| 摘要 |
PURPOSE:To improve the S/N ratio by installing No.1 and No.2 low pass filter performing the low pass filtering respectively of outputs of No.1 and No.2 synchronous rectifying circuits and preventing mutual interference between No.1 luminous element and light-receiving element as well as No. 2 luminous element and light-receiving element. CONSTITUTION:Pulse generators 10, 11 generate pulse signals of mutually different frequencies, allowing pulse lighting of No.1, No.2 luminous elements 6, 7. Luminous quantity passing through a slit by rotation of rotary slitted plate 1 becomes outputs of No.1, No.2 of light-receiving elements 4, 5 and they are subjected to a synchronous rectification by synchronization with the pulse signals respectively. Outputs of synchronous rectifying circuits 16, 17 are delivered to each low pass filters 18, 19 as outputs and for instance, even if light of No.2 luminous element 7 is incident to a light receiving element 4, an output increment (noise) of light-receiving element 4 by an incident light from a luminous element 7 can be eliminated. |
