Patent ID: 10393927

Abstract:
A diffuser is provided with a recess-protrusion structure formed on a plane. When a z-axis is defined as a normal to the plane, an x-axis is defined on the plane, the x-axis is divided into plural intervals, Snx represents length of an interval nx, Sx-max and Sx-min represent the maximum and the minimum of Snx, respectively, the relationship 2<Sx-max/Sx-min holds, Snx varies on a random basis between Sx-min and Sx-max, in an xz cross section, a recess portion and a protrusion portion are formed on each of adjacent intervals along the x-axis, respectively, and when dznx represents a difference between the maximum and the minimum of z coordinate of the recess-protrusion structure in the interval nx in the xz cross section, Anx represents a ratio between dznx and Snx, Anx-max and Anx-min represent the maximum and the minimum of Anx, the relationship Ax-max/Ax-min<1.3 holds.