Motion effects in scanned acoustic holography

Analytical and experimental results are presented concerning the effects of unwanted motion between the object and various elements of an acoustic imaging system during the recording of a scanned acoustic hologram using an electronic reference. It is found that the basic results are different for motions in different directions and that the principal effect on the hologram is distortion of the fringe pattern rather than blurring of the fringes as in optical holography. Various kinds of distortion for a variety of cases involving a moving ultrasonic point source are discussed. (In addition, the effect on image quality is analyzed for an extended test object that reflects, rather than is the source of, the ultrasonic waves which constitute the scene beam.) Analytical results are given for the decrease in resolution associated with the different kinds of motion. The approach used here is fundamentally deterministic in nature, as opposed to statistical, and only simple uniform motions are considered.