| 摘要 |
PURPOSE:To prevent an overcurrent to a light projecting element and circuits even when a subject is at infinite distance or has a low coefficient of reflection by providing a control circuit which controls a projected light output with a limiting means which limits the output of a light projecting means so that the output value does not exceeds an upper limit value. CONSTITUTION:When the output -Q of an RSFF6 goes up to a high level, transistor TRs 7 and 8 turn on and a capacitor C11 is discharged through a resistance R19; and a voltage applied to an IR photodiode rises gradually and turns on an AC basis synchronously with a CLK. An OP Amp operates as a constant voltage circuit together with TRs 13-15. Reflected light from a subject is incident to a semiconductor position detector 21 and IA and IB from electrodes A and B are inputted to switches 36 and 37 through OP Amps 24 and 25, frequency selecting circuits 26 and 27, etc., to calculate integral values VA and VB. Then, the output of the diode is increased by the sum signal and compared by a comparator 58 with VR1; when it is greater than VR1, an FF6 is set to prevent the overcurrent. |
