FULL-FIELD AMPLITUDE AND PHASE MEASUREMENT OF LOUDSPEAKERS BY USING TV-HOLOGRAPHY AND DIGITAL IMAGE-PROCESSING

TV-holography has been combined with automatic data acquisition and image processing to calculate the amplitude and phase distribution of sinusoidally vibrating objects. The method is based on recording six holograms (video frames) where the amplitude and phase of the object and a vibrating reference mirror are varied in predetermined, calibrated steps. The image processing algorithms combine the frame information to solve for the unknown amplitude and phase of the test object. Various averaging techniques have been used to overcome stability problems and to increase the measuring accuracy and resolution. A description is presented of how the system can be used to analyze the vibration modes of loudspeakers. Different ways of displaying the amplitude and phase information are demonstrated and discussed. © 1993 Academic Press Limited.