Research of transient flow field real time interferogram acquisition system

摘要

This paper describes a novel synchronous control system of high speed imaging, which combines a common path interferometer system modulated by the space phase. The system can continuously grab multiple frame interferograms, which contain transient flow field distortion. The study of this system will provide a fire-new means for the research of aerodynamics. The light source of the system is Nd: YLF semiconductor pump solid pulsed laser of which wavelength is 1053 nanometers. The laser pulse width is less than 30 nanoseconds, far less than the exposure time of the camera shutter. Thus the laser pulse can freeze the flow field within several dozen nanoseconds and catch the biggish change of turbulent flow. The pulsed laser beam containing the information of turbulent flow enters a cyclical radial shearing interferometer. The emergent lights, being respectively contracted and expanded , re-combine and form fringe pattern in high space frequency, modulated with a definite carrier frequency. The fringe pattern is formed on the high speed CMOS camera at last. An accurate short time delay circuit is provided for synchronization matching of the pulsed laser and camera exposure. The speed of image acquisition in full pixels with 1280×1024 can reach 450 frames per second. This interferogram acquisition system with compact configuration and strong anti-disturbance capability, has successfully grabbed clear transient interferograms that provided reliable image information for follow-up image processing and flow field density calculating.