ROBUST AVERAGING OF SIGNALS FOR TRIANGULATION SENSORS

Optical sensors are increasingly being employed for quality assurance tasks. Such tasks require metrologically safe tools, which means that the measuring uncertainty of the employed sensors has to be quantified , compared and minimized. The measuring uncertainties of optical trian gulation sensors have been found to increase up to a factor of ten, if typical industrially used surfaces, such as steel, are probed under u nfortunate angles. This paper proposes three techniques for reducing e rrors incurred in measurements of triangulation sensors when the surfa ce of the specimen is not perpendicular to the incident light beam, an d when the characteristics of the specimen surface vary. The relative merits of the three techniques are discussed, enabling choices to be m ade in respect of sensor cost, size of error reduction and speed of op eration. The third and most robust technique involves several detector s viewing from different directions in combination with the use of pri ncipal component analysis. Principal component analysis is a statistic al method to obtain a robust average of all signals of the several det ectors.