Showing papers on "Perspective (geometry) published in 1992"

Stereo from uncalibrated cameras

Abstract: The problem of computing placement of points in 3-D space, given two uncalibrated perspective views, is considered. The main theorem shows that the placement of the points is determined only up to an arbitrary projective transformation of 3-space. Given additional ground control points, however, the location of the points and the camera parameters may be determined. The method is linear and noniterative, whereas previously known methods for solving the camera calibration and placement problem to take proper account of both ground-control points and image correspondences are unsatisfactory in requiring either iterative methods or model restrictions. As a result of the main theorem, it is possible to determine projective invariants of 3-D geometric configurations from two perspective views. >

External lead shape measurement apparatus for measuring lead shape of semiconductor package by using stereoscopic vision

Abstract: A lead shape measurement apparatus includes a first perspective imaging device for photographing external leads to be measured, from an oblique direction; a second perspective imaging device for photograping external leads to be measured, from an oblique direction different from that of the first perspective imaging device and so as to include a same photographic field of vision as the first perspective device; a first measurement point determination element for determining a center point of two intersecting virtual straight lines which intersect two ridges of the external leads to be measured in an image plane by photography of the first perspective imaging device; a second measurement point determination element for setting epipolar line in the image plane by the second perspective imaging device on the basis of sight lines when a measurement sampling point of the first perspective imaging device is photographed, and for determining a center point of two intersecting virtual straight lines which intersect two ridges of the external leads to be measured in an image plane and which exists upon the epipolar line; and a coordinate obtaining element for obtaining each of a plurality of the measurement sampling points which are set for measuring a three-dimensional shape of the external leads.

Detection of vertical lines and circles in 3D space using Hough transform techniques

Abstract: Curve detection is an important topic in computer vision. Amongst the many algorithms for curve detection, methods based on Hough transform (HT) techniques have been found to be very effective. The paper developes two specific HT techniques to detect straight lines vertical to the X-Y plane and circles parallel to the X-Y plane in the 3D space from a single perspective image. The projection of vertical lines remains straight lines in the image, but circles become ellipses when the image plane is assumed to be at an angle ( >