| 摘要 |
PURPOSE:To enable countermeasure to products, simply by changing a set level regardless of a change in pattern of a lead frame, by counting the time of transmission light of a laser beam varying clock frequency in response to the velocity of the laser beam scanned. CONSTITUTION:As a motor 4 runs at a fixed rotational speed, the moving speed of a scanning laser beam on a lead frame is higher toward the periphery and hence, when a detection level is set for a fixed time, the distance to be judged is different between the center and the periphery. Then, the measurement of time is done with a processing circuit 12. When the time during which the laser beam is transmitted or shielded is counted with a clock oscillator 15, position information of a moving stage 5 is inputted from a control circuit 14 to change the clock frequency of the oscillator 15 corresponding to the position thereof so that the number of pulses counted and the moving distance of the scanning beam will be always constant. With such an arrangement, an abnormal shape is judged by detecting how much the number of pulses differs from a set value.
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