Experimental Research Of Ultraviolet Laser Slice Imaging

Laser has a small divergence angle, the beam is extremely narrow. It’s not easy to be intercepted by others and it has anti-interference ability and other advantages. Laser has been widely used in imaging. Range-gated imaging is an imaging way of laser imaging. By the control of the accurate gate door, the gate door can be open at any given time and it can image the target at a certain distance. It can effectively suppress background noise and backscattering noise, then to achieve to restore accurate distance information. Ultraviolet laser has the advantages of solar blind area, so that it’s not influenced by solar radiation. Ultraviolet laser has wide application in the field of imaging, but it’s not used in range-gated imaging. The focus of this study is that to use ultraviolet laser to make range-gated imaging and to verify the feasibility of slice imaging by using ultraviolet laser as the laser light source.Firstly, research the situation of laser range-gated imaging and ultraviolet laser imaging in China and foreign countries. Give the system performance of range-gated laser imaging system in China and foreign countries. Introduce an improved method on system parameters and the algorithm. Then introduce the applications of the domestic and foreign ultraviolet laser imaging.Secondly, introduce the basic principles of range-gated imaging and describe the principles of binarization algorithm and centroid algorithm which are used to process the images. Then describe the propagation characteristics in the atmosphere of ultraviolet laser. Use laser equation to deduce the formula of laser echo energy and then give the SNR model. Finally, describe the theory of sum frequency briefly.Thirdly, simulate the transmittance of ultraviolet laser in the atmosphere. Then simulate laser echo energy and SNR model according to the formula of them. Analyze the influence of laser pulse width and gate width on imaging results. Simulate slice imaging, contrast the conditions of binarization algorithm and centroid algorithm used to restore the distance image of target. It can verify centroid algorithm has advantages in distance accuracy. Compare the effect of range accuracy in the conditions of combinations of different gate width and step.Next, design overall program of the imaging system and build imaging platform. Adjust convex lens and LBO crystal in the emission optical system, to ensure a more stable ultraviolet laser output. Test the delay of each part in the system and give the whole timing sequence of the system.Finally, image a single carton and restore the distance information of the carton accurately. It can verify the feasibility of ultraviolet laser slice imaging. Then in the conditions of two kinds of gate triggering width at 10 ns and 15 ns, image three planes with imaging gradient. It can get the conclusion that narrower gate width can acquire higher range accuracy under the premise of no loss of information. The range accuracy of the system can reach 10 cm.