| 摘要 |
PURPOSE:To detect a live knot having characteristics of the asymmetric distribution of light reflecting intensity by imbalance at a photodetecting level of two photodetecting devices, by providing a means for irradiating scanning beam light and two photodetecting devices. CONSTITUTION:A polygon mirror 14 is rotated in an arrow mark B direction and laser light from a laser light emitting device (a light pojecting device emitting white light may be used) 13 is reflected by the mirror 14. Then, its reflected light is reflected by an FQ mirror 6 and scanning laser beam light is irradiated from the normal line direction to the surface of a blank single plate moving to an arrow mark A direction. The light reflected on the surface of the single plate 1 is received by photodetectors 3, 2 arranged symmetrically to an irradiating part to obtain each signal X1, X2 by amplifying each signal by amplifiers 7, 8. These signals X1, X2 are added by an adder 9 and also, subtracted by a subtracter 10 and the subtracted value X1-X2 is divided by the added value X1+ X2 with a divider 1 to calculate the absolute value of the divided value by an absolute value circuit 12. |
