Apparatus and method for measuring three-dimensional shape of wood block

A method for measuring three dimensional shape of a generally cylindrical wood block comprising steps of:

• projecting by a light emitting device a light beam against the wood block supported rotatably at a tentative spin axis thereof in such a way that illuminated lines each extending substantially for entire length of the wood block and parallel to the tentative spin axis of the wood block are formed by the light beam at two different positions on the outer peripheral surface of the wood block;
• photographing by an imaging device having a lens the wood block with the illuminated lines on the outer peripheral surface thereof at a plurality of angular positions of the wood block while the wood block is rotated on the tentative spin axis, thereby providing a plurality of photographed block images;
• previously storing data representing the position of the light emitting device and the imaging device relative to the tentative spin axis of the wood block;
• recognizing image of each illuminated line in each of the photographed block images and determining by computation the position of each illuminated line image at a plurality of spaced points thereof;
• determining by computation distances between the tentative spin axis of the wood block and each illuminated line on the outer peripheral surface of the wood block at a plurality of cross-sections of the wood block perpendicular to the tentative spin axis, spaced at a predetermined interval along the tentative spin axis and corresponding to said plurality of spaced points, based on data of said illuminated line image position;
• determining by computation profiles of the wood block at said plurality of cross-sections based on data of said distances;
• said projecting a light beam is done by a pair of lasers disposed symmetrically with respect to an imaginary plane passing through the center of the lens of the imaging device and the tentative spin axis in longitudinal direction of the wood block as viewed from one end of the wood block, each of said lasers being spaced at a predetermined angle from said imaginary plane;
• said photographing is done in such a way that a part on the outer peripheral surface of the wood block photographed by the imaging device at an angular position of the wood block as the illuminated line image due to the illuminated line formed by one laser is photographed by the imaging device again at a different angular position of the wood block as the illuminated line image due to the illuminated line formed by the other laser;
• a step of dividing half-and-half each photographed block image into a first image region and a second image region along an imaginary line in the block image that corresponds to the tentative spin axis of the block;
• and
• a step of combining the first image region of a first block image photographed at a first angular position of the block and the second image region of a second block image photographed at a second angular position of the wood block where the block is rotated from the first angular position for an angle corresponding to twice as big as a predetermined angle, wherein one of the first image region of the first block image and the second image region of the second block image is inverted in line symmetry with respect to said imaginary line.