| 摘要 |
PURPOSE:To make it possible to inspect not only the existence of flange cracking and a hole but also sticking of foreign matter, deformation, etc., by detecting a difference in electric signal between the quantities of reflected light from two parts of a can adjoining each other and equal in area. CONSTITUTION:When faces A to D are obtained by sectioning by imaginary line 71 in the diameter direction of a can and imaginary line 72 in the circumferential direction, detection head 40 is so arranged that light reflected by surface A is detected by photo transistor (a) and light from surface B is by surface (b); and light from surface C is detected by transistor (c), and light from D by (d). Now, if surface D has a crack, electric signals generated by transistors (a) to (d) are amplified secondarily by main amplifier 51 of decision unit 50. After this amplification, electric signal waves from (a) and (c) are inputted to computer 52 to calculates a difference between the both, signal wave L, and in the same way, a difference between signal waves from transistors (b) and (d) is calculated by computer 52' to obtain new signal wave M. Through filter 53, only signal wave M is left as signal wave W, which is compared with the reference signal of a comparator, so that a signal indicating the existence of a crack will be sent out. |
