Long range 3D imaging through atmospheric obscurants using array-based single-photon LiDAR

Range walk error correction for MPPC array-based high-precision 3D imaging

The multi-pixel photon counter (MPPC) array-based 3D imaging is a promising technology for remote sensing. However, variations in target reflectivity can introduce range walk error (RWE) during threshold discrimination, limiting imaging performance. This paper proposes an efficient RWE correction method for MPPC array, which combines threshold voltage modulation and macro-pixel linear regression. Using single-frame images obtained at four different threshold voltage, the method reduces the depth difference between high and low reflectivity regions of planar targets from 76.51 cm to 1.17 cm (98.47% reduction). Incorporating multi-frame techniques further reduces the depth difference to less than 0.69 cm. The method also demonstrates superior correction performance for non-planar targets, significantly improving 3D imaging accuracy. These results validate the effectiveness of the proposed method and enhance the robustness of MPPC array under fluctuating echo energy conditions. This provides crucial technical support for long-range detection in complex environments.

50.1 W narrow linewidth Nd:YVO4 Innoslab nanosecond amplifier at 1064 nm with high efficiency

A narrow linewidth nanosecond partially end-pumped slab (Innoslab) laser amplifier at 1064 nm has been demonstrated. A 6 W seed at a repetition rate of 10 kHz was amplified to 50.1 W with an absorbed pump power of 163 W, achieving a power stability of 0.49% over 10 min. The maximum extraction efficiency reached 28.3% at an absorbed pump power of 144 W. The beam quality factor M2 at the maximum output power was measured to be 1.31 and 1.26 in the horizontal and vertical directions, respectively. To the best of our knowledge, this study is the first report of high-efficiency amplification of nanosecond narrow linewidth lasers using a wedge-shaped dual-pass Nd:YVO4 Innoslab amplifier at a repetition rate of 10 kHz.

Large-FoV 3D imaging of single-photon LiDAR at up to 12 km

Single-photon light detection and ranging (LiDAR) has emerged as a valuable technology for active imaging applications. The growing demand for wider applications has driven advancements in measurement range, imaging resolution, and field of view (FoV). Here, we present a high-resolution, large-FoV single-photon LiDAR system capable of panoramic imaging. The system employs continuous raster scanning with a single-photon detector array to achieve rapid measurements, while timing-based pixel segmentation ensures precise data organization. A histogram-folding-based data compression and reconstruction method was developed, resulting in a two-order-of-magnitude increase in processing speed during simulations while maintaining high image reconstruction quality. The experimental results demonstrated the system's capacity for rapid, high-resolution, and large-FoV imaging, achieving a resolution of 7.2'' across a 1.6∘×2.1∘ FoV (1052 × 803 pixels) for buildings up to 12 km, all captured and processed in just 10 min. This approach has great potential for use in environmental mapping and related fields.

Advancement on target ranging and tracking by four-quadrant photon counting lidar

Single-photon lidar stands out as a promising technology for long-distance lidar applications, owing to its attributes of single-photon sensitivity and high repetition rate. Existing single-photon lidar systems typically rely on single-point scanning for positioning and tracking, necessitating intricate and precise scanning control. In pursuit of a more concise and efficient positioning, we incorporate the four-quadrant theory to articulate the signal formula of photon detection, and propose a novel single-photon four-quadrant positioning method. Our method, which includes signal preprocessing, compensation for longitudinal motion, extraction of pixel intensity, and acquisition of lateral motion, facilitates motion acquisition and positioning for targets. Through simulation calculations, we analyze and compare the effectiveness of each step of the method. With longitudinal and lateral speeds of 100 m/s and 50 m/s, respectively, the trajectory error is 1.7%, and the average speed error is 1.8%. Moreover, for various verification experiments, the trajectory errors are all below 4.2%, and the average speed errors remain under 5.4%, effectively verifying the validity of our method in acquiring the motion information and positioning of targets. It provides an excellent option for acquiring motion information and tracking small moving targets over long distances.

Development of a near-infrared single-photon 3D imaging LiDAR based on 64×64 InGaAs/InP array detector and Risley-prism scanner

A near-infrared single-photon lidar system, equipped with a 64×64 resolution array and a Risley prism scanner, has been engineered for daytime long-range and high-resolution 3D imaging. The system's detector, leveraging Geiger-mode InGaAs/InP avalanche photodiode technology, attains a single-photon detection efficiency of over 15% at the lidar's 1064 nm wavelength. This efficiency, in tandem with a narrow pulsed laser that boasts a single-pulse energy of 0.5 mJ, facilitates 3D imaging capabilities for distances reaching approximately 6 kilometers. The Risley scanner, composing two counter-rotating wedge prisms, is designed to perform scanning measurements across a 6-degree circular field-of-view. Precision calibration of the scanning angle and the beam's absolute direction was achieved using a precision dual-axis turntable and a collimator, culminating in 3D imaging with an exceptional scanning resolution of 28 arcseconds. Additionally, this work has developed a novel spatial domain local statistical filtering framework, specifically designed to separate daytime background noise photons from the signal photons, enhancing the system's imaging efficacy in varied lighting conditions. This paper showcases the advantages of array-based single-photon lidar image-side scanning technology in simultaneously achieving high resolution, a wide field-of-view, and extended detection range.

PE-RASP: range image stitching of photon-efficient imaging through reconstruction, alignment, stitching integration network based on intensity image priors

Single photon imaging integrates advanced single photon detection technology with Laser Radar (LiDAR) technology, offering heightened sensitivity and precise time measurement. This approach finds extensive applications in biological imaging, remote sensing, and non-visual field imaging. Nevertheless, current single photon LiDAR systems encounter challenges such as low spatial resolution and a limited field of view in their intensity and range images due to constraints in the imaging detector hardware. To overcome these challenges, this study introduces a novel deep learning image stitching algorithm tailored for single photon imaging. Leveraging the robust feature extraction capabilities of neural networks and the richer feature information present in intensity images, the algorithm stitches range images based on intensity image priors. This innovative approach significantly enhances the spatial resolution and imaging range of single photon LiDAR systems. Simulation and experimental results demonstrate the effectiveness of the proposed method in generating high-quality stitched single-photon intensity images, and the range images exhibit comparable high quality when stitched with prior information from the intensity images.