PURPOSE: To discriminate extactly a converging condition by a simple method by using a piezoelectric element which is brought into contact with a work piece for discriminating the converging state of the working beam projected to the piece to be worked on the piece to be worked.
CONSTITUTION: The amplitude of the output signal of a piezoelectric element 24 disposed in contact with a piece 23 to be worked is detected with a waveform detector 25. A control system 26 for a piece to be worked moving device 28 or a converging lens moving device 27 is driven by said detected signal. Laser light is first irradiated from a work beam source 21 and the signal in this stage is detected by the detector 25. If the signal is larger than the specified amplitude, the lens 22 or the piece 23 is moved by the device 27 or 28 and the position where the amplitude of the output signal is min. is found by repeating such operation. The optimum position for working is thus detected.
MIYAZAKI TOSHIYUKI
YOSHIOKA TOSHIAKI
SHIRAI YASUYUKI
SADA TOSHIO
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