To solve the problem that a conventional lens generates a difference between light intensity nearby a light source and light intensity distant from the light source and also to solve the problem that a light source using the primary colors (red R, blue B, and green G) of light (hereinafter an RGB light source) may fails in light mixing nearer the light source.

A lens is arranged at a bottom of a cylinder equal to a circumference of one lens or two or more stacked lenses so as to obtain effects of critical reflection in the cylinder. Further, a translucent diffusion plate is provided at the cylinder bottom where the lens is arranged or on the opposite upper side so as to accelerate diffusion in multiple directions.