Integration time control

Claim 2

A charge coupled device camera with integration control of incident light along an optical path comprising: a lens in the path of said incident light; a two dimensional charge coupled device, CCD, placed in the path of said incident light after it has passed through said lens; a frustrated total internal reflection, FTIR, device placed between said lens and said CCD in said optical path; means for controlling said FTIR device connected to said FTIR device; camera control circuitry connected to said CCD; a light level error signal generator connected to said camera control circuitry; and a voltage to pulsewidth converter connected between said camera control circuitry and and said FTIR control means and said light level error signal generator.

Claim 3

A charge coupled device camera with integration control of incident light along an optical path as claimed in claim 1 where said light level error signal generator and voltage to pulsewidth converter comprise: an integrator circuit connected to said camera control circuitry; a sample and hold circuit connected in series to said integrator; an error generator with a predetermined threshold connected in series to said sample and hold circuit; an error gain control circuit connected in series to said error generator; an absolute value generator connected to said error gain control circuit; an error polarity detector connected to input from said error gain control circuit and to have two outputs, one of said outputs input to said absolute value generator; a comparator connected to said absolute value generator; a pulse generator connected to said comparator; a pulse counter connected to provide feedback to said comparators from said pulse generator; a counter limiter inputting said second output from said error polarity detector and also inputting the same signal fed to said pulse counter by said pulse generator; a first counter operatively connected to said counter limiter; a second counter inputting horizontal sync and vertical sync from said camera control circuitry; and a comparator inputting signals from both of said counters and feeding an output signal to said camera control circuitry.