| 摘要 |
In elastic-wave holography where transducers are used to convert the detected elastic waves into corresponding electrical signals, the phase pattern of many transducers spread over the hologram area is recorded by sampling all of the electrical signals during one cycle of the coherent elastic waves to get a relative time delay for the zero-axis crossings of each signal. Pulses at zero-axis crossing times, produced by amplifying, clipping, and differentiating the signals, are then shaped or stretched to form short square waves of time duration M, or phase duration K electrical degrees, where K equals 360 DEG /L, L being the integral number of phase intervals into which the coherent-wave cycle is subdivided. Each value of K also corresponds to one step of the gray scale used in recording the final hologram.
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