High-resolution non-confocal non-line-of-sight imaging based on spherical-slice transform from spatial and temporal frequency to space and time.

Current non-confocal non-line-of-sight (NLOS) imaging faces the problems of low resolution and limited scene adaptability. We propose a non-confocal NLOS imaging method based on spherical-slice transform from spatial and temporal frequency to space and time. Simulation and experimental results show that the proposed method has high-resolution reconstruction without artifact interference, shape distortion, and position offset. Furthermore, it has strong scene adaptability. After GPU acceleration, the reconstruction time of the proposed method can be reduced to several hundred milliseconds for the PF32 photon array camera with 32 × 32 detection units. In the future, the proposed method has great potential for application in real-time NLOS imaging systems.

Passive localization and reconstruction of multiple non-line-of-sight objects in a scene with a large visible transmissive window.

Passive non-line-of-sight imaging methods have been demonstrated to be capable of reconstructing images of hidden objects. However, current passive non-line-of-sight imaging methods have performance limitations due to the requirements of an occluder and aliasing between multiple objects. In this paper, we propose a method for passive localization and reconstruction of multiple non-line-of-sight objects in a scene with a large visible transmissive window. The analysis of the transport matrix revealed that more redundant information is acquired in a scene with a window than that with an occluder, which makes the image reconstruction more difficult. We utilized the projection operator and residual theory to separate the reconstruction equation of multiple objects into the independent equations of the located objects that can be reconstructed independently by TVAL3 and Split-Bregman algorithms, which greatly reduces the computational complexity of the reconstruction. Our method lays the foundation for multiple objects reconstruction in complex non-line-of-sight scenes.

Smartphone Use, Technology Affordance for Healthcare and Elders' Life Satisfaction.

Previous studies have examined how smartphones influence the life satisfaction of the elderly, but the existence of conflicting conclusions suggests the existence of a "black box". In this study, using a survey from 941 elders, we examine whether smartphone use can improve life satisfaction of the elders by inducing emotional affordance offered by social networking Apps and functional affordance offered by healthcare system Apps. It is found that both emotional affordance and functional affordance acted as intermediating variables between the use of smartphone and elders' life satisfaction. In addition, it is founded that living arrangement with adult children moderates the positive impact of smartphone use on functional affordance, but there was no such moderating effect on emotional affordance. This study offers insights about how digital healthcare innovation will be applied to increase well-being of elders by applying framework of selective optimization with compensation.

Family Business Internationalization in Paradox: Effects of Socioemotional Wealth and Entrepreneurial Spirit.

This study investigates the internationalization (i. e., foreign investment) of small family businesses by classifying the effects of external socioemotional wealth (family reputation) vs. internal socioemotional wealth (family involvement). The study involved 2,704 small family businesses in China, and the results support the hypothesis that family reputation has a positive effect on internationalization, while family involvement has a negative effect on internationalization. Moreover, entrepreneurial spirit reinforces the positive effect of family reputation on internationalization and enhances the negative relationship between family involvement and internationalization. This study contributes by examining the effect of entrepreneurial spirit as a potential balancing factor for the paradoxical influence of internal vs. external socioemotional wealth.

Method for the generation of microwave frequency combs based on a Vernier optoelectronic feedback loop.

Microwave frequency combs (MFCs) with flexible tunability and prominent phase noise performance are of importance to many applications, including consumer electronic product, fundamental research and military defence. It is difficult for traditional electronic signal sources to meet the imperative demand in terms of high frequency scale, due to a challenging problem of deteriorating phase noise performance with increasing frequency. Photonics-assisted methods have capacity of implementing the generation of microwave signals with high frequency and low phase noise. Here we report a novel photonics-assisted MFC generation method utilizing an optoelectronic feedback loop with a Vernier configuration. The proposed MFC generation system features self-sustained oscillation, inherent multiple-mode oscillation and low phase noise level. In the proof-of-principle experiment, the MFC generation system based on a dual-path Vernier optoelectronic feedback loop is demonstrated, and the comb spacing tuning from 3.072 to 4.710 GHz and the single sideband phase noise of -99.60 dBc/Hz at 10 kHz offset from the carrier are achieved.

Richardson-Lucy deconvolution of time histograms for high-resolution non-line-of-sight imaging based on a back-projection method.

Non-line-of-sight (NLoS) imaging is a newly developed technique with widespread applications in recent years. At present, it is difficult for NLoS imaging to achieve a high-resolution reconstruction with an existing back-projection method. We propose a novel approach based on the Richardson-Lucy deconvolution of time histograms for high-resolution NLoS imaging. In our approach, the backscattering photons from a line-of-sight scene, often regarded as adverse factors, are used favorably as priors for the deconvolution of time histograms. All deconvoluted time histograms are back projected into the space to form a high-resolution NLoS reconstruction. The simulated and experimental results with the approach demonstrated that the reconstructions of NLoS objects are indeed with high resolution, even under a relatively high noise level.

Reconstruction of multiple non-line-of-sight objects using back projection based on ellipsoid mode decomposition.

Non-line-of-sight imaging has attracted more attentions for its wide applications. Even though ultrasensitive cameras/detectors with high time-resolution are available, current back-projection methods are still powerless to acquire a satisfying reconstruction of multiple hidden objects due to severe aliasing artifacts. Here, a novel back-projection method is developed to reconstruct multiple hidden objects. Our method considers decomposing all the ellipsoids in a confidence map into several "clusters" belonging to different objects (namely "ellipsoid mode decomposition"), and then reconstructing the objects individually from their ellipsoid modes by filtering and thresholding, respectively. Importantly, the simulated and experimental results demonstrate that this method can effectively eliminate the impacts of aliasing artifacts and exhibits potential advantages in separating, locating and recovering multiple hidden objects, which might be a good base for reconstructing complex non-line-of-sight scenes.

Super-sensitive angular displacement estimation via an SU(1,1)-SU(2) hybrid interferometer.

In this paper, we propose a protocol for the estimation of angular displacement based upon orbital angular momentum and an SU(1,1)-SU(2) hybrid interferometer. This interferometer consists of an optical parametric amplifier, a beam splitter, and reflection mirrors; the balanced homodyne detection is used as the detection strategy. The results indicate that super-resolution and super-sensitivity can be achieved with an ideal scenario. Additionally, we study the effect of photon loss on resolution and sensitivity, and the robustness of our protocol is also discussed. Finally, the advantage of our protocol compared with an SU(1,1) protocol is demonstrated, and the merits of orbital angular momentum-enhanced protocol are summarized.

Recovering three-dimensional shape through a small hole using three laser scatterings.

An approach was proposed and developed to recover the 3D shape concealed in a shelter with a small hole only using three laser scatterings. This approach extends reconstruction of concealed 3D shape from "around a corner" to "through a small hole". Based on principle of rectilinear propagation of light, a simple geometric mapping tentative theoretical frame independent of scene was proposed to extract 3D information of concealed objects. Experimental setup mainly consists of a nanosecond laser and a single-photon APD, both of which are commercially available. The 3D reconstructions of three hidden objects were acquired with a resolution of centimeters.

Multipulse gate-delayed range gating imaging lidar.

We present a technique to reconstruct a higher resolution of depth map of range gating imaging lidar by applying the delays of the gates to a typical range gating lidar system during the detection of each returned laser pulse with the encoding of the returned signal. With the consequent delays of the gate, the depth of the scene is extended accordingly. A multipulse gate-delayed range gating lidar system is designed to prove the resolution improvement from 6 to 1.5 m. The unchanged peak power of the laser, the widths of the laser pulse and the sampling period result in a simple structure of the lidar system.

Salient target detection based on pseudo-Wigner-Ville distribution and Rényi entropy.

We present what we believe to be a novel method based on pseudo-Wigner-Ville distribution (PWVD) and Rényi entropy for salient targets detection. In the foundation of studying the statistical property of Rényi entropy via PWVD, the residual entropy-based saliency map of an input image can be obtained. From the saliency map, target detection is completed by the simple and convenient threshold segmentation. Experimental results demonstrate the proposed method can detect targets effectively in complex ground scenes.

Improvement of range accuracy of range-gating laser radar using the centroid method.

An improved processing approach based on the relation between range accuracy and slicing number is proposed to improve the range accuracy of range-gating laser radar. The sequence of time-slice images is segmented according to their optimal slicing number and processed in segments to achieve the range information of objects. Experimental results indicate that the slicing number has a significant impact on range accuracy, and the highest range accuracy can be achieved when the systems work with an optimal slicing number.

Gain-modulated three-dimensional active imaging with depth-independent depth accuracy.

We present a three-dimensional imaging method using a pulsed laser as a flood illuminating source and an intensified camera as the receiver with exponentially modulated gain. The depth map of a scene is obtained from two intensity images and the depth accuracy is independent of the depth of the target in the scene. We demonstrate a depth-independent depth accuracy of 0.32 m in an indoor experiment and obtain a depth map of an outdoor scene ranging from 150 to 180 m under a lower signal to noise ratio condition.

Scannerless three-dimensional imaging using a pulsed laser and an intensified charge-coupled device with linearly modulated gain.

We have developed a scannerless three-dimensional imaging approach that uses a pulsed laser to illuminate a target and an intensified charge-coupled device as the receiver with linearly modulated gain in gated time. The target range is extracted by processing an intensity image with linearly modulated gain and an intensity image with constant gain. Feasibility of the approach is demonstrated by an indoor experiment. Our prototype system can produce 256x256 pixel range images at a 20 Hz frame rate in an outdoor test. The test results indicate that range accuracy is related to the slope coefficient and initial value of the modulated gain.