Patent ID: 8320226

Claim:
An optical element comprising: three or more sub-wavelength convexo-concave structures having pitches less than a wavelength of an incident light incident to the optical element and having groove depths equal to each other; and a periodic structure having the three or more sub-wavelength convexo-concave structures, the pitch of the periodic structure greater than the wavelength of the incident light, wherein a predetermined polarization direction of the incident light is diffracted mainly into a specific order, and wherein groove extending directions of the three or more sub-wavelength convexo-concave structures are formed so as to be different from each other and filling factors of the three or more sub-wavelength convexo-concave structures are set so that refractive indexes of the three or more sub-wavelength convexo-concave structures with respect to a polarization direction different from the predetermined polarization direction are the same as each other.