Narrow Results

Polychromatic lighting sources that are composed of at least four different colored light-emitting diodes (LEDs) offer versatility in color quality of illumination. In this paper, different methods of assessment of color quality of white light are discussed and a general approach to the solution of the color-mixing problem by means of optimization in respect of several color rendition characteristics is considered. Spectral power distributions of model tetrachromatic solid-state sources obtained by maximizing various figures of merit, such as color rendering index, gamut area index, color quality scale, and indices based on the statistical analysis of the just perceivable chromaticity differences for a large number of test color samples, are demonstrated. A concept tetrachromatic lighting source that can be operated within a dynamical trade-off between two opposing color rendition characteristics, the ability to render colors with high fidelity and the ability to render colors with increased chromatic saturation, is introduced. Such "smart" sources with tailored color quality can meet individual needs and preferences of color vision and find numerous applications in lighting.

In this study, we propose a modified partial differential equation (PDE)-based algorithm for image de-hazing. The algorithm possesses relatively low computational complexity and the core function of the PDE is easily amenable to hardware implementation. New contributions include the optimization and automated processing for dark and hazy images, avoiding manual parameter tuning. Additionally, the regularization parameter is computed adaptively from the binary mask of the input image. This is combined with a gradient-based metric for optimization to automatically determine stopping time of the algorithm for both types of images. The proposed scheme is fast and utilizes spatial or frequency domain filters to achieve illumination and reflectance component estimation without resorting to logarithms. Moreover, there is absence of halos in de-hazed images compared to previous work. Extensive experiments indicate that the proposed approach yields results comparable to or better than several works from the literature.