Optical pickup device and focus control method

摘要

An optical pickup device includes a detection-use condenser lens for focusing a reflected light from a disk of a light emitted from a light source; a hologram element for dividing a light passed through the detection-use condenser lens into a light passed through a high numerical aperture region and a light passed through a low numerical aperture region; and a photodetector including at least a first light receiving element for detecting the laser beam which passed through the high numerical aperture region and a second light receiving element for detecting the laser beam which passes through the low numerical aperture region. Based on output signals from the first light receiving element and the second light receiving element, a focus error signal FE1 and a focus error signal FE2 are prepared respectively. According to an output value of the photodetector, a focus control is performed based on the error signal FE1 or the focus error signal FE2.