Lighting device, display device, control device, control method, and program

Abstract

To provide a lighting device with minimal variation in luminance distribution. [Solution] The lighting device (1) includes a light guide unit (20) that guides light from a light source unit (10) to a display element (30), and a control unit (71) that controls the display element (30). The light guide unit (20) includes a plurality of branching surfaces (21a to 21e) that branch the light from the light source unit (10), and the control unit (71) changes the light utilization efficiency for each position of the display element (30) to reduce variations in the brightness distribution due to the plurality of branching surfaces (21a to 21e).

Description

Technical Field

[0006]

[0001] The present invention relates to a lighting device, a display device, a control device, a control method, and a program.

Background Art

[0002] Patent Document 1 discloses an optical device including a beam splitter having a plurality of branching portions.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A lighting device with less variation in luminance distribution is desired.

Means for Solving the Problems

[0005] A lighting device according to one aspect of the present invention includes a light guide unit that guides light from a light source unit to a display element, and a control unit that controls the display element. The light guide unit includes a plurality of branching surfaces that branch light from the light source unit, and the control unit changes the light utilization efficiency for each position of the display element so as to reduce the variation in luminance distribution caused by the plurality of branching surfaces.

Effects of the Invention

[0006] According to the present invention, a lighting device with less variation in luminance distribution can be provided.

Brief Description of the Drawings

[0007] [Figure 1] It is a configuration diagram of a display device in the first embodiment. [Figure 2]This is a diagram showing the configuration of the light source unit in the first embodiment. [Figure 3] This is a diagram showing the configuration of the illumination light guide unit in the first embodiment. [Figure 4] This figure shows a perspective view of the beam splitter in the first embodiment and a diagram of the optically symmetrical plane U. [Figure 5] This figure shows the region on the display element in the first embodiment where reflected light from the branching surface reaches. [Figure 6] This figure shows the illumination light in the first embodiment. [Figure 7] This figure shows the illumination light in the first embodiment. [Figure 8] This figure shows the illumination light in the first embodiment. [Figure 9] This figure shows the illumination light in the first embodiment. [Figure 10] This figure shows the brightness distribution of the display element in the first embodiment. [Figure 11] This figure shows the brightness of the display element in the H-H' cross-section in the first embodiment. [Figure 12] This figure shows the optical efficiency (H-H' cross-section of the display element) in the first embodiment. [Figure 13] This figure shows the V-V' cross-sectional brightness of the display element in the first embodiment. [Figure 14] This figure shows the optical efficiency (V-V' cross-section of the display element) in the first embodiment. [Figure 15] This figure shows the illumination area of ​​the display element in the first embodiment. [Figure 16] This figure shows the Vk-Vk' (k=a, b, c, d, e) cross-sectional brightness of the display element in the first embodiment. [Figure 17] This figure shows the region where the brightness change of the display element is large in the first embodiment. [Figure 18] This figure shows a beam splitter in the second embodiment. [Figure 19] This figure shows a perspective view of the beam splitter in the second embodiment and a diagram of the optically symmetrical plane U. [Figure 20] It is a diagram showing a beam splitter in the third embodiment. [Figure 21] It is a perspective view of a beam splitter in the third embodiment and a diagram showing an optically symmetric plane U. [Figure 22] It is a diagram showing the relationship between the angular field and the reflectance of a region in the third embodiment. [Figure 23] It is a luminance cross-sectional view on the display element side in the third embodiment.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0009] (First Embodiment) First, referring to FIG. 1, the display device 1 in the first embodiment of the present invention will be described. FIG. 1 is a configuration diagram of the display device 1. The display device 1 includes a light source unit 10, an illumination light guide unit (light guide unit) 20, a display element 30, a projection unit (projection system) 40, and an image light guide unit 50. The image shown by the display element 30 enters the pupil 61 of the user's eye 60 and is projected onto the retina surface 62. In this embodiment, the display device 1 is composed of the light source unit 10, the illumination light guide unit 20, the display element 30, and the projection unit 40. The display device 1 projects image light emitted from the display element 30 by illuminating the display element 30 (the dotted line 1000 in FIG. 1 indicates a representative optical path from the light source unit 10).

[0010] FIG. 2 is a configuration diagram of the light source unit 10. The display device 1 shapes the light from the light source unit 10 by the illumination light guide unit 20 and illuminates the display element 30. The light source unit 10 includes a light source 11 such as a laser or an LED, a collimator lens 12 that collimates the light source 11, a diffuser (diffusion plate) 13 that spreads the collimated light to a desired divergence angle, and a polarizer 14.

[0011] The light source 11 is composed of three or more wavelengths of light, including red (R), green (G), and blue (B), and can be combined to form white light. However, this embodiment is not limited to this, and may be a light source that combines light sources having emission wavelengths of each wavelength, or a light source that has multiple light-emitting surfaces on a single light-emitting chip. For example, it may be a laser light source having each of the RGB light-emitting surfaces, and the light may be combined within the chip by waveguides or multiplexing prisms to produce a single output. Alternatively, it may be a light source having multiple light-emitting surfaces of a specific color, depending on the luminous efficiency, for example, a light source having one R, two G, and one B light-emitting surface.

[0012] The collimator lens 12 is a lens that approximately parallelizes the light from the light source 11, illuminates the subsequent diffuser 13, and diffuses and illuminates the light at a desired angle after the diffuser 13. The diffuser 13 diffuses the approximately parallelized light to a desired divergence angle, forming the illumination light necessary for the subsequent optical system. The diffuser 13 is not essential and may be omitted if there is sufficient etendum for illumination, such as when the light-emitting surface of the light source 11 is large. The polarizer 14 is configured to produce light with a specific polarization direction in the subsequent stage and to become S-polarized when it reaches the beam splitter described later. However, if the polarization direction has been adjusted in advance using a laser light source, the polarizer 14 may be omitted.

[0013] As described later, the illumination light guide unit 20 projects (guides) light from the light source unit 10 to the display element 30. The display element 30 is, for example, a reflective display element (reflective LCOS: Liquid crystal on silicon), but a transmissive display element (transmissive LCOS) or a DMD (Digital Micromirror Device) may also be used. The display element 30 is an element capable of displaying a two-dimensional image. The image light formed by the illuminated display element 30 is parallelized by the projection unit 40 and incident on the image light guide unit 50.

[0014] The image light guide unit 50 is a light guide plate having an input unit 51 and an output unit 52. The input unit 51 guides the image light from the projection unit 40 into the light guide plate, guides the image light while totally reflecting it within the light guide plate, and outputs the image light in the direction of the user's eye 60 using the output unit 52.

[0015] The input unit 51 may be configured as a reflective mirror within the image light guide unit 50, or it may be configured as a microstructure such as a diffraction grating, hologram, or metasurface. The output unit 52, as shown in Figure 1, is configured as a group of partial reflective mirrors within the image light guide unit 50 and outputs the replicated image light toward the human eye. The output unit 52 may consist of multiple partial reflective mirrors, or it may consist of a microstructure such as a diffraction grating or metastructure, and it has the role of deflecting the image light toward the human eye. In addition, although the output unit 52 is composed of multiple mirrors so that projection can be made even when the user's eye 60 is turned to the other side, it may also be an optical unit with a single deflection output function. With this configuration, the image light output from the display element 30 can be projected onto the retinal surface 62 of the user's eye 60.

[0016] The processing unit 70 is a control device that controls the lighting device and includes a control unit 71 and a memory unit 72. The memory unit 72 stores data on the optical efficiency (light utilization efficiency) of the display element 30 to reduce variations in the luminance distribution (luminance unevenness) in the user's eye. The control unit 71 uses the data stored in the memory unit 72 (by acquiring data from the memory unit 72) to change the optical efficiency of the display element 30 at each display position to reduce variations in the luminance distribution. In other words, the control unit 71 changes the optical efficiency of the display element 30 at each display position to reduce variations in the luminance distribution caused by the multiple branching surfaces of the illumination light guide unit 20.

[0017] The data stored in the memory unit 72 is, for example, data relating to the brightness distribution obtained by inverting the brightness distribution obtained by imaging the user's eye using an imaging device (not shown). The control unit 71 uses this data to invert the brightness distribution of the user's eye, thereby changing the optical efficiency so that the brightness distribution of the user's eye becomes constant. The optical efficiency of the display element 30 is the transmittance if the display element 30 is a transmissive display element, and the reflectance if the display element 30 is a reflective display element. Alternatively, if the display element 30 is an element such as a DMD that includes multiple reflective surfaces, the control unit 71 changes the optical efficiency by driving the multiple reflective surfaces. In this case, the optical efficiency is, for example, the time ratio between the on state and the off state of the display element 30.

[0018] Next, the illumination light guide unit 20 will be described in detail with reference to Figure 3. Figure 3 is a diagram of the configuration of the illumination light guide unit 20. The illumination light guide unit 20 is composed of a beam splitter 21 having multiple beam splitter surfaces, a λ / 4 wave plate 22, and a polarizer 23. The beam splitter 21 has multiple branching surfaces 21a to 21e that split the light beam. Each of the branching surfaces 21a to 21e is a polarizing beam splitter, which reflects S-polarized light at a certain rate while transmitting P-polarized light. The branching surfaces 21a to 21e are composed of dielectric multilayer films, diffraction elements, or holograms, etc.

[0019] Light from the light source unit 10 enters the beam splitter 21 from the surface 21A, is partially reflected at the branching surface 21a, passes through the λ / 4 wave plate 22, and illuminates the display element 30 as circularly polarized light.

[0020] Light transmitted through the branching surface 21a is partially reflected by the branching surface 21b, passes through the λ / 4 wave plate 22, and illuminates the display element 30 as circularly polarized light. Light transmitted through the branching surface 21b is subsequently reflected by the subsequent branching surface in the same manner as the branching surface 21a described above, and illuminates the display element 30.

[0021] The dotted line 1000 represents a typical light. This light replicates five illumination lights at the five branching surfaces of the beam splitter and is sent to the projection unit 40 as five image lights. It is desirable that the reflected light from the branching surfaces 21a to 21e uniformly illuminates the display element 30. For example, if the reflectances of the branching surfaces 21a to 21e are 1 / 5 (=20%), 1 / 4 (=25%), 1 / 3 (=33%), 1 / 2 (=25%), and 1 (=100%), respectively, the illumination light from each surface will be equal.

[0022] The illumination light that lights up the display element 30 is reflected by the display element 30, passes through the λ / 4 wave plate 22, and mostly becomes P-polarized before reaching the beam splitter 21. It then passes through the branching surfaces (polarization branching surfaces) 21a to 21e, and only the P-polarized light passes through the polarizer 23 before reaching the projection unit 40.

[0023] The polarizer 23 has the role of blocking unwanted light, such as ghosting, from an optical path other than the optical path described above. Since the aforementioned optical path is P-polarized while unwanted light is often not P-polarized, the polarizer 23 can make the display of the required projected light clearer, but it can be omitted depending on the specifications of the optical system.

[0024] Incidentally, the beam splitter 21 has a plane U that is symmetrical in terms of its optical properties. Figure 4 is a perspective view of the beam splitter 21 and a diagram showing the optically symmetrical plane U. In Figure 4, plane U' shows a cross-section of the illumination light guide section 20 and plane U. The branching planes 21a to 21e are arranged along the intersection axis X' on plane U'.

[0025] On the display element 30, the light reflected from the branching surfaces 21a to 21e has regions 31a to 31e where each reflected light is in close proximity. Figure 5 shows the regions on the display element 30 to which the reflected light from the branching surfaces 21a to 21e reaches. On the display element 30, the reflected light from the branching surfaces 21a to 21e overlaps if the branching surfaces are close to each other, and does not overlap if the branching surfaces are far apart.

[0026] Here, the light reflected from the branching surfaces 21a to 21e is not just unidirectional light as shown in Figure 3, but is diffused light. This light is incident on surface 21A of the beam splitter 21, undergoes total internal reflection within the beam splitter 21, and is then split into multiple beams at the branching surfaces 21a to 21e. Therefore, the light reflected at the branching surfaces 21a to 21e includes light that arrives directly from the incident surface 21A and light that has been reflected from the side surface 21B or side surface 21C.

[0027] Figure 6 shows the illumination light as viewed from the display element 30. The λ / 4 wave plate 22 is omitted here. Also, for the sake of simplicity, the tangents to each branching surface on surface 21C and the tangents to each branching surface on surface 21B are positioned to coincide as viewed from the display element. That is, the thickness of the beam splitter, which is the distance between surface 21B and surface 21C, is assumed to be equal to the distance between each branching surface in the X direction.

[0028] In the field of view 32a in Figure 6, the light La from the beam splitter 21 is reflected by the branching surface 21a. In the field of view 32a, not only light parallel to the X-axis from the light source is illuminated, but also light focused into region 31a. Among these, the light within the angle θ range that will later be projected by the projection unit 40 is important, and light with a greater inclination is blocked by the projection unit 40. For this reason, the following description will focus on the light with an angle θ within the range that can be captured by the projection unit 40.

[0029] Next, we will describe the illumination light at other angles of view, using the light illuminating within the angle θ range as a reference. When viewing the beam splitter 21 from the angle of view 32bc on the display element 30, the intersection line with the branching surface 21c on surface 21B coincides with the intersection line with the branching surface 21b on surface 21C. At angle of view 32bc, there are two types of light from the beam splitter 21: light Lb and light Lc from the light source side. Light Lb is reflected by surface 21b, and light Lc from the opposite side of the light source is reflected by surface 21c. As described above, the amount of light reflected from each branching surface is the same because the reflectivity of each surface is appropriately determined, so the amounts of light Lc and light Ld are the same. In other words, the illumination light quantity (luminance) at angles 32a and 32bc within the angle θ range is equal.

[0030] Next, we focus on the field of view 32c, which is on the light source side near the field of view 32cd. The light illuminating the field of view 32c can be divided into three types of light. The first is reflected light Lc1 (Figure 8(a)) which is reflected directly from the incident surface 21A by the branching surface 21c. The second is reflected light Lc2 (Figure 8(b)) which is totally reflected from the incident surface 21A by surface 21C and then reflected by the branching surface 21c. The third is light Ld (Figure 8(c)) which is reflected by the branching surface 21d and transmitted through the branching surface 21c.

[0031] Of these, light Ld is a type of light not present in field of view 32a shown in Figure 6 or field of view 32bc shown in Figure 7. The luminance of field of view 32c is the same as that of field of view 32a and field of view 32bc, but is higher due to illumination by light Ld.

[0032] On the other hand, in the vicinity of field of view 32de, at field of view 32e, which is on the opposite side from the light source 11, the situation is different from that described above (Figure 9). At field of view 32e, only the light reflected by the branching surface 21e is illuminated, but there is no illumination light in the range of angle θ' within the range of angle θ that can be captured by the projection unit 40. This is because the incident angle in the range of angle θ' is small when viewed from surface 21B, and is smaller than the angle at which light incident from surface 21A can be totally reflected, so it is not guided from the incident surface 21A. In other words, the brightness at field of view 32e is less than at field of view 32a and field of view 32bc.

[0033] Up to this point, we have explained the luminance to the display element in terms of the optical path on the XZ cross section. Since the display element 30 is arranged on the XY plane, the luminance to the display element 30 is as shown in Figure 10. Figure 10 is a diagram showing the luminance distribution of the display element 30. As shown in Figure 10, the area of ​​301FT, which has high luminance uniformity, occupies the majority, but there are multiple adjacent areas of 301U with high luminance and 301S with low luminance.

[0034] Next, referring to Figure 11, the luminance distribution in the horizontal direction (H-H' cross-sectional direction) from the center of the field of view shown in Figure 10 will be explained. Figure 11 is a diagram showing the luminance of the display element 30 in the H-H' cross-section. In Figure 11, the horizontal axis represents the horizontal field of view, and the vertical axis represents luminance. High and low luminance areas are adjacent to each other, indicating abrupt changes in luminance. Such changes are observed as lines of light and dark on the screen when viewed with the display device 1. The H-H' cross-sectional direction is the same direction as the intersection axis X' of the illumination light guide unit 20.

[0035] As shown in Figure 3, light from the light source 10 enters the beam splitter 21 and is reflected by the branching surfaces 21a to 21e. This light then passes through the λ / 4 wave plate 22, is reflected by the display element 30, passes through the λ / 4 wave plate 22 again, passes through the beam splitter and branching surfaces, and passes through the polarizer 23. Here, the display element 30 is a reflective LCOS as described above, and its phase can be changed depending on the state of the liquid crystal in front of the reflective surface.

[0036] A reflective LCOS is a liquid crystal display panel in which a reflective layer and liquid crystal are formed on a silicon substrate. The silicon substrate side contains a liquid crystal driving circuit and pixel electrodes, and light that passes through the transparent substrate and liquid crystal layer is reflected by the pixel electrodes. The liquid crystal is then driven by the pixel electrodes, and the phase of light is controlled for each pixel.

[0037] When the phase changes, the reflected light from the display element 30 is polarized and separated at the branching surface of the beam splitter 21, so the light transmitted through the branching surface is attenuated. In other words, only P-polarized light is transmitted and S-polarized light is reflected, so the ratio can be changed by the amount that the phase is controlled. Furthermore, since the subsequent polarizer 23 transmits light with aligned phases, only P-polarized light is transmitted through the polarizer 23, and S-polarized components generated by stray light, etc., are blocked.

[0038] Here, for areas with high brightness, such as 301U in Figure 10, the phase of the display element is corrected so that the reflected light from the display element 30 is attenuated before reaching the projection unit. Conversely, for areas with low brightness, such as 301S, the phase of the display element is corrected so that the reflected light from the display element is illuminated before reaching the projection unit.

[0039] Figure 12 shows the optical efficiency of the H-H' cross-section of the display element 30, before and after phase correction, from after beam splitter reflection to after polarizer transmission. In Figure 12, the horizontal axis represents the horizontal field of view, and the vertical axis represents the optical efficiency.

[0040] The dotted line in Figure 12 represents the optical efficiency before phase correction and is constant. That is, the phase of the liquid crystal is controlled to be equal on the H-H' cross section. The solid line in Figure 12 represents the optical efficiency after phase correction and has variations in intensity. This variation is controlled to be inversely related to the luminance ratio of the display element before phase correction. As a result, the luminance on the display element reaching the projection area becomes uniform from H to H'. Also, since there is less luminance change in the direction perpendicular to the H-H' cross section than in the H-H' cross section direction, the phase difference may be determined to be the same as that determined in the H-H' cross section. However, if there is a gradual luminance change in the H-H' cross section direction, separate from the large illuminance change that occurs at the boundary of the branching surface, these may be used as the basis for correction.

[0041] Figure 13 shows a luminance distribution (dotted line) where the luminance changes gradually in the vertical direction (V-V' section) from the center of the field of view, after correcting for areas with large luminance changes in the H-H' section direction. In Figure 13, the horizontal axis represents the vertical field of view, and the vertical axis represents luminance. The distribution shown in Figure 13 is less noticeable and harder to notice than the luminance unevenness (variation in luminance distribution) in the H-H' section mentioned above, because there are no abrupt changes in luminance. However, in scenes where the same color is displayed across the entire screen, the luminance reduction at the edges becomes noticeable.

[0042] Figure 14 shows the optical efficiency (dotted line) of the display element 30 in the V-V' cross-sectional direction, from after beam splitter reflection to after polarizer transmission. In Figure 14, the horizontal axis represents the horizontal field of view, and the vertical axis represents the optical efficiency. The dotted line in Figure 14 is constant, indicating that the phase of the liquid crystal is controlled to be equal in the V-V' cross-sectional direction. Therefore, the phase of the display element 30 is corrected so that the amount of light increases gradually from the display element 30 to the projection unit 40 in the VV' cross-sectional direction.

[0043] The solid line in Figure 14 shows the optical efficiency from beam splitter reflection to polarizer transmission after phase correction, and the solid line in Figure 13 shows the luminance distribution on the display element 30. The strength of the optical efficiency in Figure 14 is controlled to be inversely related to the luminance ratio at the display element before phase correction. As a result, the luminance on the display element 30 reaching the projection unit 40 is uniform from V to V'.

[0044] In this way, by appropriately correcting the abrupt and gradual changes in brightness in the display element 30 for each direction, brightness unevenness (variation in brightness distribution) can be reduced when observed by the user's eye 60. Alternatively, if the gradual change in the H-H' cross-sectional direction is not constant in the V-V' cross-sectional direction, correction in the V-V' direction may be made for each position in the HH' direction.

[0045] In this embodiment, light from the light source is incident on the beam splitter from the incident surface 21A, and the display element 30 is illuminated by the branching surfaces 21a to 21e, but the light illuminating each branching surface has a discretely different optical path length.

[0046] The light reflected from the branching surface 21b illuminates with a longer optical path length than the light reflected from the branching surface 21a, resulting in a wider beam of light. Therefore, the light reflected from the branching surface 21b has lower brightness. Consequently, the brightness change in the V-V' cross-sectional direction of the display element also changes for each branching surface on the illumination optical path. Thus, the brightness change in the VV' cross-sectional direction can be varied for each region.

[0047] Figure 15 shows the illumination area of ​​the display element 30. For example, the areas 301a to 301e on the display element shown in Figure 15 are divided according to which branching surface 21a to 21e reflected in the illumination light path illuminates them, and the subscripts a to e indicate this relationship.

[0048] Figure 16 shows the luminance distribution in the vertical cross-sectional directions Va-Va' to Ve-Ve' sections in regions 301a to 301e. In Figure 16, the horizontal axis represents the vertical field of view, and the vertical axis represents the luminance. For clarity, the figures are exaggerated and the luminance at the central field of view is standardized, but the luminance distribution in the V-direction cross-section differs in each region. In each region 301a to 301e, the optical efficiency in the VV' cross-sectional direction may be discretely varied as explained with reference to Figures 13 and 14.

[0049] As described above, the control unit 71 makes the optical efficiency in the direction perpendicular to the intersection line different from the optical efficiency in the direction along the intersection line. The control unit 71 may make the optical efficiency different in the direction perpendicular to the intersection line, or it may keep the optical efficiency constant in the direction perpendicular to the intersection line.

[0050] Incidentally, the brightness change in the H-H' cross-sectional direction is larger than that in the V-V' cross-sectional direction. Therefore, the H-H' cross-sectional direction may be divided into regions as described above and controlled accordingly. Figure 17 shows regions in which the brightness change of the display element 30 is large. For example, the regions 301ab, 301bc, 301cd, and 301de shown in Figure 17 (multiple regions along the intersection line (axis X')) are regions with large brightness changes, but even controlling the optical efficiency only in these regions is effective in improving brightness uniformity. The number of regions 301ab, 301bc, 301cd, and 301de is less than the number of branching surfaces. Therefore, it is sufficient to control the optical efficiency for each of the multiple regions.

[0051] As described above, by making the optical efficiency of the display element 30 non-constant with respect to the direction of the intersection line (axis X') between the surface U, which has optical properties symmetrical with respect to the illumination light path from the illumination light guide unit 20 to the display element 30, and the display element 30, steep brightness unevenness can be effectively suppressed.

[0052] In this embodiment, an example using a reflective LCOS is shown, but a transmissive LCOS without a reflective surface may also be used. Even when a transmissive LCOS is used according to the specifications of the optical system, brightness unevenness can be reduced in the same way as described above by the control of this embodiment.

[0053] Furthermore, in this embodiment, since the illumination light guide unit 20 and the display element 30 are adjacent to each other, the light rays from the surface U and the display element 30 are set as axis X'. However, depending on the subsequent optical processes, a virtual U surface may be set. For example, if a mirror that bends the optical path by 90 degrees is placed between the illumination light guide unit 20 and the display element 30, there may be no intersection line between the surface U and the display element 30. In this case, it is preferable to set axis X' by assuming an intersection line between the virtual U surface bent by the bending mirror and the display element. In other words, the surface U may be aligned with the optical system from the illumination light guide unit 20 to the display element 30 and aligned with an optically equivalent coordinate system.

[0054] Furthermore, in this embodiment, for the sake of clarity, the spacing between the branching surfaces of the illumination light guide 20 on the intersection axis X' is the same as the thickness of the illumination light guide 20. It is easy to imagine that if this spacing is increased, the areas illuminated by the branching surfaces will be separated, and the brightness of the illumination interface will decrease. Conversely, if this spacing is narrowed, the areas illuminated by the branching surfaces will overlap, and the brightness of the illumination interface will increase.

[0055] In the former case, the brightness of the interface decreases, so brightness uniformity can be improved by reducing the optical efficiency of the uniformly illuminated area. On the other hand, in the latter case, the brightness of the interface increases, so brightness uniformity can be improved by reducing the optical efficiency only in the interface area.

[0056] In this embodiment, the area with large brightness changes at the interface (for example, 301U and 301S in Figure 10) is smaller than the area with high brightness uniformity (for example, 301TF in Figure 10). Therefore, the former, which only dims the light in the narrow area, has higher optical efficiency as an illumination device and lower power consumption. The area of ​​the area with large brightness changes at the interface and the area with high brightness uniformity will vary depending on the configuration and specifications of the optical system. It is desirable to configure the illumination light guide section to reduce power consumption in accordance with the optical configuration.

[0057] Furthermore, as described above, the phase of the reflective LCOS is controlled to improve optical efficiency (Figure 12 or Figure 14), but if the optical efficiency is already controlled to be maximized, it is not possible to further improve the optical efficiency. This embodiment assumes that the phase of the reflective LCOS is controlled in advance so that the upper limit of optical efficiency does not exceed the correction amount. By controlling the optical efficiency of the display element 30 while taking these factors into consideration, it is possible to configure an illumination device that improves brightness uniformity while reducing power consumption.

[0058] (Second Embodiment) Next, with reference to Figure 18, a method for reducing brightness unevenness in the illumination light guide section in a second embodiment of the present invention will be described. Figure 18 shows an illumination light guide section (beam splitter 25) of a different type from that of the first embodiment. The beam splitter 25 has its branching surfaces arranged on the same plane. The beam splitter 25 will be described below along the optical path.

[0059] Region 25Ba is the region into which light from the light source 10 is incident, and is composed of, for example, a general AR coating. Region (branching surface) 25Ca is the region that reflects light incident from the first region, and may be a general metal mirror or a dielectric multilayer film that reflects incident light. Region (branching surface) 25Bb is a region that reflects obliquely incident light while transmitting perpendicular light, and is composed of, for example, a dielectric multilayer film, a diffraction grating, or a metasurface. Regions (branching surfaces) 25Cc and 25Cd are regions that partially transmit obliquely incident light and reflect the rest, and transmit perpendicularly incident light. Region 6 is a region that transmits both obliquely incident light and perpendicularly incident light. The transmittance of region 25Cb is, for example, 1 / 3, and the transmittance of region 25Cc is, for example, 1 / 2. When the light incident on region 25Cb is 1, the light transmitted through regions 25Cb, 25Cc, and 25Cd is all 1 / 3.

[0060] Figure 19 shows a perspective view of the beam splitter 25 and an optically symmetrical plane U. As shown in Figure 19, regions 25Ba and 25Bb are located on plane 25B, and regions 25Ca, 25Cb, 25Cc, and 25Cd are located on plane 25C. The beam splitter 25 has a plane U that is optically symmetrical. Plane U' shows a cross-section of the beam splitter 25 and plane U. Regions 25Ca to 25Cd are located along the intersection axis X' on plane U'.

[0061] The display element 30 is composed of a DMD. The DMD is a display element manufactured using MEMS (Micro-Electro-Mechanical System) technology, and is an element in which a large number of movable tiny mirrors (micromirrors) are arranged in a planar manner. Each tiny mirror has a tilt, and the angle can be switched by the control unit, allowing two patterns of illumination light paths to be formed. That is, an "ON" state (on state) in which it is connected to the subsequent optical system, and an "OFF" state (off state) in which it is disconnected from the subsequent optical system. In other words, by switching the angle in the control unit, in the "ON" state, obliquely incident light from the illumination light guide unit 20 is reflected in a direction perpendicular to the illumination light guide unit 20 and connected to the subsequent optical system.

[0062] In the "OFF" state, obliquely incident light from the illumination light guide 20 is reflected at an angle significantly deviating from the vertical, absorbed by an absorber (not shown), and not connected to the subsequent optical system. By controlling the time length (time ratio) between the "ON" and "OFF" states, the intensity of the projected image can be expressed. The dotted line in Figure 18 represents the optical path in the "ON" state.

[0063] In this embodiment, the beam splitter 25 has multiple important regions in the optical path on surfaces 25B and 25C, each with a coating having different optical properties. Generally, due to manufacturing tolerances, the coatings may be slightly separated or slightly overlapping at the boundaries between the regions. Therefore, the brightness of the display element changes significantly at the boundaries of the regions. The idea behind this change is that light passing near the boundary surface may have a transmittance different from that between the regions, or the transmittance may increase due to a gap. In that case, the brightness of the light that passes near the boundary surface and reaches the display element increases. Alternatively, depending on the manufacturing process, the transmittance may decrease. In that case, the same idea applies as above, and a sharp decrease in brightness occurs at the point where the light passing near the boundary reaches the display element.

[0064] As a result, a striped brightness distribution similar to that of the first embodiment is obtained. These stripes appear perpendicular to the intersection axis X', and the arrangement of the stripes occurs along the intersection axis X'. In this case, the concept is the same as in the first embodiment; the optical efficiency (light utilization efficiency) in areas with large striped brightness changes should be controlled to be uniform with the rest. In the case of DMDs, the uniformity of brightness across the entire field of view can be improved by shortening the "ON" time interval of the display element in areas with high brightness and lengthening the "ON" time interval of the display element in areas with low brightness.

[0065] (Third embodiment) Next, with reference to Figure 20, a method for reducing brightness unevenness in the illumination light guide in the third embodiment of the present invention will be described. Figure 20 shows an illumination light guide (beam splitter 26) of a different type from that of the first and second embodiments. The beam splitter 26 is composed of an incident region 26Ca from the light source 10, a transmissive region 26Cb with a gradient, and a reflective region 26C, and the light emitted from region 26Cb passes through the display element 30 and the polarizer 23. The display element 30 is a transmissive LCOS.

[0066] Figure 21 shows a perspective view of the beam splitter and an optically symmetric plane U. Region 26Cb is a reflective area where the transmittance increases and the reflectance decreases as you move from the -X side to the +X side. However, this reflective area remains constant in the direction perpendicular to the XZ plane (Y-axis direction). The beam splitter 26 has a plane U that is optically symmetric. Plane U' shows a cross-section of the beam splitter 26 and plane U.

[0067] Region 26Bb is configured such that its transmittance and reflectance change along the intersection axis X' on plane U'. That is, the transmittance increases and the reflectance decreases from the LT side to the HT side along the X axis, but remains constant in the Y axis direction. In this case, as shown in Figure 20, the branching point and the display element are not parallel in the optical path diagram viewed from the Y axis direction. In this case, the intensity of optical brightness appears on the intersection line (axis X'') of plane U and the display element 30. Therefore, the cross-sectional brightness distribution of the display element 30 shown later represents the distribution in the cross-section in the direction of axis X''.

[0068] Figure 22 shows the reflectance of region 26Bb from the LT side to the HT side. In Figure 22, the horizontal axis represents the field of view and the vertical axis represents the reflectance. The configuration and concept of this reflectance are the same as in the first embodiment. In this embodiment, as shown in Figure 20, the illumination light is branched into four beams, so it is reflected up to four times. Therefore, the reflectance when the main ray is reflected once to four times should be 1 / 4, 1 / 3, 1 / 2, and 1, and fine adjustments should be made considering the angle of incidence and divergence of the incident light.

[0069] Figure 23 shows the luminance distribution of the display element. In Figure 23, the horizontal axis represents the field of view and the vertical axis represents luminance. Figure 23 plots the luminance in the direction of the X'' axis cross-section from the center of the field of view. In the lighting system configuration of this embodiment, the luminance distribution is such that peaks and valleys alternate, and there is no region with constant luminance. On the other hand, although not shown in the figure, the direction perpendicular to the X'' axis is almost uniform. Therefore, in order to make the luminance distribution shown in Figure 23 uniform, the phase of the X'' axis cross-section of the display element 30 should be controlled so that the optical efficiency (light utilization efficiency) has an inverse relationship with the jagged luminance change.

[0070] In each embodiment, preferably, the difference between the maximum and minimum values ​​of the optical efficiency correction amount in the direction along the intersection line (the difference between the optical efficiency of the uncorrected region and the optical efficiency of the corrected region) is 5% or more. Preferably, the difference between the maximum and minimum values ​​of the corrected optical efficiency in the direction along the intersection line (correction residue) is 5% or less. These can be measured, for example, using a luminance meter.

[0071] (Other embodiments) The present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions.

[0072] According to each embodiment, it is possible to provide a lighting device, display device, control device, control method, and program that exhibit less variation in luminance distribution.

[0073] Each embodiment disclosed includes the following configuration: (Composition 1) A light guide unit that guides light from the light source unit to the display element, It has a control unit that controls the display element, The light guide unit includes a plurality of branching surfaces that branch the light from the light source unit, The lighting device is characterized in that the control unit changes the light utilization efficiency for each position of the display element in order to reduce the variation in the brightness distribution due to the plurality of branching surfaces. (Configuration 2) The plurality of branching surfaces have surfaces having optical properties symmetrical with respect to the optical path from the light guide to the display element. The lighting device according to configuration 1, characterized in that the control unit changes the light utilization efficiency of the display element in a direction equivalent to the intersection line between the surface and the display element. (Composition 3) The lighting device according to configuration 2, characterized in that the control unit changes the light utilization efficiency in a plurality of regions along the intersection line. (Composition 4) The lighting device according to configuration 3, characterized in that the number of the multiple regions is less than the number of the multiple branching surfaces. (Composition 5) The lighting device according to any one of configurations 2 to 4, characterized in that the control unit makes the light utilization efficiency in the direction perpendicular to the intersection line different from the light utilization efficiency in the direction along the intersection line. (Composition 6) The lighting device according to configuration 5, characterized in that the control unit causes the light utilization efficiency to differ in the direction perpendicular to the intersection line. (Composition 7) The lighting device according to configuration 5, characterized in that the control unit makes the light utilization efficiency constant in the direction perpendicular to the intersection line. (Composition 8) The lighting device according to any one of configurations 2 to 7, characterized in that the difference between the maximum and minimum values ​​of the correction amount for light utilization efficiency in the direction along the intersection line is 5% or more. (Composition 9) The lighting device according to any one of configurations 2 to 8, characterized in that the difference between the maximum and minimum values ​​of the corrected light utilization efficiency in the direction along the intersection line is 5% or less. (Composition 10) The system further includes a storage unit for storing data relating to the light utilization efficiency for reducing the aforementioned variation in the luminance distribution, The lighting device according to any one of configurations 1 to 9, characterized in that the control unit changes the light utilization efficiency using the data. (Composition 11) The aforementioned data is data relating to the brightness distribution obtained by inverting the brightness distribution obtained by imaging the user's eye. The lighting device according to configuration 10, characterized in that the control unit changes the light utilization efficiency so that the luminance distribution of the user's eye becomes constant by inverting the luminance distribution of the user's eye using the data. (Composition 12) The aforementioned display element is a transmissive display element, The lighting device according to any one of configurations 1 to 11, characterized in that the light utilization efficiency is the light transmittance in the display element. (Composition 13) The aforementioned display element is a reflective display element, The lighting device according to any one of configurations 1 to 11, characterized in that the light utilization efficiency is the reflectance of light in the display element. (Composition 14) The display element includes a plurality of reflective surfaces, The lighting device according to any one of configurations 1 to 11, characterized in that the control unit changes the light utilization efficiency by driving the plurality of reflective surfaces. (Composition 15) The lighting device according to configuration 14, characterized in that the light utilization efficiency is the time ratio between the on state and the off state of the display element. (Composition 16) A display device characterized by having an illumination device according to any one of configurations 1 to 15 and the display element. (Composition 17) A control device for controlling an illumination device that guides light from a light source to a display element, A storage unit that stores data relating to the light utilization efficiency of the display element in order to reduce variations in the brightness distribution in the user's eye, A control device characterized by having a control unit that uses the aforementioned data to change the light utilization efficiency for each display position of the display element in order to reduce the aforementioned variation in the brightness distribution. (Method 1) A control method for controlling an illumination device that guides light from a light source to a display element, The steps include: acquiring data from the memory unit regarding the light utilization efficiency of the display element to reduce variations in the brightness distribution in the user's eyes; A control method characterized by having the step of changing the light utilization efficiency for each display position of the display element using the aforementioned data to reduce the variation in the luminance distribution. (Composition 17) A program characterized by causing a computer to execute the control method described in Method 1.

[0074] Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of its gist. [Explanation of symbols]

[0075] 1 Display device (lighting device) 10 Light source section 20. Illumination light guide section (light guide section) 21a~21e Branching surface 30 Display elements 71 Control Unit

Claims

1. A light guide unit that guides light from the light source unit to the display element, It has a control unit that controls the display element, The light guide unit includes a plurality of branching surfaces that branch the light from the light source unit, The lighting device is characterized in that the control unit changes the light utilization efficiency for each position of the display element in order to reduce the variation in the brightness distribution due to the plurality of branching surfaces.

2. The plurality of branching surfaces have surfaces having optical properties symmetrical with respect to the optical path from the light guide to the display element. The lighting device according to claim 1, characterized in that the control unit changes the light utilization efficiency of the display element in a direction equivalent to the intersection line between the surface and the display element.

3. The lighting device according to claim 2, characterized in that the control unit changes the light utilization efficiency in a plurality of regions along the intersection line.

4. The lighting device according to claim 3, characterized in that the number of the plurality of regions is less than the number of the plurality of branching surfaces.

5. The lighting device according to claim 2, characterized in that the control unit makes the light utilization efficiency in the direction perpendicular to the intersection line different from the light utilization efficiency in the direction along the intersection line.

6. The lighting device according to claim 5, characterized in that the control unit causes the light utilization efficiency to differ in the direction perpendicular to the intersection line.

7. The lighting device according to claim 5, characterized in that the control unit makes the light utilization efficiency constant in the direction perpendicular to the intersection line.

8. The lighting device according to claim 2, characterized in that the difference between the maximum and minimum values ​​of the correction amount for light utilization efficiency in the direction along the intersection line is 5% or more.

9. The lighting device according to claim 2, characterized in that the difference between the maximum and minimum values ​​of the corrected light utilization efficiency in the direction along the intersection line is 5% or less.

10. The system further includes a storage unit for storing data relating to the light utilization efficiency for reducing the aforementioned variation in the luminance distribution, The lighting device according to claim 1, characterized in that the control unit changes the light utilization efficiency using the data.

11. The aforementioned data is data relating to the brightness distribution obtained by inverting the brightness distribution obtained by imaging the user's eye. The lighting device according to claim 10, characterized in that the control unit changes the light utilization efficiency so that the luminance distribution of the user's eye becomes constant by inverting the luminance distribution of the user's eye using the data.

12. The aforementioned display element is a transmissive display element, The lighting device according to claim 1, characterized in that the light utilization efficiency is the light transmittance in the display element.

13. The aforementioned display element is a reflective display element, The lighting device according to claim 1, characterized in that the light utilization efficiency is the reflectance of light in the display element.

14. The display element includes a plurality of reflective surfaces, The lighting device according to claim 1, characterized in that the control unit changes the light utilization efficiency by driving the plurality of reflective surfaces.

15. The lighting device according to claim 14, characterized in that the light utilization efficiency is the time ratio between the on state and the off state of the display element.

16. A display device comprising an illumination device according to any one of claims 1 to 15 and the display element.

17. A control device for controlling an illumination device that guides light from a light source to a display element, A storage unit that stores data relating to the light utilization efficiency of the display element in order to reduce variations in the brightness distribution in the user's eye, A control device characterized by having a control unit that uses the aforementioned data to change the light utilization efficiency for each display position of the display element in order to reduce the aforementioned variation in the brightness distribution.

18. A control method for controlling an illumination device that guides light from a light source to a display element, The steps include: acquiring data from the memory unit regarding the light utilization efficiency of the display element to reduce variations in the brightness distribution in the user's eyes; A control method characterized by having the step of changing the light utilization efficiency for each display position of the display element using the aforementioned data to reduce the variation in the luminance distribution.

19. A program characterized by causing a computer to execute the control method described in claim 18.

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