Method for measuring edge profile of an elongated member

Abstract

The present invention is a method of determining edge profile of one or both edges of an elongated member such as a piece of lumber or structural timber. This can be done at high speed as the member is conveyed past a scanning station where it is subject on the conveyor to translational and/or rotational movement relative to a baseline. The baseline is located generally parallel to the longitudinal axis or centerline of the member. At the leading end of the member the instantaneous edge height above the baseline is measured at three spaced apart locations. These measurements are continued along the member with each sampled portion substantially overlapping the previously sampled portion. For each individual sampled portion any deviation from linearity of the edge at the interior measurement position is determined from a chord drawn between the end measurement positions. Knowing these deviations the edge profile can be readily computed for the member. This is most readily done by dividing twice each deviation by the square of the distance between adjacent scanning positions to obtain a second derivative of the edge contour at the measured location. The overall edge contour is then obtained by double integrating the second derivatives obtained over the length of the measured member.