DIFFRACTIVE OPTICAL ELEMENT AND OPTICAL HEAD APPARATUS

摘要

[PROBLEMS] To provide a diffractive optical element diffracting light of three wavelengths at two diffraction grating surfaces. [MEANS FOR SOLVING PROBLEMS] A diffractive optical element is provided with a first diffraction grating surface and a second diffraction grating surface facing the first diffraction grating surface. With respect to incoming lights of three wavelengths, the diffraction efficiency of the diffracted light of one wavelength is equal to or below a prescribed value at the first diffraction grating surface, and the diffraction efficiency of the diffracted light of the other wavelengths is equal to or below the prescribed value at the second diffraction grating surface. This allows obtaining a diffractive optical element capable of diffracting lights of three wavelengths with a simple configuration.