KEYWORDS: Target detection, Pulsed laser operation, Photon counting, Pulse signals, Signal detection, Data processing, Ranging, Detection and tracking algorithms, Signal to noise ratio
Aiming at the method of photon counting laser ranging data processing for high-speed dynamic moving targets, a photon counting laser ranging data processing method based on polynomial motion delay compensation is proposed. This data processing method effectively improves the signal-to-noise ratio of high-speed moving targets through target motion polynomial modeling, multi-pulse motion delay compensation and accumulation. The simulation data is generated by the method of superimposing the real background noise to simulate the target echo, and the algorithm is verified. The results show that when the laser echo rate is 0.53% and the background noise rate is 2.57×106count/s, the target can still be accurately detected, which is equivalent to increasing the operating distance by about 1.43 times. The maximum distance measurement error is 0.29 meters, which is close to the distance resolution, effectively ensuring the distance measurement accuracy under weak signals.
The main drawback of diode laser array is the inhomogeneous intensity distribution in the far field. So the beam shaping
technology is very important in the application of laser diode array. This work present a novel beam shaping optical
system based on fly’s eye lens. The system can homogenize the diode laser array based on the multi-aperture beam
integrating theory. Such beam shaping system was designed by ray tracing method using ZEMAX™ Non-Sequential
Components analysis tools. The ray-tracing simulation shows that a 5 × 5 mm2 Top-Hat intensity profile was got at a
working distance of 40 mm and the homogeneity of the intensity distribution is better than 90%. And it is verified that
such beam shaping system is adapted for the aberrations of bars very well by simulation. Based on the design, a relative
experimental research on the beam shaping system for 5 bars LD stack is carried out. Through the beam shaping system
the laser diode power intensity is improved 4 times, light field distribution nonuniformity is less than 10%, and the
system coupling efficiency is more than 80%, which validated the engineering feasibility and applied value of this novel
LD array beam shaping system.
The analysis of scattering characteristics of diffractive optics based on Finite-difference time-domain method is
presented. And its scattering pattern along the surface is gotten. It shows that the scattering intensity in the discontinuous
surface is much higher than the continuous surface. This causes the decrease of diffractive efficiency. Binary optics with
multilevel relief can cause more scattering than micro optics with continuous relief, so it is not suitable for being used in
the situation where phase varies rapidly.
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