Sony Corporation

Kiyonori Tominaga

Atsushi Matsuzaki

Yasunobu Kuniyoshi

Susumu Akazawa

Takashi Okada

Takao Tsuchiya

Kinya Shinkai

Shouji Omori

Shoji Ohmori

As described above, according to the present invention, there is provided a color CRT display having a one-beam electron gun for reproducing colors by sequentially switching respective chrominance signals, R, G, and B, supplied to the one-beam electron gun. The color CRT display is characterized in that a color image displayed on a CRT screen is picked up by a CCD image pickup device and the image pickup signal is stored in an image pickup signal memory, the image pickup signal is compared with an original video signal stored in a video signal memory in terms of components of chromaticity using an arithmetic operator, and the frequency and phase of the image pickup signal of a VCO, which are required for determining the switching timing of chrominance signals in a multiplexer, are adjusted so that the difference between the image pickup signal and the original video signal in terms of components of chromaticity is minimized. With this configuration, it is possible to reproduce stably colors without generation of a black compression, even when the color CRT display is applied to a high precision display.

Color cathode ray tube display

A phase-tracking loop circuit which can be used, for example, as an FM detector or as a frequency-tracking control circuit to control the index signal of a beam-index cathode ray tube (CRT), includes an adder receiving an input signal of fluctuating frequency, a tracking filter coupled to the output of the adder and whose passband center frequency is shiftable, in response to a control voltage, to follow changes in the frequency of the input signal, an attenuator feeding an attenuated version of the output from the tracking filter back to the adder for combining in the latter with the input, and a phase comparator comparing the phase of the output of the adder with the output of the tracking filter to provide a corresponding control voltage to the tracking filter. If used as an FM detector, the control voltage can also constitute a demodulated signal. If used to control color switching in a beam index CRT, a controlled signal tracking the phase of the index signal can be derived from a phase-locked loop circuit which provides one of the inputs to the phase comparator in response to the output of the tracking filter.

Phase tracking loop circuit

In a beam index color television receiver having the screen of its color cathode ray tube provided with a repetitive pattern of a plurality of groups of different primary color phosphor elements arranged side-by-side across the image area of the screen to be scanned by a single electron beam as the latter is selectively modulated by respective color signals, index and mode set signals are provided in response to scanning by the beam of respective locations on the screen which are interspersed across the latter with distances therebetween which are non-integrally different from the pitch of the groups of color phosphor elements, and with adjacent locations corresponding to the mode set signal being spaced apart by an integral multiple of such pitch. The index signal can be provided by the scanning with the beam of index elements at the corresponding locations on the screen which emit light or other radiant energy, while the mode set signal may be provided in response to the absence of the index elements at the respective locations or to the presence, at the latter locations, of mode set elements which emit distinctive radiations when scanned by the beam. In any case, a gate pulse generator is responsive to the index signal to provide sequentially repeated gating signals by which the color signals are gated to selectively modulate the electron beam, and the phase and sequence of the gating signals are controlled in response to the mode set signal for ensuring that, as the beam scans each color phosphor element, the beam is modulated by the corresponding color signal.

Beam index color cathode ray tube

A color television receiver includes an automatic phase control circuit (which will be hereinafter referred to simply as an APC circuit) with a voltage controlled oscillator for controlling the phase of a reference carrier supplied to a color demodulator so that the phase and frequency of the reference carrier are locked to those of a color burst signal. In addition to the APC circuit, an auxiliary frequency control loop drives the frequency of the voltage controlled oscillator until its frequency falls within the lock-in range of the APC loop. The auxiliary frequency control loop includes a counter circuit for counting cycles of the output signal of the voltage controlled oscillator during a reference time interval and a decoding circuit for decoding the output of the counter circuit to produce an auxiliary control signal for frequency control of the voltage controlled oscillator.

Color television receiver AFPC circuit

In an automatic phase control circuit having a predetermined lock-in range wherein the oscillating signal produced by the adjustable oscillator of the automatic phase control circuit is used in combination with an input signal to derive a signal whose phase is compared to a reference signal, the phase difference between the derived signal and the reference signal being used as a phase control signal for the oscillator so as to minimize this phase difference and thus lock the phase of the derived signal to that of the reference signal, a method of adjusting the oscillator in the event that the phase relation between the oscillating signal and the input signal is outside the lock-in range. During recurrent intervals, which vary with time base errors in the input signal, the number of cycles of the oscillating signal is counted. The count is examined to determine whether it is within a predetermind range of a predetermined count, and if outside this range, the oscillating frequency of the oscillator is adjusted in a direction to return the count to within this predetermined range. In a preferred embodiment, this automatic phase control circuit is used to eliminate time-base errors in at least the chrominance signal of a composite color video signal. In such an embodiment, the adjustable oscillator is used in a frequency-converter for converting the frequency of at least the chrominance signal from an input frequency to a different frequency, and it is the phase of the frequency-converted chrominance signal which is compared to the reference signal.

Time-base error correction

A clamping circuit for color television signals includes a demodulator for demodulating the chrominance component of the color television signals to produce first and second color difference signals, and first and second adders for adding adjustable first and second control signals to the first and second color difference signals so as to produce modified first and second color difference signals. A matrix circuit is responsive to the outputs from the first and second adders to produce a third color difference signal. A reference signal, which represents a predetermined level of a color television signal, such as the pedestal level, is added to each of the color difference signals; and a first comparator compares the first color difference signal, with the reference signal added thereto, to the third color difference signal, with the reference signal added thereto, and a second comparator compares the second color difference signal, with the reference signal added thereto, to the third color difference signal, with the reference signal added thereto. At the times of occurrence of the pedestal level of the color television signal, the outputs from the first and second comparators are sampled, respectively, to produce the first and second control signals which are fed back and added to the first and second color difference signals. In one embodiment, the reference signal is a d.c. level proportional to the pedestal level of the color television signal. In another embodiment, the reference signal is the luminance component of the color television signal clamped to the pedestal level. This clamped luminance signal is produced by another clamp circuit.

Growing community of inventors

Tokyo, Japan

Kiyonori Tominaga