Patent ID: 6404460
Filing Date: 2002-06-11
Classification: H04N

Abstract:
In a video edge enhancement circuit comprising first and second delay lines coupled in series, the input signal to the edge enhancement circuit being delayed for a first time period by the first delay line to produce a first delayed signal, the first delayed signal being delayed for an additional time period by the second delay line to produce a second delayed signal, the edge enhancement circuit further comprising first and second amplifiers with inverting and noninverting inputs, the inverting input of the first amplifier receiving the input signal of the edge enhancement circuit, the noninverting inputs of the first and second amplifiers receiving the first delayed signal from the first delay line, and the inverting input of the second amplifier receiving the second delayed signal from the second delay line, the outputs of the first and second amplifiers being combined and amplified by a sharpness control amplifier, the output of the sharpness control amplifier being combined with the first delayed signal from the first delay line to produce a video output with edge enhancement of the transitions in the input signal, the improvement comprising:providing a feed forward gain control loop to control the sharpness control amplifier and a threshold control for the sharpness control amplifier such that the sharpness control amplifier can be controlled to reduce background noise from the input signal by reducing low amplitude transitions from the input signal, wherein the threshold control of the sharpness control amplifier determines a threshold voltage, the threshold voltage determining when the video output will trend toward zero.