| 摘要 |
PURPOSE:To control the range accurately, by a method wherein the difference between two analog signals is controlled to be zero, and the range between an object to be measured and the reference surface is detected without utilizing any divider. CONSTITUTION:A position sensor 8 outputs two analog signals corresponding to the incidence position of light. Two analog signals A1 and A2 detected and outputted from the sensor 8 are applied to an amplifier 11 consisting of an operational amplifier 11a and a resistor 11b and to a variable gain amplifier 12 consisting of an operational amplifier 12a and a variable resistor 12b, respectively. An amplified output B1 is applied to a subtractor 15, and an amplified output B2 is applied to a subtractor 19. The subtractors 15 and 19 apply two subtraction outputs D1 and D2 to a subtractor 26 and an adder 27, respectively. Then, a subtraction output E from the subtractor 26 is applied to a variable voltage supply 30, and thus, the position of an optical lens-barrel 1 in the vertical line is determined. An addition output F from the adder 27 is applied to a light source control circuit 5 and to a level detector circuit 31, respectively. |
