| 摘要 |
PURPOSE:To perform a highly accurate and highly reliable sensing under an environment with a large disturbing noise by employing a received light signal as effective data subject to being below a specified value in the quantity of light received with a photoelectric sensor when a specified modulated light is projected to an object. CONSTITUTION:A modulated light above 10kHz is projected to a welding work 1 from a light source 10 through a projector controlling circuit 9 and mode to form a spot image 11 on a photoelectric sensor (PSD) 13 through a condenser 12. Light current signals X1 and X2 obtained from electrodes at both ends of the sensor 13 are inputted into an arithmetic circuit 17 via an amplification circuit 15 and a band pass filter 16 and a difference signal is divided by a sum signal to determine the image formation position, which is inputted into a signal processing circuit 18. On the other hand, the sum S of outputs X1' and X2' of the circuit 15 is obtained with an addition circuit 19 and is compared with the reference signal S0 from a reference setting circuit 20 with a comparator circuit 21. An image formation position signal detected for the time tS smaller than the value S0 is employed by the circuit 18. Thus, the sensing under the environment with a large disturbing noise can be done at a high accuracy and with a high reliability. |
