An apparatus, comprising: an ultrasonic sensor array; and a control system, at least part of which is coupled to the ultrasonic sensor array, the control system configured to: acquire first image data generated by the ultrasonic sensor array, the first image data corresponding to at least one first reflected ultrasonic wave received by at least a portion of the ultrasonic sensor array from a target object during a first acquisition time window, wherein the target object comprises a user's finger, and at least a portion of the first image data represents at least one fingerprint feature of the user's finger; acquire second image data generated by the ultrasonic sensor array, the second image data corresponding to at least one second reflected ultrasonic wave received by at least the portion of the ultrasonic sensor array from the target object during a second acquisition time window that is longer than the first acquisition time window, wherein at least a portion of the second image data represents at least one sub-epidermal feature of the user's finger; initiate an authentication process based on the first image data and the second image data; and wherein the control system is further configured to acquire third image data generated by the ultrasonic sensor array, the third image data corresponding to at least one third reflected ultrasonic wave received by at least the portion of the ultrasonic sensor array from the target object, and wherein the initiated authentication process is based, at least in part, on identifying a temporal-based feature difference of the target object between the third image data and either the first image data or the second image data; and wherein the initiated authentication process generates a liveness indicator based, at least in part, on the temporal-based feature difference of the target object. an ultrasonic sensor array; and a control system, at least part of which is coupled to the ultrasonic sensor array, the control system configured to: acquire first image data generated by the ultrasonic sensor array, the first image data corresponding to at least one first reflected ultrasonic wave received by at least a portion of the ultrasonic sensor array from a target object during a first acquisition time window, wherein the target object comprises a user's finger, and at least a portion of the first image data represents at least one fingerprint feature of the user's finger; acquire second image data generated by the ultrasonic sensor array, the second image data corresponding to at least one second reflected ultrasonic wave received by at least the portion of the ultrasonic sensor array from the target object during a second acquisition time window that is longer than the first acquisition time window, wherein at least a portion of the second image data represents at least one sub-epidermal feature of the user's finger; initiate an authentication process based on the first image data and the second image data; and acquire first image data generated by the ultrasonic sensor array, the first image data corresponding to at least one first reflected ultrasonic wave received by at least a portion of the ultrasonic sensor array from a target object during a first acquisition time window, wherein the target object comprises a user's finger, and at least a portion of the first image data represents at least one fingerprint feature of the user's finger; acquire second image data generated by the ultrasonic sensor array, the second image data corresponding to at least one second reflected ultrasonic wave received by at least the portion of the ultrasonic sensor array from the target object during a second acquisition time window that is longer than the first acquisition time window, wherein at least a portion of the second image data represents at least one sub-epidermal feature of the user's finger; initiate an authentication process based on the first image data and the second image data; and wherein the control system is further configured to acquire third image data generated by the ultrasonic sensor array, the third image data corresponding to at least one third reflected ultrasonic wave received by at least the portion of the ultrasonic sensor array from the target object, and wherein the initiated authentication process is based, at least in part, on identifying a temporal-based feature difference of the target object between the third image data and either the first image data or the second image data; and wherein the initiated authentication process generates a liveness indicator based, at least in part, on the temporal-based feature difference of the target object.