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Proceedings Paper

Flow-induced birefringence: the hidden PSF killer in high performance injection-molded plastic optics
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Paper Abstract

A 7-mm OD, NA = 1 water immersion injection-molded plastic endoscope objective has been fabricated for a laser scanning fiber confocal reflectance microscope (FCRM) system specifically designed for in vivo detection of cervical and oral pre-cancers. Injection-molded optics was selected for the ability to incorporate aspheric surfaces into the optical design and its high volume capabilities. Our goal is high performance disposable endoscope probes. This objective has been built and tested as a stand-alone optical system, a Strehl ratio greater than 0.6 has been obtained. One of the limiting factors of optical performance is believed to be flow-induced birefringence. We have investigated different configurations for birefringence visualization and believe the circular polariscope is most useful for inspection of injection-molded plastic optics. In an effort to decrease birefringence effects, two experiments were conducted. They included: (1) annealing of the optics after fabrication and (2) modifying the injection molding prameters (packing pressures, injection rates, and hold time). While the second technique showed improvement, the annealing process could not improve quality without physically warping the lenses. Therefore, to effectively reduce flow-induced birefringence, molding conditions have to be carefully selected. These parameters are strongly connected to the physical part geometry. Both optical design and fabrication technology have to be considered together to deliver low birefringence while maintaining the required manufacturing tolerances. In this paper we present some of our current results that illustrate how flow-induced birefringence can degrade high performance injection-molded plastic optical systems.

Paper Details

Date Published: 23 February 2006
PDF: 11 pages
Proc. SPIE 6082, Endoscopic Microscopy, 60820E (23 February 2006); doi: 10.1117/12.647274
Show Author Affiliations
Matthew D. Chidley, College of Optical Sciences, The Univ. of Arizona (United States)
Tomasz Tkaczyk, College of Optical Sciences, The Univ. of Arizona (United States)
Robert Kester, College of Optical Sciences, The Univ. of Arizona (United States)
Michael R. Descour, College of Optical Sciences, The Univ. of Arizona (United States)

Published in SPIE Proceedings Vol. 6082:
Endoscopic Microscopy
Guillermo J. Tearney; Thomas D. Wang, Editor(s)

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