Optical pickup device and optical disk device having a diffraction grating

摘要

An optical pickup device is adapted to read information signals from optical recording media of two different types such as a "DVD" and a "CD" for which two light beams with different wavelengths are used and comprises a photodetector having a single light receiving section that can be shared by optical recording media of two different types. Both the light beam reflected from the signal recording surface of the "DVD" 106 a and the light beam reflected from the signal recording surface of the "CD" 106 b are diffracted by the diffraction element 6 and focussed to a same spot on the light receiving surface of the photodiode of a photodetector 7.