Optical head for a plurality of types of information recording media

摘要

An optical head with high light utilization efficiency that includes a diffractive optical element and a light source emitting beams with a plurality of wavelengths that can read plural types of information recording media. A beam emitted from a light source selectively emitting a beam with a first wavelength and a beam with a second wavelength that is approximately twice as long as the first wavelength is collimated into a parallel beam by a diffraction collimator lens, is bent by a mirror for bending an optical path, and then is focused by a diffraction objective lens on an information recording medium. Outgoing light from these diffractive lenses is substantially a second-order diffraction light with respect to the beam with the first wavelength and is substantially a first-order diffraction light with respect to the beam with the second wavelength.