Multi-beam Modulated Photon-counting Laser Imaging

Laser imaging has been widely used in city modeling,bridge construction and topographic mapping.Due to the high resolution of ranging,long distance of detection and abundant information of returning signal,the laser imaging playing an important role in the imaging technology field.With the development of single-photon detection and time-correlated single photon-counting,the laser imaging system could achieve longer distance and higher resolution as never before,which shows great potential.Scanning with multi beams,multi-beam photon-counting imaging system has high imaging efficiency and wide field of view covering,which is an important development direction in photon-counting laser imaging.This thesis focuses on the technology and method of modulation of beams,to improve the system of multi-beam photon-counting laser imaging.This thesis proposed and demonstrated the technology of modulation of the laser pulse.Using the time correlation between the synchronization signal and returning photons,just a single-pixel single-photon detector was used to detect the returning photons of all the beams simultaneously.Rather than solving the difficulty of making single-photon detector array,a practicable and simple design of multi-beam singlephoton counting laser imaging system was demonstrated.A 16-beam single-photon counting laser imaging system was developed based on this technology,and only a single-pixel Si-based single-photon detector was used to detect all the 16-beam returning photons.A lobby was scanned to test the performance of this system.With scanning angle vertically covering of 261.80,horizontally covering of 2.98 rad,depth resolution of 28.5 cm,detection precision of 48.0 mm,a 9600 pixels 3D image was got.This thesis developed the technology of modulation of intensity and laser angle.A rectangle beam array system and a linear beam array system were demonstrated.Both systems were using a 100-channel Si-based avalanche photodiode array and a 100-channel time-correlated single photon counting module.The system with rectangle beam array had high beam covering rate in the field of view,with adjacent beams angle of 0.13 mrad.And the wavelength of laser used in this system was 1064 nm,which was invisible.It's suitable to be use as military target searching and alarming lidar.And this system was tested to scanning the buildings 950 m away.No space between adjacent spots was achieved.The system with linear beam array had wide field of view covering,with 100 beams totally covering 24.75 mrad.The wavelength of laser used in this system was 532 nm.The detector had high detection efficiency in this wavelength.And this system was suitable to be used as target imaging and mapping lidar.This system was tested to scanning the playground 400 m away.With scanning angle covering4.0°×1.4°,a 6400 pixels 3D image was got.