| 摘要 |
PROBLEM TO BE SOLVED: To enhance accuracy in the adjustment of shift of the optical axis incident to heating of a laser beam source, or the like, by determining the oscillation duty of the laser beam and adjusting the optical axis of the laser beam based on the oscillation duty thus determined. SOLUTION: Relation between the variation of oscillation duty and the shit of optical axis is measured previously and stored in a memory in the form of a lookup table or displacement information by determining a function according to an approximately formula. A duty detector 60 for detecting the oscillation duty of the laser beam is provided in an exposing light source 12. A controller 20 retrieves or calculates a corresponding correction amount from the displacement information in the memory 20a based on the detected oscillation duty and delivers a signal for adjusting the optical signal to first optical axis correction systems 23, 24.
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