Acoustical Holography of Nonexistent Wavefronts Detected at a Single Point in Space

An experiment is described in which a hologram is recorded by scanning the source and having the detector stationary. The resulting ``scanned source'' hologram is shown to be identical to the conventional ``scanned detector'' hologram. The significance of this experiment is that it demonstrates: (1) that sampled holograms of an object can be recorded at a single point in space with either a scanning source or an array of sources; (2) that the object wavefront need not actually exist in space but may be geometrically synthesized; (3) that the object may be illuminated by a changing rather than stationary wave field. The interesting possibilities which this configuration gives rise to are briefly discussed.