Lighting device and display device

Abstract

To provide a lighting device capable of irradiating the whole irradiation surface near the irradiation surface, using a small number of light sources.SOLUTION: A lighting device has a light source, a first optical element that converts light emitted from a light source into substantially parallel light, and a plurality of second optical elements arranged in a first direction. Each of the plurality of second optical elements has a light incident surface. The second optical element guides at least part of the substantially parallel light incident on the light incident surface in a second direction intersecting the first direction, and guides the other portion in the first direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a lighting device and a display device. [Background technology]

[0002] Three-dimensional display technologies include the hologram method and the Arc 3D method. Both can display a three-dimensional image in space by shining a reproduction light onto a specially processed glass plate or film surface. Light is incident on the line drawing engraved on the surface of the glass plate or film, and the light is reflected, refracted, scattered, etc. by the edges of the line drawing and reaches the eye, creating a three-dimensional image floating in the air.

[0003] A known configuration reduces scintillation by splitting light emitted from an extra-high pressure mercury lamp using a half mirror array and combining multiple beams of light having an optical path length difference equal to or greater than the coherence length (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-122949 Summary of the Invention [Problem to be solved by the invention]

[0005] It is desirable for a lighting device to be able to uniformly illuminate the entire illumination surface, such as a display film. When used for three-dimensional display applications, it is desirable for the lighting device itself to be small and placed close to the illumination surface. Illuminating the entire illumination surface with a single light source requires a certain distance from the light source to the illumination surface, resulting in reduced illuminance and increased space. On the other hand, using multiple light sources not only increases costs, but also poses the risk of degrading the quality of the displayed image due to light interference between the light sources. The present invention aims to provide a lighting device that can illuminate the entire illumination surface from the vicinity of the illumination surface using a small number of light sources. [Means for solving the problem]

[0006] In one embodiment, an illumination device includes a light source, a first optical element that converts light emitted from the light source into substantially parallel light, and a plurality of second optical elements that are arranged in a first direction; each of the plurality of second optical elements has a light incident surface; The second optical element guides at least a portion of the substantially parallel light incident on the light incident surface in a second direction intersecting the first direction, and guides the other portion in the first direction. [Effects of the Invention]

[0007] An illumination device is realized that can illuminate the entire irradiation surface from the vicinity thereof with a small number of light sources. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of a display device to which an illumination device according to an embodiment is applied; [Figure 2] 1 is a schematic diagram of a lighting device according to a first embodiment. [Figure 3] FIG. 4 is a schematic diagram of a modified example of the lighting device of the first embodiment. [Figure 4A] 4 is a diagram showing an illumination state of the lighting device of FIG. 3. FIG. [Figure 4B] 4 is a diagram showing an illumination state of the lighting device of FIG. 3. FIG. [Figure 5] 4 is a diagram showing an illumination state of the lighting device of FIG. 3. FIG. [Figure 6A] FIG. 10 is a diagram showing an example of the arrangement of a second optical element. [Figure 6B] FIG. 10 is a diagram showing an example of the arrangement of a second optical element. [Figure 7] FIG. 10 is a schematic diagram of a lighting device according to a second embodiment. [Figure 8] FIG. 10 is a schematic diagram of a modified example of the lighting device of the second embodiment. [Figure 9] 9 is a diagram showing the illumination state of the lighting device of FIG. 8. FIG. [Figure 10A]FIG. 10 is a diagram showing another modified example of the lighting device of the second embodiment. [Figure 10B] FIG. 10 is a diagram showing yet another modified example of the lighting device of the second embodiment. [Figure 11] FIG. 10 is a schematic diagram of a lighting device according to a third embodiment. [Figure 12] FIG. 2 is a diagram showing optical characteristics of Example 1. [Figure 13] FIG. 10 is a diagram showing optical characteristics of Example 2. [Figure 14] FIG. 10 is a diagram showing optical characteristics of Example 3. [Figure 15] FIG. 10 is a diagram showing the optical characteristics of Example 4. [Figure 16] FIG. 10 is a diagram showing the optical characteristics of Example 5. [Figure 17] FIG. 10 is a diagram showing the optical characteristics of Example 6. [Figure 18] FIG. 10 is a diagram showing the optical characteristics of Example 7. [Figure 19] FIG. 10 is a diagram showing the optical characteristics of Example 8. [Figure 20] FIG. 1 is a diagram summarizing the specifications and performance of Examples 1 to 8. DETAILED DESCRIPTION OF THE INVENTION

[0009] In one embodiment, a lighting device is provided that is arranged close to an illumination surface such as a display board or display film and can illuminate the entire illumination surface almost uniformly with a small number of light sources. To achieve this, the device includes a light source, a first optical element that converts light emitted from the light source into approximately parallel light, and a plurality of second optical elements arranged in a first direction. Each of the plurality of second optical elements has a light incident surface, and the second optical element guides at least a portion of the approximately parallel light incident on the light incident surface in a second direction that intersects with the first direction, and guides the remaining portion in the first direction.

[0010] FIG. 1 is a schematic diagram of a display device 1 to which an illumination device 20 according to an embodiment is applied. The display device 1 includes, for example, a display board 11, a stereoscopic display sheet 12, and an illumination device 20 arranged along one side of the display board 11 or the stereoscopic display sheet 12. The display board 11 is, for example, an existing display board that displays one-dimensional or two-dimensional images. The stereoscopic display sheet 12 is a sheet for stereoscopic display, such as a hologram sheet or an arc 3D sheet. The irradiation surface of the stereoscopic display sheet 12 is defined as the XY plane, and the height direction of the display board 11 is defined as the Z direction. By illuminating the stereoscopic display sheet 12 with light emitted from the illumination device 20, a stereoscopic image 15 of a drawing engraved on the stereoscopic display sheet 12 is displayed in the space between the observer's eyes 10 and the stereoscopic display sheet 12.

[0011] To clearly display a stereoscopic image 15 within the field of view of the eye 10, it is desirable to illuminate the entire irradiation surface of the stereoscopic display sheet 12 with approximately parallel light with little interference between adjacent reflected light beams. From the viewpoint of miniaturizing the display device 1, it is desirable to arrange the lighting device 20 near the display board 11 or the stereoscopic display sheet 12. In this embodiment, light emitted from a light source is converted into approximately parallel light by a first optical element, and at least a portion of the approximately parallel light incident on the second optical elements is guided in a direction intersecting the X direction (for example, the Y direction or the -Y direction) using a plurality of second optical elements arranged in the X direction. This allows the entire irradiation surface to be illuminated from the vicinity of the stereoscopic display sheet 12, which is the irradiation surface.

[0012] First Embodiment 2 is a schematic diagram of an illumination device 20A according to the first embodiment. The illumination device 20A includes a light source 25, a first optical element 27, and a plurality of second optical elements 29-1 to 29-n (n is an integer of 2 or greater). The arrangement direction of the second optical elements 29-1 to 29-n (hereinafter sometimes collectively referred to as "second optical elements 29") is defined as the X direction, the height direction of the illumination device 20A or the second optical elements 29 is defined as the Z direction, and the direction perpendicular to the X and Z directions is defined as the Y direction.

[0013] The light source 25, the first optical element 27, and the plurality of second optical elements 29-1 to 29-n are held in a housing 23A. For convenience of illustration, an upper cover of the housing 23A is omitted in FIG. 2, but as will be described later, the housing 23A may be provided with an upper cover. The light source 25 is a microscopic optical device such as a light emitting diode (LED), a laser diode (LD), or a super luminescent diode (SLD) mounted on a mounting substrate 26. A constant current circuit and wiring for driving the light source 25 may be formed on the mounting substrate 26.

[0014] When the light source 25 is a low-coherence optical device such as an LED or SLD, the first optical element 27 is a collimating lens that converts the light emitted from the light source 25 into approximately parallel light. The collimating lens may be any lens that can convert the divergent light emitted from the light source 25 into approximately parallel light, and may be a spherical lens, a cylindrical lens, or the like made of glass, acrylic, polycarbonate, or the like.

[0015] When the light source 25 is an LD, the first optical element 27 may be a beam expander that expands the beam diameter to a size suitable for the light incident surface of the second optical element 29, or that converts an elliptical beam into a circular beam.

[0016] In the first embodiment, assembly 28A including light source 25 and first optical element 27 is disposed inside side surface 22 of housing 23A along the X direction, similar to second optical elements 29-1 to 29-n. In the following description, the +X direction and -X direction will be collectively referred to as the "X direction." Second optical elements 29-1 to 29-n are fixed to bottom surface 21 of housing 23A at predetermined intervals. Second optical elements 29-1 to 29-n are disposed tilted at an angle of 40° to 50°, more preferably 42° to 48°, and even more preferably 44° to 46° with respect to the X axis.

[0017] Each of the second optical elements 29-1 to 29-n has a light incident surface 290. Light emitted from the light source 25 and converted into approximately parallel light by the first optical element 27 is incident on the light incident surface 290 of the second optical element 29-1 located closest to the light source 25. A portion of the light incident on the light incident surface 290 is reflected in the Y direction, and the other portion is transmitted in the X direction. The approximately parallel light transmitted through the second optical element 29-1 is incident on the light incident surface 290 of the next second optical element 29-2, and a portion of the light is reflected in the Y direction, and the other portion is transmitted in the X direction. Subsequently, at least a portion of the incident light is projected in the Y direction by the second optical elements 29-3 to 29-n in sequence.

[0018] To reduce optical loss, the light incident surface 290 of the second optical element 29-n farthest from the light source 25 may have a reflectivity that reflects 50% or more, preferably 90% or more, and more preferably 95% or more of the light incident on the light incident surface 290. The second optical elements 29-1 to 29-n are formed of beam splitters, mirrors, glass plates, etc., having a predetermined reflectivity. The second optical elements 29-1 to 29-n may be optical plates made of glass, acrylic, polycarbonate, etc., with a dielectric mirror, a metal reflective film, etc. formed on the light incident surface, or may be optical plates with a diffraction grating designed to have a predetermined reflectivity. The second optical elements 29-1 to 29-n may be cube- or prism-type beam splitters or mirrors instead of the plate-type optical elements shown in the figures. Alternatively, as described below, some or all of the second optical elements 29-1 to 29-n may be plain glass, or may be glass plates with an anti-reflection film formed on the back side of the light incident surface 290.

[0019] 2, the illumination device 20A can irradiate the illumination surface with substantially parallel light without gaps using a single light source 25. Furthermore, the light source 25, the first optical element 27, and the second optical elements 29-1 to 29-n are all compactly arranged in the X direction, and the illumination device 20A can be provided close to the illumination surface along one side of the display board 11 or the three-dimensional display sheet 12.

[0020] 3 is a schematic diagram of a modified example of the illumination device of the first embodiment. The illumination device 20B has a first unit 30B-1 and a second unit 30B-2, each including a light source 25, a first optical element 27, and second optical elements 29-1 to 29-n. In this example, the first unit 30B-1 and the second unit 30B-2 are arranged symmetrically along the X direction with respect to the center of the longitudinal direction (X direction) of the lower surface 21 of the housing 23B. The first unit 30B-1 and the second unit 30B-2 may be collectively referred to as "unit 30B" as appropriate.

[0021] In the first unit 30B-1 and the second unit 30B-2, assemblies 28B-1 and 28B-2, each including a light source 25 and a first optical element 27, are disposed at both ends in the X direction. In each of the first unit 30B-1 and the second unit 30B-2, light is emitted from the light source 25 and converted into approximately parallel light by the first optical element 27, and is projected in the Y direction by the second optical element 29 while being guided from the outside toward the center in the X direction.

[0022] The configuration shown in FIG. 3 is effective when illuminating a large-area stereoscopic display sheet 12. In each unit 30B of the illumination device 20B, the light source 25, the first optical element 27, and the second optical elements 29-1 to 29-n are all compactly arranged in the X direction, allowing the illumination device 20B to be installed close to the illumination surface along one side of the display board 11 or the stereoscopic display sheet 12. Only two light sources 25 are installed at both ends in the X direction, and almost all of the incident light guided from both sides is reflected in the Y direction by the second optical element 29-n located in the center, thereby reducing light loss and interference between adjacent reflected light beams. In addition, because the light is projected in the Y direction by the second optical elements 29-1 to 29-n before the divergence of the approximately parallel light becomes large, interference between adjacent reflected light beams is also reduced.

[0023] The wavelengths of the light sources 25 used in the first unit 30B-1 and the second unit 30B-2 may be the same or different. Depending on the drawings engraved on the stereoscopic display sheet 12, half of the irradiation surface may be irradiated with white light and the other half with green light to display a color stereoscopic image 15 in the air. As described above, in the lighting device 20B, there is little interference between adjacent reflected light beams, so even when light sources 25 with different wavelengths are used, there is almost no color mixing and the irradiation surface can be illuminated with two colors separately.

[0024] 4A and 4B show the illumination state of illumination device 20B in FIG. 3. In FIG. 4A, illumination device 20B is entirely housed inside housing 23B. Housing 23B has bottom surface 21, side surfaces 22, and top surface 24 that entirely covers second optical element 29 (see FIG. 3). In each of first unit 30B-1 and second unit 30B-2, substantially parallel light is transmitted from the end toward the center in the X direction, while at least a portion of the light is sequentially projected in the Y direction. A cover may be placed on the opening surface of housing 23B, i.e., the surface from which light is extracted.

[0025] For example, as shown in FIG. 4B, a cover 241 may be provided on the light-emitting side of the illumination device 20B. To clearly show the arrangement of the cover 241, the top surface 24 is not shown in FIG. 4B. The cover 241 may be optically processed to guide the light 35 projected in the Y direction by the second optical elements 29-1 to 29-n (see FIG. 3) obliquely downward toward the target irradiation surface so that the light 35 projected in the Y direction from the illumination device 20B is directed downward below the XY plane defined by the X and Y directions. This is because, unless the light 35 projected in the Y direction by the second optical elements 29-1 to 29-n is projected in a direction parallel to the surface of the stereoscopic display sheet 12 and illuminates the surface, the image formed on the stereoscopic display sheet 12 cannot be illuminated, and stereoscopic display cannot be achieved. The cover 241 provided on the light-emitting side may be used in the illumination device 20A of FIG. 2.

[0026] 5 is a diagram showing the illumination state of the illumination device in FIG. 3, specifically, a schematic diagram of light projected in the Y direction by illumination device 20A or 20B (hereinafter, occasionally referred to collectively as "illumination device 20"). The light projected in the Y direction from illumination device 20 is projected at an inclination of 1 to several degrees, for example, 1.5 to 2.5 degrees, with respect to the XY plane, depending on the size of the illumination surface. This allows the approximately parallel light projected from illumination device 20 to evenly illuminate the entire surface of stereoscopic display sheet 12, starting from the vicinity of the surface of stereoscopic display sheet 12.

[0027] The second optical elements 29-1 to 29-n are arranged to minimize overlap of the substantially parallel light beams projected in the Y direction and to suppress the occurrence of dark lines on the illuminated surface. To achieve this, each of the second optical elements 29-1 to 29-n is arranged so as to be offset in the direction opposite to the light projection side (in the -Y direction if the light projection direction is the Y direction as described above) as it moves away from the light source 25. Alternatively, the width of the second optical elements 29-1 to 29-n in the Y direction increases as it moves away from the light source 25.

[0028] 6A and 6B show examples of the arrangement of second optical elements 29-1 to 29-3. In Fig. 6A and 6B, the arrangement direction of second optical elements 29-1 to 29-3 is defined as the X direction, the height direction of second optical element 29 is defined as the Z direction, and the projection direction by second optical element 29 is defined as the Y direction.

[0029] As shown in FIG. 6A, a configuration is considered in which second optical elements 29-1 to 29-3 of a constant width are arranged without offset along a reference line Rx extending in the X direction. Here, incident light is reflected by the light incident surface 290 of the second optical elements 29-1 to 29-3, but as will be described later, it may be configured so that the light is reflected by the back surface opposite to the light incident surface 290. The beam diameter of the light converted into approximately parallel light by the first optical element 27 is D1. The beam diameter usable by the second optical elements 29-1 to 29-3 is D2, which is smaller than D1. The beam diameter of the light reflected in the Y direction by the second optical element 29-1, which is closest to the light source 25, is φ1. When a portion of the light transmitted through the second optical element 29-1 is incident on the side surface 31 of the second optical element 29-2 in the next stage, it is not reflected in the Y direction but is vignetted, i.e., a loss L LOST When a part of the light transmitted through the second optical element 29-2 is incident on the side surface 31 of the next second optical element 29-3, a further loss L LOST becomes larger.

[0030] As a result, the beam diameters of the light projected in the Y direction become thinner (φ2, φ3) as the distance between the second optical elements 29-2, 29-3 and the light source 25 increases, and dark lines 33a may appear between adjacent reflected light beams. The dark lines 33a may be recognized as dark spots on a stereoscopically displayed image. When an LD is used as the light source 25, a relatively narrow beam is incident on the center of the second optical element 29, so the impact of the dark lines 33a is small. In contrast, when an LED or SLD is used as the light source 25, even if the light emitted from the light source 25 is collimated to a substantially parallel beam, it may be difficult to narrow the beam so that it is incident only on the center of the second optical element 29.

[0031] In this embodiment, the second optical elements 29-1 to 29-n are designed to suppress the occurrence of dark lines 33a and to illuminate the irradiation surface evenly. In Fig. 6B, the second optical elements 29-1 to 29-3 are arranged so that the further away from the light source 25 they are, the more offset they are from the reference line Rx in the -Y direction (opposite to the projection direction).

[0032] For example, the second optical element 29-1 closest to the light source 25 is aligned with the reference line Rx. The next second optical element 29-2 is offset from the reference line Rx in the -Y direction by Δd1. The offset amount Δd2 of the third second optical element 29-3 in the -Y direction is set larger than Δd1. This allows the substantially parallel light converted by the collimating lens to pass through the second optical elements 29-1 to 29-3 while maintaining the diameter D1. Light rays vignetted by the side surface 31 of the next-stage second optical element 29 are minimized, and the beam diameter φ1 of the substantially parallel light projected in the Y direction by the second optical elements 29-1 to 29-3 can be made substantially constant. Even if a small amount of light rays are vignetted by the side surface 31 of the next-stage second optical element 29, the dark line 33b caused by the vignetting is approximately the thickness of the second optical element 29 and is therefore hardly recognized as a dark spot by the observer's eye 10.

[0033] Instead of offsetting the positions of the second optical elements 29-1 to 29-n in the -Y direction as they become farther from the light source 25, the width of the second optical elements 29 may be set to increase as they become farther from the light source 25. By gradually increasing the width of the second optical elements 29, as in FIG. 6B , it is possible to minimize the amount of light vignetting at the side surface 31 of the second optical element 29 at the next stage, and to maintain a substantially constant beam diameter φ1 of the substantially parallel light projected in the Y direction. Even if a small amount of light vignetting occurs at the side surface 31 of the second optical element 29 at the next stage, the dark line caused by the vignetting is approximately the thickness of the second optical element 29, and is hardly recognized as a dark spot by the observer's eye 10.

[0034] Second Embodiment 7 is a schematic diagram of an illumination device 20C according to a second embodiment. Similar to the first embodiment, the illumination device 20C has a plurality of second optical elements 29-1 to 29-n (n is an integer of 2 or more) arranged in the X direction. The second optical elements 29-1 to 29-n are collectively referred to as "second optical elements 29" where appropriate.

[0035] In the second embodiment, an assembly 28C including a light source 25 and a first optical element 27 is provided in a direction (for example, a -Y direction) intersecting with the arrangement direction (X direction) of second optical elements 29-1 to 29-n. If the arrangement in the first embodiment is an I-shaped arrangement, the arrangement in the second embodiment may be called an L-shaped arrangement.

[0036] The light source 25 mounted on the mounting substrate 26 is an LED, an LD, an SLD, etc., as in the first embodiment. Depending on the type of light source 25 used, a collimator lens, a beam expander, etc. can be used as the first optical element 27.

[0037] The light source 25, the first optical element 27, and the plurality of second optical elements 29 are held in a housing 23C. The housing 23C may have an L-shaped lower surface 21C in accordance with the L-shaped arrangement of the lighting device 20C. The second optical elements 29-1 to 29-n are fixed to the lower surface 21C at predetermined intervals on the inner side of the side surface 22 of the housing 23C. The second optical elements 29-1 to 29-n are arranged tilted at an angle of 40° to 50°, more preferably 42° to 48°, and even more preferably 44° to 46° with respect to the X-axis.

[0038] Light emitted from the light source 25 and converted into substantially parallel light by the first optical element 27 enters the light incident surface 290 of the second optical element 29-1 located closest to the light source 25, where a portion of the parallel light is transmitted in the Y direction and another portion is reflected in the X direction. The substantially parallel light reflected by the second optical element 29-1 enters the light incident surface 290 of the next second optical element 29-2, where a portion of the parallel light is reflected in the Y direction and another portion is transmitted in the X direction. Subsequently, at least a portion of the incident light is projected in the Y direction by the second optical elements 29-3 to 29-n in sequence. The light incident surface 290 of the second optical element 29-1 located closest to the light source 25 may have a reflectance of 50% or more, preferably 80% or more, and more preferably 90% or more. In this case, most of the incident light can be reflected in the X direction to distribute the light uniformly.

[0039] The light incident surface 290 of the second optical element 29-n farthest from the light source 25 may have a reflectance of 50% or more, preferably 90% or more, and more preferably 95% or more. In this case, most of the incident light can be reflected in the Y direction to reduce optical loss. The second optical elements 29-1 to 29-n are formed of beam splitters, mirrors, glass plates, etc., having a predetermined reflectance. The second optical elements 29-1 to 29-n may be optical plates made of glass, acrylic, polycarbonate, etc., with a dielectric mirror, a metal reflective film, etc. formed on the light incident surface, or may be optical plates with a diffraction grating designed to have a predetermined reflectance. The second optical elements 29-1 to 29-n may be cube- or prism-type beam splitters or mirrors instead of the plate-type optical elements shown in the figure. Alternatively, as described below, some or all of the second optical elements 29-1 to 29-n may be plain glass, or may be glass plates with an anti-reflection film formed on the back side of the light incident surface 290.

[0040] As in the first embodiment, the illumination device 20C can illuminate the entire XY plane with substantially parallel light from near the XY plane using a single light source 25. Specifically, the XY plane can be illuminated evenly, without gaps, with substantially parallel light. By arranging an assembly 28C including the light source 25 and the first optical element 27 in an L-shape with respect to the arrangement of the second optical elements 29-1 to 29-n, three or more illumination devices 20C can be lined up in the X direction for use. Furthermore, the housings 23C can be provided close to each other along one side of the display panel 11 or the three-dimensional display sheet 12.

[0041] 8 is a schematic diagram of a modified example of the illumination device of the second embodiment. The illumination device 20D has a first unit 30D-1 and a second unit 30D-2, each including a light source 25, a first optical element 27, and second optical elements 29-1 to 29-n. The units may be collectively referred to as "unit 30D" as appropriate. In this example, an assembly 28D-1 of the first unit 30D-1 and an assembly 28D-2 of the second unit 30D-2 are disposed in the center in the X direction, and substantially parallel light converted by the first optical element 27 is projected in the Y direction while being guided from the center in the X direction toward both sides.

[0042] The configuration in Fig. 8 is effective when illuminating a large-area stereoscopic display sheet 12. Only two light sources 25 are provided in the center in the X direction, and light guided from the center to both sides is projected sequentially in the Y direction, so light interference between the light sources 25 is suppressed. With a relatively short optical path length, almost all light can be projected in the Y direction before the influence of divergence of approximately parallel light becomes significant, so interference between adjacent reflected light beams is also suppressed.

[0043] The wavelengths of the light sources 25 used in the first unit 30D-1 and the second unit 30D-2 may be the same or different. Depending on the drawings engraved on the stereoscopic display sheet 12, half of the irradiation surface may be illuminated with white light and the other half with green light to display a color stereoscopic image 15 in the air. In the configuration of Figure 8, interference between adjacent reflected light beams is suppressed, so it is possible to combine light sources 25 with different wavelengths.

[0044] Fig. 9 shows the illumination state of illumination device 20D of Fig. 8. In Fig. 8, illumination device 20D may have housing 23D that houses first unit 30D-1 and second unit 30D-2. Housing 23D has top surface 24D in addition to bottom surface 21D and side surface 22. In each of first unit 30D-1 and second unit 30D-2, substantially parallel light is guided from the center toward both ends in the X direction, and at least a portion of the light is sequentially projected in the Y direction.

[0045] As in the first embodiment, a cover 241 may be provided on the light output side of the illumination device 20D. The cover 241 may be optically processed to guide the light 35 projected in the Y direction by each of the second optical elements 29-1 to 29-n diagonally downward so that the entire XY plane is illuminated with the light 35 projected in the Y direction. Furthermore, the second optical elements 29-1 to 29-n arranged in the X direction may be arranged so as to be offset gradually in the -Y direction as they become farther away from the light source 25 (see FIG. 6B). Alternatively, the width of the second optical elements 29-1 to 29-n may be gradually increased as they become farther away from the light source 25.

[0046] 10A and 10B show yet another modification of the illumination device of the second embodiment. In Fig. 10A, illumination device 20E has an L-shaped first unit 30E-1, a second unit 30E-2, and a third unit 30E-3 arranged repeatedly in the X direction in the same orientation. Assemblies 28E-1, 28E-2, and 28E-3, each including a light source 25 and a first optical element 27, are housed in the protruding portions of the L shapes.

[0047] 10A is suitable for illuminating a large-area stereoscopic display sheet 12. The number of units is not limited to three, and by repeatedly arranging four or more units, it is possible to appropriately illuminate a display medium that is long in one direction (X direction).

[0048] 10B, the lighting device 20F has an L-shaped first unit 30F-1 and a second unit 30F-2 arranged in opposite directions along the X direction. Assemblies 28F-1 and 28F-2, each including a light source 25 and a first optical element 27, are arranged at both ends in the X direction. Light emitted from the light source 25 and converted into approximately parallel light by the first optical element 27 is guided from both ends in the X direction toward the center, and then sequentially projected in the Y direction. By setting the reflectance of the second optical element 29, which is located in the center in the X direction, to be high, light loss and interference can be suppressed.

[0049] 10B is also suitable for illuminating a large-area stereoscopic display sheet 12. The number of units is not limited to two, and by repeatedly arranging three, four, or more units, it is possible to appropriately illuminate a display medium that is long in one direction (X direction).

[0050] 10A or 10B, a cover 241 (see FIG. 9) may be provided on the light output side of the illumination devices 20E, 20F. The cover 241 may be optically processed to guide the light projected in the Y direction diagonally downward so that the XY plane is illuminated with approximately parallel light projected in the Y direction. Alternatively, the second optical elements 29-1 to 29-n arranged in the X direction may be offset slightly in the -Y direction as they become farther away from the light source 25, or the width of the second optical elements 29-1 to 29-n may be gradually increased as they become farther away from the light source 25. This makes it possible to suppress the occurrence of dark lines and illuminate the illumination surface evenly.

[0051] <Third embodiment> 11 is a schematic diagram of an illumination device 20G according to a third embodiment. The illumination device 20G uses a single light source 25 and a single first optical element 27G, and two sets of arrays of second optical elements 29-1 to 29-n are arranged in parallel. One array of second optical elements 29-1 to 29-n is referred to as a first array 295R, and the other array of second optical elements 29-1 to 29-n is referred to as a second array 295L. The first array 295R and the second array 295L may be collectively referred to as "arrays 295" as appropriate. In each of the first array 295R and the second array 295L, the multiple second optical elements 29-1 to 29-n are arranged in the X direction, but the direction in which the light incident surfaces 290 of the second optical elements 29-1 to 29-n included in the first array 295R are inclined relative to the X axis is opposite to the direction in which the light incident surfaces 290 of the second optical elements 29-1 to 29-n included in the second array 295L are inclined relative to the X axis.

[0052] In each of the first array 295R and the second array 295L including the second optical elements 29-1 to 29-n, the second optical elements 29-1 to 29-n may be offset in opposite directions (i.e., in the -Y and +Y directions) along the light projection direction as they move farther away from the assembly 28G. Alternatively, the width of the second optical elements 29-1 to 29-n may increase as they move farther away from the assembly 28G. A cover may be provided on the light output side of each of the first array 295R and the second array 295L arranged in parallel. The cover may be optically processed to guide light reflected by the first array 295R on the right side of the light source 25 diagonally downward to the right, and light reflected by the second array 295L on the left side of the light source 25 diagonally downward to the left.

[0053] The illumination device 20G can project light 35R and 35L in opposite directions, i.e., the +Y direction and the -Y direction, using only one assembly 28G including a light source 25 and a first optical element 27G. The illumination device 20G is suitably applied to a configuration in which multiple 3D display sheets are arranged in one direction (the Y direction), such as a ticket machine or an advertisement board. One illumination device 20G can be used to display 3D images on two adjacent display surfaces.

[0054] <Optical characteristics of the second optical element> The following describes the optical characteristics of the second optical elements 29-1 to 29-n when the design parameters of the illumination device 20 are variously changed. In the following Examples 1 to 8, an LED is used as the light source 25, and a collimating lens is used as the first optical element 27. The number of units 30 each consisting of the light source 25, the first optical element 27, and the second optical elements 29-1 to 29-n, as well as the type and reflectance of the second optical element 29, are variously changed to calculate the optical characteristics. [Example]

[0055] Fig. 12 shows the reflection characteristics of second optical elements 29-1 to 29-n in Example 1. Example 1 employs the configuration of the I-shaped illumination device 20B in Fig. 3. Two sets of units 30B, each including a light source 25, a first optical element 27, and second optical elements 29-1 to 29-n, are used, and assemblies 28B, each including a light source 25 and a first optical element 27, are arranged at both ends in the X direction. Each unit 30B has six second optical elements 29-1 to 29-6, and a total of 12 second optical elements 29 are arranged symmetrically with respect to the center in the X direction.

[0056] 12, the horizontal axis represents the serial number of the second optical elements 29, and the vertical axis represents the normalized amount of emitted light from the second optical elements 29. The serial number of the second optical elements is called the "mirror number." Of the amounts of light emitted from the multiple second optical elements 29, the highest amount of emitted light is normalized to 100%.

[0057] The twelve second optical elements 29 are plate-type beam splitters (BS). Mirror numbers 1 to 6 correspond to the second optical elements 29-1 to 29-6 of the first unit 30B-1, and mirror numbers 7 to 12 correspond to the second optical elements 29-6 to 29-1 of the second unit 30B-2. The relationship between the mirror number and the reflectance is as follows: Mirror Number Reflectivity 1 25.0% 2 25.0% 3 30.0% 4 40.0% 5 50.0% 6 100.0% 7 100.0% 8 50.0% 9 40.0% 10 30.0% 11 25.0% 12 25.0%

[0058] The sixth and seventh beam splitters, which are the furthest from the light source 25 in the first unit 30B-1 and the second unit 30B-2, respectively, have a reflectivity of 100%, and all of the light incident on their light incident surfaces is reflected, maximizing the light utilization efficiency.

[0059] In Example 1, the emitted light intensity gradually decreases from the outer beam splitters toward the central beam splitter, and the normalized emitted light intensity of the central beam splitter is approximately 50%. The difference in light intensity within the irradiation surface is approximately 50%. If the emitted light intensity changes continuously, the human eye will not perceive the change even if the normalized emitted light intensity decreases to 30%. Therefore, the difference in light intensity within the irradiation surface in Example 1 is good. Since almost all light is reflected in the Y direction by six mirrors on both sides in the X direction, the divergence of the reflected light is small, and the interference between the reflected light beams is negligibly small. [Example]

[0060] Fig. 13 shows the reflection characteristics of second optical elements 29-1 to 29-n in Example 2. Like Example 1, Example 2 employs the configuration of I-type illumination device 20B in Fig. 3, and uses a total of 12 beam splitters (mirror numbers 1 to 12) as second optical elements 29. However, the reflectance of the beam splitters is limited to two types: 15.0% and 25.0%. The relationship between the mirror number and the reflectance is as follows: Mirror Number Reflectivity 1 15.0% 2 15.0% 3 15.0% 4 25.0% 5 25.0% 6 25.0% 7 25.0% 8 25.0% 9 25.0% 10 15.0% 11 15.0% 12 15.0%

[0061] In Example 2, the output light intensity gradually decreases at the three outer beam splitters, but because the reflectivity of the central beam splitter is increased, the normalized output light intensity increases at the fourth and ninth beam splitters, and then decreases toward the center. The normalized output light intensity at the central beam splitter is maintained at 50% or more, and the difference in light intensity within the irradiation surface is good. Although some of the incident light is not reflected by the central mirror, causing some light loss, since this is the last mirror in the transmission direction, the incident light intensity itself is small, and the light loss is negligible. Since most of the light is reflected by six mirrors on both sides in the X direction, the divergence of the reflected light is small, and the interference between the reflected light beams is also negligible. [Example]

[0062] Fig. 14 shows the reflection characteristics of second optical elements 29-1 to 29-n in Example 3. Like Examples 1 and 2, Example 3 employs the configuration of I-type illumination device 20B in Fig. 3 and uses a total of 12 beam splitters (mirror numbers 1 to 12) as second optical elements 29. However, the beam splitters have only one reflectance of 15.0%. In other words, the reflectance is 15.0% for all of mirror numbers 1 to 12.

[0063] In Example 3, the emitted light intensity gradually decreases from the outer to the inner beam splitter, and at the most central beam splitter, the normalized emitted light intensity is slightly below 50%, but significantly above 30%. The difference in light intensity within the irradiation surface is good, at just under 50%. Although 85% of the incident light is not reflected by the central mirror, resulting in some light loss, the light utilization efficiency is within an acceptable range. Since most of the light is reflected in the Y direction by six mirrors on both sides in the X direction, the divergence of the reflected light is small, and the interference between the reflected light beams is negligible. [Example]

[0064] Fig. 15 shows the reflection characteristics of second optical elements 29-1 to 29-n of Example 4. Example 4 employs the configuration of illumination device 20A of Fig. 2, and uses a single LED light source 25 and a single collimating lens as first optical element 27. Twelve consecutive beam splitters (mirror numbers 1 to 12) are used as second optical element 29. The beam splitters have two reflectivities: 8.0% and 15.0%. The relationship between mirror number and reflectivity is as follows: Mirror Number Reflectivity 1 8.0% 2 8.0% 3 8.0% 4 8.0% 5 8.0% 6 8.0% 7 15.0% 8 15.0% 9 15.0% 10 15.0% 11 15.0% 12 15.0%

[0065] In Example 4, light emitted from a single light source 25 is projected in the Y direction using 12 beam splitters. Therefore, the reflectivity of the seventh and subsequent beam splitters is set higher than the reflectivity of the first to sixth beam splitters. The emitted light intensity gradually decreases from the first to sixth beam splitters. The normalized emitted light intensity reaches a maximum at the seventh beam splitter, and then decreases steadily from the eighth beam splitter onward. The normalized emitted light intensity is maintained above 50% at the first to eleventh beam splitters, and is only slightly below 50% at the last beam splitter. The difference in light intensity within the irradiation surface is approximately 50%, which is satisfactory. Although some light is not reflected at the last beam splitter, resulting in a slight light loss, the incident light intensity itself is small, making the light loss negligible. The light utilization efficiency is within an acceptable range. Although nearly parallel light is generated by the first optical element 27, the long optical path length causes the effect of divergence, which can lead to divergence and interference of the light beams at the 11th and 12th beam splitters. If the optical path length becomes even longer, the interference between the light beams reflected by the last two beam splitters will increase, and one displayed image may appear as multiple images in the stereoscopic display image. However, with the configuration of Example 4, this is within the allowable range for stereoscopic display. [Example]

[0066] FIG. 16 shows the reflection characteristics of the second optical elements 29-1 to 29-n of Example 5. Example 5 employs the configuration of the illumination device 20A of FIG. 2, using a single LED light source 25 and a single collimating lens as the first optical element 27. Twelve consecutive pieces of raw glass (mirror numbers 1 to 12) are used as the second optical element 29. Although the raw glass is not coated with a reflective material, all of the raw glass has a reflectance of 17.5% due to Fresnel reflection, which occurs when light is incident on the interface between media with different refractive indices. The thickness of this raw glass is 1.0 mm. The distance between the emission point of light reflected on the front surface of the raw glass and the emission point of light reflected on the back surface is 0.74 mm.

[0067] In Example 5, the normalized output light intensity is 30% or more for the first seven raw glasses, but drops to less than 30% for the eighth and subsequent raw glasses. The difference in light intensity within the irradiation surface is approximately 80% at most, but because the normalized output light intensity changes continuously, the difference in light intensity is difficult to perceive in the stereoscopic display image. The difference in light intensity within the irradiation surface is within an acceptable range. Although a slight light loss occurs due to light not reflected by the twelfth raw glass, it is negligibly small, resulting in very good light utilization efficiency. Interference may occur between light reflected on the front surface and light reflected on the back surface of the raw glass, but this is within an acceptable range. The configuration of Example 5 is very effective in terms of cost. [Example]

[0068] FIG. 17 shows the reflection characteristics of the second optical elements 29-1 to 29-n of Example 6. Example 6 employs the configuration of the illumination device 20A of FIG. 2, using a single LED light source 25 and a single collimating lens as the first optical element 27. Twelve consecutive raw glass pieces (mirror numbers 1 to 12) are used as the second optical element 29. An anti-reflection (AR) coating is applied to the back surface of the raw glass pieces. The reflectance of the AR-coated raw glass pieces is uniformly 9.7%. The AR coating on the back surface of the raw glass pieces suppresses reflection from the back surface, thereby suppressing interference between the light reflected from the front surface of the raw glass pieces and the light reflected from the back surface. The thickness of the AR-coated raw glass pieces is 1.0 mm, and the distance between the emission points of the light reflected from the front and back surfaces of the AR-coated raw glass pieces is 0.74 mm.

[0069] In Example 6, a normalized output light intensity of 30% or more is maintained up to the 12th AR-coated raw glass. Therefore, the continuous change in normalized output light intensity is not noticeable to the human eye, and the difference in light intensity within the irradiation surface is within an acceptable range. Although light loss occurs due to the light not reflected by the 12th raw glass, the light utilization efficiency is within an acceptable range. Due to the long optical path length, interference of the reflected light beams may occur at mirror numbers 11 and 12, but this is also within an acceptable range. The configuration of Example 6 is very advantageous in terms of cost, and the quality of the stereoscopic display image is better than that of Example 5. [Example]

[0070] FIG. 18 shows the reflection characteristics of second optical elements 29-1 to 29-n of Example 7. Example 7 employs the configuration of the illumination device 20A of FIG. 2, using a single LED light source 25 and a single collimating lens as the first optical element 27. Only 12 consecutive pieces of raw glass are used as the second optical element 29. The raw glass pieces of mirror numbers 1 to 6 have an AR coating on the back surface. The reflectance of the AR-coated raw glass is 9.7%. The raw glass pieces of mirror numbers 7 to 12 are uncoated. The reflectance of the uncoated raw glass is 17.5%. Throughout mirror numbers 1 to 12, the thickness of the raw glass is 1.0 mm, and the distance between the emission points of light reflected from the front and back surfaces of the raw glass is 0.74 mm.

[0071] The normalized output light intensity monotonically decreases from mirror number 1 to 6, but increases once at mirror number 7 and then decreases again monotonically from mirror number 8 onwards. In Example 7, the normalized output light intensity is maintained at 50% or more up to mirror number 10, and is maintained at about 40% at mirror numbers 11 and 12, so the difference in light intensity within the irradiation surface is within the allowable range. Light loss is less than in Example 6, and light utilization efficiency is good. As in Examples 5 and 6, the long optical path length may cause interference between reflected light beams at mirror numbers 11 and 12, but this is within the allowable range. The configuration of Example 7 is also very advantageous in terms of cost, and the quality of the stereoscopic display image is better than that of Example 5. [Example]

[0072] FIG. 19 shows the reflection characteristics of the second optical elements 29-1 to 29-n of Example 8. Similar to Examples 1 to 3, Example 8 employs the configuration of the lighting device 20B of FIG. 3 and uses two sets of units 30 each consisting of an LED light source 25, a first optical element 27, and second optical elements 29-1 to 29-n. Uncoated raw glass is used as the second optical element. Each unit 30 contains six pieces of raw glass, for a total of 12 pieces of raw glass. The thickness of the raw glass is 0.5 mm, and the distance between the emission points of light reflected from the front and back surfaces of the raw glass is 0.37 mm.

[0073] A normalized emitted light intensity of 40% or more is maintained through mirror numbers 1 to 12, and the difference in light intensity within the irradiation surface is within the allowable range. The light loss is less than in Example 6, and the light utilization efficiency is well within the allowable range. By reducing the thickness of the raw glass, the distance between the emission points of light reflected on the front and back of the raw glass is narrowed, reducing the interference of the reflected light. Since the optical path length of one unit is half that of Examples 4 to 7, interference between adjacent reflected light beams is reduced. The configuration of Example 8 is very advantageous in terms of cost.

[0074] Figure 20 is a diagram summarizing the specifications and performance of Examples 1 to 8. The number of units (shown as the number of sets in the figure) consisting of an LED, a collimating lens, and multiple second optical elements 29, and the type of second optical element (mirror) were varied to evaluate light utilization efficiency, light intensity difference within the irradiation surface, cost, and luminous flux coherence. The luminous flux interference includes interference due to beam divergence caused by an increase in the optical path length, and interference of the luminous flux reflected on the front and back surfaces of the second optical element. Excellent evaluation results are indicated by double circles. Good evaluation results are indicated by single circles. Evaluation results within the acceptable range are indicated by triangles.

[0075] Throughout Examples 1 to 8, the light utilization efficiency was highly evaluated, being within or exceeding the acceptable range. In particular, Examples 1 and 5 had low light loss and very good light utilization efficiency. The light intensity difference within the irradiation surface was within the acceptable range or was evaluated as good throughout Examples 1 to 8. In particular, Examples 1 to 4 had a good light intensity difference within the irradiation surface, within a range of approximately 50%. In terms of cost, Examples 1, 2, and 4, which use beam splitters with different reflectivities, tend to be expensive, but are within the acceptable range. Example 3, which uses a beam splitter with a single reflectivity, is more cost-effective than Examples 1, 2, and 4. Examples 5 to 8, which use plain glass, are superior in terms of cost. Regarding light beam interference, Examples 1 to 8, which use two sets of units, shorten the optical path length and sufficiently suppress light divergence. Interference of reflected light on the front and back of the element was sufficiently suppressed in Examples 1 to 3, which use beam splitters, and in Example 8, which uses thin plain glass. Depending on the priority, one of the configurations of Examples 1 to 8 can be appropriately selected. Depending on the optical path length, an LD may be used instead of an LED as the light source 25, and a beam expander may be used as the first optical element 27.

[0076] Although the illumination device 20 and its application examples have been described above based on specific configuration examples, the present invention is not limited to these configuration examples. The arrangement and number of elements of the illumination device are not limited to those of Examples 1 to 8. The number of second optical elements 29 included in one unit can be appropriately set depending on the type of light source 25 used. The second optical element 29 farthest from the light source 25 may be a mirror or beam splitter with a reflectance of 90% or more, and the remaining second optical elements 29 may be plain glass or plain glass with an AR coating. The housing 23A of the illumination device 20A in FIG. 2 and the housing 23C of the illumination device 20C in FIG. 7 may have a top surface 24. When illuminating a large-area stereoscopic display sheet 12, three or more units 30 may be repeatedly arranged as shown in FIG. 10A or 10B. In either case, the illumination surface can be illuminated over a wide area with approximately parallel light without gaps, i.e., evenly.

[0077] By combining a sensor with the display device 1 using the lighting device 20 of the embodiment, a three-dimensional image of a touch panel can be displayed in the air, realizing a non-contact input device. The lighting device 20 of the embodiment can be applied to a wide range of applications requiring approximately parallel light, such as street advertising lighting and projectors. Furthermore, since it can be used as a lighting device that uniformly irradiates an irradiation surface, it can also be used to realize, for example, a sterilization device using a UV light source. The irradiation surface can be a surface such as a desk, or UV light can be irradiated to create an invisible sterilization surface in space. Multiple light sources 25 can be arranged in the Z direction, and two irradiation surfaces can be lined up in the Z direction. One can be UV and the other can be visible light, making it possible to visualize a position close to the sterilization surface. [Explanation of symbols]

[0078] 1 Display device 20, 20A~20G lighting equipment 11 Display board 12 3D display sheet 21 Underside of the housing 22 Side of the case 23, 23A~23D housing 25 light source 27 First Optical Element 28A, 28B-1, 28B-2, 28C, 28D-1, 28D-2, 28E-1, 28E-2, 28E-3, 28F-1, 28F-2, 28G Assembly 29, 29-1 to 29-n Second optical element 30, 30B, 30D units 30B-1, 30D-1, 30E-1, 30F-1 1st unit 30B-2, 30D-2, 30E-2, 30F-2 2nd unit 30E-3 Unit 3 33a, 33b dark line 290 Light incidence surface 295R First sequence 295L Second sequence

Claims

1. A light source and a first optical element that converts the light emitted from the light source into substantially parallel light; a plurality of second optical elements arranged in a first direction; and each of the plurality of second optical elements has a light incident surface; the second optical element guides at least a portion of the substantially parallel light incident on the light incident surface in a second direction intersecting with the first direction, and guides another portion of the substantially parallel light in the first direction; each of the plurality of second optical elements is arranged to be offset in a direction opposite to the second direction as it becomes farther from the light source; the side surface of each of the plurality of second optical elements in the opposite direction is inclined from the first direction so that the end on the light source side is positioned in the second direction further than the end on the opposite side to the light source; Lighting equipment.

2. Each of the plurality of second optical elements is arranged to cross the center of the substantially parallel light. The lighting device according to claim 1 .

3. Each of the plurality of second optical elements is formed so that the width of the light incident surface increases with increasing distance from the light source.

3. The lighting device according to claim 1 or 2.

4. the light source and the first optical element are provided along the first direction, each of the plurality of second optical elements reflects at least a portion of the substantially parallel light incident on the light incident surface in the second direction and transmits the other portion in the first direction; The lighting device according to claim 1 .

5. the light source and the first optical element are provided along the second direction, the second optical element provided at a position closest to the light source transmits at least a portion of the substantially parallel light incident on the light incident surface in the second direction and reflects the remaining portion in the first direction, and the second optical element onto which the light reflected in the first direction is incident reflects at least a portion of the substantially parallel light in the second direction and transmits the remaining portion in the first direction; The lighting device according to claim 1 .

6. a cover that covers the light exit sides of the plurality of second optical elements; the cover has an optical processing for directing the substantially parallel light guided in the second direction downward from a plane determined by the first direction and the second direction. The lighting device according to claim 1 .

7. a plurality of units each formed of the light source, the first optical element, and the second optical element; A plurality of the units are arranged along the first direction.

7. The lighting device according to claim 1.

8. The plurality of light incident surfaces are inclined at an angle of 40° to 50° with respect to the first direction. The lighting device according to any one of claims 1 to 7.

9. A light source; a first optical element that converts the light emitted from the light source into substantially parallel light; a plurality of second optical elements arranged in a first direction; a first array of the plurality of second optical elements arranged in the first direction; and a second array including the plurality of second optical elements arranged in parallel with the first array; and each of the plurality of second optical elements has a light incident surface; the second optical element guides at least a portion of the substantially parallel light incident on the light incident surface in a second direction intersecting with the first direction, and guides another portion of the substantially parallel light in the first direction; the first array and the second array project substantially parallel light incident on the light incident surface in opposite directions along the second direction; Lighting equipment.

10. In the first array and the second array, the second optical elements are arranged so as to be offset in opposite directions from each other as the second optical elements are spaced apart from the light source.

10. The lighting device according to claim 9.

11. the light incident surfaces of the plurality of second optical elements in the first array and the light incident surfaces of the plurality of second optical elements in the second array are inclined in opposite directions to each other with respect to the first direction; 11. The lighting device according to claim 9 or 10.

12. A display board and a stereoscopic display sheet disposed on the display board; The lighting device according to claim 1 , which is disposed on the display board along one side of the display board; having Display device.

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