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Schematic of a system based on DTDM: FPGA, field programmable gate array; TL, transmitting lens; RL, receiving lens; APD, Avalanche photo diode; TD, time delayer; and SSM, signal sampling module.
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A ranging method based on the differential time domain method (DTDM) is proposed in order to improve ranging accuracy and the range of active measurement based on peak discriminator (PD). We develop mathematical models and deduce that zero-crossing sensitivity is an important factor, which affects the ranging error of DTDM. Additionally, zero-cross...
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Citations
... In D-ToF LiDAR systems, semiconductor photodetectors are commonly employed due to their small size, low cost, and insensitivity to magnetic fields. Among these, linear and Geigermode avalanche photodiodes (APDs) are the most commonly used types [5][6][7][8]. ...
Due to its numerous advantages such as high gain and low operating bias, the silicon photomultiplier (SiPM) holds great potential in LiDAR applications. However, it is more jittery at weak echoes and more sensitive to ambient light, making its ranging performance at low signal-to-noise ratios (SNRs) severely deteriorated. To enhance the ranging performance of SiPM LiDAR under low SNR, a novel echo processing method, to the best of our knowledge, was proposed based on the statistical property of SiPM responses and validated under relatively intensive sunlight ( $\gt \!50\; {\rm klx}$ > 50 k l x ) using a self-developed LiDAR system. At the same time, laser pulse width modulation and multi-pulse laser emission are used in ranging experiments to maximize the advantages of this method. It has shown that increasing the laser pulse width within a certain range can improve ranging performance, and that emitting multiple laser pulses improves ranging performance more significantly. Utilizing a three-pulse laser with a peak power of only 3.2 W, a target 122 m away was ranged with a precision of 6.53 cm with only five accumulations.
... The main ranging methods can be divided into time identification methods based on the time-to-digital converter (TDC) and waveform centroid determination. When the environment and the target are more complex, the amplitude of the echo pulse changes greatly, and the TDC technology that only relies on the threshold to achieve time measurement will no longer be suitable, leading to a large drift error [5][6][7][8]. The full waveform ranging method is the most effective method to solve this problem, mainly including the waveform centroid and Gaussian fitting methods. ...
This paper proposes an energy-barycenter-based waveform centroid algorithm (EWCA) for a high-precision Lidar ranging system. Firstly, the emission and echo pulse models of the pulse Lidar ranging system are established. Secondly, based on analyzing the merits and demerits of the conventional waveform centroid algorithm (CWCA) and intensity-weighted waveform centroid discrimination algorithm (IWCD). Moreover, combined with the characteristics of the energy moment distribution, the adaptive strategy is used to select the point with the higher signal as the calculation time series, and we proposed the EWCA to calculate the timing moment. Finally, we compared EWCA with CWCA and IWCD through simulation and actual experiments. The experimental simulation results show EWCA has higher accuracy and robustness than the comparison algorithm with different SNR. EWCA can achieve an average error of 0.1235 ns, a standard deviation of 0.0848 ns, and variance of 0.0072 ns at an SNR of 5 dB. At the same time, the Lidar ranging system is established to compare these methods further, and the ranging error of the proposed method can be within 20 mm when the measured distance is 40 m. This method has higher timing accuracy and application range, which has the potential to handle further ranging tasks.
... We developed a mathematical model and concluded that the zero crossing sensitivity is an important factor affecting the DTDM ranging error. In addition, the zero crossing sensitivity is determined by the delay time [4]. Lee et al. need to conduct prospective studies using standardized injury and exposure measures to consolidate our understanding of the incidence of injuries and risk factors related to musculoskel-etal injuries among preprofessional dancers. ...
Multifeature data integration technology uses computer technology to automatically analyze and process the observation data obtained by multiple sensors in chronological order according to a defined threshold. And it can complete the necessary decision-making and evaluation tasks in the data processing process. This article is aimed at studying the effect of multifeature information fusion on dance movement recognition technology. The article mainly adopts the principle of structural risk mitigation and the image thresholding method to effectively obtain the binarized image of the dancer’s moving image, so as to select an appropriate threshold, use the threshold as its distinguishing standard, and then segment the pixel threshold. The method of multifeature information fusion and dance movement recognition technology is introduced. The performance of image classification algorithms is compared, and the experiment of dance video movement, human behavior recognition, and gait phase recognition are carried out. The experimental data show that in the power identification algorithm of this article, when the peak value is 1000 bits, the experimental data is 256 bits, the analysis and comparison data is 457 bits, and the experimental environment is 812 bits. When the peak value is 2000 bits, the experimental data is 451 bits, the analysis and comparison data is 635 bits, and the experimental environment is 947 bits. The experimental data is 562 bits, the analysis and comparison data is 546 bits, and the experimental environment is 774 bits. The experimental results show that the dance action recognition technique based on multifeature information fusion is studied well.
... Lidar is a significant technology for capturing 3D information and has been widely used in a multitude of fields, such as terrain mapping, building virtual environments, urban modeling, target recognition and car navigation [1][2][3][4]. Among the various lidar systems, the streak tube imaging lidar (STIL) has the advantages of the deep imaging field of view, high frame rate and high range accuracy, and is considered one of the most promising 3D lidar imaging systems [5]. ...
We improve the system of multi-slit streak tube imaging lidar (MS-STIL) for occluded target detection. To solve the contradiction between high range resolution and deep depth of field, a fiber-optic beam, called ‘beam shunting’, is designed. In addition, we combine the deep-learning-based image inpainting algorithm with the MS-STIL to solve the problem of ineffective imaging when the target is obscured by a large area. Finally, the results of the simulated contrast experiments show that the range resolution is increased from 0.4 m to 0.1 m, and the new system is effective in detecting occluded targets.
... It can be seen fromFigure 3that within the range of 100 m, the range accuracy of the spherical target is within 40 m, the minimum accuracy is 3.6 mm, and the accuracy is at 60 m, 80 m, and 100 m. They are 4.8 mm, 6.3 mm, and 7.7 mm respectively[6]. ...
The accuracy of terrestrial 3D laser scanners is mainly determined by the accuracy of ranging and angle measurement. Therefore, the research of horizontal angle accuracy is very important. The current construction industry can develop at the fastest speed because of the advent of many advanced science and technology research and development. The rational application of these science and technology to the construction industry can intuitively display the internal structure and external shape of the building. In front of people, it effectively guarantees the country's economic benefits and the people's property safety. The article studies the influence of distance, incident angle and target color on the accuracy of the scanner during measurement. Using the plane fitting method to analyse the accuracy, a qualitative analysis conclusion is drawn that as t he distance increases, the angle of incidence increases, which will cause the measurement accuracy of the ground 3D laser scanner to decrease.
... Kurtti et al. proposed a unipolar to bipolar based timing discriminator and then performed zero-crossing detection for time discrimination [15]. Cao et al. presented the differential time domain method (DTDM) based on peak discrimination to improve the accuracy [16]. ...
In the pulsed light time-of-flight (ToF) measurement, the timing point generated in the receiver channel is very important to the measurement accuracy. Therefore, a differential hysteresis timing discrimination method is proposed to generate timing points of the receiver channel. This method is based on utilizing the unbalanced characteristics of the fully differential operational amplifier circuit as well as introducing extra hysteresis levels to achieve the stable generation of timing points. With this method, fewer circuit components are consumed and the dynamic range of the receiver channel is not limited by its linear range. The experiments demonstrate that a receiver channel applying the proposed discrimination reaches better single shot accuracy compared to that using leading-edge timing discrimination. This method is also suitable for the timing walk error compensation by means of pulse width. Finally, these results verify the effectiveness of the proposed method in pulsed light ToF measurement.
... To the best of our knowledge, autofocusing method can be divided into two categories, namely active and passive autofocusing methods. Active autofocusing method employs a launch equipment to actively emit laser light or waves (infrared or ultrasound) [10][11][12]. Although high autofocusing efficiency is obtained, the remarkable drawback of this method is low autofocusing accuracy [13]. ...
... Although the reflected laser pulse is a Gaussian function in general, the actual signal returned is not precisely known since the target scene or object of interest is unknown. In this context, peak estimator and leading edge detection are clearly not suitable due to the noisy nature of the reflected laser signal recorded in the image pixels [11]. As for matched filter and maximum likelihood method, a reference signal or model needs to be assumed that is not feasible in some cases. ...
Accuracy is an important measure of system performance and remains a challenge in 3D range gated reconstruction despite the advancement in laser and sensor technology. The weighted average model that is commonly used for range estimation is heavily influenced by the intensity variation due to various factors. Accuracy improvement in term of range estimation is therefore important to fully optimise the system performance. In this paper, a 3D range gated reconstruction model is derived based on the operating principles of range gated imaging and time slicing reconstruction, fundamental of radiant energy, Laser Detection And Ranging (LADAR), and Bidirectional Reflection Distribution Function (BRDF). Accordingly, a new range estimation model is proposed to alleviate the effects induced by distance, target reflection, and range distortion. From the experimental results, the proposed model outperforms the conventional weighted average model to improve the range estimation for better 3D reconstruction. The outcome demonstrated is of interest to various laser ranging applications and can be a reference for future works.
... In this study, we employ a laser ranging finder [20] to combine the advantages of active and passive autofocusing techniques to improve the performance of autofocusing. This finder was developed by our group to obtain a reasonable initial position of the lens during the coarse autofocusing stage. ...
A novel autofocusing method combining active and passive techniques is proposed to improve autofocusing performance. The proposed method is divided into coarse and fine autofocusing stages. First, a laser ranging finder viewed as the active technique is used to obtain a reasonable initial position of the compensating lens group during the coarse autofocusing stage. Second, a retina-like sampling method is used to decrease the volume of processing data during the fine autofocusing stage. We developed a prototype and performed comparative experiments using different targets based on the proposed method and the traditional passive method (TPM). Under optical power of 9×, the TPM consumed 2.5 s, while the proposed method performed at 1.3 s. The comparative experiments also showed that the proposed method exhibited a better anti-interference property than the traditional method.
... cars and planes). Therefore, extreme situations of strong or weak intensity will result in poor performances on measuring dynamic ranges [16]. Studying the position between the RL and APD is important and beneficial to improve the performances of TDPELP-based systems. ...
We theoretically and experimentally examined the effects of the different positions between receiving lens (RL) and detector, namely, defocus, off-axis, and tilt, on the time-domain pulsed echo laser profile (TDPELP). Results show that distortions including saturation and broadening of TDPELP are obtained, regardless of the position between RL and detector. Thus, we adjust the focal length of RL to successfully obtain an optimal TDPELP using tunable lens under extreme situations, such as too strong or too weak intensity of the TDPELP.
