Method and circuit for electronic shutter control

An apparatus for controlling the shutter open time in an opto-electronic device, said device comprising an illumination source for lighting an image, an optic lens, a photodetector array lying in the image plane of said lens, and an electronic shutter which allows said illuminated image to expose said photodetector array when said shutter is open, comprising:

• an average intensity control circuit which receives a frame pixel intensity values, calculates an average intensity value across said frame, compares said average intensity value to a first threshold, and generates a first control signal indicating whether or not said average intensity value is outside a first intensity range defined by said first threshold;
• a peak intensity control circuit which receives said frame, determines a peak intensity value across said frame, compares said peak intensity value to a second threshold, and generates a second control signal indicating whether or not said peak intensity value is outside a second intensity range defined by said second threshold;
• and
• an intensity control circuit which receives said first controls signal and said second control signal, and which adjusts said shutter open time in a first direction in response to said first control signal if said first control signal indicates that said average intensity value is outside said first intensity range, and which otherwise adjusts said shutter open time in one of either said first direction or a second direction if said second control signal indicates that said peak intensity value is outside said second intensity range.

An opto-electronic apparatus, comprising:

• an illumination source for illuminating an image;
• an optic lens;
• a photodetector array lying in the image plane of said lens which senses intensity levels of pixels of said image and generates a frame of pixel intensity values;
• an electronic shutter which allows said illuminated image to expose said photodetector array when said shutter is open;
• an average intensity control circuit which receives said frame of pixel intensity values, calculates an average intensity value across said frame, compares said average intensity value to a first threshold, and generates a first control signal indicating whether or not said average intensity value is outside a first intensity range defined by said first threshold;
• a peak intensity control circuit which receives said frame, determines a peak intensity value across said frame, compares said peak intensity value to a second threshold, and generates a second control signal indicating whether or not said peak intensity value is outside a second intensity range defined by said second threshold;
• and
• an intensity control circuit which receives said first control signal and said second control signal, and which adjusts said shutter open time in a first direction in response to said first control signal if said first control signal indicates that said average intensity value is outside said first intensity range, and which otherwise adjusts said shutter open time in one of either said first direction or a second direction if said second control signal indicates that said peak intensity value is outside said second intensity range.