FOCUS ERROR RETESTING METHOD FOR OPTICAL DISK DRIVER

摘要

The method for detecting a focus error of an optical disk driver detects the focus error by using a thin film having on but sides a reflecting film of high reflecting ratio in order to detect a concentrated focus state of an object lens concentrating on light spot. The method is arranged that incident beam is concetnrated into the object lens, this concentrated beam is reflected on the optical disk, and on its opposite side a light detecting apparatus is set, thereby a change of a beam incidence angle entering the thin film is separated into the reflected beam so that the focus error signal can be detected.