JP2021086009A - Light source device and projector - Google Patents

Abstract

To provide a small-sized light source device that reduces reduction in illuminance in a center part of an illumination target area.SOLUTION: A light source device of the present application comprises: a first light source; a second light source; a third light source; a fourth light source; a diffusion element; a first light path changing element; a second light path changing element; a third light path changing element; and a fourth light path changing element. The first light source forms a first light source image at a first position on the diffusion element; the second light source forms a second light source image at a second position on the diffusion element; the third light source forms a third light source image at a third position on the diffusion element; the fourth light source forms a fourth light source image at a fourth position on the diffusion element. A longitudinal direction of the first light source image and a longitudinal direction of the third light source image extend along a first direction on the diffusion element; a longitudinal direction of the second light source image and a longitudinal direction of the fourth light source image extend along a second direction orthogonal to the first direction on the diffusion element; a first phase difference plate is provided on a light path of first light; a second phase difference plate is provided on a light path of third light.SELECTED DRAWING: Figure 4

Description

The present application relates to a light source device and a projector.

A laser light source is attracting attention as a light source device used in a projector. In Patent Document 1 below, a laser light source having a plurality of light emitting points, a condensing lens that condenses a plurality of laser beams emitted from a plurality of light emitting points, and a plurality of lasers condensing by the condensing lens A laser light source device including a diffuser element that widens each diffusion angle of light is disclosed.

Japanese Unexamined Patent Publication No. 2008-96777

In the light source device of Patent Document 1, for example, if the distance from the laser light source to the diffusing element is shortened by omitting the condenser lens in order to reduce the size, a diffusing element having a wide diffusion angle is required. However, when a transmission type diffusion element is used, if the diffusion angle is made too wide, the light transmittance is lowered due to the influence of total internal reflection. Therefore, in order to secure the light transmittance, it is necessary to use a diffusion element having a relatively narrow diffusion angle.

Even if the diffusion element having a narrow diffusion angle is irradiated with light from one laser light source, no particular problem occurs. However, for example, when light is irradiated from a plurality of laser light sources to a diffusing element having a narrow diffusion angle for the purpose of increasing the brightness of the light source device, it is close to the central portion of the diffusing element, that is, the optical axis of the diffusing element. The desired illuminance could not be obtained in the region, and the illuminance distribution on the diffuser element might become non-uniform. As a result, in the projector equipped with this laser light source device, there is a possibility that brightness unevenness and color unevenness of the projected image may occur.

In order to solve the above problems, the light source device of one aspect of the present application emits a first light source that emits a first light, a second light source that emits a second light, and a third light. A third light source, a fourth light source that emits a fourth light, a diffusing element that diffuses the first light, the second light, the third light, and the fourth light, and the first. Between the first light path changing element provided on the optical path of the first light between the one light source and the diffusing element and folding back the optical path of the first light, and between the second light source and the diffusing element. A second light path changing element provided on the light path of the second light and folding back the light path of the second light, and a third light path between the third light source and the diffusion element are provided. A third light path changing element that folds back the light path of the third light is provided on the fourth light path between the fourth light source and the diffuser, and the fourth light path is provided. A fourth light path changing element that folds back is provided, the first light source forms a first light source image at a first position on the diffuser, and the second light source forms a second light source image on the diffuser. The third light source is formed at a second position different from the first position, and the third light source image is formed at the first position on the diffuser and a third position different from the second position. The fourth light source forms the fourth light source image at the first position, the second position, and the fourth position different from the third position on the diffuser, and forms the fourth light source image in the longitudinal direction of the first light source image and the first position. The longitudinal direction of the three light source images is along the first direction on the diffuser element, and the longitudinal direction of the second light source image and the longitudinal direction of the fourth light source image are orthogonal to the first direction on the diffuser element. Along the second direction, a first retardation plate is provided on the optical path of the first light, and a second retardation plate is provided on the optical path of the third light.

In the light source device of one aspect of the present application, the first optical path changing element includes a first front-stage mirror that reflects the first light emitted from the first light source and the first front-stage mirror that reflects the first front-stage mirror. It has a first rear-stage mirror that reflects the light of 1, and the second optical path changing element has a second front-stage mirror that reflects the second light emitted from the second light source and the second front-stage mirror. A third rear-stage mirror that reflects the second light reflected by the mirror, and the third optical path changing element reflects the third light emitted from the third light source. And a third rear-stage mirror that reflects the third light reflected by the third front-stage mirror, and the fourth optical path changing element emits the fourth light emitted from the fourth light source. It may have a fourth front-stage mirror that reflects the light and a fourth rear-stage mirror that reflects the fourth light reflected by the fourth front-stage mirror.

In the light source device of one aspect of the present application, the first light source image, the second light source image, the third light source image, and the fourth light source image are one of the first light source images on the diffuser. One short side of the second light source image faces one long side of the second light source image, one short side of the second light source image faces one long side of the third light source image, and one of the third light source images. The short side may be arranged so as to face one long side of the fourth light source image and one short side of the fourth light source image to face one long side of the first light source image. ..

In the light source device of one aspect of the present application, the first phase difference plate is composed of a 1/2 wave plate with respect to the wavelength band of the first light, and the second phase difference plate is of the third light. It may be composed of a 1/2 wave plate for a wavelength band.

The projector of one aspect of the present application projects a light source device of one aspect of the present application, an optical modulator that modulates light from the light source device according to image information, and light modulated by the optical modulator. It is equipped with a projection optical device.

It is a schematic block diagram of the projector of 1st Embodiment. It is a schematic block diagram of the 1st light source apparatus. It is a schematic block diagram of the 2nd light source apparatus. It is a perspective view of the main part of the 2nd light source device. It is a figure which shows the arrangement of a plurality of light source images on a diffusing element. It is a figure which shows the illuminance distribution of the light flux emitted from a diffusing element. It is a figure which shows the arrangement of a plurality of light source images on a diffusing element by the 2nd light source device of a modification. It is a figure which shows the illuminance distribution of the light flux emitted from a diffusing element. It is a schematic block diagram of the light source apparatus of the 1st comparative example. It is a figure which shows the illuminance distribution of the light flux emitted from a diffusing element. It is a schematic block diagram of the light source apparatus of the 2nd comparative example. It is a figure which shows the illuminance distribution of the light flux emitted from a diffusing element. It is a schematic block diagram of the 2nd light source apparatus of 2nd Embodiment.

[First Embodiment]
Hereinafter, the first embodiment of the present application will be described with reference to FIGS. 1 to 12.
FIG. 1 is a schematic configuration diagram of the projector of the present embodiment.
In each of the following drawings, in order to make each component easy to see, the scale of dimensions may be different depending on the component.

As shown in FIG. 1, the projector 1 of the present embodiment includes an illumination device 100, a color separation light guide optical system 200, an optical modulation device 400, a cross dichroic prism 500, and a projection optical device 600. The light modulation device 400 includes a light modulation element 400R for red light, a light modulation element 400G, and a light modulation element 400B.

The lighting device 100 includes a first light source device 101 and a second light source device 102. The first light source device 101 emits a yellow fluorescent YL containing red light R and green light G toward the color separation light guide optical system 200. The second light source device 102 emits blue light B toward the color-separated light guide optical system 200.

The color separation light guide optical system 200 includes a dichroic mirror 210, a reflection mirror 220, a reflection mirror 230, and a reflection mirror 250. The color separation light guide optical system 200 separates the yellow fluorescent YL emitted from the first light source device 101 into red light R and green light G, guides the red light R to the light modulation element 400R, and transmits the green light G. It leads to the optical modulation element 400G. Further, the color separation light guide optical system 200 guides the blue light B emitted from the second light source device 102 to the light modulation element 400B.

The field lens 300R is provided between the color-separated light guide optical system 200 and the light modulation element 400R. The field lens 300G is provided between the color-separated light guide optical system 200 and the light modulation element 400G. The field lens 300B is provided between the color-separated light guide optical system 200 and the light modulation element 400B.

The dichroic mirror 210 transmits the red light R and reflects the green light G. The reflection mirror 220 reflects the green light G reflected by the dichroic mirror 210. The reflection mirror 230 reflects the red light R transmitted through the dichroic mirror 210. The reflection mirror 250 reflects the blue light B emitted from the second light source device 102.

The red light R transmitted through the dichroic mirror 210 is reflected by the reflection mirror 230, passes through the field lens 300R, and is incident on the image forming region of the light modulation element 400R for red light. The green light G reflected by the dichroic mirror 210 is further reflected by the reflection mirror 220, passes through the field lens 300G, and is incident on the image forming region of the light modulation element 400G for green light. The blue light B reflected by the reflection mirror 250 enters the image forming region of the light modulation element 400B for blue light through the field lens 300B.

The light modulation element 400R, the light modulation element 400G, and the light modulation element 400B modulate the incident colored light according to the image information to form the image light corresponding to each color. Each of the light modulation element 400R, the light modulation element 400G, and the light modulation element 400B is composed of a liquid crystal panel. Although not shown, the polarizing plates on the incident side are arranged on the light incident side of the light modulation element 400R, the light modulation element 400G, and the light modulation element 400B, respectively. A polarizing plate on the emission side is arranged on the light emission side of the light modulation element 400R, the light modulation element 400G, and the light modulation element 400B, respectively.

The cross dichroic prism 500 synthesizes each image light emitted from the light modulation element 400R, the light modulation element 400G, and the light modulation element 400B to generate synthetic light, and forms a color image. The cross-dicroic prism 500 has a substantially square shape in a plan view in which four right-angled prisms are bonded together, and a dielectric multilayer film is provided at a substantially X-shaped interface in which the right-angled prisms are bonded to each other.

The projection optical device 600 magnifies and projects the synthetic light emitted from the cross dichroic prism 500 onto the screen SCR to form a color image.

Hereinafter, the configuration of the first light source device 101 will be described.
FIG. 2 is a schematic configuration diagram of the first light source device 101.
As shown in FIG. 2, the first light source device 101 includes a first light emitting unit 121, a first collimator optical system 122, an afocal optical system 123, a homogenizer optical system 124, a dichroic mirror 150, and pickup optics. It includes a system 127, a wavelength conversion element 110, a first integrator optical system 131, a polarization conversion element 132, and a superimposition optical system 133.

The first light emitting unit 121 has a plurality of first light emitting elements 121a. The plurality of first light emitting elements 121a are arranged in an array in a plane orthogonal to the optical axis. The number of the first light emitting elements 121a is not particularly limited. The first light emitting element 121a emits excitation light BL having an excitation wavelength band of, for example, 440 to 470 nm. That is, the excitation light BL is light in the blue wavelength band. The first light emitting element 121a is composed of a semiconductor laser light source that emits linearly polarized light.

In the present embodiment, the optical path of the main light beam emitted from the first light emitting element 121a in the center of the first light emitting unit 121 is defined as the optical axis ax2. Further, the optical path of the main light beam of the light emitted from the wavelength conversion element 110, which will be described later, is defined as the optical axis ax3. The optical axis ax2 and the optical axis ax3 are in the same plane and are orthogonal to each other.

On the optical axis ax2, the first light emitting unit 121, the first collimator optical system 122, the afocal optical system 123, the homogenizer optical system 124, and the dichroic mirror 150 are arranged side by side in this order. On the optical axis ax3, the wavelength conversion element 110, the pickup optical system 127, the dichroic mirror 150, the first integrator optical system 131, the polarization conversion element 132, and the superimposition optical system 133 are arranged side by side in this order.

The first collimator optical system 122 converts the excitation light BL emitted from each first light emitting element 121a of the first light emitting unit 121 into parallel light. The first collimator optical system 122 is composed of, for example, a plurality of collimator lenses 122a arranged in an array. One collimator lens 122a is arranged corresponding to one first light emitting element 121a. The excitation light BL converted into parallel light by the first collimator optical system 122 is incident on the afocal optical system 123.

The afocal optical system 123 converts the spot diameter of a luminous flux composed of a plurality of excitation lights BL. The afocal optical system 123 is composed of, for example, an afocal lens 123a made of a convex lens and an afocal lens 123b made of a concave lens. The excitation light BL that has passed through the afocal optical system 123 is incident on the homogenizer optical system 124.

The homogenizer optical system 124 converts the light intensity distribution of the excitation light BL into a uniform distribution, a so-called top hat distribution, in the illuminated region. The homogenizer optical system 124 is composed of, for example, a multi-lens array 124a and a multi-lens array 124b. The excitation light BL emitted from the homogenizer optical system 124 is incident on the dichroic mirror 150.

The dichroic mirror 150 has a wavelength selectivity that reflects a blue light component and transmits a yellow light component. That is, the dichroic mirror 150 has a property of reflecting the excitation light BL emitted from the first light emitting unit 121 and transmitting the fluorescent YL emitted from the wavelength conversion element 110 described later. The dichroic mirror 150 is arranged so as to form an angle of 45 ° with respect to the optical axis ax2 and the optical axis ax3. The excitation light BL incident on the dichroic mirror 150 is reflected by the dichroic mirror 150 and travels toward the pickup optical system 127.

The pickup optical system 127 condenses the excitation light BL toward the wavelength conversion layer 11 of the wavelength conversion element 110, and parallelizes the fluorescent YL emitted from the wavelength conversion layer 11. The pickup optical system 127 includes a pickup lens 127a and a pickup lens 127b.

The wavelength conversion element 110 includes a wavelength conversion layer 11, a support substrate 12 that supports the wavelength conversion layer 11, and a reflection layer 13 provided between the wavelength conversion layer 11 and the support substrate 12. The wavelength conversion layer 11 is composed of, for example, a sintered body in which YAG phosphor particles are sintered. The wavelength conversion element 110 converts the excitation light BL into fluorescent YL (first light in the first wavelength band) in a yellow wavelength band different from the excitation wavelength band. Fluorescent YL has a peak wavelength in the wavelength band of, for example, 500 to 700 nm.

The support substrate 12 is made of a metal material having excellent thermal conductivity, such as copper and aluminum. The reflective layer 13 is made of a metal material having high reflectance such as silver or aluminum or a dielectric multilayer film. Of the fluorescent YLs generated by the wavelength conversion layer 11, the fluorescent YLs traveling toward the support substrate 12 are reflected by the reflection layer 13 and emitted from the wavelength conversion layer 11 to the outside. The fluorescent YL emitted from the wavelength conversion element 110 proceeds toward the pickup optical system 127.

After being converted into parallel light by the pickup optical system 127, the fluorescent YL passes through the dichroic mirror 150 and is incident on the first integrator optical system 131. The first integrator optical system 131 divides the incident fluorescent YL into a plurality of luminous fluxes. The first integrator optical system 131 is composed of a first lens array 131a and a second lens array 131b. Each of the first lens array 131a and the second lens array 131b has a configuration in which a plurality of lenses are arranged in an array.

The fluorescent YL emitted from the first integrator optical system 131 is incident on the polarization conversion element 132. The polarization conversion element 132 converts the fluorescent YL into linearly polarized light having a predetermined polarization direction. The polarization conversion element 132 is composed of a polarization separation membrane, a retardation plate, and a mirror.

The fluorescent YL that has passed through the polarization conversion element 132 is incident on the superimposing lens 133a. The superimposing lens 133a superimposes a plurality of light fluxes emitted from the polarization conversion element 132 on the image forming region of the light modulation device to be illuminated. As a result, the fluorescent YL can uniformly illuminate the image forming region. The superimposition optical system 133 is composed of a first integrator optical system 131 including a first lens array 131a and a second lens array 131b, and a superimposition lens 133a.

Hereinafter, the configuration of the second light source device 102 will be described.
FIG. 3 is a schematic configuration diagram of the second light source device 102. FIG. 4 is a perspective view of a main part of the second light source device 102. In FIG. 4, among the second light source device 102, the light source unit 21, the diffusion element 22, the distance shortening unit 23, the first retardation plate 24, and the second retardation plate 25 are illustrated, and other components are illustrated. Omit.

As shown in FIG. 3, the second light source device 102 includes a light source unit 21, a diffusion element 22, a distance shortening unit 23, a first retardation plate 24, a second retardation plate 25, and a second collimator. It includes an optical system 26, a second integrator optical system 27, a polarization separating element 28, a third retardation plate 29, and a concave mirror 30.

The central axis of the blue luminous flux BH emitted from the light source unit 21 described later is defined as the optical axis ax4. The light source unit 21, the distance shortening unit 23, the diffusion element 22, the second collimator optical system 26, the second integrator optical system 27, the polarization separating element 28, the third retardation plate 29, and the concave mirror 30 are on the optical axis ax4. They are arranged in this order along.

As shown in FIG. 4, the light source unit 21 emits a first light source 31 that emits the first light L1, a second light source 32 that emits the second light L2, and a third light source L3 that emits the third light L3. It has a light source 33 and a fourth light source 34 that emits a fourth light L4. Each of the first light source 31, the second light source 32, the third light source 33, and the fourth light source 34 is composed of a CAN package type laser light source including a second light emitting element 35 and an imaging lens 36. Each of the first light source 31, the second light source 32, the third light source 33, and the fourth light source 34 is composed of the same laser light source. Therefore, the light source unit 21 emits a blue luminous flux BH including the first light L1, the second light L2, the third light L3, and the fourth light L4. In FIG. 4, the package containing the second light emitting element 35 and the imaging lens 36 is not shown.

The second light emitting element 35 is composed of a semiconductor laser element. The second light emitting element 35 emits blue light B having a wavelength band of, for example, 440 to 470 nm. The wavelength band of the second light emitting element 35 may be the same as or different from the wavelength band of the first light emitting element 121a. Further, the blue light B is P-polarized light with respect to the polarization separating element 28 described later. The second light emitting element 35 has a chip-like shape as a whole, and has a rectangular light emitting surface when viewed from the emission direction of blue light B. The imaging lens 36 collects the light emitted from the second light emitting element 35 toward the diffusing element 22, and forms a light source image of the second light emitting element 35 on the diffusing element 22.

The diffusing element 22 diffuses the blue luminous flux BH emitted from the light source unit 21. The diffusion element 22 is, for example, a transmission type diffusion element having a light incident surface 22a and a light emitting surface 22b perpendicular to the optical axis ax4 and having a concavo-convex structure on either one of the light incident surface 22a and the light emitting surface 22b. It is composed of. The diffusing element 22 has a property of diffusing the polarization state of the blue luminous flux BH without disturbing it by optimizing the shape and dimensions of the concave-convex structure. The diffusing element 22 has a property of diffusing the blue luminous flux BH with a relatively narrow diffusing angle.

The distance shortening unit 23 is provided on the optical path of the blue luminous flux BH between the light source unit 21 and the diffusing element 22. The distance shortening unit 23 turns back the optical path of the blue luminous flux BH emitted from the light source unit 21 to secure a substantial optical path length between the light source unit 21 and the diffusion element 22, while ensuring the actual optical path length between the light source unit 21 and the diffusion element 22. Reduce the physical distance to 22.

The distance shortening unit 23 has a first optical path changing element 41 that folds back the optical path of the first light L1, a second optical path changing element 42 that folds back the optical path of the second light L2, and a third optical path that folds back the optical path of the third light L3. It has a three optical path changing element 43 and a fourth optical path changing element 44 that folds back the optical path of the fourth optical path L4. The first optical path changing element 41 is provided on the optical path of the first light L1 between the first light source 31 and the diffusing element 22. The second optical path changing element 42 is provided on the optical path of the second light L2 between the second light source 32 and the diffusing element 22. The third optical path changing element 43 is provided on the optical path of the third light L3 between the third light source 33 and the diffusing element 22. The fourth optical path changing element 44 is provided on the optical path of the fourth light L4 between the fourth light source 34 and the diffusing element 22.

The first optical path changing element 41 includes a first front-stage mirror 411 and a first rear-stage mirror 412. The first front-stage mirror 411 reflects the first light L1 emitted from the first light source 31 toward the first rear-stage mirror 412. The first rear-stage mirror 412 reflects the first light L1 reflected by the first front-stage mirror 411 toward the diffusion element 22.

The second optical path changing element 42 includes a second front-stage mirror 421 and a second rear-stage mirror 422. The second front-stage mirror 421 reflects the second light L2 emitted from the second light source 32 toward the second rear-stage mirror 422. The second rear-stage mirror 422 reflects the second light L2 reflected by the second front-stage mirror 421 toward the diffusion element 22.

The third optical path changing element 43 includes a third front-stage mirror 431 and a third rear-stage mirror 432. The third front-stage mirror 431 reflects the third light L3 emitted from the third light source 33 toward the third rear-stage mirror 432. The third rear-stage mirror 432 reflects the third light L3 reflected by the third front-stage mirror 431 toward the diffusion element 22.

The fourth optical path changing element 44 includes a fourth front-stage mirror 441 and a fourth rear-stage mirror 442. The fourth front-stage mirror 441 reflects the fourth light L4 emitted from the fourth light source 34 toward the fourth rear-stage mirror 442. The fourth rear-stage mirror 442 reflects the fourth light L4 reflected by the fourth front-stage mirror 441 toward the diffusion element 22.

All the mirrors 411, 421, 421, 422, 431, 432, 441, 442 constituting each optical path changing element 41, 42, 43, 44 have a rectangular outer shape. These mirrors do not necessarily have a rectangular outer shape, and may have, for example, a square outer shape. However, each light L1, L2, L3, L4 having a rectangular cross section emitted from the rectangular light emitting surface of the second light emitting element 35 is each mirror 411, 421, 421, 422, 431, 432, 441, 442. Therefore, when the shape of the mirror is rectangular according to the light, the area of the mirror is smaller than that when the shape of the mirror is square, and the mirror can be miniaturized.

The first retardation plate 24 is provided on the optical path of the first light L1 between the first light source 31 and the first front-stage mirror 411. The first retardation plate 24 is composed of a 1/2 wavelength plate with respect to the wavelength band of the first light L1. The second retardation plate 25 is provided on the optical path of the third light L3 between the third light source 33 and the third front-stage mirror 431. The second retardation plate 25 is composed of a 1/2 wavelength plate with respect to the wavelength band of the third light L3. The first retardation plate 24 and the second retardation plate 25 do not necessarily have to be 1/2 wavelength plates, but are preferably 1/2 wavelength plates.

The second collimator optical system 26 parallelizes the blue luminous flux BH emitted from the diffusing element 22. The second collimator optical system 26 includes a first collimator lens 26a and a second collimator lens 26b.

The second integrator optical system 27 is composed of a double-sided lens array in which a plurality of lenses are formed on two surfaces of a base material. As a result, the physical optical path length can be shortened as compared with the case where an integrator optical system including two lens arrays is used, and the second light source device 102 can be miniaturized.

The polarization separating element 28 reflects the S polarization component and transmits the P polarization component. Since the blue luminous flux BH emitted from the second integrator optical system 27 is P-polarized light in which the polarization direction is maintained immediately after being emitted from the light source unit 21, it passes through the polarization separating element 28 and passes through the polarization separating element 28, and the third retardation plate 29 Proceed towards.

The third retardation plate 29 is composed of a quarter wave plate with respect to the wavelength band of the blue luminous flux BH. Therefore, the P-polarized blue light flux BH is converted into, for example, a counterclockwise circularly polarized blue light flux BH by passing through the third retardation plate 29, and proceeds toward the concave mirror 30.

The concave mirror 30 is provided on the optical path of the blue luminous flux BH between the diffusion element 22 and the light modulation element 400B. The concave mirror 30 has a spherical reflecting surface 30a, reflects the blue light flux BH emitted from the diffusion element 22 and guides it to the light modulation element 400B, and focuses the blue light flux BH in the image forming region of the light modulation element 400B. Let me.

The counterclockwise circularly polarized blue light flux BH is reflected by the concave mirror 30 and converted into a clockwise circularly polarized blue light flux BH. The clockwise circularly polarized blue light flux BH is converted into S-polarized blue light flux BH by passing through the third retardation plate 29 again, reflected by the polarization separating element 28, and emitted from the second light source device 102. ..

A light source device including a transmission type diffuser element, such as the second light source device 102 of the present embodiment, has a relatively narrow diffusion angle characteristic for the purpose of suppressing total internal reflection and suppressing a decrease in light transmittance. A diffuser is used. In this case, in order to compensate for the narrow diffusion angle characteristic of the diffusion element, a light source device having a configuration in which light from a light source is incident at a large incident angle can be considered.

Here, the present inventor assumed the light source device of the first comparative example shown below, and simulated the illuminance distribution of the luminous flux at a position separated from the diffusing element by a predetermined distance.
FIG. 9 is a schematic configuration diagram of the light source device of the first comparative example.
As shown in FIG. 9, the light source device 80 of the first comparative example includes four light sources 81 arranged in a square shape when viewed from the direction of the optical axis ax4, and a diffusion element 82. The diffusion element 82 has a narrow diffusion angle characteristic. Further, each light source 81 is arranged at an angle with respect to the optical axis ax4 so that the incident angle θ1 of the light with respect to the diffusion element 82 is, for example, 30 °.

FIG. 10 is a simulation result showing the illuminance distribution of the luminous flux emitted from the diffusion element 82. In FIG. 10, a region that looks whitish is a region where the illuminance is relatively high, and a region that looks blackish is a region where the illuminance is relatively low.
As shown in FIG. 10, a region with high illuminance appears near the four corners of the square, and an illuminance distribution in which the illuminance in the central portion near the optical axis ax4 is significantly lower than the illuminance in the corners can be obtained. I found out.

Next, the present inventor assumed the light source device of the second comparative example shown below, and simulated the illuminance distribution of the luminous flux at a position separated from the diffusing element by a predetermined distance.
FIG. 11 is a schematic configuration diagram of the light source device of the second comparative example.
As shown in FIG. 11, the light source device 90 of the second comparative example includes four light sources 91 arranged in a square shape when viewed from the direction of the optical axis ax4, and a diffusion element 92. The diffusion element 92 has a narrow diffusion angle characteristic. Further, each light source 91 is arranged at an angle with respect to the optical axis ax4 so that the incident angle θ2 of the light with respect to the diffusion element 92 is, for example, 15 °. Therefore, the incident angle θ2 in the second comparative example is smaller than the incident angle θ1 in the first comparative example.

FIG. 12 is a simulation result showing the illuminance distribution of the luminous flux emitted from the diffusing element 92. In FIG. 12, a region that looks whitish is a region where the illuminance is relatively high, and a region that looks blackish is a region where the illuminance is relatively low.
As shown in FIG. 12, the illuminance in the central portion near the optical axis ax4 is higher than the illuminance in the corner portion, and there is a problem of illuminance decrease in the central portion of the region when the light source device 80 of the first comparative example is used. Turned out to be improved.

However, the light source device 90 of the second comparative example has the following problems.
In the light source device 80 of the first comparative example, since the incident angle θ1 of light with respect to the diffusion element 82 is large, the positions of the light sources 81 are separated from the optical axis ax4, and the distance between the light sources 81 is wide. Therefore, even if each light source 81 is arranged at a position close to the diffusion element 82, the packages of adjacent light sources 81 are unlikely to interfere with each other. On the other hand, in the light source device 90 of the second comparative example, since the incident angle θ2 of the light with respect to the diffusion element 92 is small, the position of each light source 91 is close to the optical axis ax4, and the distance between the light sources 91 is narrow. Therefore, if each light source 91 is arranged at a position close to the diffusion element 92, the packages of adjacent light sources 91 interfere with each other, and it is difficult to arrange each light source 91 at a predetermined position. Therefore, each light source 91 must be arranged at a position far from the diffusion element 92 so that the packages of adjacent light sources 91 do not interfere with each other. In this case, there is a problem that the light source device 90 becomes large.

Therefore, as shown in FIG. 3, the present inventor provides the distance shortening unit 23 and turns back the optical paths of the lights L1, L2, L3, and L4 emitted from the light sources 31, 32, 33, and 34. We have come up with the idea that the physical distance between the light source unit 21 and the diffuser 22 can be shortened while maintaining a substantial optical path length between each of the light sources 31, 32, 33, 34 and the diffuser 22. However, in order to secure the space of the folded optical path, it is necessary to shift the two mirrors constituting the optical path changing elements 41, 42, 43, 44 with respect to the optical axes of the light sources 31, 32, 33, 34. is there. Therefore, if one light source and one optical path changing element are considered as one set and the set is rotated around the optical axis of each light source, one optical path changing element 41, 42, 43, depending on the rotation angle, It was found that the mirror of 44 and the mirror of other optical path changing elements 41, 42, 43, 44 may interfere with each other.

Of the two mirrors that make up each optical path changing element 41, 42, 43, 44, the front-stage mirror is arranged at a position closer to the optical axis ax4 than the rear-stage mirror depending on the angle, and the front-stage mirrors are arranged with each other. There is a high possibility that interference will occur. Therefore, as a result of examining the rotation angle of each set including the light source and the optical path changing element, the present inventor has as shown in FIG. 4, that the front-stage mirror 411 and the third optical path changing element 43 of the first optical path changing element 41 Arrangement in which the longitudinal direction of the front-stage mirror 431 faces the first direction, and the longitudinal direction of the front-stage mirror 421 of the second optical path changing element 42 and the front-stage mirror 441 of the fourth optical path changing element 44 faces the second direction orthogonal to the first direction. Should be adopted.

When the arrangement of each front-stage mirror is as described above, the orientation of the second light emitting element 35 of each light source is the optical axis in the order of the first light source 31, the second light source 32, the third light source 33, and the fourth light source 34. It is in a state of being rotated by 90 ° about ax4. According to this arrangement, the front mirrors 411, 421, 431, 441 of each optical path changing element 41, 42, 43, 44 are arranged outside the diffusion element 22 and at the position farthest from the diffusion element 22. The possibility that the front mirrors of the optical path changing elements 41, 42, 43, and 44 interfere with each other can be minimized.

When the above arrangement is adopted, the arrangement of the four light source images formed on the diffusion element 22 is as shown in FIG. That is, as shown in FIG. 5, the first light source 31 forms the first light source image S1 at the first position on the diffusion element 22, and the second light source 32 forms the second light source image S2 on the diffusion element 22. The third light source 33 is formed at a second position different from the first position, and the third light source image S3 is formed at a third position different from the first position and the second position on the diffusion element 22, and the fourth light source is formed. 34 forms the fourth light source image S4 at a fourth position different from the first position, the second position, and the third position on the diffusion element 22. The longitudinal direction of the first light source image S1 and the longitudinal direction of the third light source image S3 are along the first direction on the diffusion element 22, and the longitudinal direction of the second light source image S2 and the longitudinal direction of the fourth light source image S4 are diffused. Along a second direction orthogonal to the first direction on the element 22.

Further, in the first light source image S1, the second light source image S2, the third light source image S3, and the fourth light source image S4, one short side of the first light source image S1 is the second light source image S2 on the diffusion element 22. One short side of the second light source image S2 faces one long side of the third light source image S3, and one short side of the third light source image S3 faces the fourth light source image S4. Is arranged so that one short side of the fourth light source image S4 faces one long side of the first light source image S1.

Generally, the light emitted from the semiconductor laser device is linearly polarized light having a polarization direction parallel to the longitudinal direction of the light emitting surface. Therefore, in the arrangement of the light source images S1, S2, S3, and S4 described above, if the first retardation plate 24 and the second retardation plate 25 are not present, the luminous flux in which light having different polarization directions is mixed is diffused. It is emitted from the element 22, and the light flux is completely transmitted through the polarization separating element 28 in the subsequent stage, and cannot be guided to the concave mirror 30, so that the light utilization efficiency is lowered.

Therefore, in the second light source device 102 of the present embodiment, a first retardation plate 24 made of a 1/2 wavelength plate is provided on the optical path of the first light L1 between the first light source 31 and the diffusion element 22. Since the second retardation plate 25 made of a 1/2 wavelength plate is provided on the optical path of the third light L3 between the third light source 33 and the diffusion element 22, a solid line arrow is shown in FIG. As shown, the polarization directions of the first light L1 and the third light L3 can be rotated by 90 ° to match the polarization directions of the second light L2 and the fourth light L4. As a result, a luminous flux in which all the light is aligned with the P-polarized light with respect to the polarization separating element 28 is emitted from the diffusion element 22. As a result, all of the luminous flux can be guided to the concave mirror 30, and the light utilization efficiency can be ensured. Instead of the configuration of the present embodiment, the fourth light L4 on the optical path of the second light L2 between the second light source 32 and the diffusing element 22 and between the fourth light source 34 and the diffusing element 22. A retardation plate may be provided on the optical path of the light source.

The present inventor has simulated the illuminance distribution of the blue luminous flux BH at a position separated from the diffusion element 22 by a predetermined distance with respect to the second light source device 102 of the present embodiment.
FIG. 6 is a simulation result showing the illuminance distribution of the blue luminous flux BH emitted from the diffusing element 22. In FIG. 6, the region that looks whitish is a region where the illuminance is relatively high, and the region that looks blackish is a region where the illuminance is relatively low.
As shown in FIG. 6, the illuminance in the central portion near the optical axis ax4 is higher than the illuminance in the corner portion, and the problem of illuminance reduction in the central portion of the region due to the light source device of the first comparative example is improved. I found out. Further, since the shape of the region occupying the same illuminance is generally rectangular and the outer shape of the second integrator optical system 27 located behind the diffusing element 22 is also rectangular, the blue luminous flux BH emitted from the diffusing element 22 is transferred. It can be efficiently incident on the second integrator optical system 27.

As described above, according to the present embodiment, it is possible to provide the second light source device 102, which is less likely to reduce the illuminance in the central portion of the illuminated area, has a substantially uniform illuminance distribution, and is compact. it can.

Further, by adopting the second light source device 102 of the present embodiment, it is possible to provide a compact projector 1 with less brightness unevenness and color unevenness of the projected image. In particular, in the case of the present embodiment, since the optical path of the blue luminous flux BH emitted from the diffusion element 22 is folded back by the concave mirror 30, the physical distance in the subsequent stage can be shortened as compared with the diffusion element 22, which contributes to the miniaturization of the projector 1. can do.

[Modification example]
In the above embodiment, the case where the plurality of light source images S1, S2, S3, and S4 on the diffusion element 22 are arranged as shown in FIG. 5 has been mentioned, but the plurality of light source images S1, S2 on the diffusion element 22 have been described. , S3 and S4 do not necessarily have to be arranged as shown in FIG.

FIG. 7 is a diagram showing the arrangement of a plurality of light source images on the diffuser element by the second light source device of this modification.
As shown in FIG. 7, in the second light source device of the present modification, the longitudinal direction of the first light source image S1 and the longitudinal direction of the third light source image S3 are along the first direction on the diffuser 22 and the second light source. The longitudinal direction of the image S2 and the longitudinal direction of the fourth light source image S4 are along a second direction orthogonal to the first direction on the diffuser 22. This feature is the same as in the above embodiment.

However, as a feature different from the above embodiment, the first light source image S1, the second light source image S2, the third light source image S3, and the fourth light source image S4 are all the light source images S1 on the diffusion element 22. The short sides of S2, S3, and S4 are arranged so as to face the center of the diffusion element 22.

In the case of this modification as well, as in the above embodiment, the third light on the optical path of the first light L1 between the first light source 31 and the diffusing element 22 and between the third light source 33 and the diffusing element 22. Phase difference on the optical path of L3 or on the optical path of the second light L2 between the second light source 32 and the diffusing element 22 and on the optical path of the fourth light L4 between the fourth light source 34 and the diffusing element 22. If a plate is provided, a blue light source BH containing light whose polarization directions are aligned with each other can be emitted from the diffusing element 22. Although the illustration of the light source device is omitted, in the case of this modification as well, since the front-stage mirrors of the optical path changing elements are arranged at positions outside the diffusion element 22, there is a possibility that the front-stage mirrors of the optical path changing elements may interfere with each other. Can be reduced.

The present inventor simulated the illuminance distribution of the blue luminous flux BH at a position separated from the diffusing element 22 by a predetermined distance with respect to the light source device of the present modification.
FIG. 8 is a simulation result showing the illuminance distribution of the blue luminous flux BH emitted from the diffusing element 22. In FIG. 8, the region that looks whitish is a region where the illuminance is relatively high, and the region that looks blackish is a region where the illuminance is relatively low.
As shown in FIG. 8, the illuminance in the central portion near the optical axis is higher than the illuminance in the corner portion, and it is found that the problem of the illuminance decrease in the central portion due to the light source device of the first comparative example is improved. It was.

[Second Embodiment]
Hereinafter, the second embodiment of the present application will be described with reference to FIG.
The configuration of the projector and the light source device of the second embodiment is substantially the same as that of the first embodiment. Therefore, detailed description of the projector and the light source device will be omitted, and only different parts will be described.
FIG. 13 is a schematic configuration diagram of the second light source device of the second embodiment.
In FIG. 13, components common to the drawings used in the first embodiment are designated by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 13, the second light source device 104 of the present embodiment includes a light source unit 21, a diffusion element 22, a distance shortening unit 23, a first retardation plate (not shown), and a second retardation plate. It includes 25, a second collimator optical system 26, a second integrator optical system 27, a condensing lens 46, and a mirror 47. The configurations of the light source unit 21, the diffusion element 22, the distance shortening unit 23, the first retardation plate, the second retardation plate 25, the second collimator optical system 26, and the second integrator optical system 27 are the same as those of the first embodiment. The same is true.

The condenser lens 46 is composed of a convex lens. The mirror 47 is arranged so as to form an angle of 45 ° with the optical axis ax4. In the present embodiment, the blue luminous flux BH emitted from the second integrator optical system 27 is focused by the condenser lens 46, reflected by the mirror 47, and guided to the light modulation element 400B.

Also in the present embodiment, there is little risk of illuminance decrease in the central portion of the illuminated area, a small light source device can be provided, brightness unevenness and color unevenness of the projected image are small, and a small projector can be provided. 1 The same effect as that of the embodiment can be obtained.

The technical scope of the present application is not limited to the above-described embodiment, and various changes can be made without departing from the spirit of the present application.
For example, in the above embodiment, an example of a light source device provided with a fixed wavelength conversion element is given as the first light source device, but instead of this configuration, a wavelength conversion element made rotatable by a drive source such as a motor. A light source device comprising the above may be used. Similarly, in the above embodiment, an example of a light source device provided with a fixed diffusion element is given as the second light source device, but instead of this configuration, a diffusion element made rotatable by a drive source such as a motor or the like is given. A light source device comprising the above may be used.

In addition, the specific description of the shape, number, arrangement, material, and the like of each component of the projector is not limited to the above embodiment, and can be changed as appropriate. Further, in the above embodiment, an example in which the present application is applied to a projector using a liquid crystal light bulb is shown, but the present invention is not limited to this. The present application may be applied to a projector using a digital micromirror device as an optical modulation device.

1 ... Projector, 21 ... Light source unit, 22 ... Diffusing element, 23 ... Distance shortening unit, 24 ... First phase difference plate, 25 ... Second phase difference plate, 31 ... First light source, 32 ... Second light source, 33 ... 3rd light source, 34 ... 4th light source, 35 ... 2nd light emitting element (laser element), 36 ... imaging lens, 41 ... 1st optical path changing element, 42 ... 2nd optical path changing element, 43 ... 3rd optical path changing element , 44 ... 4th optical path changing element, 102, 104 ... 2nd light source device (light source device), 400 ... Optical modulator, 411 ... 1st front mirror, 412 ... 1st rear mirror, 421 ... 2nd front mirror, 422 ... 2nd rear stage mirror, 431 ... 3rd front stage mirror, 432 ... 3rd rear stage mirror, 441 ... 4th front stage mirror, 442 ... 4th rear stage mirror, 600 ... Projection optical device, BH ... Blue light source (light source), L1 ... First light, L2 ... second light, L3 ... third light, L4 ... fourth light.

Claims (5)

The first light source that emits the first light and
A second light source that emits a second light,
A third light source that emits a third light,
A fourth light source that emits a fourth light,
A diffusing element that diffuses the first light, the second light, the third light, and the fourth light.
A first optical path changing element provided on the optical path of the first light between the first light source and the diffusing element and folding back the optical path of the first light.
A second optical path changing element provided on the optical path of the second light between the second light source and the diffusing element and folding back the optical path of the second light.
A third optical path changing element provided on the optical path of the third light between the third light source and the diffusing element and folding back the optical path of the third light.
A fourth optical path changing element provided on the optical path of the fourth light between the fourth light source and the diffusing element and folding back the optical path of the fourth light.
With
The first light source forms a first light source image at a first position on the diffusion element.
The second light source forms the second light source image at a second position different from the first position on the diffusion element.
The third light source forms a third light source image at a third position different from the first position and the second position on the diffusion element.
The fourth light source forms a fourth light source image at a fourth position different from the first position, the second position, and the third position on the diffusion element.
The longitudinal direction of the first light source image and the longitudinal direction of the third light source image are along the first direction on the diffusion element.
The longitudinal direction of the second light source image and the longitudinal direction of the fourth light source image are along a second direction orthogonal to the first direction on the diffusion element.
A light source device in which a first retardation plate is provided on the optical path of the first light, and a second retardation plate is provided on the optical path of the third light. The first optical path changing element includes a first front-stage mirror that reflects the first light emitted from the first light source and a first rear-stage mirror that reflects the first light reflected by the first front-stage mirror. And have
The second optical path changing element includes a second front-stage mirror that reflects the second light emitted from the second light source and a second rear-stage mirror that reflects the second light reflected by the second front-stage mirror. And have
The third optical path changing element includes a third front-stage mirror that reflects the third light emitted from the third light source, and a third rear-stage mirror that reflects the third light reflected by the third front-stage mirror. And have
The fourth optical path changing element includes a fourth front-stage mirror that reflects the fourth light emitted from the fourth light source and a fourth rear-stage mirror that reflects the fourth light reflected by the fourth front-stage mirror. The light source device according to claim 1, further comprising. In the first light source image, the second light source image, the third light source image, and the fourth light source image, one short side of the first light source image is one of the second light source images on the diffusion element. One short side of the second light source image faces one long side of the third light source image, and one short side of the third light source image faces one long side of the third light source image. The light source according to claim 1 or 2, which is arranged so as to face one long side and one short side of the fourth light source image faces one long side of the first light source image. apparatus. The first phase difference plate is composed of a 1/2 wave plate with respect to the wavelength band of the first light.
The light source device according to any one of claims 1 to 3, wherein the second retardation plate is composed of a 1/2 wave plate for the wavelength band of the third light. The light source device according to any one of claims 1 to 4.
An optical modulation device that modulates the light from the light source device according to image information,
A projection optical device that projects light modulated by the light modulation device, and
Equipped with a projector.

Images