CHECKING DEVICE OF SURFACE DEFECT

摘要

PURPOSE:To check a surface defect with high accuracy and high reliability by sampling a fixed information region by a separating circuit for fixed information region provided at a signal processing part and detecting the surface defect of a data recorded region. CONSTITUTION:A surface defect checking device 7 is provided with an optical system 8, a focus servo circuit 9 and a signal processing part 10. All additions of a 4-split detector 16 are carried out by an adder 21 and supplied to the part 10. The part 10 is connected to a computer. A fixed information region separating circuit 22 is provided at the part 10 to check a surface defect of a data recorded area A. An AND is obtained by an AND circuit 38 between the output 26 of a comparator 25 and the output 28 of a monostable multivibrator 27 to detect a surface defect signal 39 of the data recorded region from which a fixed information region B is sampled. In such a way, a surface defect can be detected with high accuracy and high reliability.