# US 4,400,721 A · Transition system for color television receivers

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- Number: US 4,400,721 A
- Document ID: US4400721A
- Status: Granted
- Kind: A
- Application number: 06/282,400
- Filed: 1981-07-13
- Granted: 1983-08-23
- Earliest claimed: 1981-07-13
- Inventors: Albert Macovski
- Web page: https://patentgrep.com/patent/US4400721A

## CPC

- H04N 9/77: Circuits for processing the brightness signal and the chrominance signal relative to each other, e.g. adjusting the phase of the brightness signal relative to the colour signal, correcting differential gain or differential phase (circuits for matrixing H04N9/67)
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

The response of color television signals are improved by adding a high frequency luminance component which is proportional to the color-difference signal so as to provide color signals with correct transitions. The ratio of the derivative of the color difference signal to the derivative of the low frequency portion of the luminance signal is used to weight the amplitude of the luminance component.

## Claims

### Claim 1

In a method for enhancing the high frequency response of color television signals which are derived from a luminance signal and a plurality of color difference signals the steps of:
low-pass filtering the luminance signal;
deriving the high frequency components of the luminance signal by subtracting the low-pass filtered luminance signal from the luminance signal; and
applying the high frequency components of the luminance signal to the color television signals in an amount proportional to components of the color-difference signals.

### Claim 2

In a method for enhancing the high frequency response of color television signals which are derived from a luminance signal and a plurality of color difference signals the steps of:
forming the ratio of the derivative of the color difference signals to the derivative of the low-frequency portion of the luminance signal;
limiting the magnitude of the ratio of the derivative of the color difference signals to the derivative of the low frequency portion of the luminance signal
weighting the amplitude of high-frequency components of the luminance signal using the limited ratio; and
applying the weighted high-frequency luminance components to components of the color-difference signals.

### Claim 3

Apparatus for enhancing the high frequency response of color television signals which are derived from a luminance signal and a plurality of color difference signals comprising:
a low-pass filter for separating the low-frequency components of the luminance signal;
means for subtracting the low-frequency components of the luminance signal from the luminance signal for extracting the high frequency components of the luminance signal; and
means for adding weighted amounts of the high-frequency luminance components to the derived color television signals where the weights are proportional to components of the color difference signals.

### Claim 4

Apparatus for enhancing the high frequency response of color television signals which are derived from a luminance signal and a plurality of color difference signals comprising:
means for forming the ratio of the derivative of the color difference signal to the derivative of the low frequency portion of the luminance signal;
a limiter for limiting the magnitude of the ratio; and
means for using the limited ratio to control the amount of high frequency components added to the derived color television signals.