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Digital Still Color Cameras sample the color spectrum using a monolithic array of color filters overlaid on a charge coupled device array such that each pixel samples only one color band. The resulting mosaic of color samples is processed to produce a high resolution color image such that the values of the color bands not sampled at a certain location are estimated from its neighbors. This process is often referred to as demosaicking. This paper introduces and compares a few commonly used demosaicking methods using error metrics like mean squared error in the RGB color space and perceived error in the CIELAB color space. 2002 SPIE and IS&T. [DOI: 10.1117/1.1484495]

In this paper, we extend the idea of using mosaicked color filter array (CFA) in color imaging, which has been widely adopted in the digital color camera industry, to the use of multispectral filter array (MSFA) in multispectral imaging. The filter array technique can help reduce the cost, achieve exact registration, and improve the robustness of the imaging system. However, the extension from CFA to MSFA is not straightforward. First, most CFAs only deal with a few bands (3 or 4) within the narrow visual spectral region, while the design of MSFA needs to handle the arrangement of multiple bands (more than 3) across a much wider spectral range. Second, most existing CFA demosaicking algorithms assume the fixed Bayer CFA and are confined to properties only existed in the color domain. Therefore, they cannot be directly applied to multispectral demosaicking. The main challenges faced in multispectral demosaicking is how to design a generic algorithm that can handle the more diversified MSFA patterns, and how to improve performance with a coarser spatial resolution and a less degree of spectral correlation. In this paper, we present a binary tree based generic demosaicking method. Two metrics are used to evaluate the generic algorithm, including the root mean-square error (RMSE) for reconstruction performance and the classification accuracy for target discrimination performance. Experimental results show that the demosaicked images present low RMSE (less than 7) and comparable classification performance as original images. These results support that MSFA technique can be applied to multispectral imaging with unique advantages.

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It has long been known that color experiences under con-

The technique of multispectral filter array (MSFA) is a multispectral extension of the widely deployed color filter array (CFA), which uses single chip sensors and subsequent interpolation strategies to produce full color images. However, multispectral demosaicking presents unique challenges to traditional CFA demosaicking algorithms which cannot be directly extended to deal with various filter arrays with different numbers of spectral bands or different spatial patterns within each band. In addition, the more spectral bands involved, the more sparse each band samples the image plane, and the less information we can utilize when performing the interpolation. In this paper, we study a generic MSFA demosaicking method, which follows a binary tree structure to determine the order according to which different spectral bands and different pixel locations within each band are progressively interpolated, making the edge information utilized more effectively. The proposed method is demonstrated to outperform three traditional interpolation techniques as well as three advanced CFA demosaicking methods using two performance measures, the root mean square error (RMSE) for reconstruction fidelity and the classification accuracy for target recognition performance.

Observer metamerism has long been known to be an issue of concern for color engineers. With the advent and mass proliferation of narrow-band display devices, this article addresses the issue of observer metamerism and puts it in the context of first understanding the implication of interobserver variations in the color matching functions (CMFs) and additionally designing the ideal set of primary illuminant spectral power distributions (SPDs) such that observer metamerism is minimized. The article also suggests the use of the Full Width Half Maximum (FWHM) and the number of modes (peaks) in the primary SPDs as a means of assessing the susceptibility to observer-to-observer variations between various modern display technologies.

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