Extending “color constancy” outside the visible region

Abstract

In this paper, the results of an investigation of the possibility of extending "color constancy" to obtain illuminantinvariant reflectance features from data in the near-ultraviolet (UV) and near-infrared (IR) wavelength regions are reported. These features are obtained by extending a blackbody-model-based color constancy algorithm proposed by Ratnasingam and Collins [J. Opt. Soc. Am. A 27, 286 (2010)] to these additional wavelengths. Ratnasingam and Collins applied the model-based algorithm in the visible region to extract two illuminant-invariant features related to the wavelength-dependent reflectance of a surface from the responses of four sensors. In this paper, this modelbased algorithm is extended to extract two illuminant-invariant reflectance features from the responses of sensors that cover the visible and either the near-UV or near-IR wavelength. In this investigation, test reflectance data sets are generated using the goodness-fitness coefficient (GFC). The appropriateness of the GFC for generating the test data sets is demonstrated by comparing the results obtained with these data with those obtained from data sets generated using the CIELab distance. Results based upon the GFC are then presented that suggest that the modelbased algorithm can extract useful features from data from the visible and near-IR wavelengths. Finally, results are presented that show that, although the spectrum of daylight in the near UV is very different from a blackbody spectrum, the algorithm can be modified to extract useful features from visible and near-UV wavelengths.

Multispectral camera as spatio-spectrophotometer under uncontrolled illumination

“…However, in a real scenario, the spectral power distribution of illumination can differ at various locations in an image. There are various methods for dealing with such situations that address illuminant estimation a per-pixel level [29][30][31]. In our current work, we are demonstrating the multispectral constancy pipeline from image acquisition to the spectral reconstruction.…”