OPTISCHE ABTASTVORRICHTUNG

摘要

Data are stored on top of one another both by means of pits and in a magnetic layer on an optical substrate which is a combination of an optical and a magneto-optical substrate. Data stored both via the pits and in the magnetic layer can be read out simultaneously by means of a suitable optical scanning device with the aid of a light beam. The light reflected by the substrate (CD) is directed to a first or a second photodetector (PD1, PD2) depending on its direction of polarisation by means of a first polarisation beam divider (PO1). The differential signal of the output signals from the first and second photodetector (PD1, PD2) formed in a first differential amplifier (DV1) is the crosstalk-affected data signal (MNS) obtained from the magnetic layer of the substrate. The light reflected by the substrate (CD) is also diverted via a lambda /4 plate (PL3) and a second polarisation beam divider (PO2) to a third and a fourth photodetector (PD3, PD4). The differential signal ES of the output signals of the third and fourth photodetectors (PD3, PD4) formed in a second differential amplifier (DV2) is essentially the interference signal causing the crosstalk which originates by reflection at the edges of the pits and is also superimposed on the magneto-optical data signal (MNS) at the output of the first differential amplifier (DV1). The differential signal ES is taken via an amplifier with an amplification lower than 1 to the inverting input of a third differential amplifier (DV3) whose non-inverting input is connected to the output of the first differential amplifier (DV1). The crosstalk-free magneto-optical data signal (MS) may be taken from the output of the third differential amplifier (DV3). This device can be used in magneto-optical recording and playback devices.