| 摘要 |
PURPOSE:To detect even a small defect existing on a guide groove of a disc, by varying the feed speed of a linear motor and revolutions of a spindle motor to always keep a scanning speed constant, when a fine spot of laser light scans over a guide groove in the surface of the disc. CONSTITUTION:A drive signal is outputted to a spindle motor 2 to scan along a guide groove in the surface of an object to be inspected placed on the spindle motor spirally with light irradiated from a light head 7 while a linear motor 4 is moved radially based on a radius position signal outputted from a radius position detector 5 so as to keep the scanning speed constant. The surface of a disc 1 is irradiated with a fine spot of laser light and an electrical signal of the reflected light thereof is converted into digital from analog synchronizing a rotation position signal, and the data thus converted is memorized 10 sequentially at a specified address. Thus, the length of a defect is determined 9 based upon the electrical signal and the results of inspecting the defect is displayed. |
