Automatic picture quality controller

An automatic image control device comprising:

• a lower-sideband variable-peaking circuit which receives an amplified FM signal that is output from a video head and that has had its frequency spectrum shifted to prevent the occurrence of black-and-white reversal phenomenon, wherein the peaking circuit peaks the lower sideband of the FM signal;
• a lower-sideband filter for extracting the lower-sideband spectral component from the FM signal;
• a comparator for comparing a d.c. voltage corresponding to a maximum detected amplitude of the extracted lower-sideband component with a reference voltage to generate an error voltage, wherein the error voltage is fed back to the lower-sideband variable-peaking circuit so that the amplitude ratio between the lower-sideband and carrier wave of the FM signal is constant, thereby enabling reproduction of images at high resolution;
• and
• an envelope detecting circuit for detecting the envelope of the voltage of the FM signal output from the video head, wherein the d.c. voltage corresponding to a maximum detected amplitude of the extracted lower-sideband component is overlain by the envelope-detected voltage.

An automatic image control device comprising:

• an AGC amplifier for amplifying a reproduced FM signal output from a video head to provide a uniform amplitude spectrum;
• a first lower-sideband variable-peaking circuit for peaking the lower sideband of the reproduced FM signal;
• a recording equalizer circuit for regulating a recording FM signal limited by a limiter so that the recording signal has a predetermined frequency characteristic;
• a second lower-sideband variable-peaking circuit for peaking the lower sideband of the recording FM signal;
• a lower-sideband filter for extracting the lower-sideband spectral component from the FM signal;
• a peak detecting circuit for converting the maximum amplitude of the lower-sideband spectral component of the extracted FM signal into a d.c. voltage;
• a comparator for comparing the d.c. voltage with a reference voltage to selectively output an error voltage to the first and second lower-sideband variable-peaking circuits;
• and
• a switch disposed between the lower-sideband filter and the first and second lower-sideband variable-peaking circuits, wherein the first lower-sideband variable-peaking circuit is connected with the lower-sideband filter by the switch during a reproducing mode to form a feedback loop, while the second lower-sideband variable-peaking circuit is connected with the lower-sideband filter by the switch during the recording mode to form another feedback loop.

An automatic image control device comprising:

• an AGC amplifier for amplifying an FM signal output from a video head to provide a uniform amplitude spectrum;
• an FM demodulating circuit for demodulating the amplified FM signal;
• a luminance-signal high-pass variable-peaking circuit for peaking the high-frequency spectral component of the luminance signal output from said FM demodulating circuit;
• a luminance-signal high-pass filter for extracting the high-frequency spectral component of the luminance signal from a video signal which has been input to a video input terminal on a VCR side from the video output terminal on a television receiver side;
• a peak detecting circuit for converting the maximum amplitude of the extracted luminance signal into a d.c. voltage;
• and
• a comparator for comparing the d.c. voltage with a reference voltage to generate an error voltage, wherein the error voltage fed back to the luminance-signal high-pass variable-peaking circuit to form a feedback loop, so that the spectrum of the luminance signal reproduced on the television receiver is uniform.

A method for use in an automatic image control device to produce sharp images, comprising:

• (a) amplifying an FM signal output from a video head with an amplifier;
• (b) detecting an envelope of the voltage of the FM signal output from the video head;
• (c) peaking the lower-sideband of the FM signal output from step (a) while maintaining an amplitude ratio between the lower-sideband and carrier wave of the FM signal constant;
• (d) extracting a lower-sideband spectral component from the FM signal subjected to step (c);
• (e) converting the maximum amplitude of the extracted lower-sideband spectral component to a d.c. voltage;
• (f) overlaying the d.c. voltage with the envelope-detected voltage to form a partial d.c. voltage;
• and
• (g) comparing the partial d.c. voltage with a reference voltage to generate an error voltage, wherein the error voltage is fed back through a feedback loop to step (c) so that amplitudes of the lower-sideband spectrum of the FM signal output from step (c) are substantially uniform, thereby improving sharpness of an image.

An automatic image control device comprising:

• a peaking amplifier which receives an amplified FM signal that has been output from a video head and amplified, and which shifts the amplified signal to prevent the occurrence of black-and-white reversal phenomenon;
• a lower-sideband variable-peaking circuit to peak the lower sideband of the amplified and shifted FM signal while maintaining an amplitude ratio between the lower-sideband and carrier wave of the FM signal constant;
• a lower-sideband filter for extracting the lower-sideband spectral component from the FM signal subjected to peaking;
• a comparator for comparing a d.c. voltage corresponding to a maximum detected amplitude of the extracted lower-sideband component with a reference voltage to generate an error voltage, wherein the error voltage is fed back to the lower-sideband variable-peaking circuit to regulate jutting amplitudes in the frequency spectrum of the lower-sideband to a uniform value, thereby improving sharpness of an image;
• and
• an envelope detecting circuit for detecting the envelope of the voltage of the FM signal output from the video head, wherein the d.c. voltage corresponding to a maximum detected amplitude of the extracted lower-sideband component is overlain by the envelope-detected voltage.

A method for use in an automatic image control device to produce sharp images, comprising:

• amplifying an FM signal input from a video head;
• detecting an envelope of the voltage of the FM signal input from the video head;
• shifting the amplified FM signal to prevent the occurrence of black-and-white reversal phenomenon;
• peaking the lower sideband of the amplified and shifted FM signal while maintaining an amplitude ratio between the lower-sideband and carrier wave of the FM signal constant;
• extracting the lower-sideband spectral component from the FM signal subjected to peaking;
• overlaying a d.c. voltage corresponding to a maximum detected amplitude of the extracted lower-sideband component with the envelope-detected voltage to form a partial d.c. voltage;
• and
• comparing the partial d.c. voltage with a reference voltage to generate an error voltage, wherein the error voltage is fed back to regulate jutting amplitudes in the frequency spectrum of the lower-sideband to a uniform value, thereby improving sharpness of an image.