Abstract: A recording or reproduction device with a three-point scanning arrangement compatible for use with recording media having different track spacings. The invention makes it possible, without changing the setting of the three-point scanning system, to use recording media having different track spacings. According to the invention, the three-point scanning system is set in such a way that the scanning center points have a lateral spacing from one another which is within a range of a first product, formed by a first predetermined value and the first track spacing, and a second product, formed by a second predetermined value and the second track spacing, the range being less than 8 percent of the value of the first product.

Abstract: Tracking error signal in an optical read/write device, such as a CD ROM, are fine tuned for deviations in the positions of the lens structure normal to the recorded medium to provide more precise tracking control. Track error signal is developed by means of DPD-TE circuitry, using for example, signals from a four quadrant photodetector. Selected pairs of the signals from the photodetector are summed and the sums are differenced to develop an intermediate signal. The intermediate signal is amplified with a gain proportional the reciprocal of the intensity of light received by the photodetector, and thereafter combined with the track error signal to provide a corrected track error signal.

Abstract: A device for corrected-focus scanning of information while recording on and/or replaying information from a recording medium is based on a radiation source which provides a scanning beam, a focusing objective lens and a radiation-sensitive detector system. A diffraction element for deriving a focus error signal is arranged in the space between the focusing objective lens and the detector system, at a predetermined, fixed distance, the diffraction element being designed such that two focus planes result which are physically separated from one another. The detector system is located between the separate focus planes such that the size ratios, which change in the event of defocusing, of the symmetrically imaged focus spot can be used to derive the focus error signal.

Abstract: An optical scanning device having a holographic optical element for receiving a scanning beam which has been influenced by a recording medium. One aspect of the invention is to use an optical spatial filter to obtain the information signals. A further aspect is to image the entire area of the scanning spot on only one detector and to use the complete light component, as a result of which the power component is increased and the requirements for adjustment of a plurality of elements with respect to one another are reduced.