Flat-field calibration method for hyperspectral frame cameras

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Flat-field calibration method for hyperspectral frame cameras. / Kokka, Alexander; Pulli, Tomi; Honkavaara, Eija; Markelin, Lauri; Kärhä, Petri; Ikonen, Erkki.

In: Metrologia, 06.08.2019.

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@article{3f1d80ec96f74bb8b84484228ef77d62,
title = "Flat-field calibration method for hyperspectral frame cameras",
abstract = "This paper presents a method for characterising spatial responsivity of hyperspectral cameras. Knowing the responsivity of the camera as a function of pixel coordinates allows applying a flat-field correction on image data. The method is based on scanning the field of view of the camera with a broadband radiance source, based on an integrating sphere, and combining the captured frames to synthesise a uniform radiance source filling the whole field of view of the camera at the focus distance. The method was compared with a traditional approach where the aperture of an integrating sphere is imaged from a close distance, filling the entire field of view of the camera. The measurement setup was tested with a hyperspectral camera, based on a tunable Fabry–P{\'e}rot interferometer. Without the flat-field correction, the average standard deviation of the pixel responsivities across all the spectral channels of the camera was 3.78{\%}. After the correction, the average standard deviation was reduced to 0.40{\%} and 3.25{\%} for the aperture-scanning method and the close-distance method, respectively. The expanded uncertainty (k  =  2) for the flat-field correction obtained using the scanning method was 0.68{\%}–0.78{\%}, depending on the spectral channel of the camera.",
keywords = "hyperspectral, camera, calibration, flat-fielding, vignetting, Fabry–P{\'e}rot, measurement uncertainty",
author = "Alexander Kokka and Tomi Pulli and Eija Honkavaara and Lauri Markelin and Petri K{\"a}rh{\"a} and Erkki Ikonen",
year = "2019",
month = "8",
day = "6",
doi = "10.1088/1681-7575/ab3261",
language = "English",
journal = "Metrologia",
issn = "0026-1394",

}

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TY - JOUR

T1 - Flat-field calibration method for hyperspectral frame cameras

AU - Kokka, Alexander

AU - Pulli, Tomi

AU - Honkavaara, Eija

AU - Markelin, Lauri

AU - Kärhä, Petri

AU - Ikonen, Erkki

PY - 2019/8/6

Y1 - 2019/8/6

N2 - This paper presents a method for characterising spatial responsivity of hyperspectral cameras. Knowing the responsivity of the camera as a function of pixel coordinates allows applying a flat-field correction on image data. The method is based on scanning the field of view of the camera with a broadband radiance source, based on an integrating sphere, and combining the captured frames to synthesise a uniform radiance source filling the whole field of view of the camera at the focus distance. The method was compared with a traditional approach where the aperture of an integrating sphere is imaged from a close distance, filling the entire field of view of the camera. The measurement setup was tested with a hyperspectral camera, based on a tunable Fabry–Pérot interferometer. Without the flat-field correction, the average standard deviation of the pixel responsivities across all the spectral channels of the camera was 3.78%. After the correction, the average standard deviation was reduced to 0.40% and 3.25% for the aperture-scanning method and the close-distance method, respectively. The expanded uncertainty (k  =  2) for the flat-field correction obtained using the scanning method was 0.68%–0.78%, depending on the spectral channel of the camera.

AB - This paper presents a method for characterising spatial responsivity of hyperspectral cameras. Knowing the responsivity of the camera as a function of pixel coordinates allows applying a flat-field correction on image data. The method is based on scanning the field of view of the camera with a broadband radiance source, based on an integrating sphere, and combining the captured frames to synthesise a uniform radiance source filling the whole field of view of the camera at the focus distance. The method was compared with a traditional approach where the aperture of an integrating sphere is imaged from a close distance, filling the entire field of view of the camera. The measurement setup was tested with a hyperspectral camera, based on a tunable Fabry–Pérot interferometer. Without the flat-field correction, the average standard deviation of the pixel responsivities across all the spectral channels of the camera was 3.78%. After the correction, the average standard deviation was reduced to 0.40% and 3.25% for the aperture-scanning method and the close-distance method, respectively. The expanded uncertainty (k  =  2) for the flat-field correction obtained using the scanning method was 0.68%–0.78%, depending on the spectral channel of the camera.

KW - hyperspectral

KW - camera

KW - calibration

KW - flat-fielding

KW - vignetting

KW - Fabry–Pérot

KW - measurement uncertainty

U2 - 10.1088/1681-7575/ab3261

DO - 10.1088/1681-7575/ab3261

M3 - Article

JO - Metrologia

JF - Metrologia

SN - 0026-1394

M1 - 055001

ER -

ID: 35823220