Focus height repeatability improvement in a machine vision inspection system

摘要

A method improves focus height repeatability in a machine vision inspection system. A region of interest is defined within a field of view imaged by a camera portion, wherein an aligned edge feature in the region of interest may introduce a focus height sensitivity that varies depending on the aligned edge feature offset relative to the image pixels. A first set of focus-determining operations determines a focus height for the region of interest, and comprise at least one of: (a) operations that reduce the sensitivity of the focus height determination to the offset of the aligned edge feature relative to the image pixels; and (b) operations that adjust the offset of the aligned edge feature relative to the image pixels according to a predetermined offset repeatability criteria, such that the image data used in the focus height determination fulfills the offset repeatability criteria.

主权项

1. A method for focus height repeatability improvement in a machine vision inspection system to be utilized for performing measurement operations on a workpiece, the method comprising:
providing a camera portion configured to provide an image of a field of view of the workpiece, the image comprising image pixels; providing a focus-determining video tool that includes elements for defining a region of interest within the field of view imaged by the camera portion, wherein the region of interest may include an aligned edge feature of the workpiece in the region of interest that has an alignment such that it introduces a focus height sensitivity that varies depending on an offset of the aligned edge feature relative to the image pixels; and providing a first set of focus-determining operations that determines a focus height for the region of interest, the first set of focus-determining operations comprising operating the machine vision inspection system to provide a set of focus curve data for the region of interest based on a set of workpiece images acquired at a plurality of Z heights, and further including edge offset desensitization operations comprising at least one of:
(a) operations that reduce the sensitivity of the focus height determination to the offset of the aligned edge feature relative to the image pixels; and(b) operations that adjust the offset of the aligned edge feature relative to the image pixels according to a predetermined offset repeatability criteria.