| 摘要 |
PURPOSE:To start detecting an objective body at an optional start position by providing a photodetecting element which moves in specific position relation with the body to be detected, and irradiating the body at positions where it advances by specific unit distance at specific intervals of unit time. CONSTITUTION:A counter 16 is reset once an initial value as the measurement start position is set in a shift register 14 from a microcomputer system, etc., at the start of measurement. The shift register 14 and counter 16 are supplied with pulses from an oscillator 15. Then, while a light emitting element corresponding to the value set initially in the shift register 14, i.e. at the detection start position 1 emits light one after another, the count up its counted value indicating the distance from the light emission position. As an advance of the light emission position is made, the light emitting element facing the photodetecting element which arrives at an objective position detection position emits light lastly. The photodetecting element 4 photodetects its light and generates an output signal. The shft register 14 and counter 15 stop operating by receiving the output signal. |
