third light source unit in the claims.

[0020] The red laser diode array 41 has a plurality of red laser diodes 411 arranged in an array. The red laser diode 411 emits a red beam LR0 in the -X direction in the third wavelength band. The third wavelength band is, for example, 640 nm ± 10 nm. The number and arrangement of the red laser diodes 411 are not particularly limited.

[0021] The third collimator lens array 42 is provided on the light emission side of the red laser diode array 41. The third collimator lens array 42 has a plurality of collimator lenses 421 provided corresponding to each of the plurality of red laser diodes 411. The collimator lens 421 is composed of a convex lens. The collimator lens 421 collimates the red beam LR0 emitted from the red laser diode 411. Hereinafter, the plurality of red beams LR0 emitted from the third collimator lens array 42 are collectively referred to as red light LR. Therefore, the red light LR is parallel light collimated by the third collimator lens array 42. The red light LR of the present embodiment corresponds to the third light in the claims.

[0022] The photosynthetic element 50 is composed of a cross dichroic prism. The cross dichroic prism has a first dichroic mirror 51 and a second dichroic mirror 52. The first dichroic mirror 51 reflects red light LR and transmits green light LG and blue light LB. The second dichroic mirror 52 reflects blue light LB and transmits green light LG and red light LR. Thereby, the photosynthetic element 50 synthesizes the blue light LB emitted from the blue light source unit 20, the green light LG emitted from the green light source unit 30, and the red light LR emitted from the red light source unit 40, and emits the synthesized white light LW toward the concave mirror 60. Since the light emitted from each laser diode is linearly polarized, the synthesized light LW emitted from the photosynthetic element 50 is also linearly polarized.

[0023] The concave mirror 60 is provided on the light emission side (+Y side) of the photosynthetic element 50. The concave mirror 60 has a reflecting surface 60a that reflects the synthesized light LW emitted from the photosynthetic element 50. The concave mirror 60 is composed of an off-axis parabolic mirror. The off-axis parabolic mirror is a mirror in which the reflecting surface is composed of a part of a parabolic surface and the reflecting surface is configured not to intersect the central axis (optical axis) of the parabolic surface. In other words, the off-axis parabolic mirror has a shape in which a part of the parabolic surface that does not include the central axis is left and the other parts are cut off. Therefore, the optical axis J of the concave mirror 60 is at a position that does not intersect the reflecting surface 60a and is located outside the incident range of the synthesized light LW to the concave mirror 60. The concave mirror 60 reflects and condenses the synthesized light LW emitted from the photosynthetic element 50, and makes the condensed synthesized light LW incident on a diffusion plate 71 described later. The specific configuration of the concave mirror 60 is not particularly limited. In FIG. 2, the optical axis J of the concave mirror 60 coincides with the optical axis AX2.

[0024] As described above, since the respective colored lights LB, LG, and LR incident on the photosynthetic element 50 are parallel lights parallelized by the respective collimator lens arrays 22, 32, and 42, the combined light LW incident on the concave mirror 60 from the photosynthetic element 50 is also parallel light. Further, by appropriately setting the orientation of the concave mirror 60 with respect to the photosynthetic element 50, the central axis of the combined light LW incident on the concave mirror 60 and the optical axis J of the concave mirror 60 are parallel. From the characteristics of the off-axis parabolic mirror, if two conditions are satisfied: the light incident on the off-axis parabolic mirror is parallel light, and the central axis of the incident light (the axis parallel to the incident direction) and the optical axis of the off-axis parabolic mirror are parallel, the light reflected by the off-axis parabolic mirror converges at a point (focus) on the optical axis of the off-axis parabolic mirror. Therefore, also in the present embodiment, the combined light LW reflected by the concave mirror 60 converges at a point on the optical axis J of the concave mirror 60. In this specification, when one axis and another axis are parallel, it includes not only the case where one axis and another axis are completely parallel, but also the case where one axis and another axis form an angle within ±5°.

[0025] The diffusing device 70 includes a disk-shaped diffusing plate 71 and a driving device 72. The diffusing plate 71 has a diffusing surface 71a that diffusely reflects the combined light LW emitted from the concave mirror 60. That is, the diffusing plate 71 of the present embodiment is a reflective diffusing plate, not a transmissive diffusing plate. The diffusing plate 71 is disposed at a position where the diffusing surface 71a intersects each of the optical axis AX1 and the optical axis AX2. Further, the diffusing surface 71a of the diffusing plate 71 is disposed at the condensing point P of the combined light LW reflected by the concave mirror 60. In other words, the focal point of the concave mirror 60 is located on the diffusing surface 71a of the diffusing plate 71. Also, the central axis of the combined light LW emitted from the diffusing plate 71 is parallel to the optical axis J of the concave mirror 60.

[0026] The drive device 72 is composed of a motor and rotates the diffusion plate 71 around the rotation axis C1 that intersects the diffusion surface 71a. By rotating the diffusion plate 71, it is possible to reduce the speckle noise that is likely to occur when using a laser diode. Note that the diffusion surface 71a in this specification does not mean a curved surface formed by the shape of a fine uneven structure described later, but means a single plane on which a plurality of concave portions and a plurality of convex portions are generally arranged. The diffusion plate 71 of the present embodiment corresponds to the diffusion member in the claims.

[0027] FIG. 3 is a front view of the diffusion device 70. FIG. 4 is a cross-sectional view of the diffusion plate 71 taken along line IV-IV of FIG. 3. As shown in FIGS. 3 and 4, the diffusion plate 71 has a light-transmissive substrate 710, a metal reflection film 711, and a dielectric multilayer film 712.

[0028] The light-transmissive substrate 710 is composed of, for example, optical glass such as BK7. Among the two surfaces of the light-transmissive substrate 710, an uneven structure 713 composed of a plurality of concave portions and a plurality of convex portions is provided on the diffusion surface 71a where the combined light LW is incident. The uneven structure 713 includes a plurality of curved surfaces arranged randomly. That is, the light-transmissive substrate 710 has an uneven structure 713 including a plurality of concave portions and a plurality of convex portions. Each concave portion is formed in a substantially spherical shape. The depth of the concave portion is, for example, about 1 / 4 of the diameter of the sphere. The uneven structure 713 can be formed by methods such as etching the light-transmissive substrate 710 or plastically deforming it by blasting treatment.

[0029] The metal reflection film 711 is provided along the uneven structure 713 of the light-transmissive substrate 710. The metal reflection film 711 is composed of a material containing, for example, aluminum. Specifically, the metal reflection film 711 is composed of high-purity aluminum with an aluminum content of 99.99 wt% or more. Preferably, the metal reflection film 711 can be selected from ultra-high-purity aluminum with a content of 99.999 wt% or more.

[0030] The metal reflective film 711 is obtained by forming a pure aluminum film with a smooth surface and a predetermined film thickness on the diffusion surface 71a of the light-transmissive substrate 710 using a film-forming method such as sputtering or vapor deposition. In the film-forming process, when a sputtering target with an aluminum content of, for example, 99.999 wt% is used, a metal reflective film 711 made of ultra-high purity aluminum with an aluminum content of 99.999 wt% is obtained.

[0031] The dielectric multilayer film 712 is provided on the surface of the metal reflective film 711 opposite to the light-transmissive substrate 710. That is, the diffusion plate 71 has a structure in which the metal reflective film 711 and the dielectric multilayer film 712 are laminated in this order on the light-transmissive substrate 710. Although not shown in FIG. 4, the dielectric multilayer film 712 has a structure in which a plurality of two types of dielectric films with different refractive indices are alternately laminated.

[0032] In the diffusion plate 71 of the present embodiment, the uneven structure 713 reflects the combined light LW emitted from the concave mirror 60 once and emits it toward the collimator optical system 80. Therefore, the combined light LW emitted from the concave mirror 60 is emitted from the diffusion plate 71 toward the collimator optical system 80 without multiple reflections on the diffusion surface 71a. According to this configuration, since the combined light LW emitted from the concave mirror 60 does not undergo multiple reflections on the diffusion surface 71a, it is possible to suppress the disturbance of the polarization direction of the combined light LW. Note that the diffusion plate 71 may be a micro lens array type diffusion plate provided with a micro lens array.

[0033] Note that, instead of the configuration of FIG. 4, the diffusion plate 71 may be such that the metal reflective film 711 is not provided and the dielectric multilayer film 712 is directly formed on the uneven structure 713 of the light-transmissive substrate 710. According to this configuration, the manufacturing process of the diffusion plate can be simplified. However, in the configuration where the metal reflective film 711 is provided, since both the metal reflective film 711 and the dielectric multilayer film 712 can perform the reflection function, the number of layers of the dielectric multilayer film 712 can be reduced.

[0034] Alternatively, the diffusion plate 71 may be composed of a metal substrate and a dielectric multilayer film 712. As the metal substrate, for example, an aluminum alloy can be used. As the aluminum alloy, for example, an Al-Mg-Si alloy in which magnesium (Mg) and silicon (Si) are added to aluminum (Al) is used. In addition, the aluminum alloy may contain elements such as iron (Fe), copper (Cu), manganese (Mn), chromium (Cr), zinc (Zn), titanium (Ti), etc. In this case, by subjecting the metal substrate to a blasting treatment, an uneven structure can be formed on one surface of the metal substrate, and the dielectric multilayer film 712 can be formed on the uneven structure. According to this configuration, the configuration of the diffusion plate can be simplified.

[0035] As shown in FIG. 2, the collimator optical system 80 is provided on the light emission side of the diffusion plate 71 on the optical axis AX2. The collimator optical system 80 is composed of a convex lens. The collimator optical system 80 collimates the combined light LW emitted from the diffusion plate 71 at a predetermined diffusion angle and emits it toward the double-sided multi-lens array 90.

[0036] The double-sided multi-lens array 90 and the superimposing lens 100 constitute an integrator optical system. The integrator optical system equalizes the illuminance distribution of the combined light LW emitted from the collimator optical system 80 in the respective image formation regions of the red light light modulator 400R, the green light light modulator 400G, and the blue light light modulator 400B.

[0037] The double-sided multi-lens array 90 is provided on the light emission side of the collimator optical system 80 on the optical axis AX2. The double-sided multi-lens array 90 is a multi-lens array in which the first multi-lens surface 90a and the second multi-lens surface 90b are integrated into one member. The first multi-lens surface 90a has a plurality of lenses for dividing the combined light LW emitted from the collimator optical system 80 into a plurality of partial light beams. The plurality of lenses are arranged in a matrix in a plane orthogonal to the optical axis AX2. The double-sided multi-lens array 90 of the present embodiment corresponds to the multi-lens optical system in the claims.

[0038] The second multi-lens surface 90b has a plurality of lenses corresponding to the plurality of lenses of the first multi-lens surface 90a. The second multi-lens surface 90b, together with the subsequent superimposing lens 100, forms an image of each lens of the first multi-lens surface 90a in each image formation region of the red light light modulation device 400R, the green light light modulation device 400G, and the blue light light modulation device 400B or in the vicinity thereof. The plurality of lenses are arranged in a matrix in a plane orthogonal to the optical axis AX2. Note that the first multi-lens surface 90a and the second multi-lens surface 90b may be provided separately as two multi-lens arrays. Further, a driving device for vibrating or swinging the double-sided multi-lens array 90 in a direction orthogonal to the optical axis AX2 (a direction along the XZ plane) may be provided. By vibrating or swinging the double-sided multi-lens array 90, it is possible to reduce the speckle noise that is likely to occur when using a laser diode.

[0039] The superimposing lens 100 condenses each of the plurality of partial light beams emitted from the double-sided multi-lens array 90 and superimposes them on each other in each image formation region of the red light light modulation device 400R, the green light light modulation device 400G, and the blue light light modulation device 400B or in the vicinity thereof.

[0040] As shown in FIG. 1, the color separation light guiding optical system 200 includes a dichroic mirror 240, a dichroic mirror 220, a reflection mirror 210, a reflection mirror 230, and a reflection mirror 250. The color separation light guiding optical system 200 separates the white combined light LW emitted from the illumination device 700 into red light LR, green light LG, and blue light LB, and guides the red light LR, the green light LG, and the blue light LB to the corresponding red light light modulation device 400R, green light light modulation device 400G, and blue light light modulation device 400B, respectively.

[0041] A field lens 300R is disposed between the color separation light guide optical system 200 and the red light use light modulation device 400R. A field lens 300G is disposed between the color separation light guide optical system 200 and the green light use light modulation device 400G. A field lens 300B is disposed between the color separation light guide optical system 200 and the blue light use light modulation device 400B.

[0042] The dichroic mirror 240 reflects the blue light LB and transmits the red light LR and the green light LG. The dichroic mirror 220 reflects the green light LG and transmits the blue light LB. Each of the reflecting mirrors 210 and 230 reflects the red light LR. The reflecting mirror 250 reflects the blue light LB.

[0043] The red light use light modulation device 400R is composed of a liquid crystal panel that modulates the red light LR according to image information to form an image. The green light use light modulation device 400G is composed of a liquid crystal panel that modulates the green light LG according to image information to form an image. The blue light use light modulation device 400B is composed of a liquid crystal panel that modulates the blue light LB according to image information to form an image.

[0044] Although not shown, incident side polarizing plates are disposed between the field lens 300R and the red light use light modulation device 400R, between the field lens 300G and the green light use light modulation device 400G, and between the field lens 300B and the blue light use light modulation device 400B, respectively. Exit side polarizing plates are disposed between the red light use light modulation device 400R and the combining optical system 500, between the green light use light modulation device 400G and the combining optical system 500, and between the blue light use light modulation device 400B and the combining optical system 500, respectively. Note that the incident side polarizing plate may not be provided if the polarization disturbance by the optical system after being emitted from the illumination device 700 is tolerable.

[0045] The synthetic optical system 500 synthesizes the respective image lights emitted from the red light light modulation device 400R, the green light light modulation device 400G, and the blue light light modulation device 400B. The synthetic optical system 500 is composed of a cross dichroic prism having a substantially square shape in plan view formed by bonding four right-angled prisms. In the cross dichroic prism, a dielectric multilayer film is provided on a substantially X-shaped interface where the right-angled prisms are bonded to each other.

[0046] The image light emitted from the synthetic optical system 500 is enlarged and projected onto the screen SCR by the projection optical device 600. The projection optical device 600 is composed of a plurality of lenses.

[0047] [Effects of the First Embodiment] The lighting device 700 of the present embodiment includes a blue light source unit 20 that emits blue light LB, a green light source unit 30 that emits green light LG, a red light source unit 40 that emits red light LR, a light synthesizing element 50 that synthesizes the blue light LB, the green light LG, and the red light LR and emits synthesized light LW, a diffusion plate 71 that diffuses the synthesized light LW emitted from the light synthesizing element 50, and a concave mirror 60 that condenses the synthesized light LW emitted from the light synthesizing element 50 and makes the condensed synthesized light LW incident on the diffusion plate 71. Further, the concave mirror 60 is composed of an off-axis parabolic mirror.

[0048] In a conventional configuration in which white composite light is condensed onto a diffusion plate using a single condenser lens, since the optical material constituting the condenser lens has wavelength dispersion, the substantial refractive index differs depending on the wavelength of light, and thus chromatic aberration cannot be avoided. Therefore, when focusing on a specific color light, blurring occurs in other color lights, and the spot of the composite light on the diffusion plate as a whole becomes larger. As a result, the image on the injection-side multi-lens array at the subsequent stage of the diffusion plate, that is, the secondary light source image, becomes larger, and the étendue becomes larger. This causes a problem that the light utilization efficiency in the subsequent optical system decreases. Further, in order to suppress the decrease in light utilization efficiency as much as possible, it is necessary to improve the positional accuracy of optical components such as the multi-lens array and the laser diode at the subsequent stage of the diffusion plate, which increases the load on the assembly process of the lighting device. Although chromatic aberration can be corrected by using a combination lens including a convex lens and a concave lens in the condenser optical system, in this case, there is a risk of increasing the size and cost of the lighting device.

[0049] In response to the above problem, according to the lighting device 700 of the present embodiment, since a concave mirror 60 is used as the condensing means for the diffusion plate 71 instead of the conventional lens, chromatic aberration does not occur in principle. Further, since the concave mirror 60 is composed of an off-axis parabolic mirror, spherical aberration that occurs when using a spherical mirror does not occur in principle. As described above, the composite light LW reflected by the concave mirror 60 converges on a single point on the optical axis J of the concave mirror 60, that is, a single point on the diffusion plate 71. Further, when using a concave mirror 60 composed of an off-axis parabolic mirror, the focal length can be made smaller compared to the case of using a lens.

[0050] From these, according to the lighting device 700 of the present embodiment, the spot size of the combined light LW on the diffusion plate 71 can be made smaller than that of the conventional lighting device. As a result, the secondary light source image formed on the second multi-lens surface 90b of the double-sided multi-lens array 90 can be made smaller, so that an illumination device 700 with a small étendue and excellent light utilization efficiency can be realized. In addition, since the secondary light source image can be made smaller, the positional accuracy of optical components such as the double-sided multi-lens array 90 and the laser diodes 211, 311, 411, etc. can be relaxed, and the load on the assembly process of the lighting device 700 can be reduced. Furthermore, since it is not necessary to use a lens for chromatic aberration correction, the increase in size and cost of the lighting device 700 can be suppressed.

[0051] In the case of the present embodiment, an off-axis parabolic mirror is used as the concave mirror 60, and the optical axis J of the concave mirror 60 does not intersect the reflecting surface 60a and is located outside the incident range of the combined light LW. In other words, among the parabolic mirrors, only the minimum necessary part that does not include the optical axis J is left, and the concave mirror 60 obtained by cutting the other parts is used. Therefore, it is possible to avoid physical interference between the optical components such as the diffusion plate 71 and the collimator optical system 80 and the concave mirror 60. As a result, the loss of the combined light LW can be suppressed, and the size reduction of the lighting device 700 can be achieved.

[0052] The projector 10 of the present embodiment includes the lighting device 700 of the present embodiment, light modulation devices 400R, 400G, 400B that modulate light including the combined light LW emitted from the lighting device 700 according to image information, and a projection optical device 600 that projects the light modulated by the light modulation devices 400R, 400G, 400B.

[0053] According to this configuration, a projector 10 with excellent light utilization efficiency can be realized.

[0054] [Second Embodiment] Hereinafter, the second embodiment of the present invention will be described with reference to FIG. 5. The basic configuration of the projector according to the second embodiment is the same as that of the first embodiment, and the configuration of the lighting device is different from that of the first embodiment. Therefore, the description of the basic configuration of the projector is omitted.

[0055] FIG. 5 is a schematic configuration diagram of the lighting device 720 according to the second embodiment. In FIG. 5, the same reference numerals are given to the components common to FIG. 2 used in the first embodiment, and the description thereof is omitted.

[0056] As shown in FIG. 5, the lighting device 720 of the present embodiment includes a blue light source unit 20, a green light source unit 30, a red light source unit 40, a light synthesizing element 50, a concave mirror 60, a diffusing device 74, a collimator optical system 80, a double-sided multi-lens array 90, and a superimposing lens 100. The basic configuration of the lighting device 720 is the same as that of the lighting device 700 of the first embodiment, and the configuration of the diffuser plate 75 is different from that of the diffuser plate 71 of the first embodiment.

[0057] The diffuser plate 75 diffuses while transmitting the combined light LW emitted from the concave mirror 60. That is, the diffuser plate 75 of the present embodiment is a transmissive diffuser plate, which is different from the diffuser plate 71 of the first embodiment. The diffuser plate 75 may be composed of a light-transmissive substrate provided with an uneven structure, or may be composed of a light-transmissive substrate containing a light-scattering material. The diffuser plate 75 is disposed at the condensing point P of the combined light LW reflected by the concave mirror 60. In the case of the present embodiment, the light source units 20, 30, 40 of each color, the light synthesizing element 50, and the concave mirror 60 are arranged in a direction rotated 90 degrees clockwise with respect to these members of the first embodiment, and the diffuser plate 75 is arranged parallel to the optical axis J of the concave mirror 60. Other configurations of the lighting device 720 are the same as those of the lighting device 700 of the first embodiment.

[0058] [Effects of the Second Embodiment] Even in this embodiment, since the spot size on the diffusion plate 75 can be made smaller than that of a conventional lighting device, the secondary light source image can be made smaller, and a lighting device 720 with excellent light utilization efficiency can be realized. The positional accuracy of optical components such as the double-sided multi-lens array 90 can be relaxed, and the load in the assembly process of the lighting device 720 can be reduced. Since there is no need to use a lens for chromatic aberration correction, an increase in the size and cost of the lighting device 720 can be suppressed. The same effects as those of the first embodiment can be obtained.

[0059] Note that the technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. The lighting device of the above embodiment includes an off-axis paraboloidal mirror as a condensing means for the diffusion plate, but instead of the off-axis paraboloidal mirror, a spherical mirror may be provided. Even with this configuration, chromatic aberration can be eliminated. Also, when there is no problem with physical interference between optical components or a decrease in light utilization efficiency, instead of the off-axis paraboloidal mirror, a paraboloidal mirror having an optical axis at a position intersecting the reflecting surface may be used. Further, the lighting device of the above embodiment includes a rotary diffusion plate, but the diffusion plate does not necessarily have to be rotatable and may be fixed.

[0060] In addition, specific descriptions of the shape, number, arrangement, material, etc. of each component of the lighting device and the projector are not limited to the above embodiment and can be appropriately changed. Also, in the above embodiment, an example in which the lighting device according to the present invention is mounted on a projector using a liquid crystal panel is shown, but it is not limited to this. The lighting device according to the present invention may be applied to a projector using a digital micromirror device as a light modulation device. Also, the projector does not necessarily have to have a plurality of light modulation devices and may be a single-plate projector having only one light modulation device.

[0061] In the above embodiment, an example in which the lighting device of the present invention is applied to a projector is shown, but it is not limited to this. The lighting device of the present invention can also be applied to lighting fixtures, automobile headlights, etc.

[0062] [Summary of the Present Disclosure] The summary of the present disclosure is appended below.

[0063] (Appendix 1) A first light source unit that emits first light in a first wavelength band; A second light source unit that emits second light in a second wavelength band different from the first wavelength band; A light combining element that combines the first light and the second light and emits combined light; A diffusing member that diffuses the combined light emitted from the light combining element; A concave mirror that condenses the combined light emitted from the light combining element and makes the condensed combined light incident on the diffusing member; An illumination device comprising the above.

[0064] According to the configuration of Appendix 1, since a concave mirror is used as a condensing means for the diffusing member, chromatic aberration does not occur, and an illumination device with excellent light utilization efficiency can be realized.

[0065] (Appendix 2) The illumination device according to Appendix 1, wherein the concave mirror is an off-axis parabolic mirror.

[0066] According to the configuration of Appendix 2, the occurrence of spherical aberration can be suppressed in addition to chromatic aberration. Also, since physical interference between optical components such as the diffusing member and the concave mirror is avoided, loss of combined light can be suppressed and miniaturization of the illumination device can be achieved.

[0067] (Appendix 3) The combined light incident on the off-axis parabolic mirror is parallel light, and the central axis of the combined light incident on the off-axis parabolic mirror is parallel to the optical axis of the off-axis parabolic mirror. The illumination device according to Appendix 1 or Appendix 2.

[0068] According to the configuration of Appendix 3, the combined light reflected by the off-axis parabolic mirror can be focused on the focal point on the optical axis of the off-axis parabolic mirror. Thereby, the light utilization efficiency can be sufficiently increased.

[0069] (Supplementary Note 4) The optical axis of the off-axis paraboloidal mirror is located outside the incident range of the combined light to the off-axis paraboloidal mirror, and the lighting device according to Supplementary Note 3.

[0070] According to the configuration of Supplementary Note 4, physical interference between optical components such as a diffusion member and the off-axis paraboloidal mirror can be reliably avoided.

[0071] (Supplementary Note 5) The focus of the off-axis paraboloidal mirror is located on the diffusion surface of the diffusion member, and the lighting device according to Supplementary Note 3 or Supplementary Note 4.

[0072] According to the configuration of Supplementary Note 5, the combined light reflected by the off-axis paraboloidal mirror can be focused on the diffusion surface of the diffusion member. Thereby, the spot size of the combined light on the diffusion surface can be minimized, and the light utilization efficiency can be sufficiently increased.

[0073] (Supplementary Note 6) The diffusion member is a reflective diffusion member that diffusely reflects the combined light, The central axis of the combined light emitted from the diffusion member is parallel to the optical axis of the off-axis paraboloidal mirror, and the lighting device according to Supplementary Note 4 or Supplementary Note 5.

[0074] According to the configuration of Supplementary Note 6, compared with the case of using a transmissive diffusion member, the loss associated with light scattering can be reduced, and the light utilization efficiency can be increased. Also, the diffusion member and the off-axis paraboloidal mirror can be efficiently arranged, and the miniaturization of the lighting device can be achieved.

[0075] (Supplementary Note 7) Further comprising a third light source unit that emits third light in a third wavelength band different from the first wavelength band and the second wavelength band, The optical synthesis element synthesizes the first light, the second light, and the third light, The first wavelength band is a blue wavelength band, the second wavelength band is a green wavelength band, and the third wavelength band is a red wavelength band, and the lighting device according to any one of Supplementary Notes 1 to 6.

[0076] According to the configuration of Supplementary Note 7, an illumination device that emits white synthetic light can be realized.

[0077] (Supplementary Note 8) The illumination device according to Supplementary Note 7, wherein each of the first light source unit, the second light source unit, and the third light source unit has a laser diode.

[0078] According to the configuration of Supplementary Note 8, an illumination device that has a wide color gamut, high efficiency, and can emit linearly polarized light can be realized.

[0079] (Supplementary Note 9) The illumination device according to Supplementary Note 8, further comprising a driving device that rotates the diffusion member about a rotation axis intersecting the diffusion surface.

[0080] According to the configuration of Supplementary Note 9, speckle noise caused by using a laser diode can be reduced.

[0081] (Supplementary Note 10) A collimator optical system that collimates the synthetic light emitted from the diffusion member, A multi-lens optical system that divides the synthetic light emitted from the collimator optical system into a plurality of partial light beams, A superposition lens that superposes the plurality of partial light beams emitted from the multi-lens optical system on the illuminated surface, The illumination device according to any one of Supplementary Notes 1 to 9, further comprising:

[0082] According to the configuration of Supplementary Note 10, the secondary light source image on the output-side multi-lens surface of the multi-lens optical system can be reduced, and an illumination device with excellent light utilization efficiency can be realized.

[0083] (Supplementary Note 11) The illumination device according to any one of Supplementary Notes 1 to 10, An optical modulation device that modulates light including the synthetic light emitted from the illumination device according to image information, A projection optical device that projects the light modulated by the light modulation device, A projector comprising the same.

[0084] According to the configuration of Supplementary Note 11, a projector with high light utilization efficiency can be realized.

Explanation of Signs

[0085] 10…Projector, 20…Blue light source unit (first light source unit), 30…Green light source unit (second light source unit), 40…Red light source unit (third light source unit), 50…Light combining element, 60…Concave mirror, 71, 75…Diffusion plate (diffusion member), 72…Drive device, 80…Collimator optical system, 90…Dual-sided multi-lens array (multi-lens optical system), 100…Superposition lens, 400R…Light modulation device for red light, 400G…Light modulation device for green light, 400B…Light modulation device for blue light, 600…Projection optical device, 700, 720…Illumination device, LB…Blue light (first light), LG…Green light (second light), LR…Red light (third light), LW…Combined light.

Claims

1. A first light source unit that emits a first light in a first wavelength band; a second light source unit that emits a second light of a second wavelength band different from the first wavelength band; a light combining element that combines the first light and the second light and emits a combined light; A diffusion member that diffuses the combined light emitted from the light combining element; a concave mirror that collects the combined light emitted from the light combining element and causes the collected combined light to be incident on the diffusing member; A lighting device comprising:

2. The illumination device of claim 1 , wherein the concave mirror is an off-axis parabolic mirror.

3. 3. The lighting device according to claim 1, wherein the combined light incident on the off-axis parabolic mirror is a parallel light, and a central axis of the combined light incident on the off-axis parabolic mirror is parallel to an optical axis of the off-axis parabolic mirror.

4. The lighting device according to claim 3 , wherein an optical axis of the off-axis parabolic mirror is positioned outside an incidence range of the combined light onto the off-axis parabolic mirror.

5. The illumination device of claim 3 , wherein a focal point of the off-axis parabolic mirror is located on a diffusing surface of the diffusing member.

6. the diffusion member is a reflective diffusion member that diffuses and reflects the combined light, The illumination device according to claim 4 , wherein a central axis of the combined light emitted from the diffusing member is parallel to an optical axis of the off-axis parabolic mirror.

7. a third light source unit configured to emit a third light of a third wavelength band different from the first wavelength band and the second wavelength band, the light combining element combines the first light, the second light, and the third light, 3. The illumination device according to claim 1, wherein the first waveband is a blue waveband, the second waveband is a green waveband, and the third waveband is a red waveband.

8. The illumination device according to claim 7 , wherein each of the first light source unit, the second light source unit, and the third light source unit includes a laser diode.

9. The lighting device according to claim 8 , further comprising a drive device that rotates the diffusing member about a rotation axis that intersects with a diffusing surface.

10. a collimator optical system that collimates the combined light emitted from the diffusing member; a multi-lens optical system that divides the combined light emitted from the collimator optical system into a plurality of partial light beams; a superimposing lens that superimposes the plurality of partial light beams emitted from the multi-lens optical system on an illuminated surface; The lighting device according to claim 1 or 2, further comprising:

11. The lighting device according to claim 1 or 2, a light modulation device that modulates light including the composite light emitted from the illumination device in accordance with image information; a projection optical device that projects the light modulated by the light modulation device; A projector equipped with

Images