Stripmap mode synthetic aperture ladar imaging under large random phase errors condition

For exploring the characteristics and regularities of SAL imaging under large random phase error conditions, we build the stripmap mode SAL imaging experiment setup by using a 1 550-nm linear chirp laser. By using this device which can generate large common-mode random phase errors, we obtain stripmap mode SAL imaging experimental data under different target echo intensities. Using the phase gradient autofocus(PGA) algorithm of the stripe pattern, we complete the process with multiple iterations to obtain a high-resolution SAL image. When large random phase error exists in the range of [-6.45π, 6.45π], the SAL image cannot be focused by simple distance compression or azimuth matched filtering, and the signal to noise ratio(SNR) of the image can only be 3 dB. By PGA processing, the phase error can be significantly lessened, and a well-focused SAL image with SNR of 43 dB can be obtained. Experiments also show that PGA processing is robust in the presence of common-mode random phase error and the process continues to be valid when echo is as weak as 10-15 W. It can be concluded that in SAL systems that include large random phase errors(such as airborne SAL), PGA processing can effectively eliminate phase error and achieve sharper image focusing. In addition, increasing the detection laser power to increase the SNR of an image will strengthen effective PGA processing. © 2019, China Science Publishing & Media LTD. All right reserved.