We present the architecture of a six band high-definition television (HDTV) camera system newly developed for accurate color reproduction of motion pictures based on spectral information. The camera has an optical component connecting the objective lens to two conventional HDTV camera heads whose spectral sensitivities are individually adjusted by placing different interference filters between the objective lens and each camera. Evaluation of the accuracy of the color estimation obtained using the six band camera and a conventional RGB, i.e., three band, HDTV camera using simulated and experimentally obtained camera signals showed that the six band camera achieves accurate color estimation. In the experimental evaluation, the average color differences for the 24 color patches of the GretagMacbeth Color Checker for the six band and RGB camera signals were 1.43 and 4.12 delta-E_ab. This system should thus be suitable for a wide variety of applications.

Theoretically, there can be a compromise between color and spatial image quality for multispectral imaging: Increasing the number of channels increases spectral and colorimetric accuracy, that is, color quality increases; decreasing the number of channels reduces image noise and other spatial artifacts, that is, spatial image quality increases. Two paired comparison psychophysical experiments were performed to scale color and spatial image quality in order to better understand this compromise. Test targets, a watercolor painting, and several dioramas were imaged using three-, six-, and 31-channel image acquisition systems. One of the three-channel systems was a professional grade trichromatic digital camera; the other systems used the identical research grade sensor. For the six- and 31-channel images, both direct pseudoinverse based transformations and the use of principal component analysis were used to convert from digital to spectral data. The spectral data were used to render colorimetric images. Pseudoinverse transformations were used to convert the three-channel images to colorimetry. Twenty-seven observers judged, successively, color and spatial image quality of colorimetric images rendered for an LCD display compared with objects viewed in a light booth.The targets were evaluated under simulated daylight (6800K) and incandescent (2700K) illumination and the visual data were transformed to quality scales using Thurstone's law of comparative judgments, Case V. The first experiment evaluated color image quality. Under simulated daylight, the subjects judged all of the images to have the same color accuracy, except the professional camera image that was significantly worse. Under incandescent illumination, all the images, including the professional camera, had equivalent performance. The second experiment evaluated spatial image quality. The results of this experiment were highly target dependent. A subsequent image registration experiment showed that the results of the spatial image quality experiment were affected by image registration to some degree. For both experiments, there was high observer uncertainty and poor data normality. Dual scaling and a graphical analysis of observer response data were used as alternate techniques to Thurstone's Law. These techniques yielded similar results to the Thurstone-based quality scales. The uncertainty was caused by insufficient ambiguity between images. A simultaneous analysis of the color and spatial image quality results for the research grade sensor indicated that the most preferred image types were the 31-channel images. Thus, it is possible for multispectral images with many channels to achieve similar color and spatial image quality to systems with just a few channels.The theoretical compromise between color and spatial image quality as the number of channels increased was not observed under these experimental conditions.

The quality of a multispectral color image acquisition system depends on many factors, the spectral sensitivity of the different channels being one of them. In a relatively common setup, a multispectral camera is being implemented by coupling a monochrome digital camera with a set of optical filters, typically mounted on a filter wheel. The properties of these filters is an important component of the system design. Different methods have been proposed for the design or selection of appropriate filters. In this article we review several methods used for selection of an optimal subset of filters from a set of available filters. The different filter selection methods are subjected to a comprehensive evaluation procedure, in which their quality is evaluated mainly in terms of the ability of the resulting system to reconstruct scene spectral reflectances.

In this study we analyze the influence of the illuminant on the reconstruction of spectral reflectance curves in the near infrared region of the spectrum. We have tested several methods based on multispectral imaging that permit us to obtain the spectral reflectance of samples from measurements performed with a CCD camera. Using numerical simulation, we have analyzed the number and shape of the optimum filters that need to be used in the acquisition channels in order to obtain good spectral reconstructions under a great number of different lighting conditions. Finally, we have studied the influence of the illuminant on the quality of the reconstruction using a set of commercially available filters which are similar to the optimum filters obtained from the simulations. Our results show that the reconstruction does not depend strongly on the illuminant used. This indicates that with the same set of filters we can obtain good reconstructions for different types of illuminant.

We propose a simple but useful method to represent multispectral images captured by multispectral cameras (MSC) with different numbers of bands. When considering accurate color reproduction under an arbitrary illuminant, it is necessary to represent them in a common space with sufficient accuracy of spectral information, estimated from each multispectral image. The principal component analysis (PCA) is useful to reduce the high dimension of the spectral information. However, PCA-based methods may cause both large differences in dynamic range between coefficients of the basis functions derived from the PCA and negative pixel values, therefore, it is not easy to handle or edit coefficient images. To solve the problem, we propose the idea of a virtual multispectral camera (VMSC) that transforms real multispectral images into virtual multispectral images. We design the sensitivities of the VMSC properly, and our unified representation can avoid some disadvantages of conventional PCA-based methods. We experimentally demonstrate the color reproduction accuracy of our method by comparing it with the PCA-based methods, and we show an example of a virtual multispectral image transformed by our method.

Multispectral imaging will certainly provide an excellent solution to color problems in medicine, and may have significant impacts in many aspects of medicine, so that the realization of individual improvement forms a complicated network. Specific reports on the concrete medical problems that will be solved by a specific multispectral technology will therefore be indispensable. It is also important to understand some specific principles are appropriate from a marketing viewpoint for the chaotic medical field. Based on these considerations, two promising medical applications of multispectral imaging are proposed; digital images with spectral reflectance for each pixel, and digital images that are very accurate reproductions of real objects. The first technology will lead to new morphological diagnostic methods more powerful than human visual perception alone, and possibly even to the discovery of the mechanism of human color recognition, while the second advance will lead to a major improvement in the diagnostic reliability of digital color images and wider medical adoption of digital technology. The former will require considerable investment but will provide significant improvements in diagnostic ability, particularly for rare diseases, while the latter will provide practical and general improvements in medicine at relatively low cost.

For analyzing color reproduction of an ink jet printer, it is important to fully understand the relationship between amounts of dye placed on the paper and resultant colors. This insight will enable one to develop a simulation that can be used to design optimum subtractive color dyes. The purpose of the present study is to verify the predicting models that can predict tristimulus values from printed dye amounts, for use in evaluating the performance of dye-based ink jet printers (IJs). In the present study, five predicting models were compared for dye-based IJ, including the Neugebauer model, the Yule-Nielsen Neugebauer model, the Kubelka-Munk model, the Cellular Neugebauer model, and the Cellular Kubelka-Munk model. Further, the comparison between a dye-based IJ and photographic color paper was studied by means of a computer simulation. This investigation was carried out from the viewpoints of the stability of selective grays for illumination metamerism and of maximizing color gamut volumes. For a dye-base IJ, the effect of ink dilution was also studied. This study is an important step toward the development of simulations for use in improving image quality for dye-based IJ.

In order to produce color ink jet prints with good fastness properties, the use of special, coated papers is generally essential. The use of modified conventional coating pigments has been suggested as a means to obtain a matte ink jet coating that would combine the good properties of silica-based ink jet coatings and conventional printing papers. This study examined the water fastness of ink jet prints using experimental coated papers containing modified PCC and kaolin pigments, and model inks with known compositions. The properties of the coatings were altered by using different ratios of coating pigments, and types of binder and dispersant. The water fastness of the prints was analyzed using conventional methods for measuring paper properties and print quality, combined with FTIR and Raman spectroscopy and multivariate data analysis methods. The results indicated that within the studied sample sets, primarily the chemical paper–ink interactions contributed to water fastness on cationic PVA-poly-DADMAC coatings, whereas on weakly cationic styrene-acrylate latex-starch coatings, structural paper properties were relevant as well. In general, increased impermeability of the coating appeared to be advantageous. With regard to the chemical paper–ink interactions, ionic bonding between the dye and the coating proved to be beneficial for water fastness, provided that the interacting coating component was insoluble to water.