طراحي، شبيه‌سازي و بهينه‌سازي سامانه‌ي اپتيكي ليدارهاي هوابرد براي نقشه‌برداري جغرافيايي سه‌بعدي

Lidar, Calibration, Scanner, Laser Beam Diameter, ZEMAX Software, Important Optical Components, Effective Optical Diagrams, Transmitter, Receiver, an‎d Optimization.

Designing,‌ Simulating an‎d Optimizing the optical system of airborne lidars for 3D geographic mapping

فيزيك

The Lidar system is a remote sensing tool that uses a laser beam to measure distances, an‎d the work this technology does is similar to the radar system, with the difference that radar works with radio waves an‎d can be said that lidar is used in military, industrial, an‎d general fields; therefore, studying it is essential. This system has different types, an‎d in this study, airborne lidar was used an‎d its concept is that the lidar system is installed on an aerial platform along with a scanner, as a result, a range of the flight path is scanned an‎d it provides us with a three-dimensional map of the path; therefore, to prepare this map, we need different data from this system; for this reason, the accuracy of the measured data is important to us, an‎d we must find the errors an‎d deviations that result from the combination of flight an‎d lidar data an‎d remove them from our data to reach a reasonable amount. For this purpose, in this study, several methods for calibrating the lidar system are described to ensure the required accuracy of the final results of this system an‎d among these, the simplified calibration method was selec‎ted an‎d its mathematics were fully discussed an‎d examined. Also, using this method, we were able to design flight strips an‎d obtain their errors. So, in this part we were able to improve the data up to 90%. In another part of this research, we studied an‎d compared different scanners for mapping at high altitudes an‎d concluded that the quadrangular tower mirror scanner is a good choice that is calibrated with the same data calibration method. Also, another issue that is important to us in the field of lidar is the divergence of the laser beam, which creates problems for us when using it at high altitudes; among them, we can mention the enlargement of the laser footprint on the ground an‎d as a result, the increase in the scattering of the beam in different directions, in which case not much reaches the detector. Therefore, considering the divergence of the laser beam, we designed a beam expan‎der an‎d parallelizer. By doing this, we were able to control the divergence of the laser beam in such a way that the same diameter of the beam exiting the transmitter aperture reaches the target. Also, for the design of the receiver, considering that the beam that is to be scattered from the target is ideal, that is, the same beam that hits the target is reflected, this beam will still diverge along the way, so for the receiver, we need a suitable receiving aperture, which has been addressed in this research; Therefore, several transmitters an‎d receivers were designed using ZEMAX software an‎d optimal modes for these two were expressed. Also, important optical components an‎d effective diagrams for both were discussed an‎d finally, the results were expressed an‎d compared with respect to the diagrams an‎d components of these optimizations.

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