The Journal of The Institute of Image Information and Television Engineers

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A new type of electrically controlled optical filter to heighten the color temperature of incident light has been developed that is comprised of guest-host mode liquid-crystal devices containing dichroic dyes. The transmission spectrum of the filter was designed as the ratio of different radiation spectra based on the black body radiation theory. The absorption for long-wavelength visible light is varied according to the liquid crystal alignment change for voltage applied to the filter. When white light with a color temperature of 5700K was incident on a filter fabricated with 6μm-thick liquid-crystal layers, the color temperature of light transmitted from the filter could continuously be changed from 6000K to 11000K by voltage control of less than 10 Vrms. The electrooptic response time was as fast as 50 ms. This liquid crystal optical filter is widely applicable to color-image input/output technologies, including the image sensing, display, and illumination fields.

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In this paper, it is shown that upstream digital signals are affected by the ingress noise in the upstream band of a two-way CATV system. The carrier-to-noise ratio of the digital data signal may be reflected by the immunity characteristics of each subscriber's unit, which consists of a CATV protector connected to a coaxial cable. It was found by bit-error-rate measurement in the two-way CATV model system that the value of the relative operating level is smaller in the UHF upstream band than the value in the HF to VHF one.

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A simple method based on IIR filters that approximates HRTFs (head-related transfer functions) has previously been proposed for realizing sound image localization. The purpose of this paper is to clarify the influence of the nonlinear phase characteristics of the IIR filters on the sound localization. First, the effectiveness of this method was verified by carrying out sound localization experiments using the approximated HRTFs for the direction sensation of a sound image on a horizontal plane in a two-loudspeaker reproduction. Next, localization experiments were carried out to investigate the influence of the phase characteristics on the localization by using both pink and narrow-band noises. The results showed that the influence, although it was dependent on the frequency band, was about 5 degrees on average, and the maximum was 10 degrees.

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Vector quantization is the process of encoding vector data as an index to a dictionary or codebook of representative vectors. One of the most serious problems for vector quantization is the high computational complexity involved in searching for the closest codeword through the codebook. In this paper, we describe a new method allowing significant acceleration of codebook design and encoding processes for vector quantization. This method has feature of using a suitable hyperplane to partition codebook and image data. Experimental results are presented on image block data. These results show that our method performs better than the previously known methods.

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