Abstract: tric accuracy is a measure of how well a detector signal voltage represents the surface reflectance at the corresponding object region for a specific illumination condition. A linear relationship should exist between the signal voltage and the product of the object reflectance and source irradiance at a point of interest. Furthermore, the measured voltage should represent only the point of interest with negligible contribution from surrounding points. This paper describes the class of machine vision applications for which photometric accuracy is important which includes color and height measurement. Recognizing that a monochrome or color CCD array is the usual choice of image sensor, error sources are reviewed. One error which has not received much attention which can severely degrade performance is CCD veiling glare. Experimental results are shown which quantify this error and an empirical model developed to represent the degradation of photometric measurement performance.!4
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