Patent ID: 9341754
Filing Date: 2016-05-17
CPC Classification: G02B

Claim Text:
1. A light diffuser for point light sources comprising: a plurality of convex portions formed on a surface thereof, the convex portions being convex with respect to the surface, wherein each of the convex portions has a substantially triangular pyramid shape whose bottom surface is a triangle, and an inclined angle θ with respect to a bottom surface of a side surface of the substantially triangular pyramid shape and a refractive index A of a material forming the convex portion satisfy the following equations (1) and (2): wherein the light diffuser further satisfies the following conditions: wherein g indicates a length of a projected line segment formed when a portion which is located closer to a top side than a portion in which the angle θ′ between a tangent among tangents of the one side surface of the convex portion and the bottom surface satisfies (1′) and (2′) is projected to the horizontal surface; b indicates a length of a projected line segment obtained when a portion B in which an angle θ′ between a tangent plane of one side surface and a bottom surface of the convex portion satisfies (1′) and (2′) is projected to a horizontal surface; c indicates a length of a projected line segment obtained when a portion C which is closer to a skirt side of the convex portion than the portion B is projected to the horizontal surface; d indicates a length of a projected line segment obtained when a portion D which is closer to a top side than the portion B is projected to the horizontal surface; and in a cutting surface appearing, the convex portion is cut at a flat surface passing through an I point, a J point, and a top of the convex portion (a center of gravity of a top triangle when the convex portion is a triangular pyramid frustum shape), wherein the I point is a projected point obtained when the top of the convex portion (the center of gravity of the triangle top when the convex portion is the triangular pyramid frustum shape) is vertically projected to the triangular bottom surface; the J point is an intersection of a perpendicular with a side that is obtained when the perpendicular is drawn from the I point to the side closest to the I point among the sides comprised in the triangular bottom surface, wherein a single-sided portion further passes through an I′ point and a J′ point from a center of a cutting surface appearing when the convex portion is cut at a flat surface perpendicular to the triangle bottom surface, wherein the I′ point is a midpoint of a line segment obtained by connecting a point obtained when the top of the convex portion (the center of gravity of the triangle top when the convex portion is the triangular pyramid frustum shape) is vertically projected to the triangle bottom surface with a top of the triangular bottom surface closest to the projected point among the tops of the triangular bottom surface; the J′ point is an intersection of a perpendicular with a side that is obtained when the perpendicular is drawn from the I′ point to the side closest to the I′ point among the sides comprised in the triangular bottom surface; and when there exist a plurality of cutting surfaces that satisfy the conditions, the cutting surface where g has a maximum value is adopted.