| The paper is based upon Aero-Optics theory, pursuing the methods and realization for measuring the density distribution of transient flow field in wind tunnel test. Aero-Optics research serves a very important and vital role in precise optical imaging detection of high-speed craft, airborne laser with precision targeting and irradiation and airborne electro-optical imaging system for precision tracking and targeting technology. Study results by improving can also be extended for Photo detection ground tracking system at long bowls and satellites. The flow around high-speed flight interfered images detecting system, which causes image migration, jitter and fuzzy phenomenon.The paper mainly aimed at establishing a mathematical model of axisymmetric fluid density distribution system and beam transmission. Finish a set of equipment with external synchronization acquisition for grabbing the wave front of flow field. With the data of flow field test, the flow information will be visualized dynamically.Compare various traditional flow testing methods, including shadow graphic, Schlieren, Shack-Hartmann and double beam interferometry. Found a novel measurement called radial shearing interferometer for flow field test. The method with no reference and high Anti-jamming, develop new fields for flow test.Against high-speed aircraft in remote and close the Properties, target detection need long exposure and short exposure. So an infrared laser with both continuous and pulse was selected. To decrease turbulent impact of imaging in close, the pulse less than 30ns duration with high repetition will freeze the turbulent. Also, a high speed CMOS digital camera and capture card were chosen. And form an integrity external synchronized image acquisition system.Designed and finished a set of precise short time delay circuit, which effectively matches the trigger pulse laser and CMOS camera shutter. Make sure that the camera will grab every pattern. The circuit realized 0.1 us or 1us, with 12 bit programmable control delay.Test the rapid flow with both long exposure and short one. Grabbing images with 450fps, 1024*1024 pixels, 50 λ, distortion. Analyze two turbulent modes of propagation effects.This research project provide a set of equipment with compact structure, strong anti-jamming capability, high spatial and time resolution for wind tunnel test, which will have a wide application foreground in the national defense and economic related fields. |
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