JP2017156389A - Optical element, illumination device, image display device and projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element, an illumination device, an image display device and a projector capable of emitting light having a uniform in-plane intensity distribution.SOLUTION: The optical element includes a first light guide optical system for enlarging light along a first direction, and a second light guide optical system disposed on both ends in the first direction of the first light guide optical system and for enlarging light along a second direction. The first light guide optical system includes: a first light guide plate; a first light incidence part for allowing the light from the second light guide optical system to enter the first light guide plate; and a first light exiting part for allowing the light incident to the first light incidence part to propagate within the first light guide plate in an opposite direction to the incident position along the first direction, as well as enlarging the light to exit to the outside. The second light guide optical system includes: a second light guide plate; a second light incidence part disposed at both ends in the second direction of the second light guide plate and allowing the light incident from the outside to enter the second light guide plate; and a second light exiting part allowing the light incident to the second light incidence part to propagate in the second light guide plate in a direction opposite to the incident position along the second direction as well as enlarging the light to exit toward the first light incidence part.SELECTED DRAWING: Figure 1A

Description

  The present invention relates to an optical element, an illumination device, an image display device, and a projector.

  In recent years, as a display device that guides image light emitted from a light source to an observer's eyes and causes the observer to observe an image (virtual image), a wearable image display device such as a head mounted display (HMD) has been used. Attention has been paid. In such an HMD, an optical element that deflects image light in a direction different from the incident direction by diffraction is used as a configuration for guiding the image light to the observer's eyes.

  By the way, such an optical element may be used not only for a display device but also for a planar light emitting lighting device. For example, in the illuminating device shown in Patent Document 1 below, two stages of light guides are provided for taking in and out guided light by a diffraction grating formed through a low refractive index thin film layer on an optical waveguide layer formed on the surface of a glass substrate. Incident laser light is converted into a linear beam by the first-stage light guide, and the linear beam is converted into a planar shape by the second-stage light guide.

Japanese Patent Application Laid-Open No. 06-018727

  However, in the illuminating device, the amount of emitted light attenuates with increasing distance from the incident position of the laser beam, and thus the amount of emitted light is distributed in the diagonal direction of the second-stage light guide. When such a planar illumination device is used as a backlight of a liquid crystal display, uneven brightness occurs in an image displayed on the liquid crystal display. Therefore, it is desired to provide a new optical element that can emit light having a uniform intensity distribution.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an optical element, an illumination device, an image display device, and a projector that can emit light having a uniform intensity distribution.

  According to the first aspect of the present invention, the first light guiding optical system that expands the incident light in the first direction and emits the light from the first light emitting unit, and the second light that intersects the incident light with the first direction. A second light guiding optical system that expands in the direction and emits from the second light emitting unit, wherein the first light guiding optical system includes a first light incident unit provided at one end and the one A second light incident portion provided at the other end that is the end opposite to the end of the first light guide optical system, and the second light guide optical system is optically coupled to the first light guide optical system. The first light guiding optical system is connected, and both the light incident on the first light incident portion and the light incident on the second light incident portion are enlarged and emitted from the first light emitting portion. An optical element is provided that is an optical system.

  According to the optical element according to the first aspect, the first light guide optical system can emit light with uniform intensity by expanding the light incident from both ends. Therefore, by providing the first light guide optical system, light with uniform intensity can be emitted.

In the first aspect, the optical system includes a third light guide optical system that expands incident light in the second direction and emits the light from a third light emitting unit, and the second light guiding optical system includes the second light emitting unit. The third light guide optical system is arranged so that the light emitted from the third light emitting part is incident on the second light incident part. Preferably they are arranged.
According to this configuration, the light emitted from the second light guide optical system and the third light guide optical system can be made uniform and emitted by the first light guide optical system.

Further, the second light guide optical system receives light from both ends of the second light guide optical system, and the third light guide optical system has both ends of the third light guide optical system. It is more desirable that light be incident from each of the parts.
In this way, the second and third light guiding optical systems can emit light with uniform intensity by enlarging the light incident from both ends. Therefore, by providing the second and third light guide optical systems, it is possible to emit light with more uniform intensity.

In the first aspect, each of the first light incident part and the first light emitting part preferably includes a reflective volume holographic optical element.
According to this configuration, since the reflective volume holographic optical element with high diffraction efficiency is provided, high light utilization efficiency can be realized.

In the first aspect, the period of the interference fringes of the reflective volume holographic optical element of the first light incident part is the same as the period of the interference fringes of the reflective volume holographic optical element of the first light emitting part. It is preferable to be provided.
According to this configuration, light can be emitted at the same angle as the incident angle.

In the first aspect, the in-layer inclination of the interference fringes of the reflective volume holographic optical element of the first light incident portion is the in-layer inclination of the interference fringes of the reflective volume holographic optical element of the first light emitting portion. It is preferable that it is provided so as to have a mirror surface target relationship.
According to this configuration, in the first light guide optical system, the light propagating through the optical system can be emitted in the vertical direction by the first light emitting unit.

  According to a second aspect of the present invention, there is provided the optical element according to the first aspect, and a light source that emits light to each of the first light incident part and the second light incident part. The light guide optical system is provided with an illuminating device arranged so that light emitted from the first light emitting unit is incident on the second light guide optical system.

  According to the illuminating device which concerns on a 2nd aspect, the light from a light source can be irradiated as illumination light which has a uniform intensity distribution planarly.

  According to the third aspect of the present invention, the optical element according to the first aspect, an optical element, a light source that emits light to each of the second light guide optical system and the third light guide optical system, A lighting device is provided.

  According to the illuminating device which concerns on a 3rd aspect, the light from a light source can be irradiated as illumination light which has planar and uniform intensity distribution.

In the second and third aspects, the light source includes a branching optical system that branches light, and the branching optical system includes a light guide member, a branch incident unit that branches light and enters the light guide member, It is preferable to have a branch emission part that emits the branched light incident from the branch incident part toward the optical element.
According to this configuration, one light can be branched and incident on the optical element.
Furthermore, it is preferable that the light guide member has a rectangular shape in a plan view, and the branch incident part branches light so that the branched light travels toward the four corners of the light guide member in a plan view.
In this way, the light from one light source can be branched and incident on the four corners of the optical element satisfactorily.
In this configuration, a mirror that reflects light emitted from the light source and guides the light to the branching optical system may be further provided.
In this way, since the light traveling direction can be changed by the mirror, it is not necessary to arrange the branching optical system linearly along the light traveling direction. Accordingly, the degree of freedom of the layout layout of the branching optical system is increased, and the size of the illumination device can be reduced.

  According to a fourth aspect of the present invention, there is provided an image display device comprising the illumination device according to the second and third aspects and a light modulation device that modulates illumination light from the illumination device.

  According to the image display device according to the fourth aspect, since the illumination light having a bright and uniform intensity distribution is modulated, a high-quality image can be displayed.

In the fourth aspect, it is preferable that light guide means for guiding the image light modulated by the light modulation device to the eyes of an observer is further provided.
According to this configuration, it is possible to provide a head cloak display that directly leads a bright image to the eyes of the observer.
Furthermore, it is desirable that the light guide means includes a reflective volume holographic optical element.
According to this configuration, it is possible to provide a head mounted display that can visually recognize external light (see-through light) together with image light.

  According to a fifth aspect of the present invention, the illumination device according to the third and fourth aspects, a light modulation device that forms image light by modulating light from the illumination device according to image information, and the image A projection optical system that projects light is provided.

  According to the projector according to the fifth aspect, it is possible to project a high-quality image because the illumination light having a bright and uniform intensity distribution is modulated.

The figure which looked at the illuminating device which concerns on 1st Embodiment from the z direction. The figure which looked at the illuminating device which concerns on 1st Embodiment from the x direction. The figure which looked at the illuminating device which concerns on 1st Embodiment from the y direction. The figure which showed the light intensity distribution in each output light of light-guide plate output light. The figure which looked at the structure of the illuminating device which concerns on a comparative example from the z direction. The figure which looked at the structure of the illuminating device which concerns on a comparative example from the x direction. The figure which looked at the composition of the lighting installation concerning a comparative example from the y direction. Sectional drawing which shows the structure of the illuminating device which concerns on 2nd Embodiment. The figure which shows the structure of a light source device. The figure which shows the structure of a light source device. The figure which shows the structure of the light source device which concerns on a modification. Sectional drawing which shows the structure of the illuminating device which concerns on 3rd Embodiment. The figure which looked at the liquid crystal display device concerning a 4th embodiment from the z direction. Sectional drawing of the liquid crystal display device which concerns on 4th Embodiment. The figure which shows the structure of the liquid crystal display device which concerns on a modification. The figure which shows the cross-sectional structure of HMD which concerns on 5th Embodiment. The figure which shows the cross-sectional structure of HMD which concerns on a modification. FIG. 10 is a schematic configuration diagram of a projector according to a sixth embodiment. The schematic block diagram of the projector which concerns on a modification. The schematic block diagram of the projector which concerns on a modification.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent.

(First embodiment)
First, the lighting device according to the first embodiment of the present invention will be described.
1A to 1C are diagrams illustrating a configuration of a lighting device. 1A to 1C show a configuration in which the illumination device is viewed from three directions. In the drawings used in the following description, an xyz coordinate system is used as necessary. The Z direction corresponds to the light emission direction from the optical element, the x direction corresponds to one direction defining a plane parallel to the surface of the light guide plate constituting the optical element, and the y direction is orthogonal to the x direction and the z direction. Corresponds to the direction.

  As illustrated in FIGS. 1A to 1C, the illumination device 100 according to the present embodiment includes a light source 10 and a planar development optical system 20. The light source 10 irradiates the planar development optical system 20 with incident light composed of laser light. In the present embodiment, the light source 10 includes four light source units 10a that emit incident light L1, L2, L3, and L4. In the present embodiment, the light source unit 10a is composed of a semiconductor laser that emits laser light having a wavelength in the green region as incident light L1, L2, L3, and L4. The light source 10 further includes a collimator lens 10b that converts incident light L1, L2, L3, L4 emitted from each light source unit 10a into parallel light.

The planar development optical system 20 is configured by one aspect of the optical element of the present invention.
The planar development optical system 20 generates illumination light including a plurality of planarly arranged lights by expanding incident light L1, L2, L3, and L4 incident from the light source 10 (external).

  In the present embodiment, the planar development optical system 20 includes a first light guide optical system 21, a second light guide optical system 22, and a third light guide optical system 23. The second light guide optical system 22 and the third light guide optical system 23 are optically connected to the first light guide optical system 21. Here, being optically connected means a relationship in which light emitted from one side enters the other. That is, the light emitted from the second light guide optical system 22 and the third light guide optical system 23 enters the first light guide optical system 21 and the light emitted from the first light guide optical system 21 is the second guide. The case where it injects into at least one of the optical optical system 22 and the 3rd light guide optical system 23 is included. In the present embodiment, a case where light emitted from the second light guide optical system 22 and the third light guide optical system 23 enters the first light guide optical system 21 will be described as an example, as will be described later.

The first light guide optical system 21 receives incident light L1, L2, L3, and L4 from the light source 10. The first light guide optical system 21 includes a first light guide plate 11, a light incident part 12, and a first light emitting part 13.
The first light guide plate 11 is made of, for example, glass or optical resin, and is a parallel flat plate having a rectangular shape with a long side in the x direction and a short side in the y direction. In the present embodiment, the first light guide plate 11 is made of, for example, a glass substrate.

  The light incident unit 12 causes the light from the second light guide optical system 22 and the third light guide optical system 23 to enter the first light guide plate 11. The light incident part 12 has a function of diffracting light incident on the light incident part 12 in the + x direction.

The light incident part 12 includes a first light incident part 12A and a second light incident part 12B.
The first first light incident portion 12 </ b> A is provided on the lower surface 11 a (the surface on the −z direction side) of the first light guide plate 11 at the −x side end of the first light guide plate 11. As will be described later, light from the second light guide optical system 22 is incident on the first light incident portion 12A.

The second light incident portion 12 </ b> B is provided on the lower surface 11 a of the first light guide plate 11 at the + x side end of the first light guide plate 11. As will be described later, light from the third light guide optical system 23 is incident on the second light incident portion 12B.
In the present embodiment, the first light incident portions 12A and 12B are configured by holographic optical elements (HOEs). In the present embodiment, a reflective volume HOE that can increase the first-order diffraction efficiency among the HOEs is used.

  In this embodiment, the 1st light-projection part 13 is comprised from the reflection type volume HOE. The first light emitting unit 13 has a function of diffracting light incident on the first light emitting unit 13 in the + z direction.

The first light emitting unit 13 propagates the light incident from the light incident unit 12 into the first light guide plate 11 along the x direction (first direction) and expands the light to the outside.
The first light emitting part 13 is provided in a region sandwiched between the first light incident part 12A and the second light incident part 12B on the lower surface 11a of the first light guide plate 11.

  The first light emitting portion 13 has a structure in which a first HOE layer 13A and a second HOE layer 13B are stacked. The first HOE layer 13A diffracts the light incident on the first light guide plate 11 by the second light guide optical system 22 and emits the light to the outside. The second HOE layer 13B diffracts the light incident on the first light guide plate 11 by the third light guide optical system 23 and emits it to the outside.

  The second light guide optical system 22 is disposed on the upper surface 21a (first surface) side of the first light guide optical system 21 on the −x direction side (one side in the first direction), and is in the y direction (perpendicular to the first direction). Light is expanded at the same angle as the incident angle along the second direction. The principle of expanding light will be described later.

  The second light guide optical system 22 includes a second light guide plate 14, a light incident part 15, and a second light emitting part 16. The second light guide plate 14 is formed of a parallel flat plate having a long side in the y direction and a long and narrow rectangular shape having a short side in the x direction. In the present embodiment, the second light guide plate 14 is made of, for example, a glass substrate.

  The light incident portions 15 are provided at both ends of the second light guide plate 14 in the y direction, and allow the light incident from the light source 10 to enter the second light guide plate 14. The light incident part 15 has a function of diffracting light incident on the light incident part 15 in the y direction.

The light incident part 15 includes a light incident part 15A and a light incident part 15B.
The light incident part 15 </ b> A is provided on the upper surface 14 a (the surface on the + z direction side) of the second light guide plate 14 at the + y side end of the second light guide plate 14.
The light incident portion 15 </ b> B is provided on the upper surface 14 a of the second light guide plate 14 at the −y side end of the second light guide plate 14.

The second light emitting unit 16 propagates the light incident from the light incident unit 15 into the second light guide plate 14 in the direction opposite to the incident position along the y direction and expands the first light guide optical system 21. To the first light incident portion 12A.
The second light emitting portion 16 is provided in a region between the light incident portions 15A and 15B on the upper surface 14a of the second light guide plate 14. The second light emitting portion 16 is set to a size that overlaps at least the first light incident portion 12A when viewed in plan from the z direction. The second light emitting unit 16 has a function of diffracting light incident on the second light emitting unit 16 in the −z direction.

  In the present embodiment, the light incident part 15 and the second light emitting part 16 are composed of a reflective volume HOE.

  The second light emitting unit 16 has a structure in which a first HOE layer 16A and a second HOE layer 16B are stacked. The first HOE layer 16 </ b> A diffracts the light incident on the second light guide plate 14 by the light incident portion 15 </ b> A and emits the light toward the first light guide plate 11. The second HOE layer 16 </ b> B diffracts the light incident on the second light guide plate 14 by the light incident part 15 </ b> B and emits the light toward the first light guide plate 11.

  The third light guide optical system 23 is disposed on the upper surface 21a side on the + x direction side (the other side in the first direction) of the first light guide optical system 21, and expands light at the same angle as the incident angle along the y direction. Let The principle of expanding light will be described later.

  The third light guide optical system 23 includes a third light guide plate 17, a light incident part 18, and a third light emitting part 19. The third light guide plate 17 is composed of a parallel plate having long sides in the y direction. In the present embodiment, the third light guide plate 17 is made of, for example, a glass substrate.

  The light incident portions 18 are provided at both ends of the third light guide plate 17 in the y direction, and allow the light incident from the light source 10 to enter the third light guide plate 17. The light incident part 18 includes a light incident part 18A and a light incident part 18B.

The light incident portion 18A is provided on the upper surface 17a (the surface on the + z direction side) of the third light guide plate 17 at the + y side end of the third light guide plate 17.
The light incident portion 18 </ b> B is provided on the upper surface 17 a of the third light guide plate 17 at the −y side end of the third light guide plate 17.

The third light emitting unit 19 propagates the light incident from the light incident unit 18 in the third light guide plate 17 in the direction opposite to the incident position along the y direction and expands the first light guide optical system 21. To the second light incident portion 12B.
The third light emitting portion 19 is provided in a region sandwiched between the light incident portions 18 </ b> A and 18 </ b> B on the upper surface 17 a of the third light guide plate 17. The third light emitting unit 19 is set to have a size that overlaps at least the second light incident unit 12B when viewed in plan from the z direction.

  In the present embodiment, the light incident part 18 and the third light emitting part 19 are composed of a reflective volume HOE.

  The third light emitting unit 19 has a structure in which a first HOE layer 19A and a second HOE layer 19B are stacked. The first HOE layer 19 </ b> A diffracts the light incident on the third light guide plate 17 by the light incident portion 18 </ b> A and emits the light toward the first light guide plate 11. The second HOE layer 19B diffracts the light incident on the third light guide plate 17 by the light incident portion 18B and emits the light toward the first light guide plate 11.

  In the present embodiment, the incident lights L 1 and L 2 emitted from the light source 10 are incident on the light incident portion 15 of the second light guide optical system 22. Specifically, the incident light L1 is incident on the light incident portion 15A, and the incident light L2 is incident on the light incident portion 15B.

In the present embodiment, the incident light L1 is incident perpendicular to the light incident portion 15A. The incident light L1 is reflected by the light incident portion 15A at an angle larger than the critical angle of the second light guide plate 14, and propagates through the second light guide plate 14 by total reflection.
Similarly, the incident light L2 enters the light incident portion 15B perpendicularly, is reflected by the light incident portion 15B at an angle larger than the critical angle of the second light guide plate 14, and propagates through the second light guide plate 14 by total reflection. To do.

  In the present embodiment, the light incident portion 15 is configured by the reflective volume HOE, so that the entire optical system can be made thinner than the configuration using the mirror, and the incident light L1 and L2 can be guided to the second light with high efficiency. It is introduced into the light plate 14. In the present embodiment, the light incident part 15 is configured using a reflective volume HOE that can increase the first-order diffraction efficiency among HOEs.

  The reflective volume HOE has remarkably large angle dependency and wavelength dependency of diffraction efficiency. In the present embodiment, since the incident lights L1 and L2 are used at a specific wavelength (green light) and a specific incident angle (0 degree), the Bragg diffraction condition can be satisfied, and a very high diffraction efficiency can be obtained. .

  Hereinafter, the propagation light in which the incident light L1 propagates in the second light guide plate 14 by total reflection is referred to as total reflection propagation light L1A, and the incident light L2 in the second light guide plate 14 propagates in total reflection by total reflection. This is referred to as propagating light L2A.

  Total reflection propagation light L1A and L2A propagating through the second light guide plate 14 by total reflection enter the second light emitting unit 16. In the present embodiment, the second light emitting unit 16 is configured by the reflective volume HOE, so that the emitted light is introduced into the first light guide plate 11 with high efficiency.

  By reducing the thickness of the second light emitting portion 16, the first-order diffraction efficiency can be suppressed. Accordingly, only a part of the total reflection propagation light L1A incident on the second light emitting unit 16 is diffracted and the emitted light L1b is emitted from the second light guide plate 14. Similarly, only a part of the total reflection propagation light L <b> 2 </ b> A incident on the second light emitting unit 16 is diffracted and the emitted light L <b> 2 b is emitted from the second light guide plate 14.

  The totally reflected propagation lights L1A and L2A that have not been diffracted propagate again in the second light guide plate 14 by total reflection, and enter the second light emitting portion 16 again. By repeating this process, the total reflection propagating light L1A, L2A is taken out from the second light guide plate 14 little by little, and the plurality of emitted light L1b, L2b are arranged at equal intervals along the y-axis direction. L1B and L2B are generated.

  In the present embodiment, the grating period (grating period along the light guide plate surface) of the light incident part 15 and the second light emitting part 16 is the same. Thereby, the output angles of the light guide plate output lights L1B and L2B can be made the same as the incident angles of the incident lights L1 and L2. In the present embodiment, since the incident angles of the incident lights L1 and L2 are 0 degrees with respect to the normal line of the light incident portion 15, that is, perpendicular incidence, the emission angle of the emitted light is also 0 degrees, that is, perpendicular emission.

  In this embodiment, the in-layer inclination of the interference fringes recorded in the layer of the second light emitting portion 16 is a mirror surface with respect to the in-layer inclination of the interference fringes of the light incident portion 15 (light incidence portions 15A and 15B). It is symmetrical (see the hatching shown in FIGS. 1A-1C).

  The second light emitting unit 16 includes a first HOE layer 16A having an in-layer inclination that is mirror-symmetrical with respect to the in-layer inclination of the interference fringe of the light incident part 15A, and the in-layer inclination of the interference fringe of the light incident part 15B. And a second HOE layer 16B having an in-layer inclination that is mirror-symmetrical. The second light emitting unit 16 is not limited to a laminated structure, and a single-layer reflective volume HOE in which interference fringes corresponding to the light incident units 15A and 15B are recorded in multiple layers may be used.

The in-layer inclinations of the interference fringes of the first HOE layer 16A and the second HOE layer 16B are mirror-symmetric (see hatching shown in FIGS. 1A to 1C).
Since the incident angle dependence of the diffraction efficiency of the reflective volume HOE is remarkably large, the first HOE layer 16A has almost zero diffraction efficiency with respect to the total reflected propagation light L2A, and the second HOE layer 16B has a diffraction efficiency with respect to the total reflection propagation light L1A. It is almost zero and does not diffract substantially.

  Therefore, the total reflection propagation light L1A is diffracted only by the first HOE layer 16A, and the total reflection propagation light L2A is diffracted only by the second HOE layer 16B. As described above, by using the reflective volume HOE, it is possible to selectively diffract or emit light depending on the direction of propagating light propagating in the light guide plate.

  The second light emitting unit 16 can diffract the total reflection propagation light L1A and L2A propagating through the second light guide plate 14 and emit the light in the vertical direction. Therefore, the second light emitting unit 16 can return the emitted light L1b and L2b of the light guide plate emitted light L1B and L2B to the −z side of the second light guide plate 14 and enter the first light guide plate 11.

  By the way, each of the outgoing lights L1b and L2b of the light guide plate outgoing lights L1B and L2B actually has a light intensity distribution represented by a Gaussian distribution. FIG. 2 is a diagram showing the light intensity distributions of the outgoing light L1b and L2b of the light guide plate outgoing light L1B and L2B.

  As shown in FIG. 2, the light intensity of each outgoing light L1b decreases as the distance from the incident position with respect to the second light guide plate 14 increases. Similarly, the light intensity of each outgoing light L2b decreases as the distance from the incident position with respect to the second light guide plate 14 increases. Specifically, the light intensity of the emitted light L1b decreases as the light emission position moves in the −y direction, and the light intensity of the light L2b decreases as the light emission position moves in the + y direction.

  According to the present embodiment, the outgoing lights L1b and L2b are emitted to the outside by being diffracted by the second light emitting part 16, and the outgoing positions from the second light guide plate 14 in the outgoing lights L1b and L2b are matched. Can be made.

  Therefore, the outgoing lights L1b and L2b are combined at the outgoing positions of the second light guide plate 14, respectively. Since the light intensities of the outgoing lights L1b and L2b are opposite to each other in the y direction, the light intensity of the light L1c obtained by combining the outgoing lights L1b and L2b is substantially the same regardless of the outgoing position.

Therefore, the second light guide optical system 22 generates light guide plate emission light L1C in which a plurality of lights L1c having uniform light intensity are arranged in the y direction. The light guide plate output light L <b> 1 </ b> C enters the first light guide plate 11.
As described above, according to the second light guide optical system 22, the input light L1 and L2 incident from both ends of the second light guide plate 14 are enlarged to generate the light guide plate output light L1C having a uniform intensity distribution. Can do.

Returning to FIG. 1, each light L <b> 1 c of the light guide plate outgoing light L <b> 1 </ b> C incident on the first light guide plate 11 enters the light incident portion 12 (first light incident portion 12 </ b> A).
Each light L1c of the light guide plate output light L1C is perpendicularly incident on the first light incident portion 12A. Each light L1c is reflected by the first light incident portion 12A at an angle larger than the critical angle of the first light guide plate 11, and propagates through the first light guide plate 11 by total reflection.

Hereinafter, the propagation light in which the light L1c propagates through the first light guide plate 11 by total reflection is referred to as total reflection propagation light L1D.
The total reflection propagation light L <b> 1 </ b> D that propagates through the first light guide plate 11 by total reflection enters the first light emitting unit 13. The first-order diffraction efficiency can be suppressed by reducing the thickness of the first light emitting portion 13. Thereby, only a part of the total reflection propagating light L1D incident on the first light emitting unit 13 is diffracted and the emitted light L1e is emitted from the first light guide plate 11.

  The totally reflected propagation light L1D that has not been diffracted again propagates through the first light guide plate 11 by total reflection, and enters the first light emitting unit 13 again. By repeating this process, the total reflection propagation light L1D is gradually extracted from the first light guide plate 11, and the light guide plate output light L1E in which a plurality of output lights L1e are arranged at equal intervals along the x direction is generated.

  In the present embodiment, the grating period (grating period along the light guide plate surface) of the light incident part 12 and the first light emitting part 13 is the same. Thereby, the output angle of the light guide plate output light L1E can be made the same as the incident angle of the light guide plate output light L1C (light L1c). That is, since the light L1c is perpendicularly incident on the light incident portion 12, each of the emitted light L1e of the light guide plate emitted light L1E that is emitted light is also emitted vertically from the first light emitting portion 13.

  In the present embodiment, the in-layer inclination of the interference fringes recorded in the layer of the first light emitting section 13 is mirror-symmetric with respect to the in-layer inclination of the interference fringes of the light incident section 12 (FIG. 1A). ~ See 1C hatching).

  The first light emitting unit 13 includes a first HOE layer 13A having an in-layer inclination that is mirror-symmetric with respect to an in-layer inclination of the interference fringes of the first light incident unit 12A, and an interference fringe layer of the second light incident unit 12B. The second HOE layer 13B having an in-layer inclination that is mirror-symmetrical with respect to the inner inclination is laminated. The first light emitting unit 13 is not limited to the laminated structure, and a single-layer reflective volume HOE in which interference fringes corresponding to the first light incident units 12A and 12B are recorded in multiple layers may be used.

  The in-layer inclination of the interference fringes of the first HOE layer 13A and the second HOE layer 13B is mirror-symmetric. Since the incident angle dependence of the diffraction efficiency of the reflective volume HOE is remarkably large, the first HOE layer 13A has substantially zero diffraction efficiency for propagating light incident from the second light incident portion 12B, and the second HOE layer 16B has the first efficiency. The diffraction efficiency with respect to the total reflection propagation light L1D incident from the light incident part 12A is substantially zero and is not substantially diffracted.

  Therefore, the total reflected propagation light L1D is diffracted only by the first HOE layer 16A, and the propagation light incident from the second light incident portion 12B is diffracted only by the second HOE layer 16B. As described above, by using the reflective volume HOE, it is possible to selectively diffract or emit light depending on the direction of propagating light propagating in the light guide plate.

  The first light emitting unit 13 can emit the total reflection propagation light L1D propagating through the first light guide plate 11 in the vertical direction. Therefore, the 1st light emission part 13 can return | fold each light L1e of the light-guide plate emitted light L1E to the + z side of the 1st light-guide plate 11, and inject | emits it outside.

  Incident light L3 and L4 emitted from the light source 10 is incident on the light incident portion 18 of the third light guide optical system 23. Specifically, the incident light L3 is incident on the light incident portion 18A, and the incident light L4 is incident on the light incident portion 18B.

  Since the third light guide optical system 23 has the same configuration as the second light guide optical system 22, the third light guide optical system 23 performs light expansion in the same manner as the second light guide optical system 22. Therefore, the description of the expansion of light in the third light guide optical system 23 is simplified.

  Hereinafter, the propagation light in which the incident light L3 propagates through the third light guide plate 17 by total reflection is referred to as total reflection propagation light L3A, and the incident light L4 is the total reflection from the propagation light propagated through the third light guide plate 17 by total reflection. This is referred to as propagating light L4A.

In the third light guide optical system 23, the total reflection propagation lights L3A and L4A are taken out from the third light guide plate 17 little by little. Similar to the second light guide optical system 22, the third light guide optical system 23 generates light guide plate emission light L1F in which a plurality of lights having uniform light intensity are arranged in the y direction. Each light L1f of the light guide plate output light L1F is perpendicularly incident on the second light incident portion 12B. Each light L1f is reflected by the second light incident part 12B at an angle larger than the critical angle of the first light guide plate 11, and propagates through the first light guide plate 11 in the -x direction by total reflection. Thereby, the light guide plate emission light L1G in which a plurality of emission lights L1g are arranged at equal intervals along the X direction is generated.
As described above, according to the third light guide optical system 23, the input light L3 and L4 incident from both ends of the third light guide plate 17 are respectively expanded to generate the light guide plate output light L1G having a uniform intensity distribution. be able to.

  Here, the outgoing lights L1e and L1g of the light guide plate outgoing lights L1E and L1G also have a light intensity distribution represented by a Gaussian distribution. The light intensity of the outgoing light L1e decreases as the light output position moves in the + x direction, and the light intensity of the outgoing light L1g decreases as the light output position moves in the −x direction.

  According to the present embodiment, the outgoing lights L1e and L1g are emitted to the outside by being diffracted by the first light emitting part 13, and the outgoing positions from the first light guide plate 11 in the outgoing lights L1e and L1g are made to coincide. be able to. Therefore, the outgoing lights L1e and L1g are combined at the outgoing positions of the first light guide plate 11, respectively. Since the light intensities of the emitted lights L1e and L1g are on the opposite side in the x direction, the light intensity of the light L1h obtained by synthesizing the emitted lights L1e and L1g is substantially the same regardless of the emission position.

  Here, when the emission interval of each light L1h constituting the illumination light L1H is larger than the beam size defined by the Gaussian distribution, the illumination light L1H becomes discrete, and the intensity distribution in the plane of the illumination light L1H becomes non-uniform. .

  In the present embodiment, the first light guide plate 11, the second light guide plate 14, and the third light guide plate 17 are configured such that the emission interval of each light L 1 h constituting the illumination light L 1 H is smaller than the beam size defined by the Gaussian distribution. The interval of the outgoing light is optimized. The interval between the outgoing lights can be appropriately adjusted by the wavelength of the incident light, the grating period of the HOE, the refractive index and the thickness of the light guide plate.

Here, in order to clarify the effect of the illumination device 100 of the present embodiment, a comparative example will be described.
In the comparative example, a case where illumination light is generated by developing one incident light in a planar shape will be described.
3A to 3C are diagrams illustrating a configuration of an illumination device 200 according to a comparative example. 3A to 3C are views of the lighting device 200 viewed from three directions (x direction, y direction, and z direction).

  As illustrated in FIGS. 3A to 3C, the illumination device 200 includes a light source 210 and a planar development optical system 220. The light source 210 irradiates the planar development optical system 220 with one incident light LL made of laser light.

  The planar development optical system 220 includes two light guide optical systems 221 and 222. The light guide optical system 221 has the same configuration as the first light guide optical system 21 except that the light incident portion is provided only on one end side (−x direction side). The light guide optical system 222 has the same configuration as the second light guide optical system 22 except that the light incident portion is provided only on one end side (−Y direction side).

In the configuration of this comparative example, the light intensity (Gaussian distribution) of the output light LL1 from the light guide optical system 222 to the light guide optical system 221 decreases as the light output position moves in the + Y direction.
Similarly, the light intensity (Gaussian distribution) of the output light LL2 from the light guide optical system 221 decreases as the light output position moves in the + x direction.

  That is, in the configuration of the comparative example, the intensity distribution T of the emitted light is generated in the diagonal direction of the planar development optical system 220 according to the distance from the light incident position in the light source 210. Therefore, uneven brightness occurs in the illumination light.

  On the other hand, according to the illuminating device 100 of this embodiment, light is incident from both ends of the light guide plate in any of the first light guide optical system 21, the second light guide optical system 22, and the third light guide optical system 23. I tried to make it. Therefore, uniform light is emitted from each of the light guide optical systems 21, 22, and 23, and the light L 1 h having uniform light intensity is arranged in a planar shape in the x direction and the Y direction by combining these lights. The illumination light L1H can be generated.

  In addition, since the thickness of the planar development optical system 20 that develops the light from the light source 10 into a plane is almost the same as that of two light guide plates, a very thin illumination device 100 can be realized.

  Further, in this embodiment, the incident angle and the emission angle to the reflective volume HOE layer are fixed by vertical incidence and vertical emission, and a single wavelength is determined by using a laser as the incident light L, so that the reflective volume HOE layer is diffracted. It can be used under conditions that increase efficiency. Therefore, the incident light L from the light source unit 10a can be efficiently converted into the illumination light L1H. Therefore, bright illumination light L1H can be obtained even if the number of light source portions 10a is small.

In the present embodiment, the case where the light emitted from the second light guide optical system 22 and the third light guide optical system 23 is incident on both ends of the first light guide optical system 21 (first light guide plate 11) is taken as an example. However, the present invention is not limited to this.
For example, the structure using only the 1st light guide optical system 21 and the 2nd light guide optical system 22 may be sufficient. That is, light from the second light guide optical system 22 is incident on one end of the first light guide plate 11 and light from another light source is incident on the other end instead of the third light guide optical system 23. Also good. Also in this configuration, the first light guide optical system 21 can generate light with uniform intensity by guiding light incident from both ends. Further, at least the second light guide optical system 22 can make uniform light incident on one end side of the first light guide optical system 21.

  Similarly, only the first light guide optical system 21 and the third light guide optical system 23 may be used. That is, the light from the third light guide optical system 23 is incident on the other end of the first light guide plate 11 and the light from another light source is incident on the other end instead of the second light guide optical system 22. It may be. Also in this configuration, the first light guide optical system 21 can generate light with uniform intensity by guiding light incident from both ends. Further, at least the third light guide optical system 23 can make uniform light incident on the other end side of the first light guide optical system 21.

  In addition, the present invention only needs to include the first light guide optical system 21 into which light is incident from at least both ends, and the second light guide optical system or the third light guide optical system can transmit incident light in one direction ( Any structure may be used as long as it expands in the y direction). In other words, the second light guide optical system or the third light guide optical system may be one that expands light in one direction by making light incident from one end side of the second light guide plate 14 or the third light guide plate 17. good.

In addition, by arranging a light source that emits light in each of the first light incident portion 12A and the second light incident portion 12B of the first light guide optical system 21, the light emitted from the first light emitting portion 13 is second. The light may be incident on the light guide optical system 22 or the third light guide optical system 23.
According to this structure, the 1st light guide optical system 21 can radiate | emit uniform light by each expanding the light which injected from both ends. Therefore, uniform light can be incident on the second light guide optical system 22 or the third light guide optical system 23.

(Second Embodiment)
Subsequently, a second embodiment of the present invention will be described. The difference between this embodiment and 1st Embodiment is the structure of an illuminating device. Below, the same code | symbol is attached | subjected about the structure and member same as 1st Embodiment, and detailed description is abbreviate | omitted.

  In the illuminating device 100 of the first embodiment, the laser light is incident on the diagonal four corners of the second light guide optical system 22. In this case, since four light sources are required, it is difficult to reduce the size of the light source 10 and the illumination device 100 including the light source 10. In the present embodiment, the illumination device itself is reduced in size by reducing the size of the light source.

FIG. 4 is a cross-sectional view showing the configuration of the illumination device of this embodiment.
As shown in FIG. 4, the illumination device 100 </ b> A of the present embodiment includes a light source 10 </ b> A and a planar development optical system 20.

  FIG. 5A is a view of the light source 10A of the present embodiment as viewed from the z direction, and FIG. 5B is a cross-sectional configuration view of the light source 10A taken along line AA.

  As illustrated in FIGS. 5A and 5B, the light source 10 </ b> A includes a light source unit 30, a collimator lens 31, and a branching optical system 35. The branching optical system 35 includes a fourth light guide plate 32, a branching incident part 33, and a branching emission part 34. The light from the light source part 30 is branched into four lights and the diagonal of the planar development optical system 20. Incident at the four corners.

The light source unit 30 includes a semiconductor laser that emits laser light having a wavelength in the green region as the incident light L.
The collimator lens 31 converts incident light L that is divergent light emitted from the light source unit 30 into substantially parallel light.
The fourth light guide plate 32 is made of, for example, glass or optical resin, and is made of a parallel plate having a substantially rectangular shape on a plane. In the present embodiment, the fourth light guide plate 32 is made of, for example, a glass substrate.

  The branch incident unit 33 branches the incident light L from the light source unit 30 and enters the fourth light guide plate 32. The branch incident portion 33 is formed at the center of the upper surface 32 a of the fourth light guide plate 32.

  The branch emitting unit 34 emits the branched light incident from the branch incident unit 33 toward the planar development optical system 20 shown in FIG. The branch emission part 34 is formed on the lower surface 32 b of the fourth light guide plate 32. The branch emission unit 34 includes a first branch emission unit 34A, a second branch emission unit 34B, a third branch emission unit 34C, and a fourth branch emission unit 34D. Each branch emission part 34A-34D is formed in the four corners of the lower surface 32b of the 4th light-guide plate 32, respectively.

  In the present embodiment, the branch incident portion 33, the first branch exit portion 34A, the second branch exit portion 34B, the third branch exit portion 34C, and the fourth branch exit portion 34D are composed of a reflective volume HOE. The branch incident unit 33 has a function of diffracting light incident on the branch incident unit 33 toward four directions where the branch emission units 34A to 34D are provided.

  The interference fringes of the branch emission part 34 (the first branch emission part 34A, the second branch emission part 34B, the third branch emission part 34C, and the fourth branch emission part 34D) are the center of the branch incident part 33 and each branch emission part 34A. It extends in a direction perpendicular to a line (branch direction) connecting the centers of .about.34D. The grating period of the branch incident part 33 and each branch output part 34A-34D is the same.

  In the present embodiment, the branch incident portion 33 is composed of a single reflection type volume HOE, and four interference fringes extending perpendicularly to the four branch directions are recorded. The in-layer inclination of each of the four interference fringes is mirror-symmetrical with the in-layer inclination of each of the branch emission portions 34A to 34D at the four corners corresponding to each of the four interference fringes.

  The incident light L perpendicularly incident on the branch incident part 33 recorded in quadruple in this way is diffracted in the direction toward the respective branch emission parts 34A to 34D at the diagonal four corners to become four branch light LC. The four branched lights LC are diffracted into the fourth light guide plate 32 at an angle greater than the critical angle, propagated through the fourth light guide plate 32 with total reflection, reach the branched light output portions 34A to 34D, and reach the HOE surface. On the other hand, the light is emitted from the fourth light guide plate 32 by being diffracted in the vertical direction.

  In addition, what is necessary is just to adjust the grating | lattice period of HOE, the refractive index of a branch light-guide plate, and thickness, in order to adjust the radiation | emission position of light from each branch radiation | emission part 34A-34D.

  The branching incident portion 33 may adopt a configuration in which two HOE layers in which HOEs in two directions are recorded are stacked, or a configuration in which four HOE layers in which one direction is recorded are stacked. May be.

Returning to FIG. 4, the four branched lights LC emitted from the branched emission parts 34 </ b> A to 34 </ b> D are incident on the diagonal four corners of the planar development optical system 20.
According to the illumination device 100A of the present embodiment, only one light source unit 30 is required, and the planar development optical system 20 and the branching optical system 35 are configured by a light guide plate. Can do.
As described above, according to the present embodiment, it is possible to provide an illumination device 100A that is thin and emits light in a planar shape from one light source unit 30 and has excellent uniformity of light emission intensity.

In the present embodiment, the case where the incident light L from the light source unit 30 is incident on the branching optical system 35 perpendicularly is described as an example, but the present invention is not limited to this.
For example, as shown in FIG. 6, incident light L from the light source unit 30 may be reflected by a mirror 36 and guided to the branching optical system 35. According to this configuration, the depth of lighting device 100A can be further reduced.

(Third embodiment)
Subsequently, a third embodiment of the present invention will be described. The difference between this embodiment and the said 1st, 2nd embodiment is the structure of an illuminating device. In the following, the same components and members as those in the above embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
In the above embodiment, the lighting device using monochromatic light has been described. In this embodiment, a lighting device using laser light of three colors of red (R), green (G), and blue (B) will be described.

FIG. 7 is a cross-sectional view showing the configuration of the illumination device of the present embodiment.
As shown in FIG. 7, the illumination device 100B of the present embodiment includes a light source 10B and a planar development optical system 20B.

  The light source 10B of the present embodiment includes a light source unit 130, a collimator lens 31, and a branching optical system 135. The light source unit 130 includes a semiconductor laser 130R that emits laser light LR in the red wavelength band, a semiconductor laser 130G that emits laser light LG in the green wavelength band, and a semiconductor laser 130G that emits laser light LB in the blue wavelength band. The white incident light LA is emitted.

The basic configuration and principle of the branching optical system 135 of this embodiment are the same as those of the branching optical system 35 shown in FIG.
The branching optical system 135 includes a light guide plate 132, a branching incident part 133, and a branching emission part 134. The light from the light source part 130 is branched into four lights and is formed at the four corners of the planar development optical system 20B. Make it incident. The light guide plate 132 is made of, for example, a glass substrate, and is made of a parallel plate having a substantially rectangular planar shape. The branch incident unit 133 branches the incident light LA from the light source unit 130 and enters the light guide plate 132. The branch incident part 133 is formed at the center of the upper surface 132 a of the light guide plate 132.

  The branch emission unit 134 emits the branched light from the branch incident unit 133 toward the planar development optical system 20. The branch emission part 134 is formed on the lower surface 132 b of the light guide plate 132. The branch emission unit 134 includes a first branch emission unit 134A, a second branch emission unit 134B, a third branch emission unit 134C, and a fourth branch emission unit 134D. Each branch emission part 134A-134D is formed in the four corners of the lower surface 132b of the light-guide plate 132, respectively.

  In this embodiment, the branch incident part 133 is comprised from the reflection type volume HOE. Specifically, the branch incident unit 133 includes a red incident HOE layer 133R corresponding to the laser light LR in the red wavelength band of the incident light LA, and a green incident corresponding to the laser light LG in the green wavelength band of the incident light LA. The HOE layer 133G for use and the blue incident HOE layer 133B corresponding to the laser light LB in the blue wavelength band of the incident light LA are sequentially stacked from above.

The red incident HOE layer 133 </ b> R satisfies the Bragg diffraction condition and diffracts the laser light LR in the red wavelength band perpendicularly incident from the light source unit 130 at an angle greater than the critical angle in the light guide plate 132.
The green incident HOE layer 133 </ b> G satisfies the Bragg diffraction condition and diffracts the laser light LG in the green wavelength band perpendicularly incident from the light source unit 130 at an angle greater than the critical angle in the light guide plate 132.
The blue incident HOE layer 133 </ b> B satisfies the Bragg diffraction condition and diffracts the laser light LB in the blue wavelength band perpendicularly incident from the light source unit 130 at an angle greater than the critical angle in the light guide plate 132.

  Each incident HOE layer 133R, 133G, 133B has a lattice period of each HOE so that the respective laser beams LR, LG, LB are diffracted at the same angle. Since each HOE satisfies the Bragg diffraction condition for the corresponding wavelength, the diffraction efficiency is almost zero with respect to light of a wavelength that is so far away as to have a different color, and diffracted light is not generated. For example, the laser beam LB reaches the red incident HOE layer 133R without being diffracted by the red incident HOE layer 133R and the green incident HOE layer 133G, and is diffracted there.

  The light propagating through the light guide plate 132 by total reflection is diffracted by each of the branch emitting portions 134 </ b> A to 134 </ b> D and taken out of the light guide plate 132. Each of the branch emission portions 134A to 134D is also laminated with a red emission HOE layer, a green emission HOE layer, and a blue emission HOE layer. Any of the outgoing HOE layers is made of a reflective volume HOE.

  The first branch emission part 134A, the second branch emission part 134B, the third branch emission part 134C, and the fourth branch emission part 134D have a red emission HOE layer, a green emission HOE layer, and a blue emission HOE layer from above, respectively. It has a stacked structure.

  Hereinafter, the red emission HOE layers of the first branch emission unit 134A, the second branch emission unit 134B, the third branch emission unit 134C, and the fourth branch emission unit 134D are collectively referred to as a red emission HOE layer 134RR, which is green. The emission HOE layer is generically called a green emission HOE layer 134GG, and the blue emission HOE layer is generically called a blue emission HOE layer 134BB.

  The laser beams LR, LG, and LB propagated through the light guide plate 132 are diffracted by the red emission HOE layer 134RR, the green emission HOE layer 134GG, and the blue emission HOE layer 134BB, respectively.

The grating periods of the red incident HOE layer 133R and the red outgoing HOE layer 134RR are the same, and the in-layer inclination of the interference fringes recorded in the HOE layer is mirror-symmetric between the incident HOE and the outgoing HOE. Yes.
The grating periods of the green incident HOE layer 133G and the green outgoing HOE layer 134GG are the same, and the in-layer inclination of the interference fringes recorded in the HOE layer is mirror-symmetric between the incident HOE and the outgoing HOE. It has become.
Similarly, the grating periods of the blue incident HOE layer 133B and the blue outgoing HOE layer 134BB are the same, and the in-layer inclination of the interference fringes recorded in the HOE layer is mirror-symmetric between the incident HOE and the outgoing HOE. It has become.

  Accordingly, each of the laser beams LR, LG, and LB is emitted from the branch emitting unit 134 at the same angle as the incident angle incident on the branch incident unit 133, and is extracted from the light guide plate 132 as the branched light LA 'with high diffraction efficiency.

  Further, since each laser beam LR, LG, LB propagates through the light guide plate 132 at the same angle, the position where it is diffracted and taken out by the branch emission unit 134 is also the same, and the deviation of the emission position by color, that is, the occurrence of color unevenness Can be suppressed.

  The four lights emitted from the branch emission parts 134A to 134D are incident on the four corners of the planar development optical system 20B in plan view. The difference between the planar development optical system 20B of this embodiment and the planar development optical system 20 of the above embodiment is that the first light guide optical system 21B is formed by stacking HOE layers corresponding to the laser beams LR, LG, and LB. The second light guide optical system 22B and the third light guide optical system 23B are configured with respective light incident portions and light output portions.

  The laser light LR, LG, and LB at the light incident portions and the light exit portions of the first light guide optical system 21B, the second light guide optical system 22B, and the third light guide optical system 23B in the planar development optical system 20B. Since the behavior (propagation by diffraction and total reflection) is the same as that of the branching optical system 135, description thereof is omitted.

  In each light emitting part (the first light emitting part 13, the second light emitting part 16, and the third light emitting part 19), it is necessary to diffract the RGB three colors of laser light. If a layer is required, a total of six HOE layers are required. Therefore, if two interference fringes are recorded in multiple recording so that the total reflection propagating light coming from two directions can be diffracted in one HOE layer, three HOE layers are sufficient.

  According to the illuminating device 100B of the present embodiment, incident light including laser beams LR, LG, and LB having different wavelength bands is developed in a planar shape in the x direction and the y direction, and white illumination having a uniform intensity distribution. Light can be generated.

  The branching optical system 135 of this embodiment has a configuration in which a single light guide plate 132 is stacked with HOE layers corresponding to light of each color of RGB. However, a single light guide plate 132 has a single layer of HOE layer corresponding to one color. It is also possible to prepare the formed colors for each of the RGB colors and use the three light guide plates 132 in an overlapping manner.

Alternatively, two HOE layers corresponding to two colors are stacked on one light guide plate 132, and an HOE layer corresponding to the remaining one color is formed on another light guide plate 132, and these two light guide plates 132 are formed. A mode in which these are used in an overlapping manner is also possible.
The same applies to each light incident portion and each light emitting portion of the first light guide optical system 21B, the second light guide optical system 22B, and the third light guide optical system 23B.

In the present embodiment, the case where the incident light L from the light source unit 130 is vertically incident on the branch optical system 135 is described as an example, but the present invention is not limited to this. For example, the incident light L from the light source unit 130 may be reflected by a mirror and guided to the branching optical system 135 (see FIG. 6).
According to this configuration, the depth of lighting device 100A can be further reduced.

(Fourth embodiment)
Subsequently, an aspect of the image display device will be described as a fourth embodiment of the present invention.
The image display apparatus according to this embodiment includes the illumination devices 100, 100A, and 100B described in the above embodiment. In the present embodiment, a liquid crystal display device will be described as an example of the image display device.

8A is a view of the liquid crystal display device as viewed from the z direction, and FIG. 8B is a cross-sectional view of the liquid crystal display device in a plane parallel to the xz plane.
As shown in FIGS. 8A and 8B, the liquid crystal display device 50 includes a backlight device 51 and a liquid crystal panel (light modulation device) 52.

  The liquid crystal panel 52 includes a pair of substrates 53, 54, a pair of electrodes 55, 56 provided on the substrates 53, 54, and a liquid crystal layer 57 sandwiched between the pair of substrates 53, 54. It is a transmissive panel. In addition, a pair of polarizing plates is disposed on the surface of the pair of substrates 53 and 54 opposite to the liquid crystal layer 57.

  Based on such a configuration, the liquid crystal panel 52 can modulate the light applied from the backlight device 51 by adjusting the voltage applied between the pair of electrodes 55 and 56 and display a desired image. ing.

The backlight device 51 may be configured using any of the lighting devices 100, 100A, and 100B described in the above embodiment, but a color image can be displayed by using the lighting device 100B. When displaying a color image, the liquid crystal panel 52 includes a color filter for each pixel.
The illumination device 100B can perform color display in time sequence by sequentially turning on the semiconductor lasers 130R, 130G, and 130B (see FIG. 7) of each color.

  According to the liquid crystal display device 50 of the present embodiment, since the liquid crystal panel 52 is illuminated by the backlight device 51 including the illumination devices 100, 100A, 100 as described above, bright image display can be performed.

  By the way, since the laser light emitted from the backlight device 51 including the illumination device 100B becomes substantially parallel light, when the liquid crystal panel 52 is illuminated as it is, an image can be seen only from the front, and the liquid crystal panel 52 is tilted. When viewed from above, light (laser light) does not enter the viewer's eyes and the image cannot be viewed. That is, sufficient viewing angle characteristics may not be obtained.

In order to improve the viewing angle characteristics so that an image can be seen even when the liquid crystal panel 52 is viewed from an oblique direction, it is necessary to convert parallel laser light into light having an angular distribution.
Therefore, the diffusibility of light emitted from the backlight device 51 (illuminating device 100B) may be adjusted by inserting a light diffusion sheet between the backlight device 51 and the liquid crystal panel 52.

In addition, as shown in FIG. 9, the light diffusibility can be adjusted by arranging a lens array RA between the backlight device 51 and the liquid crystal panel 52. The lens array RA includes small lenses RA1 arranged in a matrix. In the lens array RA, each small lens RA1 corresponds to each outgoing beam from the backlight device 51.
According to this configuration, since each outgoing beam is converted into an angled state, the light transmitted through the liquid crystal panel 52 is emitted as diffused light. Therefore, the viewing angle characteristics in the liquid crystal panel 52 are improved.

  Further, the light diffusing sheet may be vibrated with a minute amplitude in order to reduce speckle noise caused by using laser light having high coherence. Or you may make it change the incident angle of the laser beam which injects into the light-guide plate of the backlight apparatus 51 minutely.

(Fifth embodiment)
Subsequently, another aspect of the image display device will be described as a fifth embodiment of the present invention.
The image display apparatus according to this embodiment includes the illumination devices 100, 100A, and 100B described in the above embodiment. The image display apparatus according to the present embodiment is an example of a head mounted display that is used by a user wearing on the head.
In the following description, a head mounted display is abbreviated as HMD.

  The HMD of this embodiment is a see-through type (transmission type) HMD. According to the HMD of the present embodiment, the user can visually recognize the image generated by the image display unit, and can also visually recognize an external image such as a scenery outside the HMD.

FIG. 10 is a diagram showing a cross-sectional configuration of the HMD.
As shown in FIG. 10, the HMD 60 includes a display module 61, a projection lens 62, a light guide plate 63, an image light incident unit 64, and an image light output unit 65. In the present embodiment, the light guide plate 63, the image light incident part 64, and the image light emission part 65 correspond to “light guide means” in the claims.

  The display module 61 includes, for example, the liquid crystal display device 50 according to the fourth embodiment. The display module 61 is not limited to a transmissive liquid crystal display device as long as it includes the illuminating devices 100, 100A, and 100B as the illuminating device, and has a configuration including a reflective liquid crystal display device and the like. May be.

  The projection lens 62 guides the image light G <b> 1 from the display module 61 to the image light incident portion 64 formed on the light guide plate 63. The light guide plate 63 is made of, for example, a glass substrate. The image light incident unit 64 diffracts the image light G <b> 1 from the display module 61 as light propagating at an angle greater than the critical angle of the light guide plate 63.

  In the present embodiment, the image light incident unit 64 and the image light output unit 65 are configured by a diffractive optical element, for example, a reflective volume HOE layer.

  The image light G1 propagated through the light guide plate 63 is incident on the image light emitting portion 65 a plurality of times, and is diffracted at the same angle as the incident angle to the image light incident portion 64 and reaches the eye ME of the observer M each time it enters. It can be observed as an image (virtual image).

  The image light emitting unit 65 composed of the reflective volume HOE strongly diffracts light in the vicinity of the wavelength satisfying the Bragg diffraction condition and transmits light of other wavelengths without being diffracted. Therefore, the observer M is in front of the eye ME. The external environment can be seen through the image light emitting portion 65 located in the area. In the present embodiment, the image light emitting unit 65 functions as a combiner.

  According to this embodiment, since the liquid crystal display device 50 that performs bright image display by including the illumination devices 100, 100A, and 100B as described above is employed in the display module 61, a bright image (virtual image) can be seen. In addition, an HMD having high see-through performance can be provided.

In the present embodiment, an example in which the image of the display module 61 is guided to the eye ME of the observer M using the light guide plate 63, the image light incident unit 64, and the image light emitting unit 65 is described as an example. In addition, the optical combiner 70 may be disposed in front of the eye ME of the observer M.
The optical combiner 70 includes a reflective volume holographic optical element (reflective volume HOE).

According to the configuration of this embodiment, since the eyepiece optical system in front of the eye ME of the observer M is only the thin optical combiner 70, the HMD can be reduced in size and weight.
Further, since the reflective volume HOE is used as the optical combiner 70, only the light in the wavelength band that generates the image light G1 is diffracted with high efficiency and the external light G2 in the wavelength band other than the image light G1 is almost transmitted, so that the light is bright. A see-through HMD capable of displaying a bright image superimposed on the outside can be provided.

  In addition, although this embodiment demonstrated the head mounted display for one eye, it is applicable also to the head mounted display for both eyes.

(Sixth embodiment)
Next, one aspect of the projector will be described as the sixth embodiment of the invention.
FIG. 12 is a schematic configuration diagram of the projector according to the present embodiment.
As shown in FIG. 12, the projector 1 of the present embodiment is a projection type image display device that displays a color image on a screen SCR.

The projector 1 includes an illumination device 2, a color separation optical system 3, a red light modulation device 4R, a green light modulation device 4G, a blue light modulation device 4B, a combining optical system 5, and a projection. And an optical system 6.
The illumination device 2 emits white illumination light WL toward the color separation optical system 3. As the lighting device 2, the lighting device 100B according to the third embodiment is used.

  The color separation optical system 3 separates the illumination light WL emitted from the illumination device 2 into red light R, green light G, and blue light B. The color separation optical system 3 includes a first dichroic mirror 7a, a second dichroic mirror 7b, a first reflection mirror 8a, a second reflection mirror 8b, a third reflection mirror 8c, and a first A relay lens 9a and a second relay lens 9b are provided.

  The first dichroic mirror 7a has a function of separating the illumination light WL emitted from the illumination device 2 into red light R, green light G, and blue light B. The first dichroic mirror 7a transmits red light R and reflects green light G and blue light B. The second dichroic mirror 7b has a function of separating the light reflected by the first dichroic mirror 7a into green light G and blue light B. The second dichroic mirror 7b reflects green light G and transmits blue light B.

  The first reflecting mirror 8a is disposed in the optical path of the red light R. The first reflection mirror 8a reflects the red light R transmitted through the first dichroic mirror 7a toward the light modulator 4R for red light. The second reflection mirror 8b and the third reflection mirror 8c are disposed in the optical path of the blue light B. The second reflection mirror 8b and the third reflection mirror 8c reflect the blue light B transmitted through the second dichroic mirror 7b toward the blue light modulation device 4B. The green light G is reflected by the second dichroic mirror 7b and proceeds toward the green light modulation device 4G.

  The first relay lens 9a and the second relay lens 9b are disposed on the light emission side of the second dichroic mirror 7b in the optical path of the blue light B. The first relay lens 9a and the second relay lens 9b compensate for the optical loss of the blue light B caused by the optical path length of the blue light B being longer than the optical path lengths of the red light R and the green light G. It has a function.

  The light modulator 4R for red light modulates the red light R according to image information, and forms image light corresponding to the red light R. The green light modulation device 4G modulates the green light G according to the image information, and forms image light corresponding to the green light G. The blue light light modulation device 4B modulates the blue light B according to the image information to form image light corresponding to the blue light B.

  For example, a transmissive liquid crystal panel is used for the light modulator for red light 4R, the light modulator for green light 4G, and the light modulator for blue light 4B. A pair of polarizing plates (not shown) are disposed on the incident side and the emission side of the liquid crystal panel. The polarizing plate transmits linearly polarized light in a specific direction.

  A field lens 110R is arranged on the incident side of the red light light modulation device 4R. A field lens 110G is arranged on the incident side of the green light modulator 4G. A field lens 110B is disposed on the incident side of the blue light modulator 4B. The field lens 110R collimates the red light R incident on the red light light modulation device 4R. The field lens 110G collimates the green light G incident on the green light modulator 4G. The field lens 110B collimates the blue light B incident on the blue light light modulation device 4B.

  The combining optical system 5 combines the image light corresponding to each of the red light R, the green light G, and the blue light B, and emits the combined image light toward the projection optical system 6. For example, a cross dichroic prism is used for the combining optical system 5.

  The projection optical system 6 includes a projection lens group including a plurality of projection lenses. The projection optical system 6 enlarges and projects the image light combined by the combining optical system 5 toward the screen SCR. As a result, an enlarged color image is displayed on the screen SCR.

  According to the projector 1 of the present embodiment, a bright image can be projected by providing the illumination device 100B.

  In the sixth embodiment, the projector 1 including the three light modulation devices 4R, 4G, and 4B is exemplified. However, the projector 1 can be applied to a projector that displays a color image with one light modulation device. Furthermore, the light modulation device is not limited to the above-described liquid crystal panel, and for example, a digital mirror device can be used.

  As shown in FIG. 13, a projector 1A that directly illuminates one liquid crystal panel (light modulation device) 52 with one illumination device 100, 100A, 100B and displays an image on the screen SCR with the projection optical system 6 is provided. It can also be configured. Note that when the illumination devices 100 and 100A that irradiate monochromatic light are used, it is not necessary to provide a color filter for the pixels of the liquid crystal panel 52. However, when the illumination device 100B that irradiates three colors of light is used, A color image can be displayed by providing a color filter in the pixel.

  Alternatively, as shown in FIG. 14, illumination devices 300R, 300G, and 300B that respectively irradiate RGB illumination light and liquid crystal panels 52R, 52G, and 52B that are provided individually corresponding to the illumination devices 300R, 300G, and 300B, respectively. In addition, the projector 1B including the combining optical system 5 and the projection optical system 81 can be configured. The illumination devices 300R, 300G, and 300B have the same configuration as the illumination devices 100 and 100A described above, and differ only in the wavelength band of light to be irradiated. Note that no color filter is provided for each pixel of the liquid crystal panels 52R, 52G, and 52B.

The projector 1B combines the image lights Gr, Gg, and Gb modulated by the liquid crystal panels 52R, 52G, and 52B by the combining optical system 5, and projects the color image KG onto the screen SCR.
According to the projector 1B according to the present modification, a higher resolution image can be projected than when a color image is projected by providing a color filter on a single liquid crystal panel, and it is brighter by using laser light. An image can be projected.

  In the above embodiment, an example in which the illumination device according to the present invention is mounted on a projector or a liquid crystal display device is shown, but the present invention is not limited to this. The lighting device according to the present invention can also be applied to lighting fixtures, automobile headlights, and the like.

  DESCRIPTION OF SYMBOLS 1,1A, 1B ... Projector, 2 ... Illuminating device, 4B ... Light modulation device for blue light, 4G ... Light modulation device for green light, 4R ... Light modulation device for red light, 6 ... Projection optical system, 10, 10A, DESCRIPTION OF SYMBOLS 10B ... Light source, 11 ... 1st light-guide plate, 11a ... Lower surface, 12 ... 1st light incident part, 13 ... 1st light-projection part, 14 ... 2nd light-guide plate, 14a ... Upper surface, 15 ... Light-incidence part, 16 ... 2nd light emission part, 17 ... 3rd light guide plate, 17a ... Upper surface, 18 ... Light incident part, 19 ... 3rd light emission part, 20, 20B ... Planar deployment optical system, 21, 21B ... 1st light guide optics System 22, 22, 22B ... 2nd light guide optical system, 23, 23B ... 3rd light guide optical system, 32 ... 4th light guide plate (light guide member), 33 ... Branch entrance part, 34 ... Branch exit part, 35 ... Branch optical system, 50 ... Liquid crystal display device (image display device), 51 ... Backlight device (illumination device), 52, 52R, 2G, 52B ... Liquid crystal panel (light modulation device), 60 ... HMD (image display device), 63 ... Light guide plate, 70 ... Optical combiner, 81 ... Projection optical system, 100, 100A, 100B ... Illumination device, 130G ... Semiconductor laser , 130R ... semiconductor laser, 132 ... light guide plate, 133 ... branch incident part, 135 ... branch optical system, 200 ... illumination device, 210 ... light source, 220 ... planar development optical system, 221, 222 ... light guide optical system, 300R , 300G, 300B ... lighting device, G1 ... image light, Gr ... image light, KG ... color image, L1H ... illumination light, L1c ... light, L1e ... light, L1f ... light, L1h ... light, L2b ... light, LB ... Laser light, LC ... branching light, LG ... laser light, LL1, LL2 ... emitted light, LL ... incident light, LR ... laser light, M ... observer, ME ... eye, R ... red light, G ... green Light, B ... blue light, SCR ... screen, WL ... illumination light, G1 ... image light.

Claims (15)

A first light guiding optical system that expands incident light in a first direction and emits the light from the first light emitting unit;
A second light guiding optical system that expands incident light in a second direction intersecting the first direction and emits the light from the second light emitting unit, and
The first light guide optical system includes a first light incident portion provided at one end portion and a second light incident portion provided at the other end portion opposite to the one end portion. And comprising
The second light guide optical system is optically connected to the first light guide optical system;
The first light guiding optical system is an optical system in which both the light incident on the first light incident portion and the light incident on the second light incident portion are enlarged and emitted from the first light emitting portion. An optical element characterized by the above. A third light guiding optical system for expanding the incident light in the second direction and emitting the light from the third light emitting unit;
The second light guide optical system is arranged so that light emitted from the second light emitting part is incident on the first light incident part,
2. The optical element according to claim 1, wherein the third light guide optical system is disposed so that light emitted from the third light emitting unit is incident on the second light incident unit. 3. The second light guide optical system receives light from both ends of the second light guide optical system,
The optical element according to claim 2, wherein the third light guide optical system receives light from both ends of the third light guide optical system. 4. The optical element according to claim 1, wherein each of the first light incident part and the first light emitting part includes a reflective volume holographic optical element. 5. The period of the interference fringes of the reflection type volume holographic optical element of the first light incident part is provided to be the same period as the period of the interference fringes of the reflection type volume holographic optical element of the first light emitting part. The optical element according to claim 4. The in-layer inclination of the interference fringes of the reflective volume holographic optical element of the first light incident portion is the relationship between the in-layer inclination of the interference fringes of the reflective volume holographic optical element of the first light emitting portion and the specular object. The optical element according to claim 4, wherein the optical element is provided. An optical element according to claim 1;
A light source that emits light to each of the first light incident part and the second light incident part,
The lighting device according to claim 1, wherein the first light guide optical system is arranged such that light emitted from the first light emitting unit is incident on the second light guide optical system. An optical element according to claim 2 or 3,
A light source that emits light to each of the second light guide optical system and the third light guide optical system;
A lighting device comprising: The light source includes a branching optical system that branches light;
The branch optical system is:
A light guide member;
A branch incident part for branching light to enter the light guide member;
A branch emission part for emitting the branched light incident from the branch incident part toward the optical element;
The lighting device according to claim 7 or 8, wherein The light guide member is rectangular in plan view,
The lighting device according to claim 9, wherein the branch incident unit branches light so that the branched light travels toward the four corners of the light guide member in plan view. The illumination device according to claim 9, further comprising a mirror that reflects light and guides the light to the branching optical system. The lighting device according to any one of claims 7 to 11,
A light modulation device for modulating illumination light from the illumination device;
An image display device comprising: The image display device according to claim 12, further comprising a light guide unit that guides image light modulated by the light modulation device to an eye of an observer. The image display apparatus according to claim 13, wherein the light guiding unit includes a reflective volume holographic optical element. The lighting device according to any one of claims 7 to 11,
A light modulation device that forms image light by modulating light from the illumination device according to image information; and
A projector comprising: a projection optical system that projects the image light.