Lighting device

Abstract

The present invention provides a lighting device that can prevent the dot patterns of each color projected onto the projection surface from appearing dark. [Solution] The lighting device 10 includes a diffractive optical element 50 that receives a laser beam Ray2 of visible wavelength and converts the laser beam into a group of rays Ray3 corresponding to a group of dot patterns projected onto a projection surface S. The longer the wavelength of the laser beam incident on the diffractive optical element, the larger the dot spacing of the dot pattern projected onto the projection surface, and the larger the spot size of the dot pattern projected onto the projection surface.

Description

[Technical Field]

[0001] This disclosure relates to a lighting device. [Background technology]

[0002] There are known lighting devices (e.g., projectors) that use multiple light sources emitting light of different wavelengths, such as RGB light sources, to combine the light emitted from each light source using a dichroic mirror, and then diffuse it with a homogenizer to form an image using an optical modulation element such as LCOS (Liquid Crystal On Silicon) (see, for example, Non-Patent Document 1).

[0003] In response to this, the present inventors investigated the use of a diffractive optical element that receives laser light in the visible wavelength range and converts the laser light into a group of rays corresponding to a group of dot patterns projected onto a projection surface, thereby forming an image composed of multiple dot patterns. [Prior art documents] [Patent Documents]

[0004] [Non-Patent Document 1] Light Edge, a technical information magazine on optical technology, No. 37, "Special Feature: Ushio's New Initiatives, Part 2" [Retrieved February 19, 2024], Internet<URL:https: / / www.ushio.co.jp / jp / technology / lightedge / 201206 / 100438.html> [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, the inventors have found that when forming an image composed of multiple dot patterns using the above-mentioned diffractive optical element, the longer the wavelength of the laser light incident on the diffractive optical element, the smaller the total dot area per unit area of ​​the dot pattern projected onto the projection surface (or the luminous flux per unit area of ​​the dot pattern projected onto the projection surface, i.e., the illuminance), resulting in the dot pattern projected onto the projection surface appearing darker.

[0006] This disclosure is made to solve these problems and aims to provide a lighting device that can prevent the dot patterns of each color projected onto the projection surface from appearing dark. [Means for solving the problem]

[0007] The illumination device according to this disclosure includes a diffractive optical element that receives laser light of a visible wavelength and converts the laser light into a group of rays corresponding to a group of dot patterns projected onto a projection surface, wherein the longer the wavelength of the laser light incident on the diffractive optical element, the larger the dot spacing of the dot pattern projected onto the projection surface and the larger the spot size of the dot pattern projected onto the projection surface.

[0008] This configuration makes it possible to create a lighting device that prevents the dot patterns of each color projected onto the projection surface from appearing dark.

[0009] In the above-described lighting device, the longer the wavelength of the laser light incident on the diffractive optical element, the larger the beam diameter of the laser light incident on the diffractive optical element may be.

[0010] Furthermore, in the above-mentioned lighting device, the total area of ​​dots per unit area of ​​each colored dot pattern projected onto the projection surface may be the same for all of them.

[0011] Furthermore, in the above-described lighting device, the luminous flux per unit area of ​​each colored dot pattern projected onto the projection surface may be the same for all of them.

[0012] Further, in the above lighting device, it may further include a plurality of laser light sources that emit laser lights having wavelengths in different visible ranges, and a plurality of lenses provided corresponding to the plurality of laser light sources, and the plurality of lenses may be collimating lenses that convert the laser light emitted by the laser light source corresponding to each lens into parallel light.

[0013] Another lighting device according to the present disclosure includes a diffractive optical element that receives laser light having a wavelength in the visible range and converts the laser light into a light beam group corresponding to a dot pattern group projected onto a projection surface, and the luminous flux per unit area of each color dot pattern projected onto the projection surface is the same as each other.

[0014] In the above lighting device, it may further include a plurality of laser light sources that emit laser lights having wavelengths in different visible ranges, and a control device that controls the brightness of each of the plurality of laser light sources, and the control device may control the brightness of the plurality of laser light sources so that the luminous flux per unit area of each color dot pattern projected onto the projection surface is the same as each other.

[0015] Another lighting device according to the present disclosure includes a diffractive optical element that receives laser light having a wavelength in the visible range and converts the laser light into a light beam group corresponding to a dot pattern group projected onto a projection surface, and the brightness per unit area of each color dot pattern projected onto the projection surface is the same as each other.

[0016] In the above lighting device, it may further include an optical element disposed between the diffractive optical element and the projection surface, and the optical element may form an image on the projection surface by blocking at least a part of the light beam group converted by the diffractive optical element. [Effect of the Invention]

[0017] According to the present disclosure, it is possible to provide a lighting device that can prevent each color dot pattern projected onto a projection surface from appearing dark. [Brief Description of the Drawings]

[0018] [Figure 1] It is a schematic configuration diagram of the lighting device 10. [Figure 2] (a) An enlarged arrow view of the diffractive optical element 50 in FIG. 1 viewed from the direction of arrow AR1, (b) A cross-sectional view taken along the line A-A in FIG. 2(a). [Figure 3] It is an example of a dot pattern DP group projected onto the projection surface S. [Figure 4] (a) An example of the size D1 of the red dot pattern DPR and the dot interval LR, (b) An example of the size D2 of the green dot pattern DPG and the dot interval LG. [Figure 5] It is a diagram for explaining that the dot interval of the dot pattern DP projected onto the projection surface S becomes larger. [Figure 6] It is an example in which the spot (light emission point) size D1 of the red dot pattern DPR projected onto the projection surface S is increased as compared with FIG. 4(a). [Figure 7] It is a schematic configuration diagram of the lighting device 10A which is a modification. [Figure 8] It is a schematic configuration diagram of the lighting device 10B which is a second modification. [Figure 9] It is an example of the optical element 60 (physical mask). [Figure 10] It is an example of an image composed of the dot pattern DP (s) formed on the projection surface S.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, the lighting device 10 (image forming device) which is an embodiment of the present disclosure will be described while referring to the accompanying drawings. The same reference numerals are assigned to corresponding components in each figure, and redundant descriptions are omitted.

[0020] FIG. 1 is a schematic configuration diagram of the lighting device 10.

[0021] As shown in Figure 1, the illumination device 10 comprises a plurality of laser light sources 20 that emit laser light Ray1 of different visible wavelengths, a plurality of lenses 30, a dichroic prism 40, a diffractive optical element 50 (DOE), and a control device 70 that controls the brightness of each of the plurality of laser light sources 20.

[0022] The multiple laser light sources 20 include, for example, a laser light source 20R that emits red laser light, a laser light source 20G that emits green laser light, and a laser light source 20B that emits blue laser light. The laser light Ray 1 emitted from each of the multiple laser light sources 20 passes through multiple lenses 30 (collimating lenses) provided corresponding to the multiple laser light sources 20, is converted into parallel light, and then enters the dichroic prism 40.

[0023] Laser beams Ray1 of each color (each wavelength in the visible range) incident on the dichroic prism 40 are directed along the same optical axis AX due to the action of the dichroic prism 40. 40 The laser beam Ray2 is emitted from the dichroic prism 40 along the specified line. The laser beam Ray2 (parallel light) emitted from the dichroic prism 40 is incident on the diffractive optical element 50. The beam diameter of the laser beam Ray2 incident on the diffractive optical element 50 is, for example, about 3 mm.

[0024] Figure 2(a) is an enlarged view of the diffractive optical element 50 in Figure 1, seen from the direction of arrow AR1, and Figure 2(b) is a cross-sectional view AA of Figure 2(a). Note that the cross-sectional view BB of Figure 2(a) is the same as the cross-sectional view AA.

[0025] The diffractive optical element 50 includes a microlens array and receives laser light Ray1 emitted from each laser light source 20, i.e., laser light Ray2 of each color (each wavelength in the visible range) emitted from the dichroic prism 40 after passing through the lens 30, and converts or splits (diffracts) the laser light Ray2 into a group of rays Ray3 corresponding to a group of dot patterns projected onto the projection surface S. In other words, the diffractive optical element 50 diffracts and divides the laser light Ray2 incident on it in the up, down, left, and right directions. The group of rays Ray3 becomes a bundle of light beams with multiple directions. As the diffractive optical element 50, for example, the product name "ardisia" from Scivax may be used. Alternatively, as the diffractive optical element 50, for example, the one described in Japanese Patent Publication No. 7061823 may be used. However, the diffractive optical element 50 may have any configuration as long as it receives laser light and converts (diffracts) the laser light into a group of rays corresponding to a group of dot patterns projected onto the projection surface S. For example, it may be a general diffraction grating with a groove structure.

[0026] The microlens array of the diffractive optical element 50 includes a plurality of lenses 51 arranged two-dimensionally in the XY direction, as shown in Figures 2(a) and 2(b). Figures 2(a) and 2(b) show an example in which the lens 51 is provided on the incident side of the diffractive optical element 50 (the incident side of the laser light Ray 2), but it is not limited to this. The lens 51 only needs to be provided on at least one of the incident side and the exit side of the diffractive optical element 50 (the incident side of the laser light Ray 2 and the exit side of the laser light Ray 2).

[0027] Figure 3 shows an example of a group of dot patterns DP projected onto the projection surface S.

[0028] The dot pattern DP is, for example, circular (see Figure 3), but is not limited to this; it may also be rectangular or of any other shape.

[0029] Furthermore, if the pitch P of the lens 51 (see Figure 2(b)) becomes too small compared to the wavelength λ of the laser light emitted from the laser light source 20, diffraction will be difficult to occur. Therefore, as long as there are enough lenses 51 within the beam angle of the laser light to cause diffraction, the pitch P should be sufficiently larger than the wavelength λ of the laser light, for example, 5 times or more, preferably 10 times or more.

[0030] The pitch P of lens 51 is, for example, 10 μm, and the height H is, for example, 7 μm.

[0031] The diffractive optical element 50 may be a transmissive diffractive optical element (DOE) or a reflective diffractive optical element (DOE). The material of the transmissive diffractive optical element 50 is, for example, polydimethylsiloxane (PDMS) with a refractive index of 1.53, but other materials such as acrylic or polycarbonate may be used as long as they are light-transmitting materials with a refractive index greater than 1.0. On the other hand, the material of the reflective diffractive optical element 50 may be a metallic material.

[0032] Here, if the beam diameters of the laser beams Ray2 (parallel light) of each color incident on the diffractive optical element 50 are the same (approximately the same), then the size of the dot pattern DP of each color projected onto the projection surface S will be the same (approximately the same) regardless of the wavelength of the laser beam incident on the diffractive optical element 50. For example, if the beam diameters of the red and green laser beams Ray2 (parallel light) incident on the diffractive optical element 50 are the same (approximately the same), then the size of the red dot pattern DP projected onto the projection surface S will be the same (approximately the same). R Size D1 (see Figure 4(a)) = Green dot pattern DP projected onto projection plane S G The size will be D2 (see Figure 4(b)). Figure 4(a) shows the red dot pattern DP. R Size D1, dot spacing L R As an example, Figure 4(b) shows a green dot pattern DP. G Size D2, dot spacing L G This is one example.

[0033] On the other hand, the longer the wavelength of the laser light Ray2 (parallel light) incident on the diffractive optical element 50, the larger the dot pitch of the dot pattern DP projected onto the projection plane S. For example, the red dot pattern DP projected onto the projection plane S when red laser light Ray2 (parallel light) is incident on the diffractive optical element 50 R The dot pitch L R (see Fig. 4(a)) The green dot pattern DP projected onto the projection plane S when green laser light Ray2 (parallel light) is incident on the diffractive optical element 50 G The dot pitch L G (see Fig. 4(b)). The reason is as follows.

[0034] Fig. 5 is a diagram for explaining that the dot pitch of the dot pattern DP projected onto the projection plane S becomes larger.

[0035] That is, the diffractive optical element 50 (DOE) is an element that generates light of a specific pattern by utilizing light diffraction and interference. The simplest diffractive optical element (DOE) has a sawtooth-shaped periodic structure, and the light reflected or transmitted by the diffractive optical element diffracts and spreads, and the intensity at positions satisfying the interference conditions increases, resulting in a dot pattern.

[0036] From the following equation of the interference condition, the longer the wavelength of the light incident on the diffractive optical element, the larger the diffraction angle θm (≧0) (see Fig. 5), and the larger the dot pitch.

[0037]

Equation

[0038] As described above, when the beam diameters of the laser beams Ray2 (parallel light) of each color incident on the diffractive optical element 50 are the same (approximately the same), the size of the dot patterns DP of each color projected onto the projection surface S will be the same (approximately the same) regardless of the wavelength of the laser beam incident on the diffractive optical element 50. On the other hand, the longer the wavelength of the laser beams Ray2 (parallel light) incident on the diffractive optical element 50, the larger the dot spacing of the dot pattern DP projected onto the projection surface S. Therefore, the longer the wavelength of the laser beam incident on the diffractive optical element 50, the lower the density of the dot pattern DP projected onto the projection surface S.

[0039] Therefore, the longer the wavelength of the laser light incident on the diffractive optical element 50, the smaller the total area of ​​dots (emission points) per unit area of ​​the dot pattern DP projected onto the projection surface S (or the luminous flux per unit area of ​​the dot pattern DP projected onto the projection surface S, i.e., the illuminance), and as a result, the dot pattern DP projected onto the projection surface S appears darker. For example, a green dot pattern DP projected onto the projection surface S G (See Figure 4(b)) Red dot pattern DP projected onto projection plane S R (See Figure 4(a)) has the drawback of appearing darker.

[0040] Next, we will describe two example configurations 1 and 2 for solving the above problems. <Configuration Example 1> In Configuration Example 1, the longer the wavelength of the laser light incident on the diffractive optical element 50, the larger the spot size (emission point) of the dot pattern DP projected onto the projection surface S, so that the total area of ​​dots (emission points) per unit area of ​​each colored dot pattern DP projected onto the projection surface S is the same (approximately the same) for all of them. For example, as shown in Figure 6, the red dot pattern DP projected onto the projection surface S R The spot (light point) size D1 is increased, and the red dot pattern DP R Spot size D1 > Green dot pattern DP G Let the spot size be D2. Figure 6 shows the red dot pattern DP projected onto the projection surface S, compared to Figure 4(a). RThis is an example of increasing the spot (light-emitting point) size D1. This is achieved by using a lens 30 (collimating lens) with an appropriate focal length. In other words, the spot size of the dot pattern DP projected onto the projection surface S can be made relatively larger by using a lens 30 with a relatively long focal length. Therefore, by using a lens 30 (collimating lens) with an appropriate focal length, the total area of ​​dots (light-emitting points) per unit area of ​​each color dot pattern DP projected onto the projection surface S can be made the same (or approximately the same). Furthermore, the curvature of the curved surface of the lens 30 can be made relatively larger to relatively enhance the diffuseness.

[0041] As described above, in Configuration Example 1, regardless of the wavelength of the laser light incident on the diffractive optical element 50, the total area of ​​dots (emission points) per unit area of ​​each colored dot pattern DP projected onto the projection surface S is the same (approximately the same) for all of them.

[0042] Therefore, in Configuration Example 1, even if the wavelength of the laser light incident on the diffractive optical element 50 becomes longer, for example, even if the green laser light source 20G and the red laser light source 20R are lit in that order, it is possible to prevent the dot patterns DP of each color projected onto the projection surface S from appearing dark.

[0043] In Configuration Example 1, the beam diameters of each color of laser light incident on the diffractive optical element 50 are different from each other. That is, the longer the wavelength of the laser light incident on the diffractive optical element 50, the larger the beam diameter of the laser light incident on the diffractive optical element 50. For example, the beam diameter of the red laser light Ray2 incident on the diffractive optical element 50 > the beam diameter of the green laser light Ray2 incident on the diffractive optical element 50 > the beam diameter of the blue laser light Ray2 incident on the diffractive optical element 50. <Configuration Example 2> In Configuration Example 2, the brightness of the laser light sources 20 (20R, 20G, 20B) is controlled so that the luminous flux per unit area, i.e., the illuminance, of each colored dot pattern DP projected onto the projection surface S is the same (or approximately the same) as each other. In other words, the output of the laser light sources 20 should be increased as the wavelength of the laser light sources 20 increases, so that they become relatively brighter. For example, the brightness of laser light source 20R > the brightness of laser light source 20G > the brightness of laser light source 20G. This is achieved by the control device 70. In this case, the total area of ​​dots (light-emitting points) per unit area of ​​each colored dot pattern DP projected onto the projection surface S may be the same (or approximately the same) as each other, or they may be different as well.

[0044] As described above, in Configuration Example 2, regardless of the wavelength of the laser light incident on the diffractive optical element 50, the luminous flux per unit area, i.e., the illuminance, of each colored dot pattern DP projected onto the projection surface S is the same (approximately the same) for all of them.

[0045] Therefore, in Configuration Example 2, even if the wavelength of the laser light incident on the diffractive optical element 50 becomes longer, for example, even if the green laser light source 20G and the red laser light source 20R are lit in that order, it is possible to prevent the dot patterns DP of each color projected onto the projection surface S from appearing dark.

[0046] In the example configuration 2, the beam diameters of each color of laser light incident on the diffractive optical element 50 may be the same or different.

[0047] As described above, according to this embodiment, it is possible to prevent the dot patterns DP of each color projected onto the projection surface S from appearing dark.

[0048] Next, I will explain some variations.

[0049] Figure 7 is a schematic diagram of the lighting device 10A, which is a modified example 1.

[0050] In the above embodiment, an example was described in which multiple combinations of laser light sources 20 and lenses 30 are used, and one diffractive optical element 50 is used, but the embodiment is not limited to this. For example, as shown in Figure 7, multiple combinations of laser light sources 20, lenses 30, and diffractive optical elements 50 may be used. In this case, the dichroic prism 40 may be omitted.

[0051] Figure 8 is a schematic diagram of the lighting device 10B, which is a modified example 2.

[0052] As shown in Figure 8, an optical element 60 may be placed between the diffractive optical element 50 and the projection surface S to block (e.g., reflect or absorb) at least a portion of the Ray 3 light group converted by the diffractive optical element 50, thereby forming an image on the projection surface S.

[0053] For example, the optical element 60 may be a physical mask that includes an image (for example, the arrow image shown in Figure 9) composed of an opaque region that does not transmit visible light (ray group Ray 3) and a transmissive region that does transmit visible light. Figure 9 is an example of an optical element 60 (physical mask). In Figure 9, the arrow region A1 represents an opaque region that does not transmit visible light. This opaque region is a filter region that reflects or absorbs visible light. On the other hand, in Figure 9, the hatched region HT1 represents a transmissive region that transmits visible light. By using a physical mask as the optical element 60, an image composed of multiple dot patterns DP can be formed (projected) onto the projection surface S. Figure 10 is an example of an image composed of multiple dot patterns DP formed on the projection surface S.

[0054] The optical element 60 may be any optical element capable of forming an arbitrary image (for example, the arrow image shown in Figure 9) projected onto the projection surface S according to control from the control device, such as a transmissive liquid crystal element, a reflective liquid crystal element, or a DMD (Digital Mirror Device) including a group of micromirrors. By using this optical element as the optical element 60, any image (see, for example, Figure 10) composed of multiple dot patterns DP can be formed (projected) onto the projection surface S.

[0055] All the numerical values ​​shown in the above embodiments are examples only, and it goes without saying that other appropriate numerical values ​​can be used.

[0056] The embodiments described above are in all respects merely illustrative. The description of the embodiments above should not be construed as limiting the disclosure. The disclosure can be implemented in a variety of other ways without departing from its spirit or main features. [Explanation of Symbols]

[0057] 10, 10A, 10B…Lighting device 20 (20B, 20G, 20R)... Laser light source 30... Lens 40… Dichroic prism 50…Diffractive optical elements 51... Lens 60…Optical elements 70...Control device A1...Arrow area DP(DP G DP R )...dot pattern HT1…Hatching area L G , L R ...dot spacing P...Pitch Ray1, Ray2… Laser light Ray3…group of rays S…Projection surface θm...diffraction angle

Claims

1. It includes a diffractive optical element that receives laser light in the visible wavelength range and converts the laser light into a group of rays corresponding to a group of dot patterns projected onto a projection surface. The longer the wavelength of the laser light incident on the diffractive optical element, the larger the dot spacing of the dot pattern projected onto the projection surface, and the larger the spot size of the dot pattern projected onto the projection surface.

2. The illumination device according to claim 1, wherein the longer the wavelength of the laser light incident on the diffractive optical element, the larger the beam diameter of the laser light incident on the diffractive optical element.

3. The lighting device according to claim 1, wherein the total area of ​​dots per unit area of ​​each colored dot pattern projected onto the projection surface is the same for all of them.

4. The lighting device according to claim 1, wherein the luminous flux per unit area of ​​each colored dot pattern projected onto the projection surface is the same for all of them.

5. Multiple laser light sources that emit laser light of different visible wavelengths, The system further comprises a plurality of lenses provided corresponding to a plurality of laser light sources, The illumination device according to claim 1, wherein each of the plurality of lenses is a collimating lens that converts the laser light emitted by the laser light source corresponding to the lens into parallel light.

6. It includes a diffractive optical element that receives laser light in the visible wavelength range and converts the laser light into a group of rays corresponding to a group of dot patterns projected onto a projection surface. A lighting device in which the luminous flux per unit area of ​​each colored dot pattern projected onto the projection surface is the same for all of them.

7. Multiple laser light sources that emit laser light of different visible wavelengths, The system further comprises a control device for controlling the brightness of each of the multiple laser light sources, The lighting device according to claim 6, wherein the control device controls the brightness of a plurality of laser light sources such that the luminous flux per unit area of ​​each colored dot pattern projected onto the projection surface is the same for all of them.

8. It includes a diffractive optical element that receives laser light in the visible wavelength range and converts the laser light into a group of rays corresponding to a group of dot patterns projected onto a projection surface. A lighting device in which the brightness per unit area of ​​each colored dot pattern projected onto the projection surface is the same for all of them.

9. The optical element further comprises an optical element disposed between the diffractive optical element and the projection surface, The illumination device according to any one of claims 1, 6, or 8, wherein the optical element forms an image on the projection surface by blocking at least a portion of the group of light rays converted by the diffractive optical element.

Images