PURPOSE: To enable discrimination of distance measuring condition with a stable operation by changing characteristic of a bandpass filter circuit.
CONSTITUTION: As a clock pulse passes through an AND gate 3, a transistor 4 repeats conduction and interruption and an infrared light emitting diode IRD 5 lights in a pulse. The projection light is reflected from an object for distance measurement and received with a semiconductor light position detecting element 6. Received light outputs at the points (a) and (a') are generated overlapping a DC component by natural light. In BPFs 13 and 15, as resistance values of FETs 14 and 16 decreases as resistance component, a sweeping is done from the high to low impedance with respect to emission frequency. Output voltages Vf and Vf' at the points (f) and (f') after DC amplification circuits 21 and 23 via smoothing circuits 19 and 20 rises gradually from the specified value.
YOSHIKAWA YUKIO
KUROSU TOMIO
SASAKI TOYONORI
MATSUMOTO KUNIO
NAMIOKA AKITA
