| dc.description.abstract | This thesis work explores the usage of a dual-RGB multispectral imaging setup for enhancing the colour accuracy of photographic films capture. A dual-RGB multispectral imaging system captures two images from a trichromatic camera using two different light sources. The combination of trichromatic camera with two light sources give rise to a six-channels multispectral imaging system. One of the applications for such a system is in cultural heritage for digitally preserving the appearance of artworks. The thesis work is mainly divided into six parts. The first part relates to the characterization of the different components of the imaging pipepline including the camera, LEDs light source, and colour targets transmittances. In the second part, dual-RGB simulations are performed on the 630 different combinations of light source pairs to find an optimal light source pair minimizing the Delta E00 error. The optimal light sources outperformed a simulated three-channel capture in colour accuracy. The third part of the thesis improves the colour accuracy of dual-RGB capture simulations. This is done by applying optimizations on the LEDs intensities. Two optimization methods of Particle Swarm Optimization (PSO) and genetic algorithm are used. Both algorithms are shown to converge on the same solution. The optimized light sources are referred to being part of the dual-RGB-PSO. In the fourth part of the thesis, real capturing sessions are conducted for three-channel, dual-RGB, dual-RGB-PSO optimized light sources. Dual-RGB and dual-RGB-PSO are shown to outperform the colour accuracy measured from three-channel captures. In real captures, both dual-RGB and dual-RGB-PSO performs equally well in contrast to the simulations where dual-RGB-PSO performed better than dual-RGB. The fifth part of the thesis is related to high dynamic range (HDR) imaging in the workflow of dual-RGB. An HDR pipeline is followed for the dual-RGB and dual-RGB-PSO captures. The results show a promising direction that can be undertaken by implementing HDR imaging techniques in dual-RGB context. The sixth part of the thesis relates to the application of the dual-RGB workflow, which was implemented on photographic films, for reflective objects. The LED light source which was originally built only for photographic films, was adapted to be operable for reflective objects with minimal changes and easy to move back and forth between film and reflective capturing mode. The simulations in the reflective mode converged to similar optimal light sources as were obtained for photographic films. Also the light sources optimized for photographic films showed good results for reflective objects. The results hint at the possibility of the development of a combined multispectral imaging setup where both the films and reflective objects can be captured, and possibly, with minimal changes both in the physical setup and light sources. | |
