Since the laser power detection circuit 11 often has an abnormal emission slice level n1 of about 1.5 mW set relative to the signal m of about 1 mW, the detector 11 detects this interval as the abnormal emission, thus producing {HEAD ~ the output signal p} of {TAIL ~ H1 voltage} by which the laser drive circuit 21 is controlled to stop the beam emission of the laser beam source 1 
Since the laser power detection circuit 11 often has an abnormal emission slice level n1 of about 1.5 mW set relative to the signal m of about 1 mW , the detector 11 detects this interval as the abnormal emission , thus producing { HEAD ~ the output signal p } of { TAIL ~ H1 voltage } by which the laser drive circuit 21 is controlled to stop the beam emission of the laser beam source 1
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