A novel beam-shaping method which obtains nearly uniform illumination for a high-power Laser Diode (LD) stack is
introduced. Based on the properties of the angular distribution during the Gaussian beams propagate, a flat-topped beam
profile can be achieved by the superposition of Multi-tilted Gaussian beams. Due to the theory above, the individual
lensing techniques are introduced to shape the beams of the LD stack. Cylindrical lenses are used to control the
divergence-angle of the output beams. By adjusting the offset of each cylindrical micro-lens, each output beam on the
fast axis gains the different tilted emitting-angle. Meanwhile the beams on the slow axis are also shaped by a large
cylindrical lens. Thus the beam-shaping optical system is designed to reconfigure the beams of a high power LD stack to
form a Multi-tilted Gaussian beam shape for a 10°×10° field-angle illumination. The simulation results from ASAP
software show that uniform illumination can be obtained in the far-field district. With the proper uniformity and high
efficiency, the beam-shaping optical system we have proposed for high-power LD stacks can be well suitable for laser
illuminator in laser active imaging and detecting system.
Scannerless imaging laser radar has been a focus of research in these years for its fast imaging speed and high resolution.
We introduced a three-dimensional imaging laser radar using intensified CCD as the receiver with constant gain and line
modulated gain. The distance map of a scene is obtained from two intensity images. According to the transmission
characteristics of the imaging system, a model of degeneration of the gray images is established and the range accuracy
of imaging laser radar based on this model is analyzed. The results show that the range accuracy is related with the
reflectivity, the actual distance and some other factors on the fast-distance-varying region, while it is mainly concerned
with shot noise for the flat area. On the basis of the cause of measurement error and the distribution characteristics of
noise, a method which uses iterative restoration algorithms on obtained intensity images is presented, Simulation is
carried out and the results show that root mean square error of distance map obtained with this method is decreased by
50%, compared with the distance map obtained by measurement. Finally the restoration results of radar images are
demonstrated to verify the effectiveness of this method.
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