An optical inspection system has been developed that detects parameter fluctuations in an optical disk pregroove structure (groove pitch, depth, and width). This optical system was devised using a laser diffraction phenomenon. Groove parameters are measured and calculated from diffracted-light intensity ratios; the groove width is calculated from the second-order diffracted-light intensity ratio to that for the first order. The groove depth is given from the first-order ratio to the zeroth-order light intensity. In addition to this groove parameter inspection, this system is capable of groove defect detection using a spatial filter whose passband is designed to be between the zeroth- and the first-order diffracted-light areas.
© 1984 Optical Society of AmericaPDF Article