File(s) not publicly available

Light-emitting diodes as light sources for spectroscopy: Sensitivity to temperature

journal contribution
posted on 05.06.2018, 00:00 authored by Clinton HayesClinton Hayes, Kerry WalshKerry Walsh, Colin GreensillColin Greensill
© The Author(s) 2017. Understanding of light-emitting diode lamp behaviour is essential to support the use of these devices as illumination sources in near infrared spectroscopy. Spectral variation in light-emitting diode peak output (680, 700, 720, 735, 760, 780, 850, 880 and 940 nm) was assessed over time from power up and with variation in environmental temperature. Initial lightemitting diode power up to full intensity occurred within a measurement cycle (12 ms), then intensity decreased exponentially over approximately 6 min, a result ascribed to an increase in junction temperature as current is passed through the light-emitting diode. Some light-emitting diodes displayed start-up output characteristics on their first use, indicating the need for a short light-emitting diode ‘burn in’ period, which was less than 24 h in all cases. Increasing the ambient temperature produced a logarithmic decrease in overall intensity of the light-emitting diodes and a linear shift to longer wavelength of the peak emission. This behaviour is consistent with the observed decrease in the IAD Index (absorbance difference between 670 nm and 720 nm, A 670 -A 720 ) with increased ambient temperature, as measured by an instrument utilising light-emitting diode illumination (DA Meter). Instruments using light-emitting diodes should be designed to avoid or accommodate the effect of temperature. If accommodating temperature, as light-emitting diode manufacturer specifications are broad, characterisation is recommended.

History

Volume

25

Issue

6

Start Page

416

End Page

422

Number of Pages

7

eISSN

1751-6552

ISSN

0967-0335

Publisher

SAGE Publications

Peer Reviewed

Yes

Open Access

No

Acceptance Date

17/09/2017

Era Eligible

Yes

Journal

Journal of Near Infrared Spectroscopy