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1 November 1991 Testing binary optics: accurate high-precision efficiency measurements of microlens arrays in the visible
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A goal of our work with binary optics is to identify the underlying efficiency limits of the technology. To aid in our understanding, we have designed a mask set that incorporates ten different 200-micrometers square lenslet designs with speeds ranging from f/0.8 to f/61 as single elements and as 10 X 10 arrays. The f/6 lenslet of the set is also used in 3.2 cm diameter arrays for an afocal imaging relay application. To measure efficiency reliably, we have developed a dedicated apparatus: the `EtaMeter.'' Based on a dual-beam, single- detector, self-referencing approach, the system offers low-noise performance, long-term stability, and excellent repeatability. EtaMeter measures relative efficiency with 0.001 precision and, when calibrated, gives absolute efficiency measurements accurate to 0.005. We have measured the optical efficiency of several devices and compared the results to benchmark calculations, concentrating on the effects of layer-to-layer alignment accuracy for 8-phase-level devices. For an f/4.5 microlens we find a distortion-induced excess loss of about 1.5/0.1 micrometers misregistration. For an f/4.5 microlens with overlay registration better than 100 nm, we achieve an absolute efficiency of 0.85, corresponding to 96 of the prediction.
© (1991) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Michael Holz, Margaret B. Stern, Shirley Medeiros, and Robert E. Knowlden "Testing binary optics: accurate high-precision efficiency measurements of microlens arrays in the visible", Proc. SPIE 1544, Miniature and Micro-Optics: Fabrication and System Applications, (1 November 1991);


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