Fiber Doppler lidar systems the advantage of high velocity precision over conventional differential velocity measurement. However, the velocity precision of fiber Doppler lidar systems may be degraded by the complex motion of the target, the roughness of the target and the discrete digital data processing. In this paper, a setup of 1064 nm fiber Doppler lidar system is proposed to measure the velocity of radial moving targets. Detailed theoretical analysis was conducted with the influence factors on the velocity precision of the system, and simulations were conducted with an optimized design. A prototype was constructed in the laboratory and experiments were carried out with the prototype. The experimental velocity was 2.65 cm/s, and the relative velocity precision was superior to 0.3%, which proved the validity of the research.
Nowadays LADAR system set on practical moving platform is purposed to detect real-time velocity as well as precise distance and direction evaluation for safe landing or obstacles avoiding. On account of narrow band, brief algorithm, non-modulated CW Doppler LADAR based on optical heterodyne principle could acquire the velocity of multiple targets with high frame frequency, high SNR ratio while no velocity ambiguity. In this paper, a non-modulated 1064nm CW Doppler fiber LADAR system with high frame frequency as well as high velocity precision is proposed. The experimental result of the system shows a velocity precision of 6.65mm/s, and a velocity detection frame frequency of 20FPS, which essentially meet the practical demands.
Based on the classical optical coherence theory, a single detector virtual ghost imaging (VGI) with partially coherence hyperbolic cosine Gaussian beam has been demonstrated theoretically. An analytical imaging formula is obtained and the numerical calculation results lead to the influences of the turbulence strength, the propagation distance and the coherent parameters of the beam on the imaging quality. Moreover, we find that the VGI with hyperbolic cosine Gaussian beam can resolve the target better than the VGI with the conventional Gaussian Schell model beam under similar conditions.
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