Patent ID: 7688511
Filing Date: 2010-03-30
Classification: G02B,G02F

Abstract:
1. A transmission diffraction grating having a film or plate shape, the diffraction grating having an incidence surface to receive incident light and an output surface to transmit and output the incident light, the incidence surface having fine grating grooves that are parallel to one another and form a sawteeth sectional shape, when receiving white light having ClE color coordinates of x=0.310 and y=0.316, the diffraction grating providing output light having a ClE color coordinate x of 0.31≦x≦0.37 and a color coordinate y of 0.3≦y 0.42, bending white light obliquely made incident to the diffraction grating to a vertical direction with suppressed dispersion and outputting the bent light, thereby realizing a light-condensing ability that a change in an output light angle is smaller than a change in an incident light angle, a normal of one of the slopes of a sawtooth forming an angle α