Control of brightness level adapted to control of contrast

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG.
1, there is shown a transfer function according to the present invention wherein the range of the brightness control is modified according to the contrast control setting.
The abscissa shows a brightness control setting from zero to 100 percent and the ordinate calibrated in a normalized brightness output voltage V.
sub.
brt.
The transfer function of FIG.
1 has a linear constant slope portion 10, wherein the output or control voltage V.
sub.
brt increases linearly with the brightness control setting for low brightness settings regardless of the setting of the contrast control.
However, for high brightness settings, beyond a point 12, the transfer function can be any of family of curves including portion 11 which is a linear continuation of portion 10 when maximum contrast is set, to portion 13 which has a reduced slope when minimum contrast is set.
It should be noted that portion 13 and others of the family of curves have a slope of greater than zero.
In an alternative embodiment, the family of curves may have a slope at or near to provide a sharper brightness control cutoff.
However, it is believed that the reduced slope gives the viewer a better "feel" to the control.
FIG.
2 shows a schematic of one embodiment for implementing the transfer function of FIG.
1.
Generally speaking, a television signal received by an antenna 5 or other appropriate source of signal such as a cable system, is processed by a tuner 6, intermediate frequency (IF) amplifier 7 and detector 8 with the luminance signal at 9 being separated from the chroma signal at 10.
The luminance and chroma signals are appropriately processed and combined in matrix 11 for driving CRT 12.
The luminance signal processing typically includes amplification and signal processing to implement various luminance signal attributes such as contrast and brightness.
A contrast control unit 20 comprises a potentiometer 22 coupled between an appropriate source of voltage V.
sub