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US 6,873,363 B1Granted
Technique for flagging oversaturated pixels
AssigneeMicron Technology, Inc.
InventorsSandor L. Barna, Eric R. Fossum
Life of this patent
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Abstract
An active pixel sensor (APS) that includes circuitry to eliminate artifacts in digital images. The APS includes a comparator for comparing a signal level from a pixel to an adjusted saturation voltage to determine if the pixel is saturated. If the pixel is saturated, an associated saturation flag is stored and used to replace the signal from the pixel with a maximum value corresponding to a brightest pixel in the image.
Claims10
An active pixel sensor comprising:
- at least one pixel comprising a photodetector that outputs an output level indicative of incoming light;
- a first sample and hold element electrically connected to the pixel operating to store a signal output level during a readout operation;
- a second sample and hold element electrically connected to the pixel operating to store a reset level during a readout operation;
- a third sample and hold element electrically connected to the pixel operating to store the signal output level during a comparison operation;
- an adjusted saturated voltage source, comprising a node that provides an adjusted saturation voltage;
- and
- a comparator having a first input node operatively connected to the third sample and hold element, a second input node electrically connected to the adjusted saturation voltage node, and an output node, said comparator operating to output a signal indicating whether the adjusted saturation voltage exceeds the output level from the photodetector.
4 more elements
An active pixel sensor comprising:
- at least one pixel comprising a photodetector;
- a sample and hold element electrically connected to die pixel and operating to store a signal level on the photodetector during a signal readout operation;
- an adjusted saturated voltage source, comprising a node that provides an adjusted saturation voltage;
- and
- a comparator having a first input node operatively connected to the sample and hold element, a second input node electrically connected to the adjusted saturation voltage node, and an output node;
- a latch electrically connected to the comparator output node, said latch operating to store a saturation flag in response to the adjusted saturation voltage exceeding the signal level;
- a select transistor operatively connected to the output node of the latch operating to enable readout of the saturation flag during a readout operation for the pixel;
- a differencing element electrically connected to the pixel and operating to produce a difference level from the signal level and a reset level output from the pixel during the pixel readout operation;
- an analog-to-digital converter for converting the difference level into a difference digital value;
- and
- a digital output selector comprising
- a detector operatively connected to the latch output node,
- an input node electrically connected to the analog-to-digital converter and an output node, and
- a switch operating to switch the difference digital value on the output node to a maximum digital value in response to the detector detecting a saturation flag.
11 more elements
A method for flagging an oversaturated pixel in an active pixel sensor array, the method comprising:
- reading a signal voltage from a pixel;
- comparing the signal voltage to an adjusted saturation voltage, wherein said adjusted saturation voltage is set to a minimum signal level;
- and
- storing a saturation flag in response to the signal voltage exceeding the adjusted saturation voltage.
1 more element
Dependencies are inferred from the claim text.