| 摘要 |
A photodetector is used to monitor contamination of optical elements within an optical system. The photodetector is aligned to detect nonspecular/diffuse reflections attributable to surface irregularities of particulate matter residing on the surfaces of the optical elements within the system. An increase in the intensity of the nonspecular reflections corresponds to increased levels of contamination on the surface of the optical element. An electronic detector circuit performs signal processing on the photodetector output signal and generates an output signal corresponding to the contamination level. In another aspect of the invention, the photodetector circuit is incorporated into a Raman gas analysis system. The invention also provides a method for detecting nonspecular reflection in an optical resonant system by generating and resonating an optical energy beam in an optical resonant cavity so as to irradiate an optical element within the cavity; detecting optical energy reflecting off the optical element; and generating an output signal functionally related to the intensity of the detected optical energy.
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