Information and data carrier optical disc drive

摘要

An optical disc drive includes a light convergence device (95) for converging a laser beam on to an optical disc (20), an adjustment or positioning device (10-16) for the adjustment of the light-convergence device in the thickness direction of the optical disc. There is also a detection device (8, 9) for detecting any deviation of the focus signal on the basis of the reflected light. The detection device (8, 9) is designed to detect any change in the focus deviation, or error signal, when the laser beam converges on to the substrate or the recording layer, while the light convergence device is adjusted or positioned. The substrate thickness is assessed (16) on the basis of this change in the focus deviation or error signal.