Testbed Design for Investigating the Irradiance and Intensity Uniformity Performance of Lightpipes

Abstract

The following describes the design for a low cost optical testbed tailored to measure the irradiance and radiant intensity uniformity of the light field output from a lightpipe. The testbed has been designed to be flexible from a mechanical standpoint to accommodate straight and tapered lightpipes with a varying number of sides and lengths, so that it can serve as a general test setup for various lightpipes which need to be validated and inspected for their output irradiance and radiant intensity uniformity performance. Key application spaces where uniformity of the irradiance and radiant intensity of the lightpipes output are critical, are flow cytometry and digital light projectors, are discussed. The ideal resolution required of the testbed is derived based on the functional requirements for the key applications. It is necessary to determine the level of accuracy needed in the testbed to ensure performance of the flow cytometer or digital light projector are not limited by the performance of the lightpipe. Two system architecture options are proposed, with low cost versions of each built and tested. Experimental data is collected with both systems and a common standard is used to compare the two and select the best option for a low cost system. The selected system is then put through additional experimental testing to explore its utility in comparing the measured performance of two well understood lightpipe designs, which are the square tapered lightpipe and the hexagonal lightpipe. All of these results are then discussed, and future improvements considered.