Abstract: In an optical pickup apparatus, including a laser source arranged along an optical axis, a polarization beam splitter and an objective lens, wherein light emitted from the laser source is emitted on a recording plane of an optical-magnetical recording media as a converged beam, light beams reflected from the recording media of the optical-magnetical recording media are separated by said polarization beam splitter to obtain a predetermined polarized light component, a phase change means, which changes a phase of light passing through one side of said optical axis and a phase of light passing through another side of said optical axis by a predetermined angle, such as wavelength plate, a phase retardation type prism and a combination optical rotation plate, is provided between the polarization beam splitter and the objective lens, and, an optical detection element, which detects the light polarized by the polarization beam splitter, is provided at a side intersecting the phase change means of the polarization be

Abstract: A head position controlling device in which the head position may be controlled accurately even with a magneto-optical disc having regions with different reflectance values. A gap sensor consisting of a light emitting element 5 and light receiving elements 6 and 7 are arrayed along the track direction of a magneto-optical disc to prevent unequilibrium in the volume of received light at the light receiving elements 6 and 7.

Abstract: An optical type record card reader according to the present invention is provided with a line sensor (10) for reading an information by a reflected light from a track of an optical type record card (1) irradiated by a light source (4) and in which optical type record card an information is recorded on a record medium (1A) as a plurality of parallel tracks which can be read out optically, a cylindrical lens (11) located rotatably between the optical type record card (1) and the line sensor (10) and an azimuth error detecting circuit for detecting an azimuth error generated between the track and the line sensor (10), wherein the cylindrical lens (11) is rotated by the detected output of the azimuth error detecting circuit to thereby correct the azimuth error. Thus, it becomes possible to correct the azimuth error of the projected image a sub-track of the optical type record card onto the line sensor smoothly, highly precisely and rapidly by the rotation of the cylindrical lens.