Operating a fingerprint sensor comprised of ultrasonic transducers

A method for operating a fingerprint sensor comprising a two-dimensional array of ultrasonic transducers, the method comprising:

• responsive to determining that an object is interacting with the fingerprint sensor during a low power mode, activating a plurality of subsets of the ultrasonic transducers of the two-dimensional array of the ultrasonic transducers, wherein each subset of the ultrasonic transducers of the plurality of subsets of the ultrasonic transducers is operable to capture an image, wherein each image is two-dimensional and non-adjacent to other images captured by other subsets of the ultrasonic transducers of the plurality of subsets of the ultrasonic transducers;
• determining a size of the plurality of subsets of the ultrasonic transducers that are activated based on a confidence of detection of a ridge/valley pattern of the object during a one-dimensional vector of pixels analysis at the fingerprint sensor;
• receiving a plurality of images corresponding to the plurality of subsets of the ultrasonic transducers of the fingerprint sensor, wherein the plurality of images are non-adjacent and two-dimensional;
• for each image of the plurality of images, determining whether the image of the plurality of images is indicative of a fingerprint;
• provided a number of images of the plurality of images that are indicative of a fingerprint satisfies a threshold, determining whether the images of the plurality of images that are indicative of a fingerprint are collectively indicative of a fingerprint;
• provided the plurality of images are collectively indicative of a fingerprint, determining that the plurality of images comprise a fingerprint;
• responsive to determining that the plurality of images comprise a fingerprint, processing a complete image at the fingerprint sensor;
• and
• responsive to determining that the plurality of images does not comprise a fingerprint, returning the fingerprint sensor to the low power mode.