| 摘要 |
PURPOSE:To improve the detection precision of surface defects by preventing advantageously degradation of S/N of defect signals due to variance of illumination to a material to be examined and variance of the temperature of the material itself. CONSTITUTION:With respect to an electric signal from a photoelectrically converted visible region light, a bias is applied to the signal of level ''0'' between video signals by an unblanking circuit 1, and the preprocessing of low-pass filtering processing is performed. After the input signal is so adjusted in an AGC circuit 2 that its average level is within a certain level range, an original signal B outputted from the circuit 2 is divided by a signal A, which is obtained by processing the signal B in an LPF3, in a dividing circuit 4. The output from the circuit 4 is converted to a floating binary. Since S/N is raised effectively by this dividing processing, defect signals are accurately extracted without failures. |
