| 摘要 |
A background light filter for use in an optical particle analysis system operates to attenuate light coupled thereto and pass an attenuated intensity light signal. If the light coupled to the filter takes the form of discrete beams or areas forming a pattern, the filter will selectively attenuate in only those portions of the filter struck by the light beams forming the pattern. The optical filter is substantially insensitive to short term variations in light coupled thereto so that changes in the received light pattern which may, for example, be produced by passage of a particle through the light beam producing the pattern, will be passed through the optical filter with substantially no attenuation.
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