US Patent 7839754 Optical head and optical disk device

An optical head includes a first laser diode configured to generate a laser beam with a wave length of λ1, a second laser diode configured to generate a laser beam with a shorter wave length of λ2 than the wave length λ1, a collimator lens arranged so that the laser beams are incident on it, an aperture filter arranged on an optical axis of the collimator lens, and an object lens 0 arranged on the optical axis so that the laser beams passing through the aperture filter are incident on it, wherein the second laser diode is arranged at a position on the optical axis further away from collimator lens than the first laser diode is away from the collimator lens.