Illuminating device and method for manufacturing illuminating device

Abstract

To provide an illuminating device that can project a desired projection pattern.SOLUTION: An illuminating device 10 includes a coherent light source 20, a shaping optical system 25 for shaping coherent light emitted from the coherent light source 20, and a diffractive optical element 30 including an uneven surface 31 for diffracting the coherent light shaped by the shaping optical system 25. The illuminating device 10 illuminates by using the coherent light diffracted by the uneven surface 31 of the diffractive optical element 30. The uneven surface 31 faces an enclosed space CR.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] The present disclosure relates to a lighting device and a method for manufacturing the lighting device.

Background Art

[0002] For example, as disclosed in Patent Document 1, a lighting device that projects a projection pattern onto a projection surface is known. The lighting device of Patent Document 1 irradiates the projection surface with coherent light diffracted by the uneven surface of a diffractive optical element.

[0003] Recently, there has been a demand to use lighting devices outdoors. When a lighting device is used outdoors, foreign substances such as dust containing dirt and water droplets are likely to adhere to the uneven surface. When foreign substances such as dust and water droplets adhere to the uneven surface, the optical path of the coherent light incident on the uneven surface can be directed in an unintended direction. At this time, the pattern projected onto the projection surface cannot be observed as the intended desired projection pattern. The projection surface cannot be illuminated with the desired projection pattern.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present disclosure is to provide a lighting device capable of projecting a desired projection pattern.

Means for Solving the Problems

[0006] One embodiment of the present disclosure relates to the following [1] to

[26] .

[0007] [1] A coherent light source, A shaping optical system that shapes the coherent light emitted from the coherent light source, A diffractive optical element includes an uneven surface that diffracts the coherent light shaped by the shaping optical system, Illumination is performed using the coherent light diffracted by the uneven surface of the diffractive optical element. The aforementioned uneven surface faces a sealed, enclosed space; this is a lighting device.

[0008] [2] A light-transmitting plate positioned opposite the diffractive optical element, The system further comprises a light-transmitting plate and a holding member for holding the diffractive optical element, The lighting device of [1] wherein the sealed space is partitioned by the holding member, the diffractive optical element, and the light-transmitting plate.

[0009] [3] The retaining member has a through hole, The diffractive optical element is joined to the holding member such that it closes the through hole from one side. The light-transmitting plate is joined to the holding member such that it closes the through hole from the other side, in the lighting device of [2].

[0010] [4] A coherent light source that emits coherent light, A shaping optical system for shaping the coherent light emitted from the aforementioned coherent light source, A diffractive optical element including an uneven surface that diffracts the coherent light shaped by the shaping optical system, A light-transmitting plate is positioned facing the diffractive optical element, The system comprises a light-transmitting plate and a holding member for holding the diffractive optical element, The retaining member has a through hole, The light-transmitting plate is joined to the holding member so as to close the through hole from one side. The diffractive optical element is joined to the holding member such that it closes the through hole from the other side. The aforementioned uneven surface is a lighting device facing the light-transmitting plate.

[0011] [5] The lighting device of [4], wherein the holding member is plate-shaped.

[0012] [6] A casing for housing the holding member, and a first sealing member for sealing the peripheral edge of the holding member and the casing, and further includes the lighting device according to any one of [2] to [5].

[0013] [7] The holding member includes a concave portion for housing the peripheral edge of the light-transmitting plate at a position around the through-hole, and is the lighting device according to any one of [3] to [5].

[0014] [8] The holding member includes a second concave portion for housing the peripheral edge of the diffractive optical element at a position around the through-hole, and is the lighting device according to any one of [3] to [5].

[0015] [9] Further includes a second holding member fixed to the holding member, The peripheral edge of the diffractive optical element is held by the holding member and the second holding member, and is the lighting device according to any one of [2] to [5].

[0016]

[10] Further includes a second sealing member for sealing between the peripheral edge of the diffractive optical element and the second holding member, and is the lighting device according to [9].

[0017]

[11] Further includes a light-transmitting plate disposed facing the diffractive optical element, The light-transmitting plate is joined to the diffractive optical element and partitions the sealed space therebetween, and is the lighting device according to [1].

[0018]

[12] The diffractive optical element includes a plate-shaped portion including the concavo-convex surface, and a protruding portion protruding from the plate-shaped portion toward the light-transmitting plate, The protruding portion is joined to the light-transmitting plate, and is the lighting device according to

[11] .

[0019]

[13] The light-transmitting plate includes a plate-shaped portion facing the concavo-convex surface, and a protruding portion protruding from the plate-shaped portion toward the diffractive optical element, The lighting device of

[11] in which the protrusion is joined to the translucent plate.

[0020]

[14] A coherent light source that emits coherent light, A shaping optical system that shapes the coherent light emitted from the coherent light source, A diffractive optical element including a concavo-convex surface that diffracts the coherent light shaped by the shaping optical system, A translucent plate disposed facing the concavo-convex surface of the diffractive optical element, and The lighting device in which the translucent plate is joined to the diffractive optical element in a circumferential portion surrounding the concavo-convex surface.

[0021]

[15] Further including a cover through which the coherent light diffracted by the diffractive optical element passes, The lighting device according to any one of [1] to

[14] , in which the cover is disposed facing the diffractive optical element.

[0022]

[16] The lighting device according to any one of [2] to

[14] , in which the distance between the concavo-convex surface of the diffractive optical element and the translucent plate is 0.5 mm or more and 3.5 mm or less.

[0023]

[17] The lighting device according to any one of [2] to

[14] , in which the translucent plate includes an antireflection layer that constitutes a surface.

[0024]

[18] The lighting device according to any one of [1] to [3],

[11] to

[13] , in which the sealed space is filled with a dry gas.

[0025]

[19] The lighting device according to any one of [1] to [3],

[11] to

[13] , in which the sealed space is a vacuum.

[0026]

[20] The lighting device according to any one of [1] to

[19] , in which the coherent light diffracted by the concavo-convex surface passes through the diffractive optical element.

[0027]

[21] The diffractive optical element includes an anti-reflective layer forming the surface opposite to the uneven surface, any of the lighting devices [1] to

[20] .

[0028]

[22] The diffractive optical element includes a hydrophilic layer that constitutes the uneven surface, any of the lighting devices from [1] to

[21] .

[0029]

[23] A lighting device of any of [1] to [3],

[11] to

[13] , wherein a desiccant is provided within the sealed space.

[0030]

[24] Any of the illumination devices [1] to

[23] wherein the coherent light is diffracted in a direction nonparallel to the zeroth-order light transmitted through the diffractive optical element by the uneven surface of the diffractive optical element.

[0031] A method for manufacturing a lighting device as described in any of

[25]

[11] to

[14] , Preparation steps include preparing a first plate containing a plurality of diffractive optical elements on one side, and a second plate containing the light-transmitting plate, A bonding step in which the second plate is bonded to one surface of the first plate so as to cover the plurality of diffractive optical elements, A method for manufacturing an illumination device, comprising: a cutting step of cutting the first plate, which is joined to the second plate, for each of the diffractive optical elements.

[0032]

[26] A method for manufacturing the lighting device of

[25] , wherein in the step of joining the second plate to the first plate, the second plate is joined to the first plate in a circumferential manner around each uneven surface. [Effects of the Invention]

[0033] According to this disclosure, a desired projection pattern can be projected. [Brief explanation of the drawing]

[0034] [Figure 1A] Figure 1A is a diagram illustrating one embodiment, and is a perspective view showing the schematic configuration of a lighting device. [Figure 1B]Figure 1B is a side view showing an example of a diffractive optical element assembly and the illuminated area of ​​an illumination device. [Figure 2] Figure 2 is a cross-sectional view showing another example of a lighting device. [Figure 3] Figure 3 is an enlarged view of section A of the lighting device in Figure 2. [Figure 4] Figure 4 shows the first holding member of the lighting device shown in Figure 3, and the light-transmitting plate held by the first holding member. [Figure 5] Figure 5 shows the first holding member of the lighting device shown in Figure 3, and the diffractive optical element held by the first holding member. [Figure 6] Figure 6 shows the second holding member of the lighting device shown in Figure 3. [Figure 7] Figure 7 is a cross-sectional view showing yet another example of a lighting device. [Figure 8] Figure 8 is a cross-sectional view showing yet another example of a lighting device. [Figure 9] Figure 9 is a cross-sectional view showing another example of the diffractive optical element assembly shown in Figure 1B. [Figure 10] Figure 10 is a cross-sectional view showing yet another example of the diffractive optical element assembly shown in Figure 1B. [Figure 11] Figure 11 is a cross-sectional view showing yet another example of the diffractive optical element assembly shown in Figure 1B. [Figure 12] Figure 12 is a diagram illustrating an example of a manufacturing method for an illumination device including the diffractive optical element assembly shown in Figure 9. [Figure 13] Figure 13 is a diagram illustrating an example of a manufacturing method for an illumination device including the diffractive optical element assembly shown in Figure 9. [Figure 14] Figure 14 is a diagram illustrating an example of a manufacturing method for an illumination device including the diffractive optical element assembly shown in Figure 9. [Modes for carrying out the invention]

[0035] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In the drawings attached to this specification, the scale and aspect ratios of the dimensions have been appropriately changed and exaggerated from those of the actual objects for the sake of illustration and ease of understanding.

[0036] In this specification, terms such as "parallel," "orthogonal," and "identical," as well as values ​​of length and angle, which specify shapes, geometric conditions, and their degrees, should not be interpreted in a strict sense, but rather to include a range that can be expected to function similarly.

[0037] To clarify directional relationships between drawings, some drawings use arrows to indicate the first direction D1, the second direction D2, and the third direction D3 as common directions across the drawings. The tip of the arrow represents the first direction in each direction. Arrows pointing towards the viewer from the drawing plane, perpendicular to the plane of the drawing, are indicated by a symbol of a dot inside a circle, as shown in Figure 2, for example. Arrows pointing away from the drawing plane, perpendicular to the plane of the drawing, are indicated by a symbol of an "x" inside a circle, as shown in Figure 1B, for example.

[0038] Figures 1A to 6 are diagrams illustrating one embodiment. Of these, Figure 1A is a perspective view showing the schematic configuration of the lighting device 10. Figure 2 is a cross-sectional view showing a specific configuration that may be applied to the lighting device 10. The lighting device 10 according to this embodiment includes a coherent light source 20, a shaping optical system 25, and a diffractive optical element 30. The shaping optical system 25 shapes the coherent light emitted from the coherent light source 20. The diffractive optical element 30 includes an uneven surface 31 that diffracts the coherent light. The uneven surface 31 diffracts the coherent light shaped by the shaping optical system 25.

[0039] The illumination device 10 projects a projection pattern 90 onto the projection surface 95 using light diffracted by the uneven surface 31. In other words, the illumination device 10 illuminates the projection surface 95 in the shape of the projection pattern 90. The coherent light diffracted by the uneven surface 31 is directed toward the illuminated area 96 on the projection surface 95. When the illuminated area 96 is irradiated with coherent light, the projected projection pattern 90 on the projection surface 95 is observed. That is, the illuminated area 96 is an area on the projection surface 95 that has the same shape as the projection pattern 90.

[0040] In the embodiment described below, measures have been taken to project a desired projection pattern. More specifically, measures have been taken to prevent foreign matter such as dust and water droplets from adhering to the uneven surface 31. This prevents coherent light from being refracted or diffracted in unintended directions due to the influence of foreign matter. Therefore, the lighting device 10 can project a desired projection pattern 90 onto the projection surface 95.

[0041] As shown in the specific example in Figure 2, the lighting device 10 may be portable. That is, the lighting device 10 can be carried by the operator without the use of special means. A portable lighting device 10 can be used in various locations. Such a lighting device 10 may be exposed to wind and rain during use. Therefore, this embodiment, in which the adhesion of foreign matter to the uneven surface 31 is suppressed, is particularly suitable for a portable lighting device 10.

[0042] The projection surface 95 onto which the illumination light from the lighting device 10 is projected is not particularly limited. Examples of projection surfaces 95 onto which the projection pattern 90 is projected include the ground such as roads, sidewalks, sports fields, and parks; water surfaces such as the sea; the exterior and interior walls of buildings such as schools, companies, office buildings, factories, assembly halls, auditoriums, gymnasiums, stadiums, and venues; passageways; floors; and ceilings.

[0043] The shape of the illuminated area 96 and the projection pattern 90 are not particularly limited. In the example shown in Figure 1A, the illuminated area 96 is a linear area extending away from the lighting device 10. The shape of the illuminated area 96 and the projection pattern 90 are not particularly limited. The shape of the illuminated area 96 and the projection pattern 90 may be a pattern representing one or more of the following: letters, pictures, color patterns, symbols, marks, illustrations, characters, or pictograms. The shape of the illuminated area 96 and the projection pattern 90 may also display information, such as direction or orientation.

[0044] The components of a lighting device 10 according to one embodiment will be described below with reference to the illustrated specific example.

[0045] As described above, in one embodiment, the lighting device 10 includes a coherent light source 20, a shaping optical system 25, and a diffractive optical element 30. The lighting device 10 may also include a casing 60 that houses the coherent light source 20, the shaping optical system 25, and the diffractive optical element 30, as shown in the figure.

[0046] In the illustrated example, the lighting device 10 includes a diffractive optical element assembly 30X. The diffractive optical element assembly 30X includes a diffractive optical element 30. As will be described later, the diffractive optical element assembly 30X includes the diffractive optical element 30 in a manner that suppresses the adhesion of foreign matter such as moisture and dust to the uneven surface 31.

[0047] The casing 60 may provide waterproofing to the lighting device 10. To provide waterproofing to the lighting device 10, waterproofing materials such as rubber, gaskets, or adhesives may be provided at the joints and fitting portions of the casing 60.

[0048] In the example shown in Figure 2, the casing 60 includes an outer cylinder portion 61 and an inner cylinder portion 62 housed within the outer cylinder portion 61. In the example shown in Figure 2, the coherent light source 20, the shaping optical system 25, and the diffractive optical element assembly 30X are located within the outer cylinder portion 61. Of these, the coherent light source 20 and the shaping optical system 25 are located within the inner cylinder portion 62.

[0049] The inner cylinder portion 62 has a cylindrical shape with one end closed. The internal dimensions of the inner cylinder portion 62 change via the stepped portion 62s. The internal dimensions of the inner cylinder portion 62 increase as you move away from the closed end towards the first side in the first direction D1. The inner cylinder portion 62 is open at the end opposite to the closed end.

[0050] The coherent light source 20 emits coherent light. Coherent light is light with a uniform wavelength and phase. The coherent light source 20 may emit coherent light in a specific wavelength range. The coherent light may have a single wavelength. The coherent light may be blue light with a wavelength of 445 nm. The coherent light may be blue light with a wavelength of 460 nm. The coherent light may be blue light with a wavelength of 488 nm. The coherent light may be green light with a wavelength of 520 nm. The coherent light may be green light with a wavelength of 530 nm. The coherent light may be red light with a wavelength of 638 nm. The coherent light may be red light with a wavelength of 660 nm. Various types of light sources can be used as the coherent light source 20. A laser light source that emits laser light may be used as the coherent light source 20. A semiconductor laser light source can be given as an example of a laser light source. In the specific example shown in Figure 2, the coherent light source 20 is fixed to one of the closed ends of the inner cylinder portion 62.

[0051] The shaping optical system 25 shapes the coherent light emitted from the coherent light source 20. In the example schematically shown in Figure 1A, the shaping optical system 25 shapes the coherent light emitted from the coherent light source 20 as divergent light into a widened parallel beam. The shaping optical system 25 shown in Figure 1A includes a lens. This lens shapes the divergent beam emitted from the coherent light source 20 into a parallel beam. In this example, the lens constituting the shaping optical system 25 functions as a collimating lens.

[0052] In the specific example shown in Figure 2, the shaping optical system 25 includes a first lens 26, a second lens 27, and a third lens 28. Similar to the shaping optical system 25 shown in Figure 1A, the shaping optical system 25 shown in Figure 2 shapes the coherent light emitted from the coherent light source 20 into a parallel light beam with a widened optical path width. In the specific example shown in Figure 2, the first lens 26, the second lens 27, and the third lens 28 are all housed in an inner cylinder 62. The first lens 26, the second lens 27, and the third lens 28 housed in the inner cylinder 62 are arranged linearly with a gap between them in the first direction D1. Of the shaping optical system 25 housed in the inner cylinder 62, the first lens 26 is closest to the coherent light source 20 in the first direction D1. Of the shaping optical system 25 housed in the inner cylinder 62, the third lens 28 is furthest from the coherent light source 20 in the first direction D1.

[0053] In the specific example shown in Figure 2, the internal dimensions of the inner cylinder portion 62 in the area where the first lens 26 is located, the internal dimensions of the inner cylinder portion 62 in the area where the second lens 27 is located, and the internal dimensions of the inner cylinder portion 62 in the area where the third lens 28 is located are all different. Of these, the internal dimensions of the inner cylinder portion 62 in the area where the first lens 26 is located are the smallest, and the internal dimensions of the inner cylinder portion 62 in the area where the third lens 28 is located are the largest.

[0054] As shown in Figure 2, a gap ring 63 may be provided between the first lens 26 and the second lens 27. The gap ring 63 may control the distance between optical elements, including the shaping optical system 25. The gap ring 63 can suppress relative displacement of optical elements, including the shaping optical system 25, due to vibrations and shocks that may be applied to the illumination device 10. As shown in Figure 2, a gap ring 63 is also provided between the second lens 27 and the third lens 28. A gap ring 63 is also provided between the third lens 28 and the diffractive optical element assembly 30X. The gap ring 63 may be an annular or cylindrical member, for example. As the material of the gap ring 63, a metal such as aluminum may be used, or a resin may be used.

[0055] In the specific example shown in Figure 2, the lighting device 10 includes a battery 64, a circuit 65, and a switch 66. The battery 64 may be a primary battery or a rechargeable secondary battery. The circuit 65 electrically connects the battery 64 and the coherent light source 20 via the switch 66. By operating the switch 66, it is possible to switch between supplying power from the battery 64 to the coherent light source 20 and stopping the power supply from the battery 64 to the coherent light source 20. In the lighting device 10, power may be supplied to the coherent light source 20 by methods other than operating the switch 66. Power may be supplied to the coherent light source 20 from outside the lighting device 10, or the power supply from the battery 64 to the coherent light source 20 may be controlled by a wired or wireless switch signal from outside the lighting device 10.

[0056] The lighting device 10 may include a control unit that controls the supply and cessation of power from the battery 64 to the coherent light source 20. The control unit may control the supply and cessation of power from the battery 64 to the coherent light source 20 by receiving an external electrical signal. The control unit may include a processor such as a CPU (Central Processing Unit). The control unit may receive an external electrical signal via wiring electrically connected to the control unit. The control unit may receive an external electrical signal via electromagnetic waves such as infrared rays.

[0057] As shown in Figure 1B, the diffractive optical element 30 changes the direction of propagation of coherent light shaped by the shaping optical system 25. The diffractive optical element 30 includes an uneven surface 31 that diffracts the coherent light shaped by the shaping optical system 25. The diffractive optical element 30 changes the direction of propagation of coherent light by diffraction at the uneven surface 31. The coherent light whose direction of propagation has been changed by the diffractive optical element 30 is irradiated onto the illuminated area 96 on the projection surface 95. That is, the illumination device 10 illuminates the illuminated area 96 using coherent light diffracted by the uneven surface 31 of the diffractive optical element 30.

[0058] In the example shown in Figure 1A, the projection surface 95 extends in a first direction D1 and a second direction D2. The first direction D1 and the second direction D2 are orthogonal to each other. The lighting device 10 is positioned offset from the projection surface 95 towards the first side in a third direction D3. The third direction D3 is orthogonal to the first direction D1. The third direction D3 is orthogonal to the second direction D2. In the illustrated example, the shape of the illuminated area 96 and the projection pattern 90 have a linear shape. The shape of the illuminated area 96 and the projection pattern 90 are linear, receding from the lighting device 10 in the first direction D1. The shape of the illuminated area 96 and the projection pattern 90 are linear. The shape of the illuminated area 96 and the projection pattern 90 have a longitudinal direction in the first direction D1. The shape of the illuminated area 96 and the projection pattern 90 have a short direction in the second direction D2. In the illustrated example, coherent light from the lighting device 10 is incident on the illuminated area 96 on the projection surface 95 at a relatively large incident angle α, for example, an incident angle α of 45° or more. The coherent light from the lighting device 10 may also be incident at an incident angle α of 60° or more, or at an incident angle α of 80° or more. The incident angle α(°) represents the angle (°) that the direction of propagation of the coherent light toward the illuminated area 96 makes with respect to the normal direction ND of the illuminated area 96. In the illustrated example, the normal direction ND is parallel to the third direction D3.

[0059] The diffractive optical element 30 may be a holographic element. The diffractive optical element 30 may be a relief hologram. By using a holographic element as the diffractive optical element 30, it is possible to design a diffraction pattern that projects light only onto the entire area of ​​a desired region on the projection surface 95 with predetermined position, shape, size, and orientation. The diffractive optical element 30 may be a transmissive holographic element. The diffractive optical element 30 may be a reflective holographic element.

[0060] In designing the diffraction pattern of the uneven surface 31, the illuminated area 96 can be set in real space such that it has a predetermined shape, size, and orientation at a predetermined position relative to the diffractive optical element 30. The position, shape, size, and orientation of the illuminated area 96 on the projection surface 95 depend on the configuration of the uneven surface 31. By adjusting the configuration of the uneven surface 31, the position, contour shape, size, and orientation of the illuminated area 96 on the projection surface 95 can be arbitrarily adjusted. Therefore, in designing the uneven surface 31, the position, shape, size, and orientation of the illuminated area 96 on the projection surface 95 can be determined first. Next, the configuration of the uneven surface 31 can be adjusted so that light can be projected over the entire determined illuminated area 96.

[0061] The diffractive optical element 30 may be fabricated as a computer-generated hologram (CGH). A computer-generated hologram is fabricated by calculating a structure with an arbitrary diffraction pattern on a computer. By using a computer-generated hologram as the diffractive optical element 30, it is possible to eliminate the need to generate object light and reference light using a light source and optical system, and to record interference fringes on the hologram recording material by exposure. The illumination device 10 is assumed to irradiate a to-illuminate area with a predetermined contour shape, size, and orientation at a predetermined position relative to the illumination device 10 with coherent light. By inputting information about the to-illuminate area 96 as parameters into the computer, the shape of the uneven surface that yields a diffraction pattern on the to-illuminate area 96 that can project diffracted light can be determined by computer calculations. The diffractive optical element as a computer-generated hologram can be fabricated by forming the determined shape of the uneven surface, for example, by resin molding. The computer may be a personal computer.

[0062] The diffractive optical element 30 may include a plurality of segmented diffractive optical elements. Each segmented diffractive optical element may be, for example, a hologram element and may be configured in the same way as the diffractive optical element described above. Light diffracted by the plurality of segmented diffractive optical elements may be incident on the same region on the projection surface 95. In other words, coherent light diffracted by each segmented diffractive optical element may be incident on the entire illuminated region 96 set on the projection surface 95. With such a diffractive optical element 30, light directed toward each position in the illuminated region 96 can be emitted in a dispersed manner from the plurality of segmented diffractive optical elements included in the diffractive optical element. This suppresses localized excessively high radiation intensity at each position on the diffractive optical element 30, thereby improving laser safety.

[0063] Each section diffractive optical element may have the same diffraction characteristics as the others. In order to achieve high-precision irradiation, each section diffractive optical element may be given separately designed diffraction characteristics depending on its position within the diffractive optical element 30. In this example, each section diffractive optical element can direct the diffracted coherent light with high precision only to the entire illuminated area 96 on the projection surface 95.

[0064] Multiple sectioned diffractive optical elements may diffract coherent light to different regions on the projection plane 95. In other words, coherent light diffracted by multiple sectioned diffractive optical elements may be incident on different sectioned irradiated regions on the projection plane 95. According to this example, a single irradiated region 96 can be formed by a combination of multiple sectioned irradiated regions.

[0065] As described above, the lighting device 10 includes the diffractive optical element 30 as part of the diffractive optical element assembly 30X. The diffractive optical element assembly 30X includes the diffractive optical element 30 in a manner that suppresses the adhesion of foreign matter such as moisture and dust to the uneven surface 31.

[0066] As shown in Figure 1B, the diffractive optical element assembly 30X partitions the sealed space CR. The sealed space CR is a space closed off from the external environment. The diffractive optical element assembly 30X includes the sealed space CR as its internal space. The portion of the member partitioning the sealed space CR that faces the sealed space CR is not exposed to the external environment. The uneven surface 31 of the diffractive optical element 30 faces the sealed space CR. As shown in Figure 1B, coherent light emitted from the coherent light source 20 may pass through the sealed space CR. As shown in Figure 1B, the illustrated diffractive optical element 30 is a transmissive hologram element. In this example, coherent light emitted from the coherent light source 20 passes through the sealed space CR and the diffractive optical element 30.

[0067] For a sealed space CR, "sealed" means that no gas leakage is detected by the immersion method specified in JIS Z 2330:2012. Specifically, if no bubbles leak from the sealed space CR partitioned by the diffractive optical element assembly 30X when the diffractive optical element assembly 30X is immersed in water, the sealed space CR is judged to be sealed. In the immersion test, the container under test is immersed to a depth of 10 cm to 30 cm from the water surface. The presence or absence of bubbles is determined by visual observation over a period of 10 minutes. No pressure adjustment of the sealed space CR is performed during the immersion test. In other words, the diffractive optical element assembly 30X incorporated into the lighting device 10 is the subject of the immersion test.

[0068] As shown in Figures 1B and 3, the diffractive optical element assembly 30X may include a light-transmitting plate 40 and a holding member 50 along with the diffractive optical element 30. Figure 3 is a cross-sectional view showing the configuration of the emission end and its surroundings of an illumination device 10 that may be applied to the illumination device 10 of Figure 2. Figure 3 shows a specific example of the diffractive optical element assembly 30X. The diffractive optical element assembly 30X shown in Figure 3 further includes a second holding member 52 in addition to the holding member 50. To distinguish it from the second holding member 52, the holding member 50 is also called the first holding member 51.

[0069] As shown in Figures 1B and 3, the first retaining member 51 has a through hole 51X. The diffractive optical element 30 is joined to the first retaining member 51 at its peripheral edge 35. The through hole 51X opens in a position surrounded by the peripheral edge 35. The diffractive optical element 30 blocks the through hole 51X from one side. The translucent plate 40 is joined to the first retaining member 51 at its peripheral edge 45. The through hole 51X opens in a position surrounded by the peripheral edge 45. The translucent plate 40 blocks the through hole 51X from the other side. The translucent plate 40 is positioned facing the diffractive optical element 30. Both openings of the through hole 51X in the retaining member 50 are blocked by the diffractive optical element 30 and the translucent plate 40. In this way, the retaining member 50, the diffractive optical element 30 and the translucent plate 40 define the sealed space CR.

[0070] The diffractive optical element 30 may be joined to the holding member 50 by welding, ultrasonic bonding, or other welding methods, or by bonding or adhesive bonding using adhesives or other bonding materials. The light-transmitting plate 40 may be joined to the holding member 50 by welding, ultrasonic bonding, or other welding methods, or by bonding or adhesive bonding using adhesives or other bonding materials. By such joining, the sealed space CR can be sealed.

[0071] In the example shown in Figure 3, the diffractive optical element 30 and the light-transmitting plate 40 face each other in the first direction D1. The light-transmitting plate 40 faces the first direction D1 with its uneven surface 31. The light-transmitting plate 40 is positioned between the coherent light source 20 and the diffractive optical element 30 along the optical path of the coherent light emitted from the coherent light source 20. That is, the coherent light that passes through the light-transmitting plate 40 is incident on the diffractive optical element 30. With this arrangement, the coherent light is diffracted by the diffractive optical element 30 downstream in the optical path of the coherent light within the lighting device 10. Therefore, the lighting device 10 can be miniaturized while maintaining high utilization efficiency of coherent light. In the example shown in Figure 1B, the coherent light is diffracted by the uneven surface 31 of the diffractive optical element 30 in a direction nonparallel to the 0th-order light LX0 that passes through the diffractive optical element 30. Even when using a diffractive optical element 30 with such diffraction characteristics, the illumination device 10 can be miniaturized while maintaining high efficiency in utilizing coherent light by arranging the light-transmitting plate 40 upstream of the diffractive optical element 30. Furthermore, by arranging the light-transmitting plate 40 upstream of the diffractive optical element 30 with such diffraction characteristics, the projection of double images (ghosts) due to multiple reflections between the light-transmitting plate 40 and the diffractive optical element 30 can be suppressed. Moreover, by using a transmissive diffractive optical element 30, the illumination device 10 can be further miniaturized while maintaining high efficiency in utilizing coherent light.

[0072] The diffractive optical element assembly 30X will be described in more detail with reference to the specific example shown in Figure 3.

[0073] As shown in Figures 3 to 5, the first retaining member 51 is plate-shaped. Figure 4 is a plan view showing the retaining member 50 (first retaining member 51) together with the light-transmitting plate 40 from the second side opposite to the first side in the first direction D1. Figure 5 is a plan view showing the retaining member 50 (first retaining member 51) together with the diffractive optical element 30 from the first side in the first direction D1. The first retaining member 51 has a through hole 51X in its center. The first retaining member 51 is connected to the open end of the inner cylinder portion 62. The first retaining member 51 is positioned with respect to the third lens 28 of the shaping optical system 25 via the gap ring 63. As shown in Figures 4 and 5, the first retaining member 51 may be a plate-shaped member having a circular contour when observed from the first direction D1. The material of the first retaining member 51 may be a metal such as aluminum, or it may be a resin.

[0074] The light-transmitting plate 40 is light-transmitting. Coherent light shaped by the shaping optical system 25 can pass through the light-transmitting plate 40. Light-transmitting means that the average total light transmittance in the visible light range is 30% or more, preferably 50% or more, and more preferably 80% or more. The average total light transmittance in the visible light range is the average value of the total light transmittance (%) measured for light at 1 nm intervals from 380 nm to 780 nm. The total light transmittance (%) refers to the total light transmittance (%) measured at an incident angle of 0° using a spectrophotometer (Shimadzu Corporation "UV-3100PC", compliant with JIS K 0115).

[0075] In the illustrated example, the light-transmitting plate 40 is plate-shaped with a pair of parallel main surfaces. This light-transmitting plate 40 maintains the parallelism of the transmitted coherent light. The light-transmitting plate 40 may have, for example, a pair of non-parallel main surfaces. This light-transmitting plate 40 may adjust the optical axis of the coherent light transmitted through it. The material constituting the light-transmitting plate 40 may be various materials capable of transmitting coherent light. The material constituting the light-transmitting plate 40 may be glass or resin. The light-transmitting plate 40 may also be a transmission-type diffraction grating.

[0076] In the example shown in Figure 4, the translucent plate 40 observed from the first direction D1 has a rectangular shape. The edges of the translucent plate 40 extend in either the second direction D2 or the third direction D3. The peripheral edge 45 of the translucent plate 40 follows this edge.

[0077] In the example shown in Figure 5, the diffractive optical element 30 observed from the first direction D1 has a rectangular shape. The edges of the diffractive optical element 30 extend in either the second direction D2 or the third direction D3. As shown in Figure 5, the peripheral portion 35 of the diffractive optical element 30 follows this edge.

[0078] The first retaining member 51 has a side end face 51p with a width in the first direction D1. The side end face 51p is circumferential. The side end face 51p includes a recess 51q. As shown in Figure 4, the recess 51q extends circumferentially along the side end face 51p. As shown in Figure 3, the first retaining member 51 is in contact with the inner cylinder portion 62 from the first direction D1 at the side end face 51p including the recess 51q. In this specific example, relative movement of the first retaining member 51 and the inner cylinder portion 62 in a direction nonparallel to the first direction D1 is suppressed. As a result, the coherent light shaped by the shaping optical system 25 can be incident on the uneven surface 31 of the diffractive optical element 30 from a predetermined direction.

[0079] The lighting device 10 may include a first sealing member 71 that seals the space between the diffractive optical element assembly 30X and the casing 60. In the example shown in Figure 3, the first sealing member 71 is provided between the first retaining member 51 and the outer cylinder portion 61. This first sealing member 71 seals the space between the first retaining member 51 and the outer cylinder portion 61. The first sealing member 71 may also be an O-ring. As shown in Figure 3, a circumferential groove 51r is provided on the side end face 51p of the first retaining member 51. The first sealing member 71 is housed in the groove 51r. The first sealing member 71 can suppress the inflow of foreign matter from the external environment into the lighting device 10.

[0080] The first retaining member 51 may include a first recess 51A that accommodates the peripheral edge 45 of the light-transmitting plate 40. As shown in Figures 3 and 4, the first recess 51A is provided at a position around the through hole 51X. The first recess 51A is adjacent to the through hole 51X. According to this specific example, the light-transmitting plate 40 can be accurately positioned in a predetermined position relative to the retaining member 50. The optical path of coherent light can be prevented from being bent in an unintended direction by the light-transmitting plate 40.

[0081] As shown in Figures 3 and 4, the internal dimensions of the first recess 51A change via the stepped portion 51s. The internal dimensions of the first recess 51A increase via the stepped portion 51s on the second side in the first direction D1.

[0082] As shown in Figures 3 and 5, the first retaining member 51 may include a second recess 51B that accommodates the peripheral edge 35 of the diffractive optical element 30. The second recess 51B is located around the through hole 51X. The second recess 51B is adjacent to the through hole 51X. According to this specific example, the diffractive optical element 30 can be accurately positioned in a predetermined location relative to the retaining member 50. The diffractive optical element 30 can direct coherent light in a desired direction.

[0083] As shown in Figures 3 and 5, the internal dimensions of the second recess 51B change via the stepped portion 51t. The internal dimensions of the second recess 51B increase via the stepped portion 51t in the portion away from the shaping optical system 25 in the first direction D1.

[0084] The lighting device 10 may further include a second retaining member 52 fixed to the first retaining member 51. As shown in Figure 6, the second retaining member 52 may have a circular contour when viewed from a first direction D1. As shown in Figure 3, the second retaining member 52 may be plate-shaped. In the illustrated example, the second retaining member 52 has the same dimensions as the first retaining member 51.

[0085] The second retaining member 52 may be fixed to the first retaining member 51 by a fastener 55. The fastener 55 may be a screw, as shown in Figure 3. In the examples shown in Figures 4 and 5, the first retaining member 51 has a plurality of fixing holes 51Y for fixing the fastener 55. Also, in the example shown in Figure 6, the second retaining member 52 has a plurality of fastener through holes 52Y through which the fastener 55 can pass. In the illustrated examples, the first retaining member 51 and the second retaining member 52 are fixed to each other by the fastener 55 passing through the fastener through holes 52Y and then being fixed to the fixing holes 51Y. Figure 6 is a plan view showing a diffractive optical element assembly 30X including the second retaining member 52.

[0086] In the example shown in Figure 6, the second retaining member 52 includes a through hole 52X that penetrates in the first direction D1. In the illustrated example, when observed from the first direction D1, the through hole 52X of the second retaining member 52 has the same dimensions as the through hole 51X of the first retaining member 51. When the first retaining member 51 and the second retaining member 52 are fixed to each other, the opening by the through hole 51X, shown by dashed lines in Figures 4 and 5, coincides with the opening by the through hole 52X shown in Figure 6 in the first direction D1. Around the through holes 51X and 52X, the peripheral portion 35 of the diffractive optical element 30 is held between the first retaining member 51 and the second retaining member 52.

[0087] As shown in Figures 3 and 6, the second retaining member 52 may have a recess 52A at a position around the through hole 52X. In the illustrated example, the recess 52A has a rectangular contour with its longitudinal direction in the second direction D2 when viewed from the second side in the first direction D1. When viewed from the first direction D1, the contour of the recess 52A of the second retaining member 52 has the same dimensions as the contour of the second recess 51B of the first retaining member 51. When the first retaining member 51 and the second retaining member 52 are fixed to each other, the contour of the second recess 51B of the first retaining member 51 shown in Figure 5 overlaps with the contour of the recess 52A of the second retaining member 52 shown in Figure 6 in the first direction D1.

[0088] As shown in Figures 2 and 3, the lighting device 10 may include a second sealing member 72 located between the second recess 51B of the first retaining member 51 and the recess 52A of the second retaining member 52. The second sealing member 72 contacts the peripheral edge 35 of the diffractive optical element 30 from the first side in the first direction D1. The second sealing member 72 seals the space between the peripheral edge 36 of the diffractive optical element 30 and the second retaining member 52. In the illustrated example, the second sealing member 72 deforms according to the shape of the gap partitioned by the peripheral edge 35 of the diffractive optical element 30, the second recess 51B of the first retaining member 51, and the recess 52A of the second retaining member 52. As a result, the peripheral edge 35 of the diffractive optical element 30 is held by the second retaining member 52 via the second sealing member 72 from the first side in the first direction D1. The peripheral edge 35 of the diffractive optical element 30 is held by the first holding member 51 from the other side in the first direction D1. The second sealing member 72 can suppress the inflow of foreign matter from the external environment into the lighting device 10.

[0089] In the examples shown in Figures 3 and 6, the outer cylindrical portion 61 of the casing 60 is in contact with the side of the second retaining member 52 opposite to the side in contact with the first retaining member 51. As shown by the dashed line in Figure 6, the second retaining member 52 is in contact with the outer cylindrical portion 61 at its peripheral edge. As shown in Figure 3, the fastener passage hole 52Y of the second retaining member 52 is blocked from the first direction D1 by the outer cylindrical portion 61.

[0090] As shown in Figures 1B and 3, the lighting device 10 may include a cover 80 positioned facing the diffractive optical element 30 in a first direction D1. The cover 80 blocks the opening of the outer cylinder portion 61 from the first direction D1. The cover 80 is light-transmitting. Coherent light diffracted by the uneven surface 31 of the diffractive optical element 30 can pass through the cover 80. According to this specific example, the inflow of foreign matter into the lighting device 10 from the opening of the outer cylinder portion 61 can be suppressed.

[0091] Next, the operation of the illustrated lighting device will be explained.

[0092] To project a projection pattern 90 onto the projection surface 95, coherent light is emitted from the coherent light source 20. The coherent light emitted from the coherent light source 20 is shaped by the shaping optical system 25. In the illumination device 10 shown in Figure 2, the coherent light emitted from the coherent light source 20 is shaped into a divergent beam by the first lens 26. The divergent beam is shaped into a parallel beam by the second lens 27 and the third lens 28. In this way, the coherent light emitted from the coherent light source 20 is shaped by the shaping optical system 25.

[0093] Coherent light shaped by the shaping optical system 25 is directed toward the diffractive optical element assembly 30X. This coherent light passes through the light-transmitting plate 40 of the diffractive optical element assembly 30X. The coherent light that has passed through the light-transmitting plate 40 passes through the through-hole 51X of the holding member 50 and is directed toward the diffractive optical element 30. The diffractive optical element 30 changes the direction of propagation of the coherent light shaped by the shaping optical system 25. The diffractive optical element 30 includes an uneven surface 31 that diffracts the coherent light shaped by the shaping optical system 25. The coherent light diffracted at the uneven surface 31 is directed toward the illuminated area 96 on the projection surface 95. This allows a projection pattern 90 corresponding to the diffraction characteristics of the uneven surface 31 to be projected onto the projection surface 95. In other words, the projection surface 95 can be illuminated by irradiating the illuminated area 96 corresponding to the diffraction characteristics of the uneven surface 31 with coherent light.

[0094] Incidentally, lighting devices are sometimes used outdoors. When lighting devices are used outdoors, foreign matter such as dust and water droplets may enter the inside of the lighting device. Also, the temperature inside the lighting device may change rapidly in accordance with the temperature of the external environment. In this case, condensation may occur inside the lighting device. Foreign matter may adhere to the uneven surface of the diffractive optical element.

[0095] When foreign matter such as dust or water droplets adheres to an uneven surface, coherent light attempting to enter the uneven surface is refracted or diffracted in an unintended direction due to the influence of these foreign matter. In this way, the optical path of coherent light can be directed in an unintended direction due to the optical effect exerted by foreign matter adhering to the uneven surface 31. As a result, the desired projection pattern cannot be projected onto the projection surface.

[0096] As shown in Figures 2 and 3, the uneven surface 31 faces the sealed space CR. The sealed space CR is a sealed space and is not connected to the external environment. This suppresses the inflow of foreign matter into the sealed space CR and suppresses the adhesion of foreign matter to the uneven surface 31. As a result, the uneven surface 31 can exhibit the expected diffraction function and diffract coherent light in the desired direction. That is, the desired illuminated area 96 on the projection surface 95 can be illuminated accurately by coherent light, and consequently, the desired projection pattern 90 can be projected onto the projection surface 95.

[0097] The illustrated lighting device 10 and diffractive optical element assembly 30X include a diffractive optical element 30 with an uneven surface 31, a light-transmitting plate 40 positioned facing the diffractive optical element 30, and a first holding member 51 that holds the diffractive optical element 30 and the light-transmitting plate 40. The first holding member 51 has a through hole 51X. The light-transmitting plate 40 is joined to the first holding member 51 so as to close the through hole 51X from one side. The diffractive optical element 30 is joined to the first holding member 51 so as to close the through hole 51X from the other side. The uneven surface 31 faces the light-transmitting plate 40. According to this specific example, a sealed space CR can be formed with a simple configuration. The number of components required to partition the sealed space CR can be reduced. Accordingly, the manufacturing cost of the lighting device 10 including the sealed space CR can be reduced.

[0098] In the illustrated example, the first retaining member 51 is plate-shaped. By using the through-hole 51X provided in the plate-shaped first retaining member 51 to form a sealed space CR, the length of the sealed space CR along the direction in which the diffractive optical element 30 and the light-transmitting plate 40 face each other, i.e., the first direction D1, can be shortened. Furthermore, the plate-shaped first retaining member 51 can be stably held by a casing 60 or the like. As a result, the dimensions of the sealed space CR and the lighting device 10 in which the sealed space CR is formed can be reduced.

[0099] In the illustrated example, the lighting device 10 and the diffractive optical element assembly 30X include a second holding member 52 fixed to a first holding member 51. The peripheral edge 35 of the diffractive optical element 30 is held by the first holding member 51 and the second holding member 52. In this example, the peripheral edge 36 of the diffractive optical element 30 is covered by the second holding member 52, thereby suppressing the inflow of foreign matter from the peripheral edge 36 of the diffractive optical element 30 onto the uneven surface 31.

[0100] In the embodiment described above, the lighting device 10 includes a coherent light source 20, a shaping optical system 25 for shaping the coherent light emitted from the coherent light source 20, and a diffractive optical element 30 including an uneven surface 31 for diffracting the coherent light shaped by the shaping optical system 25. The uneven surface 31 faces a sealed space CR. In this specific example, the adhesion of foreign matter to the uneven surface 31 can be suppressed. As a result, the coherent light can be diffracted in a desired direction by the uneven surface 31. Therefore, a desired projection pattern 90 can be projected onto the projection surface 95 with high accuracy.

[0101] In the embodiment described above, the lighting device 10 includes a coherent light source 20 that emits coherent light, a shaping optical system 25 that shapes the coherent light emitted from the coherent light source 20, a diffractive optical element 30 including an uneven surface 31 that diffracts the coherent light shaped by the shaping optical system 25, a light-transmitting plate 40 positioned facing the diffractive optical element 30, and a holding member 50 that holds the diffractive optical element 30 and the light-transmitting plate 40. The holding member 50 (first holding member 51) has a through hole 51X. The light-transmitting plate 40 is joined to the holding member 50 so as to close the through hole 51X from one side. The diffractive optical element 30 is joined to the holding member 50 so as to close the through hole 51X from the other side. The uneven surface 31 faces the light-transmitting plate 40. According to this specific example, the adhesion of foreign matter to the uneven surface 31 can be suppressed. As a result, the uneven surface 31 allows coherent light to be diffracted in the desired direction. Therefore, the desired projection pattern 90 can be accurately projected onto the projection surface 95.

[0102] While one embodiment has been described with reference to specific examples, the above-mentioned example does not limit the embodiment to one specific example. The above-described example of one embodiment can be implemented in various other examples, and various omissions, substitutions, modifications, additions, etc., can be made without departing from the gist of the example.

[0103] An example of modification will be described below with reference to the drawings. In the following explanation and the drawings used therein, parts that can be configured in the same way as in the specific example described above will be given the same reference numerals as those used for the corresponding parts in the specific example described above, and redundant explanations will be omitted.

[0104] In the specific example described above, the holding member 50 (first holding member 51) was plate-shaped. However, it is not limited to this, and as shown in Figure 7, the holding member 50 may be cylindrical. In this example, the diffractive optical element 30 may be joined to the holding member 50 so as to close the through hole 51X from one side. The light-transmitting plate 40 may be joined to the holding member 50 so as to close the through hole 51X from the other side.

[0105] In the specific example described above, the diffractive optical element assembly 30X of the lighting device 10 included a holding member 50 for holding the diffractive optical element 30 and the light-transmitting plate 40. However, as shown in Figure 8, the holding member 50 may be omitted from the lighting device 10 and the diffractive optical element assembly 30X. As shown in Figure 8, the diffractive optical element 30 and the light-transmitting plate 40 may be held by a casing 60. The casing 60 has a through hole 60X. The light-transmitting plate 40 is joined to the casing 60 so as to close the through hole 60X of the casing 60 from one side. The diffractive optical element 30 is joined to the casing 60 so as to close the through hole 60X of the casing 60 from the other side. According to this specific example, the diffractive optical element 30 and the light-transmitting plate 40 can partition a sealed space CR that can be stably maintained in a sealed state with a simple configuration.

[0106] In the specific example described above, the diffractive optical element assembly 30X of the lighting device 10 included a second holding member 52 fixed to the holding member 50. However, as shown in Figures 7 and 8, the second holding member 52 may be omitted from the lighting device 10 and the diffractive optical element assembly 30X.

[0107] In the specific example described above, the sealed space CR was partitioned by the diffractive optical element 30, the light-transmitting plate 40, and the holding member 50. However, as shown in Figures 9 to 11, the sealed space CR may also be partitioned between the diffractive optical element 30 and the light-transmitting plate 40 which are joined together. The light-transmitting plate 40 may be joined to the diffractive optical element 30 in a circumferential portion (region) surrounding the uneven surface 31. According to this specific example, by allowing light to pass through the light-transmitting plate 40, the sealed space CR can be easily partitioned while more reliably allowing coherent light to enter the uneven surface 31.

[0108] In the example shown in Figure 9, the diffractive optical element 30 includes a plate-like portion 30a containing an uneven surface 31, and a projection 30b protruding from the plate-like portion 30a toward the light-transmitting plate 40. In this specific example, the projection 30b of the diffractive optical element 30 partitions the sealed space CR from a direction nonparallel to the direction in which the uneven surface 31 and the light-transmitting plate 40 face each other. According to this specific example, the diffractive optical element 30 and the light-transmitting plate 40 can partition a sealed space CR that can be stably maintained in a sealed state with a simple configuration.

[0109] In the example shown in Figure 10, the light-transmitting plate 40 includes a plate-shaped portion 40a facing the uneven surface 31 of the diffractive optical element 30, and a protruding portion 40b projecting from the plate-shaped portion 40a toward the diffractive optical element 30. In this specific example, the protruding portion 40b of the light-transmitting plate 40 demarcates the sealed space CR from a direction nonparallel to the direction in which the uneven surface and the light-transmitting plate 40 face each other. Even in this specific example, the diffractive optical element 30 and the light-transmitting plate 40 can demarcate a sealed space CR that can be stably maintained in a sealed state with a simple configuration.

[0110] In the example shown in Figure 11, the diffractive optical element 30 includes a plate-shaped portion 30a with an uneven surface 31, and a projection 30b that protrudes from the plate-shaped portion 30a toward the light-transmitting plate 40. The light-transmitting plate 40 also includes a plate-shaped portion 40a facing the uneven surface 31 of the diffractive optical element 30, and a projection 40b that protrudes from the plate-shaped portion 40a toward the diffractive optical element 30. In this specific example as well, the diffractive optical element 30 and the light-transmitting plate 40 can partition a sealed space CR that can be stably maintained in a sealed state with a simple configuration.

[0111] As an example of a manufacturing method for a lighting device 10 that includes a sealed space CR partitioned between a diffractive optical element 30 and a light-transmitting plate 40, the manufacturing method for a lighting device 10 including the sealed space CR shown in Figure 9 will be described with reference to Figures 12 to 14.

[0112] First, a first plate 101 containing multiple diffractive optical elements 30 on one side, and a second plate 102 containing a light-transmitting plate 40 are prepared. As shown by the dashed line in the example in Figure 11, the first plate 101 contains three diffractive optical elements 30 aligned in the third direction D3. In the illustrated example, adjacent diffractive optical elements 30 in the third direction D3 are connected without being cut. Each of the three diffractive optical elements 30 contains an uneven surface 31 facing the second plate 102 in the first direction D1. The first plate 101 containing multiple diffractive optical elements 30 can be manufactured by various molding methods. For example, the first plate 101 can be manufactured by injection molding or nanoimprint molding.

[0113] In the example shown in Figure 12, the first plate 101 includes a plate-like portion 101a containing the uneven surface 31 of the diffractive optical element 30, and a projection 101b projecting from the plate-like portion 101a toward the second plate 102. In the illustrated example, the uneven surface 31 of the diffractive optical element 30 is located between two adjacent projections 101b in the third direction D3.

[0114] Next, as shown in Figures 12 and 13, a second plate 102 is joined to one surface of a first plate 101 containing a plurality of diffractive optical elements 30. The first plate 101 and the second plate 102 may be joined to each other by adhesive or welding. As shown in Figure 13, the first plate 101 is joined to the second plate 102 at the protruding portion 101b. As a result, the region between the protruding portions 101b of adjacent first plates 101 in the third direction D3 is closed by the second plate 102. That is, in the joining process of the first plate 101 and the second plate 102, a sealed space CR is defined between the first plate 101 and the second plate 102. Also, in the example shown in Figure 13, the second plate 102 is joined circumferentially to the first plate 101 around the uneven surface 31.

[0115] Next, as shown in Figure 14, the first plate 101 joined to the second plate 102 is cut into sections for each diffractive optical element 30. In the illustrated example, the first plate 101 joined to the second plate 102 is cut by planes extending in the first direction D1 and the second direction D2. In this way, a diffractive optical element assembly 30X is manufactured in which a sealed space CR is partitioned between the diffractive optical elements 30 and the light-transmitting plate 40. Then, by incorporating this diffractive optical element assembly 30X, the lighting device 10 is manufactured.

[0116] In one specific example of the manufacturing method for the lighting device 10 shown in Figures 12 to 14, the sealed space CR of the diffractive optical element assembly 30X is partitioned between the first plate 101 and the second plate 102 during the joining process in which the second plate 102 is joined to one side of the first plate 101. According to this specific example, the sealed space CR is partitioned by the first plate 101 and the second plate 102 before the cutting process in which the first plate 101, joined to the second plate 102, is cut for each diffractive optical element 30. This effectively prevents foreign matter such as dust and water droplets that may be generated during the cutting process from flowing into the sealed space CR. Therefore, according to this specific example, the inflow of foreign matter onto the uneven surface 31 of the diffractive optical element 30 can be suppressed.

[0117] In one specific example of the manufacturing method of the lighting device 10 shown in Figures 12 to 14, when the second plate 102 is joined to the first plate 101, the second plate 102 is joined to the first plate 101 in a circumferential manner around the uneven surface 31 of the diffractive optical element 30. In this specific example, the uneven surface 31 of the diffractive optical element 30 is covered by the second plate 102 before the cutting process in which the first plate 101, joined to the second plate 102, is cut into individual diffractive optical elements 30. This effectively prevents foreign matter such as dust that may be generated during the cutting process from adhering to the uneven surface 31 of the diffractive optical element 30.

[0118] Unlike the examples shown in Figures 12 to 14, the second plate 102 may include a projection that extends toward the first plate 101. Also, unlike the examples shown in Figures 11 to 13, the first plate 101 may include a projection that extends toward the second plate 102, and the second plate 102 may also include a projection that extends toward the first plate 101.

[0119] In the specific examples described above, the sealed space CR may be filled with a dry gas. The gas filling the sealed space CR may be air or nitrogen. Note that "dry" means that the dew point temperature of the gas at a pressure of 1 atm is -30°C or lower. The dew point temperature is measured using a capacitive dew point meter (ND-TA, manufactured by Nagano Electric Industries Co., Ltd., compliant with JIS Z 8806:2001). Alternatively, in the specific examples described above, the sealed space CR may be under reduced pressure. Reduced pressure means that the pressure is less than 1 atm. The sealed space CR may also be a vacuum. According to these specific examples, the amount of water vapor contained in the sealed space CR is reduced, and the occurrence of condensation inside the sealed space CR can be suppressed. This suppresses the adhesion of water droplets to the uneven surface 31.

[0120] In the specific example described above, the distance between the uneven surface 31 of the diffractive optical element 30 and the light-transmitting plate 40 may be 0.5 mm or more and 3.5 mm or less, 1.0 mm or more and 3.0 mm or less, or 1.5 mm or more and 2.5 mm or less. By setting an upper limit on the distance between the uneven surface 31 and the light-transmitting plate 40, the increase in the volume of the sealed space CR partitioned between the diffractive optical element 30 and the light-transmitting plate 40 can be suppressed. This reduces the amount of water vapor contained in the sealed space CR and suppresses the adhesion of water droplets to the uneven surface 31 due to condensation, etc. Furthermore, by setting a lower limit on the distance between the uneven surface 31 and the light-transmitting plate 40, the sealed space CR can be easily partitioned within the lighting device 10.

[0121] In the specific example described above, the diffractive optical element 30 may include a hydrophilic layer that constitutes the uneven surface 31. The hydrophilic layer is defined as a layer on which the contact angle of a 4 μl water droplet dropped onto the surface of the diffractive optical element 30, which is composed of the hydrophilic layer, is 30° or less. The contact angle is measured using a contact angle meter (DropMaster DM500, manufactured by Kyowa Interface Science Co., Ltd., compliant with JIS R 3257:1999). The hydrophilic layer may include various materials containing hydrophilic groups. According to this specific example, even if a water droplet adheres to the uneven surface 31, it is possible to effectively suppress the unintentional large bending of the optical path of coherent light caused by this water droplet.

[0122] In the specific example described above, a desiccant may be provided in the sealed space CR. Calcium oxide, strontium oxide, silica gel, superabsorbent polymer, or moisture getter (for example, "OleDry" manufactured by Futaba Corporation) may be used as the desiccant. According to this specific example, the humidity inside the sealed space CR can be reduced by the desiccant. This effectively suppresses condensation on the uneven surface 31.

[0123] In the specific example described above, the light-transmitting plate 40 may include an anti-reflective layer that constitutes its surface. The anti-reflective layer of the light-transmitting plate 40 refers to a layer that has the function of suppressing the reflection of coherent light from the coherent light source 20. The reflectance is measured by a spectrophotometer (Shimadzu Corporation "UV-3100PC", compliant with JIS K 0115). The reflectance of the light-transmitting plate 40 with the anti-reflective layer may be 1.0% or less for 0° incident light. The light-transmitting plate 40 may include an anti-reflective layer on the surface facing the shaping optical system 25. The light-transmitting plate 40 may also include an anti-reflective layer on the surface facing the uneven surface 31 of the diffractive optical element 30. The anti-reflective layer of the light-transmitting plate 40 may be a single layer. The anti-reflective layer of the light-transmitting plate 40 may include hollow silica and fluorine additives as particles to adjust the refractive index. In this specific example, reflection of coherent light shaped by the shaping optical system 25 on the light-transmitting plate 40 is suppressed, and the illuminated area 96 can be clearly illuminated by the light emitted from the coherent light source 20. Furthermore, in this specific example, the occurrence of double images (ghosts) caused by reflection of coherent light on the surface of the light-transmitting plate 40 can be suppressed.

[0124] In the specific example described above, the diffractive optical element 30 may include an anti-reflective layer that constitutes the surface opposite to the uneven surface 31. The anti-reflective layer of the diffractive optical element 30 means a layer that has the function of suppressing the reflection of coherent light from the coherent light source 20. The reflectance is measured by a spectrophotometer (Shimadzu Corporation "UV-3100PC", compliant with JIS K 0115). The reflectance of the diffractive optical element 30 with the anti-reflective layer may be 1.0% or less for 0° incident light. The anti-reflective layer of the diffractive optical element 30 may be a single layer. In the diffractive optical element 30, the single-layer anti-reflective layer may be a thin film containing magnesium fluoride to adjust the refractive index. Two or more anti-reflective layers may be provided on the diffractive optical element 30. When two or more anti-reflective layers are provided on the diffractive optical element 30, the refractive index and thickness of each anti-reflective layer may be different. According to this specific example, by suppressing the reflection of ambient light in the diffractive optical element 30, the projection pattern 90 can be projected with high precision and stability.

[0125] In addition, while several modifications of the above-described embodiments have been explained, it is naturally possible to combine and apply multiple modifications as appropriate. [Explanation of Symbols]

[0126] 10: Illumination device, 20: Coherent light source, 25: Shaping optical system, 26: First lens, 27: Second lens, 28: Third lens, 30X: Diffractive optical element assembly, 30: Diffractive optical element, 31: Uneven surface, 40: Light-transmitting plate, 50: Holding member, 51: First holding member, 52: Second holding member, 55: Fixing device, 60: Casing, 61: Outer cylinder, 62: Inner cylinder, 63: Gap ring, 64: Battery, 65: Circuit, 66: Switch, 71: First sealing member, 72: Second sealing member, 80: Cover, 90: Projection pattern, 95: Projection surface, 96: Illuminated area

Claims

1. A coherent light source, a shaping optical system for shaping the coherent light emitted from the coherent light source, a diffractive optical element including a concavo-convex surface for diffracting the coherent light shaped by the shaping optical system, and the concavo-convex surface faces a sealed space, a lighting device.

2. A light-transmitting plate disposed facing the diffractive optical element, and a holding member for holding the diffractive optical element and the light-transmitting plate, and the sealed space is partitioned by the holding member, the diffractive optical element, and the light-transmitting plate, the lighting device according to claim 1.

3. The holding member has a through hole, the diffractive optical element is joined to the holding member so as to close the through hole from one side, the light-transmitting plate is joined to the holding member so as to close the through hole from the other side, the lighting device according to claim 2.

4. A coherent light source that emits coherent light, a shaping optical system for shaping the coherent light emitted from the coherent light source, a diffractive optical element including a concavo-convex surface for diffracting the coherent light shaped by the shaping optical system, a light-transmitting plate disposed facing the diffractive optical element, and a holding member for holding the diffractive optical element and the light-transmitting plate, and the holding member has a through hole, the light-transmitting plate is joined to the holding member so as to close the through hole from one side, the diffractive optical element is joined to the holding member so as to close the through hole from the other side, the concavo-convex surface faces the light-transmitting plate, a lighting device.

5. The holding member is plate-shaped, the lighting device according to claim 4.

6. A casing for housing the holding member, and a first sealing member for sealing the peripheral portion of the holding member and the casing, the lighting device according to any one of claims 2 to 5.

7. The holding member includes a recess for housing the peripheral portion of the light-transmitting plate at a position around the through hole, the lighting device according to any one of claims 3 to 5.

8. The holding member includes a second recess for housing the peripheral portion of the diffractive optical element at a position around the through hole, the lighting device according to any one of claims 3 to 5.

9. Further comprising a second holding member fixed to the holding member, the peripheral portion of the diffractive optical element is held by the holding member and the second holding member, the lighting device according to any one of claims 2 to 5.

10. The lighting device according to claim 9, further comprising a second sealing member that seals between the peripheral portion of the diffractive optical element and the second holding member.

11. The lighting device further comprises a light-transmitting plate disposed facing the diffractive optical element, The light-transmitting plate is joined to the diffractive optical element and defines the sealed space therebetween, the lighting device according to claim 1.

12. The diffractive optical element includes a plate-shaped portion including the uneven surface, and a protruding portion protruding from the plate-shaped portion toward the light-transmitting plate, The protruding portion is joined to the light-transmitting plate, the lighting device according to claim 11.

13. The light-transmitting plate includes a plate-shaped portion facing the uneven surface, and a protruding portion protruding from the plate-shaped portion toward the diffractive optical element, The protruding portion is joined to the light-transmitting plate, the lighting device according to claim 11.

14. A coherent light source that emits coherent light, A shaping optical system that shapes the coherent light emitted from the coherent light source, A diffractive optical element including an uneven surface that diffracts the coherent light shaped by the shaping optical system, A light-transmitting plate disposed facing the uneven surface of the diffractive optical element, and The light-transmitting plate is joined to the diffractive optical element in a circumferential portion surrounding the uneven surface, a lighting device.

15. The lighting device further comprises a cover through which the coherent light diffracted by the uneven surface of the diffractive optical element passes, The cover is disposed facing the diffractive optical element, the lighting device according to any one of claims 1 to 5, 11 to 14.

16. The distance between the uneven surface of the diffractive optical element and the light-transmitting plate is 0.5 mm or more and 3.5 mm or less, the lighting device according to any one of claims 2 to 5, 11 to 14.

17. The light-transmitting plate includes an antireflection layer that constitutes a surface, the lighting device according to any one of claims 2 to 5, 11 to 14.

18. The light-transmitting plate is a transmissive diffraction grating, the lighting device according to any one of claims 2 to 5, 11 to 14.

19. The sealed space is filled with a dry gas, the lighting device according to any one of claims 1 to 3, 11 to 13.

20. The sealed space is depressurized, the lighting device according to any one of claims 1 to 3, 11 to 13.

21. The coherent light diffracted by the uneven surface of the diffractive optical element passes through the diffractive optical element. The lighting device according to any one of claims 1 to 5, 11 to 14.

22. The diffractive optical element includes an antireflection layer that constitutes a surface on the side opposite to the uneven surface. The lighting device according to any one of claims 1 to 5, 11 to 14.

23. The diffractive optical element includes a hydrophilic layer that constitutes the uneven surface. The lighting device according to any one of claims 1 to 5, 11 to 14.

24. A moisture absorbent is provided in the sealed space. The lighting device according to any one of claims 1 to 3, 11 to 13.

25. By the uneven surface of the diffractive optical element, the coherent light is diffracted in a direction non-parallel to the zero-order light that passes through the diffractive optical element. The lighting device according to any one of claims 1 to 5, 11 to 14.

26. A method for manufacturing a lighting device according to any one of claims 11 to 14, A preparation step of preparing a first plate including a plurality of the uneven surfaces on one surface and a second plate having translucency, A bonding step of bonding the second plate to the one surface of the first plate, A cutting step of cutting the first plate and the second plate bonded to the first plate for each of the uneven surfaces. A method for manufacturing a lighting device.

27. In the step of bonding the second plate to the first plate, the second plate is circumferentially bonded to the first plate around each of the uneven surfaces. The method for manufacturing a lighting device according to claim 26.

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