System for positioning a body

摘要

A system for positioning a body having two opposed edges and having a first axis oriented to pass through the two edges. A beam of light oriented along a second axis orthogonal to the first axis images one or both of the edges onto all or a portion of a photodetector array which is aligned in a direction parallel to the first axis. The array is scanned to obtain a light intensity transition profile of all or part of the projected image whereby the profile has either one or two 50% intensity points. The body is then shifted until both of the 50% intensity points strike predetermined locations on the array indicating that both the edges are included in the image. The body is shifted along the first axis until the fifty percent (50%) intensity point along the transition profile strikes a predetermined location along the photodetector array. The body is also moved along the second axis until the slope of the intensity transition profile is maximized, thereby obtaining an in-focus position. The body is then translated along a third axis, substantially orthogonal to the first and the second axes, until the minimum in the intensity transition profile drops to a predetermined percent of the full intensity value.