/ Optical pickup apparatus for capable of detecting thickness variation of recording medium and/or compensating spherical abberation generated by thickness variation thereof

摘要

Light splitting-detecting means for detecting the light beam reflected from the recording medium and passing through the objective lens and the optical path converting means into a plurality of optical regions, the optical beam being reflected from the recording medium and passing through the objective lens and the optical path converting means. Comprising a light detector or a light splitting device provided to divide / detect in consideration of the change in the amount of light distribution according to the thickness change of the light and a plurality of light detectors for receiving the light divided by each, and calculates the detection signal output from the light detector An optical pickup apparatus configured to detect a thickness change signal is disclosed. According to such an optical pickup apparatus, a change in thickness of the recording medium can be detected even in an optical system structure that does not include an astigmatism lens that causes astigmatism on the light-receiving side, and drives a spherical aberration correcting element or collimating lens along the optical axis. An actuator is further provided, and when the spherical aberration correcting element is driven by the detected thickness change signal, or the collimating lens is driven along the optical axis, spherical aberration caused by the thickness change of the recording medium can be corrected.