Patent ID: 9329374
Filing Date: 2016-05-03
CPC Classification: F21S,G02B

Claim Text:
1. An optical surface determination method for a projection lens that receives light entering through a rear face of the projection lens, internally reflects the light twice, and then emits the light from a front face of the projection lens, the optical surface determination method comprising: setting an incoming wavefront of light that is emitted from a light source and enters the projection lens; setting an outgoing wavefront of light that is emitted from the projection lens and forms a predetermined light distribution pattern; setting a shape of the front face of the projection lens; setting a shape of an incidence region in the rear face of the projection lens, through which the incoming wavefront emitted from the light source enters the projection lens; calculating a first intermediate wavefront generated by an internal reflection by a first reflection region of the front face of the projection lens, based on a shape of the first reflection region; calculating a second intermediate wavefront before refracted by a refraction region of the front face of the projection lens, based on a shape of the refraction region; and determining, as an optical surface, a shape of a second reflection region in the rear face of the projection lens, which reflects the first intermediate wavefront and outputs the second intermediate wavefront, based on the calculated first intermediate wavefront and the calculated second intermediate wavefront.