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DE-112015001703-B4 - Optical element

DE112015001703B4DE 112015001703 B4DE112015001703 B4DE 112015001703B4DE-112015001703-B4

Abstract

A microlens array (1100) equipped with a plurality of microlenses and formed as the only component comprising a collimator lens (1200), wherein each microlens has: N sides (S) of a convex polygon, a microlens vertex (T) located from a face of the convex polygon, and N curved surfaces (CS) separated by lines connecting the microlens vertex (T) and the N vertices of the convex polygon, and where the straight line passing through the microlens vertex (T) and perpendicular to the face of the convex polygon is defined as the z-axis, the intersection point between the z-axis and the face of the convex polygon is defined as the origin (O), and the straight line in the face of the convex polygon passing through the origin (O) and perpendicular to a side (S) of the convex polygon is defined as the x-axis, the z-coordinate of the curved surface corresponding to the side (S) is represented by z = f ( x ) , where t is a distance from the origin (O) to the side (S), n is a refractive index of a microlens material, A is a non-negative constant, C is a positive constant, and g(x) is defined by g ( x ) = − x | x | ⋅ C x 2 + A n 1 + ( C x 2 + A ) 2 − 1 where each microlens is designed in such a way that g ( x ) − 0,035 ≤ d f ( x ) d x ≤ g ( x ) + 0,035 for 0.25·t < |x| ≤ t.

Inventors

  • Daisuke Seki
  • Norihisa Sakagami

Assignees

  • NALUX CO., LTD.

Dates

Publication Date
20260513
Application Date
20150324
Priority Date
20140407

Claims (6)

  1. A microlens array (1100) comprising a plurality of microlenses and consisting of a single component comprising a collimator lens (1200), each microlens comprising: N sides (S) of a convex polygon, a microlens vertex (T) located from a face of the convex polygon, and N curved surfaces (CS) separated by lines connecting the microlens vertex (T) and the N vertices of the convex polygon, where the straight line passing through the microlens vertex (T) and perpendicular to the face of the convex polygon is defined as the z-axis, the intersection point between the z-axis and the face of the convex polygon is defined as the origin (O), and the straight line in the face of the convex polygon passing through the origin (O) and perpendicular to a side (S) of the convex polygon is defined as the x-axis, which The z-coordinate of the curved surface corresponding to side (S) is represented by z = f ( x ) , where t is a distance from the origin (O) to the side (S), n is a refractive index of a microlens material, A is a non-negative constant, C is a positive constant, and g(x) is defined by g ( x ) = − x | x | ⋅ C x 2 + A n 1 + ( C x 2 + A ) 2 − 1 where each microlens is designed in such a way that g ( x ) − 0,035 ≤ d f ( x ) d x ≤ g ( x ) + 0,035 for 0.25·t < |x| ≤ t.
  2. A microlens array (1100) according to Claim 1 , where the convex polygon is a regular polygon.
  3. A microlens array (1100) according to Claim 2 , where the z-axis is defined such that it passes through the center of the regular polygon.
  4. A microlens array (1100) according to one of the Claims 1 until 3 , where N is 3, 4 or 6.
  5. A microlens array (1100) according to one of the Claims 1 until 4 , wherein each microlens is formed such that adjacent curved surfaces (CS) have a different shape.
  6. A microlens array (1100) according to Claim 1 , where the curved surface (CS) of the microlens is represented by z = f ( x ) = ∑ n = 1 10 ( x | x | ) n a n x n where n is a positive integer and a n is a constant.

Description

Technical field The present invention relates to a microlens array for forming an illuminated area with a uniform illuminance distribution. background Optical elements for modifying the light distribution from a light source, creating an illuminated area used as alignment marks or indicators for visual recognition in measuring devices, medical instruments, industrial robots, or similar applications, have been developed. Among these optical elements are those in which subdivided parts of a cylindrical lens are combined (Patent Document 1), and those shaped as a pyramid with lateral faces that have a cylindrical envelope (Patent Document 2). However, an optical element designed in such a way that the distribution of light in an illuminated area formed on a surface becomes uniform to a satisfactory degree has not been conventionally developed. State of the art documents Patent documents Patent document 1: JP 11 - 133 209 APatent document 2: JP 2003 - 504 217 A ( WO 01 / 03 892 A1 ) Further exemplary microlens arrays can be found in the printed materials. US 6 816 311 B1 , US 2006 / 0 250 707 A1 and JP 2000 - 56 101 A known. Brief description of the invention Problem to be solved by the invention Accordingly, there is a need for an optical element designed in such a way that the distribution of light in an illuminated area formed on a surface becomes sufficiently uniform. Measures to solve the problem According to the present invention, a microlens array as defined in claim 1 is provided. Exemplary embodiments of the present invention are defined in the dependent claims. An optical element according to one aspect of the present disclosure is equipped with a plurality of microlenses. Each microlens has N sides of a convex polygon, a microlens vertex located a distance from a plane of the convex polygon, and N curved surfaces subdivided by lines connecting the microlens vertex and the N vertices of the convex polygon. If the straight line passing through the microlens vertex and perpendicular to the plane is defined as the z-axis, the intersection point between the z-axis and the plane is defined as the origin, and the straight line in the plane passing through the origin and perpendicular to a side is defined as the x-axis, then a z-coordinate of the curved surface corresponding to the side is represented by z=f(x), where a distance from the origin to the side is represented as t, and a virtual curved surface at 0 ≤ |x| ≤ t is represented by z=F(x), where n is a refractive index of a microlens material, A represents a non-negative constant, C represents a positive constant, and g(x) is defined by g(x)=dF(x)dx=−x|x|⋅Cx2+An1+(Cx2+A)2−1, where each microlens is designed in such a way that g(x)−0,035≤df(x)dx≤g(x)+0,035 This condition is met for 0.25·t < |x| ≤ t. Each curved surface of each microlens of the optical element according to the present aspect is formed such that the difference between a gradient of the curved surface of each microlens and a virtual curved surface that uniformly renders an illuminance distribution in an illuminated area formed by a uniform beam of parallel rays incident at a right angle to the plane of the polygon of each microlens on a plane perpendicular to the parallel beam is 0.035 or less than 0.25·t < |x| ≤ t. Accordingly, an illuminance distribution in an illuminated area formed by a uniform A bundle of parallel rays, incident at a right angle onto the plane of the polygon of each microlens of the optical element according to the present aspect, is essentially uniform on a plane perpendicular to the bundle of parallel rays. Even if variations in the intensity of a bundle of parallel rays exist, the illuminance distribution in an illuminated area formed by the entire microlens array will be essentially uniform because the microlens array comprises a plurality of microlenses. Furthermore, because the area of each curved surface where 0.25·t < |x| ≤ t is satisfied is small, the gradient there is not significant. In the optical element according to the first embodiment of the present disclosure, where an acute angle of the direction in which a ray, which strikes the plane perpendicularly and moves in the z-axis direction, moves after exiting the virtual curved surface is represented with the z-axis by θ, θ at x=0 is represented by θc, and θ at |x|=t is represented by θe, the following relationships apply. A=tan θcC=tan θe−tan θct2 In the optical element according to the second embodiment of the present disclosure, z=F(x) monotonically decreases for |x| within 0 ≤ |x| ≤ t. In the optical element according to the third embodiment of the present disclosure, the convex polygon is a regular polygon. In the optical element according to the fourth embodiment of the present disclosure, the z-axis is defined such that it passes through the center of the regular polygon. In the optical element according to the fifth embodiment of the present disclosure, N is 3, 4 or 6. In the optical element acco