Optical communication of video information with distortion correction

DETAILED DESCRIPTION I claim: 1.
In an optical communication transmitter wherein a video signal is clamped, by a clamp circuit, with respect to a DC reference level and then coupled to a light-emitting diode, the light output of which is coupled over an optical link to a receiver having automatic gain control, the improvement comprising: a predistortion circuit coupled to the output of said clamp circuit for feeding back a portion of the video signal to said clamp circuit to dynamically change the DC clamping reference level of said clamp circuit, said predistortion circuit having an operator-adjustable time constant, whereby said time constant can be adjusted to compensate for distortions caused by the characteristics of said light-emitting diode.
2.
The transmitter as defined by claim 1, wherein said predistortion circuit also has an operator-adjustable feedback level.
3.
The transmitter as defined by claim 1, wherein said predistortion circuit comprises an adjustable resistor and a capacitor coupled in series.
4.
The transmitter as defined by claim 1, wherein said predistortion circuit comprises an adjustable resistor and a capacitor coupled to ground reference potential.
5.
The transmitter as defined by claim 4, wherein said predistortion circuit further comprises a voltage divider and wherein said adjustable resistor and said capacitor are coupled in series arrangement from between said voltage divider to ground reference potential.
6.
The transmitter as defined by claim 1, wherein said predistortion circuit includes a parallel arrangement of: a first adjustable resistor and a first capacitor coupled in series; and a voltage divider, and a second adjustable resistor and second capacitor coupled in series arrangement from between said voltage divider to ground reference potential.
7.
The transmitter as defined by claim 6, wherein said first adjustable resistor and first capacitor have a smaller time constant than said second adjustable resistor and second capacitor.
8.
The transmitter as defined by claim 6, wherein said predistortion circuit further comprises a series arrangement including a third adjustable resistor and a third capacitor, said series arrangement being coupled in parallel with the other portions of the predistortion circuit