Long Range Single-photon Three-dimensional Imaging

Long-range active three-dimensional imaging is widely used in many applications,including three-dimensional remote sensing,spaceborne mapping,airborne surveil-lance,ground-to-space detection,long-range target tracking and recognition,and so on.Long-range LiDAR continues to move toward smaller,lighter,and lower power.With the development of technology,the detection limit of traditional photodetectors has become the bottleneck of the development of traditional LiDAR.In recent decades,quantum technology has developed rapidly.New technologies based on quantum tech-nology are constantly emerging,breaking through the traditional technology by means of quantum technology.Quantum technology has also given LiDAR a new develop-ment opportunities——single-photon LiDAR.Single-photon LiDAR provides single-photon sensitivity and picosecond time resolution,breaking the technical restrictions of traditional LiDAR.It can only increase the detection distance,detection signal strength,and signal-to-noise ratio by increasing the laser power and increasing the telescope aper-ture before.However,although single-photon LiDAR has made important progress in recent years,there are still huge challenges in long-range applications.On the one hand,the expansion of the beam and field of view at long distances limits the spacial resolution,deteriorating the quality of imaging and seriously weakening the detection and identifi-cation capabilities.On the other hand,due to the existence of huge attenuation,when the imaging distance is extended to tens of kilometers or hundreds kilometers,the returned echo is extremely weak and mixed with strong noise.Aiming at the challenges faced by long-range single-photon imaging,this paper explains the technology about long-range single-photon imaging system,including the long-range LiDAR detection model,free space optical technology,integrated noise sup-pression methods,single-photon detection,and time-correlated single photon count-ing technology.Based on these explanation,a design for building a long-range high-resolution single-photon LiDAR is proposed,and it is also studied and analyzed in detail.In the design,we developed technical methods that can effectively improve the performance,such as two stages fine field-of-view scanning and polarization noise suppression.Finally,we built an efficient,low-noise coaxial scanning single-photon LiDAR system prototype.With regards to the problem of insufficient spacial(lateral)resolution of long-range LiDAR,we have innovated a method of sub-pixel precision scanning combined with a convolutional accurate model that considers transmitting beams and FoV expansion to effectively improve the resolution of a single photon imaging system.We have achieved 8.2 kilometers of super-resolution all-day three-dimensional imaging.For the extension of imaging distance,a high-efficiency coaxial scanning imaging system can effectively collect very weak echo photons,and the comprehensive filtering methods we have adopted can significantly suppress the system background noise.At the.same time,we have developed a computational algorithm that offers high-resolution reconstruction and high photon efficiency for the data of low photon counts(i.e.,?1 sig-nal photon per pixel)mixed with high background noise(i.e.,signal to background ratio?1/30).We experimentally demonstrated active single-photon 3D-imaging at a distance of up to 45 km in an urban environment.After a further improvement of the system and a new extremely low-noise single-photon detection method,we finally created a single-photon three-dimensional imaging distance record up to 202 km,which is an order of magnitude farther than the previous farthest single-photon three-dimensional imaging reported.