WO2026004140A1 - Microlens array and illumination device - Google Patents

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

The present invention relates to a microlens array and a lighting device equipped with the same.

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

Patent No. 5275557 U.S. Patent No. 7,983,552

However, flashlight lenses using such conventional Fresnel lenses are not sufficient to uniformize the light emitted from highly directional LED light sources. Furthermore, achieving the desired light distribution requires high precision in the processing of the Fresnel lens itself and in aligning the LED light source with the Fresnel lens. This means that misalignment due to variations during manufacturing and assembly can prevent the desired light distribution characteristics from being achieved.

The present invention aims to solve the above-mentioned problems in the past and achieve the following objectives. Specifically, the present invention aims to provide a microlens array and lighting device that are less affected by processing accuracy and assembly accuracy and that can achieve uniform and desired light distribution characteristics.

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 within 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 surrounding unit units are separated by ridge lines or valley lines, and adjacent unit units are arranged so closely together that a planar view of the unit units is hexagonal due to the ridge lines or valley lines separating the unit units.

The microlens array described in claim 2 is the microlens array described in claim 1, wherein the individual units have a concave dimple shape that is open on the bottom side.

The microlens array described in claim 3 is the microlens array described in claim 1, but has a convex lens shape that protrudes toward the apex.

The lighting device described in claim 4 is characterized by comprising a microlens array described in any one of claims 1 to 3.

The present invention is less susceptible to processing accuracy and assembly accuracy, and achieves uniform and desired light distribution characteristics.

1A is a front view of a microlens array and an illumination device according to a first embodiment of the present invention, and FIG. 1B is an enlarged view showing the microlens array. 1 is a cross-sectional view of the microlens array and the lighting device according to the first embodiment of the present invention taken along line XX. 1A is a perspective view illustrating a microlens array according to a first embodiment of the present invention, and FIG. 1B is a diagram illustrating an arrangement of units that constitute the microlens array. FIG. 1 is a front view showing an arrangement of a microlens array according to a first embodiment of the present invention. 10A is a perspective view illustrating a microlens array and an illumination device according to a second embodiment of the present invention, FIG. 10B is an enlarged view showing the microlens array, and FIG. 10C is a front view illustrating the arrangement of the microlens array. FIG. 10 is a cross-sectional view taken along line XX of a microlens array and an illumination device according to a second embodiment of the present invention. FIG. 10 is an enlarged view illustrating a microlens array according to a second embodiment of the present invention. FIG. 1 is a front view of a conventional flashlight lens. FIG. 1 is a cross-sectional view of a conventional flashlight lens taken along line XX. 1A and 1B are diagrams showing the irradiation pattern on the exit surface of the lighting device of the present invention, and 1C and 1D are diagrams showing the irradiation pattern on the irradiation surface of a lighting device using a conventional flashlight lens.

Embodiments of the present invention will be described below with reference to the drawings. Note that in each of the following embodiments, identical parts are designated by the same reference numerals, and some detailed descriptions may be omitted.

First Embodiment

FIG. 1 shows (A) a front view of a microlens array and a lighting device according to a first embodiment of the present invention, and (B) an enlarged view of the microlens array. FIG. 2 shows a cross-sectional view of the microlens array and a lighting device according to the first embodiment of the present invention taken along line X-X. FIG. 3 shows (A) a perspective view of 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.

The lighting device 1 according to the first embodiment of the present invention, shown in Figure 1, is provided with a microlens array 100 in the circular center portion for controlling the light distribution of the projection pattern on the projection surface. At least the circular center 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 Figure 1(B), the microlens array 100 has multiple units 10 made 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 paint or the like to desired portions of the peripheral portion as appropriate.

Furthermore, as shown in the X-X cross-sectional view of Figure 2, the illumination device 1 according to the first embodiment has a recessed shape on the surface on which the microlens array 100 is formed, and an LED light source (not shown) is disposed at a predetermined position in the center of the recessed shape.

As shown in Figure 3(A), each unit 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 the top 11, bottom 12, and side 13. That is, each unit 10 is defined by the top 11 and side 13 that extend 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.

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

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.

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

Note that the apex 11 of the microlens array 100 of the present invention is not limited to an elliptical shape and may also be circular.

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 makes up the microlens array 100, and the light distribution is appropriately controlled in each unit 10, with the light being irradiated towards the illumination surface from the exit surface on the opposite side of the microlens array formation surface (the surface opposite the recessed side).

Second Embodiment

Figure 5 shows (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. Figure 6 is a cross-sectional view of the microlens array and a lighting device according to Example 2 taken along line X-X. Figure 7 is an enlarged view illustrating the microlens array according to the second embodiment.

The lighting device 1 according to the second embodiment shown in FIG. 5 includes a circular microlens array 100 in its central portion 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 representing the apex 11, bottom 12, and side 13. That is, as shown in FIG. 5(B), each unit 10 is formed of the apex 11 and side 13 extending in a cone shape from the apex 11 toward the bottom 12, forming a convex lens shape that protrudes toward the apex 11. At least the circular center 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. Furthermore, as shown in FIG. 5(C), the microlens array 100 includes a hexagonal lattice-like arrangement of unit units 10, each consisting of a large number of light-transmitting optical elements, in a two-dimensional plane.

Furthermore, 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 surface on which the microlens array 100 is formed, and an LED light source (not shown) is disposed at a predetermined position in the center of the recessed shape.

Furthermore, as shown in Figures 5(C) and 7, the centers of the tops 11 of the units 10 are arranged closely to the central unit 10, so that the virtual bottoms (not shown) and sides 13 of the units 10 surrounding the central unit 10 in a hexagonal lattice pattern in the secondary plane overlap. As a result, as shown in Figure 7, each unit 10 is partitioned by the sides 13, which include valley lines 20, at the boundaries between the central unit 10 and the surrounding units 10.

Furthermore, as shown in Figure 5(C), when viewed in a plan view from the top 11 side, each unit 10 has an elliptical top 11, and the bottom side defined by the valley lines 20 has a hexagonal shape, forming a convex lens shape that protrudes toward the top 11 side.

Note that the apex 11 of the microlens array 100 according to the present invention is not limited to an elliptical shape and may also be circular.

In the lighting device 1 according to the second embodiment of the present invention, light from an LED light source located in the center of the lighting device 1 enters the microlens array 100 from the top 11 side of each unit 10 that makes up the microlens array 100, and the light distribution is appropriately controlled in each unit 10, and the light is irradiated toward the illumination surface from the exit surface on the opposite side of the microlens array formation surface (the surface opposite the recessed side).

The lighting device 1 according to the first and second embodiments of the present invention described above can obtain desired light distribution characteristics on the projection reference surface (projection surface) by appropriately setting the spacing (pitch) between the tops 11 of each unit 10, the angle of spread of the side portions 13 that spread in a cone shape from the top 11 side to the bottom 12 side, and the thickness of the unit 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 emission angle, projecting onto the projection surface. At this time, because adjacent unit units 10 are positioned sufficiently close to each other, the emitted light from each unit 10 overlaps with each other on the projection surface, making it possible to obtain uniform light distribution characteristics on the projection surface.

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

The graphs in Figures 10(A) to (D) 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) perpendicular to the optical axis (Z axis) with 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 indicated by the illuminance distribution (shading shown on the graph) corresponding to that illuminance.

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.

Figure 10(A) is a diagram showing the illuminance distribution on the projection surface when the LED light source is placed 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. Figure 10(B) is a diagram showing the illuminance distribution on the projection surface when the LED light source is placed at a position shifted 0.35 mm in the X and Y directions and 0.077 mm in the Z direction from the light source center position in Figure 10(A) in the lighting device 1 according to the first embodiment of the present invention.

Furthermore, Figure 10(C) shows the illuminance distribution on the projection surface when the LED light source is placed at the light source center position (XYZ) of the Fresnel lens 200 in the optical design of a conventional lighting device equipped with the general Fresnel lens 200 shown in Figures 8 and 9. Figure 10(D) shows the illuminance distribution on the projection surface when the LED light source is placed at a position shifted 0.35 mm in the X and Y directions and 0.077 mm in the Z direction from the light source center position in Figure 10(C) in a conventional lighting device.

As shown in Figures 10(A) and 10(B), the light passing through the microlens array 100 according to the first embodiment of the present invention has controlled light distribution characteristics 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 the uniformity of the illuminance distribution is not affected 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.

On the other hand, in a lighting device using a conventional Fresnel lens, as shown in Figures 10(C) and 10(D), the light distribution characteristics on the projection surface of light that has passed through the Fresnel lens 200 become uneven when the placement of the LED light source shifts from the center position of the light source in the optical design, and it is clear that the desired light distribution characteristics cannot be ensured.

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 the desired light distribution control and uniformity of the irradiated light can be achieved even if there is misalignment between the LED light source and the microlens array due to variations during manufacturing or assembly.

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

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

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

The lighting device 1 of the present invention can provide light emitted from the light source with a rectangular light distribution characteristic, making it particularly suitable for applications such as camera flashes that illuminate a specific rectangular area.

1 Lighting device 10 Unit 11 Top 12 Bottom 13 Side 20 Ridge or valley line 100 Microlens array 200 Fresnel lens (prior art)

Claims (4)

Units each consisting of a portion of a circular truncated cone or an elliptical truncated cone, which are imaginarily defined by a top, a bottom, and a side, are arranged in a hexagonal lattice pattern in a two-dimensional plane, with the centers of the circular or elliptical tops of the units being arranged in the hexagonal lattice pattern;
A microlens array characterized in that the side of the unit, which extends in a cone shape from the top side to the bottom side, has one unit and six surrounding unit units, each boundary of which is defined by a ridge line or valley line, and adjacent unit units are arranged so closely together that a planar view of the unit units is hexagonal due to the ridge lines or valley lines that define the unit units. The microlens array of claim 1, wherein the individual units have a concave dimple shape that is open on the bottom side. The microlens array of claim 1, wherein the individual units have a convex lens shape that protrudes toward the top. A lighting device equipped with the microlens array described in any one of claims 1 to 3.