| 摘要 |
PURPOSE:To automatically meter the offset amount during the photo-scanning optical systems of a positioning device in a period of time during a laser scanning starting point and the output timing of the reference signal to synchronize with the laser scanning and to enable to correct the time-metered value of the alignment detecting signal on the basis of the offset amount in the positioning processing to be performed hereafter. CONSTITUTION:Reference marks 11 and 11' are scanned by the left and right objective detecting systems and the time interval during the detected signals obtainable is metered. Subsequently, the left and right detecting systems are made to drive on the basis of the metered value and the reference positions of the left and right detecting systems are exactly set in such a way that these reference marks 11 and 11' come to the reference positions such as the centers of the detecting systems. Then, a time during the photo-scanning starting point in each detecting system, that is, the rising point of the synchronizing signals and a point to scan the reference mark 11 or 11' is metered. Moreover, the time-metered offset amount during the foregoing detecting systems based on the metered value, that is, the temporal offset amount during the mean value of the foregoing metered values in the left and right detecting systems and the output timing of the reference signal in the reference state that is decided in the state of design or experimentally is calculated. In the positioning processing to be performed hereafter, the time-metered value of the alignment detecting signal is corrected on the basis of this offset amount. |
