| 摘要 |
PURPOSE:To identify a defect positively even when a diffraction pattern is deviated with changes in line, by judging the defect from the number of imaging areas of the diffraction pattern with an area sensor. CONSTITUTION:Reflected light 23 from an object 21 to be inspected is condensed with a condenser lens 24 to from an image on an area sensor 25 and after a diffraction pattern obtained is converted into an electrical signal, an output of the area sensor is read sequentially to be fed to a comparison section 28, which compares an output (a) of the area sensor with a reference signal (b) of a reference signal generator 27 and the output of the area sensor moves to a high level when exceeding the signal (b). A gate pulse with the pulse width proportional to an occupied area of the imaging area is obtained and then, sent to the subsequent imaging area judging section 29. here, a sampling pulse (d) is made to pass within the time of a gate pulse (c) to acquire a pulse signal corresponding to the number of imaging areas and then, the signal is sent to a counting defect judging section 33. The counting defect judging section 33 counts the pulse signal (e) to compare counts (f) with an upper limit value (g) and a lower limit value (h) from an upper/lower limit value setters 31 and 32 and outputs a defect signal.
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