| 摘要 |
A device for optically scanning an information layer by means of a focused radiation beam. Radiation reflected from the information layer is made astigmatic by an oblique plane parallel plate and subsequently detected by a detection system. An electronic circuit derives a focus error signal, representing the distance between the focal point of the radiation beam and the information plane, from the electrical detector signals by using the high-frequency components in the detector signals. The influence of stray light falling on the detection system on the focus error signal is thereby reduced.
|
