Abstract: In an apparatus for recording and/or reproducing information on and/or from an optical record medium having a control track in which information for identifying the relevant optical record medium has been recorded, plural sets of operational condition data for various kinds of optical record media which will be set on the apparatus have been previously stored in a memory unit. Information recorded in a control track of an optical record medium set on the apparatus is first read out to identify a kind of the optical record medium, and then a set of operational condition data is selectively read out of the memory unit in accordance with the identified kind of the optical record medium. The writing and/or reading power of a light beam impinging upon the optical record disc is controlled in accordance with the read out operational condition data to effect the recording and/or reproduction in an optimum manner.

Abstract: A light beam linearly polarized is incident on a substrate for a disc not a right angle, but at an an oblique angle with respect to the substrate surface, while holding constant an angle .kappa. between the plane of polarization of the linearly polarized light and the incident plane, and the intensity of the leaked light passing through an analyzer set in a crossed Nichol state with respect to the linearly polarized light is measured while changing an angle (azimuth angle .PSI.) between the incident plane and a reference line, such as a line extending in the radial direction of the disc substrate. These measured values are compared with the calculated values derived from the theoretical formula for determining the respective magnitudes of the three refractive indices.

Abstract: In a method of recording, in the over-write mode, bivalent signals "0" and "1" on an opto-magnetic record medium having a ferrimagnetic material whose compensation temperature is higher than a room temperature, but is lower than a Curie temperature, an external magnetic field is applied to the record medium, and a laser light beam is modulated in accordance with the bivalent signals. When the bivalent signal "0" is to be recorded, the laser light beam is set to a lower power level and the ferrimagnetic material of the record medium is heated to a temperature higher than the room temperature, but lower than the compensation temperature so that the ferrimagnetic material is magnetized in the same direction as the external magnetic field.

Abstract: A surface of the thermoplastic polyester film which has stickiness after having been heated is treated with a monocarboxylic acid so as to convert hydroxyl groups on the film surface into corresponding ester groups by reaction with the acid. Further, the film surface is treated with a monohydric alcohol so as to convert carboxyl groups on the film surface into corresponding ester groups by reaction with the alcohol. Thus, the stickiness on the film surface is eliminated.