A method for registration of CAD model to video images with added clutter

摘要

A technique for position-finding on a manufactured device such as an integrated circuit ("IC") or a printed circuit board ("PCB"), relating the observed image to a description such as the CAD database that was used to create the devices. The technique contemplates providing an optical image of the surface of the device, obtained with an imaging device such as a video camera and a microscope, generating a synthetic CAD image from the CAD database, subjecting both images to a filtering operation (Laplacian of Gaussian convolution), binarizing (taking the sign of) the results, and correlating the two filtered and binarized images (referred to as "processed" images) to determine relative alignment. One application of the invention is to allow precision positioning of a positioning head relative to a workpiece such as placing an IC device (12) on a PCB (15). A positioning head (17) to which a camera (22) is mounted is driven to the approximate location of the IC site by a positioning mechanism. The positioning mechannism need not be accurate for large increments of travel, but must be capable of providing small relative displacements with high precision. The camera image of the area near the IC site on the PCB is filtered and binarized, and correlated with a processed CAD image of the region surrounding the IC site. This establishes the actual position of the camera (and therefore the positioning head). The positioning head is then moved by the indicated amount.