Experimental investigation on aero-optical effects of a hypersonic optical dome under different exposure times.

Abstract

The aero-optical effects induced by the complex flow structure around a hypersonic optical dome is highly unsteady, which leads to significant differences in the imaging quality under different exposure times. It is of great significance to study the influence of exposure time on imaging quality for guiding the design of imaging guidance seekers and improving imaging guidance accuracy. Based on the hypersonic gun wind tunnel, an aero-optical effect measurement platform was built to measure the wavefront from transient exposure to long exposure. With the increase of exposure time, the accuracy of high-order optical path difference (OPD) reconstruction by low-order Zernike polynomials increased from 62.2% to 88.6%. The increase of exposure time was helpful to reduce the complexity of the wavefront spatial distribution structure. In principle, it could reduce the difficulty of wavefront adaptive correction systems. With the increase of exposure time, the ${{\rm OPD}_{\rm rms}}$OPDrms corresponding to ${{\rm OPD}_{\rm high-order}}$OPDhigh-order increased gradually, the amplitude decreased gradually, and the difference of ${{\rm OPD}_{\rm rms}}$OPDrms decreased gradually at different times. Under different exposure times, the large-aperture approximation principle could achieve a better prediction of Strehl ratio values. With the increase of exposure time, the imaging integral resolution, $R$R, decreased obviously, and it was stable at about ${1.43}{R_0}$1.43R0. Compared with that, $R$R was improved by about 30% when the exposure time was 6 ns.