Lighting device

Abstract

Provided is an illumination device having a sufficiently large irradiation angle and a uniform light intensity within a predetermined range even when a light source using light having a small external expansion angle such as laser light or light close to parallel light is used. The illumination device includes a light source having at least one light emitting unit; a first optical element that receives light emitted from the light source and increases the emission angle of the light; and a second optical element that receives light emitted from the first optical element and further increases the irradiation angle of the light.

Description

Technical Field

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

[0002] In the prior art, there are known lighting devices that aim to improve the uniformity of brightness (light intensity) within a certain range by increasing the illumination angle of light emitted by a light source such as an LED, for example, the devices disclosed in Patent Documents 1 and 2. All such prior art devices include a light source such as an LED and a lens for adjusting its orientation, wherein the light emission direction is expanded outward by refracting the light emitted by the LED through the lens.

[0003] The lens described above is preferably a concave-convex lens, having a first surface for receiving light emitted from a light source and a second surface for emitting light. The first surface defines a cavity for accommodating an LED element. The lens has an axis (lens optical axis) and is an axisymmetric lens, substantially coaxial with the LED optical axis. On the second surface, a central region containing the lens optical axis is concave compared to other surface regions.

[0004] However, while this technology can increase the illumination angle for light sources such as LEDs, which have a large illumination angle, it is difficult to apply to light sources such as lasers, which have a small illumination angle, and thus it is difficult to increase the illumination angle.

[0005] Furthermore, the same problem arises when using non-laser sources, such as collimated light sources that emit parallel light with a small beam diameter using collimating lenses. Specifically, since the light emitted by the source only has a component parallel to the optical axis, it is difficult to sufficiently increase the illumination angle of the emitted light.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2019-220266

[0009] Patent Document 2: Japanese Patent Application Publication No. 2009-510731 Summary of the Invention

[0010] The problem to be solved by this invention

[0011] In view of the above-mentioned problems of the prior art, the present invention aims to provide an illumination device that has a sufficiently large illumination angle and uniform light intensity within a predetermined range even when using light with a small outward expansion angle, such as laser light or light sources similar to parallel light.

[0012] Problem-solving methods

[0013] To solve the above problems, the lighting device of the present invention includes: a light source having at least one light-emitting unit; a first optical element that receives light emitted from the light source and emits it after increasing its emission angle; and a second optical element that receives light emitted from the first optical element and emits it after further increasing its illumination angle.

[0014] Invention Effects

[0015] According to the present invention, an illumination device is provided that has a sufficiently large illumination angle and uniform light intensity within a predetermined range even when using light with a small outward expansion angle, such as laser light, or a light source similar to parallel light. Attached Figure Description

[0016] Figure 1A This is an optical structure diagram of the overall structure of a lighting device 100 according to one embodiment.

[0017] Figure 1B The light intensity characteristics of the emitted light from the lighting device 100 are shown.

[0018] Figure 2 This is a schematic diagram illustrating a structural example of a microlens array 10M used as the first optical element 10.

[0019] Figure 3A This is an example of a top view of a 10M microlens array.

[0020] Figure 3B This is a schematic diagram of an imaginary circle.

[0021] Figure 4 Let d be the distance from the center C of the imaginary circle to the center of the top surface (lens surface) of each microlens ML (d = 0 ~ R). H The graph is plotted with the horizontal axis as the x-axis and the vertical axis as the sag of the microlens ML, z.

[0022] Figure 5 This is a cross-sectional view of the microlens ML cut along a plane containing the axis of symmetry.

[0023] Figure 6 To indicate Figure 4 The graph shows the relationship between distance d and a specific tilt angle β, using the microlens shown as an example.

[0024] Figure 7 A graph illustrating the relationship between a specific tilt angle adjustment coefficient k and a specific tilt angle β.

[0025] Figure 8 To indicate Figure 4 and Figure 6 A graph illustrating the relationship between the distance d of the microlens ML and the adjustment coefficient k for a specific tilt angle.

[0026] Figure 9 A graph illustrating an example of the relationship between a specific tilt angle β of a microlens ML and the distance d from the center C.

[0027] Figure 10A The diagram shows a structural example of the first optical element 10.

[0028] Figure 10B The diagram shows a structural example of the first optical element 10.

[0029] Figure 10C The diagram shows a structural example of the first optical element 10.

[0030] Figure 10D The diagram shows a structural example of the first optical element 10.

[0031] Figure 10E The diagram shows a structural example of the first optical element 10.

[0032] Figure 10F The diagram shows a structural example of the first optical element 10.

[0033] Figure 10G The diagram shows a structural example of the first optical element 10.

[0034] Figure 11A This is a schematic diagram illustrating the definition of the divergence angle θd.

[0035] Figure 11B A top view of an example microlens array with perturbations added to the microlens arrangement.

[0036] Figure 11C A top view of an example microlens array with perturbations added to the microlens arrangement.

[0037] Figure 11D A top view of an example microlens array with perturbations added to the microlens arrangement.

[0038] Figure 12 This is an explanatory diagram showing the distance L between the light source 1 and the first optical element 10.

[0039] Figure 13A The image shows the intensity distribution of the emitted light from the NIR-VCSEL used as light source 1 in Example 1.

[0040] Figure 13B The figures shown are the various values ​​used in Example 1.

[0041] Figure 14 This is a graph showing the relationship between distance d and the specific tilt angle adjustment coefficient k in Example 1.

[0042] Figure 15This is a schematic diagram of the microlens array in Example 1.

[0043] Figure 16 The image shows an example of a fisheye lens used as the second optical element 20 in Embodiment 1.

[0044] Figure 17 The simulation results for Example 1 are shown below.

[0045] Figure 18 The simulation results for Comparative Example 1 are shown below.

[0046] Figure Labels

[0047] 1. Light source; 10. First optical element; 20. Second optical element. Detailed Implementation

[0048] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the drawings, functionally identical elements are represented by the same numbers. Furthermore, although the drawings illustrate embodiments and exemplary implementations consistent with the principles of the present disclosure, they are for the purpose of understanding the disclosure and are not intended to be interpreted in a limiting manner. The descriptions in this specification are merely typical examples and do not limit the claims or application examples of the present disclosure at any level.

[0049] While this disclosure has been described in great detail to enable those skilled in the art to practice it, it should be understood that other implementations or methods may exist, and that modifications or substitutions of the composition or structure or various elements may be made without departing from the scope and spirit of the technical concept of this disclosure. Therefore, the following description should not be construed as limiting it thereto.

[0050] The following is for reference. Figure 1A and Figure 1B The following describes a lighting device according to one embodiment. Figure 1A This is an optical structure diagram of the overall structure of the lighting device in this embodiment. Figure 1B The image shows the luminous intensity characteristics of this lighting device. For example... Figure 1A As shown, the lighting device 100 is generally composed of a light source 1, a first optical element 10 and a second optical element 20.

[0051] Light source 1 is a light source that emits light with good directionality, such as a laser source. In addition to a laser source, light source 1 can also be composed of a light source such as an LED that emits light with poor directionality and a collimating lens that collimates the light into parallel light.

[0052] The first optical element 10 increases the illumination angle of the emitted light from the light source 1. The second optical element 20 further increases the illumination angle of the emitted light increased by the first optical element 10.

[0053] An example of the light intensity distribution of the lighting device 100 is shown below. Figure 1B .exist Figure 1B In the diagram, the horizontal axis represents the emission angle of light centered on the optical axis, and the vertical axis represents the light intensity when the maximum light intensity is set to 1.

[0054] The exit angle of light has the same meaning as the divergence angle and expansion angle of light emitted by a device, optical device, or lighting device. The magnitude of the exit angle is closely related to the size of the illumination range of the lighting device. In this specification, when measuring the light intensity distribution (light intensity distribution characteristics) of light emitted by a device, optical device, or lighting device, or when performing calculations through simulation, the light intensity per unit solid angle is obtained in a manner corresponding to the exit angle of light (the maximum light intensity value is set to 1).

[0055] like Figure 1B As shown, in the light intensity distribution characteristics of the lighting device 100 of this embodiment, the light intensity when the emission angle of the emitted light is ±90° is 0.5 or more, preferably 0.55 or more, and more preferably 0.6 or more. Furthermore, the absolute value of the emission angle at which the light intensity becomes 0.9 or more is 45° or less (-45° to 45°), preferably 50° or less, more preferably 55° or less, and particularly preferably 60° or less. Additionally, the light intensity distribution can be measured, for example, using an orientation measuring device IMS-5000 from Asahi Spectrophotometer Co., Ltd.

[0056] For the light source 1, a laser source with a relatively small illumination angle (outward expansion angle) is more advantageous in terms of the functionality of the lighting device 100 in this embodiment. When the light source 1 is a laser source, the laser source can be either a light-emitting array including multiple light-emitting units disposed in a predetermined area, or a single laser element including only one light-emitting unit.

[0057] When the light source 1 is a laser source, the laser source can be either a vertical cavity surface emitting laser (VCSEL) or a VCSEL array with effective light-emitting units arranged in two or three dimensions. In addition to a laser source, the light source 1 can also use LED elements or an LED array with effective light-emitting units arranged in two or three dimensions. Furthermore, besides electric field light sources such as laser sources or LEDs, temperature radiation light sources or discharge light sources can also be used. Temperature radiation light sources include incandescent bulbs and halogen bulbs, while representative discharge light sources include high-pressure mercury lamps, metal halide lamps, and fluorescent lamps. Regarding the illumination angle of the light emitted from the light source 1, the full width at half maximum (FWHM) in the light intensity distribution of the light source is 6°–40°, preferably 12°–30°, and more preferably 15°–24°.

[0058] The first optical element 10 has a first surface for light incident and a second surface for light emanating. The first optical element 10 may be, for example, a surface with the function of light diffusion, and may have a light homogenizing effect, or may include a homogenizer and a diffuser plate or diffuser element (diffusing function). The diffuser plate or diffuser element has the function of diffusing incident light at a certain angle by means of refraction or diffraction through minute irregularities or irregularities on its surface or interior. The second surface may be a surface similar to the first surface that also has a diffusion function, or it may be a surface that does not have a diffusion function. At least one of the first surface and the second surface of the first optical element 10 has a diffusion function.

[0059] The first optical element 10 may be, for example, a microlens array, a cylindrical lens array, a microprism array, a Fresnel lens array, etc. These arrays can be implemented by forming multiple microlenses, cylindrical lenses, microprisms, or Fresnel lenses on at least one of the first and second surfaces of the first optical element 10. Furthermore, multiple optical elements can be mixed and formed within a single first optical element 10.

[0060] Furthermore, microlenses or microprisms can be either concave or convex. They can be arranged according to a certain pattern or randomly distributed. Microlenses or microprisms can be a combination of different curvatures, shapes, angles, and sizes.

[0061] Furthermore, the first optical element 10 can be a frosted diffuser plate or the like, having a micro-uneven structure formed by roughening the surface of a substrate or support. The first optical element 10 can also have a linearly symmetrical or point-symmetrical structure relative to its center, but is not limited to these. In cases where multiple structures such as multiple lenses are formed, an asymmetrical structure may also be present.

[0062] An example of the structure of the microlens array 10M used as the first optical element 10 is shown below. Figure 2 (a) to Figure 2 (c) The microlens array 10M includes a substrate SB, which has a first surface S1 on which light is incident and on which a plurality of microlenses ML are arranged, and a second surface S2 on which light is emitted. The second surface S2 is planar, thereby making the microlens array 10M a generally planar element. Furthermore, in Figure 2 (a) to Figure 2 In (c), microlenses ML can be formed on both the first surface S1 and the second surface S2. In this case, since there are two surfaces that have the function of applying light, it is expected that the effect of increasing the illumination angle can be enhanced.

[0063] Furthermore, although not shown in the figure, the 10M microlens array, in addition to... Figure 2 (a) to Figure 2 (c) In addition to the generally flat shape shown by example, it may also have a curved shape, such as a curved surface. The material of the microlens array 10M is not limited to any particular material. The material of the microlens array 10M can be inorganic, organic, or inorganic / organic hybrid materials, including resin and glass.

[0064] The manufacturing method of the microlens array 10M is not limited to any particular manufacturing method. For example, a mold for transfer can be prepared in advance, and then the microlens array 10M can be formed by molding. When the formed surface, or the components and / or support containing the surface, are formed of resin or plastic, the molding method can be injection molding, blow molding, extrusion molding, casting molding, vacuum forming, etc.

[0065] Furthermore, a fluid resin or uncured resin can be poured onto a substrate or support made of materials such as glass or resin, and a microlens transfer can be performed on at least one surface of the resin using a mold. Then, by drying or curing the resin, the resin is integrated with the substrate or support to form a microlens array 10M (two-piece (2P) molding).

[0066] In addition, cylindrical lens arrays or microprism lens arrays can be formed using similar methods.

[0067] Furthermore, the first optical element 10 can be a microlens array 10M, wherein the individual microlenses can have a shape distribution. A top view of such a microlens array 10M is shown below. Figure 3A .

[0068] Figure 3A The microlens array 10M shown, for example, has a roughly square top surface of approximately 1 mm × 1 mm. The size of the microlens array 10M can vary depending on the size of the light source 1, the required illumination performance of the illumination device, etc. The shape of each microlens ML can be, for example, Figure 2 The shape shown is roughly square, but it can also be as follows: Figure 3A The polygon shown can also be a circle or an ellipse.

[0069] exist Figure 3A In the top view, the shape of each microlens ML in the microlens array 10M is a circle or a hexagon or other polygon centered on the axis of symmetry, and the lens diameter can be, for example, 25 μm or less. Furthermore, when the shape of the microlens ML is circular, the diameter of the circle is the lens diameter, and when the shape of the microlens ML is polygonal, the diameter of its circumcircle is the lens diameter.

[0070] exist Figure 3A In a 10M microlens array, six microlenses are arranged in an equally spaced and equally phased manner for each microlens (referred to as a "hexagonal close-packed array" in this paper). The lens spacing (the center-to-center distance between two adjacent lenses) is, for example, about 25 μm.

[0071] When specifically determining the microlens array to be 10M, it can be done as follows: Figure 3B As shown, for the top surface of a 10M microlens array, assuming it has a center C and a radius R... H An imaginary circle. The center position or radius of this imaginary circle can be determined, for example, based on its relationship with the shape and size of the microlens array 10M, the size of the light source 1, and the emission angle of the emitted light from the light source 1. In other words, the position or size of the imaginary circle can be determined based on the size corresponding to the effective transmission range of the emitted light.

[0072] When the top surface of the microlens array 10M is circular, the circle itself can be used as an imaginary circle. When the top surface of the microlens array 10M is elliptical, polygonal, or any other shape formed by curves or straight lines, the inscribed circle tangent to its outline can be used as an imaginary circle. Furthermore, when the top surface of the microlens array 10M is polygonal, the circles contained within it or the inscribed circle tangent to any side of the polygon can be used as imaginary circles.

[0073] The characteristics of the microlenses ML contained in the 10M microlens array are described below. For example, consider the following... Figure 3A The microlens array 10M shown is a 1mm × 1mm square on the top surface, and the microlenses ML are arranged in a hexagonal close-packed array with axisymmetric characteristics. The imaginary circle is the inscribed circle of the top surface profile of the microlens array 10M.

[0074] The geometric center of the 10M microlens array, or the axis of symmetry of the microlenses near that geometric center, can be taken as the center C of the imaginary circle. Figure 3A In the example scenario, the radius R of the imaginary circle H It is 500 μm. It should be noted that... Figure 3AThe example is provided for ease of understanding and is not intended to limit the invention.

[0075] The shape of the microlens ML can vary with the distance d from the center C of the imaginary circle. Figure 4 Let d be the distance from the center C of the imaginary circle to the center of the top surface (lens surface) of each microlens ML (d = 0 ~ R). H The graph is plotted with the horizontal axis as the x-axis and the vertical axis as the sag of the microlens ML, and it shows the curve along... Figure 3A The dashed line A-A' in the figure represents the shape of a portion of the cross-section of the microlens ML. In the example shown in the figure, the microlens ML is illustrated as a concave lens, but it is not limited to this.

[0076] from Figure 4 The graph clearly shows that, in this example, the shape of the microlens ML varies with its position (distance d) within the microlens array 10M. Specifically (at least for a portion), the microlens ML is formed such that the sag z decreases as the distance d increases. Sag, or sag amount, refers to the maximum depth (or maximum height when the microlens is convex) in a direction parallel to the axis of symmetry or optical axis of the microlens ML. Figure 4 Another feature of the example is the tangential plane of the microlens ML. Figure 4 The angle of the dashed line (in the middle) changes with the distance d. Thus, the magnitude of the divergence or diffusion angle of light relative to the axis of symmetry of the microlens ML can be evaluated based on the inclination angle of the tangent plane.

[0077] Figure 5 This is a cross-sectional view of a microlens ML cut along a plane containing an axis of symmetry. When the diameter of the microlens ML is D, the tilt angle of the tangent plane of the lens surface at a predetermined position between the center and outer edge of the microlens ML (e.g., a distance of 0.6 × D from the center) is set as a specific tilt angle β. This specific tilt angle β is one of the indicators representing the shape characteristics of the microlens ML. Figure 6 The curve graph shows that... Figure 4 The relationship between distance d and a specific tilt angle β is illustrated using the microlens shown as an example. Since the microlenses ML in the microlens array 10M are formed discretely, their specific tilt angle β relative to distance d is also a discrete angle, and the coordinates (d, β) represent... Figure 6 Any point on the dashed line.

[0078] exist Figure 6 In the example, the specific tilt angle β is d = 0 to d1 (d1 <R H A constant value within the range of d = d1 to R H Within the range, it monotonically decreases as d increases. d1 = 0.6 × R H The preferred value is d1 = 0.5 × R. HMore preferably, d1 = 0.45 × R H The specific tilt angle β of the microlens ML is between d = 0 and R. H Maximum value β within the range max The angle is 20° to 40°, preferably 22° to 35°, more preferably 25° to 32°, and especially preferably 25° to 30°. Furthermore, the specific tilt angle β of the microlens ML is in the range of d = 0 to R. H Minimum value β within the range min The angle is 5° to 25°, preferably 10° to 20°, and more preferably 12° to 18°. Furthermore, β... min / β max The value is 0.2 to 1.0, preferably 0.4 to 0.8, and more preferably 0.5 to 0.7. That is, when the distance d from the predetermined position is within the predetermined value, the multiple microlenses ML have approximately the same shape, but when the distance d exceeds the predetermined value, the shape of the microlenses ML changes with the distance d. The specific tilt angle β can be measured using an Olympus OLS4500 industrial microscope (100x objective magnification) equipped with scanning laser microscopy capabilities.

[0079] The shape of each microlens ML is, for example, an axisymmetric aspherical shape represented by Equation 1 below.

[0080] Formula 1

[0081]

[0082] Where z is the sag, r is the distance from the axis of symmetry, K is the aspherical coefficient, R is the radius (paraxial radius) when the surface near the axis of symmetry is approximated as a sphere, α2, α4, α6 are higher-order coefficients, and k is a coefficient used to adjust the specific tilt angle β of the microlens ML (specific tilt angle adjustment coefficient).

[0083] For each microlens ML, the shape of the microlens ML can be adjusted by adjusting the coefficient k common to the terms of each order. Even if the coefficient k changes to different values, as long as Equation 1 is followed, the shape of the lens will be similar. Manufacturing microlenses ML with similar shapes and different values ​​of coefficient k also reduces costs when manufacturing a 10M microlens array using a transfer mold. By making the shape of the axisymmetric microlens ML follow Equation 1, a microlens ML with the desired specific tilt angle β can be represented simply by changing the value of the specific tilt angle adjustment coefficient k, which is therefore a reasonable approach for manufacturing transfer molds, etc. Furthermore, examples of the relationship between the specific tilt angle adjustment coefficient k and the specific tilt angle β under a predetermined coefficient are as follows: Figure 7 As shown in the graph.

[0084] Figure 8 express Figure 4 and Figure 6 An example of the relationship between the distance d of the microlens ML and the specific tilt angle adjustment coefficient k. The specific tilt angle adjustment coefficient k of the microlens ML is in the range of d = 0 to d1 (d1 <R H It is a constant value within the range of d = d1 to R. H It increases monotonically within the range. d1 = 0.6 × R H The preferred value is d1 = 0.5 × R. H More preferably, d1 = 0.45 × R H .

[0085] The specific tilt angle adjustment coefficient k of the microlens ML is between d = 0 and R. H The maximum value k within the range max When the specific tilt angle adjustment coefficient k is set to 1 within the above range where the specific tilt angle adjustment coefficient k is a fixed value, the specific tilt angle adjustment coefficient k is 1.2 to 2.7, preferably 1.5 to 2.5, and especially preferably 1.7 to 2.2.

[0086] Furthermore, the specific tilt angle β of the microlens ML can have, relative to the distance d from the center C, a certain angle of inclination. Figure 9 (a) to Figure 9 The distribution shown in (c) is as follows.

[0087] The following is for reference. Figures 10A to 10G This describes a specific structural example of the first optical element 10. Figure 10A In the structural example, the resin material forming the microlens ML forms a concave microlens ML on only one side, omitting the substrate. Figure 10B In the structural example, resin material is formed only on the first surface S1 side of the substrate SB, and this resin material forms a concave microlens ML. Figure 10C In the structural example, the first surface S1 and the second surface S2 of the substrate SB form concave microlenses ML1 and ML2.

[0088] exist Figure 10D In the structural example, the resin material forming the microlens ML forms a convex microlens ML on only one side, omitting the substrate. Figure 10E In the structural example, resin material is formed only on the first surface S1 side of the substrate SB, and this resin material forms a convex microlens ML. Figure 10F In the structural example, the first surface S1 and the second surface S2 of the substrate SB form convex microlenses ML1 and ML2. Furthermore, in... Figure 10G In the structural example, one side of the resin material forms a concave microlens ML1, and the opposite side forms a convex microlens ML2 (substrate omitted).

[0089] Furthermore, as mentioned above, the specific tilt angle β of the microlens ML corresponds to the divergence angle θd when light exits after incident on the microlens ML. The divergence angle θd is defined as the exit angle corresponding to half of the maximum light intensity when parallel light is incident on the microlens ML and the light intensity per unit solid angle is calculated in a manner corresponding to the exit angle (see [link to relevant documentation]). Figure 11A ).

[0090] The divergence angle θd is measured with reference to the axis of symmetry of the microlens ML. The specific tilt angle β of the microlens ML is measured with reference to a plane perpendicular to the axis of symmetry of the microlens ML. When the microlens ML is formed on either principal plane of a flat substrate having two parallel principal planes, the angle formed by the principal plane and the tangent plane can be used as the specific tilt angle.

[0091] Furthermore, the first optical element 10 may be the aforementioned hexagonal close-packed microlens array 10M, or a microlens array in which the center positions of each microlens ML are offset along the X, Y, or Z directions based on this arrangement. The X and Y directions are orthogonal to each other within the plane of the generally flat microlenses, and the Z direction is perpendicular to the plane of the microlens array. Alternatively, the Z direction is the axis of symmetry of the microlens ML, while the X and Y directions are perpendicular to and orthogonal to the axis of symmetry. Figure 11B The image shown is a top view of an example of such a microlens array. Figure 11C As shown in the schematic diagram, in Figure 11B In the example, the arrangement of each microlens ML is shown after randomly varying by ±4μm along the X and Y directions and ±1μm along the Z direction (moving the lens in the direction of the arrow). That is, Figure 11B A microlens array can be considered as an array with an appropriate perturbation added to a hexagonal close-packed array of microlenses. Figure 11D This is a schematic diagram of adding a similar perturbation when the microlens ML is rectangular.

[0092] The following is for reference. Figure 12 The distance L between the light source 1 and the first optical element 10 will be explained. When the distance L between the light source 1 and the first optical element 10 is increased, the cross-sectional area of ​​the light beam incident on the first surface S1 of the first optical element 10 increases accordingly, resulting in a tendency for the overall size of the lighting device to increase. Conversely, when the distance L is too small, the number of structures such as microlenses or microprisms through which light passes decreases, making it easier for the emitted light from the first optical element 10 to become non-uniform.

[0093] The first optical element 10 preferably contains at least 10 microlenses ML within the cross-sectional area of ​​the light beam received from the light source 1. Let the distance from the light source 1 to the first optical element 10 be L, the outward expansion angle of the light emitted from the light source 1 be θo (where θo = FWHM / 2), and the average radius of the microlenses be D. A When the condition is met, the following formula is preferred:

[0094] 10 < π × (L × tanθo) 2 / πD A 2

[0095] √10 <L×tanθo / D A

[0096] Furthermore, more preferably, satisfying 10 <L×tanθo / D A .

[0097] In the case where the second optical element 20 is a lens, in order to enable it to emit light at a larger angle and illuminate a wider area, the second optical element is preferably a fisheye lens. A fisheye lens is a type of equidistant projection lens. Generally, there is a proportional relationship between the light incident angle θ of a fisheye lens and the image height h at the imaging position. In this embodiment, it is preferable to increase the illumination angle of the emitted light by emitting light through the second optical element 20, which is composed of such a fisheye lens.

[0098] The field of view W (full angle) of the fisheye lens used as the second optical element 20 is 150° or more, preferably 160° or more, more preferably 180° or more, and especially preferably 200° or more.

[0099] The positional relationship between the lens constituting the second optical element 20 and the light source 1 can be adjusted so that its optical axis is approximately parallel to or overlaps with the optical axis of the light source 1. When the optical axis of the second optical element 20 is adjusted to be substantially aligned with the optical axis of the light source 1, it is expected that highly symmetrical and uniform illumination light can be obtained.

[0100] The fisheye lens that can be used in this embodiment can be the fisheye lens used in interchangeable lens cameras, the fisheye lens used in the built-in camera module of smartphones or mobile terminals (including lenses that are installed on top of the original camera in a conversion manner), etc.

[0101] The light emitted by light source 1 is converted by the first optical element 10 into light with a predetermined illumination angle and uniform in-plane illumination intensity. After being refracted by a lens (such as a fisheye lens) constituting the second optical element, the illumination device can have a large illumination angle and uniform illumination intensity in all directions. The illumination device of this embodiment can be used in facial recognition systems, vehicle cameras, and three-dimensional sensing technologies for applications such as LiDAR, which are currently under development. A representative method of three-dimensional sensing technology is the Time-of-Flight (TOF) method, which is a technique for obtaining three-dimensional information by measuring the time required for illumination light to strike an object and return. In this case, since more information can be obtained when the illumination light is emitted at a larger angle, it is important that the light emitted by the light source in the illumination device is emitted at a large angle. By using the illumination device of this embodiment, the light intensity can remain constant without changing with the illumination angle (divergence angle), thereby making the analysis in the TOF method easier.

[0102] Example

[0103] The embodiments of the present invention will be described below.

[0104] Example 1

[0105] The lighting device of Example 1 is manufactured based on the following components.

[0106] Light source 1 uses a Vixar NIR-VCSEL (part number: V0081). This light source emits near-infrared light with a dominant wavelength of 940nm. Furthermore, this light source is a hexagonal close-packed multimode array, consisting of a total of 281 VCSEL light-emitting units. The typical FWHM value is 18°, and the light-emitting unit size is 0.9mm × 1mm.

[0107] Figure 13A The image shows the intensity distribution of the emitted light from the NIR-VCSEL used as light source 1. The intensity distribution of the emitted light from this light source is roughly a ring-shaped distribution with lower intensity in the central part.

[0108] Furthermore, the first optical element 10 employs a hexagonal close-packed microlens array with dimensions of 1mm × 1mm and a thickness of 0.4mm. The fundamental spacing between the microlenses ML is 24μm. The microlenses ML are hexagonal in shape, with a maximum dimension D of [missing value]. and has Figure 13B The coefficients shown and the shape represented by Equation 1.

[0109] Furthermore, the inscribed circle of the first optical element 10 is considered an imaginary circle, and the center C of this imaginary circle is simultaneously the geometric center of the microlens array 10M, and coincides with the microlens ML having an axis of symmetry. The radius R of the imaginary circle... HThe distance is 500 μm. The relationship between the distance d from the center C of the imaginary circle and k in Equation 1 is as follows: Figure 14 As shown. It should be noted that, corresponding to the way the axis of symmetry of the microlens formed with the spacing is set, the actual value of d is a discrete value.

[0110] In the range d = 0 to 200 μm (d1 = 200 μm), k = 1. In the range d = R... H When d = 500 μm, k = 1.91. Within the range of k varying with d (d = 200–500 μm), the average rate of change of k is 3 × 10⁻⁶. -3 / μm. In addition, the microlens ML is based on a basic spacing of 24μm, with a perturbation of ±4μm in the XY direction and a perturbation of ±1μm in the Z direction (vertical direction).

[0111] Furthermore, the microlens array 10M is manufactured by injection molding resin onto a glass substrate after pre-preparing a mold with a textured structure opposite to the concave-convex structure in the lens shape of the microlens array 10M. The glass substrate is a 0.4 mm thick borosilicate glass substrate (Corning's D263 T Eco). The resin is a photocurable resin (Celloxide 2021P from Daicel Corporation, with 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate as the main component).

[0112] A cross-sectional schematic diagram of the microlens array fabricated in this manner is shown below. Figure 15 .also, Figure 15 To facilitate understanding of the schematic diagram of the sag distribution, the number and size of the microlenses ML, the scale ratio to the shape of the microlens array, the scale ratio of the thickness to the sag of the microlenses ML are all different from the actual shape.

[0113] In addition, the second optical element 20 adopts, for example Figure 16 The fisheye lens shown has a field of view of 210°.

[0114] The intensity distribution of the illumination light of the lighting device shown in Figure 1 (Embodiment 1), fabricated using the aforementioned light source 1, first optical element 10, and second optical element 20, was calculated through simulation, and the results are shown below. Figure 17 The simulation used Zemax's OpticsStudio Ver20.1, where a light source with an exit surface of 0.9 mm × 1 mm is assumed to emit 1 × 10⁻⁶ rays. 7A beam of light is emitted in a weighted manner corresponding to the light intensity distribution of light source 1, and then tracked to calculate the light intensity distribution. In the light intensity distribution characteristics of the illumination device of Embodiment 1, the light intensity is 0.68 when the emission angle is 90° or -90°, and the emission angle is ±65 to 66° when the light intensity is 0.9. According to Embodiment 1, illumination light with a sufficiently large illumination angle and uniform light intensity within a predetermined range can be provided based on laser light emitted from light source 1.

[0115] Comparative Example 1

[0116] The following describes a comparative example of Example 1. In the comparative example, the microlens array of the first optical element 10 used in Example 1 is set to d1 = R. H Except for the fact that it is used as the first optical element 10 after being 500 μm in diameter, the other conditions are the same. That is, in the entire microlens array 10M of the first optical element 10 in Comparative Example 1, the shape of the microlens ML is exactly the same (k=1), and the divergence angle θd and the specific tilt angle β of the microlens ML are constant values.

[0117] Except for the microlens array 10M of the first optical element 10, the light source 1 and the second optical element 20 of the illumination device in Comparative Example 1 are the same as those in Embodiment 1, and the spacing and coaxiality of its constituent elements are also the same as those in Embodiment 1.

[0118] The intensity distribution of the illumination light from the illumination device of Comparative Example 1, which was fabricated using the aforementioned light source 1, first optical element 10, and second optical element 20, was calculated through simulation, and the results are shown below. Figure 18 Similarly, this simulation uses Zemax's OpticsStudio Ver20.1, where it is assumed that light source 1 with an exit surface of 0.9mm × 1mm will emit 1 × 10 7 A light ray is emitted in a weighted manner corresponding to the light intensity distribution of light source 1, and then tracked to calculate the light intensity distribution. The light intensity is 0.15 when the emission angle is 90° or -90°, and the emission angle is ±32 to 33° when the light intensity is 0.9.

[0119] from Figure 18 It can be seen that when the divergence angle of the microlens ML in the microlens array 10M, which serves as the first optical element 10, remains uniform within the range of the imaginary circle, a uniform light intensity distribution cannot be obtained. The reason for this is that when a fisheye lens is used as the second optical element 20, although it can achieve illumination over a wide angle range, the reflection at the interface increases as the incident angle of light on the lens or element increases. Moreover, the larger the illumination angle of the fisheye lens, the lower its transmittance.

[0120] On the other hand, when the lighting device does not include the first optical element 10 but only includes a light source 1 employing a VCSEL and a fisheye lens as the second optical element 20, the light intensity of the light irradiated at a predetermined angle is proportional to the light intensity of the light emitted from a predetermined position of the light source 1. That is, when the axis of symmetry of the light source 1, such as the VCSEL array, which emits light with a constant luminous area and a roughly axially symmetrical light intensity distribution, is coaxial with the optical axis of the fisheye lens as the second optical element 20, light near the axis of symmetry of the light source 1 (the optical axis of the entire device) is emitted from the lighting device at a smaller emission angle, while light farther from the axis of symmetry of the light source 1 is emitted from the lighting device at a larger emission angle. For this reason, in order to make the emitted light of the lighting device have a uniform light intensity distribution (illumination light intensity distribution) (i.e., to obtain illumination light with uniform brightness), it is necessary to suppress the light intensity of the portion of light emitted from near the axis of symmetry of the light source 1, and to increase or maintain or suppress the decrease of the light intensity of the portion of light emitted from farther from the axis of symmetry.

[0121] In addition to its diffusion function, the first optical element 10 used in the lighting device of the present invention can also achieve uniform brightness illumination by increasing the divergence angle θd of the structure near the center (central part) and decreasing the divergence angle θd of the structure far from the center (peripheral part). Furthermore, since the lighting device of this embodiment can use light sources such as lasers that emit high-intensity light, the problem of overall dimming caused by an increased illumination range can be solved.

[0122] other

[0123] This invention is not limited to the embodiments described above, but also includes various modified embodiments. For example, although the embodiments described above have been detailed to make the invention clear and easy to understand, the invention is not limited to all the structures described above. Furthermore, some structures of one embodiment can be replaced with structures of other embodiments. In addition, structures of other embodiments can be added to the structure of one embodiment. Moreover, for some structures in each embodiment, other structures can be added, deleted, or replaced.

Claims

1. A lighting device, characterized in that, include: A light source having at least one light-emitting unit; The first optical element receives light emitted from the light source and emits it after increasing its emission angle; as well as The second optical element receives the light emitted from the first optical element and further increases the illumination angle before emitting it. The first optical element is a microlens array composed of multiple microlenses, and the shape of each microlens is represented by the following formula: Where z is the sag, r is the distance from the axis of symmetry, K is the aspherical coefficient, R is the radius when the surface near the axis of symmetry is approximated as a sphere, α2, α4, and α6 are higher-order coefficients, and k is the adjustment coefficient of the specific tilt angle β when the tilt angle of the tangent plane of the lens surface at a predetermined position between the center and the outer edge of the microlens is set to a specific tilt angle β. In a first region where the distance from the center of the microlens array is within a first value, the adjustment coefficient k of the microlens is a constant value. In a second region where the distance from the center of the microlens array exceeds the first value, the adjustment coefficient k of the microlens increases monotonically with the increase of the distance.

2. The lighting device as claimed in claim 1, characterized in that, The microlens array is configured such that the shape of the microlenses varies with the distance from the center of the microlens array.

3. The lighting device as described in claim 2, characterized in that, In the first region, the plurality of microlenses have approximately the same shape, while in the second region, the shape of the microlenses varies with the distance.

4. The lighting device as described in claim 3, characterized in that, In the first region, the specific tilt angle β is a constant among the multiple microlenses, and in the second region, the specific tilt angle β changes with the distance.

5. The lighting device as described in any one of claims 1 to 4, characterized in that, The second optical element is a fisheye lens.

6. The lighting device as described in any one of claims 2 to 4, characterized in that, Let L be the distance from the light source to the first optical element, and let θo be the outward expansion angle of the light emitted from the light source, where θo = FWHM / 2, FWHM is the full width at half maximum (FWHM), and let D be the average value of the microlens radius. A hour, 10<π×(L×tanθo) 2 / πD A 2 。

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