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Proceedings Paper

The use of a novel phosphor screen for visualising the infrared beam of a gas detector
Author(s): Robert Withnall; Jack Silver; Nicola Wilstead; Terry G. Ireland; George R. Fern; David Klein; Stephen Bishton; Bob Rhodes
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Paper Abstract

A hand held gas detector is being developed that consists of a laser diode emitting light of wavelength equal to 1651 nm and an extended InGaAs detector. The infrared laser beam is double-passed through a column of air via a folding mirror to a detector. The air column is in contact with the outside atmosphere so that low relative molecular mass hydrocarbon gases, which diffuse into the air column, can be detected by the absorption of some of the infrared light. The absorption at around 1651 nm is due to the overtones of C-H stretching vibrations and the limit of detection of the technique is at the parts per million level. One of the problems of using such a device in the field is that the operator cannot visualise the infrared beam directly. Consequently if the gas detection device fails to give a reading, the operator cannot be sure whether the laser is emitting light and the beam is correctly aligned. The paper describes the use of a novel phosphor screen in order to visualise the beam by converting the infrared radiation into visible light. The properties of a number of phosphors that were developed and tested for the visualisation of the beam will be described. The merits of storage phosphors are compared to those of upconversion phosphors for use at this wavelength, which is longer than wavelengths previously visualised using upconversion phosphors.

Paper Details

Date Published: 3 June 2005
PDF: 12 pages
Proc. SPIE 5826, Opto-Ireland 2005: Optical Sensing and Spectroscopy, (3 June 2005); doi: 10.1117/12.604958
Show Author Affiliations
Robert Withnall, Univ. of Greenwich (United Kingdom)
Jack Silver, Univ. of Greenwich (United Kingdom)
Nicola Wilstead, Univ. of Greenwich (United Kingdom)
Terry G. Ireland, Univ. of Greenwich (United Kingdom)
George R. Fern, Univ. of Greenwich (United Kingdom)
David Klein, Semelab plc (United Kingdom)
Stephen Bishton, Semelab plc (United Kingdom)
Bob Rhodes, Semelab plc (United Kingdom)

Published in SPIE Proceedings Vol. 5826:
Opto-Ireland 2005: Optical Sensing and Spectroscopy
Gerard D. O'Sullivan; Brian D. MacCraith; Hugh James Byrne; Enda McGlynn; Alan G. Ryder, Editor(s)

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