Patent ID: 8451539

Claim:
An optical element comprising: a first light transmitting layer placed at a light incident side of the optical element and having a first sawtooth blazed surface, the first sawtooth blazed surface including a plurality of first light-transmitting slopes defining a first blaze angle; and a second light transmitting layer having a second sawtooth blazed surface including a plurality of second light-transmitting slopes defining a second blaze angle, the second light transmitting layer having a bottom surface, the bottom surface of the second light transmitting layer being in contact with all of the first sawtooth blazed surface of the first light transmitting layer, wherein, a tilting direction of the first light-transmitting slopes and a tilting direction of the second light-transmitting slopes are opposite, when the first light transmitting layer has an Abbe number ν; the second light transmitting layer has an Abbe number ν′; the first sawtooth blazed surface has a step height d; and the second sawtooth blazed surface has a step height d′, the relationship d′/d<ν′/ν−1 is satisfied; light which passes the first and second light transmitting layer is immediately output to an outside of the optical element directly from the second light transmitting layer, when the first light transmitting layer has a refractive index n; the second light transmitting layer has a refractive index n′; the first sawtooth blazed surface has a step height d; the second sawtooth blazed surface has a step height d′; and light being used has an average wavelength λ, {d(n′−1)−d(n−n′)}/λ is within a range of ±0.2 around an integer value.