| 摘要 |
PURPOSE:To enable position detection with high detection efficiency and high precision by using alignment marks having plural peak values in an integrated density distribution, and enabling binary coding to be applied to many kinds of wafers. CONSTITUTION:A video signal is outputted through a video amplifier 31, an A/D converter 32, and a latch 33 to an X-direction and Y-direction addition block. Memories 40, 36 store the output data of latches 39, 35, respectively. A control circuit 41 controls timing and sequence of a prealignment detection circuit and controls memory 36. A control circuit 42 controls the memory 40. A mu processor connects through a data bus to the memories 36, 40. When in measuring the distance values of the alignment marks, the distance between the central positions of the 2 peaks are measured as said values, large change is not given even if the range of setting the slice level is enlarged in binary coding, thus permitting the position detection to be achieved with high detection efficiency and high precision. |
