Abstract
A new spatial filtering method is proposed for a narrow band elimination of spatial frequency spectrum. The spatial filter is an array of solar cells which consists of same sized parallel slits manufactured by lithography technique on a single silicon wafer.
Output signals from each solar cell are electrically weighted through the external do amplifiers to realize the weighting distribution so that the weighting value of the center-cell is equal to the sum of the weighting values of the other cells. This spatial weighting gives a characteristics of a narrow band spectrum elimination.
It is expected to apply this spatial filter to the defect detection of knitted fabrics which originally have a narrow spatial frequency spectrum yielded by the periodic knitting. To examine the effectiveness of this spatial filtering method, the experiments are performed to detect some typical defects occurred in the knitted fabrics. And the designing parameters are discussed for the total number of slits, the pitch and the width of slits to realize the better filtering characteristics matched to the individual defect spectrum.
As the results, it is found out that this narrow band elimination spatial filtering method can be applicable to the on-line defect detection of knitted fabrics, e. g. underwears and stockings.
