| 摘要 |
A light source (12) radiates an infrared beam (14) through the exhaust plume (22) of a motor vehicle (20) which passes in front of the source (12). A photosensor unit (18) includes a plurality of photodetectors (42,44,-46,48) which are spaced closely adjacent to each other and simultaneously sense the beam (14) after it propagates through the plume (22). An optical beam homogenizes or integrator (36) disposed between the plume (22) and the photosensor unit (18) causes the light incident on the photodetectors (42,44,46,48) to have uniform intensity. The photodetectors (42,44,46,48) are sensitive to different wavelengths corresponding to spectral absorption peaks of constituents of the composition of the plume (22), including carbon monoxide (CO), carbon dioxide (CO2) and hydrocarbon (HC). A computer (24) computes the composition of the plume (22) as the percentages of the constituents based on the sensed transmittances of the respective wavelengths through the plume (22). A video camera (26) produces a video image of the vehicle license plate (28), and a combiner (24,32) causes the video image to be displayed on a video monitor (30) and recorded on a video recorder (32) together with the plume composition data.
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