| 摘要 |
PURPOSE: A stepper for sensing an error of a shutter is provided to prevent efficiently a process error due to a noise signal included in an output signal of the shutter. CONSTITUTION: A stepper is formed with a shutter drive unit(100), a shutter(120), a pulse counter unit(140), a shutter error sense unit(160), and an alarm generation unit(180). The shutter(120) is driven by an operation start signal outputted from the shutter drive unit(100). The shutter(120) outputs a square wave signal according to the operation start signal. The pulse counter unit(140) is driven by an operation start signal outputted from the shutter(120). The pulse counter unit(140) counts the square wave signal outputted from the shutter(120). A timer is mounted in the shutter error sense unit(160). The timer is driven by the operation start signal of the shutter drive unit(100).
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