| 摘要 |
PURPOSE:To prevent the variation of the distance measuring accuracy through the feed back control of the amount of light emitted from a light emitting means to always make the amount of light received by a light receiving means constant. CONSTITUTION:Pulse modulated light emitted from a light emission element 1 and reflected on a measuring objective 4 is received by a semiconductor position detector 5 at the light receiving point x in the light receiving surface 5a. The detector 5 provides position signals in the form of signals currents IA and IB corresponding to the light receiving point. The light receiver 5 generates continuous signal voltages VA and VB corresponding to the currents IA and IB, respectively. An adder 14 adds the signals VA and VB, then sends the result to a pulse modulation circuit 2. The circuit 2 generates oscillating pulses P0, the frequency of which varies in inverse proportion to the signal VA+VB. Thus the element 1 is subjected to pulse modulation and to feedback control so that the amount of light received by the detector 5 is always kept at a fixed level even if the distance X from the measuring objective 4 varies. |
