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DETECTION OF PINHOLES IN ALMONDS THROUGH X–RAY IMAGING

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Transactions of the ASAE. 44(4): 997–1003. (doi: 10.13031/2013.6232) @2001
Authors:   S. Kim, T. Schatzki
Keywords:   Sorting, X–ray imaging, Insect damage, Almond, Pinhole

Pinhole insect damage in natural almonds (i.e., in nuts with the brown skin intact) is very difficult to detect on line. For quality reasons, methods to detect and remove such damaged nuts are of great importance. In this study, we explored the possibility of using Xray imaging to detect pinhole damage in almonds by insects. Xray film and xray linescanned images of 522 pinholedamaged almonds were obtained. Of these film images, 505 were successfully digitized to 8 bits by use of a film scanner with a 0.173mm detector pitch, and 499 of the 505 were collected by a linescan unit with 0.5mm pitch photodiodes, again at 8 bits. The pinholedamaged region appeared slightly darker than the nondamaged region in Xray negative images. A machinerecognition algorithm was developed to detect these darker regions. The algorithm used firstorder (pixel intensity) and secondorder (intensity change) information to identify the damaged region. To reduce the number of false positive results due to germ regions in highresolution images, germ detection and removal routines were also included. With scanned film images, the algorithm showed approximately an 81% correct recognition ratio with only 1% false positives. With linescanned images, 65% of the pinholes were correctly recognized with less than 12% false positives. The algorithm was very fast and efficient, requiring only minimal computation time. The computation rate, if implemented on line, was estimated to be 66 nuts/s, while the xray line scanner could achieve a scan rate of 24 nuts/s.

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