RANGE FINDER FOR AUTOFOCUS CAMERA

摘要

PURPOSE:To obtain a signal indicating which of a long, an intermediate, and a short distance an object is through a comparing means and a discriminating means by providing the comparing means which compares two signals with each other and the discriminating means which discriminates the level of either of those two signals or their superposed signal. CONSTITUTION:A judging circuit B which calculates the difference between output voltages of current/voltage converting circuits IVC1 and IVC2 and judges whether the difference is larger than a constant value or not consists of a differential amplifier OP3 which calculates the difference between outputs I1 and V2 and a comparator COM3 which compares the difference value Vx with the constant value. A judging circuit M which judges whether the sum of the outputs V1 and V2 of the current/ voltage converting circuits IVC1 and IVC2 is larger than a constant value or not consists of an amplifier OP4 and a comparator COM2. The judging circuit M checks whether the quantity of photodetection of a photodetecting element 4 is larger than a constant value or not and judges that the object is at a long distance when the quantity of photodetection is smaller than the constant value. Then, the judging circuit B judges that the object is at a short distance when I1>I2 and judges that the object is at an intermediate distance when I1