Reversible color component transforms derived by the LU factorization are briefly described. It is possible to obtain an reversible implementation to a given component transform, even if the original transform is irreversible. Some examples are presented and their performances are compared in image compression.

A blind equalization algorithm which makes use of the Stop" region of the Stop-and-Go algorithm is proposed. By adaptively updating the tap weights at the Stop region as well, it is intended to improve the convergence property of the Stop-and-Go algorthm. The performance of the proposed algorithm is compared with the conventional Stop-and-Go algorithm using various communication channels. Simulation results indicate the improvement of the convergence speed while maintaining or possibly lowering the residual error.

In this letter, we study on the sensitivity to the electrical stimulus pulse for biomedical electronics for the purpose to make a tactile vision substitution system for binds. We derive the equivalent circuit of finger by measuring sensitive voltages with various touch condition and various DC voltage. And we consider to the sensitivity of finger against electrical stimulus pulse. In order to convert the sense of sight to tactile sense, we consider four types of touch condition and various types of pulse. It is shown that the sensitivity of finger to electrical stimulus pulse is determined by duty-ratio, frequency, hight of pulse and the type of touch condition. In the case that duty-ratio is about 20%, frequency is within about 60-300Hz and touch condition is A-4 type, the sensitive voltage becomes the lowest. With this result, a tactile vision substitution system can be developed and the system will be used to transfer various infomations to blinds without paper.

We introduce an extended EZW coder that uses flexible zerotree coding of wavelet coefficients. A flexible parent-child relationship is defined so as to exploit spatial dependencies within a subband as well as hierarchical dependencies among multi-scale subbands. The new relationship is based on a particular statistics that a large coefficient is more likely to have large coefficients in its neighborhood in terms of space and scale. In the flexible relationship, a parent coefficient in a subband relates to four child coefficients in the next finer subband in the same orientation. If each of the children is larger than a given threshold, the parent extends its parentship to the neighbors close to its conventional children. A probing bit is introduced to indicate whether a significant parent has significant children to be scanned. This enables us to avoid excessive scan of insignificant coefficients. Also, produced symbols are re-symbolized into simple variable-length binary codes to remove some redundancy according to a pre-defined rule. As a result, the wavelet coefficients can be described with a small number of binary symbols. This binary symbol stream gives a competitive performance without an additional entropy coding and thus a fast encoding/decoding is possible. Moreover, the binary symbols can be more compressed by an adaptive arithmetic coding. Our experimental results are given in both binary-coded mode and arithmetic-coded mode. Also, these results are compared with those of the EZW coder.

The error diffusion filter in this paper is optimized with respect to the ideal blue noise pattern corresponding to a single tone level. The filter coefficients are optimized by the minimization of the squared error norm between the Fourier power spectra of the resulting halftone and the blue noise pattern. During the process of optimization, the binary pattern power spectrum matching algorithm is applied with the aid of a new blue noise model. The number of the optimum filters is equal to that of different tones. The visual fidelity of the bilevel halftones generated by the error diffusion filters is evaluated in terms of a weighted signal-to-noise ratio, Fourier power spectra, and others. Experimental results have demonstrated that the proposed filter set generates satisfactory bilevel halftones of grayscale images.

In this paper, the fundamental characteristics of tactile recognition by electrical stimulus in order to develop a vision substitution system were described. The electrical stimulus pulse or DC voltage was applied at a touch board, and a conducting band which was connected to the ground level was fastened around a root of finger. First of all, the resistance of finger by the DC voltage was measured and the equivalent circuit of a finger was estimated. It was found that the most of resistance of this mechanism was concentrated at the contact of tip of finger and its value reached to MΩ order. And this resistance widely varied by the contact condition. The resistance of finger itself was relatively low and the contact resistance of band connectoin was about 30 kΩ. Total stray capacitance was about 26-62 nF, which was calculated by our experiments. Secondly, the minimum recognition voltage to applied stimulus pulse was measured by changing frequency, duty-ratio and voltage of pulse. It was found that the most sensitive pulse was in situation of that the frequency range was within from 60 Hz to 300 Hz, the duty-ratio of 20%, and the minimum sensitive voltage was about 13V. Lastly, this electrical stimulus pulse was applied to the touch Braille board. A touch Braille board was controlled by a computer (PC8801). In this system, an input letter from keyboard is translated to Braille code data by a computer automatically, which express the letter by the 6 points for the brind. And a Braille data is output at a touch board. By touching on the contact point of the touch board, a person can recognize Braille points by electrical stimulus. It was found that the Braille recognition by electrical stimulus pulse was available as same as it could be done by raised points.

A zerotree image-coding scheme is introduced that effectively exploits the inter-scale self-similarities found in the octave decomposition by a wavelet transform. A zerotree is useful for efficiently coding wavelet coefficients; its efficiency was proved by Shapiro's EZW. In the EZW coder, wavelet coefficients are symbolized, then entropy-coded for further compression. In this paper, we analyze the symbols produced by the EZW coder and discuss the entropy for a symbol. We modify the procedure used for symbol-stream generation to produce lower entropy. First, we modify the fixed relation between a parent and children used in the EZW coder to raise the probability that a significant parent has significant children. The modified relation is flexibly modified again based on the observation that a significant coefficient is more likely to have significant coefficients in its neighborhood. The three relations are compared in terms of the number of symbols they produce.