FOCUS ERROR SIGNAL DETECTOR AND FOCUS ERROR SIGNAL DETECTION

摘要

PROBLEM TO BE SOLVED: To prevent the deterioration of error rate characteristic with respect a focus offset in an astigmatism method and to remove a noise entering a focus error signal when grooves consisting of lands and grooves are scanned crossingly. ;SOLUTION: The light reflected by an optical disk 9 returns along the same route as an incident route and is reflected by a polarization beam splitter 5 and thereafter, the light advances along the route different from the incident route. The light reflected by the polarization beam splitter 5 is converged by a converging lens 11 and passes optical parts integrated with a concave lens 12 and a cylindrical lens 13. The light further passes a diffraction grating 14, and the light is dispersed. Quadrisected sensors 15 detect the dispersed light and outputs the signal meeting the detected light. The influence of the light generated by diffraction at the optical disk 9 may be expelled by superposing the zero order light and ±1st order light generated by the diffraction grating 14.;COPYRIGHT: (C)2001,JPO