| 摘要 |
An optical interferometer and an ultrasonic distance measuring subsystem are used to obtain spectra from the surface of a sample. The interferometer uses a broadband electromagnetic radiation source and modulates the radiation at a frequency which is inversely proportional to wavelength. The modulated radiation impinges on the surface of interest where it is absorbed. The absorption of radiation causes the surface of the sample to expand. This change in dimension is then detected by the ultrasonic distance measuring subsystem which employs a single frequency acoustic radiation source to measure the instantaneous distance between the sample surface and the ultrasonic distance measurement subsystem. The detected changes in distance relate to amplitude of absorption at a given wavelength, thereby allowing absorption spectra for surface point to be generated indicating the chemical composition of each point of the surface.
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