Optical pickup device and focal error detecting device therefor and wave aberration and focal error detecting device therefor

Abstract

An optical pickup device includes an irradiating optical system for converging a light beam to form a spot on a recording surface via a light-transmitting layer of an optical recording medium, and a photodetection optical system for converging return light reflected and returned from the spot on a photodetector. The device detects wave aberration and focal error of the light beam. A diffractive optical element is disposed on the optical axis of return light in the photodetection optical system and provided with an annulus. The diffractive optical element annularly extracts, from return light, ray components in the vicinity of a predetermined radius on a pupil on the emitting pupil surface of the irradiating optical system, which is affected by the wave aberration generated in the optical system. The photodetector contains first light receiving components for receiving the ray components transmitted and extracted by the annulus, and second light receiving components for receiving at least some of the ray components other than the ray components transmitted by the annulus. The device further includes a focal error detecting circuit connected to the first light receiving components and which detects the focal error of the light beam on the basis of a subsequent photoelectrically converted output. The device may include a wave aberration error detecting circuit connected to the second light receiving components and which detects the wave aberration of the light beam on the basis of a subsequent photoelectrically converted output.