Abstract: An optical pick-up is provided. The optical pick-up includes a light source, a first objective lens configured to focus light emitted from the light source on a high-density optical information storage medium, a photo-detector configured to detect a signal by receiving light reflected from the high-density optical information storage medium, an optical-path changer configured to convert a travel path of incident light to allow the light emitted from the light source to proceed toward the high-density optical information storage medium, and to allow the light reflected from the high-density optical information storage medium to proceed toward the photo-detector, and a blocking device disposed in an optical path of signal light reflected from a target reproducing/recording layer of the high-density optical information storage medium, passes through the first objective lens, and proceeds toward the photo-detector.

Abstract: A phase difference layer 12 and a reflection layer 13 are provided. Then, adjustment is performed such that the phase difference layer 12 and the reflection layer 13 impart a predetermined phase difference to light having a particular wavelength bandwidth or plural kinds of light of different wavelengths that enter in an oblique direction relative to the normal direction of the plane of the phase difference layer 12. By virtue of this, the light 16a that goes forward and backward through the phase difference layer 12 and then exits the layer has an ellipticity ? of 0.7 or greater. Thus, in particular, when this wave plate is employed in an optical head device, the function of reflection and the function of a ¼-wave plate are integrated. Thus, stable recording and reproduction of an optical disk are achieved, and size reduction is achieved in the optical head device.

Abstract: A conventional optical pickup apparatus has a problem that due to multiple optical paths provided therein, the number of parts of optical systems becomes larger and a time required for attaching the parts and adjusting an optical axis becomes longer. In optical pickup apparatus 1 of the invention, a major part of optical path 21 of a laser beam emitted from first semiconductor laser device 2 and optical path 20 of a laser beam emitted from second semiconductor laser device 3 are shared. Then, the laser beam reflected from the optical disk 17 (optical feedback) is received by shared PDIC 19 and light-receiving processing is accurately performed on the laser beam as a light detector. With this structure, the number of parts of optical systems disposed in the optical pickup apparatus 1 is reduced, an attachment operation of the parts becomes easier, and a time required for adjusting an optical axis is reduced. Thus, an operational efficiency is greatly improved.

Abstract: According to one embodiment, an information reproduction apparatus includes an information acquisition unit, an error detection unit, and a control unit. The information acquisition unit is configured to irradiate a reference beam, convert the reference beam into a luminance signal, and output the luminance signal when reproducing an information recording Medium. The error detection unit is configured to detect at least one selected from a first error and a second error by extracting a feature extraction quantity from the luminance signal. The first error is of an irradiation angle of the reference beam. The second error is of at least one selected from a temperature and a wavelength of the reference beam. The control unit is configured to control at least one selected from the irradiation angle and the at least one selected from the reproduction temperature and the wavelength of the reference beam using the second error.