PROJECTION EXPOSURE DEVICE

PURPOSE:To obtain the central coordinate value of a synthetic picture in a short time by a wafer alignment mark and a reticle window by dividing pattern data up to an end point from a starting point for the scanning of a slit into two groups or more and acquiring the central coordinate value of the synthetic picture on the basis of selected threshold data. CONSTITUTION:The values of memorized points (a-d) are read by a processor 8, maximum values at the point (a) and the point (d) are compared mutually by a comparator 9 by controlling the processor 8, a smaller value is selected, and the point (a) is selected. The value is memorized onto another specified address in a memory 3. Minimum values at the point (b) and the point (c) are compared mutually through the same method, a larger value is acquired, and the value of the point (c) is memorized similarly to an address in the memory 3. Absolute values at the point (a) and the point (c) acquired are compared mutually, and the intersection coordinates I1, I2, I3, I4 of a pattern and the four points can be obtained by one-time check to the threshold value of m1 slightly smaller than the point (a) when m1 is determined in the threshold value (l) when the point (a) is larger. The four points are acquired, and a central coordinate value is arithmetically operated on the basis of procedure previously determined by a program 7.