Lighting device, sensor device, and traveling body

Abstract

The illumination device (10) comprises: a light source (12) which emits parallel light or divergent light; a diffusion element (14) which receives light emitted from the light source (12) and emits light with a diffusion angle of 50° or more and 110° or less; and a lens group (16) which has a negative focal power, receives light from the diffusion element (14) at a first surface (16a), and emits light from a second surface (16b) with a distribution angle of 140° or more.

Description

Technical Field

[0001] This invention relates to lighting devices. Background Technology

[0002] In recent years, lighting devices that use lasers as a light source have been used for illumination of surveillance sensors, such as those used as vehicle-mounted peripheral or in-vehicle surveillance sensors, and for monitoring of moving objects like people in facilities such as hospitals and factories.

[0003] In such a lighting device, in order to illuminate as wide a range as possible with laser light emitted from a single light source, it is required to increase the diffusion of the laser beam and emit light at a wide angle (e.g., 180 degrees). Here, when referred to as a wide angle, there are cases where it is made wide in the horizontal direction, and cases where it is made wide in both the horizontal and vertical directions.

[0004] Conventional methods for laser diffusion include using diffuser plates (such as frosted or opalescent diffusers), microlens arrays, microprism arrays, and DOEs (diffuser elements). However, there are limitations to efficiently widening the laser field of view when using only a diffuser plate or diffuser element (hereinafter referred to as "diffraction element"). To overcome this limitation, a method is known to achieve wide-angle diffusion by combining a diffuser element with a lens having negative optical power, thereby further extending the light diffused by the diffuser element.

[0005] For example, Patent Document 1 discloses a laser illumination device for the purpose of ensuring the safety of the human eye, comprising: a laser source; a micro-element lens that amplifies the laser from the laser source; and a meniscus lens having a negative optical power that amplifies the laser from the micro-element lens.

[0006] [Prior art literature]

[0007] [Patent Documents]

[0008] Patent Document 1: Japanese Patent Application Publication No. 2018-133138 Summary of the Invention

[0009] [The problem the invention aims to solve]

[0010] In the laser illumination device disclosed in Patent Document 1, a meniscus lens with negative optical power is provided behind a micro-element lens in order to ensure eye safety by increasing the size of the light source projected onto the human eye. However, regarding the light distribution angle, only a wide angle (e.g., 140 degrees) is described, and the configuration for further extending the light is not disclosed.

[0011] The present invention was made in view of the above circumstances, and its object is to provide an illumination device that can extend light over a wider angle.

[0012] [Technical solutions for addressing technical problems]

[0013] To address the aforementioned issues, one aspect of the present invention provides an illumination device comprising: a light source that emits parallel or divergent light; a diffusion element that receives light emitted from the light source and emits light at a diffusion angle of 50° or more and 110° or less; and a lens assembly having negative optical power, receiving light from the diffusion element on a first surface and emitting light from a second surface at a light distribution angle of 140° or more.

[0014] Furthermore, any combination of the above-mentioned constituent elements, or any scheme that transforms the present invention into a method, apparatus, system, etc., is also valid as a scheme of the present invention.

[0015] [Invention Effects]

[0016] According to the present invention, it is possible to provide a lighting device that can extend light over a wider angle. Attached Figure Description

[0017] Figure 1 This is a schematic cross-sectional view of a lighting device according to an embodiment of the present invention.

[0018] Figure 2 This is a schematic perspective view of a lighting device according to an embodiment of the present invention.

[0019] Figure 3 It is a diagram that defines the angle of light emitted from the components of a lighting device relative to the optical axis.

[0020] Figure 4 It is a diagram showing the relationship between the angle of the light ray relative to the Z-axis and the azimuth angle of the light ray L.

[0021] Figure 5 (a) and Figure 5 (b) is a diagram used to illustrate the diffusion element.

[0022] Figure 6 This is a top view showing a portion of the diffusion element.

[0023] Figure 7 This is a conceptual diagram representing a beam of light emitted from a diffuser element.

[0024] Figure 8 This is a graph showing an example of the calculated light emission efficiency of a lighting device.

[0025] Figure 9 This is another example of a graph showing the calculated light emission efficiency of a lighting device.

[0026] Figure 10 It means at θ 3max When θ = 90°, 1maxA graph showing the change in contribution rate when the change occurs.

[0027] Figure 11 It means at θ 3max When θ = 85°, 1max A graph showing the change in contribution rate when the change occurs.

[0028] Figure 12 It means at θ 3max When θ = 80°, 1max A graph showing the change in contribution rate when the change occurs.

[0029] Figure 13 It means at θ 3max When θ = 75°, 1max A graph showing the change in contribution rate when the change occurs.

[0030] Figure 14 It means at θ 3max When θ = 70°, 1max A graph showing the change in contribution rate when the change occurs.

[0031] Figure 15 Is Figures 10-14 A diagram showing the light emission efficiency of a lighting device under various conditions, represented by contour lines.

[0032] Figure 16 It is a graph showing the light intensity distribution of light emitted from the light source used in the simulation.

[0033] Figure 17 This is a top view of the microlens array used in the simulation.

[0034] Figure 18 yes Figure 17 A partial cross-sectional view of the microlens array shown.

[0035] Figure 19 This is a schematic cross-sectional view of the meniscus lens used in the simulation.

[0036] Figure 20 This is a diagram showing the configuration of a lighting device used for simulation.

[0037] Figure 21 This is a diagram showing a measurement system for measuring the light distribution of an illumination device.

[0038] Figure 22 It is a graph showing the light intensity distribution of the lighting device obtained through simulation and the actual measured light intensity distribution of the lighting device.

[0039] Figure 23 This is a diagram showing an example of the light distribution of a lighting device.

[0040] Figure 24 It means having Figure 23 A diagram of a moving robot with a lighting device showing the light distribution pattern.

[0041] Figure 25 This is an example diagram showing a cross-section of a portion of a microlens array.

[0042] Figure 26 yes Figure 25 A schematic magnified view of the microlens shown.

[0043] Figure 27 (a) ~ Figure 27 (g) is a diagram showing an example of the cross-sectional shape of a microlens.

[0044] Figure 28 This is an example of how F(θ3) = {cos(0.9 × θ3)} is represented. -0.1 F(θ3) = {cos(0.415×θ3)} -10 The graph of the function, and the graph of several functions contained within these functions.

[0045] Figure 29 This is an example of the expression F(θ3) = {cos(0.4 × θ3)}. -1.5 F(θ3) = {cos(0.465 × θ3)} -7.5 The graph of the function, and the graph of several functions contained within these functions.

[0046] Figure 30 This is shown by F(θ3) = {cos(0.512×θ3)} -3 A diagram showing the distribution of light intensity.

[0047] Figure 31 This is another example of a graph showing the calculated results of the light emission efficiency of a lighting device.

[0048] Figure 32 This is another example of a graph showing the calculated results of the light emission efficiency of a lighting device.

[0049] Figure 33 It means at θ 3max When θ = 90°, 1max A graph showing the change in contribution rate when the change occurs.

[0050] Figure 34 It means at θ 3max When θ = 85°, 1max A graph showing the change in contribution rate when the change occurs.

[0051] Figure 35 It means at θ 3max When θ = 80°, 1maxA graph showing the change in contribution rate when the change occurs.

[0052] Figure 36 It means at θ 3max When θ = 75°, 1max A graph showing the change in contribution rate when the change occurs.

[0053] Figure 37 It means at θ 3max When θ = 70°, 1max A graph showing the change in contribution rate when the change occurs.

[0054] Figure 38 Is Figures 33-37 A diagram showing the light emission efficiency of a lighting device under various conditions, represented by contour lines.

[0055] Figure 39 It will be used to implement Figure 30 The diagram of the meniscus lens with light distribution is shown on the r-Z coordinate system.

[0056] Figure 40 It is a graph showing the light intensity distribution of the lighting device obtained through simulation and the actual measured light intensity distribution of the lighting device. Detailed Implementation

[0057] The embodiments of the present invention will now be described. Where the same or equivalent constituent elements, components, and processes are labeled with the same reference numerals in the various figures, repeated descriptions will be omitted where appropriate. Furthermore, the embodiments are not limiting of the invention but merely illustrative, and all features and combinations thereof described in the embodiments may not be the essential content of the invention.

[0058] Figure 1 This is a schematic cross-sectional view of the lighting device 10 according to an embodiment of the present invention. Figure 2 This is a schematic perspective view of the lighting device 10 according to an embodiment of the present invention. Figure 1 and Figure 2 As shown, the lighting device 10 includes a light source 12, a diffusion element 14, and a lens group 16.

[0059] Light source 12 emits parallel or divergent light. Light source 12 is particularly capable of being a laser source that emits coherent laser light. Diffusion element 14 receives light emitted from light source 12 and emits light with a diffusion angle of 50° or more and 110° or less. Diffusion element 14 can be plate-shaped, and is particularly capable of being a microlens array with multiple microlenses on any one of the main surfaces of the plate. Lens group 16 has negative optical power. Lens group 16 receives light emitted from diffusion element 14 and emits light with a beam distribution angle of 140° or more. Lens group 16 is particularly capable of being a single meniscus lens. A "lens group" can consist of one or more lenses; in the case of multiple lenses, it refers to a lens group consisting of these multiple lenses as a single unit.

[0060] The larger the diffusion angle, the lower the total light transmittance of the diffusion element 14 equipped with microlenses. On the other hand, regarding the total light transmittance of the lens group 16, the larger the diffusion angle, the larger the incident angle towards the lens surface and the greater the reflectivity, thus the lower the transmittance.

[0061] Here, a laser light source is used as the light source 12, and the axis of symmetry of the intensity distribution of the light emitted from the light source 12 is set as the optical axis Ax of the illumination device 10. The optical axis Ax can be perpendicular to the light emission surface 12a of the light source 12, or it can pass through the center of the light emission surface 12. Figure 1 As shown, for the purpose of subsequent explanation, the X, Y, and Z coordinate axes are determined by taking the direction parallel to the optical axis Ax as the Z direction, the direction perpendicular to the Z direction and parallel to the paper as the Y direction, and the direction perpendicular to the paper as the X direction.

[0062] Lens group 16 is configured as a single lens or a single lens equivalent to lens group 16. The surface that receives light emitted from diffuser element 14 is designated as surface 16a, and the surface that emits light approximately opposite surface 16a is designated as surface 16b. In the case where lens group 16 is a single lens of the meniscus, when the curvature of surface 16a is set as C1 and the curvature of surface 16b is set as C2, C1 < 0, C2 < 0, and |C2| < |C1| (in the case of negative optical power). Curvature is the reciprocal of the paraxial radius when the paraxial region of each surface approximates a sphere. In a meniscus lens, when |C2| < |C1|, it is sometimes referred to as a meniscus lens with negative optical power.

[0063] Figure 3 This is a diagram defining the angle of light emitted from the constituent elements of the lighting device 10 relative to the optical axis. For example... Figure 3 As shown, the angles of the emitted light from the first surface 16a and the second surface 16b of the lens group 16 relative to the Z-axis are set as θ1, θ2, and θ3, respectively. If θ1 is less than 25° (diffusion angle less than 50 degrees), the second surface 16b of the lens group 16 is either flat or concave, and the reflectivity at its interface becomes very high, resulting in a decrease in the overall light utilization efficiency of the lighting device 10. If θ1 exceeds 55° (diffusion angle exceeds 110 degrees), the tilt angle of the lens surface of the microlens of the diffusion element 14 increases, and the reflection loss increases, thus reducing the overall light utilization efficiency of the lighting device 10. Therefore, it is preferable that θ1 is 25° or more and 55° or less (50° ≤ 2 × θ1 ≤ 110°).

[0064] When the angle between the emitted light of the lighting device 10 and the optical axis Ax is set to θ3, the maximum value of 2×θ3 can be a light distribution angle of 160° or more and 180° or less.

[0065] Furthermore, the lighting device 10 satisfies the following equation (1) with respect to θ1 to θ3.

[0066] θ2-θ1≦θ3-θ2 (1)

[0067] The left side of equation (1) represents the change in the angle of light in the first surface 16a of lens group 16, and the right side of equation (1) represents the change in the angle of light in the second surface 16b of lens group 16. When the condition of equation (1) is satisfied, the transmittance of the meniscus lens becomes higher.

[0068] When θ1 is small, the transmittance reaches its maximum when θ2 - θ1 = θ3 - θ2. On the other hand, when θ1 is large, to satisfy the condition θ2 - θ1 = θ3 - θ2, the tilt angle of the first surface 16a must exceed 90°, making the manufacture of the lens group 16 difficult. In this case, the optimal condition is when the tilt angle of the first surface 16 is less than 90° and θ2 - θ1 is as close as possible to θ3 - θ2.

[0069] Furthermore, when the intensity of light emitted from the lens group 16 per unit solid angle is set to F(θ3), the illumination device 10 satisfies the following equation (2) with respect to F(θ3).

[0070] F(θ3) = (1 - R) 32 (θ2))×F(θ2)×Δθ2×sinθ2 / (Δθ3×sinθ3)=(1-R 32 (θ2))×(1-R 21 (θ1))×F(θ1)×Δθ1×sinθ1 / (Δθ3×sinθ3)=constant (2)

[0071] Among them, R 21 (θ1) is the reflection loss in the first surface 16a of lens group 16, R 32 (θ2) is the reflection loss in the second surface 16b of the lens group 16, F(θ1) is the intensity of light emitted from the diffuser element 14 per unit solid angle, and F(θ2) is the intensity of light emitted from the second surface 16b of the lens group 16 per unit solid angle. Additionally, Δθ1, Δθ2, and Δθ3 are small angles of θ1, θ2, and θ3, respectively.

[0072] In order to keep the intensity (luminance) of light emitted from the lighting device 10 per unit solid angle constant, the relationship of equation (2) needs to be satisfied. Figure 4 This represents the relationship between the angle θ of ray L relative to the Z-axis and the azimuth angle Φ of ray L. Equation (2) assumes that F(θ1), F(θ2), and F(θ3) are constant and independent of the azimuth angle Φ.

[0073] In the lighting device 10, when the intensity of the light emitted from the lighting device 10 per unit solid angle is set as F(θ3), equation (2) can also be satisfied, and F(θ3) increases as θ3 increases.

[0074] In lighting fixtures, it is sometimes desirable to vary the light intensity according to θ3. For example, when monitoring people below using a ceiling-mounted surveillance device, the distance to a person directly below the device is closer, while the distance to a person diagonally below is farther. In this case, increasing the intensity of light diagonally below the device can expand the monitored area compared to directly below the device. This is not limited to a function that increases with θ3; for example, the function shown in equation (3A) can be cited.

[0075] F(θ3) = (cosθ3) -2 (3A)

[0076] Furthermore, in order to correct the difference in sensitivity between the center and the periphery of the light detection unit, it is sometimes preferable to increase the light intensity of the illumination device as θ3 increases. As a function that increases with the increase of θ3, for example, the functions shown in the following equations (3B) and (3C) can be cited.

[0077] F(θ3) = (cosθ3) -4 (3B)

[0078] F(θ3) = (cosθ3) -n (3C)

[0079] As the light source 12 used in the lighting device 10 of this embodiment, a highly directional light source such as a surface-emitting laser (VCSEL) or a surface-emitting laser diode can be used. Alternatively, a component combining a low-directional light-emitting element such as an LED and a collimating lens can also be used as the light source 12. The VCSEL or laser can also be composed of an array of multiple light-emitting points or light-emitting elements arranged in a housing. The light emitted from the light source 12 does not need to be perfectly collimated; for example, it can be diffused light diffused at about 20°.

[0080] The light source 12 has a light emitting surface (light-emitting surface) 12a, from which light is emitted with a luminous intensity distribution within a defined angle. The axis along which the luminous intensity distribution is approximately symmetrical is designated as the optical axis Ax. The optical axis Ax can be perpendicular to the light emitting surface 12a, perpendicular to a local bottom surface of the housing of the light source 12, or pass through the center of the light emitting surface 12a. The light source 12 is generally arranged such that the optical axis Ax is parallel to the Z-axis of an orthogonal coordinate system. The illumination device 10 or its components will be described below.

[0081] When using a light-emitting element made of semiconductors such as lasers or LEDs as the light source 12, small size and low power consumption are advantageous. In addition, it is more advantageous than light sources such as incandescent lamps and fluorescent lamps that emit light by means of resistance heating, due to its good responsiveness when modulation is applied.

[0082] The structure of the diffusion element 14 is not limited as long as it is a component that receives light emitted from the light source 12 and emits light with an amplified spread angle. As the diffusion element 14, the following diffusion plates can be used: a flat plate made of glass, resin, etc., a frosted type diffusion plate whose surface is roughened by grinding, polishing, or sandblasting; an etched type diffusion plate whose surface is etched with hydrofluoric acid or the like to apply a specified roughness; and a protein type diffusion plate in which a milky white, white, or gray film is formed on the surface of a flat plate made of glass or resin.

[0083] Furthermore, elements with multiple tiny microlenses, microprisms, and other concave-convex structures formed on the surface of a substrate made of glass, resin, etc., can also be used as diffusion elements 14 from the point of view of their good performance and control.

[0084] The diffusion element 14, which is composed of a microlens array, is an element with tiny lenses (microlenses) randomly arranged on its surface or an element with cylindrical lenses arranged in a row. Each microlens can be convex or concave, or it can be a combination of convex and concave lenses.

[0085] The size of the microlenses in the diffusion element 14 does not need to be uniform, and the height of the lenses can also vary. As long as a specified diffusion angle is obtained and uniform light intensity is achieved in the necessary directions, the shape of the microlenses when viewed from the incident side (top view) can be polygonal, circular, elliptical, or a combination thereof. In addition, gaps can be left between the microlenses.

[0086] The diameter of each microlens in the diffusion element 14 can be from several μm to hundreds of μm, for example, from 10 μm to 200 μm.

[0087] The microlens array in the diffusion element 14 can be an element formed by molding resin or glass using a mold, an element formed by injecting resin into a mold, an element formed by etching the surface of glass with acid, or an element formed by sandblasting to create tiny bumps and depressions. The microlenses can be formed from a material that is translucent at the wavelength of the light source 12, and do not need to be transparent at other wavelengths.

[0088] Figure 5 (a) and Figure 5 (b) is a diagram used to illustrate the diffusion element 14. Figure 5(a) is a probability front view of the diffusion element 14. Figure 5 (b) is Figure 5 (a) is a schematic A-A cross-sectional view of the diffusion element 14 shown. Figure 6 This is a top view showing a portion of the diffuser element 14.

[0089] The diffusion element 14 is a microlens array including a plate 20 and a plurality of microlenses 22 formed on the surface of the plate 20.

[0090] The diffuser element 14 shown here is quadrilateral in frontal view, but its shape is not limited as long as it has sufficient size to receive light from the light source 12. In addition to polygons, it can also be circular, elliptical, etc.

[0091] In other embodiments of the diffusion element 14, the microlens 22 may also be formed on the main surface of the back of the plate 20, in which case the diffusion efficiency can be improved. Alternatively, the microlens 22 may be formed on the surface of a refractive convex or concave lens, in which case the diffused light can be refracted, and the amplification or reduction of the diffusion angle can be controlled. The diffusion element 14 may also include these microlenses 22.

[0092] In addition to including such a microlens 22, the diffusion element 14 can enhance its diffusion capability by containing light-scattering particles (diffusing particles) within its interior. The same effect can be expected when a film containing diffusing particles is formed on the surface of the diffusion element 14 or the surface of the microlens 22. The size of the light-scattering particles can be approximately 1 nm to 100 nm in the case of Rayleigh scattering, and larger, or approximately 1 μm to 10 μm in the case of Mie scattering. Besides resins such as PMMA, the particles can also be composed of particles made of SiO2, MgF2, or their hollow particles.

[0093] Furthermore, an anti-reflective film (including a reflective film that suppresses reflection even when the reflectivity is not substantially zero) can be formed on the surface of the diffusion element 14 to suppress reflection and improve light transmittance. By forming an anti-reflective film, the brightness of the illumination from the lighting device 10 can be improved. The anti-reflective film is obtained by coating the surface of the diffusion element with one or more layers of inorganic materials such as MgF2, SiO2, TiO2, or Ta2O5, or materials such as resin. An anti-reflective film can also be obtained by coating a layer containing hollow or solid particles such as SiO2 or MgF2 within an adhesive. As a coating method, in addition to physical methods such as vacuum evaporation, sputtering, and ion plating, a method of coating a liquid precursor of the film onto the surface and then drying it can also be used.

[0094] Lens group 16 has a lens system that receives light emitted through diffuser element 14 at a predetermined expansion angle, and then amplifies the expansion angle to emit light. The lens system with the function of amplifying the expansion angle is generally a concave lens system. A concave lens system is a lens system with negative optical power. Lens group 16 may also be composed of more than one lens, including a lens group with surfaces glued together. Furthermore, in adjacent lenses, a layer with a refractive index different from that of the lens may be included between the surfaces.

[0095] When lens group 16 is composed of a single axially symmetric lens (single lens), examples include plano-concave lenses, concave-concave lenses, and concave-convex lenses. Concave-convex lenses are sometimes referred to locally as meniscus lenses, and meniscus lenses with negative optical power can also be those where the peripheral thickness is greater than the central thickness. Meniscus lenses possess some of the functions of both concave and convex lenses, and are generally known to reduce spherical aberration compared to plano-concave lenses, and have advantages in terms of ease of controlling their spread angle.

[0096] The lens group 16 can be made of a material that is transmissive at the wavelength of the light source 12, and does not need to be transparent at other wavelengths. It can be formed using resin or glass as the material.

[0097] Furthermore, when a meniscus lens is used as lens group 16, by including light-scattering particles (diffusing particles) inside the lens, magnification based on the expansion angle of lens group 16 can be achieved through their light diffusion effect. The same effect can be expected when a film containing the diffusing particles is formed on the lens surface. The size of the light-scattering particles is as described above. The particles can be colorless and transparent; in addition to resins such as PMMA, particles composed of SiO2 or MgF2 can be used, and their hollow particles can also be used.

[0098] Furthermore, an anti-reflective film (including a reflective film that suppresses reflection even when the reflectivity is not substantially zero) can be formed on the surface of the lens group 16 to suppress reflection and improve light transmittance. By forming an anti-reflective film, the brightness of the illumination from the lighting device 10 can be improved. The anti-reflective film is obtained by coating the surface of the lens with one or more layers of inorganic materials such as MgF2, SiO2, TiO2, or Ta2O5, or materials such as resin. An anti-reflective film can also be obtained by coating an adhesive layer containing particles of hollow or solid SiO2, MgF2, etc. In addition to physical methods such as vacuum evaporation, sputtering, and ion plating, a method can also be used to fix the film by coating a liquid precursor of the film onto the surface and then drying or curing it.

[0099] The lighting device 10 according to an embodiment of the present invention is characterized in that it includes: a light source 12; a diffusion element 14 that receives light emitted from the light source 12 and emits light at a predetermined expansion angle; and a lens group 16 that receives light emitted from the diffusion element 14 and emits light at a further magnified predetermined expansion angle.

[0100] The following illumination device 10 is used as an example: The light source 12 uses a laser (VCSEL array; multiple VCSEL type semiconductor lasers are arranged in an array and integrated in the housing) with a light emitting surface of about 1 mm × 1 mm, the diffusion element 14 uses a generally flat microlens array as shown in Figure (5), and the lens group 16 uses an axisymmetric meniscus lens.

[0101] In a space formed by orthogonal coordinate axes, the light source 12 is arranged such that the optical axis Ax is parallel to the Z direction (the optical axis Ax can also be used as the Z-axis). The diffuser element 14 is arranged such that the optical axis Ax of the light source 12 passes through the geometric center of the diffuser element 14, receiving light from the light source 12. In this case, the light-receiving surface of the diffuser element 14 preferably has a size sufficient to receive or receive approximately all of the light emitted from the light source 12 within the necessary range. When multiple microlenses are formed on one side of a generally parallel plate, the surface on which the microlenses are formed can be used as the light-receiving surface, or the surface opposite to it can be used as the light-receiving surface. The diffuser element 14, which is composed of a microlens array, is a generally parallel plate with a top view size of 0.25 mm × 0.25 mm to 5 mm × 5 mm and a thickness of 0.1 mm to 3 mm. At least one side has multiple microlenses formed, each with a size of 2.5 μm to 100 μm and a sag (microlens height) of 5 μm to 500 μm.

[0102] When an axisymmetric meniscus lens is used as lens group 16, the meniscus lens 16 is arranged such that the axis of symmetry of the lens (which may also be the optical axis of the lens) coincides with the axis Ax of the light source, and the concave surface faces the diffuser element 14. The meniscus lens 16 has, for example, a diameter of 5 mm to 50 mm and a center thickness of 0.25 mm to 15 mm.

[0103] Furthermore, the lighting device 10 may also include a housing (not shown) that integrates and holds these components and other components together.

[0104] The shape of the meniscus lens 16 will now be described. Light incident from the light source 12 onto the diffuser element 14 is diffused by the microlenses arranged in the diffuser element 14, extending it to a predetermined range. Figure 1 , Figure 2As shown, the light emitted from the diffuser element 14 is diffused in a manner that is approximately symmetrical with respect to the optical axis Ax, extending inside a cone, pyramid, or frustum-shaped cone or frustum-shaped cone.

[0105] Regarding the light emitted from the diffuser element 14, its light intensity can vary depending on the angle (θ1) with respect to the Z-axis. However, when the light intensity is constant regardless of θ1, it is easy to design the meniscus lens 16 of the subsequent stage (rear lens), so it is preferred.

[0106] On the other hand, the light intensity can also be constant in the direction of rotation (Φ direction) centered on the Z-axis. When the shape of the meniscus lens 16 in the subsequent stage is symmetrical with respect to the Z-axis, it is advantageous that the light intensity after passing through the diffuser 14 is constant with respect to each Φ, so that the illumination light from the illumination device is uniform and does not need to be corrected by the lens group 16 in the subsequent stage.

[0107] Regarding the light emitted from the diffuser element 14, the angle (θ1) between the light emitted from the diffuser element 14 and the Z-axis (optical axis Ax) is taken as the divergence angle. Considering the divergence angle dependence of the intensity of the light emitted from the diffuser element 14, when the maximum intensity is set as Io (here, it is assumed that the intensity on the optical axis Ax (θ1=0°) is the maximum), the full width at half maximum (FWHM) of the angle of 1 / 2×Io is taken as the diffusion angle. Furthermore, when the maximum intensity Io does not exist on the optical axis Ax (for example, when the light intensity distribution is annular or bat-wing), the difference between the maximum and minimum values ​​of the angle corresponding to the intensity of 1 / 2×Io is taken as the diffusion angle. The diffusion angle of the diffuser element 14, which is composed of microlenses, is preferably 50° or more and 110° or less. If the diffusion angle is less than 50°, the reflection loss in the lens surface when the light is diffused by the meniscus lens 16 in the subsequent stage will increase. If the diffusion angle exceeds 110°, the reflection loss in the diffusion element 14 will increase, and the total amount of light emitted from the illumination device 10 will decrease.

[0108] Light, diffused to a predetermined diffusion angle by the diffusion element 14, is incident on the first surface (light-receiving surface) 16a of the meniscus lens 16, where it is refracted and its divergence angle increases. The light then travels from inside the lens to the second surface (emission surface) (16b) and is refracted out.

[0109] Here, we consider the tracing of light rays emitted from light source 12. For example... Figure 3 As shown, the light emitted from the light-emitting surface 12a of the light source 12 (e.g., a ray parallel to the optical axis Ax) is expanded by the diffusion element 14 to an angle of divergence θ1, by the first surface 16a of the meniscus lens 16 to θ2, and by the second surface 16b of the meniscus lens 16 to θ3. θ1 to θ3 are all angles formed with the Z-axis (optical axis).

[0110] When the light intensity distribution emitted from the diffuser element 14 is symmetrical with respect to the Z-axis, the maximum value of θ1 (θ 1max The divergence angle becomes half of the diffusion angle of the diffusion element 14. Similarly, the maximum divergence angle θ of the first surface 16a and the second surface 16b of the meniscus lens 16 is... 2max and θ 3max They also become half of the diffusion angles of the first surface 16a and the second surface 16b of the meniscus lens 16, respectively.

[0111] Figure 7 This is a conceptual diagram representing the light beam emitted from the diffuser element 14. Consider the light contained in a ring with divergence angles of θ1 and θ1 + Δθ1 (where Δθ1 is a small angle) emitted from the diffuser element 14. Let the light intensity distribution after passing through the diffuser element 14 be F(θ1). Since the light intensity distribution is symmetrical about the Z-axis, F(θ1) remains constant even if the orientation (Φ) changes.

[0112] like Figure 7 As shown, the light energy E(θ1) within the ring of θ1 and θ1+Δθ1 when Δθ1 is sufficiently small is represented by the following equation (4).

[0113] E(θ1) = F(θ1) Δθ1 r1 (2πr1) sinθ1 / (4π r1 2 ) 4π = 2π F(θ1) Δθ1 sinθ1 (4)

[0114] Similarly, after passing through the first surface 16a of the meniscus lens 16, the energy E(θ2) of the light passing through the ring of θ2 and θ2+Δθ2 is expressed by the following equation (5) when Δθ2 is sufficiently small.

[0115] E(θ2) = 2π F(θ2) Δθ2 sinθ2 (5)

[0116] Similarly, after passing through the second surface 16b of the meniscus lens 16, the energy E(θ3) of the light passing through the ring zone of θ3 and θ3+Δθ3 when Δθ3 is sufficiently small is represented by the following equation (6).

[0117] E(θ3) = 2π F(θ3) Δθ3 sinθ3 (6)

[0118] Reflection loss occurs in the first surface 16a and the second surface 16b of the meniscus lens 16. Let the reflection loss generated in the first surface 16a be R. 21 (θ1) Let the reflection loss generated in the second surface 16b be R. 32 When (θ2), the following equations (7) and (8) hold true.

[0119] (1-R) 21 (θ1) F(θ1) Δθ1 sinθ1=F(θ2) Δθ2 sinθ2 (7)

[0120] (1-R) 32 (θ2) F(θ2) Δθ2 sinθ2=F(θ3) Δθ3 sinθ3 (8)

[0121] Therefore, the following equation (9) holds true.

[0122] (1-R 32 (θ2) (1-R) 21 (θ1) F(θ1) Δθ1 sinθ1

[0123] = (1-R) 32 (θ2) F(θ2) Δθ2 sinθ2

[0124] =F(θ3) Δθ3 sinθ3 (9)

[0125] If we consider F(θ3) as expression (9), it becomes as in expression (10).

[0126] F(θ3) = ((1-R) 32 (θ2) F(θ2) Δθ2 sinθ2 / (Δθ3 sinθ3)

[0127] = (1-R) 32 (θ2))(1-R 21 (θ1) F(θ1) Δθ1 sinθ1 / (Δθ3 sinθ3) (10)

[0128] In order to keep the luminance from the lighting device 10 constant, the parameters need to be set in such a way that F(θ3) shown in equation (10) is a constant value.

[0129] On the other hand, in order to increase F(θ3) as θ3 increases, a function that satisfies equation (10) and makes F(θ3) monotonically increase can be used. As examples of such functions, consider the functions shown in equation (11) or (12) below, and the functions shown in equation (3C) above.

[0130] F(θ3) = (cosθ3) -2 (11)

[0131] F(θ3) = (cosθ3) -3 (11)

[0132] When the loss caused by reflection is suppressed by applying an AR (anti-reflection) coating to the lens surface of the meniscus lens 16, the above equation (10) obtained for F(θ3) becomes equation (13) when the reflection loss can be ignored.

[0133] F(θ3) = F(θ2) Δθ2 sinθ2 / (Δθ3 sinθ3)

[0134] =F(θ1) Δθ1 sinθ1 / (Δθ3 sinθ3) (13)

[0135] If F(θ3) is set to a constant value, uniform illumination can be obtained. If F(θ3) is set to a function that increases with θ3, then an illumination device 10 in which the radiation intensity changes according to the function can be obtained.

[0136] According to equation (13), the shape of the lens surface of the meniscus lens 16 is determined for various F(θ1), F(θ2), and F(θ3). For example, if F(θ1) is constant and independent of θ1, and F(θ3) is also constant and independent of θ3, then equation (14) is obtained from equation (13).

[0137] Δθ3 sinθ3=C Δθ1 sinθ1 (14)

[0138] Where C is a constant.

[0139] When θ1 = 0, since the light ray travels parallel to the Z-axis, θ3 = 0. When θ1 = Δθ1, Δθ3 is obtained through equation (14), like θ 3（k） =θ 3（k－1） +Δθ 3（k） (When k=1, due to θ) 3（1－1） =0, therefore θ 3（1） =0+Δθ3=Δθ3) Find θ like this 3（1） While increasing θ1 by Δθ1 successively, we calculate Δθ3 using the above formula, and then... 3（k） =θ 3（k－1） +Δθ3 （k） Thus, by adding to the previous θ3, θ3 corresponding to θ1 can be obtained sequentially from the center of the meniscus lens 16 outwards. The constant C is determined as θ3 with the specified θ1 as the target. In this way, θ3 corresponding to θ1 is obtained. In the case where there is reflection loss on the lens surface of the meniscus lens 16 and F(θ3) is not constant, θ3 corresponding to θ1 can also be obtained similarly by using equations (11) and (12). In this case, since θ2 is not specifically defined, it can take various values. For example, when θ2 = θ · In this case, light is not extended at all in the first surface 16a of the meniscus lens 16, but is significantly bent in the second surface 16b. Furthermore, the case where θ2 < θ1 also holds mathematically. At this time, the light that was extended to θ1 is temporarily narrowed to θ2 and then extended again. Due to the increased reflection loss in the lens surface, the transmittance is greatly reduced.

[0140] If θ1, its corresponding θ2, and its corresponding θ3 are determined, the shapes of the first surface 16a and the second surface 16b of the meniscus lens 16 can be determined by ray tracing. The method is briefly explained below.

[0141] If the meniscus lens 16 is rotationally symmetrical about the Z-axis, then at the intersection of the Z-axis and the meniscus lens 16, the tangent plane of the lens surface is orthogonal to the Z-axis. Therefore, when θ1 = 0, light is incident perpendicularly on the lens surface of the meniscus lens 16.

[0142] Light incident on the first surface 16a of the meniscus lens 16 at an angle θ1 = Δθ1 is refracted at this surface and travels in the direction of θ2. At this point, the incident angle to the lens surface is uniquely determined according to the law of refraction, and consequently, the angle between the lens surface and the Z-axis is also uniquely determined. Similarly, by successively increasing θ1 by Δθ1 while calculating the angle between the lens surface and the Z-axis through which the light passes, the tilt angle of the lens surface through which light at angle θ1 passes can be determined.

[0143] Since the tilt angle of the central lens surface of the meniscus lens 16 is determined, the surface shape of the meniscus lens 16 can be determined by smoothly connecting the lens surfaces from their coordinates towards the outer periphery, i.e., by continuously changing the differential coefficients of the lens surfaces. The shape of the second surface 16b of the meniscus lens 16 can also be determined by the same calculation.

[0144] As mentioned above, even if θ1 and θ3 are determined, since θ2 is arbitrary, the shape of the meniscus lens 16 is infinite for any combination of θ1 and θ3. Therefore, when designing the meniscus lens 16, it is necessary to determine the optimal θ2.

[0145] The optimal θ2 can be determined by the following method. In the first surface 16a of the meniscus lens 16, the direction of light propagation is deflected by θ2 - θ1. Let Δθ 21 The deflection angle Δθ is defined as θ2 - θ1. 21 Similarly, the deflection angle Δθ in the second surface 16b of the meniscus lens 16 is... 32 Defined as Δθ 32 =θ3-θ2. According to Figure 1 and Figure 4 The relationship in equation (15) holds true.

[0146] θ3 = θ1 + Δθ 21 +Δθ 32 (15)

[0147] Equation (15) indicates that the light diffused to θ1 by the diffuser element 14 is further extended by Δθ in the first surface 16a of the meniscus lens 16. 21 Δθ is further extended in the second surface 16b of the meniscus lens 16. 32 .

[0148] The amount of deflection in the divergence angle θ3 of the lighting device 10 in the diffusion element 14 and the first surface 16a and the second surface 16b of the meniscus lens 16 is defined as the contribution rate of each element by the following equations (16) to (18).

[0149] η1=θ1 / θ3 (16)

[0150] η 21 =Δθ 21 / θ3 (17)

[0151] η 32 =Δθ 32 / θ3 (18)

[0152] Clearly define η1 and η 21 and η 32 The sum is 1. Furthermore, these contribution rates do not change even if θ3 varies. Setting θ3 constant, through various η1, η... 21 η 32 The light emission efficiency of the lighting device 10 is calculated by combining the values ​​of light energy emitted from the light source 12 (e.g., 1). Light emission efficiency represents the light energy emitted from the lighting device 10 through the meniscus lens 16, with the light energy emanating from the light source 12 set to 1. This light energy is not only measured in a specific direction (θ3), but is obtained by integrating the light energy emitted in all directions.

[0153] Figure 8 An example showing the calculated light emission efficiency of the lighting device 10. Figure 8 In the chart, the vertical axis represents light emission efficiency, and the horizontal axis represents η. 21 / η 32 At θ 1max =40°, θ 3max When η = 90°, for various η 21 and η 32 Calculate the light emission efficiency. In this example, η1 = 40 / 90 = 0.44, η 21 +η 32 =0.56.

[0154] Depend on Figure 8 It can be seen that, with η 21 / η 32 As η increases, light emission efficiency rises. 21 / η 32 It reaches its maximum at approximately 0.74. Furthermore, in this calculation example, the refractive index of the meniscus lens 16 is 1.586, and the distribution of the emitted light is uniform (where F(θ3) = constant).

[0155] Additionally, in η 21 / η 32 When the value is greater than 0.74, the light emission efficiency is zero. This means that the tilt angle of the first surface of the meniscus lens is greater than 90°, making the lens difficult to manufacture and therefore impossible to achieve.

[0156] Figure 9Another example showing the calculated light emission efficiency of the lighting device 10. Here, in θ 1max =40°, θ 3max When η = 70°, for various η 21 and η 32 Calculate the light emission efficiency. In this example, η1 = 40 / 70 = 0.57, η 21 +η 32 =0.43.

[0157] Figure 9 The example shown is the same as Figure 8 Compared to the example shown, the deflection angle is smaller in meniscus lens 16. Figure 9 As shown in the example, with η 21 / η 32 As η increases, light emission efficiency rises. 21 / η 32 =1 takes the maximum value, and decreases again if it exceeds 1. and Figure 8 The examples shown are different, in Figure 9 In the example shown, since the tilt angle of the first surface 16a of the meniscus lens 16 will not exceed 90°, it is possible to achieve η 21 / η 32 The meniscus lens 16 was fabricated over a large area.

[0158] The light emission efficiency of the lighting device 10 can also be calculated in the same way for other combinations of θ1, θ2, and θ3, provided that the condition for maximizing the light emission efficiency is found. Then we can know η 21 ≦η 32 (19).

[0159] The equality in equation (19) holds when the tilt angle of the first surface 16a of the meniscus lens 16 is less than 90°. Otherwise, it means that within the range where the tilt angle of the first surface 16a of the meniscus lens 16 does not exceed 90°, η is maximized as much as possible. 21 The efficiency of time radiation increases.

[0160] If expressed in terms of angle (19), then

[0161] Δθ 21 / θ3≦Δθ 32 / θ3 (20)

[0162] or

[0163] θ2-θ1≦θ3-θ2 (twenty one)

[0164] These are the optimal conditions.

[0165] If we refer to equations (20) and (21), we can determine the θ2 with the highest light emission efficiency for different θ1 and θ3. For example, when θ1 = 40° and θ3 = 90°, according to... Figure 8 , in η 21 / η 32 When the light emission efficiency is 0.74, the light emission efficiency of the lighting device 10 reaches its maximum.

[0166] η 21 =Δθ 21 / θ3=(θ2-θ1) / θ3 (twenty two)

[0167] η 32 =Δθ 32 / θ3=(θ3-θ2) / θ3 (twenty three)

[0168] The relationship is used to calculate θ2, which is θ2 = 61.26°. Additionally, when θ1 = 40° and θ3 = 70°, according to... Figure 9 , in η 21 / η 32 When θ = 1, the light emission efficiency of the lighting device 10 becomes the maximum. If we calculate θ2 at this time, it is θ2 = 55°.

[0169] Figures 10-14 θ represents the maximum light emission efficiency of the lighting device 10. 1max θ 2max θ3 1max The result of the calculation based on the combination of . Figure 10 Indicates at θ 3max When θ = 90°, 1max Changes in contribution rate during changes. Figure 11 Indicates at θ 3max When θ = 85°, 1max Changes in contribution rate during changes. Figure 12 Indicates at θ 3max When θ = 80°, 1max Changes in contribution rate during changes. Figure 13 Indicates at θ 3max When θ = 75°, 1max Changes in contribution rate during changes. Figure 14 Indicates at θ 3max When θ = 70°, 1max The change in contribution rate when the change occurs. Furthermore, it is important to note that... Figure 13 and Figure 14 In, η 21 and η 32 The curves overlap, making them indistinguishable when visually identified.

[0170] Depend on Figure 10 It can be seen that at θ 3max When θ = 90°, if θ 1max When it increases, then η 21 With η 32 The inconsistency arises because the tilt angle of the first surface of the meniscus lens 16 exceeds 90°, failing to satisfy η. 21 =η 32 The conditions. Additionally, by Figure 11 It can be seen that at θ 3max When θ = 85°, if θ 1max If it increases, then η 21 With η 32 They also become inconsistent, but the difference is less than Figure 10 θ 3max =90°. Additionally, from Figures 12-14 It can be seen that at θ 3max When θ = 80°, 75°, and 70°, 1max Within roughly the entire range, it becomes η 21 =η 32 .

[0171] Figure 15 exist Figures 10-14 Under various conditions, the light emission efficiency of the lighting device 10 is represented by contour lines. Figure 15 It can be seen that, with θ 3max As the value increases, the light emission efficiency decreases, and at the same time, the light emission efficiency becomes the maximum value for θ. 1max Increase. For example, θ 3max When θ is 90°, 1max At 40°, the radiometric efficiency reaches its maximum (approximately 0.78), θ 3max When θ is 70°, 1max The radioactivity is highest around 30° (approximately 0.81).

[0172] according to Figure 15 The following information is available.

[0173] (1) At θ 1max =27°~58° and θ 3max Within the range of 70° to 90°, the light emission efficiency is above 0.75.

[0174] (2) At θ 1max =29°~54° and θ 3max Within the range of 70° to 90°, the light emission efficiency is above 0.76.

[0175] (3) At θ 1max =38°~43° and θ 3maxWithin the range of 70° to 90°, the light emission efficiency is above 0.78.

[0176] (4) At θ 1max =32°~42° and θ 3max Within the range of 74° to 84°, the light emission efficiency is above 0.79.

[0177] (5) At θ 1max =30°~38° and θ 3max Within the range of 70° to 78°, the light emission efficiency is above 0.80.

[0178] On the other hand, as mentioned above, when the light is spread to more than 140° (70°≦θ) 3max When ), there exists a θ2 where the light emission efficiency is the maximum, and this optimal θ2 is determined by the above equation (19) or equation (21).

[0179] Furthermore, regarding the light distribution of the lighting device 10 (also known as the angular distribution of light intensity or simply the light intensity distribution), the CV value (coefficient of variation) is preferably 0.05 or less, more preferably 0.04 or less, and particularly preferably 0.035 or less, within the range of -70°≦θ3≦70° or -80°≦θ3≦80°.

[0180] Based on the above embodiments of the present invention, the light source 12, the diffusion element 14, and the lens group 16 were designed, and simulations were performed to determine the light distribution characteristics obtained as an illumination device 10. The simulations were performed using OpticsStudio 5 Ver20.1 manufactured by Zemax.

[0181] As light source 12, a Vixar NIR-VCSEL (Part Number: V0081) is used. This light source emits near-infrared light with a dominant wavelength of 940nm. In addition, this light source is an array of multiple light-emitting regions arranged in a hexagonal close arrangement, which is a collection of a total of 281 VCSEL light-emitting parts, and the size of the light-emitting part (light-emitting surface) is approximately 1.0mm × 1.0mm.

[0182] Figure 16 This represents the light intensity distribution emitted from the light source used in the simulation. The light intensity distribution is approximately axisymmetric, with a full width at half maximum (FWHM) of 18°. The light intensity is lower near the optical axis (radiation angle = 0°), and a roughly annular distribution representing the maximum light intensity distribution is shown at a specified emission angle.

[0183] As the diffusion element 14, a plate-shaped microlens array with multiple microlenses formed on one side is used. Figure 17This is a top view of the 0.25mm × 0.25mm range of the microlens array used in the simulation. Figure 18 yes Figure 17 A partial cross-sectional view of the microlens array shown.

[0184] The microlens array is a plate with a main surface of 1 mm × 1 mm and a thickness of 0.4 mm, with multiple convex microlenses formed on one side of the main surface. The average spacing of the microlens array is about 24 μm, and they are randomly formed. The microlenses are axially symmetric convex surfaces, and their basic shape is represented by the following equation (22).

[0185] [Formula 1]

[0186] Where C = 0.010133, K = -0.7, a2 = 28.95186, a4 = 123969.3, a6 = 0, r is the distance from the axis of symmetry [mm], and Z represents the Sag quantity [mm].

[0187] Furthermore, each microlens is formed in such a way that it randomly varies by ±9μm in the direction parallel to the main surface and by ±1μm in the direction perpendicular to the main surface.

[0188] Such a microlens array, for example, is prepared by injection molding a mold with the lens shape of the microlens array reversed on one side of a parallel flat transparent substrate of 2mm × 2mm × t × 0.4mm (t is the thickness) using resin. The resin, for example, can be a photocurable resin (CELLOXIDE 2021P manufactured by DAICL Corporation (main component: 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate) to form a specified shape.

[0189] A meniscus lens is used as lens group 16. Figure 19 This is a schematic cross-sectional view of the meniscus lens 16 used in the simulation. As an axisymmetric lens, the meniscus lens 16 is designed with the distance from the axis defined as r and the Sag value defined as Z. Following the design steps of the lens surface constructed based on calculations of θ1, θ2, and θ3, the (r, Z) data sets of the first surface (light incident surface) 16a and the second surface (light exit surface) 16b are obtained. Table 1 below shows the (r, Z) data of the first surface 16a and the second surface 16b of the meniscus lens 16.

[0190] [Table 1]

[0191] The actual meniscus lens 16 is manufactured by machining polycarbonate (TAKIRON, model PCET1600). Using the method described in the above embodiment, the Sag amount (Z value) relative to the distance r from the optical axis (Z-axis) is calculated, and this numerical data is input into a machining apparatus for processing.

[0192] Figure 20 This describes the configuration of the lighting device 10 used for simulation. For example... Figure 20 The light source 12, the diffusion element (microlens array) 14, and the lens group (meniscus lens) 16 are configured as shown. The axis (Z-axis) that is symmetrical about the light intensity distribution of the light source 12 is set as the optical axis of the light source 12.

[0193] For a diffuser element 14 with multiple microlenses formed on one surface, the surface with the microlenses is designated as the first surface 14a, and the flat surface on the opposite side is designated as the second surface 14b. The diffuser element 14 is positioned such that the first surface 14a of the diffuser element 14 faces the emitting surface 12a of the light source 12, and the optical axis of the light source 12 is perpendicular to the second surface 14b of the diffuser element 14 and passes through the geometric center of the main surface of the diffuser element 14. Furthermore, the meniscus lens 16 is positioned such that the first surface 16a of the meniscus lens 16 faces the diffuser element 14, and the optical axis of the meniscus lens 16 is aligned with the optical axis of the light source 12. The optical axis of the light source 12 is designated as the Z direction, and the direction emitted from the light source 12 is designated as positive.

[0194] Furthermore, regarding the spacing in the Z direction of each component, the distance between the emitting surface 12a of the light source 12 and the second surface 14b of the diffuser element 14 is set as d1, and the distance between the second surface 14b of the diffuser element 14 and the second surface 16b of the meniscus lens 16 is set as d2. By varying d1 within the range of 0.2mm to 1.5mm and d2 within the range of 1.5mm to 5.0mm, θ... 3max Fine adjustments are made in a way that increases the value while decreasing the deviation in light distribution (CV value). As an appropriate value, d1 is approximately 0.7 mm and d2 is approximately 3.5 mm.

[0195] In the simulation, firstly, with Figure 16 The light distribution (light intensity distribution) shown makes 1×10 6 A ray of light is emitted from the emitting surface 12a of the light source 12. The light distribution (light intensity distribution) of the light emitted from the diffuser element 14 is determined. Next, the size and arrangement of the diffuser element 14 are adjusted to achieve a light distribution of 5 × 10⁻⁶. 7 A light ray is emitted, and the incident light that enters the lens group (meniscus) 16 and the light trail of the emitted light from the lens group 16 are determined, and the light intensity distribution of the illumination device 10 is determined.

[0196] Then, prepare the aforementioned light source 12, diffusion element 14 and meniscus lens 16, and manufacture the actual lighting device 10. Figure 21 This describes a measurement system 100 for measuring the light distribution of an illumination device 10. The measurement system 100 includes a photodetector 106 comprising an aperture 102 and a photoelectric element 104. The illumination device 10 is pre-fixed and made to emit light; the photodetector 106 scans the area around the illumination device 10, for example, with the principal point of a lens group 16 such as a meniscus lens as the center, thereby enabling the measurement of the dependence of the light intensity on the angle θ3.

[0197] Figure 22 This section represents the light intensity distribution of the lighting device as determined by simulation and the actual measured light intensity distribution. The simulated light intensity distribution is represented by a dashed line. The actual measured light intensity distribution (measured value) is represented by a circle.

[0198] Several differences can be observed between the measured values ​​and the simulation, but θ 3max With a light intensity of 94° (the angle corresponding to a light intensity of 0.5 (the angle corresponding to half the value)), for example, compared to the technology described in Patent Document 1 above, it becomes an illumination device that provides the same light distribution with a wider angle.

[0199] The CV value (coefficient of variation), which represents the deviation of light distribution, is 0.028 (simulation) and 0.0329 (measured value) in the range of -70°≦θ3≦70°, and 0.0344 (simulation) and 0.0339 (measured value) in the range of -80°≦θ3≦80°.

[0200] The above explains how to set the value of |θ3| from 0° to the maximum value θ. 3max The angle allows for the design of illumination within a region centered on the optical axis Ax, and provides methods and examples. Regarding the value of |θ3|, the shape of the meniscus lens 16 can be designed, for example, to emit light within the range of 40°–90° or 30°–80°. For example, it can be set to have… Figure 23 The illumination device shown has a light distribution pattern. Such a light distribution is sometimes referred to as a medium-low, annular, or ring-shaped light distribution. Additionally, because its shape is reminiscent of a bat's outstretched wings, it is sometimes called a Bat-Wing.

[0201] Figure 24 Indicates having Figure 23 The illustrated illumination device is mounted on a traveling robot 200. The traveling robot 200 is, for example, an automated cleaning robot, and is equipped with the illumination device 10 with the optical axis Ax perpendicular to the traveling surface 202.

[0202] In the environmental recognition of the driving robot 200, sensing of the vicinity of the driving surface 202 is necessary, but there are also situations where sensing of the upper space is not required. In such cases, the lighting device 10 is positioned at... Figure 23 The light distribution shown, which does not emit light for illumination near the optical axis Ax, can enhance the amount of light in the illumination area 204 to the side of the optical axis Ax, thus improving the efficiency of light utilization.

[0203] As mentioned above, there are sometimes requirements for lighting devices that do not emit light or emit very little light near the optical axis Ax. In such cases, by setting the conditions of the microlens array constituting the diffusion element 14 to specific conditions, it is possible to achieve the required characteristics of such lighting devices.

[0204] Figure 25 An example of a cross-section representing a portion of the microlens array 114. The highest point of the microlens 122 is designated as vertex 122a, and the portion including vertex 122a and near the vertex is designated as top 122b. Figure 25 The image shows a convex microlens 122, but the same applies to a concave microlens, where the lowest point of the microlens can be taken as the vertex.

[0205] When light from the light source is incident on Figure 25 When a diffusion element consisting of a microlens array 114 of the shape shown is used, a ring-shaped light distribution with relatively small light intensity near the optical axis of the light source can be obtained.

[0206] Figure 26 yes Figure 25 A schematic enlarged view of the microlens 122 is shown. The straight line passing through the vertex 122a of the microlens 122 is defined as the optical axis 122c of the microlens. The top 122b of the microlens 122 is sharp, and the slope from the vertex 122a to both sides of the microlens 122 is steep at the top 122b. Light rays L incident approximately parallel to the microlens 122 are deflected at a larger angle due to this steep slope, resulting in less light near the optical axis 122c and a smaller light intensity. When the top 122b of the microlens 122 is not sharp (including when it has a locally nearly flat surface (a surface perpendicular to the optical axis 122c)), a portion of the light incident on the microlens 122 is not significantly deflected before exiting, and the reduction in light intensity near the optical axis 122c is less pronounced.

[0207] As for the cross-sectional shape of such a specific microlens 122, the inclination of the surface can be changed drastically at the vertex 122a. When the surface is expressed as a function of the distance r from the optical axis 122c and the Sag quantity Z, the second differential coefficient of r with respect to the vertex 122a can also be discontinuous. Figure 27Examples of the cross-sectional shape of the microlens 122 are shown in (a) to (g). These shapes can also be named according to the cross-sectional shape of a cutting tool, such as a knife. Figure 27 (a) Represents a microlens 122 with a convex shape. Figure 27 (b) Represents a planar microlens 122. Figure 27 (c) represents a hollow microlens 122. Figure 27 (d) represents a microlens 122 with a symmetrical shape consisting of a convex surface and a plane. Figure 27 (e) represents a microlens 122 with an asymmetric shape consisting of a convex surface and a plane. Figure 27 (f) represents a microlens 122 with an asymmetric shape composed of several planes. Figure 27 (g) represents a microlens 122 with a symmetrical shape consisting of several planes.

[0208] Next, we specifically consider the case where the intensity F(θ3) of the light emitted from the lighting device 10 per unit solid angle increases within a certain range as |θ3| increases. |θ3| represents the absolute value of θ3. Unless otherwise specified, all symbols represent the same or corresponding parameters or physical quantities as described above.

[0209] As a function of the increase of F(θ3) with the increase of |θ3|, it is not limited to this, but equations (3A), (3B), or the generalized equation (3C) can be shown. In addition, the case of the light intensity increasing with the increase of |θ3| is shown because such a light intensity distribution is generally required to improve the performance of the sensor. In addition, for example, the shape of the meniscus lens can also be designed as a function of the decrease of light intensity with the increase of |θ3|, so that light is emitted only within a specified angular range.

[0210] The example (3C), etc., representing F(θ3), is because there exist cases where the emission pattern from the light source (including the emission pattern of the light source defined in simulations, etc.) is a function of the cosine function cosθ containing the emission angle θ, or where the illuminance decreases as it moves away from the optical axis, and cosθ is related to the emission pattern. 4 Since θ is proportional (cosine 4th power law), using a cosine function containing θ is similar when expressing the relationship between the radiation angle and the changing light intensity.

[0211] Furthermore, in cases where a lighting device is required for a specific purpose, the direction of light is usually such that F(θ3) increases within a certain range as the radiation angle θ3 increases. Additionally, sometimes the light intensity is specified as discrete values ​​corresponding to the radiation angle θ3. In this case, the discrete (scattered) data can also be expressed as a continuous function {cos(α×θ3)}. -n Perform fitting (n and α are positive real numbers).

[0212] Furthermore, in the lighting device 10, the intensity F(θ3) of the light emitted per unit solid angle from the lighting device 10 can also be {cos(α×θ3)} within the range of -80°≦θ3≦80°. -n ≦F(θ3)≦{cos(β×θ3)} -m And {cos(α×θ3)} -n <{cos(β×θ3)} -m n and m are positive real numbers, and α and β are positive real numbers. Additionally, in {cos(α×θ³)}... -n ≦F(θ3)≦{cos(β×θ3)} -m And {cos(α×θ3)} -n <{cos(β×θ3)} -m In this case, it can also be 1≦n, m≦5 and 0.1≦α, β≦2.5. Additionally, in the case of -85°≦θ3≦85°, it can also be {cos(α×θ3)}. -n ≦F(θ3)≦{cos(β×θ3)} -m And {cos(α×θ3)} -n <{cos(β×θ3)} -m n and m are positive real numbers, and α and β are positive real numbers. Additionally, in {cos(α×θ³)}... -n ≦F(θ3)≦{cos(β×θ3)} -m And {cos(α×θ3)} -n <{cos(β×θ3)} -m In this context, it can also be 1≦n, m≦5 and 0.1≦α, β≦2.5. Furthermore, the above function can also be standardized such that the light intensity F(0) = 1 when θ3 = 0, or such that the minimum value of F(θ3) within a specific range of θ3 equals 1. For lighting devices circulating in the market, after passing through... Figure 22 After measuring the light intensity using the method shown, it can also be standardized by making the light intensity F(0) = 0 when θ3 = 0, or by taking the minimum value of F(θ3) within a specific range of θ3 as 1, and then comparing and contrasting (the same applies below).

[0213] Furthermore, in the lighting device 10, the intensity F(θ3) of the light emitted from the lighting device 10 per unit solid angle can be (cosθ3) as α=β=1 in the range of -80°≦θ3≦80°. -0.1 ≦F(θ3)≦(cosθ3) -1.2 Alternatively, (cosθ3) is also preferred. -0.2 ≦F(θ3)≦(cosθ3) -1Additionally, in the range -80°≦θ³≦80°, α=β=1 could also be (cosθ³). -0.1 ≦F(θ3)≦(cosθ3) -1.2 Alternatively, (cosθ3) is also preferred. -0.2 ≦F(θ3)≦(cosθ3) -1 .

[0214] In particular, as a portable lighting device for use in portable computers and terminals such as smartphones, the intensity F(θ3) of the light emitted from the lighting device 10 per unit solid angle can also be {cos(α×θ3)} within the range of -80°≦θ3≦80°. -0.1 ≦F(θ3)≦{cos(β×θ3)} -7 (Where 0 < α, β < 1), α and β can also be defined as follows: within the angular range of θ3 (70° to 90°), F(θ3) will not increase drastically. The angle θ within the angular range of θ3 (70° to 90°)... 0 3 (for example, it could be θ) 0 In the range of 3 = 70°, 80°, 90°, it can also be determined as F(θ). 0 3) Values ​​within the range of 1 to 10 (excluding 1). Preferably, α and β can also be determined as F(θ). 0 3) Values ​​within the range of 1.1 to 10. Additionally, within the range of -80°≦θ³≦80°, it can also be {cos(0.9×θ³)}. -0.1 ≦F(θ3)≦{cos(0.415×θ3)} -10 It can also be {cos(0.4×θ³)} -1.5 ≦F(θ3)≦{cos(0.465×θ3)} -7.5 In the case of the above-described uses or applications, the ratio of light intensity in the central portion to the peripheral portion of the surface illuminated by the lighting device is expected to be approximately 1:10 to 1:5. Furthermore, as mentioned above, it is common to use a light distribution pattern that includes a cosine function.

[0215] Figure 28 The diagram shows that, for 0 < θ3 (note that only the region 0 < θ3 is shown due to symmetry about θ = 0), F(θ3) = {cos(0.9 × θ3)}. -0.1 F(θ3) = {cos(0.415×θ3)} -10 The graphs of the functions and the graphs of several functions contained within these functions. Figure 29 The diagram shows that F(θ3) = {cos(0.4 × θ3)}. -1.5F(θ3) = {cos(0.465 × θ3)} -7.5 The graphs of the functions and the graphs of several functions contained within these functions.

[0216] As an example, let F(θ3) = (cosθ3) -3 Let's take an example. F(θ3), as explained above, is represented by equation (10) or equation (13). In F(θ3) = (cosθ3) -3 When, equation (13) is as shown in equation (23).

[0217] (cosθ3) -3 =F(θ1) Δθ1 sinθ1 / (Δθ3 sinθ3) (twenty three)

[0218] Furthermore, if F(θ1) is constant and independent of θ1, then the following equation is obtained from equation (23).

[0219] (Δθ3) sinθ3)(cosθ3) -3 =C Δθ1 sinθ1 (twenty four)

[0220] Where C is a constant.

[0221] If we compare equation (24) with equation (14), we have the following: multiplying the left side by (cosθ3) -3 Although the terms differ, θ3 corresponding to θ1 can be calculated sequentially using the same method described in paragraph 0068. Note that (cosθ3) -3 In θ ３ =90° becomes infinitely large. To make the divergence angle greater than 180°, as F(θ3), choose a light intensity distribution close to that of the target, and even if θ ３ Functions that do not diverge even at a angle of 90°. For example, F(θ3)={cos(α×θ3)} -3 (25) Based on the above, θ1 and its corresponding θ3 can be calculated. Similar to the case where F(θ3) is constant, since θ2 is arbitrary, it needs to be optimized. The optimal θ2 can be calculated in the same way as when F(θ3) is constant.

[0222] Figure 30 The light intensity distribution is represented by equation (26).

[0223] F(θ3)={cos(0.512×θ3)} -3 (26)

[0224] Furthermore, at θ ３ When α = 90°, the value of α is determined by F(90) = 3.

[0225] Figure 31 Another example showing the calculated light emission efficiency of the lighting device 10. Figure 31 In the chart, the vertical axis represents light emission efficiency, and the horizontal axis represents η. 21 / η 32 At θ 1max =40° and θ 3max When η = 90°, for various η 21 and η 32 Calculate the light emission efficiency. In this example, η1 = 40 / 90 = 0.44, η 21 +η 32 =0.56.

[0226] Depend on Figure 31 It can be seen that, with η 21 / η 32 As η increases, light emission efficiency rises. 21 / η 32 It reaches its maximum at approximately 0.73. Furthermore, in this calculation example, the refractive index of the meniscus lens 16 is 1.586, and the light distribution of the emitted light follows equation (26). Additionally, at η... 21 / η 32 When the value is greater than 0.73, the light emission efficiency is zero. This means that the tilt angle of the first surface corresponding to the incident surface of the meniscus lens is greater than 90°, making the lens difficult to manufacture and thus an unachievable range.

[0227] Figure 32 Another example showing the calculated light emission efficiency of the lighting device 10. Here, at θ 1max =40°, θ 3max When η = 70°, for various η 21 and η 32 Calculate the light emission efficiency. In this example, η1 = 40 / 70 = 0.57, η 21 +η 32 =0.43.

[0228] Figure 32 The example shown is the same as Figure 31 Compared to the example shown, the deflection angle is smaller in meniscus lens 16. Figure 31 As shown in the example, with η 21 / η 32As η increases, light emission efficiency rises. 21 / η 32 =1 takes the maximum value, and decreases again if it exceeds 1. and Figure 29 The examples shown are different, in Figure 32 In the example conditions shown, the maximum light emission efficiency is relatively small, but since the tilt angle of the first surface 16a of the meniscus lens 16 will not exceed 90°, it is possible to achieve a higher maximum light emission efficiency (η). 21 / η 32 The meniscus lens 16 was fabricated over a large area.

[0229] In other combinations of θ1, θ2, and θ3, the light emission efficiency of the lighting device 10 can also be calculated in the same way. If the condition for the light emission efficiency to be maximized is determined, it is as follows (27).

[0230] η 21 ≦η 32 (27)

[0231] The equality of equation (27) holds when the tilt angle of the first surface 16a of the meniscus lens 16 is less than 90°. Otherwise, it means that within the range where the tilt angle of the first surface 16a of the meniscus lens 16 does not exceed 90°, η is maximized as much as possible. 21 The efficiency of time radiation increases.

[0232] If expressed in terms of angle (27), then the following equations (28) or (29) can be derived.

[0233] Δθ 21 / θ3≦Δθ 32 / θ3 (28)

[0234] or

[0235] θ2-θ1≦θ3-θ2 (29)

[0236] These are the optimal conditions.

[0237] Based on equations (28) and (29), the θ2 with the highest light emission efficiency can be determined for different θ1 and θ3. For example, when θ1 = 40° and θ3 = 90°, according to... Figure 29 , in η 21 / η 32 When = 0.73, the light emission efficiency of the lighting device 10 reaches its maximum. According to the following relationship (22) and (23), η 21 =Δθ 21 / θ3=(θ2-θ1) / θ3 (twenty two) η 32 =Δθ 32 / θ3=(θ3-θ2) / θ3 (twenty three) Find θ2, then θ2 = 61.14°. Additionally, when θ1 = 40° and θ3 = 70°, according to... Figure 32 , in η 21 / η 32 When θ = 1, the light emission efficiency of the lighting device 10 becomes the maximum. If we calculate θ2 at this time, it is θ2 = 55°.

[0238] Figures 33-37 θ represents the maximum light emission efficiency of the lighting device 10. 1max θ 2max θ3 1max The result of the calculation based on the combination of . Figure 33 Indicates at θ 3max When θ = 90°, 1max Changes in contribution rate during changes. Figure 34 Indicates at θ 3max When θ = 85°, 1max Changes in contribution rate during changes. Figure 35 Indicates at θ 3max When θ = 80°, 1max Changes in contribution rate during changes. Figure 36 Indicates at θ 3max When θ = 75°, 1max Changes in contribution rate during changes. Figure 37 Indicates at θ 3max When θ = 70°, 1max The change in contribution rate when the change occurs. Furthermore, it is important to note that... Figure 34 and Figure 35 In, η 21 and η 32 The curves overlap, making them indistinguishable when visually identified.

[0239] Depend on Figure 33 It can be seen that at θ 3max When θ = 90°, if θ 1max If it increases, then η 21 With η 32 The inconsistency arises because the tilt angle of the first surface of the meniscus lens 16 exceeds 90°, failing to satisfy η. 21 =η 32 The conditions. Additionally, by Figure 34 It can be seen that at θ 3max When θ = 85°, if θ 1max If it increases, then η 21 With η 32 They also become inconsistent, but the difference is less than Figure 10 θ3max =90°. Additionally, from Figures 35-37 It can be seen that at θ 3max When θ = 80°, 75°, and 70°, 1max Within roughly the entire range, it becomes η 21 =η 32 .

[0240] Figure 38 exist Figures 33-37 Under various conditions, the light emission efficiency of the lighting device 10 is represented by contour lines. Figure 38 It can be seen that, with θ 3max As the value increases, the light emission efficiency decreases, and at the same time, the light emission efficiency becomes the maximum value for θ. 1max Increase. For example, θ 3max When θ is 90°, 1max At θ = 40°, the radiometric efficiency becomes maximum (approximately 0.77), 3max When θ is 70°, 1max The radioactivity is highest around 30° (approximately 0.81).

[0241] according to Figure 38 The following information is available.

[0242] (1) At θ 1max =30°~58° and θ 3max Within the range of 70° to 90°, the light emission efficiency is above 0.75.

[0243] (2) At θ 1max =34°~52° and θ 3max Within the range of 70° to 90°, the light emission efficiency is above 0.76.

[0244] (3) At θ 1max =40°~43° and θ 3max Within the range of 70° to 90°, the light emission efficiency is above 0.77.

[0245] (4) At θ 1max =30°~42° and θ 3max Within the range of 70° to 80°, the light emission efficiency is above 0.79.

[0246] (5) At θ 1max =30°~38° and θ 3max Within the range of 70° to 75°, the light emission efficiency is above 0.80.

[0247] On the other hand, as mentioned above, when the light is spread to more than 140° (70°≦θ) 3maxWhen ), there exists a maximum light emission efficiency θ2, which can also be determined by the above equation (A5) or equation (29).

[0248] The following Table 2 shows the methods used for implementation. Figure 30 The data of (r, Z) for the first surface 16a and the second surface 16b of the meniscus lens 16 are used for light distribution. The meanings of r and Z are based on Equation (22). Figure 39 The diagram shows the representation of meniscus lens 16 in r-Z coordinates. The vertex of the second surface 16b is set to (r, Z) = (0, 0). The shapes of the meniscus lenses listed in Table 2 are based on... Figure 30 Using the light distribution as the target value, at θ 3max =90°, θ 1max The shape was designed using the above method under a 40° angle. With the same configuration as when the light intensity is constant, and using the same components for the light source and diffuser, a meniscus lens was actually fabricated and its light distribution measured, with only the lens changed to the data in Table 2. Figure 40 The measured light distribution is shown in the figure. Furthermore, the dashed line in the figure represents the light distribution as the target. Although some differences can be observed between the measured values ​​and the simulation, θ3... 0 3 is 85° (the angle corresponding to a light intensity of 0.5 (the angle corresponding to half the value)), which, for example, compared to the technology described in Patent Document 1 above, becomes an illumination device that provides the same light distribution with a wider angle.

[0249] [Table 2]

[0250] The present invention has been described above based on embodiments. Those skilled in the art should understand that these embodiments are merely illustrative, and various modifications can be made to the combination of the constituent elements and processing procedures, and these modifications are also within the scope of the present invention.

[0251] [Industrial Availability]

[0252] This invention can be used in lighting devices that use lasers as a light source.

[0253] [Explanation of reference numerals in the attached figures]

[0254] 10 Illumination device, 12 Light source, 14 Diffuser element, 16 Lens group, 22, 122 Microlenses, 100 Measurement system, 104 Photoelectric element, 106 Photodetector, 114 Microlens array, 200 Driving robot.

Claims

1. A lighting device comprising: A light source that emits parallel or divergent light; A diffusion element that receives light emitted from the light source and emits light at a diffusion angle of 50° or more and 110° or less, wherein the diffusion element is a microlens array having multiple microlenses; as well as The lens group, having negative optical power, receives light from the diffuser element on the first surface and emits light from the second surface at a beam angle of 140° or greater. This lens group is a single, axisymmetric meniscus lens. The lighting device is characterized by, When the angle of the emitted light from the diffuser relative to the optical axis is set as θ1, the angle of the emitted light from the first surface of the lens group relative to the optical axis is set as θ2, and the angle of the emitted light from the second surface of the lens group relative to the optical axis is set as θ3, the following conditions are met: θ2-θ1≦θ3-θ2, Within the range of -70°≦θ3≦70°, the CV value of the light distribution of the light intensity of the lighting device is less than 0.05, wherein the CV value is obtained by dividing the average value of the light intensity of the lighting device within the range of θ3 by the standard deviation of the light intensity of the lighting device.

2. The lighting device as claimed in claim 1, characterized in that, Set the maximum value of θ1 to θ 1max Set the maximum value of θ3 as θ 3max At θ 1max =27°~58° and θ 3max Within the range of 70° to 90°, the light emission efficiency is above 0.

75.

3. A sensor device, It includes the lighting device as described in claim 1 or 2.

4. A type of vehicle, It includes the sensor device as described in claim 3.

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