Automatic sharpness control circuit for a television receiver

DETAILED DESCRIPTION It is an object of the present invention to provide an automatic control of the degree of picture sharpness, thus avoiding the noise accentuation in the case of low signal power while at the same time providing a selectable control for the preference of the viewer.
It is another object of the present invention to provide a sharpness control circuit in which the viewer may select the preferred picture sharpness without being concerned about the noise performance of the receiver at low signal levels.
This object is important because such a manual control is normally located by receiver manufacturers at the back of television receivers and it is not considered desirable to add the control to the more basic controls easily accessible from the front of the receiver.
An additional object of the invention is to provide a sharpness control circuit permitting the receiver to automatically select the desirable trade-off between the picture sharpness and picture noise.
It is still an additional object of the invention to provide a sharpness control circuit having flexibility and ease in the adjustment in the point at which actuation of the automatic sharpness control feature assumes control.
According to the present invention there is provided an improvement in a sharpness control circuit for a color television receiver.
The television receiver is of the type having a variable frequency response device for processing a demodulated video signal to establish the peaking of the response in frequency to the video signal and a device for selecting one of a plurality of predetermined characteristics of the frequency response device to provide selective peaking of the frequencies comprising the video signal thereby to vary the sharpness of the picture.
According to the invention, there is provided a device for establishing a controlled range of characteristics for at least one of the plurality of selected predetermined characteristics for the device in inverse relation to the strength of the received signal