Holographic optical element, illumination apparatus, and sensor

Abstract

To provide a holographic optical element capable of increasing irradiation range while keeping the size of the illumination apparatus down.SOLUTION: A holographic optical element in an embodiment includes: a transparent substrate 11; an incident hologram 12 placed on the transparent substrate 11 for propagating incident light 2 into the transparent substrate 11; and an emitting hologram 13 placed on the transparent substrate 11 for diffracting light propagating in the transparent substrate 11 to emit from the transparent substrate 11. The incident hologram 12 diffracts the incident light 2 in multi-direction and emits the incident light 2 so that the diffracted incident light 2 achieves total reflection within the transparent substrate 11.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a holographic optical element, an illumination device, and a sensor. [Background technology]

[0002] Conventionally, optical systems using holographic optical elements in light-guiding members have been known. For example, in an imaging device disclosed in Patent Document 1, incident light is diffracted and totally reflected by a first holographic optical element, guided in the light-guiding member, and then diffracted and reflected by a second holographic optical element and emitted to the outside. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-281765 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the imaging device of Patent Document 1, the first and second holographic optical elements are disposed on opposing surfaces of a light-guiding member, and are spaced apart in the width direction of the light-guiding member so as not to face each other.

[0005] A typical hologram optical element diffracts light in only one direction. Therefore, when the hologram optical element of Patent Document 1 is used in an illumination device, the emission range of the illumination device can be expanded by, for example, increasing the distance between the first and second hologram optical elements in the width direction of the light guide member or increasing the length of the light guide member in the thickness direction. In either case, the size of the light guide member increases, and therefore the size of the illumination device increases.

[0006] In view of the above, an object of the present disclosure is to provide a hologram optical element, an illumination device, and a sensor that can expand the irradiation range while reducing the size of the illumination device in an illumination device that uses a hologram optical element. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, a holographic optical element according to one embodiment of the present disclosure comprises a first transparent substrate, an input hologram provided on the first transparent substrate and causing incident light to propagate within the first transparent substrate, and an output hologram provided on the first transparent substrate and diffracting the light propagating within the first transparent substrate so that it exits from the first transparent substrate, wherein the input hologram diffracts the incident light in multiple directions and exits the incident light so that the diffracted incident light is totally reflected within the first transparent substrate. Effect of the Invention

[0008] According to the present disclosure, it is possible to expand the illumination range while suppressing the size of the lighting device. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of a hologram optical element according to a first embodiment. [Diagram 2] FIG. 1 is a cross-sectional view of a hologram optical element according to a first embodiment. [Diagram 3] FIG. 2 is a plan view of an entrance hologram according to the first embodiment. [Figure 4] FIG. 2 is a plan view of an exit hologram according to the first embodiment. [Diagram 5] FIG. 1 is a cross-sectional view of a hologram optical element according to a first embodiment. [Figure 6] FIG. 11 is a cross-sectional view of a hologram optical element according to a second embodiment. [Figure 7] FIG. 11 is a plan view of an entrance hologram according to the third embodiment. [Figure 8] 13A and 13B are diagrams illustrating a hologram optical element according to a fourth embodiment. [Figure 9]FIG. 13 is a cross-sectional view of a hologram optical element according to a fifth embodiment. [Figure 10] FIG. 13 is a cross-sectional view of a hologram optical element according to a sixth embodiment. [Figure 11] FIG. 13 is a cross-sectional view of a hologram optical element according to a modified example of the sixth embodiment. [Figure 12] FIG. 13 is a block diagram of an illumination device according to a seventh embodiment. [Figure 13] FIG. 13 is a block diagram of a sensor according to an eighth embodiment. [Figure 14] FIG. 11 is a perspective view of another example of the hologram optical element. [Figure 15] FIG. 11 is a plan view of another example of an incident hologram. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings. The following description of the preferred embodiments is essentially merely illustrative and is not intended to limit the present invention, its applications, or its uses. In the following description, the same parts are given the same reference numerals, and detailed descriptions will be omitted as appropriate.

[0011] The volume phase hologram used in this disclosure is different from a two-dimensional diffraction grating with fine periodic irregularities on the surface, and records a three-dimensional refractive index distribution in a sinusoidal shape within a volume. By controlling the direction and period of this sinusoidal wave and the amplitude of the refractive index difference, it is possible to control the light distribution of the volume phase hologram.

[0012] (First embodiment) Fig. 1 is a perspective view of a hologram optical element according to a first embodiment. In the following description, the traveling direction of incident light 2 (thickness direction of hologram optical element 1) is defined as the Y direction, one width direction of hologram optical element 1 is defined as the X direction, and the direction perpendicular to the X direction and Y direction (the other width direction of hologram optical element 1) is defined as the Z direction. In Fig. 1 and other figures, each light beam is appropriately illustrated by an arrow or the like.

[0013] 1, a hologram optical element 1 receives incident light 2 and emits output light 3. The XZ cross-sectional shape of the output light 3 is different from the XZ cross-sectional shape of the incident light 2. In other words, the hologram optical element 1 has the function of changing the cross-sectional shape of the incident light 2 and emitting the output light 3.

[0014] 2 is a cross-sectional view of the hologram optical element according to the first embodiment. As shown in FIG. 2, the hologram optical element 1 includes a transparent substrate 11, an entrance hologram 12, and an exit hologram 13.

[0015] The transparent substrate 11 (first transparent substrate) is a flat plate with high transmittance. The transparent substrate 11 is made of, for example, quartz, optical glass, etc. The transparent substrate 11 has surfaces 11a and 11b which are flat surfaces facing each other.

[0016] Incident hologram 12 is a transmission-type volume phase hologram arranged on surface 11a of transparent substrate 11. Incident hologram 12 is a hologram in which a predetermined refractive index distribution is recorded. Incident hologram 12 receives incident light 2 and emits propagating light 4 to transparent substrate 11.

[0017] Exit hologram 13 is a transmission-type volume phase hologram disposed on surface 11b of transparent substrate 11. Exit hologram 13 is a hologram in which a predetermined refractive index distribution is recorded. Exit hologram 13 receives propagating light 4 and emits exit light 3.

[0018] Next, the propagation of light within the hologram optical element 1 will be described.

[0019] First, incident light 2 is incident on incident hologram 12. Upon receiving incident light 2, incident hologram 12 diffracts incident light 2 and emits propagating light 4 to transparent substrate 11.

[0020] FIG. 3 is a plan view of the incident hologram according to the first embodiment. As shown in FIG. 3, when the incident hologram 12 is viewed from the Y direction, interference fringes are formed concentrically around the center. Due to the interference fringes, the incident light 2 incident on the incident hologram 12 is diffracted so as to spread outward from the center when the hologram optical element 1 is viewed in a plan view. The diffracted incident light 2 spreads outward concentrically from the center in the plan view of the hologram optical element 1 as propagating light 4. That is, the incident hologram 12 does not diffract light in only one direction, but diffracts the incident light 2 in multiple directions. In FIG. 2, the incident light 2 is diffracted by the incident hologram 12 and is output to the transparent substrate 11 as propagating light 41, 42. In addition, the output angles of the propagating light 41, 42 are set so that the propagating light 41, 42 are totally reflected when the incident hologram 12 is incident on the transparent substrate 11 and the output hologram 13.

[0021] When the propagating lights 41 and 42 enter the emission hologram 13, a part of them is emitted as the exit light 3, and the remaining part is totally reflected by the surface of the emission hologram 13 and propagates within the transparent substrate 11 as the propagating light 4. In Fig. 2, the propagating lights 41 and 42 are partially emitted as the exit light 31 and 32, respectively, and the remaining part propagates within the transparent substrate 11 as the propagating light 43 and 44.

[0022] Thereafter, the propagating lights 43 and 44 are totally reflected by the surface 11a of the transparent substrate 11, and then enter the exit hologram 13 again. When the propagating lights 43 and 44 enter the exit hologram 13, like the propagating lights 41 and 42, a part of the propagating lights 43 and 44 is emitted as the exit light 3, and the remaining part is totally reflected by the exit hologram 13 and propagates through the transparent substrate 11 as the propagating light 4. In FIG. 2, the propagating lights 43 and 44 are partially emitted as the exit light 33 and 34, respectively, and the remaining part propagates through the transparent substrate 11 as the propagating lights 45 and 46. Thereafter, the propagating light 4 propagates through the hologram optical element 1 while being totally reflected within the transparent substrate 11, and a part of it is emitted as the exit light 3 every time it enters the exit hologram 13.

[0023] FIG. 4 is a plan view of the emission hologram according to the first embodiment. As shown in FIG. 4, when viewed from the Y direction, the emission hologram 13 has interference fringes formed concentrically around the center. Due to the interference fringes, the emission hologram 13 emits the emission light 3 so that the emission light 3 has the same optical axis direction in any region. In addition, the optical axis direction of the emission light 3 at this time is approximately the same as the optical axis direction of the incident light 2 at the center of the cross section. In FIG. 2, the optical axes of the incident light 2 and the emission lights 31 to 34 are approximately the same in the Y direction. Here, it is desirable that the deviation of the optical axes of the incident light 2 and the emission light 3 is at least equal to or less than the width of the incident hologram 12 in the Z direction, and specifically, is desirably 10 mm or less. In this embodiment, the optical axis direction of the incident light 2 at the center of the cross section is approximately the same as the optical axis direction in any region of the cross section of the emission light 3, but it may be approximately the same as the optical axis direction in any part of the cross section of the emission light 3.

[0024] Fig. 5 is a cross-sectional view of the holographic optical element according to the first embodiment. In Fig. 2, for the sake of explanation, each light beam is shown as an arrow, but in reality, each light beam has a certain width as shown in Fig. 5. Note that in Fig. 5, the emitted light beams 31 and 33 are omitted.

[0025] In Fig. 5, the exit light 3 emitted by the exit hologram 13 has a certain width in the Z direction. Therefore, if the distance between the surface 11a of the transparent substrate 11 and the exit surface of the exit hologram 13 is large, the distance that the propagating light 4 travels from when it enters the exit hologram 13 until it re-enters the exit hologram 13 becomes large, resulting in a gap between adjacent exit lights 3 (exit lights 32, 34 in Fig. 5). This results in an area from which light is not emitted from part of the exit surface of the hologram optical element 1.

[0026] Therefore, it is desirable to reduce the area from which light is not emitted from the exit surface of hologram optical element 1. Specifically, assuming that the diameter of incident light 2 is D, the diffraction angle at entrance hologram 12 is θ, and the distance between surface 11a of transparent substrate 11 and the exit surface of exit hologram 13 is t, then

[0027]

number

[0028] It is desirable that:

[0029] With the above configuration, the hologram optical element according to this embodiment includes a transparent substrate 11 (first transparent substrate), an input hologram 12 provided on the transparent substrate 11 to propagate the incident light 2 into the transparent substrate 11, and an output hologram 13 provided on the transparent substrate 11 to diffract the light propagating in the transparent substrate 11 so as to be output from the transparent substrate 11. The input hologram 12 diffracts the incident light 2 in a plurality of directions, and outputs the incident light 2 so that the diffracted incident light 2 is totally reflected in the transparent substrate 11. As a result, since the input hologram 12 diffracts the incident light 2 in a plurality of directions, it is not necessary to displace the input hologram 12 and the output hologram 13 in a planar view (X direction or Z direction), and the range irradiated with the incident light 2 by the input hologram 12 can be expanded. Therefore, by using the hologram optical element according to this embodiment in an illumination device, the illumination range can be expanded while suppressing the size of the illumination device.

[0030] Second embodiment Fig. 6 is a cross-sectional view of the holographic optical element according to the second embodiment. In Fig. 6, emission hologram 13 emits emission light beams 32a and 34a as emission light beam 3. Note that in Fig. 6, emission light beam 3 on the upper side of the drawing is omitted.

[0031] 6, the intensity distribution of the output light 3 is uniform. Specifically, a portion of the propagating light 42 is output from a region 132 of the output hologram 13 as output light 32a, and a portion of the propagating light 44 is output from a region 133 of the output hologram 13 as output light 34a.

[0032] Here, the amount of emitted light 32a is I 32a Let A be the amount of propagating light 42 and η be the diffraction efficiency in region 132.

[0033]

number

[0034] In this case, the amount of light of the propagating light 44 is AA×η1. If the diffraction efficiency in the region 133 is η2, then

[0035]

number

[0036] Then, the amount of light I of the emitted light 32a is 32a and the amount of light I of the emitted light 34a 34a This makes it possible to make the intensity distribution of the emitted light 3 constant.

[0037] Even when the number of diffractions of propagating light 4 increases, light with a uniform intensity distribution can be emitted from hologram optical element 1 by similarly appropriately adjusting the diffraction efficiency for each region of output hologram 13.

[0038] Third embodiment Fig. 7 is a plan view of an incident hologram according to the third embodiment. In Fig. 7, the propagating light 4 diffracted by the incident hologram 12 is illustrated as propagating light 4a to 4d. Note that the propagating light 4a is diffracted at the center of the incident hologram 12, and the propagating light 4a propagates in the +X direction, the propagating light 4b in the +Z direction, the propagating light 4c in a direction that forms 45° with the X direction, and the propagating light 4d in a direction that forms α° with the X direction.

[0039] As shown in FIG. 7, the exit hologram 13 is formed to be approximately square in plan view, so that among the distances from the center to the periphery, the distances from the center to the X direction and the Z direction are the shortest, and the distance from the center to the direction forming 45° with the X direction (Z direction) is the longest. That is, among the propagating lights 4a to 4d, the length of the propagating light 4a and 4b is the shortest, and the length of the propagating light 4c is the longest. For this reason, in order to make the intensity distribution of the exit light 3 constant, the exit hologram 13 needs to have a higher diffraction efficiency in the direction in which the propagating light 4c propagates than the diffraction efficiency in the direction in which the propagating lights 4a and 4b propagate. Specifically, the distance from the center of the entrance hologram 12 to the periphery of the exit hologram 13 in the direction forming α° with the X direction in plan view is defined as L α , L α If the diffraction efficiency in the direction (such as the X direction) where is the smallest is γ0, then the diffraction efficiency in the diffraction direction α, γ α teeth,

[0040]

number

[0041] This makes it possible to make the intensity distribution of the emitted light 3 constant.

[0042] (Fourth embodiment) Fig. 8 is a diagram for explaining a hologram optical element according to a fourth embodiment. Specifically, Fig. 8(a) is a cross-sectional view of a hologram optical element 1, Fig. 8(b) is a graph showing the amount of incident light 2, and Fig. 8(c) is a graph showing the amount of exit light 3.

[0043] As shown in Fig. 8(b), the intensity distribution of the incident light 2 is not constant. Specifically, the amount of light of the incident light 2 is the highest at the center (the center in the Z direction) and the lowest at the outer periphery (the upper and lower ends in the Z direction). Even in such a case, the intensity distribution of the output light 3 can be made constant.

[0044] As shown in FIG. 8(a), the emission hologram 13 emits the emission lights 32b and 34b as the emission light 3. Specifically, a part of the propagating light 42 is emitted from the region 134 of the emission hologram 13 as the emission light 32b, and a part of the propagating light 44 is emitted from the region 135 of the emission hologram 13 as the emission light 34b. Here, the regions 134 and 135 overlap in the region 136. Therefore, the amount of the emission light 3 in the region 136 is the sum of the amounts of the light at the ends of the regions 134 and 135 (see FIG. 8(c)). Therefore, even if the intensity distribution of the incident light 2 is not constant, the intensity distribution of the emission light 3 can be made constant by overlapping the emission regions of the emission lights 3 with each other or by appropriately setting the diffraction efficiency of each region. The region 136 can be set by adjusting the thickness of the transparent substrate 11.

[0045] Fifth embodiment Fig. 9 is a cross-sectional view of a holographic optical element according to a fifth embodiment. In Fig. 9, emission holograms 13a and 13b are provided on surface 11a of transparent substrate 11. Note that emission holograms 13a and 13b in Fig. 9 are reflective volume phase holograms, and emission holograms 13a and 13b are reflective volume phase holograms.

[0046] 9, a portion of incident light 2 incident on incident hologram 12a passes through incident hologram 12a to become exit light 3, and the remainder is diffracted to become propagating light 4. Specifically, a portion of incident light 2 passes through incident hologram 12 and is emitted from surface 11b of transparent substrate 11 as exit light 35. The remainder of incident light 2 is diffracted by incident hologram 12 to become propagating light 45, 46 that propagate within transparent substrate 11.

[0047] Then, the propagating light 45, 46 is totally reflected by the surface 11b of the transparent substrate 11 and enters the exit holograms 13a, 13b. When the propagating light 45 enters the exit hologram 13a, a part of it is reflected by the surface of the exit hologram 13a to become the exit light 36, and the remainder is totally reflected to become the propagating light 47 that propagates within the transparent substrate 11. Similarly, when the propagating light 46 enters the exit hologram 13b, a part of it is reflected by the surface of the exit hologram 13b to become the exit light 37, and the remainder is totally reflected to become the propagating light 48 that propagates within the transparent substrate 11.

[0048] Thereafter, the propagating lights 47 and 48 are totally reflected by the surface 11b of the transparent substrate 11, and then re-enter the exit holograms 13a and 13b, respectively. When the propagating lights 47 and 48 enter the exit holograms 13a and 13b, like the propagating lights 45 and 46, a part of the propagating lights 47 and 48 is emitted as the exit light 38 and 39, and the remaining part is totally reflected by the exit holograms 13a and 13b, and propagates within the transparent substrate 11 as the propagating light 4. Thereafter, the propagating light 4 propagates within the hologram optical element 1 while being totally reflected within the transparent substrate 11, and a part of it is emitted as the exit light 3 every time it enters the exit hologram 13.

[0049] In FIG. 9, entrance hologram 12a and exit holograms 13a and 13b are disposed only on one surface (surface 11a) of transparent substrate 11, which makes it easy to manufacture the holographic optical element.

[0050] Incidentally, the entrance hologram 12a and the exit holograms 13a and 13b may be formed on the same film.

[0051] Also in FIG. 9, by using a configuration similar to that of the first to fourth embodiments, the intensity distribution of the emitted light 3 can be made constant.

[0052] Sixth embodiment Fig. 10 is a cross-sectional view of a holographic optical element according to a sixth embodiment. In Fig. 10, incident hologram 12b and exit holograms 13c and 13d are provided on surface 11b of transparent substrate 11. Incident hologram 12a in Fig. 10 is a reflective volume phase hologram, and exit holograms 13c and 13d are transmissive volume phase holograms.

[0053] In FIG. 10, incident light 2 enters incident hologram 12b through transparent substrate 11. A portion of incident light 2 that enters incident hologram 12b passes through incident hologram 12b to become exit light 3, and the remainder is diffracted to become propagating light 4. Specifically, incident light 2 passes through incident hologram 12b and is emitted from surface 11b of transparent substrate 11 as exit light 35a. The remainder of incident light 2 is diffracted by incident hologram 12b to become propagating light 45a, 46a that propagate within transparent substrate 11.

[0054] Then, the propagating light 45a, 46a is totally reflected by the surface 11a of the transparent substrate 11 and enters the exit holograms 13c, 13d. When the propagating light 45a enters the exit hologram 13c, a part of the propagating light 45a is reflected by the surface of the exit hologram 13c to become the exit light 36a, and the remaining part is totally reflected to become the propagating light 47a that propagates within the transparent substrate 11. Similarly, when the propagating light 46a enters the exit hologram 13d, a part of the propagating light 46a is reflected by the surface of the exit hologram 13d to become the exit light 37a, and the remaining part is totally reflected to become the propagating light 48a that propagates within the transparent substrate 11.

[0055] Thereafter, the propagating lights 47a and 48a are totally reflected by the surface 11a of the transparent substrate 11, and then re-enter the exit holograms 13c and 13d, respectively. When the propagating lights 47a and 48a enter the exit holograms 13c and 13d, like the propagating lights 45a and 46a, a part of the propagating lights 47a and 48a is emitted as the exit lights 38a and 39a, and the remaining part is totally reflected by the exit holograms 13c and 13d, and propagates within the transparent substrate 11 as the propagating light 4. Thereafter, the propagating light 4 propagates within the hologram optical element 1 while being totally reflected within the transparent substrate 11, and a part of it is emitted as the exit light 3 every time it enters the exit hologram 13.

[0056] In FIG. 10, entrance hologram 12b and exit holograms 13c and 13d are disposed only on one surface (surface 11b) of transparent substrate 11, which makes it easy to manufacture the holographic optical element.

[0057] Incidentally, the entrance hologram 12b and the exit holograms 13c and 13d may be formed on the same film.

[0058] Also in FIG. 10, by using a configuration similar to that of the first to fourth embodiments, the intensity distribution of the emitted light 3 can be made constant.

[0059] Fig. 11 is a cross-sectional view of a hologram optical element according to a modified example of the sixth embodiment. In Fig. 11, a transparent substrate 14 (second transparent substrate) is provided on the surface of incident hologram 12a and exit holograms 13c, 13d opposite to surface 11b on which transparent substrate 11 is provided. That is, incident hologram 12a and exit holograms 13c, 13d are sandwiched between transparent substrates 11, 14. This can improve the reliability of hologram optical element 1 in terms of heat resistance, water resistance, weather resistance, and the like.

[0060] It should be noted that the transparent substrate 14 does not need to have the same thickness as the transparent substrate 11 since it does not have any optical function.

[0061] Also in the first to fourth embodiments, similarly to the fourth embodiment, a transparent substrate may be disposed on the outside of the entrance hologram and the exit hologram.

[0062] Seventh embodiment Fig. 12 is a block diagram of an illumination device according to a seventh embodiment. As shown in Fig. 12, the illumination device according to the sixth embodiment includes a hologram optical element 1, a power supply unit 5, a light source 6, and a control unit 7. The hologram optical element 1 is any of the hologram optical elements according to the first to sixth embodiments described above.

[0063] The power supply unit 5 is connected to, for example, a commercial power source, and supplies power to the light source 6 and the control unit 7 .

[0064] Based on the supplied power, the light source 6 irradiates light onto the hologram optical element 1. The light source 6 is preferably a monochromatic laser light source or LED, but may also be a laser light source or LED that emits light at a plurality of wavelengths.

[0065] The control unit 7 controls the power supplied to the light source 6 to control the light irradiated from the light source 6 to the hologram optical element 1 .

[0066] In FIG. 12, light emitted from the light source 6 via the hologram optical element 1 can be used as illumination light, so that it is possible to illuminate indoors and outdoors, for example.

[0067] The illumination device may include a plurality of each of the hologram optical element 1, the power supply unit 5, the light source 6, and the control unit .

[0068] Eighth embodiment Fig. 13 is a block diagram of a sensor according to the eighth embodiment. As shown in Fig. 13, the sensor according to the sixth embodiment includes a hologram optical element 1, a power supply unit 5, a light source 6, a control unit 7, and a light receiving element 8. The hologram optical element 1 is any of the hologram optical elements according to the first to sixth embodiments described above.

[0069] The power supply unit 5 supplies power to the light source 6, the control unit 7, and the light receiving element 8.

[0070] Based on the supplied power, the light source 6 irradiates light onto the hologram optical element 1. The light source 6 is preferably a monochromatic laser light source or LED, but may also be a laser light source or LED that emits light at a plurality of wavelengths.

[0071] The control unit 7 controls the power supplied to the light source 6 to control the light irradiated from the light source 6 to the hologram optical element 1 .

[0072] The light receiving element 8 is an element such as a photoelectric element or an image sensor that converts light into a signal.

[0073] In Fig. 13, light emitted from a light source 6 via a hologram optical element 1 is irradiated onto a detection object 9. The light irradiated onto the detection object 9 is reflected and received by a light receiving element 8. This makes it possible to detect the detection object 9. In other words, the detection object 9 can be used as a sensor (for example, a displacement sensor or a foreign object inspection sensor) that detects the detection object 9.

[0074] (Other embodiments) The cross-sectional shape of the outgoing light 3 is not limited to the shape shown in FIG. 1. For example, as shown in FIG. 14(a) and (b), it may be a circle or a star. In each of the above embodiments, the cross-sectional shape of the outgoing light 3 can be any shape, such as a circle, a star, an ellipse, or a free curved surface, by appropriately changing the shape and diffraction efficiency of the incident hologram and the outgoing hologram. That is, the cross-sectional shape of the outgoing light 3 may be one in which the dimensions in multiple directions of the cross-sectional shape of the incident light 2 are changed. The cross-sectional shape of the outgoing light 3 may be appropriately changed depending on the purpose of use. For example, in laser illumination, a wall surface may generally be irradiated with rectangular light, but it may be circular for reasons such as performance and design, as in the case of a spotlight. The shape of the incident hologram 12 does not necessarily have to be circular and may be any shape. The transparent substrate 11 does not necessarily have to be circular and may be any shape. The incident light 2 does not necessarily have to be parallel light, and may be divergent light or convergent light. The emitted light 3 does not necessarily have to be parallel light, but may be divergent or convergent light.

[0075] Furthermore, the shape of the interference fringes recorded in incident hologram 12 is not limited to that shown in Fig. 3. For example, incident hologram 12 may have hexagonal interference fringes as shown in Fig. 15. In other words, incident hologram 12 may have any type of interference fringes as long as it can magnify incident light 2, and may have a curved line, a combination of multiple straight lines, or a complex three-dimensional refractive index distribution.

[0076] In each of the above embodiments, the input hologram and the output hologram are not limited to a volume phase type hologram optical element. For example, the input hologram and the output hologram may be an embossed type hologram optical element, and any type of hologram optical element may be used as long as the hologram optical element 1 in each of the above embodiments can be realized. [Industrial Applicability]

[0077] The holographic optical element of the present disclosure can be applied to lighting devices, sensors, imaging devices, bed-mounted displays, head-up displays, and the like. [Explanation of symbols]

[0078] 1 Holographic optical elements 2 Incident light 3. Emitted light 4. Propagation of light 11 Transparent substrate (first transparent substrate) 12, 12a, 12b Incident hologram 13, 13a-13d Emitting hologram 14 Transparent substrate (second transparent substrate)

Claims

1. A first transparent substrate; an incident hologram provided on the first transparent substrate, the incident light propagating within the first transparent substrate; an emission hologram provided on the first transparent substrate and diffracting light propagating through the first transparent substrate so as to be emitted from the first transparent substrate; The incident hologram diffracts incident light in a plurality of directions and outputs the incident light such that the diffracted incident light is totally reflected within the first transparent substrate.

2. The holographic optical element according to claim 1 , wherein an optical axis direction of the central portion of the cross section of the incident light substantially coincides with an optical axis direction of at least any partial region of the cross section of the outgoing light emitted from the first transparent substrate.

3. 2. The holographic optical element according to claim 1, wherein a cross-sectional shape of the outgoing light emitted from the first transparent substrate is obtained by changing dimensions in a plurality of directions of the cross-sectional shape of the incident light.

4. The holographic optical element according to claim 1 , wherein the entrance hologram and the exit hologram are provided on the same surface of the first transparent substrate.

5. 2. The holographic optical element according to claim 1, further comprising a second transparent substrate provided on a surface of the entrance hologram and the exit hologram opposite to a surface on which the first transparent substrate is provided.

6. An illumination device comprising the holographic optical element according to any one of claims 1 to 5.

7. A sensor comprising the hologram optical element according to any one of claims 1 to 5.

Images