| 摘要 |
PURPOSE:To achieve higher defect inspection accuracy, by projecting two pulse like laser lights in opposite phase each other onto a recording medium to detect a defect by a time deviation signal of the detection signal of the two laser beams based on the defect. CONSTITUTION:Pulse like laser lights in opposite phase each other are emitted from two modulators 18 and 19. A beam splitter 23 emits the two modulated laser beams to a recording medium 12 as arranged parallel at an interval equivalent to the beam diameter. The reflected lights of the two lasers by the medium 12 are reflected with a beam splitter 24 after passing through a pickup lens 26 and 1/4 wavelength plate 25 and enter a detector 13. The detection output from the detector 13 is inputted into a signal processing section 14 which detects a time deviation signal of two detection signals based on defects on the medium 12 as defect signal. Thus, the defect inspection accuracy can be improved.
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