An apparatus and method for detecting twist in an articles such as pieces
of lumber being carried on a high-speed longitudinally moving conveyer use
a non-contact scanning technique according to which a pair of transverse
scan line beams is directed onto a surface of the article in spaced
relationship in the conveying direction, and successive scans of
corresponding simultaneously scanned pairs of spaced transverse areas on
the article are repeatedly performed while the article is conveyed, to
generate profile data characterizing position of each transverse area in a
reference system. The profile data characterizing the respective position
of both transverse areas is compared with one another to generate partial
twist indicative data associated with each scan, followed by a summation
of the partial twist indicative data associated with all scans to obtain
an indication of the twist in the considered portion of the article.
