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Perhaps the most significant factor impacting the accuracy of software for the design of automobile illumination optics is the proper characterization of the light source. Techniques used in the past have employed a simplified geometry to model the emitting element of the lamp along with an intensity distribution which had been measured at some fixed distance. This produced major inaccuracies in the prediction of the optical performance of complicated systems. The authors have been active for several years in developing improved techniques for lamp characterization. It is the intent of this paper to describe the aspects of lamp modeling which we have found to be important. These factors include the use of “far-field” and “near-field” photometry, the spatial variation of luminance over the lamp, and re-emission of radiation incident on the lamp. The most difficult light sources to model accurately are high intensity discharge sources.

Extensive analysis has been performed to determine whether photometric measurements performed using a digital CCD camera system can provide accurate and reliable data for automotive lighting devices. Numerous factors must be examined and understood. Providing the proper equipment is selected and all calibration details are incorporated, the collected data are shown to provide a near-perfect match to goniometer data for the lighting devices which have been studied. This leads to a significant opportunity to provide near-instantaneous testing for collection of isocandela data.

There is a need for more extensive photometric data than simply SAE test points. Full isocandela diagrams and other data are needed if advanced design of lighting devices is to be performed. With the development of scientific-based CCD camera photometers, rapid and accurate measurement of such becomes possible. With proper calibration and computer linking, a powerful new tool is provided. This paper describes techniques which give NIST-traceable near-instantaneous photometry for use in the laboratory and factory.