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A fiber optic array spectrometer with parallel multichannel optical lock-in detection and its application to in situ lighting measurements
  • Christophe Martinsons ,
  • Nicolas Picard ,
  • Samuel Carrell
Christophe Martinsons
Centre Scientifique et Technique du B√Ętiment, Centre Scientifique et Technique du B√Ętiment

Corresponding Author:[email protected]

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Nicolas Picard
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Samuel Carrell
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Abstract

Lock-in detection is a well-established technique to measure a modulated electrical signal in the presence of noise and large background signals. Commercially available lock-in amplifiers are not adapted to detector arrays such as used in modern compact optical spectrometers. In this case, performing lock-in detection requires a parallel multichannel processing of all spectral channels simultaneously. This paper describes an optical lock-in spectrometer featuring parallel and multichannel lock-in detection. It is based on two compact array spectrometers working in phase quadrature thanks to a wideband optical modulator assembled using standard optical components. In the application example, irradiance and illuminance lock-in measurements were performed on commercial LED lamps exhibiting temporal light modulation at different frequencies. A remote sensing optical device was designed to measure from a distance the temporal luminous waveform of a specific LED lamp and send it to the reference input of the optical lock-in spectrometer. When these lamps were operating together on top of a large continuous luminous background up to 30 times more intense, the optical lock-in spectrometer successfully retrieved the respective spectral irradiance distributions and color parameters of each lamp, allowing their characterization to be performed independently of the other light sources illuminating the sensor during the measurements.
01 Jul 2023Published in Journal of Lightwave Technology volume 41 issue 13 on pages 4489-4495. 10.1109/JLT.2023.3244652