| 摘要 |
PURPOSE:To miniaturize the device and simplify assembly adjusting operation by eliminating the alignment of striped pattern image to a specified position on an image sensor by a method wherein, in the contrast inspection of a striped pattern projected on a wafer, bright and dark position is automatically detected to measure the level. CONSTITUTION:Striped pattern detection signals 81, 82 of forward and backward focusing are inputted to an out-of-focus discriminating circuit 10. To calculate the contrast of both striped pattern detection signals of forward and backward focusing by the same process, a signal 53 through an input signal coamplifier 21 is inputted to a sample hold 22 and a comparator 26 comprising a peak detection circuit. Besides, the other input terminal of comparator 26 is impressed with the sample hold output 54 to compare each picture element with one another. Therefore, the sample hold output 54 will be peaked at the point whereon the level of both signals is inversed to be held to the other sample holds 23, 24. Furthermore, sample commands 56, 57 are generated by a control pulse generator circuit 27. |
