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Proceedings Paper

Image processing automatic interferometric calibration system for line scales
Author(s): Hector Gonzalez; Carlos Galvan; J. Antonio Muñoz
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Paper Abstract

An automatic calibration bench to calibrate line scales up to three meters has been developed at the Centro Nacional de Metrologia. It incorporates an heterodyne laser interferometer to follow the position of a carriage that support a microscope with a CCD camera. The images are processed using a novel robust algorithm to determine the center of each line. The carriage travels along guide ways and is commanded by a computer that controls the servomotor that moves it, allowing to complete the calibration automatically. The measurement and control software developed uses an image processing algorithm based on Gabor filters and robust statistics to discriminate between lines and unwanted features that may exist such as stain, scratches, rust, etc. It then calculates the absolute position of each line by coupling the reading of the carriage position given by the interferometer and the centerline position of the line in the image. Additionally, the software corrects the laser readings for ambient condition variations and controls the progress of the carriage. The mechanical design consists of a stiff bench with guide ways on which the carriage travels. Although the carriage travels in non-kinematic guide ways, the microscope and CCD camera sit on a plate that is kinematically supported. The movement is provided by a servomotor and transmitted by means of a screw. Uncertainty is expected to be between 3 and 10 um which is common to other similar systems. The gross advantage is the ability to calibrate automatically and discriminate defects on the scale.

Paper Details

Date Published: 20 November 2003
PDF: 10 pages
Proc. SPIE 5190, Recent Developments in Traceable Dimensional Measurements II, (20 November 2003); doi: 10.1117/12.503865
Show Author Affiliations
Hector Gonzalez, Ctr. Nacional de Metrología (Mexico)
Carlos Galvan, Ctr. Nacional de Metrología (Mexico)
J. Antonio Muñoz, Ctr. de Investigacion en Matematicas (Mexico)


Published in SPIE Proceedings Vol. 5190:
Recent Developments in Traceable Dimensional Measurements II
Jennifer E. Decker; Nicholas Brown, Editor(s)

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