Patent ID: 7940309
Filing Date: 2011-05-10
Classification: G02B,G03B

Abstract:
1. An optical low pass filter, comprising: a light transmitting member; a refractive index distribution generation unit that generates a refractive index distribution cyclically changing within a plane of the light transmitting member, the plane being perpendicular to an optical axis of a light beam incident to the light transmitting member, the refractive index distribution generation unit generating the refractive index distribution within the plane by generating a compressional wave progressing in the light transmitting member and comprising a piezoelectric element that generates the compressional wave in the light transmitting member by applying a high frequency voltage; a controller that controls the refractive index distribution generation unit so as to partially change a low pass filtering function according to the refractive index distribution within the plane of the light transmitting member; and an electrical power control circuit that controls a level of an electrical power applied to the piezoelectric element, wherein: