Radial and Tangential Tilt Detection for Rewritable Optical Disks

Abstract

In an optical disk system which uses a short wavelength laser diode and a high numerical aperture objective lens, it is necessary to detect and compensate for the disk tilt, because the coma aberration deteriorates the read/write characteristics and the tilt margin becomes narrower. This paper presents a new radial and tangential tilt detection method for rewritable optical disks, which is based on the intensity distribution of the reflected light from the disk. This method features high sensitivity (about 0.37/° for radial direction and about 0.51/° for tangential direction) and is suitable for high-frequency servo operation. Moreover, it can be combined with the differential push-pull detection method and the land/groove detection method by using three beams. Experimental results have demonstrated the validity of this method.