Optical pickup device and optical disk playback device provided therewith

Abstract

There is provided an optical pickup device comprising a laser light source for emitting a laser beam, an object lens for focusing the laser beam onto the recording surfaces of layersandof an optical disk and condensing the laser beam onto the recording surfaces, photodetectors for receiving the laser beam reflected by the optical disk, and a diffraction grating for diffracting a part of the reflected laser beam toward the photodetectors, wherein data can be simultaneously written to layersand. The photodetector detects the reflected light from layerafter being refracted by the diffraction grating, and detects the reflected light from layerwithout being refracted, so that the data of layersandcan be simultaneously read. Thus, data can be simultaneously read from and written to the recording surfaces of a plurality of layers of an optical disk.