Measuring Absolute Radiance by Calibrating a Hyperspectral Camera Economically

ABSTRACT Hyperspectral imaging has become popular for a vast number of applications. It allows the analysis of the spectral radiometric, photometric, and colorimetric properties of images on a pixel‐by‐pixel level. To measure the pixel‐level absolute spectral radiance of images, researchers have proposed several absolute radiometric calibration methods of hyperspectral cameras, but these methods are challenging to apply. This paper demonstrates a method to characterize and calibrate an economical commercial hyperspectral camera (Specim IQ) using affordable instruments: a factory‐calibrated spectroradiometer, a Helium lamp, and a stable broadband light source. The dark signal is stable and uniform; no flat‐field correction is needed if a 2% error can be tolerated. However, a 1.88 nm wavelength correction must be applied. Through this method, the camera, which is designed to measure spectral reflectance, can be used to measure the absolute spectral radiance of a scene by a simple equation. The calibration result was validated by comparing the reconstructed spectra of an OLED panel and a Macbeth ColorChecker with the spectroradiometer. The camera can achieve an average accuracy of about 4% in radiance, 4% in luminance, Δ u′ , v′ 0.005 in chromaticity, and a total color difference of 2.5 Δ E * ab . This performance is comparable with a factory‐calibrated colorimetric camera. The paper demonstrates that hyperspectral imaging can be done with reasonable accuracy and affordability, and it can be a powerful tool in lighting and visual perception research.