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Method for more accurate transmittance measurements of low-angle scattering samples using an integrating sphere with an entry port beam diffuser |
Applied Optics, Vol. 50, Issue 7, pp. 999-1006 (2011)
http://dx.doi.org/10.1364/AO.50.000999
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Abstract
For most integrating sphere measurements, the difference in light distribution between a specular reference beam and a diffused sample beam can result in significant errors. The problem becomes especially pronounced in integrating spheres that include a port for reflectance or diffuse transmittance measurements. The port is included in many standard spectrophotometers to facilitate a multipurpose instrument, however, absorption around the port edge can result in a detected signal that is too low. The absorption effect is especially apparent for low-angle scattering samples, because a significant portion of the light is scattered directly onto that edge. In this paper, a method for more accurate transmittance measurements of low-angle light-scattering samples is presented. The method uses a standard integrating sphere spectrophotometer, and the problem with increased absorption around the port edge is addressed by introducing a diffuser between the sample and the integrating sphere during both reference and sample scan. This reduces the discrepancy between the two scans and spreads the scattered light over a greater portion of the sphere wall. The problem with multiple reflections between the sample and diffuser is successfully addressed using a correction factor. The method is tested for two patterned glass samples with low-angle scattering and in both cases the transmittance accuracy is significantly improved.
© 2011 Optical Society of America
OCIS Codes
(120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
(120.3150) Instrumentation, measurement, and metrology : Integrating spheres
ToC Category:
Instrumentation, Measurement, and Metrology
History
Original Manuscript: September 27, 2010
Revised Manuscript: January 10, 2011
Manuscript Accepted: January 13, 2011
Published: February 24, 2011
Virtual Issues
Vol. 6, Iss. 4 Virtual Journal for Biomedical Optics
Citation
Annica M. Nilsson, Andreas Jonsson, Jacob C. Jonsson, and Arne Roos, "Method for more accurate transmittance measurements of low-angle scattering samples using an integrating sphere with an entry port beam diffuser," Appl. Opt. 50, 999-1006 (2011)
http://www.opticsinfobase.org/vjbo/abstract.cfm?URI=ao-50-7-999
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