Probing of Two-Dimensional Grid Patterns by Means of Camera-Based Image Processing

Published

March 1, 2000

Author(s)

Martin Schroeck, Theodore D. Doiron

Abstract

Camera based probes and machine vision have found increased use in coordinate measuring machines over the past years and the calibration of artifacts for these probes has become an important task for NIST. Until recently these artifacts have been calibrated using one or two dimensional measuring machines with electro-optic microscopes or scanning devices as probes. These sensors evaluate only a small section of the edge of a grid mark, and irregularities in this particular spot from local deformations or contamination influence the measurement result. Since these measurements result in a single number based on the entire field of view, the influence of small irregularities are not easily detected. Since different probes scan different parts of the grid mark edge they may give systematically different positions of the mark. The conversion to video based sensors has allowed for flexibility in edge detection, although most instruments still use least squares fits as the substitute geometry of straight edges. This method is very susceptible to noise and edge irregularities, We present some experiments for finding the sub-pixel edge point locations and fitting the set of edge points to a line using a fairly simple least sum of absolute deviations fit. Data from a high accuracy 2D measuring machine is used to show the strengths of the algorithms.

Proceedings Title

Proc. SPIE, Machine Vision Applications in Industrial Inspection VIII, Kenneth W. Tobin, Jr., Editor

Volume

3966

Conference Dates

January 24, 2000

Conference Location

San Jose, CA

Conference Title

Image Processing and Metrology

Pub Type

Conferences

Keywords

computer vision, edge detection, grid plates, least sum of absolute deviations, robust algorithm

Citation

Schroeck, M. and Doiron, T. (2000), Probing of Two-Dimensional Grid Patterns by Means of Camera-Based Image Processing, Proc. SPIE, Machine Vision Applications in Industrial Inspection VIII, Kenneth W. Tobin, Jr., Editor, San Jose, CA (Accessed April 20, 2024)