Vilaseca Meritxell, Pujol Jaume, Arjona Montserrat, de Lasarte Marta
Center for Sensors, Instruments and Systems Development, Department of Optics and Optometry, Technical University of Catalonia, Terrassa, Spain.
Appl Opt. 2006 Jun 20;45(18):4241-53. doi: 10.1364/ao.45.004241.
We analyze the performance of a multispectral system that works in the near- infrared (NIR) region of the electromagnetic spectrum (NIR: 800-1000 nm). The system, which uses a CCD camera as a sensor with five acquisition channels, is capable of reconstructing the NIR spectral reflectance curves for a wide range of samples with a high degree of accuracy. We carried out a study of the sources of error in the experimental system, developed a luminance adaptation model to remove the dependence of the captured images on the exposure time of the camera and the f-number of the objective lens, and performed reconstructions of the spectral reflectances of a set of 80 samples. We achieved the best results by using a 12-bit camera, considering a different luminance adaptation transform for each channel, and by using the pseudoinverse reconstruction method. Under these conditions, the system provided mean percentages of reconstruction higher than 99.8% and root-mean-square-error values lower than 0.17, and is therefore suitable for use as a spectrophotometric instrument.
