| 摘要 |
PURPOSE:To enable separate inspection of a wiring pattern and a through hole part by a method wherein a reflected light signal from the wiring pattern and a gradation signal of a through hole transmitted modulated light signal are converted into binary- coded images by two independent threshold values respectively. CONSTITUTION:A gradation image (a) of a printed circuit board 101 obtained from an image-sensing device 104 becomes a synthesized signal of a wiring pattern signal and a fringe pattern image of which an image signal level is modulated in each line in a sub-scanning direction in a through hole area by transmissive illumination from below the board 101. After a wiring pattern part is amplified 106 with an ordinary amplification factor and a fringe pattern signal part is amplified 109 with such an amplification factor as to bring about nonlinear amplification, then, they are converted 108, 111 into binary-coded images by independent threshold values respectively. Thereby the binary-coded image c1 of the through hole area is made to be a circular fringe-like pattern being distinct and uniform in the sub-scanning direction, a through hole image can be separated from the wiring pattern part by a simple construction and with fidelity even when the board 101 is thick and wide, and the inspection for width, damage, etc., can be facilitated. |
