N 
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inlet on the 
nted facing 
g a pair of 
of 405nm, 
t and were 
the object, 
the cotton, 
ight source 
id balanced 
cheme of 
2. 
CCD camera 
ay 
;ystem 
of foreign 
/ely visible 
wavelength 
length, 
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have. Then, 
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: for bristle 
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i feature of 
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of the two 
lal contrast 
image than 
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ble region, 
ir detecting 
i cotton. 
(c) 850nm wavelength image (d) fused image of two wavelengths 
Fig.3 comparison of images of different band: (a) visible region image, (b) 405nm wavelength image, (c) 850nm wavelength 
image, (d) fused image of two wavelengths. 
Thus, the combination of the 405nm and 850nm wavelengths 
enabled the differentiation of foreign fibers from cotton. And 
best visual contrast between foreign fibers and cotton was show 
in the fused image of the two wavelengths, so the image fusion 
method using multiwavelength imaging showed the best 
potential of discriminating a wide range of foreign fibers from 
cotton. 
For quantitatively evaluation the performance of image fusion 
method, the average gray level difference between cotton and