| 摘要 |
PURPOSE:To detect minute contamination and a foreign material without being influenced by wrinkles, bending, uneven reflection of an object to be tested, by a method wherein a difference between adjoining detecting signals of a scanning type photoelectric conversion camera is processed in a numeral manner. CONSTITUTION:An image of a pattern of an object to be inspected is formed on a secondary sendor 1' of a scanning type photoelectric conversio camera. Information on the secondary sensor 1' opens an analogue gate circuit 4 in order by means of a clock pulse to feed it into an A/D conversion circuit 5 where it is brought to a digital manner to enter a memory 6 for storing therein. By means of a start signal from a process start signal generating circuit 12, a data is read from the adjoining address of the memory, and a data difference is found in a reduction circuit 7 to store the difference in a memory 8. The data in the memory 8 is sent to a numeral code conversion circuit 18 from a numeral decision circuit 15, wherein the upper and the lower limit value are set, and a decision circuit 18 compares the output with a data from the memory 8. If a signal exceeding the upper and the lower limit value exist, an output signal is generated at a terminal 19. |
