| 摘要 |
PURPOSE:To make a titled camera have necessary distance measuring accuracy with simple circuit constitution by inputting an output of a current-voltage converting circuit to a comparing circuit for comparing it with a prescribed voltage level through an amplifier without compressing it logarithmically, and obtaining a binary signal of far and near. CONSTITUTION:When a pulse light emission of a waveform is executed as a light emitting element 11, photocurrents I1, I2 of a PSD are brought to current- voltage conversion by operational amplifiers OP1, OP2, respectively, become a waveform and appear in its output terminal. These two signals are amplified differentially by an operational amplifier OP3. At the time of I1=I2, Vx=Vz, therefore, Vx and Vz are compared by a comparator COM, and when a focus is set as far and near at the time of Vx>Vz and at the time of Vx<Vz, respectively, an auto focus of two zones of far and near can be executed. A reference voltage of the comparator COM is set as Vc lowered slightly from Vx, and in case when reflected light is not returned, a result of being far is obtained. |
