| 摘要 |
PURPOSE:To perform measurement reducing the fatigue of an observer without being restricted by the brightness of a measuring environment, by observing the state of an object to be measured illuminated by a light source through the shutter part of a liquid crystal element and controlling the cycle of the opening and closing operation of the shutter part. CONSTITUTION:A liquid crystal element 1 is arranged in opposed relation to the front side of a rotary body 14 illuminated by a light source lamp 13. A signal with predetermined frequency is oscillated in the oscillator 9 of a control system for the opening and closing driving of the shutter part A of the element 1 and set to a predetermined phase in a phase shifter 11 by the signal from a phase control signal generating circuit 10 to be sent to a liquid crystal driving circuit 12. An observer visually confirms the marker 15 of the rotary body 14 through the shutter part A and adjust the frequency of the signal in the oscillator 9 so that the marker 15 looks like a stop state to adjust the phase of the signal in the circuit 10. The oscillation frequency of the oscillator obtained by this adjustment shows the number of rotations of the rotary body 14 and measurement reducing the fatigue of the observer can be performed without being restricted by the brightness of measuring environment.
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