A light incident angle detectiing device with semi-transparent and radially gradient film

PURPOSE: A light source direction tracking apparatus in which a translucency radial shape gradation film is adhered is provided to reduce the operation quantity which a computer processes in an active type light retro-reflector using a pin hole and image sensor, thereby improving the whole performance. CONSTITUTION: A light source direction tracking apparatus in which a translucency radial shape gradation film is adhered comprises the followings: a flat board(20) which forms a pin hole in which the light is transmitted; a radial shape gradation film(30) which is integrally formed in the flat board; an image sensor(10) which is separately installed with the flat board and forms a phase of the light which penetrated and transmitted the pin hole; and a lower plate(50) which measures a phase central part of the transmission light which is measured in the image sensor and measures the direction of the light source.