Measuring shapes of three-dimensional objects by rotary focused-plane sectioning

摘要

We devised a new method of shape-from-focus to model a robotic work space. The focused-plane in the new method of focused-plane sectioning was rotated around the axis located at the front focal point of an imaging lens to be able to scan omni-directionally and obtain panoramic range data on the space where objects were located. The astigmatism of the image-taking lens was a major factor causing systematic errors in detecting the 3-D coordinates of the objects. The measurement errors depended on the direction of the object contours. We devised an effective method of correction, where the coordinates of a contour point were corrected by detecting the edge direction of a contour image and interpolating the line-of-sight range and azimuthal angle of the contour point between the predetermined ranges and azimuthal angles of the horizontal and vertical contour points using the direction of the measured contour. After correction, the lateral position errors were less than 0.17 mm and the range errors were less than 8.6 mm on the contour in a direction of 45° at a distance of 730 mm.