198072 ⎘
Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation , reproducing using an optical beam at lower power ; Record carriers therefor; Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for focusing only; Focus-error methods other than those covered by - Skewed beams methods (using an angled beam, i.e. a beam which is reflected from the disc at an angle different from 90°)