1. A method of correcting effects of diffraction in a platen layer of an ultrasonic sensor, wherein the ultrasonic sensor comprises an ultrasonic transmitter, a piezoelectric receiver layer, an ultrasonic sensor array and a processor, comprising: capturing a plurality of images of a fingerprint having a plurality of phases in a time sequence; summing the plurality of images multiplied by a complex phase exponential to form an integrated complex image; aligning the integrated complex image to a pre-selected phase to form an aligned complex image; determining a maximum energy phase using the aligned complex image; and determining a maximum energy image to represent the fingerprint based at least in part on the aligned complex image at the maximum energy phase.