Diffusion plate

Abstract

To obtain a distribution of optical characteristics smoothly varying in a plane of one diffusion plate.SOLUTION: There is provided a diffusion plate 1 that has at least one surface of a base material sectioned into a plurality of regions, where one representative microlens is set for each of the regions among a plurality of microlenses arranged in the regions, and surface shapes of the plurality of microlenses are determined by lens parameters. A first lens parameter as the lens parameter of a first representative microlens arranged in a first region among the plurality of regions and a second lens parameter as the lens parameter of a second representative microlens arranged in a second region adjacent to the first region are different, and lens parameters of the plurality of microlenses arranged between the first representative microlens and the second representative microlens are set to values interpolated based upon the first lens parameter and the second lens parameter.SELECTED DRAWING: Figure 17

Description

[Technical Field]

[0001] The present invention relates to a diffuser plate. [Background technology]

[0002] Diffusers that diffuse incident light in a desired direction are used to change the diffusion characteristics of light. Diffusers are widely used in a variety of devices, including display devices such as displays, projection devices such as projectors, and various lighting devices. One type of diffuser diffuses incident light at a desired diffusion angle by utilizing the refraction of light caused by the surface shape of the diffuser. A known example of this type of diffuser is a microlens array diffuser, in which multiple microlenses, each measuring several tens of micrometers, are arranged.

[0003] For example, Patent Document 1 discloses an irregular arrangement of multiple microlenses using a honeycomb structure as a basic pattern. In Patent Document 1, multiple microlenses are irregularly arranged on the surface of a diffuser plate so that the surface vertex position of each microlens is located within a predetermined circle centered on the surface vertex position of the basic pattern. Patent Document 1 also discloses that the variation range of the opening diameter of each microlens is kept within a predetermined range so that the diffusion characteristics of the diffuser plate are within a desired range. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4981300 Summary of the Invention [Problem to be solved by the invention]

[0005] In the technology of Patent Document 1, although the fluctuation range of the aperture diameter of each microlens arranged on the surface of the diffuser plate varies irregularly, the optical characteristics are uniform across the entire surface of a single diffuser plate.

[0006] However, in recent years, there has been a demand for the development of a diffuser that can achieve multiple different optical characteristics within the surface of a single diffuser, in order to expand the design freedom of optical equipment systems, reduce the number of components in optical equipment systems, and make optical equipment systems more compact.However, if the optical characteristics change rapidly from region to region within the surface of a single diffuser, unevenness and discontinuity in the brightness of the diffused light become noticeable, making it impossible to achieve the desired diffusion characteristics.

[0007] Therefore, the present invention has been made in consideration of the above problems, and an object of the present invention is to provide a diffuser plate that can have a distribution of optical properties that changes smoothly within the surface of a single diffuser plate. [Means for solving the problem]

[0008] In order to solve the above problem, according to one aspect of the present invention, A microlens array type diffuser plate, A substrate; a plurality of microlenses disposed on at least one surface of the substrate; Equipped with the surface on which the plurality of microlenses are disposed is divided into a plurality of regions; One representative microlens is set for each of the regions from among the plurality of microlenses arranged in the region; the surface shapes of the plurality of microlenses are determined by lens parameters; a first lens parameter, which is the lens parameter of a first representative microlens arranged in a first region among the plurality of regions, is different from a second lens parameter, which is the lens parameter of a second representative microlens arranged in a second region adjacent to the first region; A diffuser plate is provided in which the lens parameters of a plurality of microlenses arranged between the first representative microlens and the second representative microlens are set to values ​​interpolated based on the first lens parameters and the second lens parameters.

[0009] The lens parameters of the microlenses arranged between the first representative microlens and the second representative microlens may be set to gradually change from the first representative microlens to the second representative microlens.

[0010] The surface shape of the microlens is an aspherical shape expressed by an aspherical formula, The lens parameters may include aspheric coefficients used in the aspheric equation.

[0011] In the plurality of microlenses arranged between the first representative microlens and the second representative microlens, the difference in aspherical coefficient between adjacent microlenses may be greater than 0 and equal to or less than 0.2.

[0012] The lens parameters may include a radius of curvature of the microlens.

[0013] In the plurality of microlenses arranged between the first representative microlens and the second representative microlens, the difference in the radius of curvature between adjacent microlenses may be 1 μm or more and 1 mm or less.

[0014] In the first region and the second region, the lens parameters of a plurality of microlenses arranged on a virtual line connecting the first representative microlens and the second representative microlens may be set to values ​​interpolated based on the first lens parameters and the second lens parameters.

[0015] The plurality of regions may be partitioned without gaps in the X and Y directions on an XY plane that represents the surface on which the plurality of microlenses are arranged.

[0016] The representative microlens may be set to be one of a plurality of microlenses arranged within the region that is arranged at or near the center of gravity of the region.

[0017] The plurality of microlenses may be randomly arranged on the surface. [Effects of the Invention]

[0018] As described above, according to the present invention, it is possible to provide a distribution of optical characteristics that changes smoothly within the surface of one diffusion plate. [Brief explanation of the drawings]

[0019] [Figure 1] 1A and 1B are a plan view and an enlarged view schematically showing a diffuser plate according to one embodiment of the present invention. [Figure 2] FIG. 10 is a plan view schematically showing another example of the shape of the region according to the embodiment. [Figure 3] 3A and 3B are an enlarged plan view and an enlarged cross-sectional view schematically illustrating the configuration of a diffusion plate according to the embodiment. [Figure 4] FIG. 2 is an enlarged cross-sectional view schematically showing the vicinity of the boundary of the microlens according to the embodiment. [Figure 5] FIG. 2 is a plan view schematically showing the planar shape (external shape) of a microlens according to the embodiment. [Figure 6] 3A and 3B are schematic diagrams showing an example of the surface shape of a microlens according to the embodiment. [Figure 7] 10A and 10B are explanatory diagrams showing the planar shape of an anamorphic microlens according to the embodiment. [Figure 8] FIG. 2 is a perspective view showing the three-dimensional shape of an anamorphic microlens according to the embodiment. [Figure 9] 3A and 3B are explanatory diagrams showing the planar shape of a torus-shaped microlens according to the embodiment; [Figure 10] FIG. 2 is a perspective view showing the three-dimensional shape of a torus-shaped microlens according to the embodiment. [Figure 11]FIG. 2 is a perspective view showing a torus-shaped curved surface according to the embodiment; [Figure 12] 10 is a flowchart showing a method for designing a microlens according to the embodiment. [Figure 13] FIG. 2 is a plan view showing the arrangement of lens center coordinates of the microlenses according to the embodiment. [Figure 14] FIG. 2 is a plan view showing the arrangement of microlenses having a rotationally symmetric aspherical shape according to the embodiment. [Figure 15] 2A and 2B are a plan view and a perspective view showing the arrangement of microlenses having a rotationally asymmetric aspherical shape according to the embodiment; [Figure 16] FIG. 10 is a first diagram illustrating the setting of lens parameters of the microlens according to the embodiment. [Figure 17] FIG. 10 is a second diagram illustrating the setting of lens parameters of the microlens according to the embodiment. [Figure 18] 10A and 10B are diagrams illustrating an example of lens parameter settings for a microlens according to the embodiment. [Figure 19] FIG. 10 is a third diagram illustrating the setting of lens parameters of the microlens according to the embodiment. [Figure 20] 10 is a perspective view showing a method for determining the aspherical shape of a microlens according to the embodiment. FIG. [Figure 21] 10 is a flowchart showing a method for manufacturing the diffuser plate according to the embodiment. [Figure 22] FIG. 2 is an explanatory diagram showing design conditions of the first embodiment. [Figure 23] 10 is a bitmap data image showing the surface shape of the microlens array at the boundary portion of the region in Example 1. [Figure 24] 10 is a bitmap data image showing the surface shape of the microlens array at the boundary portion of the region in Example 1. [Figure 25] FIG. 10 is an explanatory diagram showing a simulation result of the first embodiment. [Figure 26] FIG. 10 is an explanatory diagram showing a simulation result of the first embodiment. [Figure 27]FIG. 10 is an explanatory diagram showing design conditions of the second embodiment. [Figure 28] 10 is a bitmap data image showing the surface shape of the microlens array at the boundary portion of the region in Example 2. [Figure 29] 10 is a bitmap data image showing the surface shape of the microlens array at the boundary portion of the region in Example 2. [Figure 30] FIG. 10 is an explanatory diagram showing a simulation result of Example 2. [Figure 31] FIG. 10 is an explanatory diagram showing a simulation result of Example 2. [Figure 32] FIG. 10 is an explanatory diagram showing design conditions of the third embodiment. [Figure 33] 10 is a bitmap data image showing the surface shape of the microlens array at the boundary portion of the region in Example 3. [Figure 34] 10 is a bitmap data image showing the surface shape of the microlens array at the boundary portion of the region in Example 3. [Figure 35] 10 is a bitmap data image showing the surface shape of the microlens array at the boundary portion of the region in Example 3. [Figure 36] 10 is a bitmap data image showing the surface shape of the microlens array at the boundary portion of the region in Example 3. [Figure 37] FIG. 10 is an explanatory diagram showing the simulation results of Example 3. [Figure 38] FIG. 10 is an explanatory diagram showing the simulation results of Example 3. [Figure 39] FIG. 10 is an explanatory diagram showing the simulation results of Example 3. [Figure 40] FIG. 20 is an explanatory diagram showing the simulation results of Example 32. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant explanations will be omitted.

[0021] <1. Overview of the diffuser> First, an overview of the diffusion plate according to the embodiment of the present invention will be described.

[0022] The diffuser plate according to this embodiment, which will be described in detail below, is a microlens array type diffuser plate that has the function of uniformly diffusing light. This diffuser plate has a substrate and a microlens array formed on the XY plane on at least one surface (principal surface) of the substrate. The microlens array is composed of a plurality of microlenses that are irregularly arranged and deployed on the XY plane. The microlenses have a convex structure (convex lenses) or a concave structure (concave lenses) that has the function of diffusing light, and have, for example, an opening width D (lens diameter) of about several tens of micrometers and a radius of curvature R of about several tens of micrometers.

[0023] In the diffuser plate according to this embodiment, the surface shape of each microlens is aspherical, and each microlens is an aspherical lens.

[0024] Furthermore, according to this embodiment, the microlenses are arranged at irregular positions on the XY plane of the substrate of the diffuser plate. For example, the microlenses may be arranged at irregular positions while overlapping each other on the XY plane so that the overlap amount Ov between adjacent microlenses falls within a predetermined tolerance range.

[0025] Furthermore, the diffuser plate according to this embodiment has multiple regions on the XY plane of the substrate that have different optical properties, such as diffusion properties, deflection properties, and deflection angle properties. This allows for greater design flexibility in the optical device system in which the diffuser plate is mounted, a reduction in the number of components in the optical device system, and a more compact optical device system. The diffusion properties indicate the range of the diffusion angle. The deflection properties indicate the range of the bending angle (deflection angle) of the beam of emitted light (diffused light) relative to the beam of incident light (normal incident light) when light is incident from a direction normal to the diffuser plate. The deflection properties indicate the range of the bending angle of the beam of emitted light (diffused light) relative to the beam of incident light (oblique incident light) when light is incident from a direction oblique to the normal to the diffuser plate.

[0026] Furthermore, in the diffuser plate according to this embodiment, the surface shapes of the microlenses are continuously different between adjacent regions (see FIG. 1 ). This allows the diffuser plate according to this embodiment to have a distribution of optical characteristics that smoothly changes within the surface of a single diffuser plate. This reduces unevenness and discontinuity in the brightness of the diffused light, thereby achieving desired diffusion characteristics. Furthermore, in the diffuser plate according to this embodiment, it is possible to avoid a situation in which the surface shapes of the microlenses located on the outer edge of one region differ significantly from those of the microlenses located on the outer edge of the other region at the boundary between adjacent regions. Therefore, the diffuser plate according to this embodiment can prevent unintended problems such as diffraction, reflection, and scattering of light at the boundary between adjacent regions.

[0027] Furthermore, in the diffuser plate according to this embodiment, the surface shapes of the multiple microlenses arranged on the XY plane are different from one another. This allows for a highly random three-dimensional surface structure of the microlens array, making it possible to control the phase overlap state of the diffused light emitted from each microlens. This reduces unevenness in the intensity distribution of the diffused light due to interference and diffraction of the diffused light emitted from the multiple microlenses, and allows for uniform light distribution of the diffused light. As a result, the diffuser plate has high transmittance brightness characteristics, satisfies the uniformity of the light distribution of the diffused light, and can control the cutoff characteristic of the intensity distribution of the diffused light.

[0028] The diffusion plate according to this embodiment having the above-described features will be described in detail below.

[0029] <2. Overall structure of the diffuser> First, the overall configuration of a diffuser plate according to one embodiment of the present invention and the layout pattern of microlenses will be described with reference to Figures 1 and 2. Figure 1 is a plan view and an enlarged view schematically showing a diffuser plate 1 according to this embodiment. Figure 2 is a plan view schematically showing another example of the shape of region 3 according to this embodiment.

[0030] The diffuser 1 according to this embodiment is a microlens array type diffuser in which a microlens array consisting of a plurality of microlenses (single lenses) is arranged on a substrate. As shown in Fig. 1, the microlens array of the diffuser 1 is composed of a plurality of regions 3. On the surface of each region 3, a plurality of microlenses are arranged in a predetermined layout pattern (arrangement pattern).

[0031] 1 shows an example in which the shape of the regions 3 constituting the microlens array of the diffuser 1 is rectangular, particularly square. However, the shape of the regions 3 is not limited to the example shown in Fig. 1, and may be any shape that can fill the surface (XY plane) of the diffuser 1 without gaps, such as an equilateral triangle or a regular hexagon.

[0032] 2, the shape of the region 3 may be a shape in which a gap is formed on the surface (XY plane) of the diffusion plate 1. The region 3 may be, for example, a perfect circle as shown in FIG. 2A, an ellipse as shown in FIG. 2B, or a rectangle as shown in FIG. 2C. For example, as shown in FIG. 2D, the shapes of the regions 3 may be different from each other. The shape of the region 3 may also be a polygon.

[0033] 1, a plurality of square regions 3 are repeatedly arranged vertically and horizontally on the surface of the diffuser plate 1. The number of regions 3 constituting the diffuser plate 1 is not particularly limited, but the diffuser plate 1 according to this embodiment includes at least two regions 3. Furthermore, the diffuser plate 1 according to this embodiment has regions 3 arranged therein that have different surface structures.

[0034] As shown in the enlarged view on the right side of FIG. 1, the layout pattern (arrangement pattern) of the multiple microlenses provided in the region 3 is continuous between the multiple adjacent regions 3 in the arrangement direction of the regions 3 (in other words, the array arrangement direction). A microlens array is formed by arranging the regions 3 without gaps while maintaining the continuity of the microlenses at the boundary between the multiple adjacent regions 3. Here, the continuity of the microlenses means that, of two adjacent regions 3, 3, the microlenses located on the outer edge of one region 3 and the microlenses located on the outer edge of the other region 3 are continuously connected without any misalignment in the planar shape or any step in the height direction.

[0035] As described above, in the diffuser 1 according to this embodiment, the microlens array is configured by arranging the regions 3 (basic structure) of the microlens array without gaps while maintaining the continuity of the boundaries. This prevents unintended problems such as diffraction, reflection, and scattering of light at the boundaries between adjacent regions 3, 3, and enables the diffuser 1 to achieve the desired light distribution characteristics.

[0036] <3. Diffuser Plate Configuration> Next, the configuration of the diffuser plate 1 according to this embodiment will be described in more detail with reference to Figs. 3 to 5. Fig. 3 is an enlarged plan view and an enlarged cross-sectional view schematically showing the configuration of the diffuser plate 1 according to this embodiment. Fig. 4 is an enlarged cross-sectional view schematically showing the vicinity of the boundary of a microlens 21 according to this embodiment. Fig. 5 is a plan view schematically showing the planar shape (external shape) of a microlens 21 when viewed from above in a direction perpendicular to the surface of a substrate 10 according to this embodiment.

[0037] As shown in FIG. 3, the diffuser plate 1 according to this embodiment includes a substrate 10 and a microlens array 20 formed on the surface of the substrate 10.

[0038] First, the substrate 10 will be described. The substrate 10 is a substrate for supporting the microlens array 20. The substrate 10 may be in the form of a film or a plate. The substrate 10 may also be in the form of a flat plate or a curved plate. The substrate 10 shown in FIG. 3 has, for example, a rectangular flat plate shape, but is not limited to this example. The shape and thickness of the substrate 10 may be any shape and thickness depending on the shape, configuration, etc. of the device in which the diffuser plate 1 is mounted.

[0039] The substrate 10 is a transparent substrate that can transmit light. The substrate 10 is made of a material that can be considered transparent in the wavelength band of light that is incident on the diffuser plate 1. For example, the substrate 10 may be made of a material that has a light transmittance of 70% or more in the wavelength band of visible light.

[0040] The substrate 10 may be formed of a known resin such as polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polycarbonate (PC), cycloolefin copolymer (COC), cycloolefin polymer (COP), triacetylcellulose (TAC), etc. Alternatively, the substrate 10 may be formed of a known optical glass such as quartz glass, borosilicate glass, white plate glass, etc.

[0041] Next, the microlens array 20 will be described. The microlens array 20 is provided on at least one surface (main surface) of the substrate 10. The microlens array 20 is a collection of a plurality of microlenses 21 (single lenses) arranged on the surface of the substrate 10. In this embodiment, as shown in FIG. 3, the microlens array 20 is formed on one surface (main surface) of the substrate 10. However, without being limited to this example, the microlens array 20 may be formed on both main surfaces (front and back surfaces) of the substrate 10.

[0042] The surface of the substrate 10 on which the microlens array 20 is provided may be, for example, a flat surface. Hereinafter, the flat surface of the substrate 10 may also be referred to as the XY plane. The X and Y directions in the XY plane are parallel to the surface of the substrate 10. The X and Y directions are perpendicular to each other. The Z direction is perpendicular to the surface of the substrate 10 (i.e., the normal direction) and corresponds to the thickness direction of the diffuser plate 1. The Z direction is perpendicular to the XY plane, the X direction, and the Y direction.

[0043] The microlenses 21 are minute optical lenses on the order of, for example, several tens of μm. The microlenses 21 constitute single lenses of the microlens array 20. The microlenses 21 may have a concave structure (concave lens) formed so as to be recessed in the thickness direction of the diffuser plate 1, or may have a convex structure (convex lens) formed so as to protrude in the thickness direction of the diffuser plate 1. In this embodiment, an example in which the microlenses 21 have a convex structure (convex lens) as shown in FIG. 3 will be described, but the present invention is not limited to such an example. Depending on the desired optical characteristics of the diffuser plate 1, the microlenses 21 may have a concave structure (concave lens).

[0044] The surface shape of the microlens 21 is aspherical. The surface shape of the microlens 21 is not particularly limited as long as it is a curved shape that includes at least a portion of an aspherical component. For example, the surface shape of the microlens 21 may be an aspherical shape that includes only an aspherical component, or a curved shape that includes an aspherical component and a spherical component or other curved component. For example, the surface shape of the vertex side of the lens surface of the microlens 21 may be aspherical, and the surface shape of the other portion may be spherical. Such a surface shape is also included in the aspherical shape of the microlens 21 according to this embodiment.

[0045] As shown in FIG. 3, the microlenses 21 are preferably arranged densely so that they are adjacent to each other with no gaps. In other words, the microlenses 21 are preferably arranged continuously so that there are no gaps (flat portions) at the boundaries between the adjacent microlenses 21. The microlenses 21 are preferably arranged without gaps on the substrate 10. In other words, the microlenses 21 are preferably arranged so that the packing ratio of the microlenses 21 is 100%. This makes it possible to suppress the component of the incident light that is transmitted directly without being scattered on the surface of the diffuser plate 1 (hereinafter also referred to as the "zero-order transmitted light component"). As a result, the microlens array 20 in which the microlenses 21 are arranged adjacent to each other with no gaps can further improve the diffusion performance.

[0046] In order to suppress the zero-order transmitted light component, the filling rate of the microlenses 21 on the substrate 10 is preferably 90% or more, and more preferably 100%. Here, the filling rate refers to the proportion of the area of ​​the surface of the substrate 10 (on the XY plane) occupied by the multiple microlenses 21. If the filling rate is 100%, the surface of the microlens array 20 will be formed by curved surface components and will contain almost no flat surface components.

[0047] However, in the actual manufacturing of the microlens array 20, the curved surfaces of the multiple microlenses 21 are continuously connected, so the vicinity of the inflection point at the boundary between the adjacent microlenses 21 may become substantially flat. In such a case, the width of the substantially flat region near the inflection point at the boundary between the microlenses 21 (the width of the boundary line 24 between the microlenses 21 shown in FIGS. 4 and 5) is preferably 1 μm or less. This allows the zero-order transmitted light component to be sufficiently suppressed.

[0048] Furthermore, in the microlens array 20 according to this embodiment, the multiple microlenses 21 are arranged irregularly (randomly) on the XY plane. Here, "irregular" means that there is no substantial regularity in the arrangement of the microlenses 21 in any region of the microlens array 20. However, even if there is some regularity in the arrangement of the microlenses 21 in a small region, the "irregular" arrangement includes the absence of regularity in the arrangement of the microlenses in the entire region. Note that a method for irregularly arranging the microlenses 21 in the microlens array 20 according to this embodiment will be described later.

[0049] Furthermore, between adjacent regions 3, lens parameters such as the radius of curvature R, aspherical coefficient A, conic constant K, and aperture width D, which determine the surface shape of each microlens 21, may vary smoothly. That is, between adjacent regions 3, at least one lens parameter selected from the group consisting of the radius of curvature R, aspherical coefficient A, conic constant K, and aperture width D of each microlens 21 may be a continuously varying (gradually changing) variable value rather than a predetermined fixed value. The radius of curvature R is the radius of curvature in the X or Y direction of the curved surface shape of the microlens 21. The aspherical coefficient A is a coefficient included in the aspherical equation. The conic constant K is a constant included in the aspherical equation. The aperture width D is the width in the X or Y direction of the opening 27 of the microlens 21 (see FIG. 5 ) and corresponds to the lens diameter of the microlens 21.

[0050] In this way, the lens parameters of each microlens 21 of the microlens array 20 according to this embodiment continuously change for each microlens 21 between adjacent regions 3. Furthermore, on the surface of the substrate 10 (on the XY plane), the multiple microlenses 21 are densely and continuously arranged so as to overlap each other, and the individual microlenses 21 are arranged at irregular positions on the XY plane.

[0051] As a result, the surface shape (three-dimensional curved shape) of each microlens 21 changes continuously between adjacent regions 3, and the planar shape of each microlens 21 (the shape projected onto the XY plane of the substrate 10) varies irregularly. As a result, the surface shape and planar shape of each microlens 21 are different from one another. Therefore, the multiple microlenses 21 have various planar shapes, as schematically shown in FIG. 3, and many of them are not symmetrical.

[0052] As a result, as shown in FIG. 4, the radius of curvature of the microlens 21A becomes R A On the other hand, the radius of curvature of the microlens 21B adjacent to the microlens 21A is R B (≠RA The radius of curvature R of the adjacent microlenses 21A and 21B is A , R B are different from each other, the boundary line 24 between the microlenses 21A and 21B is not made up of only straight lines, but is made up of at least a part that includes a curve.

[0053] Specifically, as shown in Fig. 5, consider a case where the microlens 21 is viewed in plan from a normal direction (Z direction) perpendicular to the surface of the substrate 10. In this case, the outline of the planar shape of the microlens 21 (boundary lines 24 between the microlens 21 and the other adjacent microlenses 21) is made up of multiple curves with different curvatures. In this way, when the boundary lines 24 between the adjacent microlenses 21, 21 include multiple curves with different curvatures, the regularity of the boundary between the microlenses 21, 21 is further disrupted, and the diffraction component of the diffused light can be further reduced.

[0054] 4. Microlens surface shape Next, the surface shape of the microlens 21 according to this embodiment will be described with reference to FIGS.

[0055] 4.1. Rotationally symmetric aspherical shape 6 is a schematic diagram showing an example of the surface shape of the microlens 21 according to this embodiment. In the following description, the surface 26 of the microlens 21 will be referred to as the "lens surface 26," and the surface shape of the microlens 21 (i.e., the curved shape of the lens surface 26) will also be referred to as the "lens surface shape."

[0056] As shown in FIG. 6, the curved surface shape (lens surface shape) of the lens surface 26 of the microlens 21 according to the present embodiment has an aspherical shape such as an elliptical surface, a parabolic surface, or a hyperbolic surface. In FIG. 6, an example is shown in which the aspherical shape of the lens surface 26 is a vertically long elliptical surface (conic coefficient K>0) in the direction of the optical axis 25. Note that the elliptical surface means a rotational elliptical surface that is the surface of a rotational ellipsoid. The rotational ellipsoid is a rotating body obtained by rotating an ellipse about its major axis or minor axis. The elliptical surface in the case of K>0 is the surface of a rotational ellipsoid (that is, a long ellipsoid) obtained by rotating the major axis of the ellipse as the rotation axis. On the other hand, the elliptical surface in the case of -1<K<0 is the surface of a rotational ellipsoid (that is, a flattened ellipsoid) obtained by rotating the minor axis of the ellipse as the rotation axis. In either case, the rotation axis of the rotational ellipsoid coincides with the optical axis 25 of the microlens 21.

[0057] As shown in FIG. 6, the optical axis 25 of the microlens 21 extends in the normal direction (Z direction) with respect to the surface (XY plane) of the base material 10 of the diffusion plate 1. That is, the optical axis 25 overlaps the Z axis. The surface shape of the microlens 21 according to the present embodiment is, for example, an aspherical shape that is rotationally symmetric about the normal direction (Z direction) with respect to the XY plane. Note that the aspherical shape may be, for example, an aspherical shape that is rotationally asymmetric about the Z direction as long as the optical axis 25 is parallel to the Z direction. When the lens surface shape is an aspherical shape, the vertex 28 of the microlens 21 is located on the optical axis 25 and the Z axis.

[0058] The aperture width D of the microlens 21 is the width (lens diameter) of the aperture 27 of the microlens 21 in the XY plane. The aperture width D is represented by the aperture width Dx in the X direction and the aperture width Dx in the X direction. Also, the radius of curvature R of the microlens 21 is the radius of curvature at the top of the lens surface shape. The radius of curvature R is represented by the radius of curvature Rx in the X direction and the radius of curvature Ry in the Y direction. As shown in FIG. 6, when the lens surface shape is an aspherical shape and is rotationally symmetric about the optical axis 25, Dx = Dy and Rx = Ry.

[0059] The center point 30 of the aspherical shape is the origin (x, y, z) when designing the aspherical shape of the microlens 21. Specifically, in the design stage of the microlens array 20, the aperture surface of the aspherical shape of the microlens 21 is designed to be a circle, an ellipse, or the like. At this time, the aperture surface is set on the xy plane where z = 0 so that the radius x (x = y) of the circle or the minor axis x and major axis y of the ellipse are set to predetermined lengths. The origin (x = 0, y = 0, z = 0) in this xyz space is the origin (x, y, z) when designing the aspherical shape, and this origin (x, y, z) corresponds to the center point 30. While FIG. 6 illustrates the center point 30 as being on the surface (XY plane) of the substrate 10, the center point 30 does not have to be on the XY plane.

[0060] The surface shape (lens surface shape) of the microlens 21 according to this embodiment is preferably an aspherical shape that is rotationally symmetric about the optical axis 25, as shown in FIG. 6. The rotationally symmetric aspherical shape is, for example, an ellipsoid (-1 <K<0、K> 0), paraboloid (K=-1), or hyperboloid (K<-1). Note that "K" is the Conic coefficient, which is used in the formula that defines the aspherical shape.

[0061] As described above, the lens surface shape according to this embodiment is preferably an aspherical shape that is rotationally symmetric about the optical axis 25. This has the advantage that the microlens 21 can be designed and manufactured relatively easily.

[0062] Furthermore, when the aspherical shape of the microlens 21 according to this embodiment is expressed by an aspherical lens formula using the Conic coefficient K, the Conic coefficient K in the aspherical lens formula is preferably greater than 0 (K>0). If K>0, the lens surface shape becomes an ellipsoid that is vertically elongated in the direction of the optical axis 25. This has the effect of making it easier to achieve both a deflection function and diffusion control.

[0063] When the aspherical shape of the microlens 21 is rotationally symmetric about the optical axis 25, the aspherical lens equation representing the aspherical shape can be, for example, the following equation (0).

[0064] Z=(x 2 / R) / {1+(1-(1+K)·x 2 / R 2 ) 0.5}+A4·x 4 +A6·x 6 ···(0) In the formula (0), the parameters are as follows: Z:Sag amount x: distance from the Z axis R: radius of curvature K: Conic coefficient A4, A6: 4th and 6th order aspheric coefficients

[0065] Furthermore, the aspect ratio k of the surface shape of the microlenses 21 (i.e., the aspherical shape) is preferably 0.1 or more and 1.1 or less, and more preferably 0.2 or more and 0.6 or less, which has the effect of making it easier to control the diffusion angle and to realize the structural formation of the microlenses 21.

[0066] Here, the aspect ratio k is the maximum lens height h of the plurality of microlenses 21. MAX and the aperture width Dx of the microlens 21 (k=h MAX / Dx). Maximum lens height h MAX is the difference between the maximum lens vertex height h1 and the minimum boundary point height h2 (h MAX =h1-h2). The maximum lens vertex height h1 is the height of the vertex of the microlens 21 with the highest vertex among the multiple microlenses 21 included in one region 3 shown in Figure 1. The minimum boundary point height h2 is the height of the lowest point of the boundary line around the microlens 21.

[0067] <4.2. Non-rotationally symmetric aspherical shapes> As described above, the microlens 21 according to this embodiment preferably has an aspherical shape that is rotationally symmetric about the optical axis 25. This rotationally symmetric aspherical shape is an aspherical shape that is isotropic about the optical axis 25. However, the surface shape of the microlens 21 is not limited to this example, and may be, for example, an aspherical shape that is not rotationally symmetric about the optical axis 25, or an aspherical shape that is anisotropic.

[0068] 7 to 11, an example will be described in which the surface shape of the microlens 21 is an aspherical shape that is rotationally asymmetric with respect to the optical axis 25 and has anisotropy. As the aspherical shape that has anisotropy stretched in a predetermined direction, for example, an anamorphic shape or a torus shape can be used.

[0069] (1) Anamorphic shape First, the anamorphic microlens 21 will be described with reference to Fig. 7 and Fig. 8. Fig. 7 is an explanatory diagram showing the planar shape of the anamorphic microlens 21. Fig. 8 is a perspective view showing the three-dimensional shape of the anamorphic microlens 21.

[0070] The microlens 21 shown in FIGS. 7 and 8 is a so-called anamorphic lens, and its surface shape is an aspherical shape including an anamorphically curved surface. As shown in FIG. 7, the planar shape of the microlens 21 is an anisotropic elliptical shape. The major axis of the elliptical shape in the Y-axis direction is Dy, and the minor axis of the elliptical shape is Dx. These Dx and Dy correspond to the aperture diameters of the microlens 21 in the X-axis direction and the Y-axis direction. As shown in FIG. 8, the surface shape of the microlens 21 is an aspherical curved surface having predetermined radii of curvature Rx and Ry in the major axis direction and the minor axis direction of the elliptical shape, respectively. The microlens 21 has an aspherical shape having anisotropy in the Y-axis direction.

[0071] Here, a method for setting the surface shape of the anamorphic microlens 21 will be described with reference to Fig. 8 and the following formula (1). The curved surface (aspherical surface) of the anamorphic shape shown in Fig. 8 is expressed by the following formula (1). The following formula (1) is an example of a formula that expresses the curved surface (aspherical surface) of the anamorphic shape.

[0072]

number

[0073] In the formula (1), the parameters are as follows: Cx=1 / Rx Cy=1 / Ry Rx: Radius of curvature in the X direction Ry: Radius of curvature in the Y direction Kx: Conic constant in the X direction Ky: Conic constant in the Y direction A 3x : Aspheric coefficient of the third order term in the X direction A 4x : Aspheric coefficient of fourth order term in the X direction A 3y : Aspheric coefficient of the third order term in the Y direction A 4y : Aspheric coefficient of fourth-order term in the Y direction

[0074] 8, a curved surface is cut out from the anamorphic curved surface defined by the above formula (1) so that the minor axis in the X direction of the ellipse on the XY plane is Dx and the major axis in the Y direction is Dy. The shape of this cut-out curved surface is set as the surface shape (anamorphic shape) of the microlens 21.

[0075] (2) Torus shape Next, another example (torus shape) of the aspherical shape of the microlens 21 will be described with reference to Fig. 9 to Fig. 11. Fig. 9 is an explanatory diagram showing the planar shape of the torus-shaped microlens 21. Fig. 10 is a perspective view showing the three-dimensional shape of the torus-shaped microlens 21. Fig. 11 is a perspective view showing the curved surface of the torus shape.

[0076] As shown in FIGS. 9 to 11, the surface shape of the microlens 21 is an aspherical shape including a partially curved surface of a torus shape. A torus is a surface of revolution obtained by rotating a circle. Specifically, as shown in FIG. 11, a so-called doughnut-shaped torus is obtained by rotating a small circle (radius: r) around a rotation axis (X-axis) located outside the small circle along the circumference of a large circle (radius: R). The curved shape of the surface (torus surface) of this torus is the torus shape. By cutting out the outer portion of this torus shape, a three-dimensional torus-shaped microlens 21 is obtained as shown in FIG. 10.

[0077] As shown in FIG. 9, the planar shape of the torus-shaped microlens 21 is an anisotropic elliptical shape. The major axis of the elliptical shape in the Y-axis direction is R, and the minor axis of the elliptical shape in the X-axis direction is r. These r and R correspond to the aperture widths Dx and Dy of the microlens 21 in the X and Y directions. As shown in FIG. 10, the three-dimensional shape of the microlens 21 is formed by an aspherical curved surface having predetermined radii of curvature R and r in the major and minor axis directions of the elliptical shape. The microlens 21 has an aspherical shape that is anisotropic in the Y-axis direction.

[0078] Here, a method for setting the surface shape of the torus-shaped microlens 21 will be described with reference to Fig. 11 and the following formula (2). Fig. 11 is a perspective view showing an aspherical curved surface expressed by the following formula (2). In formula (2), R is the radius of the major circle, and r is the radius of the minor circle.

[0079]

number

[0080] 11, a curved surface is cut out from the torus-shaped curved surface defined by the above formula (2) so that the minor axis in the X direction of the ellipse on the XY plane is r and the major axis in the Y direction is R. The shape of this cut-out curved surface portion is set as the curved surface shape (torus shape) of the microlens 21.

[0081] The above-described aspherical shapes such as the anamorphic shape and torus shape are not rotationally symmetric about the optical axis 25 of the microlens 21. However, the aspherical shape is symmetric in the Y direction with respect to the XZ plane including the optical axis 25, and is symmetric in the X direction with respect to the YZ plane including the optical axis 25. The surface shape of the microlens 21 may be an aspherical shape (for example, an anamorphic shape or a torus shape) that has such symmetry and anisotropy.

[0082] In addition to the above-mentioned examples, the aspherical shape of the anisotropic microlens 21 may also be, for example, an aspherical shape cut out from an ellipsoid.

[0083] 5. Microlens design method Next, a method for designing a microlens according to this embodiment will be described with reference to Fig. 12 to Fig. 20. Fig. 12 is a flowchart showing the method for designing a microlens according to this embodiment.

[0084] (S10) Setting the lens center coordinates 12, first, the lens center coordinate pn of each microlens 21 is set on the surface (XY plane) of the microlens array 20. The lens center coordinate pn is the coordinate on the XY plane of the center point 30 (see FIG. 6) of each microlens 21. When setting the lens center coordinate pn, it is preferable that the lens center coordinates pn are set at irregular positions so that the intervals between the lens center coordinates pn on the XY plane are distributed within a predetermined range.

[0085] Specifically, as shown in Fig. 13, a plurality of lens center coordinates pn(xpn, ypn) are set on the XY plane of region 3 of microlens array 20, the size of which is set in advance. Note that n is the number of installed microlenses 21 (n = 1, 2, 3, ...). The plurality of lens center coordinates pn(xpn, ypn) are arranged on the XY plane so that the intervals between the plurality of lens center coordinates pn are within a predetermined range.

[0086] 14, an adjustment process may be performed on the overlap amount Ov between adjacent microlenses 21, 21, as needed. By this adjustment process, the lens center coordinates pn of the multiple microlenses 21 are adjusted so that the overlap amount Ov between adjacent microlenses 21, 21 on the XY plane falls within a predetermined allowable range (for example, equal to or less than a predetermined value), and the lens center coordinates pn of the multiple microlenses 21 are arranged irregularly.

[0087] 14, first, the x and y coordinates of the lens center coordinates pn of a newly placed microlens 21 and the lens radius r are determined using random numbers. Next, the overlap amount Ov between the planar shape of each microlens 21 already placed and the planar shape of the newly placed microlens 21 is calculated. The overlap amount Ov is the overlap width between the planar shapes of two adjacent microlenses 21, 21, and can be calculated using the following equation (50).

[0088] Ov=ri+rj-((xi-xj) 2 +(yi-yj) 2 ) 0.5 ···(50) In the equation (50), the parameters are as follows: Ov: Amount of overlap between adjacent microlenses 21, 21 xi, yi: lens center coordinates pi of one microlens 21 ri: radius of one microlens 21 xj, yj: lens center coordinates pj of the other microlens 21 rj: radius of the other microlens 21

[0089] In this way, when a new microlens 21 is arranged on the XY plane, the overlap amount Ov with the already arranged microlenses 21 is calculated, and if the overlap amount Ov is within a preset tolerance range, the new microlens 21 is arranged. Conversely, if the calculated overlap amount Ov is outside the tolerance range (for example, if it exceeds the upper limit of the tolerance range or is below the lower limit of the tolerance range), the new microlens 21 is not arranged. It is preferable to determine the tolerance range in advance depending on the optical characteristics required of the microlens array 20, etc.

[0090] As described above, as shown in FIG. 14, the lens center coordinates pn of the microlenses 21 may be irregularly arranged on the XY plane while the overlap amount Ov is adjusted within the allowable range. This allows the multiple microlenses 21 to be arranged at irregular positions on the XY plane while overlapping with each other with an appropriate overlap amount Ov. This prevents the occurrence of flat areas that do not form lens surfaces between adjacent microlenses 21, thereby suppressing the occurrence of zero-order diffracted light that passes through the flat areas of the diffuser plate 1. This also reduces unevenness in the intensity distribution of diffused light due to interference and diffraction of the diffused light emitted from the multiple microlenses 21. Furthermore, because the microlenses 21 do not overlap excessively, the formability and feasibility of the microlens array structure are not impaired.

[0091] (S12) Lens parameter setting Next, lens parameters of each microlens 21 are set as shown in Fig. 12. The lens parameters are parameters that determine the surface shape (lens surface shape) of the microlens 21. In this embodiment, it is preferable that the lens parameters are set so as to smoothly change between adjacent regions 3.

[0092] When the lens surface shape is an aspherical shape that is rotationally symmetric about the optical axis 25, such as an ellipsoid (the surface of a spheroid whose axis of rotation is the direction of the optical axis 25), a paraboloid, or a hyperboloid (see FIG. 14), the lens parameters include, for example, the aperture width D (lens diameter) of the microlens 21, the radius of curvature R of the apex of the microlens 21, the aspherical coefficient A, the conic constant K, the tilt angle α, and the azimuth angle β. The tilt angle α is the tilt angle (0 to 90°) of the optical axis 25 of the microlens 21 with respect to the normal direction (Z direction) of the surface of the diffuser. The azimuth angle β is an angle that represents the tilt direction of the optical axis 25 of the microlens 21 on the XY plane, and is expressed as an angle (0 to 360°) of the tilt direction with respect to the X-axis direction, for example.

[0093] On the other hand, as shown in FIG. 15 , when the lens surface shape is rotationally asymmetric about the optical axis 25 and has an anisotropic aspherical shape, such as an anamorphic shape or a torus shape, the lens parameters may be parameters used in a function (z = f(d)) that defines the aspherical shape. In this case, the height direction value z of the lens surface shape is expressed as a function (z = f(d)) of the distance d from the lens center coordinate pn on the XY plane. The distance d may include the distance dx in the X direction from the lens center coordinate pn on the XY plane and the distance dy in the Y direction. The position z of the lens surface shape in the height direction can be determined by a function using the distances dx and dy (z = f(dx, dy)). In addition, the lens parameters may be, for example, the aperture width D (lens diameter) of the microlens 21, the radius of curvature R of the apex of the microlens 21, the aspherical coefficient A, the conic constant K, the tilt angle α, the azimuth angle β, etc.

[0094] When the lens surface shape is an aspherical shape (e.g., an ellipsoid, a paraboloid, a hyperboloid, etc.) that is rotationally symmetric about the optical axis 25, the planar shape of the microlens 21 is, for example, a circle as shown in Fig. 14. On the other hand, when the lens surface shape is an aspherical shape (e.g., an anamorphic shape, a torus shape) that is rotationally asymmetric about the optical axis 25, the planar shape of the microlens 21 is, for example, an ellipse or a shape that approximates an ellipse as shown in Fig. 15.

[0095] Furthermore, in this embodiment, the lens parameters are set so that the surface shapes of the multiple microlenses 21 change smoothly between adjacent regions 3. Note that "adjacent" includes both line contact between adjacent regions 3 and point contact between adjacent regions 3. For example, in the example of FIG. 18B described below, regions 3a and 3b are in line contact and therefore can be said to be adjacent to each other. Furthermore, regions 3a and 3d are in point contact and therefore can be said to be adjacent to each other.

[0096] A design method for continuously changing the lens parameters of a plurality of microlenses 21 between adjacent regions 3 will be described below with reference to Fig. 16 and Fig. 17. Fig. 16 is a first diagram illustrating the setting of the lens parameters of the microlenses 21 according to this embodiment. Fig. 17 is a second diagram illustrating the setting of the lens parameters of the microlenses 21 according to this embodiment.

[0097] As shown in the upper diagram of Fig. 16 (Fig. 16A), for example, it is assumed that the microlenses 21 are arranged at irregular positions on the surface of the substrate 10. As shown in the lower diagram of Fig. 16 (Fig. 16B), the surface (XY plane) of the substrate 10 on which the multiple microlenses 21 are arranged is virtually divided (segmented) into multiple regions 3. In the example shown in Fig. 16B, the surface of the substrate 10 is virtually divided into three rectangular regions 3A to 3C.

[0098] 17A, in this embodiment, one representative microlens 50 (indicated by a black circle in FIG. 17) is set for each region 3 from among the plurality of microlenses 21 arranged in that region 3. The representative microlens 50 is set to any one of the plurality of microlenses 21 arranged in that region 3. It is preferable that the representative microlens 50 be set to a microlens 21, among the plurality of microlenses 21 arranged in that region 3, that is arranged at or near the center of gravity of that region 3. This makes it possible to further prevent unintended defects such as diffraction, reflection, and scattering of light at the boundary between adjacent regions 3.

[0099] In this embodiment, the first lens parameters are different from the second lens parameters. The first lens parameters are lens parameters of the first representative microlens 50 arranged in the first region 3 among the multiple regions 3. The second lens parameters are lens parameters of the second representative microlens 50 arranged in the second region 3 adjacent to the first region 3.

[0100] 17B, ​​in this embodiment, the lens parameters of the plurality of microlenses 21 (hereinafter referred to as "intermediate microlenses 60") disposed between the first representative microlens 50 and the second representative microlens 50 are set to values ​​interpolated based on the first lens parameters and the second lens parameters. By setting the lens parameters of each of the plurality of intermediate microlenses 60 (shown by white circles in FIG. 17B) to values ​​interpolated from the first lens parameters and the second lens parameters, it becomes possible to gradually change the lens parameters of the plurality of intermediate microlenses 60 from the first representative microlens 50 to the second representative microlens 50.

[0101] The interpolation may be, for example, spline interpolation, linear interpolation, Lagrange interpolation, etc., and is preferably spline interpolation. By setting the lens parameters of the intermediate microlenses 60 to values ​​obtained by spline interpolation from the first lens parameters and the second lens parameters, it becomes possible to change the lens parameters of the intermediate microlenses 60 more smoothly from the first representative microlens 50 to the second representative microlens 50.

[0102] Furthermore, in the first region 3 and the second region 3, the lens parameters of the multiple microlenses 21 arranged on the virtual line V connecting the first representative microlens 50 and the second representative microlens 50 are preferably set to values ​​interpolated based on the first lens parameters and the second lens parameters. Of the multiple microlenses 21 arranged on the virtual line V, one or more microlenses 21 other than the intermediate microlens 60 will hereinafter be referred to as "linear microlenses 70." This makes it possible to smoothly change the lens parameters of one or more linear microlenses 70 (indicated by gray circles in FIG. 17B) arranged in a direction away from the second representative microlens 50 in addition to the lens parameters of the intermediate microlens 60. Also, in the second region 3, it makes it possible to smoothly change the lens parameters of one or more linear microlenses 70 arranged in a direction away from the first representative microlens 50 in addition to the lens parameters of the intermediate microlens 60.

[0103] In this case, the rate of change in lens parameters of the multiple intermediate microlenses 60 and linear microlenses 70 arranged on the virtual line V may be constant in a predetermined direction on the virtual line V. Also, the rate of change in lens parameters of the multiple linear microlenses 70 arranged in a direction away from the first representative microlens 50 may be set to be the same as the rate of change in lens parameters in a direction from the first representative microlens 50 to the second representative microlens. Similarly, the rate of change in lens parameters of the multiple linear microlenses 70 arranged in a direction away from the second representative microlens 50 may be set to be the same as the rate of change in lens parameters in a direction from the second representative microlens 50 to the first representative microlens.

[0104] The virtual line V is, for example, a line connecting the center of the first representative microlens 50 and the center of the second representative microlens 50. The virtual line V may be, for example, a line connecting an arbitrary point within the planar shape of the first representative microlens 50 and an arbitrary point within the planar shape of the second representative microlens 50 on the XY plane. The intermediate microlens 60 and the linear microlens 70 are microlenses 21 in which at least a part of the planar shape of the microlens 21 is located on the virtual line V on the XY plane, for example.

[0105] The lens parameters to be interpolated include, for example, the radius of curvature R of the microlenses 21, the aspherical coefficient A, the conic constant K, the aperture width D (lens diameter) of the microlenses 21, the tilt angle α, and the azimuth angle β. This makes it possible to provide a diffuser 1 having a distribution in which the surface shapes of the multiple microlenses 21 change continuously (smoothly) within the plane (in the XY plane).

[0106] Furthermore, among the lens parameters, the lens parameters to be interpolated as described above (hereinafter referred to as "interpolation target parameters") preferably include the aspherical coefficient A of the microlenses 21. This allows the bending angle of the outgoing light (diffused light) relative to the beam of obliquely incident light or normally incident light to be different for each of the multiple regions 3 provided on the diffuser plate 1. This makes it possible to provide a diffuser plate 1 with both a diffusion function and a deflection angle function. This allows for greater design freedom in an optical device system incorporating the diffuser plate 1, a reduction in the number of components in the optical device system, and a more compact optical device system. Furthermore, varying the bending angle allows for changes in the aspect ratio of an image projected through the diffuser plate 1, changes in the outer edge shape of the projected image, and the brightness distribution of the projected image. Note that there is no limitation on the number of degrees of the aspherical coefficient A, but the aspherical coefficient A is preferably a third-order aspherical coefficient A3, and more preferably a third-order aspherical coefficient A3 and a fourth-order aspherical coefficient A4. This further increases the design freedom of the bending angle. Alternatively, it may be either or both of the aspherical coefficient A in the X direction and the aspherical coefficient A in the Y direction.

[0107] Furthermore, when the parameter to be interpolated is the aspherical coefficient A, it is preferable that the difference in the aspherical coefficient A between adjacent intermediate microlenses 60 be greater than 0 and equal to or less than 0.2. This more effectively prevents a situation in which the surface shapes of the intermediate microlenses 60 located on the outer edge of one region 3 and the intermediate microlenses 60 located on the outer edge of the other region 3 differ significantly at the boundary between adjacent regions 3. This makes it possible to further prevent unintended defects such as diffraction, reflection, and scattering of light at the boundary between adjacent regions 3.

[0108] Furthermore, it is preferable that the parameters to be interpolated include the radius of curvature R of the microlenses 21. This allows the diffusion angle to be different for each of the multiple regions 3 provided on the diffuser 1. This makes it possible to impart a luminance distribution to the projected image projected through the diffuser 1.

[0109] Furthermore, when the parameter to be interpolated is the radius of curvature R, it is preferable that the difference in the radius of curvature R between adjacent intermediate microlenses 60 be 1 μm or more and 1 mm or less. This makes it possible to more effectively prevent a situation in which the surface shapes of the intermediate microlenses 60 located on the outer edge of one region 3 and the intermediate microlenses 60 located on the outer edge of the other region 3 differ significantly at the boundary between adjacent regions 3. This makes it possible to further prevent unintended defects such as diffraction, reflection, and scattering of light at the boundary between adjacent regions 3.

[0110] Next, the setting of lens parameters of the plurality of microlenses 21 other than the representative microlens 50, the intermediate microlens 60, and the linear microlenses 70 in each region 3 will be described. The representative microlens 50, the intermediate microlens 60, and the linear microlenses 70 are referred to as "interpolated lenses." The microlenses 21 other than the interpolated lenses are referred to as "non-interpolated lenses." The lens parameters of the non-interpolated lenses may be substantially identical to the lens parameters of the interpolated lenses located at the shortest distance from the non-interpolated lenses. The lens parameters of the non-interpolated lenses may also be substantially identical to the lens parameters of the interpolated lenses arranged in the same direction as the non-interpolated lenses. "Substantially identical" includes not only completely identical but also lens parameters that are smaller than the difference between the lens parameters of two adjacent interpolated lenses. The lens parameters of the non-interpolated lenses may be set to values ​​interpolated based on the lens parameters of the plurality of interpolated lenses located at the shortest distance from the non-interpolated lenses. The lens parameters of the non-interpolated lenses may also be set to values ​​interpolated based on the lens parameters of the plurality of interpolated lenses located within a predetermined range from the non-interpolated lenses.

[0111] A specific example of smoothly changing the lens parameters of a plurality of microlenses 21 between adjacent regions 3 will be described below with reference to Fig. 18. Fig. 18 is a diagram illustrating an example of setting the lens parameters of the microlenses 21 according to this embodiment.

[0112] In the example shown in the upper diagram of FIG. 18 (FIG. 18A), the surface (XY plane) of the substrate 10 is virtually divided into three rectangular regions 3A to 3C. In the example shown in FIG. 18A, the regions 3A to 3C are arranged in the Y direction, with region 3A adjacent to region 3B and region 3B adjacent to region 3C. A representative microlens 50A is set from among the multiple microlenses 21 arranged in region 3A. Similarly, representative microlenses 50B and 50C are set from among the multiple microlenses 21 arranged in regions 3B and 3C, respectively.

[0113] When the aspherical coefficient A is continuously changed as a lens parameter, the aspherical coefficient AA of the representative microlens 50A arranged in region 3A of the multiple regions 3 is made different from the aspherical coefficient AB of the representative microlens 50B arranged in region 3B adjacent to region 3A. Also, the aspherical coefficient AB of the representative microlens 50B arranged in region 3B is made different from the aspherical coefficient AC of the representative microlens 50C arranged in region 3C adjacent to region 3B.

[0114] Next, the aspherical coefficient A of the plurality of intermediate microlenses 60 arranged between the representative microlenses 50A and 50B is set to a value interpolated based on the aspherical coefficients AA and AB. Similarly, the aspherical coefficient A of the plurality of intermediate microlenses 60 arranged between the representative microlenses 50B and 50C is set to a value interpolated based on the aspherical coefficients AB and AC.

[0115] For example, consider a case where the aspherical coefficient A3A of the cubic term of the representative microlens 50A is set to -0.000005, the aspherical coefficient A3B of the representative microlens 50B is set to -0.000015, and the aspherical coefficient A3C of the representative microlens 50C is set to -0.000025. In this case, the aspherical coefficient A3 of the cubic term of the multiple intermediate microlenses 60 arranged between the representative microlenses 50A and 50B is set to a value interpolated between -0.000005 and -0.000015. In addition, the aspherical coefficient A3 of the cubic term of the multiple intermediate microlenses 60 arranged between the representative microlenses 50B and 50C is set to a value interpolated between -0.000015 and -0.000025.

[0116] As a result, the aspherical coefficient A3 of the third-order term of the intermediate microlenses 60 arranged between the representative microlenses 50A and 50B is set to gradually decrease from the representative microlens 50A toward the representative microlens 50B. Similarly, the aspherical coefficient A3 of the third-order term of the intermediate microlenses 60 arranged between the representative microlenses 50B and 50C is set to gradually decrease from the representative microlens 50B toward the representative microlens 50C.

[0117] Consider a case where the aspherical coefficient A3A of the cubic term of the representative microlens 50A is set to -0.000005, the aspherical coefficient A3B of the representative microlens 50B is set to -0.000015, and the aspherical coefficient A3C of the representative microlens 50C is set to -0.000005. In this case, the aspherical coefficient A3 of the cubic term of the multiple intermediate microlenses 60 arranged between the representative microlenses 50A and 50B is set to a value interpolated between -0.000005 and -0.000015. Furthermore, the aspherical coefficient A3 of the cubic term of the multiple intermediate microlenses 60 arranged between the representative microlenses 50B and 50C is set to a value interpolated between -0.000015 and -0.000005.

[0118] As a result, the aspherical coefficient A3 of the third-order term of the intermediate microlenses 60 arranged between the representative microlenses 50A and 50B is set to gradually decrease from the representative microlens 50A toward the representative microlens 50B. Similarly, the aspherical coefficient A3 of the third-order term of the intermediate microlenses 60 arranged between the representative microlenses 50B and 50C is set to gradually increase from the representative microlens 50B toward the representative microlens 50C.

[0119] 18A , the lens parameters of one or more linear microlenses 70 arranged on the virtual line VAB in regions 3A and 3B are set to values ​​interpolated based on the lens parameters of the representative microlenses 50A and 50B. The virtual line VAB is a virtual line connecting the representative microlenses 50A and 50B. For example, the aspherical coefficient A3 of the third-order term of one or more linear microlenses 70 arranged on the virtual line VAB is set to a value interpolated based on the aspherical coefficients A3A and A3B. That is, in region 3A, the aspherical coefficient A3 of the third-order term of one or more linear microlenses 70 arranged in the Y direction between the representative microlens 50A and the outer edge of region 3A is set to a value interpolated based on the aspherical coefficients A3A and A3B. Similarly, in the example shown in Figure 18A, the aspherical coefficient A3 of the third-order term of one or more linear microlenses 70 arranged on the virtual line connecting representative microlens 50B and representative microlens 50C in regions 3B and 3C is set to a value interpolated based on aspherical coefficients A3B and A3C.

[0120] 18A, the aspherical coefficients A3 of the third-order term of the microlenses 21 arranged in the Y direction change continuously, but the aspherical coefficients A3 of the third-order term of the microlenses 21 arranged in the X direction are substantially the same. Here, "substantially the same" includes not only completely the same but also a third-order aspherical coefficient A3 that is smaller than the difference between the aspherical coefficients A3 of the third-order term of two microlenses 21 adjacent in the Y direction.

[0121] Furthermore, when the radius of curvature R is continuously changed as a lens parameter, the radius of curvature RA of the representative microlens 50A arranged in region 3A is made different from the radius of curvature RB of the representative microlens 50B arranged in region 3B. Furthermore, the radius of curvature RB of the representative microlens 50B arranged in region 3B is made different from the radius of curvature RC of the representative microlens 50C arranged in region 3C.

[0122] Next, the curvature radius R of the intermediate microlenses 60 arranged between the representative microlenses 50A and 50B is set to a value interpolated based on the curvature radius RA and the curvature radius RB. Also, the curvature radius R of the intermediate microlenses 60 arranged between the representative microlenses 50B and 50C is set to a value interpolated based on the curvature radius RB and the curvature radius RC.

[0123] For example, consider a case where the radius of curvature RA of representative microlens 50A is set to 130 μm, the radius of curvature RB of representative microlens 50B is set to 150 μm, and the radius of curvature RC of representative microlens 50C is set to 170 μm. In this case, the radius of curvature R of the multiple intermediate microlenses 60 arranged between representative microlenses 50A and 50B is set to a value interpolated between 130 μm and 150 μm. Also, the radius of curvature R of the multiple intermediate microlenses 60 arranged between representative microlenses 50B and 50C is set to a value interpolated between 150 μm and 170 μm.

[0124] As a result, the radii of curvature R of the intermediate microlenses 60 arranged between the representative microlenses 50A and 50B are set to gradually increase from the representative microlens 50A toward the representative microlens 50B. Similarly, the radii of curvature R of the intermediate microlenses 60 arranged between the representative microlenses 50B and 50C are set to gradually increase from the representative microlens 50B toward the representative microlens 50C.

[0125] Also, consider a case where the radius of curvature RA of representative microlens 50A is set to 130 μm, the radius of curvature RB of representative microlens 50B is set to 100 μm, and the radius of curvature RC of representative microlens 50C is set to 170 μm. In this case, the radius of curvature R of the multiple intermediate microlenses 60 arranged between representative microlenses 50A and 50B is set to a value interpolated between 130 μm and 100 μm. Also, the radius of curvature R of the multiple intermediate microlenses 60 arranged between representative microlenses 50B and 50C is set to a value interpolated between 100 μm and 170 μm.

[0126] As a result, the radii of curvature R of the intermediate microlenses 60 arranged between the representative microlenses 50A and 50B are set to gradually decrease from the representative microlens 50A toward the representative microlens 50B. On the other hand, the radii of curvature R of the intermediate microlenses 60 arranged between the representative microlenses 50B and 50C are set to gradually increase from the representative microlens 50B toward the representative microlens 50C.

[0127] 18A , the curvature radius R of one or more linear microlenses 70 arranged on the virtual line VAB in regions 3A and 3B is set to a value interpolated based on the curvature radius RA and the curvature radius RB. That is, the curvature radius R of one or more linear microlenses 70 arranged in the Y direction between the representative microlens 50A and the outer edge of region 3A in region 3A is set to a value interpolated based on the curvature radius RA and the curvature radius RB. The rate of change in the lens parameters of the linear microlenses 70 arranged on the virtual line VAB between the representative microlens 50A and the outer edge of region 3A may be constant, for example, in the +Y direction or the −Y direction on the virtual line VAB. The rate of change in the lens parameters of one or more linear microlenses 70 arranged on the virtual line VAB between the representative microlens 50A and the outer edge of region 3A may be set to the same as the rate of change in the lens parameters in the direction from the representative microlens 50B to the representative microlens 50A. In addition, the rate of change of the lens parameters of one or more linear microlenses 70 arranged between the representative microlens 50A and the outer edge of region 3A on the virtual line VAB may be set to be the same as the rate of change of the lens parameters in the direction from the representative microlens 50A to the representative microlens 50B.

[0128] Similarly, in the example shown in Figure 18A, the curvature radii R of multiple microlenses 21 arranged on the virtual line connecting representative microlens 50B and representative microlens 50C in regions 3B and 3C are set to values ​​interpolated based on the curvature radii RB and RC.

[0129] 18A, the radii of curvature R of the microlenses 21 arranged in the Y direction change continuously, but the radii of curvature R of the microlenses 21 arranged in the X direction are substantially the same. Here, "substantially the same" includes not only completely the same but also a radius of curvature R that is smaller than the difference between the radii of curvature R of two microlenses 21 adjacent in the Y direction (the difference between the lens parameters of the two adjacent microlenses 21 set to interpolated values).

[0130] In the example shown in the lower diagram of FIG. 18 (FIG. 18B), the surface of the substrate 10 is virtually divided into four rectangular regions 3a to 3d. In the example shown in FIG. 18B, regions 3a and 3b are arranged in the X direction, and regions 3c and 3d are arranged in the X direction. Regions 3a and 3c are arranged in the Y direction, and regions 3b and 3d are arranged in the Y direction. Regions 3a and 3b, regions 3a and 3c, and regions 3a and 3d are adjacent to each other. Regions 3b and 3c, and regions 3b and 3d are adjacent to each other. Regions 3c and 3d are adjacent to each other.

[0131] Then, for example, a representative microlens 50a is set from among the plurality of microlenses 21 arranged in the region 3a. Similarly, representative microlenses 50c to 50d are set from among the plurality of microlenses 21 arranged in the regions 3c to 3d, respectively.

[0132] For example, when the radius of curvature R is continuously changed as a lens parameter, the radius of curvature Ra of the representative microlens 50a arranged in region 3a, the radius of curvature Rb of the representative microlens 50b arranged in region 3b, and the radius of curvature Rc of the representative microlens 50c arranged in region 3c are all made different from each other.Furthermore, the radius of curvature Ra of the representative microlens 50d arranged in region 3d, the radius of curvature Rb of the representative microlens 50b arranged in region 3b, and the radius of curvature Rc of the representative microlens 50c arranged in region 3c are all made different from each other.

[0133] Next, the curvature radius R of the intermediate microlenses 60 arranged in the X direction between the representative microlenses 50a and 50b is set to a value interpolated based on the curvature radius Ra and the curvature radius Rb. Also, the curvature radius R of the intermediate microlenses 60 arranged in the X direction between the representative microlenses 50c and 50d is set to a value interpolated based on the curvature radius Rc and the curvature radius Rd.

[0134] Furthermore, the curvature radius R of the intermediate microlenses 60 arranged in the Y direction between the representative microlenses 50a and 50c is set to a value interpolated based on the curvature radius Ra and the curvature radius Rc. Furthermore, the curvature radius R of the intermediate microlenses 60 arranged in the Y direction between the representative microlenses 50b and 50d is set to a value interpolated based on the curvature radius Rb and the curvature radius Rd.

[0135] 18B between representative microlenses 50a and 50d, the radius of curvature R of the intermediate microlenses 60 arranged in the diagonal direction in Fig. 18B is set to a value interpolated based on the radius of curvature Ra and the radius of curvature Rd. Also, the radius of curvature R of the intermediate microlenses 60 arranged in the diagonal direction in Fig. 19 between representative microlenses 50b and 50c is set to a value interpolated based on the radius of curvature Rb and the radius of curvature Rc.

[0136] In the example shown in FIG. 18B, the curvature radius R of one or more linear microlenses 70 arranged on the virtual line Vad in regions 3a and 3d is set to a value interpolated based on the curvature radius Ra and the curvature radius Rd. The virtual line Vad is a virtual line connecting the representative microlens 50a and the representative microlens 50d. In the example shown in FIG. 18B, the curvature radius R of one or more linear microlenses 70 arranged on the virtual line Vbc in regions 3b and 3c is set to a value interpolated based on the curvature radius Rb and the curvature radius Rc. The virtual line Vbc is a virtual line connecting the representative microlens 50b and the representative microlens 50c.

[0137] Similarly, in the example shown in Figure 18B, the curvature radius R of the linear microlenses 70 arranged on the virtual line connecting the representative microlenses 50a and 50b in regions 3a and 3b is set to a value interpolated based on the curvature radius Ra and the curvature radius Rb. In the example shown in Figure 18B, the curvature radius R of the linear microlenses 70 arranged on the virtual line connecting the representative microlenses 50a and 50c in regions 3a and 3c is set to a value interpolated based on the curvature radius Ra and the curvature radius Rc. In the example shown in Figure 18B, the curvature radius R of the linear microlenses 70 arranged on the virtual line connecting the representative microlenses 50b and 50c in regions 3b and 3c is set to a value interpolated based on the curvature radius Rb and the curvature radius Rc. In the example shown in Figure 18B, the radius of curvature R of the linear microlens 70 arranged on the virtual line connecting the representative microlens 50c and the representative microlens 50d in regions 3c and 3d is set to a value interpolated based on the radius of curvature Rc and the radius of curvature Rd.

[0138] 18B , the radius of curvature R of the non-interpolated lens may be substantially the same as the radius of curvature R of the interpolated lens located at the shortest distance from the non-interpolated lens. The radius of curvature R of the non-interpolated lens may be substantially the same as the radius of curvature R of the interpolated lens arranged in the same direction as the non-interpolated lens. The radius of curvature R of the non-interpolated lens may be set to a value interpolated based on the radii of curvature R of multiple interpolated lenses located at the shortest distance from the non-interpolated lens. The radius of curvature R of the non-interpolated lens may be set to a value interpolated based on the radii of curvature R of multiple interpolated lenses located within a predetermined range from the non-interpolated lens.

[0139] The above has described setting the lens parameters of each microlens 21 when the microlenses 21 are arranged in irregular positions on the surface of the substrate 10. However, as shown in FIG. 19 , the microlenses 21 may also be arranged in regular positions on the surface of the substrate 10. When the microlenses 21 are arranged in regular positions, multiple regions 3 and representative microlenses 50 are set, similar to when the microlenses 21 are arranged in irregular positions. The intermediate microlenses 60 and the linear microlenses 70 are set to values ​​interpolated based on the first lens parameter of the first representative microlens 50 and the second lens parameter of the second representative microlens 50, which are arranged in two mutually adjacent regions 3. The lens parameters of the non-interpolated lenses are also set in the same way as when the microlenses are arranged in irregular positions.

[0140] (S14) Determining the lens surface shape Next, the lens surface shape of each microlens 21 is determined based on the lens parameters set in S12 above. Specifically, as shown in Fig. 20, the Z coordinate position representing the surface shape of each microlens 21 is calculated based on the lens parameters set above, and the lens surface shape of the microlens 21 is set. Then, the height position in the Z direction of the set lens surface shape is adjusted so that the size on the XY plane of the set lens surface shape (e.g., opening width D) matches the size of the parameter set in S12 above (e.g., opening width D set in S12 above). Then, the horizontal cross section of the lens surface shape on the XY plane after adjusting the height position is set as a cross section at the position z = 0.

[0141] As described above, according to the method for designing the microlenses 21 of this embodiment, the lens parameters can be set so that the surface shapes of the multiple microlenses 21 change smoothly between adjacent regions 3. This makes it possible to have a distribution of optical characteristics that changes smoothly within the surface of one diffuser plate 1.

[0142] 6. Microlens manufacturing method Next, a method for manufacturing the diffuser plate 1 according to this embodiment will be described with reference to Fig. 21. Fig. 21 is a flowchart showing the method for manufacturing the diffuser plate 1 according to this embodiment.

[0143] 21, in the method for manufacturing the diffuser plate 1 according to this embodiment, first, the substrate (the substrate of the master disk or the substrate 10 of the diffuser plate 1) is cleaned (step S101). The substrate may be, for example, a roll-shaped substrate such as a glass roll, or a flat substrate such as a glass wafer or a silicon wafer.

[0144] Next, a resist is formed on the surface of the substrate after cleaning (step S103). For example, a resist layer can be formed using a resist made of a metal oxide. Specifically, a resist layer can be formed on a roll-shaped substrate by spray coating or dipping the resist. On the other hand, a resist layer can be formed on a flat substrate by subjecting the resist to various coating processes. Note that either a positive photoreactive resist or a negative photoreactive resist may be used as the resist. A coupling agent may be used to improve adhesion between the substrate and the resist.

[0145] Furthermore, the resist layer is exposed using a pattern corresponding to the shape of the microlens array 20 (step S105). This exposure process may be performed by appropriately applying a known exposure method, such as exposure using a grayscale mask, multiple exposure by overlapping multiple grayscale masks, or laser exposure using a picosecond pulse laser or a femtosecond pulse laser.

[0146] The exposed resist layer is then developed (S107). This development process forms a pattern in the resist layer. The development process can be performed by using an appropriate developer depending on the material of the resist layer. For example, if the resist layer is formed of a resist using a metal oxide, the resist layer can be alkaline-developed by using an inorganic or organic alkaline solution.

[0147] Next, the developed resist layer is used for sputtering or etching (S109), completing a master disk with the shape of the microlens array 20 formed on its surface (S111). Specifically, a glass master can be manufactured by glass etching a glass substrate using the patterned resist layer as a mask. Alternatively, a metal master can be manufactured by Ni sputtering or nickel plating (NED treatment) on the patterned resist layer to form a nickel layer to which the pattern is transferred, and then peeling off the substrate. For example, a metal master can be manufactured by forming a nickel layer to which the resist pattern is transferred by Ni sputtering to a thickness of about 50 nm or nickel plating (e.g., a Ni sulfamate bath) to a thickness of 100 μm to 200 μm.

[0148] Furthermore, by using the master master (e.g., glass master master, metal master master) completed in S111 above, a pattern is transferred (imprinted) onto a resin film or the like to create a soft mold with an inverted shape of the microlens array 20 formed on its surface (S113).

[0149] Thereafter, a soft mold is used to transfer the pattern of the microlens array 20 onto a glass substrate or a film substrate, etc. (S115), and further, a protective film, an anti-reflection film, etc. are formed as needed (S117), thereby producing the diffuser plate 1 according to this embodiment.

[0150] In the above, an example has been described in which a soft mold is manufactured (S113) using a master master (S111), and then the diffuser plate 1 is manufactured (S115) by transfer using the soft mold. However, the present invention is not limited to this example. A master master (e.g., an inorganic glass master) on which an inverted shape of the microlens array 20 is formed may be manufactured, and the diffuser plate 1 may be manufactured by imprinting using the master master. For example, the diffuser plate 1 can be manufactured by applying an acrylic photocurable resin to a base material made of PET (Polyethylene Terephthalate) or PC (Polycarbonate), transferring the pattern of the master master to the applied acrylic photocurable resin, and UV-curing the acrylic photocurable resin.

[0151] On the other hand, when the diffusion plate 1 is manufactured by directly processing the glass substrate itself, following the development process in step S107, the substrate 10 is subjected to a dry etching process using a known compound such as CF4 (S119), and then a protective film, an anti-reflection film, etc. are formed as necessary (S121), thereby manufacturing the diffusion plate 1 according to this embodiment.

[0152] It should be noted that the manufacturing method shown in FIG. 21 is merely an example, and the manufacturing method of the diffusion plate is not limited to the above example.

[0153] <7. Examples of diffuser panel applications> Next, application examples of the diffuser plate 1 according to this embodiment will be described.

[0154] The above-described diffusion plate 1 can be appropriately mounted in various devices that need to diffuse light to realize their functions. Examples of such devices include display devices such as various displays (e.g., LED and organic EL displays), projection devices such as projectors, and various lighting devices.

[0155] For example, the diffuser 1 can be applied to backlights and lenses integrated with diffusers in liquid crystal display devices, and can also be used for light shaping. The diffuser 1 can also be applied to transmission screens, Fresnel lenses, and reflective screens in projection devices. The diffuser 1 can also be applied to various lighting devices used for spot lighting, base lighting, and the like, various special lighting, and various screens such as intermediate screens and final screens. Furthermore, the diffuser 1 can be used for controlling the diffusion of light from a light source in an optical device, and can be used for controlling the light distribution of an LED light source device, the light distribution of a laser light source device, and the light distribution of light incident on various light valve systems.

[0156] The diffuser 1 can be applied to any known device that utilizes light diffusion, not limited to the above-mentioned application examples. For example, the diffuser 1 according to this embodiment can be mounted in optical devices such as various illumination optical systems, image projection optical systems, and measurement, detection, and sensing optical systems.

[0157] <8. Summary> The diffuser 1 including the microlens array 20 according to this embodiment has been described above. The diffuser 1 according to this embodiment is a microlens array 20-type diffuser 1, and includes a substrate 10 and a plurality of microlenses 21 arranged on an XY plane on at least one surface of the substrate 10. The surface on which the plurality of microlenses 21 are arranged is divided into a plurality of regions 3, and one representative microlens 50 is set for each region 3 from among the plurality of microlenses 21 arranged in each region 3. The surface shapes of the plurality of microlenses 21 are determined by lens parameters, and a first lens parameter is a lens parameter of a first representative microlens 50 arranged in a first region 3 among the plurality of regions 3, and a second lens parameter is a lens parameter of a second representative microlens 50 arranged in a second region 3 adjacent to the first region 3. The lens parameters of the plurality of microlenses 21 arranged between the first representative microlens 50 and the second representative microlens 50 are set to values ​​interpolated based on the first lens parameter and the second lens parameter.

[0158] As described above, the diffuser plate 1 according to this embodiment has a plurality of regions 3 with different optical properties, such as diffusion properties, deflection properties, and deflection angle properties, on the XY plane of the base material 10. This makes it possible to increase the degree of freedom in designing an optical device system in which the diffuser plate 1 is mounted, reduce the number of components in the optical device system, and make the optical device system more compact.

[0159] Furthermore, in the diffuser 1 according to this embodiment, the surface shapes of the microlenses 21 can be continuously changed between adjacent regions 3. This allows the diffuser 1 according to this embodiment to have a distribution of optical characteristics that smoothly changes within the surface of a single diffuser 1. Therefore, the diffuser 1 according to this embodiment can suppress unevenness and discontinuity in the brightness of diffused light, thereby achieving desired diffusion characteristics. Furthermore, the diffuser 1 according to this embodiment can avoid a situation in which the surface shapes of the microlenses 21 located on the outer edge of one region 3 differ significantly from those of the microlenses 21 located on the outer edge of the other region 3 at the boundary between adjacent regions 3. Therefore, the diffuser 1 according to this embodiment can prevent unintended problems such as diffraction, reflection, and scattering of light at the boundary between adjacent regions 3. This improves the appearance quality of the projected image projected through the diffuser 1.

[0160] In addition, the lens parameters of the multiple microlenses 21 arranged between the first representative microlens 50 and the second representative microlens 50 may be set to gradually change from the first representative microlens 50 to the second representative microlens 50.

[0161] This further prevents a situation in which the surface shapes of the microlenses 21 located on the outer edge of one region 3 differ significantly from those of the microlenses 21 located on the outer edge of the other region 3 at the boundary between adjacent regions 3. Therefore, the diffuser 1 according to this embodiment can further prevent unintended defects such as diffraction, reflection, and scattering of light at the boundary between adjacent regions 3. This further improves the appearance quality of the image projected through the diffuser 1.

[0162] The surface shape of the microlens 21 may be an aspherical shape expressed by an aspherical formula, and the lens parameters may include an aspherical coefficient A used in the aspherical formula.

[0163] This allows the bending angle of the outgoing light (diffused light) relative to the light beam of obliquely incident light or normally incident light to be different for each of the multiple regions 3 provided on the diffuser plate 1. This makes it possible to provide a diffuser plate 1 that has both a diffusing function and an angle deflection function. This allows for greater design freedom in the optical device system in which the diffuser plate 1 is installed, a reduction in the number of components in the optical device system, and a miniaturization of the optical device system. Furthermore, by varying the bending angle, it is possible to change the aspect ratio of the projected image projected through the diffuser plate 1, change the outer edge shape of the projected image, and impart brightness distribution to the projected image.

[0164] Furthermore, among the multiple microlenses 21 arranged between the first representative microlens 50 and the second representative microlens 50, the difference in aspherical coefficient A between adjacent microlenses 21 may be greater than 0 and equal to or less than 0.2.

[0165] This makes it possible to further prevent a situation in which, at the boundary between adjacent regions 3, the surface shapes of the microlenses 21 located on the outer edge of one region 3 differ significantly from those of the microlenses 21 located on the outer edge of the other region 3. Therefore, it becomes possible to further prevent unintended defects such as diffraction, reflection, and scattering of light from occurring at the boundary between adjacent regions 3.

[0166] The lens parameters may also include the radius of curvature R of the microlens 21.

[0167] This allows the diffusion angle to be different for each of the multiple regions 3 provided on the diffuser 1. Therefore, it becomes possible to impart a luminance distribution to the projected image projected through the diffuser 1.

[0168] Furthermore, among the multiple microlenses 21 arranged between the first representative microlens 50 and the second representative microlens 50, the difference in the radius of curvature R between adjacent microlenses 21 may be 1 μm or more and 1 mm or less.

[0169] This makes it possible to further prevent a situation in which, at the boundary between adjacent regions 3, the surface shapes of the microlenses 21 located on the outer edge of one region 3 differ significantly from those of the microlenses 21 located on the outer edge of the other region 3. Therefore, it becomes possible to further prevent unintended defects such as diffraction, reflection, and scattering of light from occurring at the boundary between adjacent regions 3.

[0170] Furthermore, within the first region 3 and the second region 3, the lens parameters of the multiple microlenses 21 arranged on the virtual line connecting the first representative microlens 50 and the second representative microlens 50 may be set to values ​​interpolated based on the first lens parameters and the second lens parameters.

[0171] This makes it possible to smoothly change the lens parameters of the multiple microlenses 21 arranged in the first region 3 in a direction away from the second representative microlens 50. Also, it makes it possible to smoothly change the lens parameters of the multiple microlenses 21 arranged in the second region 3 in a direction away from the first representative microlens 50. Therefore, it is possible to further improve the appearance quality of the projected image projected through the diffuser 1.

[0172] The multiple regions may be partitioned without gaps in the X and Y directions on the XY plane.

[0173] This makes it possible to suppress the zero-order transmitted light component. As a result, the microlens array 20, in which the multiple microlenses 21 are arranged adjacent to each other with no gaps between them, can further improve the diffusion performance.

[0174] Furthermore, the representative microlens 50 may be set to be one of the microlenses 21 arranged in the region 3 that is located at the center of gravity of the region 3 or in the vicinity of the center of gravity of the region 3.

[0175] This makes it possible to further prevent unintended problems such as diffraction, reflection, and scattering of light at the boundaries between the adjacent regions 3.

[0176] Furthermore, the microlenses 21 may be arranged irregularly on the XY plane.

[0177] This makes it possible to control the overlapping state of the phases of the diffused light emitted from each microlens 21. Therefore, it is possible to reduce unevenness in the intensity distribution of the diffused light due to interference and diffraction of the diffused light emitted from the multiple microlenses 21, and to distribute the diffused light uniformly. This makes it possible to have high transmittance brightness characteristics, satisfy the uniformity of the light distribution of the diffused light, and control the cutoff characteristic of the intensity distribution of the diffused light.

[0178] Furthermore, the diffuser plate 1 including the aspherical microlenses 21 according to this embodiment can be manufactured, for example, by imprinting using a master having the concave-convex structure of the microlenses 21. The master can be manufactured by high-precision drawing exposure or stepper exposure using a laser beam or a controlled light source, and photolithography techniques such as etching. For example, the master can be manufactured by electroforming a structured surface formed by lithography, or it can be manufactured as an inorganic device by glass etching. Alternatively, the master can be manufactured by precision machining techniques.

[0179] The diffuser plate 1 according to this embodiment may be provided as an inorganic device produced by glass etching, for example. Alternatively, the diffuser plate 1 may be provided as an organic imprint film replicated from a master. In this way, the diffuser plate 1 may be provided as a transfer film product or a component surface transfer product. When producing a transfer product of the diffuser plate 1, a flat master or a roll master may be used, and injection molding, melt transfer, or UV resin transfer using a photopolymerization method may be utilized. [Example]

[0180] Next, a diffuser plate according to an embodiment of the present invention will be described. Note that the following embodiment is merely an example to demonstrate the effects and feasibility of the diffuser plate according to the present invention, and the present invention is not limited to the following embodiment.

[0181] The diffusers according to Examples 1 to 3 were designed under the design conditions described below while changing the surface structure of the microlens array.

[0182] The microlens arrays according to Examples 1 to 3 were designed with the surface of each microlens being an aspherical shape expressed by mathematical formula (1). A simulation was performed to see how the diffused light distribution caused by the microlens array was achieved when incident light was normal to the microlens array.

[0183] The simulation results of Examples 1 to 3 will be described below with reference to Fig. 22 to Fig. 40. Fig. 22, Fig. 27, and Fig. 32 show the design conditions of Examples 1 to 3, Fig. 23 to Fig. 26 show the simulation results of Example 1, Fig. 28 to Fig. 31 show the simulation results of Example 2, and Fig. 33 to Fig. 40 show the simulation results of Example 3.

[0184] Figures 23, 24, 28, 29, and 33 to 36 are computer-generated bitmap data images showing the surface shape of the microlens array at the boundary of region 3. The upper figures in Figures 25, 26, 30, 31, and 37 to 40 are graphs showing the diffusion angle at the boundary of region 3. In the upper figures in Figures 25, 26, 30, 31, and 37 to 40, the vertical axis of the graph represents the intensity of the emitted light [Watts / Steradian] (optical power per unit solid angle), and the horizontal axis represents the polar angle (degrees) of the emitted light. The lower figures in Figures 25, 26, 30, 31, and 37 to 40 are images showing the simulation results of the luminance distribution of diffused light projected onto a screen surface located 100 mm away from the diffuser.

[0185] Example 1 As shown in FIG. 22 , in Example 1, the XY plane is divided into three regions in the Y direction to form region 3. That is, in Example 1, region 3A, region 3B, and region 3C are adjacent to each other in this order in the Y direction. In Example 1, the radius of curvature R of the representative microlens 50 in region 3A is set to 130 μm. The radius of curvature R of the representative microlens 50 in region 3B is set to 150 μm. The radius of curvature R of the representative microlens 50 in region 3C is set to 170 μm. The radii of curvature R of the multiple microlenses 21 arranged between the representative microlens 50 in region 3A and the representative microlens 50 in region 3B are set to values ​​obtained by spline interpolation based on the radius of curvature R of the representative microlens 50 in region 3A and the radius of curvature R of the representative microlens 50 in region 3B. The curvature radii R of the microlenses 21 arranged between the representative microlenses 50 in region 3B and the representative microlenses 50 in region 3C are set to values ​​obtained by spline interpolation based on the curvature radii R of the representative microlenses 50 in region 3B and the curvature radii R of the representative microlenses 50 in region 3C. In addition, in Example 1, the aspheric coefficients A of all the microlenses 21 arranged in region 3A, region 3B, and region 3C are set to values ​​obtained by spline interpolation based on the curvature radii R of the representative microlenses 50 in region 3B and the curvature radii R of the representative microlenses 50 in region 3C. 3y was set to −0.000015, the pitch was set to 60 μm, and the conic constant K was set to 0. Note that the pitch is the distance between the lens center coordinates of adjacent microlenses 21.

[0186] 23, at the boundary between region 3A and region 3B, the microlenses 21 located on the outer edge of region 3A and the microlenses 21 located on the outer edge of region 3B are continuously connected without any deviation in their planar shapes or any step in the height direction, and it was confirmed that the surface shapes of the microlenses 21 are continuous from region 3A to region 3B. Also, as shown in Fig. 24, at the boundary between region 3B and region 3C, the microlenses 21 located on the outer edge of region 3B and the microlenses 21 located on the outer edge of region 3C are continuously connected without any deviation in their planar shapes or any step in the height direction, and it was confirmed that the surface shapes of the microlenses 21 are continuous from region 3B to region 3C.

[0187] As shown in the upper diagram of Fig. 25, the diffusion angle was 12.8 degrees at the boundary between region 3A and region 3B. Also, as shown in the upper diagram of Fig. 26, the diffusion angle was 11.2 degrees at the boundary between region 3B and region 3C. From these results, it was confirmed that in Example 1, by smoothly changing the radius of curvature R on the XY plane, the diffusion angle on the XY plane changed smoothly.

[0188] Furthermore, as shown in the lower diagram of FIG. 25, it was confirmed that the diffused light was not bent at the boundary between region 3A and region 3B. Furthermore, as shown in the lower diagram of FIG. 26, it was confirmed that the diffused light was not bent at the boundary between region 3B and region 3C. From these results, in Example 1, the aspherical coefficient A 3y By setting is a fixed value, it was confirmed that the diffused light is not bent on the XY plane.

[0189] <Example 2> 27, in Example 2, the XY plane is divided into three regions in the X direction to form the regions 3. That is, in Example 2, the regions 3A, 3B, and 3C are adjacent to each other in this order in the X direction. In Example 2, the aspheric coefficient A of the representative microlens 50 in region 3A is 3y was set to -0.000005. The aspherical coefficient A of the representative microlens 50 in the region 3B 3y was set to -0.000015. The aspherical coefficient A of the representative microlens 50 in the region 3C 3y The aspherical coefficient A of the plurality of microlenses 21 arranged between the representative microlens 50 of the region 3A and the representative microlens 50 of the region 3B is set to −0.000025. 3y is the aspheric coefficient A of the representative microlens 50 in the region 3A. 3y and the aspherical coefficient A of the representative microlens 50 in the region 3B. 3y The aspherical coefficient A of the plurality of microlenses 21 arranged between the representative microlens 50 of the region 3B and the representative microlens 50 of the region 3C is set to a value obtained by spline interpolation based on the above. 3yis the aspheric coefficient A of the representative microlens 50 in the region 3B. 3y and the aspheric coefficient A of the representative microlens 50 in the region 3C. 3y In Example 2, the radius of curvature R of all the microlenses 21 arranged in the region 3A, the region 3B, and the region 3C was set to 150 μm, the pitch was set to 60 μm, and the conic constant K was set to 0.

[0190] 28, at the boundary between region 3A and region 3B, the microlenses 21 located on the outer edge of region 3A and the microlenses 21 located on the outer edge of region 3B are continuously connected without any deviation in their planar shapes or any step in the height direction, and it was confirmed that the surface shapes of the microlenses 21 are continuous from region 3A to region 3B. Also, as shown in Fig. 29, at the boundary between region 3B and region 3C, the microlenses 21 located on the outer edge of region 3B and the microlenses 21 located on the outer edge of region 3C are continuously connected without any deviation in their planar shapes or any step in the height direction, and it was confirmed that the surface shapes of the microlenses 21 are continuous from region 3B to region 3C.

[0191] As shown in the upper diagram of Fig. 30, the diffusion angle was 11.9 degrees at the boundary between region 3A and region 3B. Also, as shown in the upper diagram of Fig. 31, the diffusion angle was 11.9 degrees at the boundary between region 3B and region 3C. From these results, it was confirmed that in Example 2, by setting the radius of curvature R to a fixed value on the XY plane, the diffusion angle did not change on the XY plane.

[0192] Furthermore, as shown in the lower diagram of FIG. 30, it was confirmed that the diffused light is bent at the boundary between region 3A and region 3B. Furthermore, as shown in the lower diagram of FIG. 31, it was confirmed that the diffused light is bent at the boundary between region 3B and region 3C. From these results, in Example 2, it was confirmed that the aspherical coefficient A 3y It was confirmed that by smoothly changing the angle of bending, the angle of bending also changed smoothly on the XY plane.

[0193] Example 3 As shown in FIG. 32 , in Example 3, the XY plane is divided into two parts in the X direction and two parts in the Y direction to form regions 3. That is, in Example 3, regions 3A and 3B are adjacent to each other in the X direction, regions 3C and 3D are adjacent to each other in the X direction, regions 3A and 3C are adjacent to each other in the Y direction, regions B and 3D are adjacent to each other in the Y direction, regions 3A and 3D are adjacent to each other, and regions 3B and 3C are adjacent to each other. In Example 3, the radius of curvature R of the representative microlens 50 in region 3A was set to 130 μm. The radius of curvature R of the representative microlens 50 in region 3B was set to 150 μm. The radius of curvature R of the representative microlens 50 in region 3C was set to 170 μm. The radius of curvature R of the representative microlens 50 in region 3D was set to 190 μm.

[0194] Furthermore, the curvature radii R of the microlenses 21 arranged between the representative microlens 50 of region 3A and the representative microlens 50 of region 3B were set to values ​​obtained by spline interpolation based on the curvature radii R of the representative microlenses 50 of region 3A and the curvature radii R of the representative microlenses 50 of region 3B. The curvature radii R of the microlenses 21 arranged between the representative microlens 50 of region 3C and the representative microlens 50 of region 3D were set to values ​​obtained by spline interpolation based on the curvature radii R of the representative microlenses 50 of region 3C and the curvature radii R of the representative microlenses 50 of region 3D. The curvature radii R of the microlenses 21 arranged between the representative microlens 50 of region 3A and the representative microlens 50 of region 3C were set to values ​​obtained by spline interpolation based on the curvature radii R of the representative microlenses 50 of region 3A and the curvature radii R of the representative microlenses 50 of region 3C. The curvature radius R of the plurality of microlenses 21 arranged between the representative microlens 50 of region 3B and the representative microlens 50 of region 3D was set to a value obtained by spline interpolation based on the curvature radius R of the representative microlens 50 of region 3B and the curvature radius R of the representative microlens 50 of region 3D. The curvature radius R of the plurality of microlenses 21 arranged between the representative microlens 50 of region 3A and the representative microlens 50 of region 3D was set to a value obtained by spline interpolation based on the curvature radius R of the representative microlens 50 of region 3A and the curvature radius R of the representative microlens 50 of region 3D. The curvature radius R of the plurality of microlenses 21 arranged between the representative microlens 50 of region 3B and the representative microlens 50 of region 3C was set to a value obtained by spline interpolation based on the curvature radius R of the representative microlens 50 of region 3B and the curvature radius R of the representative microlens 50 of region 3C.

[0195] In Example 3, the aspherical coefficients A of all the microlenses 21 arranged in the regions 3A to 3D are 3y was set to -0.000015, the pitch was set to 60 [μm], and the conic constant K was set to 0.

[0196] As shown in Fig. 33, at the boundary between region 3A and region 3B, the microlenses 21 located on the outer edge of region 3A and the microlenses 21 located on the outer edge of region 3B are continuously connected without any deviation in their planar shapes or any difference in height, confirming that the surface shapes of the microlenses 21 are continuous from region 3A to region 3B. Also, as shown in Fig. 34, at the boundary between region 3A and region 3C, the microlenses 21 located on the outer edge of region 3A and the microlenses 21 located on the outer edge of region 3C are continuously connected without any deviation in their planar shapes or any difference in height, confirming that the surface shapes of the microlenses 21 are continuous from region 3A to region 3C. As shown in Fig. 35, at the boundary between region 3B and region 3D, the microlenses 21 located on the outer edge of region 3B and the microlenses 21 located on the outer edge of region 3D are continuously connected without any deviation in their planar shapes or any difference in height, confirming that the surface shapes of the microlenses 21 are continuous from region 3B to region 3D. Furthermore, as shown in Figure 36, at the boundary between region 3C and region 3D, the microlenses 21 located on the outer edge of region 3C and the microlenses 21 located on the outer edge of region 3D are continuously connected without any misalignment in the planar shape or any step in the height direction, and it was confirmed that the surface shape of the microlenses 21 is continuous from region 3C to region 3D.

[0197] As shown in the upper diagram of FIG. 37, the diffusion angle was 12.8 degrees at the boundary between region 3A and region 3B. As shown in the upper diagram of FIG. 38, the diffusion angle was 11.9 degrees at the boundary between region 3A and region 3C. As shown in the upper diagram of FIG. 39, the diffusion angle was 10.5 degrees at the boundary between region 3B and region 3D. As shown in the upper diagram of FIG. 40, the diffusion angle was 9.9 degrees at the boundary between region 3C and region 3D. From these results, it was confirmed that in Example 3, the diffusion angle changed smoothly on the XY plane by smoothly changing the radius of curvature R on the XY plane.

[0198] Furthermore, as shown in the lower diagram of FIG. 37, it was confirmed that the diffused light was not bent at the boundary between region 3A and region 3B. As shown in the lower diagram of FIG. 38, it was confirmed that the diffused light was not bent at the boundary between region 3A and region 3C. As shown in the lower diagram of FIG. 39, it was confirmed that the diffused light was not bent at the boundary between region 3B and region 3D. As shown in the lower diagram of FIG. 40, it was confirmed that the diffused light was not bent at the boundary between region 3C and region 3D. From these results, in Example 3, it was confirmed that the aspherical coefficient A 3y By setting is a fixed value, it was confirmed that the diffused light is not bent on the XY plane.

[0199] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention. [Explanation of symbols]

[0200] 1 Diffuser 10 Base material 20 Microlens Array 21 Microlens 3 areas 50 Representative Microlenses

Claims

1. A microlens array type diffuser plate, A substrate; a plurality of microlenses disposed on at least one surface of the substrate; Equipped with the surface on which the plurality of microlenses are disposed is divided into a plurality of regions; One representative microlens is set for each of the regions from among the plurality of microlenses arranged in the region, the surface shapes of the plurality of microlenses are determined by lens parameters; a first lens parameter, which is the lens parameter of a first representative microlens arranged in a first region among the plurality of regions, is different from a second lens parameter, which is the lens parameter of a second representative microlens arranged in a second region adjacent to the first region; A diffuser plate, wherein the lens parameters of a plurality of microlenses arranged between the first representative microlens and the second representative microlens are set to values ​​interpolated based on the first lens parameters and the second lens parameters.

2. 2. The diffuser plate of claim 1, wherein the lens parameters of the plurality of microlenses arranged between the first representative microlens and the second representative microlens are set to gradually change from the first representative microlens to the second representative microlens.

3. The surface shape of the microlens is an aspherical shape expressed by an aspherical formula, The diffuser plate according to claim 1 , wherein the lens parameters include aspheric coefficients used in the aspheric equation.

4. 4. The diffuser plate of claim 3, wherein the difference in aspherical coefficient between adjacent microlenses in the plurality of microlenses arranged between the first representative microlens and the second representative microlens is greater than 0 and less than or equal to 0.

2.

5. The diffuser plate according to claim 1 , wherein the lens parameters include a radius of curvature of the microlenses.

6. 6. The diffusion plate according to claim 5, wherein the difference in the radius of curvature between adjacent microlenses in the plurality of microlenses arranged between the first representative microlens and the second representative microlens is 1 μm or more and 1 mm or less.

7. 3. The diffuser plate according to claim 1, wherein the lens parameters of a plurality of microlenses arranged on a virtual line connecting the first representative microlens and the second representative microlens in the first region and the second region are set to values ​​interpolated based on the first lens parameters and the second lens parameters.

8. The diffusion plate according to claim 1 , wherein the plurality of regions are partitioned without gaps in the X and Y directions on an XY plane that represents the surface on which the plurality of microlenses are arranged.

9. The diffuser plate according to claim 1 , wherein the representative microlens is set to a microlens that is located at or near the center of gravity of the region among a plurality of microlenses that are located within the region.

10. The diffuser plate according to claim 1 , wherein the plurality of microlenses are irregularly arranged on the surface.

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