Research On Key Techniques And Applications Of Color Correction For Multi-projector System

With the increasing capabilities of the projectors and the development of computer graphics, projection techniques have been widely used in exhibitions, education, culture, entertainment and military simulation etc. Displays with large scale and super resolution can be constructed by multi-projector system, with the help of computer vision and real-time graphic rendering techniques, various surfaces could be used for projection to provide more vivid and infective visual effect. In recent years, cameras and image-analysis based calibration techniques are getting more and more attentions. Although the geometry deviation can be corrected using such techniques as perspective warping and 3D reconstruction, there are color artifacts caused by brightness differences inside projected image, different projection angle and surface reflectance, existence of the overlap region and inter-reflection. This paper focuses on the color correction of multi-projector systems with different shapes of surfaces and illuminations, which ensures the projected image correspond to the target appearance. The main contributions of this paper are listed in the followings:(1) A method that reconstructs the color model and corrects the color artifacts of multi-projector systems applied on non-textured surface is proposed. In order to remove the color fluctuation of the projected image, the brightness and chrominance properties of the system are thoroughly analyzed and described with parametric models. Brightness smoothen method that achieves perceptual uniformity and chrominance correction method that employs both gamut matching and gamut morphing are proposed to ensure smooth color transition. For the system that contains irregular shaped overlap regions, a threshold and smoothness based constrained optimization is applied to calculate attenuate weight for each pixel so as to ensure the brightness uniformity of the system. Theoretical analysis and experimental results show that, compared with the existing methods that deal with projection displays containing irregular shaped overlap region, the proposed algorithm reduces color deviations by more than 30%, which proves the feasibility of the algorithm on correcting the brightness and chrominance variations of multi-projector system.(2) A method that reconstructs the projector-camera color model and compensate the color distortion of multi-projector systems applied on textured surface is proposed. In order to remove the color distortion caused by the non-uniform reflectance of textured surface, a novel algorithm that estimates the surface reflectance are proposed to compensate the target image in real-time. The cost of rendering and system storage is further reduced by decomposing the system color-mixing properties from reflectance information. Theoretical analysis and experimental results show that, compared with the similar methods, the proposed algorithm increases the lightness range by more than 50% while reducing the system memory cost by 66.7%, which proves the feasibility of the algorithm on compensating the projected images on the textured surface.(3) A method that acquires the light transportations and compensates the color distortion of multi-projector systems on complex environments with global illumination is proposed. In order to acquire the energy distribution of each projector pixel, adaptive segmentation and compress sensing based methods are applied to more efficiently acquire the light transport matrix. Clustering based inversion and decomposition of light transport matrix methods are proposed to ensure the real-time image compensation. Theoretical analysis and experimental results show that the proposed method can eliminate the differences between the projected and target image of the multi-projector systems with complex global illumination.Large scale projection displays and textured surface real-time editing systems are designed based on the above-mentioned studies, projection applications in the large-scale cultural activities have been developed, which proves the feasibility and accuracy of the proposed methods.