Diffuser, display device, projection device, lighting device, and light source for remote sensing

Abstract

To enable improvement in uniformity of intensity of diffusion light, reducing spectrum noise occurring due to a diffraction phenomenon in a cyclical structure, and to improve a light distribution property, reducing noise of 0-order diffraction light.SOLUTION: A microlens array type diffusion plate 1 emitting diffusion light in a linear way comprises: a base material 10; and a plurality of cylindrical lenses 21 that are arrayed in an X-direction on an X-Y plane of the base material 10, and made of a convex strip part or concave strip part extending in a Y-direction. An opening width D and radius of curvature R in the X-direction of respective cylindrical lenses 21 fluctuate respectively at random within a fluctuation range to be defined by fluctuation full-width rates δD and δR with a reference opening width Dk and reference radius of curvature Rk as a reference. An amount of eccentricity Ec of respective cylindrical lenses 21 fluctuates within a fluctuation range to be defined by a fluctuation full-width ratio δEc. The δD, δR and δEc satisfy an expression (1), and at least one of the δD or δR is not 0%.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a diffuser, a display device, a projection device, a lighting device, and a light source for remote sensing. [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] In such a microlens array type diffuser, the wavefronts of light from each microlens interfere with each other, resulting in diffraction waves due to the periodic structure of the microlens arrangement, which causes unevenness in the intensity distribution of the diffused light. For this reason, technologies have been proposed to reduce unevenness in the intensity distribution of the diffused light caused by interference and diffraction by varying the arrangement of the microlenses, the shape of the lens surface, and the shape of the opening.

[0004] For example, Patent Document 1 describes a diffuser plate having a plurality of microlenses regularly arranged in a rectangular lattice pattern on its main surface, in which the microlenses have different cross-sectional shapes and no axis of symmetry. Patent Document 2 also describes a diffuser plate in which the vertices of the microlenses arranged in a rectangular lattice pattern are shifted from the lattice points of a reference lattice. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2016 / 051785 [Patent Document 2] International Publication No. 2015 / 182619 Summary of the Invention [Problem to be solved by the invention]

[0006] An example of the microlens array type diffuser is a diffuser that diffuses incident light linearly in a specific direction and emits linearly diffused light. Such a diffuser generally has a microlens array structure in which multiple cylindrical lenses of the same shape are periodically arranged.

[0007] However, in such an array structure in which multiple cylindrical lenses of the same shape are periodically arranged, the diffraction phenomenon of the periodic structure generates spectral diffracted light (spectral noise), which reduces the uniformity of the intensity of the linearly diffused light.Furthermore, the generation of high-intensity zero-order diffracted light (noise) makes it difficult to properly distribute the diffused light in a specific direction, which reduces the light distribution of the linearly diffused light in that direction.

[0008] Therefore, the present invention has been made in consideration of the above circumstances, and an object of the present invention is to reduce the spectral noise generated by the diffraction phenomenon of the periodic structure in a microlens array type diffuser plate that emits linear diffused light, thereby improving the uniformity of the intensity of the linear diffused light, and to reduce the noise of the zeroth order diffracted light, thereby improving the light distribution. [Means for solving the problem]

[0009] In order to solve the above problem, according to one aspect of the present invention, A microlens array type diffuser that emits linearly diffused light, A substrate; a plurality of cylindrical lenses arranged in the X direction on an XY plane on at least one surface of the substrate, the lenses comprising convex or concave ridge portions extending in a Y direction perpendicular to the X direction; Equipped with the aperture width D [μm] in the X direction of each of the cylindrical lenses varies randomly within a variation range defined by a variation total width rate δD [%] with respect to a reference aperture width Dk [μm]; The radius of curvature R [μm] of each cylindrical lens varies randomly within a variation range defined by a full width variation rate δR [%] based on a reference radius of curvature Rk [μm], The eccentricity Ec [μm] of each cylindrical lens varies randomly within a variation range defined by a full width variation rate ΔEc [%], The ΔD [%], the ΔR [%], and the ΔEc [%] are expressed as follows: Formula (2) and the δD [%] and The above δR [%] both is not 0[%] Ku , The ΔD [%] is 7% or more and less than 30%, The ΔR [%] is equal to or greater than 7% and less than 30%, The ΔEc [%] is 7% or more and 30% or less. A diffuser plate is provided.

[0010]

number

[0011] however, The total fluctuation width ratio δD [%] is the ratio of the total fluctuation width ΔD [μm] to the reference opening width Dk [μm] (δD = ΔD / Dk × 100), The total fluctuation width ΔD [μm] is the upper limit dD of the fluctuation amount dD of the opening width D. MAX and the lower limit dD MIN and the difference (ΔD=dD MAX -dD MIN ), The total fluctuation width ratio δR [%] is the ratio of the total fluctuation width ΔR to the reference curvature radius Rk (δR = ΔR / Rk × 100), The total fluctuation width ΔR [μm] is the upper limit dR of the fluctuation amount dR of the radius of curvature R. MAX and the lower limit dR MIN and the difference (ΔR=dR MAX -dR MIN), the eccentricity amount Ec is a deviation amount in the X direction of the vertex position of each of the cylindrical lenses with respect to the center position of each of the cylindrical lenses in the X direction, The total fluctuation width rate ΔEc [%] is the ratio of the total fluctuation width ΔEc to the reference opening width Dk (ΔEc = ΔEc / Dk × 100), The total fluctuation width ΔEc [μm] is the upper limit Ec of the eccentricity amount Ec MAX and lower limit Ec MIN and the difference (ΔEc=Ec MAX -Ec MIN ).

[0014] The ΔD [%], the ΔR [%], and the ΔEc [%] satisfy the following formula (3): death, The ΔEc [%] is 30% or less. This may be done.

[0015]

number

[0019] In order to solve the above-mentioned problems, according to another aspect of the present invention, there is provided a display device including the above-mentioned diffusion plate.

[0020] In order to solve the above problem, according to another aspect of the present invention, there is provided a projection device including the above-mentioned diffuser plate.

[0021] In order to solve the above problem, according to another aspect of the present invention, there is provided an illumination device including the above-mentioned diffusion plate.

[0022] In order to solve the above problem, according to another aspect of the present invention, there is provided a light source for remote sensing comprising the above-mentioned diffuser plate. [Effects of the Invention]

[0023] As described above, according to the present invention, in a microlens array type diffuser plate that emits linear diffused light, the spectral noise generated by the diffraction phenomenon of the periodic structure can be reduced, improving the uniformity of the intensity of the linear diffused light, and the noise of the zeroth-order diffracted light can be reduced, improving the light distribution. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is an explanatory diagram schematically illustrating a diffusion plate according to an embodiment of the present invention. [Figure 2] 3A and 3B are an enlarged plan view and an enlarged cross-sectional view schematically showing the diffusion plate according to the embodiment. [Figure 3] FIG. 2 is a perspective view schematically showing a microlens array of the diffuser plate according to the embodiment. [Figure 4] 10A and 10B are an enlarged plan view and an enlarged cross-sectional view schematically showing a diffusion plate according to a modified example of the embodiment. [Figure 5] FIG. 10 is a perspective view schematically showing a microlens array of a diffuser plate according to a modified example of the embodiment. [Figure 6] FIG. 2 is an enlarged cross-sectional view schematically showing an eccentric state of the cylindrical lens according to the embodiment. [Figure 7] 10 is a graph showing an example of the intensity of diffracted light due to the periodic structure of a microlens array. [Figure 8] 10 is a graph showing an example of light distribution characteristics of a diffuser plate according to the embodiment. [Figure 9] 10 is a flowchart showing a method for manufacturing the diffuser plate according to the embodiment. [Figure 10] FIG. 10 is an explanatory diagram of a diffusion plate according to Comparative Example 1. [Figure 11] FIG. 10 is an explanatory diagram of a diffusion plate according to Comparative Example 2. [Figure 12] FIG. 10 is an explanatory diagram of a diffusion plate according to Comparative Example 3. [Figure 13] FIG. 10 is an explanatory diagram of a diffusion plate according to Comparative Example 4. [Figure 14] FIG. 10 is an explanatory diagram of a diffusion plate according to Comparative Example 5. [Figure 15] FIG. 10 is an explanatory diagram of a diffusion plate according to Comparative Example 6. [Figure 16] FIG. 13 is an explanatory diagram of a diffusion plate according to Comparative Example 7. [Figure 17] FIG. 13 is an explanatory diagram of a diffusion plate according to Comparative Example 8. [Figure 18] FIG. 2 is an explanatory diagram of a diffusion plate according to the first embodiment. [Figure 19] FIG. 10 is an explanatory diagram of a diffusion plate according to a second embodiment. [Figure 20] FIG. 10 is an explanatory diagram of a diffusion plate according to a third embodiment. [Figure 21] FIG. 10 is an explanatory diagram of a diffusion plate according to a fourth embodiment. [Figure 22] FIG. 10 is an explanatory diagram of a diffusion plate according to a fifth embodiment. [Figure 23] FIG. 10 is an explanatory diagram of a diffusion plate according to a sixth embodiment. [Figure 24] FIG. 13 is an explanatory diagram of a diffusion plate according to a seventh embodiment. [Figure 25] FIG. 13 is an explanatory diagram of a diffusion plate according to an eighth embodiment. [Figure 26] FIG. 13 is an explanatory diagram of a diffusion plate according to a ninth embodiment. [Figure 27] FIG. 20 is an explanatory diagram of a diffusion plate according to a tenth embodiment. [Figure 28] FIG. 20 is an explanatory diagram of a diffusion plate according to an eleventh embodiment. [Figure 29] FIG. 23 is an explanatory diagram of a diffusion plate according to a twelfth embodiment. [Figure 30] FIG. 22 is an explanatory diagram of a diffusion plate according to a thirteenth embodiment. [Figure 31] FIG. 1 is an explanatory diagram of a diffusion plate according to Reference Example 1. [Figure 32] FIG. 10 is an explanatory diagram of a diffusion plate according to Reference Example 2. [Figure 33] FIG. 10 is an explanatory diagram of a diffusion plate according to Reference Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0025] 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.

[0026] <1. Overview of the diffuser> First, an overview of the diffusion plate according to the embodiment of the present invention will be described.

[0027] The diffuser plate according to the present embodiment, which will be described in detail below, is a microlens array-type diffuser plate with the function of uniformly diffusing light. This diffuser plate includes a substrate and a microlens array formed on an XY plane on at least one surface (principal surface) of the substrate. The microlens array is composed of a plurality of microlenses arranged and developed on the XY plane. The microlenses according to the present embodiment are made of cylindrical lenses having a substantially cylindrical shape. The cylindrical lenses are made of convex or concave ridges extending in the Y direction perpendicular to the X direction, and have an opening width D in the X direction of, for example, several tens of μm. The cylindrical lenses have, for example, a lens surface with a substantially semi-cylindrical shape. A microlens array is formed by periodically arranging a plurality of cylindrical lenses in the X direction on the XY plane.

[0028] In the diffuser plate according to this embodiment, the X-direction aperture widths D (corresponding to the X-direction pitch (period) and lens diameter) of the multiple cylindrical lenses arranged in the X direction vary randomly (irregularly) so as to be different from one another. Furthermore, the X-direction curvature radii R of the multiple cylindrical lenses vary randomly (irregularly) so as to be different from one another. In addition, the planar position in the X direction of the apex of each microlens is decentered from the X-direction central position of each microlens. At this time, the eccentricity amounts Ec of the multiple cylindrical lenses vary randomly (irregularly) so as to be different from one another. Furthermore, the Z-direction height positions of the apexes of the multiple cylindrical lenses (positions in the thickness direction of the diffuser plate) also vary randomly (irregularly) and are different from one another.

[0029] In this manner, in this embodiment, the aperture width D, radius of curvature R, decentering amount Ec, etc. of each cylindrical lens are randomly varied. As a result, the surface shape of each cylindrical lens varies randomly, resulting in different surface shapes among multiple cylindrical lenses. Furthermore, the aperture width D, radius of curvature R, and decentering amount Ec of each cylindrical lens are randomly varied within a variation range defined by predetermined full width fluctuation ratios δD, δR, and δEc [%], respectively. Furthermore, the full width fluctuation ratios δD, δR, and δEc [%] are set to satisfy predetermined relational expressions. Details of the full width fluctuation ratios δD, δR, and δEc [%] and these relational expressions will be described later.

[0030] As described above, the diffuser plate according to this embodiment randomly varies each variable element of the multiple microlenses (cylindrical lenses) to achieve a highly random three-dimensional surface structure of the microlens array. Furthermore, by satisfying the relational expressions using the full width variation ratios δD, δR, and δEc as parameters, the variations in the aperture width D, radius of curvature R, and eccentricity Ec are also adjusted within suitable variation ranges. This reduces zero-order diffracted light (noise) in the uniaxial linear diffused light emitted from the diffuser plate, improving the light distribution in the X direction. It also reduces spectral noise caused by the periodic structure of the microlens array, improving the intensity uniformity of the diffused light. Spectral noise is noise consisting of periodic peaks of diffracted light generated by diffraction caused by the periodic structure of the microlens array.

[0031] Therefore, according to this embodiment, it is possible to suitably control the overlapping state of the phases of light emitted from each microlens (cylindrical lens). As a result, it is possible to achieve excellent light distribution, anisotropy of light distribution in the X direction, and cutoff of the intensity distribution of diffused light in the X direction by suppressing noise of the zeroth-order diffracted light while satisfying the uniformity of light distribution in the X direction of uniaxial linear diffused light. Below, a diffuser plate having the above-mentioned characteristics will be described in detail.

[0032] <2. Overall structure of the diffuser> First, the overall configuration of a diffuser plate 1 according to one embodiment of the present invention and the layout pattern of microlenses will be described with reference to Fig. 1. Fig. 1 is an explanatory diagram that schematically shows the diffuser plate 1 according to this embodiment.

[0033] The diffuser plate 1 according to this embodiment is a microlens array type diffuser plate, and includes a microlens array 20 consisting of a plurality of microlenses (cylindrical lenses 21) arranged on a substrate. As shown in FIG. 1, the microlens array 20 of the diffuser plate 1 is composed of a plurality of unit cells 3. The unit cells 3 are a basic arrangement pattern of microlenses. A plurality of microlenses (cylindrical lenses 21) are arranged on the surface of each unit cell 3 in a predetermined layout pattern (arrangement pattern).

[0034] 1 shows an example in which the shape of the unit cells 3 constituting the diffuser plate 1 is rectangular, particularly square. However, the shape of the unit cells 3 is not limited to the example shown in Fig. 1, and may be any shape, such as an equilateral triangle or a regular hexagon, as long as it can fill the surface (XY plane) of the diffuser plate 1 without gaps.

[0035] 1, a plurality of square unit cells 3 are repeatedly arranged vertically and horizontally (X and Y directions) on the surface of the diffuser plate 1. The number of unit cells 3 constituting the diffuser plate 1 according to this embodiment is not particularly limited, and the diffuser plate 1 may be composed of one unit cell 3 or multiple unit cells 3. Furthermore, in the diffuser plate 1 according to this embodiment, unit cells 3 having different surface structures may be repeatedly arranged, or unit cells 3 having the same surface structure may be repeatedly arranged.

[0036] Furthermore, between the unit cells 3, 3, the layout pattern (arrangement pattern) of the multiple microlenses (cylindrical lenses 21) provided within the unit cells 3 is continuous in the arrangement direction of the unit cells 3 (in other words, the array arrangement direction). The microlens array 20 is formed by arranging the unit cells 3 without gaps while maintaining the continuity of the microlenses at the boundaries between the multiple unit cells 3, 3. Here, the continuity of the microlenses means that, of two adjacent unit cells 3, the microlenses located on the outer edge of one unit cell 3 and the microlenses located on the outer edge of the other unit cell 3 are continuously connected without any misalignment in the planar shape or any step in the height direction.

[0037] As described above, in the diffuser 1 according to this embodiment, the unit cells 3 (basic structure) of the microlens array 20 are arranged without gaps while maintaining the continuity of their boundaries, thereby forming the microlens array 20. This prevents unintended problems such as diffraction, reflection, and scattering of light at the boundaries between the unit cells 3, 3, and enables the diffuser 1 to achieve the desired light distribution characteristics.

[0038] <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. 2 to 5. Fig. 2 is an enlarged plan view and an enlarged cross-sectional view schematically showing the diffuser plate 1 according to this embodiment. Fig. 3 is a perspective view schematically showing the microlens array 20 of the diffuser plate 1 according to this embodiment. Fig. 4 is an enlarged plan view and an enlarged cross-sectional view schematically showing the diffuser plate 1 according to a modified example of this embodiment. Fig. 5 is a perspective view schematically showing the microlens array 20 of the diffuser plate 1 according to a modified example of this embodiment.

[0039] As shown in FIGS. 2 to 5, 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.

[0040] 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 shown in FIGS. 2 and 4 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 of the device in which the diffuser plate 1 is to be mounted.

[0041] The substrate 10 is a transparent substrate that can transmit light and has translucency. The substrate 10 is made of a material that can be considered transparent in the wavelength band of light that enters 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 corresponding to visible light.

[0042] 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.

[0043] 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 (single lenses) arranged on the surface of the substrate 10. In this embodiment, as shown in FIG. 2, the microlens array 20 is formed on one 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.

[0044] The microlenses are minute optical lenses on the order of, for example, several tens of μm. The microlenses constitute single lenses of the microlens array 20. The microlenses according to this embodiment are constituted by cylindrical lenses 21, as shown in FIGS. 2 to 5.

[0045] The cylindrical lens 21 is an optical lens having a substantially semi-cylindrical (cylindrical) lens surface. The cylindrical lens 21 has a function of converting incident light such as laser light into linear diffused light, for example.

[0046] The surface shape of each cylindrical lens 21 is not particularly limited as long as it is a curved shape that includes a partial curved surface component of an approximately semi-cylindrical shape (a semi-cylindrical curved surface component). An approximately semi-cylindrical shape means a substantial semi-cylindrical shape, and includes not only a strict semi-cylindrical shape but also a shape that is distorted from a semi-cylindrical shape. The surface shape of the cylindrical lens 21 may be, for example, a curved shape that includes only a cylindrical component, a curved shape that includes a cylindrical component and a non-cylindrical component, or a curved shape that includes only a non-cylindrical component.

[0047] The cylindrical lenses 21 may be a convex structure (convex lens) formed so as to protrude in the thickness direction of the diffuser plate 1, as shown in Figures 2 and 3, or may be a concave structure (concave lens) formed so as to be recessed in the thickness direction of the diffuser plate 1, as shown in Figures 4 and 5. In this way, the cylindrical lenses 21 may be either a convex structure (convex lens) or a concave structure (concave lens) depending on the desired optical characteristics of the diffuser plate 1.

[0048] 2 and 3, the cylindrical lens 21 according to this embodiment is a microlens having a convex structure, which is made up of a slender convex ridge extending in the Y direction. A plurality of cylindrical lenses 21 made up of the convex ridge ridges are arranged in the X direction to form a microlens array 20 made up of microlenses with a convex structure.

[0049] 4 and 5, the cylindrical lenses 21 according to a modified example of this embodiment are microlenses having a concave structure, each of which is made up of a thin, concave ridge extending in the Y direction. A plurality of cylindrical lenses 21 made up of concave ridges are arranged in the X direction to form a microlens array 20 made up of microlenses with a concave structure.

[0050] In either the convex or concave structure, the opening width D in the X direction, the radius of curvature R, and the amount of decentering Ec of the lens apex of each cylindrical lens 21 vary randomly within a predetermined variation range, so that the surface shapes of the multiple cylindrical lenses 21 are different from one another.

[0051] In the microlens array 20 according to this embodiment, the opening width D in the X direction of the plurality of cylindrical lenses 21 varies randomly within a predetermined variation range. Therefore, the arrangement pitch of the cylindrical lenses 21 in the X direction is not constant, and the plurality of cylindrical lenses 21 are not arranged regularly at a predetermined pitch (period) in the X direction. However, the plurality of cylindrical lenses 21 are arranged so as to extend in the Y direction and be parallel to one another, and the microlens array 20 as a whole is arranged to a certain degree regularly (hereinafter referred to as "quasi-regularly").

[0052] As shown in FIGS. 2 to 5, the plurality of cylindrical lenses 21 are preferably arranged densely in the X direction so that they are adjacent to each other with no gaps. In other words, the plurality of cylindrical lenses 21 are preferably arranged continuously in the X direction so that no gaps (flat portions) exist at the boundaries between adjacent cylindrical lenses 21. By arranging the cylindrical lenses 21 on the substrate 10 with no gaps (in other words, arranging the cylindrical lenses 21 so that the packing ratio is 100%), it is possible to suppress the component of the incident light that is transmitted directly without being scattered by the surface of the diffuser plate 1 (hereinafter also referred to as the "zeroth-order transmitted light component"). As a result, by arranging the plurality of cylindrical lenses 21 adjacent to each other with no gaps, it is possible to further improve the diffusion performance of the microlens array 20 according to this embodiment.

[0053] In order to suppress the zero-order transmitted light component, the filling rate of the cylindrical lenses 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 portion on the surface (XY plane) of the substrate 10 that is occupied by the multiple cylindrical lenses 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.

[0054] However, in the actual manufacture of the microlens array 20, the curved surfaces of the multiple cylindrical lenses 21 are continuously connected, so the area near the inflection point at the boundary between adjacent cylindrical lenses 21 may become substantially flat. In such a case, it is preferable that the width in the X direction of the substantially flat area near the inflection point at the boundary between the cylindrical lenses 21 (the width in the X direction of the boundary line between the cylindrical lenses 21) is, for example, 1 μm or less. This allows the zero-order transmitted light component to be sufficiently suppressed.

[0055] In this embodiment, the surface shape (three-dimensional curved shape) and planar shape (two-dimensional shape projected onto the XY plane of the substrate 10) of the cylindrical lenses 21 vary randomly. As shown in FIGS. 2 and 4 , the planar shape of the cylindrical lenses 21 (the outer shape of the cylindrical lenses 21 projected onto the XY plane) is generally a strip-like, approximately rectangular shape extending elongatedly in the Y direction. The surface shapes and planar shapes of the multiple cylindrical lenses 21 are different from one another. The reason the multiple cylindrical lenses 21 have different shapes from one another is that the aperture width D, curvature radius R, and eccentricity Ec of the lens apex of each cylindrical lens 21 vary randomly within a predetermined variation range. Note that the method for varying the aperture width D, curvature radius R, and eccentricity Ec of the cylindrical lenses 21 according to this embodiment will be described in detail later.

[0056] As described above, in this embodiment, the aperture width D, radius of curvature R, and amount of eccentricity Ec of each cylindrical lens 21 vary randomly and have variations. The phase distribution of the optical aperture of each cylindrical lens 21 differs depending on the orientation. The multiple cylindrical lenses 21 are continuously arranged in the X direction so as to overlap one another on the surface of the substrate 10, and the radius of curvature R, aperture width D, and amount of eccentricity Ec of each cylindrical lens 21 vary randomly. As a result, the shapes (surface shape and planar shape) of the multiple cylindrical lenses 21 are different from one another. Therefore, the multiple cylindrical lenses 21 have various shapes as shown in FIGS. 2 to 5, and many of them have cross-sectional shapes that are asymmetric in the X direction. As a result, the periodic structure of the microlens array 20 is disrupted, thereby reducing spectral noise caused by the periodic structure and noise such as zero-order diffracted light. Therefore, the diffuser 1 according to this embodiment can improve the light distribution and uniformity of the linear diffused light emitted from the microlens array 20 compared to conventional microlens arrays.

[0057] <4. Parameter definition> Next, definitions of various parameters relating to the microlens array 20 according to this embodiment will be described.

[0058] (A) Parameters related to opening width (A1) Opening width D [μm]: Variation The aperture width D is the aperture width in the X direction of each cylindrical lens 21 (see FIGS. 2 to 5). The aperture width D is the actual aperture width that varies randomly for each cylindrical lens 21, and is a fluctuating value. The aperture width D corresponds to the lens diameter and pitch (period) of the cylindrical lenses 21 in the X direction.

[0059] (A2) Reference opening width Dk [μm]: fixed value The reference aperture width Dk is the aperture width in the X direction of the reference shape of the cylindrical lens 21. The reference aperture width Dk is a fixed value set when the microlens array 20 is designed. The reference aperture width Dk serves as a reference value (central value of variation) when the aperture width D is varied.

[0060] (A3) Amount of variation in opening width dD [μm]: Variation value The aperture width variation dD is the difference between the “aperture width D [μm]” and the “reference aperture width Dk [μm].” dD is a variation value that varies randomly for each cylindrical lens 21. dD=D-Dk

[0061] (A4) Variation rate of opening width K D [±%]: Fluctuation value Opening width fluctuation rate K D teeth 、 This is the ratio (percentage) of the "variation in opening width dD [μm]" to the "reference opening width Dk [μm]". K D is a variable value that varies randomly for each cylindrical lens 21. K D =dD / Dk×100

[0062] (A5) Total width of aperture width fluctuation ΔD [μm]: fixed value The total width of fluctuation of the opening width ΔD is the upper limit dD of the fluctuation amount dD of the opening width. MAX [μm] and lower limit dD MINΔD is a fixed value set at the time of designing the microlens array 20. ΔD represents the maximum fluctuation width [μm] when the opening width D is varied. ΔD=dD MAX -dD MIN

[0063] (A6) Opening width fluctuation rate δD [%]: fixed value The aperture width variation total width rate δD is the ratio (percentage) of the "aperture width variation total width ΔD [μm]" to the "reference aperture width Dk [μm]". δD is a fixed value set when the microlens array 20 is designed. δD is the ratio of the maximum variation width when the aperture width D is varied (ratio to Dk), and represents the variation range of D. δD is zero or a positive value. δD=ΔD / Dk×100

[0064] (B) Parameters related to the radius of curvature (B1) Radius of curvature R [μm]: Variation value The radius of curvature R is the radius of curvature in the X direction of each cylindrical lens 21 (see FIGS. 2 to 5). The radius of curvature R is the actual radius of curvature that varies randomly for each cylindrical lens 21, and is a fluctuating value. The radius of curvature R represents the radius of curvature of the curved lens surface in the cross section of the cylindrical lens 21 in the X direction.

[0065] (B2) Reference radius of curvature Rk [μm]: Fixed value The reference radius of curvature Rk is the radius of curvature in the X direction of the reference shape of the cylindrical lens 21. The reference radius of curvature Rk is a fixed value that is set when the microlens array 20 is designed. The reference radius of curvature Rk serves as a reference value (center value of variation) when the radius of curvature R is varied.

[0066] (B3) Variation in radius of curvature dR [μm]: Variation value The variation amount dR of the radius of curvature is the difference between the “radius of curvature R [μm]” and the “reference radius of curvature Rk [μm].” dR is a variation value that varies randomly for each cylindrical lens 21. dR=R-Rk

[0067] (B4) Rate of variation of radius of curvature K R [±%]: Fluctuation value Curvature radius fluctuation rate K R teeth 、 It is the ratio (percentage) of the "variation amount of the radius of curvature dR [μm]" to the "reference radius of curvature Rk [μm]". K R is a variable value that varies randomly for each cylindrical lens 21. K R =dR / Rk×100

[0068] (B5) Total width of variation of curvature radius ΔR [μm]: fixed value The total variation width ΔR of the radius of curvature is the upper limit dR of the variation amount dR of the radius of curvature. MAX [μm] and lower limit dR MIN ΔR is a fixed value set at the time of designing the microlens array 20. ΔR represents the maximum fluctuation width [μm] when the radius of curvature R is varied. ΔR=dR MAX -dR MIN

[0069] (B6) Curvature radius fluctuation full width rate δR [%]: fixed value The full width variation rate δR of the radius of curvature is the ratio (percentage) of the "full width variation of the radius of curvature ΔR [μm]" to the "reference radius of curvature Rk [μm]". δR is a fixed value set when the microlens array 20 is designed. δR is the ratio of the maximum variation width when the radius of curvature R is varied (ratio to Rk), and represents the variation range of R. δR is zero or a positive value. δR=ΔR / Rk×100

[0070] (C) Eccentricity parameters (C1) Eccentricity Ec [μm]: Fluctuation value The decentering amount Ec is the amount of deviation in the X direction of the apex position of each cylindrical lens 21 (hereinafter also referred to as the lens apex position 22) from the center position (center point 23) of each cylindrical lens 21 in the X direction (see FIG. 6). The decentering amount Ec is the actual amount of decentering that varies randomly for each cylindrical lens 21, and is a fluctuation value. Note that when Ec is a positive value, this means that the lens apex position 22 is deviated from the center position (center point 23) in the positive direction in the X direction. On the other hand, when Ec is a negative value, this means that the lens apex position 22 is deviated from the center position (center point 23) in the negative direction in the X direction. In this way, the decentering amount Ec can be either a positive value or a negative value.

[0071] (C2) Standard eccentricity Eck [μm]: Fixed value The reference eccentricity amount Eck is the eccentricity amount of the reference shape of the cylindrical lens 21. In this embodiment, the reference eccentricity amount Eck is 0 μm, but Eck may be set to a value other than 0. The reference eccentricity amount Eck is a reference value (fluctuation center value) when fluctuating the eccentricity amount Ec.

[0072] (C3) Eccentricity fluctuation rate K Ec [±%]: Fluctuation value Eccentricity fluctuation rate K Ec teeth 、 This is the ratio (percentage) of "eccentricity Ec [μm]" to "reference opening width Dk [μm]". K Ec is a variable value that varies randomly for each cylindrical lens 21. K Ec =Ec / Dk×100

[0073] (C4) Total fluctuation width of eccentricity ΔEc [μm]: fixed value The total fluctuation width ΔEc of the eccentricity is the upper limit Ec of the eccentricity Ec MAX [μm] and lower limit Ec MIN ΔEc is a fixed value that is set when the amount of eccentricity Ec is varied. ΔEc represents the maximum variation width [μm] when the amount of eccentricity Ec is varied. ΔEc=Ec MAX -Ec MIN

[0074] (C5) Eccentricity fluctuation full width rate δEc [%]: fixed value The decentering amount fluctuation full width rate δEc is the ratio (percentage) of the "decentration amount fluctuation full width ΔEc [μm]" to the "reference aperture width Dk [μm]". δEc is a fixed value set when the microlens array 20 is designed. δEc is the ratio (to Dk) of the maximum fluctuation width when the decentering amount Ec is varied, and represents the fluctuation range of Ec. δEc is zero or a positive value. δEc=ΔEc / Dk×100

[0075] (D) Other parameters (D1) Square root sum of squares K [%]: fixed value The square root of the sum of squares K is the square root of the sum of squares of the above-mentioned full width fluctuation ratios δD, δR, and δEc. The square root of the sum of squares K [%] is expressed by the following equation (10). K is a fixed value set when the microlens array 20 is designed. K defines the range of fluctuation when the aperture width D, the radius of curvature R, and the amount of decentering Ec are varied.

[0076]

number

[0077] (D2) Lens maximum height difference Zmax [μm] Zmax represents the maximum height difference of the microlens array surface within the area of ​​the reference pattern of the microlens array 20 (for example, a rectangular area such as the unit cell 3 shown in FIG. 1). The reference pattern may be, for example, a rectangular area with one side measuring 0.8 mm or 4 mm. The microlens array 20 is constructed by tiling this reference pattern on the XY plane of the substrate 10 to increase the area. Therefore, Zmax also corresponds to the maximum height difference of the lens surfaces across the entire microlens array 20.

[0078] 5. Microlens placement method Next, a method for arranging microlenses according to this embodiment will be described in detail with reference to Figures 2 to 6. Figure 6 is an enlarged cross-sectional view that schematically shows the decentered state of cylindrical lenses 21 according to this embodiment.

[0079] The microlens array 20 in which a plurality of cylindrical lenses 21 having the above-described characteristics are arranged can be realized by the microlens arrangement method described below.

[0080] First, a reference state (hereinafter also referred to as "initial arrangement state") is set in which a plurality of cylindrical lenses 21 having a reference shape are arranged in the X direction on the XY plane of the substrate 10. Next, this initial arrangement state is changed to a state (hereinafter also referred to as "varied arrangement state") in which the shapes of the cylindrical lenses 21 (for example, the opening width D in the X direction of the cylindrical lenses 21, the radius of curvature R, the position of the vertex 22, etc.) are randomly varied. Hereinafter, this arrangement method of the cylindrical lenses 21 will be referred to as the "reference arrangement method."

[0081] In this reference arrangement method, the cylindrical lenses 21 are arranged in a regular reference state, and then randomness is imparted to the shape and arrangement of the cylindrical lenses 21. Therefore, when the microlens array 20 in the final, fluctuating arrangement state is viewed somewhat macroscopically, the arrangement of the cylindrical lenses 21 is such that the regular initial arrangement state can be estimated to some extent. This reference arrangement method will be described in detail below.

[0082] (1) Initial arrangement of the cylindrical lenses 21 In the reference arrangement method according to this embodiment, first, an initial arrangement state is set as a reference for arranging the cylindrical lenses 21. Specifically, in the initial arrangement state, a plurality of cylindrical lenses 21 having the same reference shape are regularly arranged in the X direction at the same reference aperture width Dk (same pitch) on an XY plane of the reference surface. In this initial arrangement state, the aperture width D in the X direction of the plurality of cylindrical lenses 21 is the same reference aperture width Dk, and the radius of curvature R is the same reference radius of curvature Rk. Furthermore, in the initial arrangement state, the vertex 22 of each cylindrical lens 21 is not decentered in the X direction (i.e., the amount of decentering Ec = 0 μm), as shown by the dashed-dotted line in FIG. 6 , and is arranged at the position of the center point 23 of each cylindrical lens 21 in the X direction (reference position).

[0083] In the initial arrangement state, the planar shape of each cylindrical lens 21 is a strip-like rectangle elongated in the Y direction (see FIGS. 2 and 4). The position of the vertex 22 of each cylindrical lens 21 (lens vertex position 22) coincides with the center point 23 of the reference shape of a non-decentered cylindrical lens (see FIG. 6). In this initial arrangement state, the aperture width D in the X direction of each cylindrical lens 21 coincides with the reference aperture width Dk (arrangement pitch in the X direction) (i.e., dD = 0 μm). In addition, the surface shape of each cylindrical lens 21 in the initial arrangement state is a predetermined reference shape (for example, a semi-cylindrical shape having a reference radius of curvature Rk).

[0084] (2) First variable arrangement state in which the opening width D is varied After setting the initial arrangement state as described above, a first varied arrangement state is set in which the surface shape of the cylindrical lenses 21 is varied by randomly varying the aperture width D in the X direction of the cylindrical lenses 21. The aperture width D is the aperture width in the X direction of the cylindrical lenses 21 cut at a cross section in the XZ plane (lens diameter in the X direction), and corresponds to the arrangement pitch in the X direction.

[0085] The method for randomly varying the aperture width D of the cylindrical lens 21 is, for example, as follows: First, a constant reference aperture width Dk [μm] that serves as a reference for variation of the aperture width D, and a variation total width rate ΔD [%] are set.

[0086] Next, the aperture width D is set by randomly varying the reference aperture width Dk [μm] within a variation range defined by the overall variation rate δD [%]. For example, the aperture width D may be set by randomly varying Dk at a variation rate within ±(δD / 2)% (D[μm] = Dk[μm] × (100 ± (δD / 2)) [%]). In this case, the variation range of the aperture width D is equal to or greater than {Dk[μm] × (100 - (δD / 2)) [%]} and equal to or less than {Dk[μm] × (100 + (δD / 2)) [%]}. For example, if δD = 10% and Dk = 40 μm, D randomly varies within a variation range of ±5% (= ±(δD / 2)) with 40 μm (= Dk) as the center value of variation. That is, D randomly varies within a variation range of 38 μm to 42 μm.

[0087] The operation of varying and setting the aperture width D is repeated for each of the cylindrical lenses 21, and the aperture widths D1, D2, . . . , D n are set, respectively. Note that n is the number of cylindrical lenses 21 arranged in the X direction.

[0088] In this way, the aperture width D of each cylindrical lens 21 in the initial arrangement state is randomly varied to obtain a first varied arrangement state. As a result, as shown in Figures 2 to 5, the aperture widths D in the X direction of the multiple cylindrical lenses 21 arranged in the X direction have mutually different values.

[0089] As described above, in the first variable arrangement state, the aperture width D of the cylindrical lenses 21 varies randomly. In this first variable arrangement state, the multiple cylindrical lenses 21 can be arranged so that the surface shapes of the multiple cylindrical lenses 21 are different from each other compared to the initial arrangement state. However, in the first variable arrangement state, the radius of curvature R in the X direction of each cylindrical lens 21 matches the reference radius of curvature Rk (i.e., dR=0 μm). Furthermore, the position of the vertex 22 of each cylindrical lens 21 matches the center point 23 of each rectangular lattice and is not decentered (see the dashed dotted line in FIG. 6). That is, the amount of decentering Ec matches the reference amount of decentering Eck (e.g., Eck=0) (i.e., Ec=0).

[0090] (3) The second variable arrangement state with varying curvature radius R After setting the first variable arrangement state as described above, a second variable arrangement state is set in which the surface shape of the cylindrical lenses 21 is varied by randomly varying the curvature radius R of the cylindrical lenses 21. The curvature radius R is the curvature radius R (curvature radius in the X direction) of the cross-sectional shape of the cylindrical lenses 21 cut along a cross section in the XZ plane.

[0091] The method for randomly varying the radius of curvature R of the cylindrical lens 21 is, for example, as follows: First, a constant reference radius of curvature Rk [μm] that serves as a reference for variation of the radius of curvature R, and a full width ratio of variation ΔR [%] are set.

[0092] Next, the radius of curvature R is set by randomly varying the reference radius of curvature Rk within a variation range defined by the overall variation rate δR [%]. For example, the radius of curvature R may be set by randomly varying Rk at a variation rate within ±(δR / 2)% (R [μm] = Rk [μm] × (100 ± (δR / 2)) [%]). In this case, the variation range of the radius of curvature R is equal to or greater than {Rk [μm] × (100 - (δR / 2)) [%]} and equal to or less than {Rk [μm] × (100 + (δR / 2)) [%]}. For example, when δR = 20% and Rk = 25 μm, R randomly varies within a variation range of ±10% (= ±(δR / 2)) with 25 μm (= Rk) as the center value of variation. That is, R varies randomly within a range of 22.5 μm to 27.5 μm.

[0093] This operation of varying and setting the radius of curvature R is repeated for each of the cylindrical lenses 21, and the radii of curvature R1, R2, . . . , R n are set respectively.

[0094] In this way, the radius of curvature R of each cylindrical lens 21 in the first variable arrangement state is randomly varied to obtain a second variable arrangement state. As a result, as shown in FIGS. 2 to 5, the radii of curvature R in the X direction of the multiple cylindrical lenses 21 arranged in the X direction have mutually different values.

[0095] As described above, in the second variable arrangement state, the aperture width D and the radius of curvature R of the cylindrical lenses 21 are randomly varied. In this second variable arrangement state, the plurality of cylindrical lenses 21 can be arranged so that the surface shapes of the plurality of cylindrical lenses 21 are even more different from each other than in the first variable arrangement state. However, in the second variable arrangement state, the position of the vertex 22 of each cylindrical lens 21 coincides with the center point 23 of each rectangular lattice and is not decentered (see the dashed dotted line in FIG. 6 ). Note that, although the above describes an example in which the aperture width D is first varied and then the radius of curvature R is varied, this is not limiting. For example, the radius of curvature R may be varied first, and then the aperture width D may be varied.

[0096] (4) The third variation arrangement state in which the lens vertex position is varied After setting the second variable arrangement state as described above, a third variable arrangement state is set in which the X-direction position of the vertex 22 of each cylindrical lens 21 is randomly decentered from the center position of the reference shape, as shown in Fig. 6. Here, decentering means varying the planar position of the vertex 22 of the cylindrical lens 21 on the XY plane so that it is shifted in the X direction from the position (center position) of the center point 23 of the reference shape. Note that the center point 23 of the reference shape is the midpoint in the X direction of the cylindrical lens 21 having the reference aperture width Dk.

[0097] A method for randomly decentering the position of the vertex 22 of the cylindrical lens 21 in the X direction (lens vertex position 22) with respect to the center position is, for example, as follows.

[0098] First, the reference eccentricity Eck of the lens apex position 22 and the fluctuation full width rate ΔEc [%] of the eccentricity Ec [μm] are set. As described above, the eccentricity Ec is the deviation amount of the lens apex position 22 in the X direction from the center point 23 (the distance in the X direction between the lens apex position 22 and the center point 23). Eck is a reference value (fluctuation center value) when fluctuating the eccentricity Ec, and in this embodiment, Eck = 0 [μm]. The fluctuation full width rate ΔEc [%] is the ratio (percentage) of the fluctuation full width ΔEc [μm] to the reference aperture width Dk [μm]. Eck, ΔEc, and ΔEc are fixed values ​​set when the microlens array 20 is designed.

[0099] Next, the eccentricity Ec [μm] of each cylindrical lens 21 is set to a value obtained by randomly varying the eccentricity Ec within a variation range defined by the full width variation rate ΔEc [%], based on the reference eccentricity Eck. For example, the eccentricity Ec may be set by randomly varying Dk at a variation rate within ±(ΔEc / 2)% (Ec [μm] = Dk [μm] × (±(ΔEc / 2) [%])). In this case, the variation range of the eccentricity Ec is equal to or greater than {Dk [μm] × (-ΔEc / 2) [%]} and equal to or less than {Dk [μm] × (+ΔEc / 2) [%]}. For example, when ΔEc = 10% and Dk = 40 μm, Ec randomly varies within a variation range of ±5% (= ±(ΔEc / 2)) of 40 μm (= Dk), with Eck = 0 μm as the center value of variation. That is, Ec varies randomly within a range of −2 μm to +2 μm.

[0100] The operation of varying and setting the amount of eccentricity Ec is repeated for each of the cylindrical lenses 21, and the amounts of eccentricity Ec1, Ec2, . . . , Ec in the X direction are calculated for each of the cylindrical lenses 21. n are set, respectively. As a result, the lens vertex position 22 of each cylindrical lens 21 is randomly decentered in the positive or negative X direction with respect to the center position (center point 23) of the reference shape.

[0101] In this way, the lens vertex positions 22 in the second variable arrangement state are randomly varied from the center point 23 to obtain a third variable arrangement state. As a result, as shown in Fig. 6, the lens vertex positions 22 of the cylindrical lenses 21 are shifted from the center point 23 in the X direction by a random eccentricity amount Ec.

[0102] In this way, in the third variable arrangement state, the lens vertex positions 22 are randomly decentered. In the third variable arrangement state, the plurality of cylindrical lenses 21 can be arranged so that the surface shapes of the cylindrical lenses 21 are even more different from one another than in the second variable arrangement state.

[0103] Furthermore, in the third variable arrangement state, the height positions in the Z direction of the vertices 22 of the multiple cylindrical lenses 21 (positions in the thickness direction of the diffuser plate 1) vary from one another. More specifically, as shown in FIGS. 2 to 5, the height positions of the vertices 22 (the deepest points of concave lenses or the highest points of convex lenses) of the multiple cylindrical lenses 21 arranged in the X direction are different from one another. This further increases the randomness of the surface shapes of the multiple cylindrical lenses 21, making it possible to impart sufficient non-periodicity to the microlens array 20.

[0104] (5) Summary As described above, according to the method for arranging cylindrical lenses 21 according to this embodiment, first, a plurality of cylindrical lenses 21 are arranged regularly (initial arrangement state). Then, the aperture width D, curvature radius R, and eccentricity amount Ec of the lens vertex position 22 of the arranged plurality of cylindrical lenses 21 are randomly varied (first, second, and third varied arrangement states). This allows the surface shapes of the regularly arranged cylindrical lenses 21 to be randomly varied. Therefore, it is possible to realize a highly random three-dimensional surface structure of the microlens array 20 while realizing a quasi-regular arrangement of the cylindrical lenses 21.

[0105] Therefore, the microlens array 20 according to this embodiment can suitably control the overlapping state of the phases of the light diverging from each cylindrical lens 21. This can suitably suppress interference of the diffused light from each cylindrical lens 21 and diffraction due to the periodic structure of the microlens array 20. This can reduce unevenness in the intensity distribution of the linear diffused light in the X direction and improve the uniformity of the light distribution in the X direction. Furthermore, it is also possible to control the anisotropy of the light distribution in the X direction and the cutoff characteristic of the intensity distribution of the diffused light.

[0106] The cutoff characteristic means that the diffused light from the microlens array 20 has a so-called top-hat diffusion characteristic. The top-hat diffusion characteristic refers to an optical function in which, for collimated light in the visible light range or telecentric light with a collimated chief ray and a fixed aperture, the uniformity of the energy distribution within the angular components in a certain range is very high, and the energy can rapidly decrease beyond this certain range of the angular components. By realizing such a top-hat diffusion characteristic, the luminance distribution of the diffused light of the light incident on the microlens array 20 becomes substantially uniform within a predetermined diffusion angle range, and within the predetermined diffusion angle range, the luminance value of the diffused light falls within a range of, for example, ±20% of the average peak level (see FIG. 8, described later).

[0107] According to the microlens array 20 of this embodiment, a plurality of cylindrical lenses 21 are arranged on the XY plane using the above-described arrangement method, and the aperture width D, curvature radius R, and eccentricity Ec of the lens vertex position 22 of each cylindrical lens 21 are appropriately varied to vary the surface shape of the cylindrical lenses 21 and introduce a curved shape distorted from a semi-cylindrical shape. This allows the microlens array 20 to achieve the desired diffusion characteristics, making it possible to more reliably achieve top-hat diffusion characteristics.

[0108] Furthermore, according to this embodiment, a plurality of cylindrical lenses 21 having the same reference shape (e.g., a semi-cylindrical shape defined by a predetermined reference aperture width Dk and a predetermined reference curvature radius Rk) are regularly arranged on the XY plane (initial arrangement state), and then the aperture width D, the curvature radius R, and the eccentricity Ec of the lens vertex position 22 are varied (the first, second, and third varied arrangement states described above). This allows the plurality of cylindrical lenses 21 to be continuously arranged on the surface of the diffuser plate 1 without any gaps between them while ensuring the randomness of the surface shape of each cylindrical lens 21. Therefore, flat portions can be minimized at the boundaries between adjacent cylindrical lenses 21, thereby suppressing the component of incident light that is transmitted directly without being scattered by the surface of the diffuser plate 1 (zero-order transmitted light component). As a result, the uniformity of the linear light distribution in the X direction and the diffusion performance can be further improved.

[0109] <6. Variation requirements for each parameter> Next, the requirements for varying the parameters (aperture width D, radius of curvature R, and amount of eccentricity Ec) of the cylindrical lens 21 according to this embodiment will be described in detail.

[0110] As described above, in the microlens array 20 according to this embodiment, the aperture width D [μm] in the X direction of each cylindrical lens 21 varies randomly within a variation range defined by the full width variation ratio δD [%], with respect to the reference aperture width Dk. The radius of curvature R [μm] of each cylindrical lens 21 also varies randomly within a variation range defined by the full width variation ratio δR [%], with respect to the reference radius of curvature Rk. Furthermore, the lens vertex position 22 of each cylindrical lens 21 is decentered in the X direction from the center position (the position of the center point 23 in the X direction of the reference shape of each cylindrical lens). The amount of decentering Ec [μm] of each cylindrical lens 21 also varies randomly within a variation range defined by the full width variation ratio δEc [%].

[0111] Furthermore, the microlens array 20 according to this embodiment preferably satisfies the following variable requirements.

[0112] (1) δD≠0[%] and / or δR≠0[%] requirement First, the microlens array 20 according to this embodiment satisfies the requirement that at least one of the full width fluctuation ratio δD [%] and the full width fluctuation ratio δR [%] is not 0 [%] (δD ≠ 0 [%] and / or δR ≠ 0 [%]). This means that either the aperture width D or the radius of curvature R of each cylindrical lens 21, or both, fluctuates randomly within a predetermined fluctuation range defined by δD and δR.

[0113] That is, when δD is not 0% (i.e., when δD>0%]), it means that the aperture width D of each cylindrical lens 21 varies randomly within the variation range defined by δD. On the other hand, when δD is 0% it means that the aperture width D of each cylindrical lens 21 does not vary but is a constant value (for example, the same reference aperture width Dk). Similarly, when δR is not 0% (i.e., when δR>0%]), it means that the curvature radius R of each cylindrical lens 21 varies randomly within the variation range defined by δR. Conversely, when δR is 0% it means that the curvature radius R does not vary but is a constant value (for example, the same reference curvature radius Rk).

[0114] As described above, in this embodiment, at least one of δD and δR is not 0%. This causes random variation in either the aperture width D or the curvature radius R of each cylindrical lens 21. Here, as long as the condition that at least one of δD and δR is not 0% is satisfied, δEc may or may not be 0% (δEc > 0%). When δEc is not 0%, this means that the lens vertex position 22 of each cylindrical lens 21 is decentered by a random amount of decentering Ec within the variation range defined by δEc and is positioned at a position displaced from the central position. On the other hand, when δEc is 0%, this means that the lens vertex position 22 of each cylindrical lens 21 is not decentered and is positioned at the central position.

[0115] As described above, the microlens array 20 according to this embodiment satisfies the requirements of δD≠0[%] and / or δR≠0[%]. Therefore, if each cylindrical lens 21 is decentered by a random amount of decentering Ec (δEc≠0[%]), but neither the aperture width D nor the radius of curvature R varies (δD=0[%] and δR=0[%]), the variation requirements of the microlens array 20 according to this embodiment are not met. In other words, if δD=0[%] and δR=0[%] are satisfied, the microlens array 20 according to this embodiment does not correspond to the microlens array 20 according to this embodiment. In this embodiment, by varying at least one of the aperture width D and the radius of curvature R, preferably both, it is possible to obtain excellent light distribution and uniformity of the linear diffused light described above.

[0116] (2) Requirements for the square root K of δD, δR, and δEc Next, in the microlens array 20 according to this embodiment, the full width fluctuation ratio ΔD [%], the full width fluctuation ratio ΔR [%], and the full width fluctuation ratio ΔEc [%] satisfy the following formula (1).

[0117]

number

[0118] Here, the left side of equation (1) is the square root K of the full width fluctuation rates ΔD, ΔR, and ΔEc. The square root K [%] is expressed by the above-mentioned equation (10).

[0119] In the microlens array 20 according to this embodiment, as shown in the above formula (1), the square root K of the sum of the squares of ΔD, ΔR, and ΔEc is 9% or more (K≧9). In other words, the lower limit of K is 9%. Setting ΔD, ΔR, and ΔEc to satisfy formula (1) and setting K to 9 or more produces the following effects.

[0120] In a microlens array 20 that emits linear diffused light (uniaxial linear diffused light) extending in a specific direction (e.g., the X direction), as shown in FIG. 7, the diffraction (solid line in FIG. 7) due to one element of the microlens array 20 (i.e., an individual cylindrical lens 21) and the diffraction (dashed line in FIG. 7) due to the periodic structure of the microlens array 20 (i.e., the entire plurality of cylindrical lenses 21 arranged in the X direction) are superimposed, generating spectral diffracted light having the angle and intensity of the intersection.

[0121] 7, due to the refraction action of the lens surface of each cylindrical lens 21, the diffused light (solid line in FIG. 7) emitted from each cylindrical lens 21 is distributed uniformly in the X direction. At this time, each diffused light is distributed uniformly while including diffracted light in one direction, while the light distribution of its wide-angle component gradually decreases. On the other hand, in a microlens array 20 in which cylindrical lenses 21 having the same shape (i.e., the same aperture width D and the same lens phase surface) are periodically arranged, the uniform light distribution (solid line in FIG. 7) due to each cylindrical lens and the diffraction due to the periodic structure of the microlenses (dashed line in FIG. 7) are superimposed, generating spectral diffracted light (spectral noise: noise of peak-shaped diffracted light due to the periodic structure).

[0122] If K is less than 9, the variations in the aperture width D and curvature radius R of each cylindrical lens 21 and the eccentricity Ec of the lens vertex position 22 become inappropriate, making it impossible to appropriately randomize the phase state of the microlens structure surface. This causes the homogeneous light distribution by each cylindrical lens 21 (solid line in FIG. 7 ) to overlap with the diffraction due to the periodic structure of the microlens array 20 (dashed line in FIG. 7 ), generating spectral noise and reducing the homogeneity of the linear diffused light. Furthermore, the generation of noise in the zeroth-order diffracted light biases the light distribution of the linear diffused light, reducing the light distribution in the X direction.

[0123] In contrast, according to the microlens array 20 of this embodiment, the aperture width D, the radius of curvature R, and the amount of decentering Ec are randomly varied so as to satisfy the above formula (1) and make K equal to or greater than 9. This makes it possible to appropriately randomize the phase state of the microlens structure surface by varying the aperture width D and the radius of curvature R (both of which are phase) of each cylindrical lens 21 and decentering the lens vertex position 22 (change in phase distribution).

[0124] As a result, the different light distribution components from each cylindrical lens 21 are superimposed (mixed), widening the luminance distribution of the spectral diffracted light, thereby achieving a light distribution with a uniform and smooth spread in the X direction. In other words, the superimposition (mixing) of roughly uniform but different light distribution components from each cylindrical lens 21 is possible. Therefore, spectral diffracted light (spectral noise), which is a diffraction phenomenon of the periodic structure, can be eliminated, achieving a uniform light distribution. Therefore, in the microlens array 20 that emits line-shaped diffused light, the spectral noise generated by the diffraction phenomenon of the periodic structure of the microlens array 20 can be reduced, improving the uniformity of the intensity of the line-shaped diffused light. Furthermore, the noise of the zero-order diffracted light can be reduced, improving the light distribution of the line-shaped diffused light in a specific direction (X direction).

[0125] Furthermore, in the above formula (1), the square root K of the squares of the fluctuation full width ratios δD, δR, and δEc is used as a parameter to evaluate the fluctuation state of the microlens shape. This makes it possible to appropriately evaluate the fluctuation state of the microlens shape by comprehensively considering the fluctuations in the aperture width D, curvature radius R, and eccentricity amount Ec of the lens vertex position 22 of the cylindrical lens 21.

[0126] Furthermore, in the above formula (1), the fluctuation rate K D , K. R , K. EcInstead of the square root of the sum of squares of [±%], the square root of the sum of squares K of the fluctuation full width rates δD, δR, δEc [%] is used as a parameter. This allows the fluctuation state of the microlens shape to be appropriately evaluated, taking into account the fluctuation range in the real space of the microlens array 20 as much as possible. Random fluctuation rate K D , K. R , K. Ec The center of [±%] is not necessarily the reference zero in reality, and bias is likely to occur. However, it is estimated that the actual full width fluctuations of the fluctuation amounts dD, dR, and Ec follow the predetermined full width fluctuation rates δD, δR, and δEc [%]. Therefore, it is preferable to use the square root K of the sum of the squares of the full width fluctuation rates δD, δR, and δEc [%] as the parameter of equation (1) for evaluating the light distribution and uniformity of diffused light.

[0127] Here, the light distribution characteristics of the diffuser plate 1 according to this embodiment will be described with reference to Fig. 8. Fig. 8 is a graph showing an example of the light distribution characteristics of the diffuser plate 1 according to this embodiment. The vertical axis of the graph in Fig. 8 represents the luminance level of the diffused light diffused by the microlens array 20, and the horizontal axis of the graph in Fig. 8 represents the diffusion angle of the diffused light emitted from the diffuser plate 1. The solid line in the graph represents the luminance distribution of the linear diffused light in the X direction (the arrangement direction of the cylindrical lenses 21), and the dashed line represents the luminance distribution of the linear diffused light in the Y direction (the longitudinal direction of the cylindrical lenses 21).

[0128] 8, the fluctuation parameters of the lens shape of the cylindrical lens 21 are set as Dk=40 μm, Rk=25 μm, ΔD=20%, ΔR=20%, and ΔEc=0%. In this case, K=28.3, which satisfies the condition (K≧9) of equation (1).

[0129] As shown in FIG. 8, the diffusion angle (full width at half maximum: FWHM) of the diffused light in the X direction by the diffuser 1 according to this embodiment is approximately 30°, while the diffusion angle (full width at half maximum: FWHM) of the diffused light in the Y direction is approximately 2°. Therefore, the diffuser 1 according to this embodiment can effectively generate linear diffused light having directivity in a specific direction (X direction). Regarding the luminance distribution in the X direction (solid line in FIG. 8), when the diffusion angle is in the angular range of approximately -10° to 10°, the luminance level of the diffused light is generally uniform, falling within a range of ±15% of the central value of the luminance level (approximately 12.5). Therefore, spectral noise is sufficiently reduced, the luminance distribution in the X direction is smooth, and the uniformity of the light distribution in the X direction is high. Furthermore, no significant zero-order diffracted light (noise) is observed near 0°, and the diffused light is dispersed and distributed in the X direction, resulting in high light distribution.

[0130] As described above, with the diffuser 1 according to this embodiment, by randomly varying the lens shape of each cylindrical lens 21 under variation conditions that satisfy the above formula (1), it is possible to improve the uniformity and light distribution of the diffused light as shown in Fig. 8. Furthermore, by controlling the cutoff characteristics of the intensity distribution of the diffused light, it is also possible to achieve top-hat type diffusion characteristics as shown in Fig. 8.

[0131] (3) Preferable requirements for the square root K of δD, δR, and δEc Furthermore, it is preferable that ΔD, ΔR, and ΔEc satisfy the following formula (2): In other words, it is preferable that the square root K of the full width fluctuation rates ΔD, ΔR, and ΔEc is 14% or more.

[0132]

number

[0133] By setting K to 14 or more, at least one of the uniformity and light distribution of the diffused light can be significantly improved. Specifically, when K is 14 or more, the spectral noise generated by the diffraction phenomenon of the periodic structure of the microlens array 20 can be significantly reduced, thereby further improving the uniformity of the line-shaped diffused light. In addition, the zero-order diffracted light (noise) can be further reduced, thereby further improving the light distribution of the diffused light in the X direction.

[0134] Furthermore, it is preferable that δD, δR, and δEc satisfy the following formula (3). In other words, it is preferable that the square root K of the sum of the squares of δD, δR, and δEc is less than 46.9%. Formula (3) represents the physical configuration conditions of the microlens array 20 according to this embodiment.

[0135]

number

[0136] If K is 46.9 or more, the variation in the surface shape of each cylindrical lens 21 becomes excessively large, which causes problems such as the impracticality of the microlens structure being lost and the light distribution characteristics of the microlens being deteriorated.

[0137] This problem will be explained in more detail below. As shown in Fig. 1, the diffuser 1 according to this embodiment is configured by arranging, for example, a plurality of rectangular unit cells 3 (reference patterns) vertically and horizontally on the XY plane of the diffuser 1. When the plurality of unit cells 3 are laid out on the XY plane in this manner, it is preferable to maintain the continuity of the lens structure of the cylindrical lenses 21 at the boundaries between the unit cells 3. It is also preferable to accommodate the plurality of cylindrical lenses 21 continuously and without gaps within a predetermined region on the XY plane of the diffuser 1, even in areas other than the boundary portions.

[0138] In this regard, if the variation in the surface shape of each cylindrical lens 21 is excessively large, it becomes difficult to maintain the continuity of the lens structure between adjacent cylindrical lenses 21. As a result, it may not be possible to continuously accommodate multiple cylindrical lenses 21 without gaps within a predetermined area on the XY plane, which may result in defects in the microlens structure and other problems that prevent the physical configuration conditions of the microlens array 20 from being satisfied.

[0139] For example, when δD and δR are 30% or more and δEc is 20% or more, K is 46.9 or more. If the microlens array 20 is designed under such variable conditions that K is 46.9 or more, defects will occur in the microlens structure as described above, and the physical configuration conditions of the microlens structure will no longer be satisfied.

[0140] Therefore, it is preferable to set the variation conditions of the cylindrical lenses 21 (i.e., the aperture width D, the radius of curvature R, and the full width variation ratio δD, δR, and δEc of the eccentricity Ec) so that the above formula (3) is satisfied and K is less than 46.9. This allows the variations in the aperture width D, the radius of curvature R, and the eccentricity Ec of each cylindrical lens 21 to be within an appropriate variation range that allows the microlens structure to be realized. This makes it possible to maintain continuity of the lens structure between adjacent cylindrical lenses 21 on the XY plane, and to accommodate multiple cylindrical lenses 21 continuously and without gaps within a predetermined area on the XY plane. This prevents defects from occurring in the microlens structure and satisfies the physical configuration conditions of the microlens array 20. As a result, the microlens array 20 can be realized favorably and deterioration of the light distribution characteristics can be suppressed.

[0141] (4) Fluctuation rate of opening width D δD Here, the full width variation ratio ΔD is preferably 7% or more and less than 30%. If ΔD is 7% or more, the aperture width D can be varied sufficiently. This, combined with variations in other variables (such as the radius of curvature R and the amount of eccentricity Ec), can improve the light distribution and uniformity of the diffused light produced by the microlens array 20 and suppress the generation of zeroth-order diffracted light (noise). On the other hand, if ΔD is less than 7%, the aperture width D does not vary sufficiently, potentially reducing the light distribution and uniformity of the diffused light. On the other hand, if ΔD is 30% or more, the aperture width D varies excessively. Therefore, as described above, it may not be possible to continuously accommodate multiple cylindrical lenses 21 without gaps within a predetermined area on the XY plane, resulting in defects in the microlens structure and failing to satisfy the physical configuration requirements of the microlens array 20.

[0142] Therefore, ΔD is preferably 7% or more and less than 30%, and more preferably 25% or less, which satisfies the physical configuration conditions of the microlens array 20 while improving the light distribution and uniformity of the diffused light.

[0143] (5) Fluctuation ratio δR of radius of curvature R The full width variation ratio δR is preferably 7% or more and less than 30%. If δR is 7% or more, the radius of curvature R can be varied sufficiently. This, combined with variations in other variables (such as the aperture width D and the eccentricity Ec), can improve the light distribution and uniformity of the diffused light produced by the microlens array 20 and suppress the generation of zero-order diffracted light (noise). On the other hand, if δR is less than 7%, the variation in the radius of curvature R becomes insufficient, potentially degrading the light distribution and uniformity of the diffused light. On the other hand, if δR is 30% or more, the variation in the radius of curvature R becomes excessively large. Therefore, as described above, it becomes impossible to continuously accommodate multiple cylindrical lenses 21 without gaps within a predetermined area on the XY plane, resulting in defects in the microlens structure and failing to satisfy the physical configuration requirements of the microlens array 20.

[0144] Therefore, ΔR is preferably 7% or more and less than 30%, and more preferably 25% or less, which satisfies the physical configuration conditions of the microlens array 20 while improving the light distribution and uniformity of the diffused light.

[0145] (6) Fluctuation width ratio δEc of eccentricity Ec The full width variation ratio ΔEc is preferably 7% or more and 30% or less. If ΔEc is 7% or more, the eccentricity Ec can be varied sufficiently. This, combined with variations in other variables (such as the aperture width D and the radius of curvature R), can improve the light distribution and uniformity of the diffused light produced by the microlens array 20 and suppress the generation of zero-order diffracted light (noise). On the other hand, if ΔEc is less than 7%, the variation in the eccentricity Ec is insufficient, potentially reducing the light distribution and uniformity of the diffused light. On the other hand, if ΔEc is greater than 30%, the variation in the eccentricity Ec becomes excessively large. Therefore, as described above, it becomes impossible to continuously accommodate multiple cylindrical lenses 21 without gaps within a predetermined area on the XY plane, resulting in defects in the microlens structure and failing to satisfy the physical configuration requirements of the microlens array 20.

[0146] Therefore, ΔEc is preferably 7% or more and 30% or less, and more preferably 20% or less, which satisfies the physical configuration conditions of the microlens array 20 while improving the light distribution and uniformity of the diffused light.

[0147] 7. Microlens manufacturing method Next, a method for manufacturing the diffuser plate 1 according to this embodiment will be described with reference to Fig. 9. Fig. 9 is a flowchart showing the method for manufacturing the diffuser plate 1 according to this embodiment.

[0148] 9, in the manufacturing method of 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.

[0149] 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 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.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] 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).

[0154] 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 then, if necessary, a protective film, an anti-reflection film, etc. are formed (S117), thereby producing the diffuser plate 1 according to this embodiment.

[0155] 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.

[0156] 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.

[0157] 9 is merely an example, and the method for manufacturing a diffuser plate is not limited to the above example. For example, it is also possible to manufacture a diffuser plate using precision machining technology. In this case, a microlens structure having a surface shape in which a plurality of cylindrical lenses are arranged as described above may be formed by cutting the surface of the master disk or the substrate of the diffuser plate using cutting blades such as diamond bits having different shapes.

[0158] <8. Application example of Diffuser 1> Next, application examples of the diffuser plate 1 according to this embodiment will be described.

[0159] The above-described diffusion plate 1 can be appropriately mounted on devices that need to diffuse light to achieve 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.

[0160] 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.

[0161] The diffuser 1 can also be applied to a light source for remote sensing. For example, the diffuser 1 can be applied to remote sensing technologies that use light, such as LIDAR (Light Detection and Ranging), and to light distribution control of sensing light sources for various industrial or consumer robotic devices.

[0162] The device to which the diffusion plate 1 is applied is not limited to the above-mentioned application examples, and the diffusion plate 1 can be applied to any known device that utilizes the diffusion of light. [Example]

[0163] <9. Example> 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.

[0164] <9.1. Diffuser design conditions> Diffuser plates according to the examples of the present invention, comparative examples, and reference examples were manufactured by the manufacturing methods described below while changing the surface structure of the microlens array.

[0165] Specifically, after first cleaning the glass substrate, a photoreactive resist was applied to one surface (main surface) of the glass substrate with a resist thickness of 2 μm to 18 μm. As the photoreactive resist, for example, a positive photoreactive resist such as PMER-LA900 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) or AZ4620 (registered trademark) (manufactured by AZ Electronic Materials Co., Ltd.) was used.

[0166] Next, a pattern was written on the resist on the glass substrate using a laser writing device with a wavelength of 405 nm, and the resist layer was exposed. Note that the resist layer may also be exposed by performing mask exposure on the resist on the glass substrate using a stepper exposure device with g-line.

[0167] The resist layer was then developed to form a pattern in the resist. As a developer, a tetramethylammonium hydroxide (TMAH) solution such as NMD-W (manufactured by Tokyo Ohka Kogyo Co., Ltd.) or PMER P7G (manufactured by Tokyo Ohka Kogyo Co., Ltd.) was used.

[0168] Next, a glass substrate was etched using the patterned resist to produce a diffuser plate. Specifically, a resist pattern was formed on the glass substrate by glass etching using Ar gas or CF4 gas, to produce a diffuser plate.

[0169] Table 1 shows the design conditions for the surface structure of the microlens array for the diffusers of the Examples, Comparative Examples, and Reference Examples manufactured as described above, and the evaluation results of the light distribution and uniformity of the linear diffused light produced by the diffusers.

[0170] [Table 1]

[0171] In each of the examples, comparative examples, and reference examples shown in Table 1, microlens array 20 was designed using the microlens arrangement method according to the present embodiment described above. In this case, various parameters such as the lens parameters (Dk, Rk, δD, δR, δEc, Zmax) shown in Table 1 were appropriately changed to generate patterns of different microlens (cylindrical lens) surface shapes. Then, lens patterns representing the shapes and arrangements of the microlenses (cylindrical lenses) according to each of the examples, comparative examples, and reference examples were output. Using these lens patterns, diffusers according to each of the examples, comparative examples, and reference examples were manufactured by the above-described manufacturing method.

[0172] Specifically, the aperture width D of the cylindrical lenses (microlenses) in the X direction was set to a fixed value or a randomly varied value for each example, comparative example, and reference example, as shown in Table 1. When the full width variation rate δD=0%, this means that the aperture width D of each cylindrical lens was not varied, and the aperture width D of all cylindrical lenses was set to the reference aperture width Dk (fixed value). On the other hand, when the full width variation rate δD≠0%, this means that the aperture width D of each cylindrical lens was varied randomly within the variation range defined by δD, using the reference aperture width Dk as a reference, as in the following equation, for example: D[μm]=Dk[μm]+(Dk[μm]×±(δD / 2)[%])

[0173] Similarly, the radius of curvature R of the cylindrical lens 21 in the X direction was set to a fixed value or a randomly varied value for each example, comparative example, and reference example, as shown in Table 1. When the full width of variation δR=0%, this means that the radius of curvature R of each cylindrical lens was not varied, and the radius of curvature R of all cylindrical lenses was set to the reference radius of curvature Rk (a fixed value). On the other hand, when the full width of variation δR≠0%, this means that the radius of curvature R of each cylindrical lens was varied randomly within the variation range defined by δR, using the reference radius of curvature Rk as a reference, as shown in the following equation, for example: R[μm]=Rk[μm]+(Rk[μm]×±(δR / 2)[%])

[0174] Furthermore, with regard to the amount of decentering of the lens apex position 22, when the full width fluctuation rate ΔEc=0%, it means that the lens apex positions 22 of all cylindrical lenses are not decentered, and the amount of decentering Ec is set to 0 μm (reference amount of decentering Eck). On the other hand, when the full width fluctuation rate ΔEc≠0%, it means that the amount of decentering Ec of the lens apex position 22 of each cylindrical lens is decentered randomly in the positive and negative directions of the X direction within the fluctuation range defined by ΔEc, for example, as in the following equation: Ec[μm]=0[μm]+(Dk[μm]×±(δEc / 2)[%])

[0175] In Examples 1 to 13, the square root K of the sum of the squares of ΔD, ΔR, and ΔEc is 9 or more (specifically, K≧9.9), satisfying the condition of the above formula (1), and K is less than 46.9 (specifically, K≦46.4), satisfying the condition of the above formula (3), and also satisfying the condition of "ΔEc≦30%." Furthermore, in Examples 7 to 13, K is 14 or more (specifically, K≧14.1), satisfying the condition of the above formula (2).

[0176] In contrast, in Comparative Examples 1 to 7, K is less than 9, and the condition of formula (1) is not satisfied. In Comparative Example 8, K=10, and the condition of formula (1) is satisfied, but ΔD=0 and ΔR=0. Therefore, Comparative Example 8 does not satisfy the requirement of the microlens array 20 according to this embodiment (the requirement that at least one of ΔD and ΔR is not 0% (ΔD≠0 or ΔR≠0)). In Reference Examples 1 and 2, K is 46.9 or more, and the condition of formula (3) is not satisfied. In Reference Example 3, ΔEc is 35%, and the condition of "ΔEc≦30%" is not satisfied.

[0177] The surface shapes of the microlens arrays on the diffusers manufactured as described above according to Examples 1 to 13, Comparative Examples 1 to 8, and Reference Examples 1 to 3 were observed using a confocal laser microscope. Furthermore, the light distribution pattern of each diffuser was simulated using Virtual-Lab (manufactured by LightTrans), and the light distribution characteristics of each diffuser were measured using a light distribution characteristic measuring device Mini-Diff (manufactured by LightTec).

[0178] 10 to 33 show the surface shape patterns of the microlens arrays of the diffusers according to Examples 1 to 13, Comparative Examples 1 to 8, and Reference Examples 1 to 3, as well as simulation results of the light distribution characteristics and luminance distribution of diffused light, respectively.

[0179] 10 to 33 (Examples 1 to 13, Comparative Examples 1 to 8, and Reference Examples 1 to 3), (A) is a confocal laser microscope image (magnification: 50x) showing the surface shape pattern of the microlens array. (B) is an image showing the results of a simulation of light distribution by electromagnetic field analysis. (C) is a graph showing the results of a simulation of the luminance distribution of diffused light (horizontal axis: coordinate position [mm] in the X direction in the projected image 100 mm ahead (Z direction) from the diffuser plate. Vertical axis: amplitude of the electric field (electric field strength [V / m]) representing the luminance level of the diffused light). (D) shows the value of the square root K of the above ΔD, ΔR, and ΔEc.

[0180] <9.2. Evaluation criteria for diffuser panels> (1) Evaluation criteria for light distribution Regarding the light distribution of the linear diffused light by the diffusion plates of each Example and Comparative Example, the degree of reduction of zero-order diffracted light (noise) was evaluated on a three-level scale (evaluation: ◎, ○, ×) according to the following evaluation criteria. The evaluation results of such light distribution are shown in Table 1 above.

[0181] Evaluation: ⊚: The zero-order diffracted light was clearly reduced. Evaluation: ◯: Generation of zero-order diffracted light was not clear. Evaluation: ×: High intensity zero-order diffracted light or zero-order diffracted light having a cored luminance distribution was clearly generated.

[0182] Here, "high-intensity zeroth-order diffracted light" refers to zeroth-order diffracted light having a peak luminance level of 0.8 [V / m] or more or close to 0.8 [V / m], as shown in graphs (C) of Figures 10 to 13 and Figure 17 (Comparative Examples 1 to 4 and 8). Also, "zeroth-order diffracted light having a cored luminance distribution" refers to zeroth-order diffracted light having a peak luminance level of less than 0.8 [V / m] but a wide luminance distribution in the X direction, as shown in graphs (C) of Figures 14 to 16 (Comparative Examples 5 to 7).

[0183] The zeroth-order diffracted light (including the bright line spectrum) emitted from the diffuser plate is noise that inhibits dispersion of the light distribution in the X direction. For example, in the luminance distribution graphs shown in (C) of FIGS. 10 to 30, the zeroth-order diffracted light (noise) appears as a peak where the luminance level (electric field strength [V / m]) on the vertical axis reaches a high value (e.g., around 0.8) near the center of the X coordinate position on the horizontal axis (approximately around 90 to 120 mm). If the zeroth-order diffracted light can be reduced, the light distribution of the diffuser plate in the X direction can be improved. The light distribution of the diffuser plate according to each example and comparative example was evaluated based on the degree to which the zeroth-order diffracted light (noise) was reduced by variations in the surface shape of the microlenses.

[0184] (2) Evaluation criteria for homogeneity Regarding the uniformity of the linear diffused light produced by the diffusers of each Example and Comparative Example, the degree of reduction in spectral noise contained in the diffused light was evaluated using three levels (evaluation: ◎, ○, ×) according to the following evaluation criteria. The evaluation results of the uniformity are shown in Table 1 above.

[0185] Evaluation ⊚: Spectral noise was uniformly reduced to a low luminance level of approximately 0.5 [V / m] or less. Evaluation: ○: High intensity spectrum noise at a luminance level of approximately 0.5 [V / m] was reduced. Evaluation: ×: Spectral noise with a high intensity, the luminance level of which was well above about 0.5 [V / m], occurred.

[0186] (3) Overall evaluation criteria The light distribution (reduction degree of zero-order diffracted light) and uniformity (reduction degree of spectral noise) of the diffusers according to each of the examples and comparative examples were evaluated comprehensively on a five-point scale (ratings A to E) according to the following evaluation criteria. The comprehensive evaluation results are shown in Table 1.

[0187] Evaluation A: Both the light distribution and uniformity of the diffused light were very good. In other words, there was no generation of zero-order diffracted light or other diffracted light, and the spectral noise was uniformly reduced to a low luminance level of approximately 0.5 [V / m] or less. Rating B: Both the light distribution and uniformity of the diffused light were good, and either the light distribution or the uniformity was very good. That is, either no zero-order diffracted light was generated (very good light distribution), or the zero-order diffracted light was largely suppressed (good light distribution). Furthermore, either the spectral noise was uniformly reduced to a low luminance level of approximately 0.5 V / m or less (very good uniformity), or high-intensity spectral noise at a luminance level of approximately 0.5 V / m was reduced (good uniformity). Evaluation C: Both the light distribution and uniformity of the diffused light were good. In other words, the zeroth-order diffracted light was largely suppressed, and high-intensity spectral noise at a luminance level of approximately 0.5 [V / m] was reduced. Rating D: The light distribution of the diffused light was insufficient. That is, zero-order diffracted light with a luminance level equivalent to or higher than 0.8 [V / m] or zero-order diffracted light with a cored luminance distribution was generated. The evaluation E:K or ΔEc setting was too large, causing excessive fluctuations in the lens surface shape, which resulted in multiple cylindrical lenses not fitting within the lens generation area and resulting in missing microlens structures. As a result, the physical configuration conditions for the microlens array were not met.

[0188] <9.3. Comparison of evaluation results of Examples, Comparative Examples, and Reference Examples> The evaluation results of Examples 1 to 13, Comparative Examples 1 to 8, and Reference Examples 1 to 3 will be compared and explained below.

[0189] (A) Regarding the condition (K≧9) and requirement (δD≠0 and / or R≠0) of Equation (1), As shown in Table 1, Comparative Examples 1 to 7 do not satisfy the condition (K≧9) of formula (1). As a result, Comparative Examples 1 to 7 were all rated "X" for light distribution and uniformity, and the overall rating was "D".

[0190] Furthermore, Comparative Example 8 does not satisfy the requirements of the microlens array according to this embodiment (i.e., the requirement that at least one of δD and δR is not 0% (δD≠0 and / or δR≠0)), and only the eccentricity Ec is varied without varying the aperture width D and the radius of curvature R. As a result, the light distribution of Comparative Example 8 is rated "X", and the overall rating is "D".

[0191] In contrast, Examples 1 to 13 satisfy the condition (K≧9) of formula (1). Furthermore, Examples 1 to 13 also satisfy the requirements of the microlens array according to this embodiment (δD≠0 and / or δR≠0), and at least one of the aperture width D and the radius of curvature R is varied. As a result, in Examples 1 to 13, the light distribution and uniformity were all evaluated as "○" or "◎", and the overall evaluation was evaluated as "A", "B", or "C".

[0192] From the above results, it can be seen that by satisfying the condition (K≧9) of formula (1) and the requirements (δD≠0 and / or δR≠0) as in Examples 1 to 13 of the present invention, it is possible to suppress the generation of zero-order diffracted light (noise) in uniaxial linear diffused light, improve the light distribution of the diffused light, reduce spectral noise, and improve the uniformity of the diffused light in the X direction.

[0193] (B) Regarding the condition of equation (2) (K≧14) As shown in Table 1, Examples 1 to 6 satisfy the condition (K≧9) of formula (1), but do not satisfy the condition (K≧14) of formula (2). As a result, Examples 1 to 6 were all rated "○" for light distribution and uniformity, and the overall rating was rated "C."

[0194] In contrast, Examples 7 to 13 satisfy the condition (K≧14) of formula (2). As a result, in Examples 7 to 13, one or both of the evaluations of light distribution and uniformity are rated as "◎", and the overall evaluation is rated as "A" or "B".

[0195] From the above results, it can be seen that by satisfying the condition (K≧14) of formula (2) as in Examples 7 to 13 of the present invention, the generation of zero-order diffracted light (noise) can be more reliably suppressed, the light distribution of the diffused light can be further improved, and the spectral noise can be significantly reduced, thereby further improving the uniformity of the diffused light in the X direction.

[0196] (C) Regarding the condition of formula (3) (K<46.9) and the condition of "δEc≦30%" As shown in Table 1, Reference Examples 1 and 2 do not satisfy the condition (K<46.9) of Expression (3). Expression (3) is an expression representing the physical configuration condition of the microlens array according to this embodiment. Furthermore, Reference Example 3 does not satisfy the condition "ΔEc≦30%". This condition "ΔEc≦30%" is also an expression representing the physical configuration condition of the microlens array according to this embodiment. Furthermore, Reference Examples 1 and 2 do not satisfy the conditions "ΔD<30%" and "ΔR<30%" (preferable physical configuration conditions of the microlens array). As a result, in Reference Examples 1 to 3, the lens surface shape was excessively varied, so that multiple cylindrical lenses did not fit within the lens generation area, resulting in missing microlens structures. Therefore, the physical configuration condition of the microlens array was not satisfied. As a result, the overall evaluation of Reference Examples 1 to 3 was an "E" rating.

[0197] In contrast, Examples 1 to 13 satisfy the condition of formula (3) (K<46.9) and also satisfy the condition "ΔEc≦30%". Furthermore, Examples 1 to 13 also satisfy the preferable conditions of "ΔD<30%" and "ΔR<30%". As a result, in Examples 1 to 13, multiple cylindrical lenses are contained within the lens formation region, no missing microlens structures occur, and the physical configuration conditions of the microlens array are satisfied. As a result, the overall evaluation of Examples 1 to 13 was not an "E" evaluation, but rather an "A" to "C" evaluation.

[0198] From the above results, it can be seen that by satisfying the condition of formula (3) (K<46.9) and the condition "ΔEc≦30%" as in Examples 1 to 13 of the present invention, the surface shape of each cylindrical lens can be varied within an appropriate variation range, thereby satisfying the physical configuration conditions of the microlens array. Furthermore, it can be seen that by satisfying the preferable conditions of "ΔD<30%" and "ΔR<30%", the physical configuration conditions of the microlens array can be more reliably satisfied, further improving the feasibility of the microlens array structure.

[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 3. Unit Cell 10 Base material 20 Microlens Array 21 Cylindrical lens (micro lens) 22 Cylindrical lens apex (lens apex position) 23 Center point (center position) of cylindrical lens D Opening width R (radius of curvature) Ec Eccentricity

Claims

1. A microlens array type diffuser that emits linearly diffused light, A substrate; a plurality of cylindrical lenses arranged in the X direction on an XY plane on at least one surface of the substrate, the lenses comprising convex or concave ridge portions extending in a Y direction perpendicular to the X direction; Equipped with an opening width D [μm] in the X direction of each of the cylindrical lenses randomly fluctuates within a fluctuation range defined by a fluctuation total width rate δD [%] with respect to a reference opening width Dk [μm]; The radius of curvature R [μm] of each cylindrical lens varies randomly within a variation range defined by a full width variation rate δR [%] based on a reference radius of curvature Rk [μm], The eccentricity Ec [μm] of each cylindrical lens varies randomly within a variation range defined by a full width variation rate δEc [%], The δD [%], the δR [%], and the δEc [%] satisfy the following formula (2), and both the δD [%] and the δR [%] are not 0 [%], The δD [%] is 7% or more and less than 30%, The δR [%] is 7% or more and less than 30%, The diffusion plate, wherein the δEc [%] is 7% or more and 30% or less. [Equation 1] however, The total fluctuation width rate δD [%] is the ratio of the total fluctuation width ΔD [μm] to the reference opening width Dk [μm] (δD = ΔD / Dk × 100), The total fluctuation width ΔD [μm] is the upper limit dD of the fluctuation amount dD of the opening width D. ＭＡＸ and the lower limit dD ＭＩＮ and the difference (ΔD = dD ＭＡＸ -dd ＭＩＮ ), The total fluctuation width ratio δR [%] is the ratio of the total fluctuation width ΔR to the reference curvature radius Rk (δR = ΔR / Rk × 100), The total fluctuation width ΔR [μm] is the upper limit dR of the fluctuation amount dR of the radius of curvature R. ＭＡＸ and the lower limit dR ＭＩＮ and the difference (ΔR = dR ＭＡＸ -dR ＭＩＮ ), the eccentricity amount Ec is a deviation amount in the X direction of the vertex position of each of the cylindrical lenses with respect to the center position of each of the cylindrical lenses in the X direction, The total fluctuation width rate δEc [%] is the ratio of the total fluctuation width ΔEc to the reference opening width Dk (δEc=ΔEc / Dk×100), The total fluctuation width ΔEc [μm] is the upper limit Ec of the eccentricity amount Ec ＭＡＸ and the lower limit Ec ＭＩＮ and the difference (ΔEc = Ec ＭＡＸ -Ec ＭＩＮ ).

2. The δD [%], the δR [%], and the δEc [%] satisfy the following formula (3): The diffusion plate according to claim 1 , wherein the δEc [%] is 30% or less. [Equation 2]

3. A display device comprising the diffusion plate according to claim 1 or 2.

4. A projection device comprising the diffuser plate according to claim 1 or 2.

5. A lighting device comprising the diffusion plate according to claim 1 or 2.

6. A light source for remote sensing, comprising the diffuser plate according to claim 1 or 2.

Images