| 摘要 |
A radiation fringe velocimeter subsystem and a subsystem for determining air density related parameters, are combined into a single optical system (20) which permits various important parameters associated with the operation of an aircraft to be measured at a sample location at a sufficient distance from the aircraft (or any physical attachment thereto) so that the measurements will not be subject to systemic errors such as those caused by air compression effects and airflow disturbances, and which does not require that any Pitot tubes, pressure ports or other similar mechanical devices protrude into the airstream where the measurements are to be made. The combined system (20) contains a laser (32) or other suitable source of radiation (14) as well as an optical arrangement (36, 38, 40) for transmitting the radiation from the laser (32) to a sample volume (12) in order both to form linearly independent sets of radiation fringes (98, 100) at the sample location as well as to focus the radiation (14) at the sample location so as to cause selected air molecules to fluoresce. The device also contains an optical receiving arrangement (40) for focusing backscattered radiation and fluorescent emissions from the sample volume onto one or more photodetectors (42). By using a radiation source (such as a Q-switched laser) that can be quickly switched between an On state (110) and Off state (112), it is possible to utilize a single photodetector (42), since the backscattered radiation (120) will cease as soon as the radiation is turned off, but the fluorescent emissions (186) will decay exponentially.
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