[in Japanese]

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[in Japanese]

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[in Japanese]

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This paper discusses a colorimetry-based method to produce color prints whose tristimulus values match those of the colors displayed on CRT screens. It addresses a colorimetric linear model for CRT displays taking into account the gamma characterisics, and a nonlinear model for the equipment which produces color prints. The latter incorporates Bouguer's Law and the spectral charactrisics of illuminants which illuminate the hard copy. A set of mathematical equations for the common signals R, G and B is formulated as a function of the both models. The equation was solved by the method of least squares for the optimum color match. The validity of the theory is examined by evaluating the color differences in an actual example.

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We have produced digital pictures to be used in subjective assessments of HDTV picture quality.
A drum scanner is used as the input device, to assure useful quality for the assessments, and a series of signal processes are performed by computer. Some technical factors, such as resolution, aliasing, color reproduction, gray scale characteristics and precision of quantization are taken into account in producing the digital pictures.
To reduce the alias component, 16-times over-sampling is employed and sub-sampling with filtering is performed by computer. Gray scale characteristics are corrected by polynomial approximation, and color reproduction is compensated for by linear matrixing. After signal processing, precision of quantization becomes equivalent to that of the 10-bit linear quantization applied to the gamma pre-corrected video signal.

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This paper describes a new dynamic track following (DTF) system for home use digital VTR. The system's magnetic heads are moved by an electro-magnetic actuator and follow the recorded track on the magnetic tape. The shapes and dimensions of the actuator's elements are examined in order to get a higher resonance frequency. Actuator resonance is suppressed by a displacement control circuit. Experiments performed by using this new DTF system in an experimental digital VTR deck yielded the following conclusions. (1) The controlled band width is 300Hz. (2) The areal recording density is 2μm²/bit and the track density is 4200 TPI (track width : 6μm) on a metal evaporated tape.

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