| 摘要 |
An optical pickup apparatus includes: one laser beam source for emitting two laser beams having respective optical paths parallel to each other and wavelengths different from each other; an optical-axis aligning means adapted to make the laser beams coaxial with each other; a collimating lens; a reflecting mirror; and an objective lens. A laser beam reflected at a high or low density disk takes the incoming path backward, passes through the optical-axis aligning means, is incident on a photo-detector, and converted thereby into an electrical signal. The optical-axis aligning means is structured such that one kind of dielectric multilayer film is formed on a transparent substrate, a transparent plate is attached on the one kind of dielectric multilayer film, and that another kind of dielectric multilayer film is formed on the transparent plate, and has its reflectance varied according to the wavelength of the laser beam.
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