Effect of polytetrafluoroethylene (PTFE) phase transition at 19 degrees C on the use of Spectralon as a reference standard for reflectance. / Ball, Christopher P.; Levick, Andrew P.; Woolliams, Emma R.; Green, Paul D.; Dury, Martin R.; Winkler, Rainer; Deadman, Andrew J.; Fox, Nigel P.; King, Martin D.

In: Applied optics, Vol. 52, No. 20, 10.07.2013, p. 4806-4812.

Research output: Contribution to journalArticlepeer-review



  • Appl. Opt. 2013 Ball

    Rights statement: This paper was published in Applied Optics and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/ao/abstract.cfm?uri=ao-52-20-4806. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.

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Sintered polytetrafluoroethylene (PTFE) is highly reflective and is widely used as a reference standard in remote sensing, radiometry, and spectroscopy. The relative change in output flux from a PTFE integrating sphere over the room temperature phase transition at 19°C has been measured at a monochromatic wavelength of 633 nm as 1.82 ± 0.21%. The change in output flux was attributed to a small change of 0.09 ± 0.02% in the total hemispherical reflectance of PTFE, caused by a change in its material density as a result of the phase transition. For the majority of users, this small change measured in total hemi-spherical reflectance is unlikely to impact significantly the accuracy of PTFE flat panel reflectors used as reference standards. However, owing to the multiple reflections that occur inside an integrating sphere cavity, the effect is multiplied and remedial action should be applied, either via a mathematical correction or through temperature stabilization of the integrating sphere when high accuracy (<5%) measurements of flux, irradiance, or radiance are required from PTFE-based integrating spheres at temperatures close to the phase transition at 19°C.
Original languageEnglish
Pages (from-to)4806-4812
Number of pages7
JournalApplied optics
Issue number20
Publication statusPublished - 10 Jul 2013
This open access research output is licenced under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

ID: 17915862