An Optimal black separation signal prediction method in the mean square error (MSE) sense is presented for color printing image coding. In this method, a prediction error signal (eK) is defined as the difference between an actual black separation k signal and a predicted k signal with luminance. In this prediction, the k signal predictor is statistically designed under a criterion of minimization of the mean square prediction error, so that the predicted value is equal to the conditional expected value of k for each luminace level. By the cmy-YIQ conversion and the use of an eK signal instead of a k signal, the spectral redundancy among the c, m, y and k signals is removed, and more efficient coding is expected. In the coding scheme, these Y, I, Q and eK signals are spatially coded separately. The simulation results show that YIQeKDPCM coding applying this prediction method is superior to conventional YIQkDPCM coding in SNR for the k signal.

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In this paper, we propose a color quantization method for moving images which efficiently composes color quantized moving images with stable colors. In this method, the initial set of colors is chosen from the first frame, and used with high priority for the rest of the image sequence to achieve stable color allocation. To use the high correlation between subsequent frames, the color difference of each corresponding pixel between subsequent frames is first calculated and compared with the appropriate threshold. Then the pixels whose color differences are under the threshold are allocated to the same colors of the corresponding pixels of the preceding frame, and the colors of other pixels are reallocated. By this method, only differential operation is employed for most pixels.
This method can also detect scene changes by monitoring the content of the “LUT”, so that it can deal with various kinds of moving images.
Several experimental results in which the images of 2²⁴ colors are quantized to 16 colors reveal the effectiveness of the proposed method.

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A new beam-index system with two different index phosphors in each primary color triplet is developed which is able to achieve a stable beam position detection. The phosphor screen is single-layered and composed of R, G and B phosphors, ultra-violet short persistent index phosphor between B and R phosphors, and green short persistent index phosphor mixed with G phosphor. This structure allows easy production of the beam-index tube. The results of theoretical analysis about index signal phase error φ_E and color saturation C_s in red color reproduction show that φ_E is 3.5° and C_s is 97% where beam spot diameter D_n normalized by triplet pitch is 1/6, 6.7° and 86%, where D_n is 1/3, 9.7° and 65%, where D_n is 1/2. The experimental results measured by trial-manufactured 1.5-inch display (D_n ≅1/2) resembles the theoretical results.

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[in Japanese]

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[in Japanese]

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