Darkfield tracking

An electronic device comprising:

• a fingerprint sensor;
• a memory;
• and
• a processor configured to:
• determine whether an object is interacting with the fingerprint sensor;
• provided an object is not interacting with the sensor, make a determination that a darkfield candidate image can be captured at the sensor;
• determine whether to capture a darkfield candidate image at the sensor based at least in part on the determination that a darkfield candidate image can be captured at the sensor;
• responsive to making a determination to capture the darkfield candidate image, capture the darkfield candidate image at the sensor, wherein the darkfield candidate image is an image absent an object interacting with the sensor;
• and
• update a darkfield estimate with the darkfield candidate image.

A non-transitory computer readable storage medium having computer readable program code stored thereon for causing a computer system to perform a method for darkfield tracking at a sensor, the method comprising:

• determining whether an object is interacting with the sensor;
• provided an object is not interacting with the sensor, making a determination that a darkfield candidate image can be captured at the sensor;
• determining whether to capture a darkfield candidate image at the sensor based at least in part on the determination that a darkfield candidate image can be captured at the sensor;
• responsive to making a determination to capture the darkfield candidate image, capturing the darkfield candidate image at the sensor, wherein the darkfield candidate image is an image absent an object interacting with the sensor;
• updating a darkfield estimate with the darkfield candidate image;
• responsive to detecting an object interacting with the sensor, capturing an image comprising the object;
• and
• correcting the image using the darkfield estimate.