US 4,523,850 A · System for positioning a body

Abstract

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.

Claims17

Dependent claims

A method of positioning a body having two opposed edges and having a first axis oriented to pass through said edges, comprising the steps of:

exposing said body to a beam of light oriented along a second axis substantially orthogonal to said first axis in a direction such that one or both of said edges are imaged by an optical system for projecting a linear section across said body as a silhouette-like image onto all or a portion of a linear array of photodetectors disposed along a direction substantially parallel to said first axis,
scanning said photodetector array to obtain a light intensity transition profile of all or part of said projected image along said photodetector array, said profile having one or two fifty percent (50%) intensity points,
shifting said body along said first axis until both of the fifty percent (50%) intensity points along said transition profile strike predetermined locations along said photodetector array, said profile being indicated by a projected image comprising both of said edges,
moving said body along said second axis until the slope of said intensity transition profile is maximized, thereby obtaining an in-focus position, and
translating said body along a third axis, substantially orthogonal to said first and said second axes, until the minimum in said intensity transition profile drops to a predetermined percent of the full intensity value.

2 more elements

An apparatus for positioning a body having two opposed edges and having a first axis oriented to pass through said edges, comprising:

a light source positioned to expose said body to a beam of light oriented along a second axis substantially orthogonal to said first axis in a direction such that one or both of said edges are imaged by an optical system,
a linear array of photodetectors disposed along a direction substantially parallel to said first axis in a position such that a linear section across said body is projected by said optical system, as a silhouette-like image, onto all or a portion of said photodetector array,
means for scanning said photodetector array to obtain a light intensity transition profile of said projected image along said photodetector array, said profile having one or two fifty percent (50%) intensity points,
means for shifting said body along said first axis to allow both of the fifty percent (50%) intensity points along said transition profile to strike predetermined locations along said photodetector array,
means for moving said body along said second axis to allow the slope of said intensity transition profile to be maximized, thereby obtaining an in-focus position, and
means for translating said body along a third axis, substantially orthogonal to said first and said second axes, to allow the minimum in said intensity transition profile to drop to a predetermined percent of the full intensity value.

3 more elements

Dependencies are inferred from the claim text.

System for positioning a body

Life of this patent

System for positioning a body

Life of this patent

Abstract

Claims17