| 摘要 |
An apparatus and method for the nondestructive inspection of dielectric matierals are disclosed. Monochromatic, phase coherent electromagnetic radiation (6), preferably in the 5-50 gigahertz frequency range (i.e. microwaves) impinges on the sample. In accordance with Snell's law, the microwaves are partly transmitted and partly reflected at each interface where the dielectric constant changes due to irregularities. A portion of the reflected beam is combined with the signal reflected by the specimen being inspected. These two signals have the same frequency, but may differ in amplitude and phase. The signals combine to produce an interference pattern, a pattern that changes as the specimen changes, or as the position of the specimen changes relative to a detector (2, 4). A computer (10) is programmed to distinguish features in the interference pattern attributable to irregularities in the material from features in the interference pattern attributable to sources of noise.
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