| 摘要 |
PURPOSE:To hold a constant output level independently of the luminous quantity change due to the change in the lapse of time in a light emitting element by applying an output of a light receiving element detecting the luminous quantity of the light emitting element to a reference potential setting variable resistor. CONSTITUTION:When the emitted light quantity of the light emitting element 4 is changed by the change in the lapse of time, the output of the light receiving element 1 is changed. On the other hand, since the output of the added light receiving element 5 is impressed to the reference potential setting variable resistor 2, the light receiving element 5 detects the luminous quantity change due to the change in the lapse of time of the element 4 so as to change the reference potential depending on the change at the same time. Thus, the output as the encoder is kept constant.
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