Microlens array and illumination device

Abstract

Provided are a microlens array and an illumination device that are not easily affected by processing accuracy or assembly accuracy and are capable of achieving a uniform and desired light distribution characteristic. In this invention, unitary units are arranged so that the centers of the circular or elliptical top bases thereof are in a hexagonal lattice formation on a two-dimensional plane, the unitary units each being a part of a conical frustum or an elliptical frustum virtually defined by the top base, a bottom base, and a lateral part. Boundaries of the lateral parts of the unitary units each expanding in a cone shape from the top base side toward the bottom base side are defined by ridge lines or valley lines between one unitary unit and six other surrounding unitary units. The unitary units positioned adjacent to one another are densely arranged to such an extent that each of the unitary units is formed as a hexagon, in a planar view, by the ridge lines or the valley line defining the unitary units.

Description

Microlens array and lighting device

[0001] The present invention relates to a microlens array and a lighting device including the same.

[0002] In recent years, flashlights using LED (light-emitting diode) light sources or the like mounted on smartphones are required to uniformly illuminate a predetermined illumination distance and illumination range, and therefore optical lenses (flashlight lenses) are used to control light distribution. Because such flashlight lenses are incorporated into the housings of thin smartphones, the optical lenses are also required to be thin in the optical axis direction, and Fresnel lenses have generally been used in the past (e.g., Patent Documents 1 and 2).

[0003] Patent No. 5,275,557 U.S. Patent No. 7,983,552

[0004] However, such conventional flashlight lenses using Fresnel lenses are not sufficient to uniformize the light emitted from a highly directional LED light source. Furthermore, to obtain a predetermined light distribution, high precision is required in the processing of the Fresnel lens itself and in the alignment of the LED light source and the Fresnel lens. Therefore, there has been a problem in that the desired light distribution characteristics cannot be obtained due to misalignment caused by variations during manufacturing and assembly.

[0005] The present invention aims to solve the above-mentioned problems in the prior art and achieve the following objectives: That is, the present invention aims to provide a microlens array and a lighting device that are less susceptible to processing accuracy and assembly accuracy and that can obtain uniform and desired light distribution characteristics.

[0006] The microlens array described in claim 1 is characterized in that the unit units, each consisting of a portion of a circular or elliptical truncated cone defined virtually by a top, bottom, and sides, are arranged in a hexagonal lattice pattern in a two-dimensional plane, with the centers of the circular or elliptical tops of the unit units being arranged in a hexagonal lattice pattern, and the sides of the unit units extending in a cone shape from the top side to the bottom side are arranged so that each unit unit and the six unit units surrounding it are separated by ridge lines or valley lines, and the adjacent unit units are arranged so closely together that the planar view of the unit units is hexagonal due to the ridge lines or valley lines separating the unit units.

[0007] A microlens array according to a second aspect of the present invention is the microlens array according to the first aspect, wherein the unitary units have a concave dimple shape that is open on the bottom side.

[0008] A microlens array according to a third aspect of the present invention is the microlens array according to the first aspect, wherein the microlens array has a convex lens shape that protrudes toward the apex side.

[0009] A lighting device according to a fourth aspect of the present invention is characterized by comprising the microlens array according to any one of the first to third aspects of the present invention.

[0010] According to the present invention, uniform and desired light distribution characteristics can be obtained without being affected by processing accuracy or assembly accuracy.

[0011] 1A is a front view of a microlens array and a lighting device according to a first embodiment of the present invention, and FIG. 1B is an enlarged view showing the microlens array. FIG. 1C is an X-X cross-sectional view of the microlens array and lighting device according to the first embodiment of the present invention. FIG. 1A is a perspective view illustrating a microlens array according to the first embodiment of the present invention, and FIG. 1B is a diagram illustrating an arrangement of units constituting the microlens array. FIG. 1C is a front view illustrating an arrangement of the microlens array according to the first embodiment of the present invention. FIG. 1A is a perspective view illustrating a microlens array and a lighting device according to a second embodiment of the present invention, and FIG. 1B is an enlarged view showing the microlens array. FIG. 1C is a front view illustrating an X-X cross-sectional view of a microlens array and a lighting device according to the second embodiment of the present invention. FIG. 1D is an enlarged view illustrating a microlens array according to the second embodiment of the present invention. FIG. 1E is a front view of a conventional flashlight lens. FIG. 1F is an X-X cross-sectional view of a conventional flashlight lens. FIG. 1A and FIG. 1B are diagrams illustrating an irradiation pattern at the exit surface of the lighting device of the present invention. FIG. 1F and FIG. 1D are diagrams illustrating an irradiation pattern at the irradiation surface of a lighting device using a conventional flashlight lens.

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following embodiments, the same parts are denoted by the same reference numerals, and some detailed descriptions may be omitted. First Embodiment

[0013] Fig. 1 is (A) a front view of a microlens array and an illumination device according to a first embodiment of the present invention, and (B) an enlarged view showing the microlens array. Fig. 2 is an X-X cross-sectional view of the microlens array and the illumination device according to the first embodiment of the present invention. Fig. 3 is (A) a perspective view explaining the microlens array according to the first embodiment of the present invention, and (B) a diagram showing the arrangement of the units that make up the microlens array. Fig. 4 is a front view showing the arrangement of the microlens array according to the first embodiment of the present invention.

[0014] The lighting device 1 according to the first embodiment of the present invention shown in FIG. 1 includes a circular central portion having a microlens array 100 for controlling the light distribution of a projection pattern on a projection surface. At least the circular central portion of the lighting device 1, where the microlens array 100 is formed, is made of a material such as a light-transmitting transparent resin. As shown in FIG. 1B, the microlens array 100 has a plurality of light-transmitting optical elements arranged in a hexagonal lattice pattern in a two-dimensional plane. The entire lighting device 1, including the peripheral portion other than the central portion, may be integrally formed from a light-transmitting transparent resin. In this case, it is preferable to apply a light-blocking black coating to the desired peripheral portion as appropriate.

[0015] In addition, as shown in the X-X cross-sectional view of Figure 2, the lighting device 1 according to the first embodiment has a recessed shape on the formation surface side of the microlens array 100, and an LED light source (not shown) is arranged at a predetermined position in the center thereof.

[0016] 3A, each of the units 10 constituting the microlens array 100 is made up of a portion of a truncated cone or elliptical truncated shape that is virtually defined by imaginary lines of a top 11, a bottom 12, and a side 13. That is, each unit 10 is defined by the top 11 and the side 13 that expands in a cone shape from the top 11 side toward the bottom 12 side, and has a concave dimple shape that is open on the bottom 12 side.

[0017] 3(B), the centers of the tops 11 of the units 10 are arranged closely to the central unit 10 so that the units 10(a) to 10(f) surrounding the central unit 10 in a hexagonal lattice pattern in the secondary plane overlap each other at their imaginary bottoms 12 and sides 13. As a result, as shown in FIG. 3(A), each unit 10 is partitioned by the sides 13 including the ridge line 20, which define the boundaries between the central unit 10 and the six units 10(a) to 10(f) surrounding it.

[0018] Furthermore, as shown in Figure 4, each unit 10 has an elliptical top 11 when viewed in a plan view from the bottom 12 side, and the open portion on the bottom 12 side, defined by the ridge line 20, has a hexagonal concave dimple shape.

[0019] In the microlens array 100 of the first embodiment, the aperture ratio of the hexagonal open portion on the side of the top portion 11 and the bottom portion 12 defined by the ridge line 20 is 1:1.73.

[0020] In the microlens array 100 of the present invention, the apex 11 is not limited to an elliptical shape, but may be a circular shape.

[0021] In the lighting device 1 according to the first embodiment of the present invention, light from an LED light source arranged in the center of a circular microlens array 100 enters the microlens array 100 from the open side of each unit 10 that constitutes the microlens array 100, and the light distribution is appropriately controlled in each unit 10, and the light is irradiated toward the irradiation surface from the exit surface on the opposite side of the microlens array forming surface (the surface opposite the recessed side). Second Embodiment

[0022] Fig. 5 is (A) a perspective view of a microlens array and a lighting device according to a second embodiment of the present invention, (B) an enlarged view showing the microlens array, and (C) a front view showing the arrangement of the microlens array. Fig. 6 is a cross-sectional view along line X-X of a microlens array and a lighting device according to Example 2. Fig. 7 is an enlarged view illustrating a microlens array according to the second embodiment.

[0023] The illumination device 1 according to the second embodiment shown in FIG. 5 includes a circular microlens array 100 at its center for controlling the light distribution of the projection pattern on the projection surface. Similar to the microlens array according to the first embodiment, each of the units 10 constituting the microlens array 100 according to the second embodiment is formed of a portion of a truncated cone or elliptical truncated ellipse defined by imaginary lines of a top 11, a bottom 12, and a side 13. That is, as shown in FIG. 5B, each unit 10 is formed of a top 11 and side 13 extending in a cone shape from the top 11 toward the bottom 12, forming a convex lens shape projecting toward the top 11. At least the circular center portion of the illumination device 1 where the microlens array 100 is formed is made of a material such as a light-transmitting transparent resin. Furthermore, as shown in FIG. 5C, the microlens array 100 includes a plurality of light-transmitting optical elements arranged in a hexagonal lattice pattern in a two-dimensional plane.

[0024] In addition, as shown in the X-X cross-sectional view of Figure 6, the illumination device 1 according to the second embodiment has a recessed shape on the formation surface side of the microlens array 100, and an LED light source (not shown) is arranged at a predetermined position in the center thereof.

[0025] 5(C) and 7, the units 10 are arranged so that the centers of the tops 11 of the units 10 are closely spaced relative to the central unit 10, so that the units 10 surrounding it in a hexagonal lattice pattern in the secondary plane overlap each other's imaginary bottoms (not shown) and sides 13. As a result, as shown in FIG. 7, the boundaries between the central unit 10 and the surrounding units 10 are defined by the sides 13 including the valley lines 20.

[0026] Furthermore, as shown in Figure 5 (C), when viewed in a plan view from the top 11 side of each unit 10, the top 11 is elliptical in shape, and the bottom side defined by the valley line 20 is hexagonal in shape, forming a convex lens shape protruding toward the top 11 side.

[0027] In the microlens array 100 according to the present invention, the top portion 11 is not limited to an elliptical shape, but may be a circular shape.

[0028] In the lighting device 1 according to the second embodiment of the present invention, light from an LED light source arranged in the center of the lighting device 1 enters the microlens array 100 from the top 11 side of each unit 10 constituting the microlens array 100, and the light distribution is appropriately controlled in each unit 10, and the light is irradiated toward the irradiation surface from the exit surface on the opposite side of the microlens array forming surface (the surface opposite the recess side).

[0029] In the lighting device 1 according to the first and second embodiments of the present invention described above, desired light distribution characteristics can be obtained on a projection reference surface (projection surface) by appropriately setting the spacing (pitch) between the tops 11 of the units 10, the spread angle of the side portions 13 that spread in a cone shape from the top 11 side toward the bottom 12 side, and the thickness of the units 10. That is, light incident on each unit 10 is refracted at a predetermined angle at the side portions 13 in accordance with Snell's law, and is emitted from the exit surface of the lighting device 1 at a predetermined exit angle and projected onto the projection surface. At this time, since adjacent units 10 are arranged sufficiently close to each other, the exit lights from the units 10 overlap each other on the projection surface, making it possible to obtain uniform light distribution characteristics on the projection surface.

[0030] The lighting device 1 of the present invention is preferably formed by injection molding from a light-transmitting resin such as PMMA.

[0031] The graphs in FIGS. 10A to 10D are simulation diagrams showing the light distribution characteristics of light emitted from the lighting device 1 according to the first embodiment of the present invention on an XY plane (positional space), which is a virtual plane (projection plane) orthogonal to the optical axis (Z axis) having its origin at a position 1 m away from the light source (not shown) on the optical axis, and which show the illuminance (unit: lx) of light on a screen size of 1052 mm x 1403 mm, as an illuminance distribution (shading shown on the graph) corresponding to that illuminance.

[0032] The microlens array 100 of the lighting device 1 according to the first embodiment of the present invention has an elliptical apex 11 with a longitudinal dimension of 0.182 mm and a lateral dimension of 0.117 mm. Adjacent units 10 are arranged at a pitch of 0.263 mm along the longitudinal direction of the elliptical apex 11 and at a pitch of 0.122 mm along the lateral direction.

[0033] Fig. 10(A) is a diagram showing the illuminance distribution on the projection surface when the LED light source is arranged at the light source center position (XYZ) in the optical design of the microlens array 100 in the lighting device 1 according to the first embodiment of the present invention. Fig. 10(B) is a diagram showing the illuminance distribution on the projection surface when the LED light source is arranged at a position shifted by 0.35 mm in the X and Y directions and 0.077 mm in the Z direction from the light source center position in Fig. 10(A) in the lighting device 1 according to the first embodiment of the present invention.

[0034] 10(C) is a diagram showing the illuminance distribution on the projection surface when the LED light source is arranged at the light source center position (XYZ) in the optical design of Fresnel lens 200 in a conventional lighting device equipped with the general Fresnel lens 200 shown in Fig. 8 and Fig. 9. Fig. 10(D) is a diagram showing the illuminance distribution on the projection surface when the LED light source is arranged at a position shifted by 0.35 mm in the X and Y directions and 0.077 mm in the Z direction from the light source center position in Fig. 10(C) in the conventional lighting device.

[0035] As shown in Figures 10(A) and 10(B), the light that passes through the microlens array 100 according to the first embodiment of the present invention has its light distribution characteristics controlled on the projection surface, ensuring sufficient illuminance at the four corners of the desired range from the center of the projection surface, and it can be seen that even if the arrangement of the LED light source is shifted in the X, Y, and Z directions from the center position of the light source in the optical design, the uniformity of the illuminance distribution is not affected.

[0036] On the other hand, in a lighting device using a conventional Fresnel lens, as shown in FIGS. 10(C) and 10(D), when the arrangement of the LED light source shifts from the center position of the light source in the optical design, the light distribution characteristics on the projection surface of the light that has passed through the Fresnel lens 200 become non-uniform in illuminance distribution, and it is found that the desired light distribution characteristics cannot be ensured.

[0037] Even when the lighting device of the present invention uses a highly directional LED light source, high precision is not required in positioning the LED light source and the microlens array, and even if there is misalignment between them due to variations during manufacturing or assembly, the desired light distribution control and uniformity of the illuminated light can be achieved.

[0038] In the lighting device 1 of the present invention, semiconductor light-emitting elements such as LED light sources can be used, but the number and arrangement of light-emitting diodes are not particularly limited. For example, a surface light source in which multiple LED light sources are arranged at predetermined positions may be used, or a single LED light source may be used.

[0039] Furthermore, in the lighting device 1 of the present invention, the shape of the exit surface on the opposite side to the surface on which the microlens array 100 is formed (the surface opposite the recessed side) is not particularly limited, and may be flat or textured.

[0040] The material of the microlens array of the present invention is not particularly limited, but it is formed by injection molding using a light-transmitting resin such as polymethyl methacrylate (PMMA), polycarbonate (PC), or epoxy resin (EP).

[0041] The lighting device 1 according to the present invention can provide light emitted from a light source with a rectangular light distribution characteristic, and is therefore particularly suitable for applications such as camera flashes that illuminate a specific rectangular area.

[0042] REFERENCE SIGNS LIST 1 Illumination device 10 Unit 11 Top 12 Bottom 13 Side 20 Ridge or valley line 100 Microlens array 200 Fresnel lens (prior art)

Claims

1. A microlens array characterized in that unit units, each consisting of a portion of a circular or elliptical truncated cone defined imaginarily by a top, bottom, and sides, are arranged in a hexagonal lattice pattern on a two-dimensional plane, with the centers of the circular or elliptical tops of the unit units being arranged in a hexagonal lattice pattern, and the sides of the unit units, which extend in a cone shape from the top side to the bottom side, are arranged so that each unit unit and the six unit units surrounding it are separated by ridge lines or valley lines, and the planar view of the unit units is hexagonal due to the ridge lines or valley lines separating the unit units, with adjacent unit units being arranged closely together.

2. The microlens array according to claim 1, wherein the individual units are in the form of concave dimples that are open on the bottom side.

3. The microlens array according to claim 1, wherein the unitary units are in the shape of convex lenses projecting toward the top.

4. A lighting device comprising the microlens array according to any one of claims 1 to 3.

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