JP2021086006A - Light source device and projector - Google Patents

Abstract

To provide a light source device that can efficiently illuminate an illumination target area.SOLUTION: A light source device of the present invention comprises: a light emitting device that emits light; and an angle conversion element that changes a light distribution angle of light emitted from the light emitting device. The angle conversion element has a first angle conversion unit and a second angle conversion unit. A distance from an optical axis of the angle conversion element to the second angle conversion unit is longer than a distance from the optical axis to the first angle conversion unit, and refractive power of the second angle conversion unit is smaller than refractive power of the first angle conversion unit.SELECTED DRAWING: Figure 5

Description

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

A light emitting device using a photonic crystal has been conventionally known. For example, Patent Document 1 below includes a two-dimensional photonic crystal and a one-dimensional photonic crystal, and emits light propagating in the in-plane direction of the two-dimensional photonic crystal to the photonic band edge of the one-dimensional photonic crystal. A surface emitting laser having a structure for reflecting light is disclosed.

Japanese Unexamined Patent Publication No. 2009-43918

It is being studied to construct a small projector by using the surface light source as described above. In this case, if the surface light source can be arranged in the immediate vicinity of the light modulation device, the light modulation device can be efficiently illuminated. However, in order to provide a space for cooling the optical modulation device or a space for arranging various optical elements such as a lens, it is necessary to arrange the surface light source and the optical modulation device at a predetermined distance. is there. For example, when the optical modulation device is composed of a liquid crystal display element, a space for arranging the polarizing element is required between the surface light source and the liquid crystal display element.

Assuming that the luminous flux emitted from the surface light source is not a parallel light flux but a divergent light flux, the diameter and outer shape of the light flux change as the distance from the surface light source increases. Therefore, when the light modulation device is arranged at a position away from the surface light source, the outer shape of the light flux incident on the light modulation device is different from the outer shape of the light flux immediately after being emitted from the surface light source. The shape of the image forming region of the optical modulator is often rectangular, and even if the shape of the light emitting region of the surface light source is made rectangular accordingly, the outer shape of the luminous flux approaches a circle as the distance from the surface light source increases. Deforms in the direction. As a result, there is a problem that the outer shape of the light beam does not match the shape of the image forming region of the light modulation apparatus, and the image forming region cannot be efficiently illuminated.

In order to solve the above problems, the light source device of one aspect of the present invention includes a light emitting device that emits light and an angle conversion element that changes the light distribution angle of the light emitted from the light emitting device. The angle conversion element includes a first angle conversion unit and a second angle conversion unit, and the distance from the optical axis of the angle conversion element to the second angle conversion unit is the distance from the optical axis to the second angle conversion unit. It is longer than the distance to the one-angle conversion unit, and the refractive force of the second angle conversion unit is smaller than the refractive force of the first angle conversion unit.

In the light source device of one aspect of the present invention, the light distribution angle of the light emitted from the second angle conversion unit may be smaller than the light distribution angle of the light emitted from the first angle conversion unit.

In the light source device of one aspect of the present invention, the first angle conversion unit emits a first incident end face on which the light emitted from the light emitting device is incident and a first emission of light having a changed light distribution angle. The first incident end face and at least one of the first ejection end faces have a first concavo-convex structure in which concave portions and convex portions are periodically provided, and the second angle conversion portion has an end face. It has a second incident end face on which the light emitted from the light emitting device is incident, and a second emission end face on which the light whose light distribution angle is changed is emitted. At least one of the above may have a second uneven structure in which the concave portion and the convex portion are periodically provided.

In the light source device according to one aspect of the present invention, the pitch of the second concavo-convex structure may be longer than the pitch of the first concavo-convex structure.

In the light source device of one aspect of the present invention, the depth of the second uneven structure may be shallower than the depth of the first uneven structure.

In the light source device of one aspect of the present invention, the first angle conversion unit has a first low refractive index unit having a first refractive index and a first high refractive index having a second refractive index higher than the first refractive index. The second refractive index conversion unit has a first refractive index periodic structure in which the refractive index unit is periodically provided, and the second angle conversion unit is based on the second low refractive index unit having the third refractive index and the third refractive index. It may have a second refractive index periodic structure in which a second high refractive index portion having a high fourth refractive index and a second high refractive index portion are periodically provided.

In the light source device of one aspect of the present invention, the pitch of the second refractive index periodic structure may be longer than the pitch of the first refractive index periodic structure.

In the light source device of one aspect of the present invention, the difference in refractive index between the first refractive index and the second refractive index of the second refractive index periodic structure is the third refractive index of the first refractive index periodic structure. It may be smaller than the difference in refractive index between the above and the fourth refractive index.

In the light source device of one aspect of the present invention, the angle conversion element may further include an angle non-conversion unit having no refractive power. In that case, it is desirable that the distance from the optical axis to the angle non-conversion unit is longer than the distance from the optical axis to the second angle conversion unit.

In the light source device of one aspect of the present invention, the light emitting device includes a base material and a light emitting region provided on the first surface of the base material, and the light emitting region is a photonic crystal having a periodic structure. It may have a structure.

In the light source device of one aspect of the present invention, the light emitting region may have a plurality of resonance portions.

The projector according to one aspect of the present invention includes a light source device according to one aspect of the present invention, an optical modulator that modulates light emitted from the light source device according to image information to generate image light, and the light. A projection optical device for projecting image light emitted from a modulation device is provided.

The projector of one aspect of the present invention may further include a light guide provided between the light source device and the light modulation device.

It is a schematic block diagram of the projector of 1st Embodiment. It is a top view of the light emitting element of 1st Embodiment. It is sectional drawing of the light emitting element along the line III-III of FIG. It is a figure which shows the light distribution angle of the light emitted from a light emitting region. It is a figure which shows the light distribution angle of the light emitted from the position which is different from each other in an angle conversion element. It is sectional drawing of the angle conversion element of 1st configuration example. It is sectional drawing of the angle conversion element of the 2nd configuration example. It is a figure which shows the position where the light emitted from a plurality of angle conversion units reaches the image formation region of an optical modulation apparatus. It is a figure which shows the planar shape and intensity distribution of a luminous flux. It is a figure which shows the planar shape and the intensity distribution of the light flux in the light emitting device of the comparative example. It is a figure which shows the relationship between the distance from the center of an injection region, and the refractive power of an angle conversion element. It is a top view of the light emitting element of the 2nd Embodiment. It is a schematic block diagram of the projector of 3rd Embodiment. It is a perspective view which shows the 1st example of a light guide body. It is a perspective view which shows the 2nd example of a light guide body.

[First Embodiment]
Hereinafter, the first embodiment of the present invention will be described with reference to FIGS. 1 to 10.
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 10 of the present embodiment is a projection type image display device that projects an image on a screen 11. The projector 10 includes a light source device 15, an optical modulation device 13, and a projection optical device 14. The light source device 15 includes a light emitting device 12 and an angle conversion element 19. The configuration of the light emitting device 12 and the angle conversion element 19 will be described in detail later.

Hereinafter, the optical axis that coincides with the normal line passing through the center of the light emitting region 12R in the light emitting device 12 and through which the main light beam of the luminous flux L emitted from the light emitting region 12R passes is referred to as an optical axis AX1. Hereinafter, the configuration of each part will be described using the XYZ Cartesian coordinate system. The axis parallel to the long side of the light emitting region 12R whose plane shape is rectangular when viewed from the direction of the optical axis AX1 is defined as the X axis, and the light emitting region is short. The axis parallel to the side is the Y axis, and the axis perpendicular to the X axis and the Y axis is the Z axis. The Z axis and the optical axis AX1 are parallel.

The light modulation device 13 modulates the luminous flux L emitted from the light source device 15 according to the image information to generate image light. The optical modulation device 13 includes an incident side polarizing plate 16, a liquid crystal display element 17, and an emitting side polarizing plate 18. When viewed from the Z-axis direction, the planar shape of the image forming region 17R of the liquid crystal display element 17 is rectangular. Further, as described above, the planar shape of the light emitting region 12R of the light emitting device 12 is rectangular, and the planar shape of the image forming region 17R and the planar shape of the light emitting region 12R are substantially similar figures. The area of the light emitting region 12R is the same as the area of the image forming region 17R or slightly larger than the area of the image forming region 17R.

The projection optical device 14 projects the image light emitted from the light modulation device 13 onto a projected surface such as a screen 11. The projection optical device 14 is composed of one or a plurality of projection lenses.

Hereinafter, the light emitting device 12 will be described.
As shown in FIG. 1, the light emitting device 12 includes a light emitting element 20 and a heat sink 21. The light emitting element 20 has a first surface 20a and a second surface 20b, and emits a luminous flux L from the first surface 20a. The heat sink 21 is provided on the second surface 20b of the light emitting element 20 in order to release the heat generated by the light emitting element 20.

FIG. 2 is a plan view showing a schematic configuration of the light emitting element 20. FIG. 3 is a cross-sectional view of the light emitting element 20 along the line III-III of FIG. In FIG. 2, only a part of the photonic crystal structure 57 in the light emitting region 12R is shown, and the other photonic crystal structure 57 is omitted in order to make the drawing easier to see.

As shown in FIG. 3, the light emitting element 20 includes a substrate 50 (base material), a laminate 51, a first electrode 52, and a second electrode 53. The laminate 51 has a reflective layer 55, a buffer layer 56, a photonic crystal structure 57, and a third semiconductor layer 58.

The substrate 50 is composed of, for example, a silicon (Si) substrate, a gallium nitride (GaN) substrate, a sapphire substrate, or the like.

The reflective layer 55 is provided on the substrate 50. The reflective layer 55 is composed of, for example, a DBR (distribution Bragg reflector) layer. The reflective layer 55 is composed of, for example, a laminated body in which AlGaN layers and GaN layers are alternately laminated, a laminated body in which AlInN layers and GaN layers are alternately laminated, and the like. The reflective layer 55 reflects the light generated in the light emitting layer 66, which will be described later, of the photonic crystal structure 57 toward the second electrode 53.

In the present specification, in the Z-axis direction, which is the stacking direction of the laminated body 51, when the light emitting layer 66 is used as a reference, the direction from the light emitting layer 66 toward the second semiconductor layer 67 is "upward", and the light emitting layer 66 to the second 1 The direction toward the semiconductor layer 65 will be described as "downward". Further, the "lamination direction of the laminated body 51" is a direction in which the first semiconductor layer 65 and the light emitting layer 66 face each other, and may be simply referred to as a "lamination direction" below.

The buffer layer 56 is provided on the reflective layer 55. The buffer layer 56 is made of a semiconductor material, and is composed of, for example, an n-type GaN layer doped with Si. In the example of FIG. 3, a mask layer 60 for growing a film forming the columnar portion 62, which will be described later, is provided on the buffer layer 56 in the manufacturing process of the light emitting element 20. The mask layer 60 is composed of, for example, a silicon oxide layer, a silicon nitride layer, or the like.

The photonic crystal structure 57 is a columnar structure provided on the buffer layer 56. The photonic crystal structure 57 has a plurality of columnar portions 62 and a plurality of light propagation layers 63. The photonic crystal structure 57 can exhibit the effect of the photonic crystal, and the light emitted by the light emitting layer 66 is confined in the in-plane direction of the substrate 50 and emitted in the stacking direction. The "in-plane direction of the substrate 50" is a direction along a plane orthogonal to the stacking direction.

The planar shape of the photonic crystal structure 57 is a polygon, a circle, an ellipse, or the like. In the present embodiment, as shown in FIG. 2, the planar shape of the photonic crystal structure 57 is a regular hexagon. The diameter of the photonic crystal structure 57 is on the order of nm, and specifically, it is, for example, 10 nm or more and 500 nm or less. As shown in FIG. 3, the columnar portion 62 is a nanostructure constituting the photonic crystal structure 57. The dimension of the photonic crystal structure 57 in the stacking direction, that is, the height H of the so-called photonic crystal structure 57 is, for example, 0.1 μm or more and 5 μm or less.

The "diameter of the photonic crystal structure 57" is the diameter of the circle when the planar shape of the photonic crystal structure 57 is a circle, and is not a circle when the planar shape of the photonic crystal structure 57 is not a circle. Is the diameter of the minimum inclusion circle. For example, when the planar shape of the photonic crystal structure 57 is a polygon, the diameter of the photonic crystal structure 57 is the diameter of the smallest circle including the polygon inside, and the planar shape of the photonic crystal structure 57 is In the case of an ellipse, the diameter of the photonic crystal structure 57 is the diameter of the smallest circle containing the ellipse.

The "center of the photonic crystal structure 57" is the center of the circle when the planar shape of the photonic crystal structure 57 is a circle, and when the planar shape of the photonic crystal structure 57 is not a circle. Is the center of the minimum inclusion circle. For example, when the plane shape of the photonic crystal structure 57 is a polygon, the center of the photonic crystal structure 57 is the center of the smallest circle including the polygon inside, and the plane of the photonic crystal structure 57. When the shape is an ellipse, the center of the photonic crystal structure 57 is the center of the smallest circle containing the ellipse.

As shown in FIG. 2, the plurality of photonic crystal structures 57 are arranged in a square lattice on the buffer layer 56. The pitches Px and Py between the two adjacent photonic crystal structures 57 are, for example, 1 nm or more and 500 nm or less. In the case of the present embodiment, the pitch Px in the X-axis direction and the pitch Py in the Y-axis direction are equal to each other. As described above, the plurality of photonic crystal structures 57 are periodically arranged at predetermined pitches Px and Py along the X-axis direction and the Y-axis direction orthogonal to each other. The pitch Px in the X-axis direction is the distance between the centers of two photonic crystal structures 57 adjacent to each other in the X-axis direction. The pitch Py in the Y-axis direction is the distance between the centers of two photonic crystal structures 57 adjacent to each other in the Y-axis direction. The plurality of photonic crystal structures 57 do not necessarily have to be arranged in a square lattice, and may be arranged in a rectangular lattice, a triangular lattice, or the like.

As shown in FIG. 3, the columnar portion 62 includes a first semiconductor layer 65, a light emitting layer 66, and a second semiconductor layer 67.

The first semiconductor layer 65 is provided on the buffer layer 56. The first semiconductor layer 65 is composed of, for example, an n-type GaN layer doped with Si.

The light emitting layer 66 is provided on the first semiconductor layer 65. The light emitting layer 66 is provided between the first semiconductor layer 65 and the second semiconductor layer 67. The light emitting layer 66 has a quantum well structure composed of, for example, a GaN layer and an InGaN layer. The light emitting layer 66 emits light by injecting an electric current through the first semiconductor layer 65 and the second semiconductor layer 67.

The second semiconductor layer 67 is provided on the light emitting layer 66. The second semiconductor layer 67 is a layer having a different conductive type from the first semiconductor layer 65. The second semiconductor layer 67 is composed of, for example, a p-type GaN layer doped with Mg. The first semiconductor layer 65 and the second semiconductor layer 67 function as a clad layer having a function of confining light in the light emitting layer 66.

The light propagation layer 63 is provided between adjacent columnar portions 62. In the example of FIG. 3, the light propagation layer 63 is provided on the mask layer 60. The refractive index of the light propagation layer 63 is lower than that of the light emitting layer 66. The light propagation layer 63 is composed of, for example, a silicon oxide layer, an aluminum oxide layer, a titanium oxide layer, and the like. The light generated in the light emitting layer 66 propagates in the light propagation layer 63.

In the light emitting element 20, a pin diode is composed of a laminate of a p-type second semiconductor layer 67, a light emitting layer 66 not doped with impurities, and an n-type first semiconductor layer 65. The bandgap of the first semiconductor layer 65 and the second semiconductor layer 67 is larger than the bandgap of the light emitting layer 66. When a forward bias voltage is applied to the pin diode and a current is injected between the first electrode 52 and the second electrode 53, electrons and holes are recombined in the light emitting layer 66, and light emission occurs.

The light generated in the light emitting layer 66 propagates through the light propagation layer 63 in the in-plane direction of the substrate 50 by the first semiconductor layer 65 and the second semiconductor layer 67. At this time, the light forms a standing wave due to the effect of the photonic crystal by the photonic crystal structure 57, and is confined in the in-plane direction of the substrate 50. The trapped light receives a gain in the light emitting layer 66 and oscillates by laser. That is, the light generated in the light emitting layer 66 resonates in the in-plane direction of the substrate 50 by the photonic crystal structure 57, and laser oscillates. Specifically, the light generated in the light emitting layer 66 resonates in the in-plane direction of the substrate 50 in the resonance portion composed of the plurality of photonic crystal structures 57, and laser oscillates. After that, the +1st-order diffracted light and the -1st-order diffracted light generated by the resonance proceed as laser light in the stacking direction (Z-axis direction).

The light emitted from the light emitting layer 66 resonates in the X-axis direction and the Y-axis direction in which a plurality of photonic crystal structures 57 are arranged at a constant pitch in the light emitting region 12R. That is, in the case of the present embodiment, the light emitting region 12R functions as a resonance portion where the light resonates. Therefore, the distance Dx between the photonic crystal structures 57 located at both ends of the plurality of photonic crystal structures 57 arranged in the X-axis direction corresponds to the resonance length in the X-axis direction. The distance Dy between the photonic crystal structures 57 located at both ends of the plurality of photonic crystal structures 57 arranged in the Y-axis direction corresponds to the resonance length in the Y-axis direction.

Of the laser light traveling in the stacking direction, the laser light traveling toward the reflection layer 55 side is reflected by the reflection layer 55 and travels toward the second electrode 53 side. As a result, the light emitting device 12 can emit light from the second electrode 53 side.

The third semiconductor layer 58 is provided on the photonic crystal structure 57. The third semiconductor layer 58 is composed of, for example, a p-type GaN layer doped with Mg.

The first electrode 52 is provided on the buffer layer 56 on the side of the photonic crystal structure 57. The first electrode 52 may be in ohmic contact with the buffer layer 56. In the example of FIG. 3, the first electrode 52 is electrically connected to the first semiconductor layer 65 via the buffer layer 56. The first electrode 52 is one electrode for injecting a current into the light emitting layer 66. As the first electrode 52, for example, a laminated film in which a Ti layer, an Al layer, and an Au layer are laminated in this order from the buffer layer 56 side is used.

The second electrode 53 is provided on the third semiconductor layer 58. The second electrode 53 may be in ohmic contact with the third semiconductor layer 58. The second electrode 53 is electrically connected to the second semiconductor layer 67. In the example of FIG. 3, the second electrode 53 is electrically connected to the second semiconductor layer 67 via the third semiconductor layer 58. The second electrode 53 is the other electrode for injecting a current into the light emitting layer 66. As the second electrode 53, for example, ITO (Indium Tin Oxide) is used. The second electrode 53 provided on one of the adjacent photonic crystal structures 57 and the second electrode 53 provided on the other are electrically connected by wiring (not shown).

Due to the photonic crystal effect, the size of the light emitting region, that is, the resonance length affects the light distribution angle of the light L0 emitted from the light emitting region. Specifically, the longer the resonance length, the smaller the light distribution angle of the emitted light L0, and the shorter the resonance length, the larger the light distribution angle of the emitted light L0.

FIG. 4 is a diagram showing the light distribution angle of the light L0 emitted from the light emitting region 12R.
As shown in FIG. 4, in the case of the present embodiment, the resonance length Dx in the X-axis direction is longer than the resonance length Dy in the Y-axis direction. In this case, as shown in FIG. 4, the light distribution angle θx along the X-axis direction of the light L0 emitted from the light emitting region 12R is smaller than the light distribution angle θy along the Y-axis direction. Conversely, by comparing the light distribution angle θx and the light distribution angle θy, the magnitude relationship between the resonance length Dx and the resonance length Dy can be confirmed. Assuming that the plane shape of the light emitting region 12R is square, the light distribution angle of the light L0 is rotationally symmetric with respect to the optical axis AX0. Specifically, the light distribution angle of the light L0 is, for example, about 5 ° at the maximum.
The light distribution angle is defined as the angle formed by the light beam emitted from one light emitting point O and the normal line AX0 passing through the light emitting point O.

Next, the operation of the angle conversion element 19 will be described.
FIG. 5 is a diagram showing the light distribution angles of the light L1 emitted from different positions of the angle conversion element 19. In the following, the operation of the angle conversion element 19 will be described by focusing on three characteristic positions on the angle conversion element 19 having different distances from the normal AX0.

As shown in FIG. 5, the angle conversion element 19 is composed of a base material having light transmission, and includes a first angle conversion unit 25, a second angle conversion unit 26, and an angle non-conversion unit 27. There is. The angle conversion element 19 refracts the light L0 emitted from the light emitting device 12, and changes the light distribution angle θ of the light before and after the incident. Here, the light distribution angle θ of the light L0 emitted from the light emitting device 12 is uniform (same) regardless of the light emitting position, and is set to θ0. The angle conversion element 19 has an incident end surface 19a on which the light L0 emitted from the light emitting device 12 is incident, and an emission end surface 19b that emits the light L1, L2, L3 after the light distribution angle θ has changed. There is. The axis that passes through the center of the incident end surface 19a and the injection end surface 19b of the angle conversion element 19 and is perpendicular to the incident end surface 19a and the injection end surface 19b is defined as the optical axis AX3 of the angle conversion element 19. It is desirable that the incident end surface 19a and the ejection end surface 19b of the angle conversion element are provided with an antireflection film.

The distance from the optical axis AX3 of the angle conversion element 19 to the second angle conversion unit 26 is longer than the distance from the optical axis AX3 of the angle conversion element 19 to the first angle conversion unit 25. Further, the distance from the optical axis AX3 of the angle conversion element 19 to the angle non-conversion unit 27 is longer than the distance from the optical axis AX3 of the angle conversion element 19 to the second angle conversion unit 26. That is, the first angle conversion unit 25, the second angle conversion unit 26, and the angle non-conversion unit 27 are arranged in this order from the center of the angle conversion element 19 toward the peripheral edge. In this case, the refractive power of the second angle conversion unit 26 is smaller than the refractive power of the first angle conversion unit 25. Further, the angle non-conversion unit 27 does not have a refractive power.

The center position of the first angle conversion unit 25 is the position P1, the center position of the second angle conversion unit 26 is the position P2, and the center position of the angle non-conversion unit 27 is the position P3. The distance from the optical axis AX3 of the angle conversion element 19 to each angle conversion unit 25, 26 or the angle non-conversion unit 27 is the optical axis AX3 of the angle conversion element 19 and each angle conversion unit 25, 26 or the angle non-conversion unit 27. It is defined as the distance between the center positions P1, P2, and P3 of.

As a result, the light distribution angle θ1 of the light L1 after being emitted from the first angle conversion unit 25 is larger than the light distribution angle θ1 of the light L0 before being incident on the first angle conversion unit 25. Similarly, the light distribution angle θ2 of the light L2 after being emitted from the second angle conversion unit 26 is larger than the light distribution angle θ0 of the light L0 before being incident on the second angle conversion unit 26. At this time, the light L0 incident on the second angle conversion unit 26 is refracted smaller than the light L0 incident on the first angle conversion unit 25, so that the light L2 emitted from the second angle conversion unit 26 is arranged. The light angle θ2 is smaller than the light distribution angle θ1 of the light L1 emitted from the first angle conversion unit 25.

Further, since the light L0 incident on the angle non-conversion unit 27 passes through the angle non-conversion unit 27 without being refracted, the light distribution angle θ3 of the light L3 after being emitted from the angle non-conversion unit 27 has no angle. It is the same as the light distribution angle θ0 of the light L0 before it enters the conversion unit 27 (θ3 = θ0). Therefore, the light distribution angle θ3 of the light L3 emitted from the angle non-conversion unit 27 is smaller than the light distribution angle θ2 of the light L2 emitted from the second angle conversion unit 26.

As shown in FIG. 5, the light distribution angle of the light L1 emitted from the first angle conversion unit 25 at the position P1 is θ1, and the light distribution angle of the light L2 emitted from the second angle conversion unit 26 at the position P2 is θ2. Assuming that the light distribution angle of the light L3 emitted from the angle non-conversion unit 27 at the position P3 is θ3, the magnitude relation of these light distribution angles is θ1> θ2> θ3. That is, the light distribution angles of the lights L1, L2, and L3 emitted from the respective positions P1, P2, and P3 gradually decrease from the center of the angle conversion element 19 toward the peripheral edge.

FIG. 8 is a diagram showing positions where the lights L1, L2, and L3 emitted from the respective positions P1, P2, and P3 in FIG. 5 reach the image forming region 17R of the liquid crystal display element 17.
As shown in FIG. 1, the luminous flux L emitted from the angle conversion element 19 passes through the incident side polarizing plate 16 and is an image forming region of the liquid crystal display element 17 arranged at a position separated from the angle conversion element 19 by a distance Z1. It is incident on 17R. At this time, the positions where the lights L1, L2, and L3 emitted from the respective positions P1, P2, and P3 reach the image forming region 17R are set as the positions Q1, Q2, and Q3, respectively, and each position Q1 from the center O1 of the image forming region 17R. Assuming that the distances to Q2 and Q3 are distances R1, R2, and R3, respectively, it is desirable that the magnitude relationship between these distances is R1 <R2 <R3. In other words, the arrival position of the light emitted from the position near the center of the angle conversion element 19 does not exceed the arrival position of the light emitted from the position farther from the center of the angle conversion element 19 than the position, and is inward. It is desirable to be located.

As a specific configuration of the angle conversion element 19 having the above-mentioned action, for example, the following two examples can be mentioned.
FIG. 6 is a cross-sectional view of the angle conversion element 40 of the first configuration example. In FIG. 6, an enlarged view of each part is shown on the right side of the overall view of the angle conversion element 40.
As shown in FIG. 6, the angle conversion element 40 of the first configuration example includes a first angle conversion unit 41, a second angle conversion unit 42, and an angle non-conversion unit 43.

The first angle conversion unit 41 has a first incident end surface 41a on which the light L0 emitted from the light emitting device 12 is incident, and a first emission end surface 41b on which the light L1 whose light distribution angle is changed is emitted. .. At least one of the first incident end surface 41a and the first ejection end surface 41b has a first concavo-convex structure 41d in which concave portions and convex portions are periodically provided. The second angle conversion unit 42 has a second incident end surface 42a on which the light L0 emitted from the light emitting device 12 is incident, and a second emission end surface 42b on which the light L2 whose light distribution angle is changed is emitted. .. At least one of the second incident end face 42a and the second ejection end face 42b has a second concavo-convex structure 42d in which concave portions and convex portions are periodically provided. The angle non-conversion portion 43 does not have a concavo-convex structure, and has a flat incident end surface 43a and an ejection end surface 43b.

The first concavo-convex structure 41d and the second concavo-convex structure 42d have different configurations from each other. Specifically, the pitch f2 of the second concavo-convex structure 42d is longer than the pitch f1 of the first concavo-convex structure 41d, and the depth t2 of the second concavo-convex structure 42d and the depth t1 of the first concavo-convex structure 41d are the same. You may. Alternatively, the pitch f2 of the second concavo-convex structure 42d and the pitch f1 of the first concavo-convex structure 41d are the same, and the depth t2 of the second concavo-convex structure 42d may be shallower than the depth t1 of the first concavo-convex structure 41d. .. Alternatively, the pitch f2 of the second concavo-convex structure 42d may be longer than the pitch f1 of the first concavo-convex structure 41d, and the depth t2 of the second concavo-convex structure 42d may be shallower than the depth t1 of the first concavo-convex structure 41d. .. That is, the pitch f2 of the second concave-convex structure 42d is longer than the pitch f1 of the first concave-convex structure 41d, and the depth t2 of the second concave-convex structure 42d is shallower than the depth t1 of the first concave-convex structure 41d. Of these, at least one of the conditions may be satisfied.

FIG. 7 is a cross-sectional view of the angle conversion element 70 of the second configuration example.
As shown in FIG. 7, the angle conversion element 70 of the second configuration example includes a first angle conversion unit 71, a second angle conversion unit 72, and an angle non-conversion unit 73.

The first angle conversion unit 71 is periodically provided with a first low refractive index unit 711 having a first refractive index and a first high refractive index unit 712 having a second refractive index higher than the first refractive index. It has the first refractive index periodic structure 71d. The second angle conversion unit 72 is periodically provided with a second low refractive index unit 721 having a third refractive index and a second high refractive index unit 722 having a fourth refractive index higher than the third refractive index. It has a second refractive index periodic structure 72d. The angle non-conversion unit 73 does not have a periodic refractive index structure, and is made of a base material having a constant refractive index.

The first refractive index periodic structure 71d and the second refractive index periodic structure 72d have different configurations from each other. Specifically, the pitch g2 of the second refractive index periodic structure 72d is longer than the pitch g1 of the first refractive index periodic structure 71d, and the difference in refractive index between the first refractive index and the second refractive index and the third refractive index The difference in refractive index between and the fourth refractive index may be the same. Alternatively, the pitch g2 of the second refractive index periodic structure 72d and the pitch g1 of the first refractive index periodic structure 71d are the same, and the difference in refractive index between the first refractive index and the second refractive index is the third refractive index. It may be smaller than the difference in refractive index from the fourth refractive index. Alternatively, the pitch g2 of the second refractive index periodic structure 72d is longer than the pitch g1 of the first refractive index periodic structure 71d, and the difference in refractive index between the first refractive index and the second refractive index is the third refractive index. It may be smaller than the difference in refractive index from the fourth refractive index. That is, the pitch g2 of the second refractive index periodic structure 72d is longer than the pitch g1 of the first refractive index periodic structure 71d, and the difference in refractive index between the first refractive index and the second refractive index is the third refractive index and the fourth. It suffices that at least one of the two conditions, which is smaller than the difference in refractive index from the refractive index, is satisfied.

Here, as the light source device of the comparative example, it is assumed that the light source device does not have an angle conversion element and is composed only of a light emitting device. The plane shape of the light emitting region of the light source device is square.
FIG. 10 is a diagram showing a cross-sectional shape and an intensity distribution perpendicular to the main light beam of the luminous flux L5 in the illuminated region in the light source device of the comparative example. The upper part of FIG. 10 shows the cross-sectional shape of the luminous flux L5, and the lower part of FIG. 10 shows the intensity distribution of the luminous flux. Further, in the upper part of FIG. 10, in addition to the cross-sectional shape of the luminous flux L5, contour lines of intensities (contour lines) are also shown.

In the light source device of the comparative example, as shown in FIG. 10, the cross-sectional shape of the light flux L5 emitted from the square light emitting region changes from a square shape to a shape with rounded corners. Further, the intensity distribution is high at the center of the illuminated area and low at the periphery of the illuminated area, and the intensity varies greatly depending on the position on the illuminated area.

On the other hand, FIG. 9 is a diagram showing a cross-sectional shape and an intensity distribution perpendicular to the main light beam of the luminous flux L in the illuminated region in the light source device 15 of the present embodiment. The upper part of FIG. 9 shows the cross-sectional shape of the luminous flux L, and the lower part of FIG. 9 shows the intensity distribution of the luminous flux L. In the upper part of FIG. 9, in addition to the cross-sectional shape of the luminous flux L, contour lines of intensities (contour lines) are also shown. Further, the broken lines in the upper part and the lower part of FIG. 9 show the cross-sectional shape and intensity distribution of the luminous flux L immediately after the light source device 15 emits light. Here, for comparison with the comparative example, the planar shape of the light emitting region 12R is assumed to be a square.

In the light source device 15 of the present embodiment, as shown in FIG. 9, the cross-sectional shape of the light flux L emitted from the angle conversion element 19 does not have much rounded corners as in the comparative example, and changes so much from a square. Not done. Further, the light emitted from the central portion of the angle conversion element 19 travels greatly, and the light emitted from the peripheral portion of the angle conversion element 19 travels without spreading so much, so that the light flux emitted from the angle conversion element 19 travels. The intensity distribution of L is slightly higher at the peripheral portion of the angle conversion element 19 than at the central portion, but an intensity distribution having a substantially constant intensity can be obtained regardless of the position on the illuminated region. As described above, the cross-sectional shape and intensity distribution of the luminous flux L immediately after the light source device 15 is emitted are sufficiently maintained even on the illuminated region.

As described above, the light source device 15 of the present embodiment includes the angle conversion element 19, and the light distribution angle is changed according to the position on the angle conversion element 19, so that the light source device 15 is separated from the light source device 15. The cross-sectional shape and intensity distribution of the light source L in the illumination region can be controlled. In particular, in the present embodiment, the light distribution angle of the light emitted from the peripheral portion of the angle conversion element 19 is smaller than the light distribution angle of the light emitted from the central portion of the angle conversion element 19, so that the light source device Even on the image forming region 17R of the liquid crystal display element 17 away from 15, the cross-sectional shape of the light flux L immediately after the light source device 15 is emitted can be sufficiently maintained.

As a result, according to the light source device 15 of the present embodiment, the cross-sectional shape of the emitted light flux L is substantially matched to the shape of the image forming region 17R, so that the light modulation device 13 can be efficiently illuminated. The cross-sectional shape of the luminous flux L changes depending on parameters such as the light distribution angle and distribution of the luminous flux L emitted from the light source device 15, the intensity and distribution of the luminous flux L, and the distance from the light source device 15.

Further, since the projector 10 of the present embodiment includes the light source device 15 that exerts the above-mentioned effect, the light utilization efficiency is high and the size can be reduced.

(Modification example)
FIG. 11 is a diagram showing the relationship between the distance from the center of the injection region of the angle conversion element 19 and the refractive power at that position. In FIG. 11, the horizontal axis represents the distance from the center of the injection region, and the vertical axis represents the refractive power. Assuming that the light distribution angle of the light incident on the angle conversion element 19 is uniform regardless of the incident position, the refractive power on the vertical axis represents the light distribution angle of the light emitted from the angle conversion element 19. Can be considered to be.

In FIG. 11, in the graphs of reference numerals A and B, the refractive power continuously changes according to the change in the distance from the center of the injection region. In this case, the ratio of the amount of change in the refractive power to the amount of change in the distance from the center of the injection region may be constant regardless of the distance from the center of the injection region, as shown in the graph of reference numeral A. As shown in the graph of reference numeral B, it may change in a curve depending on the distance from the center of the injection region.

When represented by the graphs of reference numerals A and B, in the case of the angle conversion element 40 of the first configuration example, at least one of the pitch and the depth of the concave-convex structure depends on the position of the incident end surface or the emission end surface of the angle conversion element 40. It may change continuously. Even when at least one of the pitch and the depth of the concave-convex structure changes continuously, the pitch and the pitch of the concave-convex structure and the region close to the peripheral portion of the angle conversion element 40 are compared. The average depths are different from each other. In this case, the region close to the central portion of the angle conversion element 40 can be regarded as the first angle conversion unit 41, and the region close to the peripheral portion can be regarded as the second angle conversion unit 42. This applies not only to the concave-convex structure but also to the refractive index periodic structure.

In FIG. 11, in the graph of reference numeral C, the refractive power changes stepwise according to the change in the distance from the center of the injection region. Further, as in the graph of reference numeral D, there may be a location where the refractive power increases locally as the position moves away from the central portion. In this way, the refractive power does not necessarily have to decrease monotonically as the distance from the center of the injection region increases, and when viewed as a whole, it decreases at the peripheral edge with respect to the center of the injection region. I just need to be there.

[Second Embodiment]
Hereinafter, the second embodiment of the present invention will be described with reference to FIG.
The basic configuration of the light source device of the second embodiment is the same as that of the first embodiment, and the configuration of the light emitting element is different from that of the first embodiment. Therefore, the entire description of the light source device will be omitted.
FIG. 12 is a plan view of the light emitting element of the second embodiment.
In FIG. 12, the same components as those in FIG. 2 used in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

In the light emitting element 20 of the first embodiment, as shown in FIG. 2, a plurality of photonic crystal structures 57 are uniformly provided in the entire light emitting region 12R, and the entire light emitting region 12R is one resonance. It made up the department. On the other hand, as shown in FIG. 12, in the light emitting element 80 of the second embodiment, the light emitting region 80R has a plurality of resonance portions 23.

In the case of the present embodiment, for example, a plurality of photonic crystal structures 57 arranged in a square lattice form one resonance portion 23, and a plurality of such resonance portions 23 are provided at intervals from each other. The plurality of resonance portions 23 are arranged on the first surface 50a of the substrate 50 so as to be separated from each other. That is, the photonic crystal structure 57 is not provided between the adjacent resonance portions 23. In FIG. 12, the photonic crystal structure 57 is shown only in one resonance portion 23, and the photonic crystal structure 57 is not shown in the other resonance portions 23.

In two adjacent resonance portions 23, the light that resonates in one resonance portion 23 does not reach the other resonance portion 23. The distance G between the resonant portions 23 and the resonant portions 23 adjacent to each other is larger than the wavelength of the light generated by the light emitting layer 66. Thereby, in the resonance portions 23 adjacent to each other, the light resonating in one resonance portion 23 can be configured so as not to reach the other resonance portion 23.

A light absorbing unit that absorbs light may be provided between the adjacent resonance units 23. The light absorption unit is composed of a substance having a band gap narrower than the band gap corresponding to the light resonating in the resonance unit 23. Examples of this kind of substance include InGaN and InN. The light absorbing portion is composed of, for example, a columnar or wall-shaped crystal body provided between adjacent resonance portions 23. As a result, in the adjacent resonance portions 23, the light resonating in one resonance portion 23 does not reach the other resonance portion 23.

Alternatively, a light reflecting portion that reflects light may be provided between the adjacent resonance portions 23. For example, a light reflecting portion can be formed by providing a columnar structure having a pitch or a diameter smaller than that of the photonic crystal structure 57 constituting the resonance portion 23 between adjacent resonance portions 23. As a result, in the adjacent resonance portions 23, the light resonating in one resonance portion 23 does not reach the other resonance portion 23.
Other configurations of the light source device are the same as those in the first embodiment.

Also in the light source device of the present embodiment, since the shape of the light flux L is substantially matched to the shape of the image forming region, the same effect as that of the first embodiment can be obtained, such that the light modulation device 13 can be efficiently illuminated.

Further, in the case of the present embodiment, the intensity distribution of the entire light emitting region 80R can be controlled by adjusting the intensity of the emitted light for each resonance portion 23. That is, the present invention can be applied to a light emitting device whose light emitting intensity is not uniform within the light emitting region 80R. The cross-sectional shape of the luminous flux L can be controlled by changing the light distribution angle of the light emitted from each resonance portion 23 in consideration of the emission intensity of the luminous flux L.

[Third Embodiment]
Hereinafter, in the third embodiment, another configuration example of the projector to which the light emitting device of the present invention can be applied will be described.
The basic configuration of the projector of the third embodiment is substantially the same as that of the projector of the first embodiment. Therefore, the description of the basic configuration is omitted, and only the different parts will be described.
FIG. 13 is a schematic configuration diagram of the projector of the third embodiment.
In FIG. 13, the same components as those in FIG. 1 used in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 13, the projector 38 of the third embodiment further includes a light guide body 39 provided between the light source device 15 and the light modulation device 13.

As the light guide body 39, as shown in FIG. 14, a light guide body 39A made of a solid rod-shaped body made of a translucent medium such as glass is used. Alternatively, as shown in FIG. 15, a light guide body 39B made of a hollow tubular body in which the reflection mirror is arranged in a tubular shape so that the reflection surface faces inward is used. Further, a light guide body having the same opening size and shape at the incident end 39a and the ejection end 39b may be used, or the aperture size increases (or decreases) from the incident end 39a toward the ejection end 39b. ) A tapered light guide may be used.

The aperture shapes of the incident end 39a and the emission end 39b of the light guide 39 are both rectangular, and are set to be substantially similar to the light emitting region 12R of the light emitting device 12 and the image forming region 17R of the liquid crystal display element 17. Further, it is desirable that the aperture size of the incident end 39a of the light guide body 39 is the same as or slightly larger than that of the light emitting region 12R. It is desirable that the opening size of the ejection end 39b of the light guide body 39 is set to be the same as or slightly larger than the image forming region 17R of the liquid crystal display element 17.

In the projector 38 of the present embodiment, since the light source device 15 of the above embodiment is used, the light flux L can be efficiently incident on the light guide body 39 arranged at a position away from the light source device 15.

Further, the luminous flux L incident on the light guide body 39 is emitted with a uniform intensity distribution due to a plurality of reflections at the interface or the inner wall surface of the light guide body 39. As a result, the intensity distribution of the light flux L may be further made uniform, and the liquid crystal display element 17 can be efficiently illuminated by the light flux L having a substantially uniform intensity. Further, since the light modulation device 13 can be arranged away from the light source device 15, the influence of the heat generated from the light source device 15 on the light modulation device 13 can be reduced.

The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above embodiment, the light emitting layer made of an InGaN-based material has been described, but various semiconductor materials can be used as the light emitting layer depending on the wavelength of the emitted light. For example, semiconductor materials such as AlGaN-based, AlGaAs-based, InGaAs-based, InGaAsP-based, InP-based, GaP-based, and AlGaP-based can be used. Further, the diameter of the photonic crystal structure or the pitch of the arrangement may be appropriately changed according to the wavelength of the emitted light.

Further, in the above embodiment, the photonic crystal structure is composed of a columnar structure protruding on the substrate, but a plurality of pores provided at a constant pitch in order to exhibit the photonic crystal effect are formed. You may have. That is, the light emitting region may include a photonic crystal structure having a periodic structure regardless of the columnar structure and the pores. Further, the light emitting device may be a surface light source including a light emitting element having no photonic crystal structure.

In addition, the specific description of the light source device, each component of the projector, its shape, number, arrangement, material, and the like is not limited to the above embodiment, and can be changed as appropriate. In the above embodiment, an example in which the light source device according to the present invention is mounted on a projector using a transmissive liquid crystal display element as a light modulation device is shown, but the present invention is not limited to this. The light source device according to the present invention may be mounted on a projector using a reflective liquid crystal display element or a digital micromirror device as a light modulation device.

For example, the projector according to the above embodiment may have a relay optical system. In this case, since the luminous flux shape is maintained in the relay optical system, when the distance between the light source device and the incident side lens is larger than the distance between the emission side lens and the light modulator, the angle conversion element is the light source device. It is desirable to place it between the relay optical system. When the distance between the light source device and the incident side lens is larger than the distance between the emission side lens and the light modulator, it is desirable that the angle conversion element is arranged between the relay optical system and the optical modulator. Alternatively, the angle conversion elements may be arranged at two locations, between the light source device and the relay optical system and between the relay optical system and the optical modulation device.

In the above embodiment, an example in which the light source device of the present invention is mounted on a projector is shown, but the present invention is not limited to this. The light source device of the present invention can also be applied to lighting equipment, automobile headlights, and the like.

10, 38 ... Projector, 12 ... Light emitting device, 12R ... Light emitting region, 13 ... Light modulator, 14 ... Projecting optical device, 15 ... Light source device, 19, 40, 70 ... Angle conversion element, 25, 41, 71 ... 1 angle conversion unit, 26, 42, 72 ... second angle conversion unit, 27, 43, 73 ... angle non-conversion unit, 41a ... first incident end face, 41b ... first injection end face, 41d ... first uneven structure, 42a ... 2nd incident end face, 42b ... 2nd injection end face, 42d ... 2nd uneven structure, 39, 39A, 39B ... light guide, 50 ... substrate (base material), 50a ... 1st surface, 57 ... photonic crystal structure Body, 71d ... 1st refractive index periodic structure, 72d ... 2nd refractive index periodic structure, 711 ... 1st low refractive index part, 712 ... 1st high refractive index part, 721 ... 2nd low refractive index part, 722 ... 2 High refractive index part.

Claims (14)

A light emitting device that emits light and
An angle conversion element that changes the light distribution angle of the light emitted from the light emitting device, and
With
The angle conversion element includes a first angle conversion unit and a second angle conversion unit.
The distance from the optical axis of the angle conversion element to the second angle conversion unit is longer than the distance from the optical axis to the first angle conversion unit.
The refractive power of the second angle conversion unit is smaller than the refractive power of the first angle conversion unit.
Light source device. The light source device according to claim 1, wherein the light distribution angle of the light emitted from the second angle conversion unit is smaller than the light distribution angle of the light emitted from the first angle conversion unit. The first angle conversion unit has a first incident end face on which the light emitted from the light emitting device is incident, and a first emission end surface on which light having a changed light distribution angle is emitted.
At least one of the first incident end face and the first ejection end face has a first concavo-convex structure in which concave portions and convex portions are periodically provided.
The second angle conversion unit has a second incident end surface on which the light emitted from the light emitting device is incident, and a second emission end surface on which the light whose light distribution angle is changed is emitted.
The light source device according to claim 1 or 2, wherein at least one of the second incident end face and the second ejection end face has a second uneven structure in which concave portions and convex portions are periodically provided. The light source device according to claim 3, wherein the pitch of the second concavo-convex structure is longer than the pitch of the first concavo-convex structure. The light source device according to claim 3, wherein the depth of the second concavo-convex structure is shallower than the depth of the first concavo-convex structure. The first angle conversion unit is periodically provided with a first low refractive index unit having a first refractive index and a first high refractive index unit having a second refractive index higher than the first refractive index. It has a first refractive index periodic structure,
The second angle conversion unit is periodically provided with a second low refractive index unit having a third refractive index and a second high refractive index unit having a fourth refractive index higher than the third refractive index. The light source device according to claim 1 or 2, which has a second refractive index periodic structure. The light source device according to claim 6, wherein the pitch of the second refractive index periodic structure is longer than the pitch of the first refractive index periodic structure. The difference in refractive index between the first refractive index and the second refractive index of the second refractive index periodic structure is the difference in refractive index between the third refractive index and the fourth refractive index of the first refractive index periodic structure. The light source device according to claim 5 or 7, which is smaller than. The angle conversion element further includes an angle non-conversion portion having no refractive power.
The light source device according to any one of claims 1 to 8, wherein the distance from the optical axis to the angle non-conversion unit is longer than the distance from the optical axis to the second angle conversion unit. The light emitting device includes a base material and a light emitting region provided on the first surface of the base material.
The light source device according to any one of claims 1 to 9, wherein the light emitting region has a photonic crystal structure having a periodic structure. The light source device according to claim 10, wherein the light emitting region has a plurality of resonance portions. The light source device according to any one of claims 1 to 11.
An optical modulation device that modulates the light emitted from the light source device according to image information to generate image light, and
A projection optical device that projects image light emitted from the light modulation device, and
Equipped with a projector. The projector according to claim 12, further comprising a light guide body provided between the light source device and the light modulation device. The projector according to claim 12, wherein the planar shape of the light emitting region is similar to the planar shape of the image forming region in the light modulation apparatus.

Images