Digital exposure circuit for an image sensor
AssigneeRound Rock Research, LLC
InventorsEric R. Fossum, Alexander I. Krymski, Roger A. Panicacci, Christopher Clark
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Abstract
Automatic exposure adjusting device considers the image on a pixel-by-pixel basis. Each pixel is characterized according to its most significant bits. After the pixels are characterized, the number of pixels in any particular group is counted. That counting is compared with thresholds which set whether the image is over exposed, under exposed, and can optionally also determine if the image is seriously over exposed or seriously under exposed. Adjustment of the exposure is carried out to bring the image to a more desired state.
Claims35
1-21. (canceled)
A device comprising:
- an analog to digital converter for producing a plurality of digital outputs comprising a plurality of bits, each of said digital outputs indicative of an output of at least one pixel of an image sensor;
- a first counter which counts a number of said digital outputs indicating overexposure during an image frame;
- a second counter which counts a number of said digital outputs indicating underexposure during said image frame;
- at least one threshold detector for comparing counting results of said first and second counters with desired thresholds;
- and
- a decision element for making a decision to either increase, decrease, or maintain an exposure of a next frame of said image sensor based on comparison results from the at least one threshold detector.
A method of controlling exposure comprising:
- obtaining a plurality of digital values representing values of pixels of an image sensor;
- reviewing only most significant bits of each of said digital values to determine if each digital value indicates an overexposed pixel or an underexposed pixel;
- comparing results of said determination with desired thresholds;
- and
- adjusting exposure of a next frame of said image sensor by:
- decreasing said exposure if a number of overexposed pixels is greater than or equal to a first threshold;
- and
- increasing said exposure if a number of underexposed pixels is greater than or equal to a second threshold.
A device comprising:
- an analog to digital converter for producing a plurality of digital outputs, each of said digital outputs indicative of an output of at least one pixel of an image sensor;
- a first counter which counts a number of said digital outputs indicating overexposure during at least one image frame;
- a second counter which counts a number of said digital outputs indicating underexposure during said at least one image frame;
- at least one comparator for comparing counting results of said first and second counters;
- and
- a decision element for making a decision to either increase, decrease, or maintain an exposure of a subsequent frame of said image sensor based on factors including comparison results from the at least one comparator.
A method of controlling exposure comprising:
- obtaining a plurality of digital values representing values of pixels of an image sensor;
- reviewing each of said digital values to determine if each digital value indicates an overexposed pixel or an underexposed pixel;
- comparing a number of digital values determined to indicate overexposed pixels in said determination with a number of digital values determined to indicate underexposed pixels in said determination;
- and
- adjusting exposure of a subsequent frame of said image sensor according to factors including said comparison.
Dependencies are inferred from the claim text.