| 摘要 |
PURPOSE:To enable the high speed detection of foreign matters adhered onto an object to be inspected while enabling high speed inspection corresponding to the adhesion state of foreign matters, by comparing the ratio of outputs from a pair of light receiving elements provided to the front and the back surfaces of the object to be inspected in corresponding relation to each other. CONSTITUTION:The laser beam 1 from a light source 8 scans the range L on a photomask 5 in an x-direction by a scanner 2 having a vibration mirror and light information from foreign matters adhered on the mask 5 is detected by light emitting elements 11, 13 corresponding to the front and the back surfaces of the mask. Each detection signals are respectively supplied to amplifiers 100, 101 and, when only the surface is irradiated with th laser beam 1, the signal e1 becomes larger than slice voltage VS while comparators 103, 104 each outputs a logical value ''1'' and an AND circuit 105 also outputs ''1''. When foreign matters are adhered to the back surface, a large amount of the laser beam 1 is subjected to positive reflection at the glass surface of the mask 5 and a part thereof irradiate the foreign matters on the back surface. Therefore, the output of the element 3 becomes smaller than that of the element 11 and the comparator 104 and the circuit 105 each outputs ''0''. |
