PROCESS AND CONNECTION ARRANGEMENT FOR COMPENSATION OF OFFSET VOLTAGE ARISING IN CIRCUITS FOR REGULATION OF FOCUS AND/OR FREQUENCY

摘要

A method for compensating offset voltages selectively in a focusing circuit that focuses a beam from a source of light on a recording medium and in a tracking circuit that positions a beam of light on data storage tracks on a recording medium. A beam of light reflected from the recording medium is directed onto a photodetector which has a plurality of photodiodes. The difference of the output voltages from the photodiodes is taken for generating an error signal which is stored as a reference during a first stage in open or closed state of the circuit selected. The selected circuit is then closed and a compensation parameter is supplied in a second stage to controls in the selected circuit. The compensation parameter is then varied until the error signal is substantially equal to the stored reference. The compensation of the offset voltages is independent of the tracking circuit, and the offset voltages in the focusing circuit can be compensated when the tracking circuit is closed.