Efficient dark current subtraction in an image sensor
AssigneeHewlett-Packard Development Company, L.P.
InventorRichard L. Baer
Life of this patent
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Abstract
A method for dark current subtraction which enables a dark frame to be reused for dark current subtraction for multiple image frames. The dark frame is reused by scaling it according to changes in the dark current levels associated with the dark frame and the image frames.
Claims18
A method for dark current subtraction, comprising the steps of:
- obtaining a dark frame from an image sensor;
- reusing the dark frame for dark current subtraction by scaling the dark frame in response to changes in dark current levels in the image sensor wherein the step of scaling includes the step of determining a difference between dark current levels in an image frame and dark current levels in the dark frame in response to a set of dummy samples in the image frame and the dark frame that represent a low charge level in the image sensor.
A method for dark current subtraction, comprising the steps of obtaining a dark frame from an image sensor and reusing the dark frame for dark current subtraction by scaling the dark frame in response to changes in dark current levels in the image sensor wherein the step of reusing the dark frame for dark current subtraction comprises the steps of obtaining an image frame from the image sensor, determining a different between dark current levels associated with the image frame and dark current levels associated with the dark frame, determining a scaled dark frame from the dark frame according to the difference, and subtracting the scaled dark frame from the image frame and wherein the step of obtaining dark frame comprises the steps of:
- obtaining a dark sample from each of a set of active elements of the image sensor;
- obtaining a dark sample from each of a set of optically black elements of the image sensor;
- obtaining a set of dummy samples that represent a low charge level in the image sensor.
An apparatus for dark current subtraction, comprising:
- means for obtaining a dark frame from an image sensor;
- means for reusing the dark frame for dark current subtraction by scaling the dark frame in response to changes in dark current levels in the image sensor wherein the means for reusing includes means for determining a difference between dark current levels in an image frame and dark current levels in the dark frame in response to a set of dummy samples in the image frame and the dark frame that represent a low charge level in the image sensor.
An apparatus for dark current subtraction, comprising means for reusing the dark frame from an image sensor, means for reusing the dark frame for dark current subtraction by scaling the dark frame in response to changes in dark current levels in the image sensor wherein the means for reusing the dark frame for dark current subtraction comprises means for obtaining an image frame from the image sensor, means for determining a difference between dark current levels associated with the image frame and dark current levels associated with the dark frame, means for determining a scaled dark frame from the dark frame according to the difference, and means for subtracting the scaled dark frame from the image frame wherein the means for obtaining a dark frame comprises:
- means for obtaining a dark sample from each of a set of active elements of the image sensor;
- means for obtaining a dark sample from each of a set of optically black elements of the image sensor;
- means for obtaining a set of dummy samples that represent a low charge level in the image sensor.
Dependencies are inferred from the claim text.