| 摘要 |
PURPOSE:To obtain a more highly accurate waveform with an increase in the quantity of light, by providing near both ends of slits of respective tracks one or more auxiliary slits with the width less than that of each track while a fixed slit corresponding thereto is made up of a plurality of flit pieces. CONSTITUTION:A rotary disc 1 has four tracks. The first track are provided with a slit 3 and slits 41 and 42 each with a width (W) at an interval (W) from both ends thereof. A fixed slit 2 is provided with slits 51 and 52 with an width 2W. Other tracks are provided with slits likewise and the disc 1 is turned in the direction of arrow, a photodiode produced an output when the rear (a) of the slit 41 is at a position P1 and the output becomes constant at a position P1. Afterward, the output rising at a position P3 and P6 becomes constant at the positions P5 and P7 and at its highest at the position P7. During the period, the output crosses a reference voltage S1 set at the position P4 and the size (large and small) relationship of the value inverts with each other. The output is proportional to a passing slit area to improve the rising accuracy of a square wave.
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