羽石 秀昭

We have developed the multiband color imaging systems in the frame work of the IPA project as New Color Management System Based on Human Perception. This system consisted of multiband CCD camera, computer, CRT and projection type monitor. Five band images were taken by CCD camera with 2048x2048 pixels. Reflectance spectra of the object were estimated by the principal component analysis and Wiener estimation method. Spectral transmittance of separation filter was optimized by simulated annealing method based on Wiener estimation. Color adaptation model was introduced for accurate color reproduction of paintings based on human perception. In this paper, estimation of spectral reflectance of paintings, developed multiband camera, various software for image composition and control of multiband camera are introduced and demonstrated.

We are developing a spectral characteristics database for evaluating color reproduction in image input devices. The database is designed so that spectral characteristics are systematically divided by category, according to the purpose to which they are to be applied and every category has a sufficient variety of samples. The categories are as follows: photographic materials, graphic color printing, computer color printers output, paints, flowers, leaves, human skin colors and historical Krinov data. The total number of colors is 49, 672. The database is being proposed to be published as Japanese / International standard technical reports for use in establishing a new color reproduction evaluation method.

The design of spectral characteristic of the light source in an optical endoscope is discussed. First, two criteria are introduced for the evaluation of the Light source and the evaluation result for two CIE standard illuminants and 15 light sources commercially available is presented. Next, an optimization method using POCS (projection onto convex set) is proposed for the design of the light source. It is shown that the optimum right source achieves much better score for the introduced criteria than the 17 light sources. Simulation of image reproduction of mucous membrane under an arbitrary light source is also described.

In this paper, a color difference is defined instead of the conventional color differences to evaluate gamut-mapping techniques for electronic endoscope images reproduced on CRT under environmental illuminant. This color difference is defined from Mahalanobis distance by using covariance matrices for differences of metric lightness, chroma and hue single. The covariance matrices for endoscope images were obtained by psychophysical experiments. We compared the resultant matrices with those for natural scenes, and found the color difference was customized for the electronic endoscope images well.

A new color management system has been developed for high definition color recording and reproduction of art paintings. This system is consisted of high accurate multi-band camera, personal computer and projected type display. The multi-band camera is composed by five band filters and single chip CCD camera with 2048x2048 pixels. The reflectance spectra of each pixel of the object were estimated by using five band images within less than the average color difference Delta E*ab = 1.16. The spectral transmittance of five filters was determined by simulated annealing method and principal component analysis of spectral reflectance of paintings. Images of art paintings were reproduced onto the projection type monitor under the consideration of color appearance. In this paper, we describe methods to estimate of reflectance spectra of paintings from five band images, optimization of spectral transmittance of filters and color reproduction of paintings based on the color appearance models.

In this paper, we propose a technique to design mosaic color filters on single-chip CCD of electronic endoscope to improve the color reproduction. In a previous paper, we have reported a color reproduction method based on the estimation of reflectance spectra. The reflectance spectra were estimated using R, G, B values and three basis functions. The R, G, B values were obtained using the rotating color wheel composed of R, G, B filters. On the other hand, the images obtained from single-chip CCD with color filter array have an interpolation error. They cause the degradation of spatial information in the estimated RGB image. In this research, we calculated spatial frequency distribution of the reflectance spectra in each optical wavelength, then we found that it has marked characteristic. In optimizing the spectral transmittance of the color filters, this characteristic and the interpolation error are used in the cost function of the nonlinear optimization technique.

Design of color filters used in multiband image acquisition system is discussed for digital archiving of artworks. Reflectance spectra of color samples for painting were first measured and analyzed using principal component analysis. Based on the measured data and its statistical property, optimum color filters with Gaussian-type spectral transmittance were designed by simulated annealing method. Effectiveness of filter optimization is demonstrated by numerical evaluation.

Fifty-four spectral reflectances of skin colors (facial pattern of Japanese women) were measured and analyzed by the principal component analysis. The results indicate that the reflectance spectra can be estimated approximately 99% by only three principal components. Based on the experimental results, it is shown that the spectral reflectance of all pixels in skin can be calculated from the R, G, B signals of HDTV (High Definition Television) camera. Computer simulations of color reproduction in skin color have been developed in both colorimetric color reproduction and color appearance models by von Kries, LAB and Fairchild. The obtained color reproduction in facial pattern and skin color patch under different illuminants are analyzed. Those reproduced color images were compared by memory matching method. The difference of appearance models is described and the difference of appearance between skin color patch and facial pattern is also discussed and analyzed.

<BR>Projected grating method is introduced to measure the three dimensional pulp slurry surface behavior for the estimation of the sheet formation on the fourdrinier. For this purpose, a simple experimental system was composed of the slide projector, video camera, A/D converter and micro computer. The grating image deformed by a flow of pulp slurry on the wire was analyzed and the three dimensional form of the surface of slurry was calculated.As the results, it became clear that the calculated three dimensional form of the surface is considereably influenced by the scattering in the plup slurry, therefore obtained form doesn't represent only the characteristics of pulp slurry surface. However, the method was significant to analyze the variations of pulp slurry behaviour and the effect of the cationic retention aids in the pulp slurry.

When simulated annealing is applied to an ill-posed reconstruction of computer tomography images, the cost function should be appropriately modified to suppress artifacts arising from the ambiguity of null components. This paper shows such modification of the cost function and proves its performance through singular value decomposition analysis. Computer simulation shows good agreement with the analysis. © 1990 Optical Society of America.

Three-dimensional reconstruction of a bone image is important in medicine to facilitate making artificial bones by numerical control and to achieve computer simulations of surgical operations. Instead of gathering sectional tomograms obtained by computer tomography, a direct 3-D reconstruction, which is much better in terms of higher spatial resolution and smaller X-ray dosage, is used to extract the bone’s shape. A proposal and an experimental result are presented in this paper. © 1989, Optical Society of America.