Photon-limited Ghost Imaging Under Single Photon Detection

Photon-limited imaging has attracted great interest due to its important applications under extreme lighting conditions,such as long-range laser three-dimensional imaging,underwater target detection,astronomical observation,biological detection,particle physics,etc.In the detection under extremely low photon flux,the received light echo signal energy is extremely weak,usually only a few photons or even a single photon.With the development of new photoelectric detection technology,detectors with single-photon sensitivity are widely studied and applied in the field of extremely weak signal detection and single photon imaging.While even with a single photon detector with time resolution capability,traditional imaging technology usually requires 10~3-10~5photons per pixel to restore and reconstruct an image.It requires a very long time and sufficient laser power,and often faces the imaging failure caused by environmental noise interference and target movement.Ghost imaging,also known as"correlation imaging"or single-pixel imaging,is a new imaging mechanism which utilizes physical association characteristics of the light field to recover the target information.It breaks through the limitations of the traditional linear optical system,and can realize the separation of object and image,lensless imaging and single-pixel imaging,so it has the advantages of anti-channel noise,super-resolution,compressed sensing,weak signal imaging,multi-spectral imaging,etc.But as a price for those advantages,it needs a long-time multi-frame detection which makes it difficult to apply to complex scenes.In order to solve the problems faced by existing imaging technologies under low light level,such as limited field of view,limited resolution,limited imaging distance,limited number of photons and limited recognition ability,this paper focuses on how to use and optimize the single-photon detection ghost imaging system to make an important breakthrough in photon efficiency and imaging quality.We have conducted many researches on theories,algorithms and experimental schemes about photon-limited ghost imaging under single-photon detection.The innovative and breakthrough results are as follows:1.Build experimental platform for ghost imaging under single-photon detection:We apply time-correlated single-photon detection technology to ghost imaging,and combine new data processing methods and imaging algorithm to realize low-light imaging with ultra-high photon efficiency.We set up the indoor and a 100-kilometer far-field experimental platforms and achieved three-dimensional target recovery with 0.01 photon detection per pixel and 5d B contrast-to-noise ratio(CNR).2.Using the single-bit detection characteristics of the single-photon detector to improve the system efficiency:we estimate the target information from single-pulse measurements,so the empty redundant pulses in the existing measurement can be omitted,greatly shortening the detection time and light source energy.At the same time,keeping the total energy of the light source unchanged,we can increase the pulse frequency(that is,the measurement frequency)to reduce the energy of a single pulse,so as to adapt to different application scenarios3.Propose the first-photon ghost imaging algorithm:We proposed the first photon ghost imaging algorithm based on the Poisson detection model and the ghost imaging structure.The arrival time of the first photon detected in each frame is used to estimate the intensity,and the characteristics of compression sampling in ghost imaing are used to realize imaging with less than 1 photon detection per pixel.After that,the fast first-photon ghost imaging(FFPGI)and single-pulse single-photon single-pixel imaging(SP~3I)algorithms were proposed as the evolution and improvement.We also combined with existing gradient filtering and machine learning algorithms to achieve high photon efficiency image reconstruction and recognition.4.Establish a theoretical model for imaging quality analysis:We establish a theoreti-cal model of single-photon detection ghost imaging under the single-photon Poisson detection model,derive the relationship between imaging quality parameters and imaging system vari-ables,and give expressions for spatial resolution,image signal-to-noise ratio,contrast expres-sions and the photon efficiency,and theoretically get the relationship between photon efficiency and image signal-to-noise ratio.We verified the theoretical results with experiments,and the results show that the photon efficiency and image quality parameters are related to system pa-rameters such as modulation matrix sparsity,target sparsity,optical source intensity,detection frames,etc.Our work lays the foundation for the analysis and optimization of the corresponding system.5.Propose a fast spatial light modulation scheme:The refresh rate of spatial light modu-lator(SLM)has become a bottleneck that limits the imaging time and efficiency of the system.By designing and experimentally testing the spatial light modulator based on the acousto-optic modulator,we achieved a thousand times faster spatial phase and intensity modulation than the existing SLMs.We used this modulator in single-pixel ghost imaging experiments,which has greatly sped up the imaging.