Abstract
The spatial resolution of a conventional imaging lidar system is constrained by the diffraction limit of the telescope's aperture. The combination of the lidar and synthetic aperture (SA) processing techniques may overcome the diffraction limit and pave the way for a higher resolution air borne or space borne remote sensor. Regarding the lidar transmitting frequency modulation continuous-wave (FMCW) signal, the motion during the transmission of a sweep and the reception of the corresponding echo were expected to be one of the major problems. The given modified Omega-K algorithm takes the continuous motion into account, which can compensate for the Doppler shift induced by the continuous motion efficiently and azimuth ambiguity for the low pulse recurrence frequency limited by the tunable laser. And then, simulation of Phase Screen (PS) distorted by atmospheric turbulence following the von Karman spectrum by using Fourier Transform is implemented in order to simulate turbulence. Finally, the computer simulation shows the validity of the modified algorithm and if in the turbulence the synthetic aperture length does not exceed the similar coherence length of the atmosphere for SAIL, we can ignore the effect of the turbulence.
Highlights
A conventional optical imager is limited in spatial resolution by the diffraction limit of the telescope aperture [1]
If we want to bring the experiments to the outside for long-range application, e.g., air-borne or space-borne synthetic aperture imaging lidar (SAIL), many effects should be taken into account [5]
We have derived a modified frequency algorithm that is suitable for the SAIL in spotlight model using the heterodyne detection system and some results of a simulation of SAIL
Summary
A conventional optical imager is limited in spatial resolution by the diffraction limit of the telescope aperture [1]. Some prior research relates to SA processing in optical wavelengths for rotating objects like inverse synthetic aperture radar (ISAR) in microwave [2]. If we want to bring the experiments to the outside for long-range application, e.g., air-borne or space-borne synthetic aperture imaging lidar (SAIL), many effects should be taken into account [5]. Since the SAIL system uses continuous wave (CW) form while pulses are used in the SAR system [6], we can not directly make use of conventional SAR techniques like the model that Karr has described in his analysis [7]. As a result of the continuous wave, we can not provide a high pulse recurrence frequency (PRF), which will lead to azimuth ambiguity [8] in the spotlight model of the SAIL system. Considering the effect of the atmosphere that certainly has potential to do harm to SAIL resolution, the wave distortions caused by atmospheric turbulence will be simulated by means of phase screens, and analysis in provided
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