| 摘要 |
PURPOSE:To sense a position with high precision by memorizing correction value data at every small region in the image sensing plane of a first position sensing means and correcting positional information obtained by the first position sensing means by a corresponding correction value. CONSTITUTION:The image of a mark on a wafer taken by a CCD camera 1 is converted into a digital signal by a CCU 21 and an analog-digital converter 22 and analyzed by a position sensing section 23 at a correction-value take-in mode. Consequently, the positional information of the wafer obtained is transmitted over a CPU 24. On the other hand, an optical interference data from a laser interferometer received by a receiver 5 is sent to the CPU 24 through an interface 27. The CPU 24 compares these data and computes a correction value in the region in an image plane, and the correction value is memorized to a non-volatile memory 25. When the position of the wafer is detected by a normal detection mode, positional information from the CCD camera is corrected by the correction value memorized to the non-volatile memory 25, thus sensing the position of the wafer with high accuracy. |
