| 摘要 |
An optical pickup which includes first to third light sources each emitting a light beam each having a first to third wavelength; an objective lens condensing each of the light beams emitted from the light sources on a signal recording face of an optical disc; a collimator lens provided between the light sources and the objective lens to convert a divergent angle of each of the light beams emitted from the light sources so as to obtain a parallel light beam; and a diffractive optical element provided between the collimator lens and the objective lens. The diffractive optical element includes first and second diffractive parts which respectively diffract the light beam having the second wavelength and the third wavelength. The second diffractive part has a diffraction structure formed by a plurality of concentric ring zones, having first to fourth optical faces, each having a different height in an optical axis direction.
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