Diffraction element and optical pickup head device

摘要

It is an object of the invention to provide a diffraction element having a simple configuration for detecting light beams of different wavelengths that are irradiated in order to store or reproduce information with respect to different types of optical disks, and an optical pickup head device. The diffraction element includes a first diffraction grating for diffracting a first light beam having a first wavelength lambda1 so as to emit a first first-order diffracted light beam, and a second diffraction grating for diffracting a second light beam having a second wavelength lambda2, which is different from the first wavelength lambda1, so as to emit a second first-order diffracted light beam. The first diffraction grating and the second diffraction grating are arranged so that the first first-order diffracted light beam diffracted by the first diffraction grating and the second first-order diffracted light beam diffracted by the second diffraction grating are focused onto a same photodetector.