| 摘要 |
PURPOSE:To attain a small-sized and inexpensive transmitter by inhibiting the reception of light to itself while its own pulse is projected and using a different modulation frequency to each projector, thereby eliminating the need for a processing circuit preventing a malfunction due to reflection. CONSTITUTION:The frequencies of a pulse oscillation circuit 12 of two transmission/reception units 111, 112 are deviated slightly by intension. As a result, projection signals P1, P2 emitted from opposed light emitting elements 14 are overlapped by one pulse at every period and parted completely in other time zone. In sending the H state to the opposite side by the units 111, 112, the pulse light modulated by the frequency is sent and in sending the L state, the element is not lighted. When the signals P1, P2 are sent mutually, the output of each photodetector 15 is given to detection circuit 18 only when an analog switch 17 is not nonconductive by inhibition signals F1, F2 from its own projector A. When the signals P1, P2 are overlapped, the pulse output is only missing and the light reception signal obtained from the incidence of the pulse light from the opposite party is all inputted to the circuit 18. |
