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Proceedings Paper

Testing binary optics: accurate high-precision efficiency measurements of microlens arrays in the visible
Author(s): Michael Holz; Margaret B. Stern; Shirley Medeiros; Robert E. Knowlden
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Paper Abstract

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.

Paper Details

Date Published: 1 November 1991
PDF: 15 pages
Proc. SPIE 1544, Miniature and Micro-Optics: Fabrication and System Applications, (1 November 1991); doi: 10.1117/12.49375
Show Author Affiliations
Michael Holz, Lincoln Lab./MIT (United States)
Margaret B. Stern, Lincoln Lab./MIT (United States)
Shirley Medeiros, Lincoln Lab./MIT (United States)
Robert E. Knowlden, Lincoln Lab./MIT (United States)

Published in SPIE Proceedings Vol. 1544:
Miniature and Micro-Optics: Fabrication and System Applications
Chandrasekhar Roychoudhuri; Wilfrid B. Veldkamp, Editor(s)

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