In terms of public security, voice is one of the most crucial types of intelligence, and research on the remote collection of voice intelligence has substantial research ramifications and applications in fields like counterterrorism and narcotics control. Most optical remote sensing-based laser voice acquisition technologies in use today illuminate static target objects placed in a long-distance sound field using invisible infrared lasers, and then use phase demodulation to obtain vibration information of the target along the beam direction. The benefits of this technology are strong concealment, good directionality, and a long working distance. In practical, it can be difficult to find the appropriate statically positioned acoustic-excited targets in the sound field. In this work, the proposed method utilizes variational mode decomposition method to separate the characteristic modes of the multimodal vibration signals of moving targets in the sound field. Each mode is weighted, reconstructed, and merged to create the acoustically excited signal of the moving target based on the variations in amplitude and frequency bands between the moving object's macroscopic displacement signal and the vibration signal. Last but not least, the objective speech quality evaluation method of PESQ was used to assess the laser speech signal produced by the dynamic target laser speech acquisition method based on variational mode decomposition. According to the research, the standing person laser speech's PESQ score increased from 1.704 to 2.804, indicating a noticeable improvement in speech quality.
KEYWORDS: 3D image processing, 3D acquisition, Target detection, Near infrared, Night vision, Stereoscopy, Pulsed laser operation, Gated imaging, Imaging systems, Night vision systems
Traditional NIR laser night vision systems can only obtain 2D images without target range information, and are also easily affected by fog, rain, snow and foreground/background. To solve the problems above, 3D laser night vision based on range-gated imaging has been developed. This paper reviews 3D range-gated imaging advances and focuses on 3D rangeintensity correlation imaging (GRICI) due to its better real time performance and higher spatial resolution. In GRICI systems, the typical illuminator is eye-invisible pulsed semiconductor laser, and the image sensor chooses gated ICCD or ICMOS with mega pixels and ns-scaled gate time. To realize 3D night vision, two overlapped gate images with trapezoidal or triangular range-intensity profiles are grasped by synchronizing the puled laser and the gated sensor. The collapsed range is reconstructed by the range-intensity correlation algorithm, and furthermore 2D and 3D images can both be obtained at the same frame rate. We have established 3D NIR night vision systems based on triangular GRICI, and the experimental results demonstrate that 3D images realize target extraction from background and through windows or smoke. The range resolution minimum is about less than 0.2m at the range of 1km in our GRICI-NV3000, and the range maximum of 3D imaging is about 5km in our GRICI-NV6000.
Moving target detection is important for the application of target tracking and remote surveillance in active range-gated laser imaging. This technique has two operation modes based on the difference of the number of pulses per frame: stroboscopic mode with the accumulation of multiple laser pulses per frame and flash mode with a single shot of laser pulse per frame. In this paper, we have established a range-gated laser imaging system. In the system, two types of lasers with different frequency were chosen for the two modes. Electric fan and horizontal sliding track were selected as the moving targets to compare the moving blurring between two modes. Consequently, the system working in flash mode shows more excellent performance in motion blurring against stroboscopic mode. Furthermore, based on experiments and theoretical analysis, we presented the higher signal-to-noise ratio of image acquired by stroboscopic mode than flash mode in indoor and underwater environment.
KEYWORDS: 3D image processing, 3D metrology, Pulsed laser operation, Super resolution, Cameras, 3D acquisition, Imaging systems, Reconstruction algorithms, 3D modeling, Image processing
In this paper, we proposed a method of canopy reconstruction and measurement based on 3D super resolution range-gated imaging. In this method, high resolution 2D intensity images are grasped by active gate imaging, and 3D images of canopy are reconstructed by triangular-range-intensity correlation algorithm at the same time. A range-gated laser imaging system(RGLIS) is established based on 808 nm diode laser and gated intensified charge-coupled device (ICCD) camera with 1392´1040 pixels. The proof experiments have been performed for potted plants located 75m away and trees located 165m away. The experiments show it that can acquire more than 1 million points per frame, and 3D imaging has the spatial resolution about 0.3mm at the distance of 75m and the distance accuracy about 10 cm. This research is beneficial for high speed acquisition of canopy structure and non-destructive canopy measurement.
Underwater 3D range-gated imaging can extend the detection range over underwater stereo cameras, and also has great potentials in real-time high-resolution imaging than 3D laser scanning. In this paper, a triangular-range-intensity profile spatial correlation method is used for underwater 3D range-gated imaging. Different from the traditional trapezoidal method, in our method gate images have triangular range-intensity profiles. Furthermore, inter-frame correlation is used for video-rate 3D imaging. In addition, multi-pulse time delay integration is introduced to shape range-intensify profiles and realize flexible 3D SRGI. Finally, in experiments, 3D images of fish net, seaweed and balls are obtained with mm-scaled spatial and range resolution.
Three-dimensional super-resolution range-gated imaging (3D SRGI) is a new technique for high-resolution 3D sensing. Up to now, 3D SRGI has been developed with two range-intensity correlation algorithms, including trapezoidal algorithm and triangular algorithm. To obtain high depth-to-resolution ratio of 3D imaging, coding method was developed for 3D SRGI based on the trapezoidal algorithm in 2011. In this paper, we propose the range-intensity coding based on the triangular algorithm and the hybrid range-intensity coding based on the triangular and trapezoidal algorithms. The theoretical models to predict the maximum coding bin number are developed for different coding methods. In the models, the maximum coding bin number is 7 for three coding gate images under the triangular algorithm, and the maximum is extended to 16 under the hybrid algorithm. The coding examples of 7 bins and 16 bins mentioned above are also given in this paper. The comparison among the three coding methods is performed by the depth-to-resolution ratio defined as the ratio between the 3D imaging depth and the product of the range resolution and raw gate image number, and the hybrid coding method has the highest depth-to-resolution ratio. Higher depth-to-resolution ratio means better 3D imaging capability of 3D SRGI.
Three-dimensional super-resolution range-gated imaging has been developed for high-resolution 3D remote sensing with two range-intensity correlation algorithms under specific shapes of range-intensity profiles (RIP). However, pulsed lasers have a minimum pulse width which limits range resolution improvement. Here a spatial difference shaping method is proposed to break the resolution limitation. This method establishes a shaping filter, and the pre-reshaping gate images are reshaped by spatial difference and yield new gate images with the laser pulse width equivalently narrowed as half value which improves the range resolution. Furthermore, the boundary blurring caused by non-rectangular laser pulses are also eliminated.
Three-dimensional range-gated imaging is a new 3D sensing technique with higher resolution than 3D flash LIDAR,
and has great potential in realizing high-resolution real-time 3D imaging to satisfy land surface remote sensing
applications. In this paper, three existing approaches of realizing 3D range-gated LIDAR are introduced including their
advantages and disadvantages. Among them, the two methods of gain modulation and range-intensity correlation can
reconstruct a 3D scene from two gate images, which enable 3D flash imaging. We propose a 3D superresolution
range-gated flash LIDAR based on triangular algorithm of range-intensity correlation, and further present a coding
method based on triangular algorithm for high depth-to-resolution ratio. Some prototyping experiments and simulations
are demonstrated.
High-resolution real-time three-dimensional imaging is important in 3D video surveillance, robot vision, and
automatic navigation. In this paper, a three-dimensional superresolution range-gated imaging based on inter-frame
correlation is proposed to realize high-resolution real-time 3D imaging. In this method, a CCD/CMOS with a gated
image intensifier is used as image sensor, and depth information collapsed in 2D images is reconstructed by
spatial-temporal inter-frame correlation with a resolution of about 1000×1000 full-frame pixels within a frame.
Furthermore, under inter-frame correlation a 3D point cloud frame is generated at video rates corresponding to
CCD/CMOS utilized. Finally, some proof simulation experiments are demonstrated.
The range-gated laser imaging technology has become a useful technique in many applications in recent years. In
order to expand the range of imaging detection and improve the measurement range resolution of the imaging system, we
used circular step advance delay sequence for the synchronous control. And we developed a method of using dynamic
phase-shift technique in FPGA to improve the precision of the delay in the time sequence, which can make the precision
of the delay stepper between the two adjacent frames less than global clock period of the FPGA and approach the limit of
FPGA’s operating frequency. That is to say, it can equivalently increase the clock frequency. Then we can effectively
improve measurement range resolution of the imaging system. In this paper, we have studied how dynamic phase-shift
technique can be equivalent to higher clock frequency and performed some experiments. We presented the structure of
dynamic phase-shift technique used to improve the precision of delay in the synchronization control time sequence. And
the simulation and experimental results are showed in this paper. The results demonstrate that using dynamic phase-shift
technique in FPGA can make the precision of the delay between the ICCD’s trigger pulse and the laser’s trigger pulse
reach 1ns, which means the resolution of measurement range can be 0.15m theoretically. The timing control signal with
dynamic phase-shift technique designed in this paper can be widely used in range-gated imaging because of its high
timing control precision and flexible parameter setting.
We propose a surveillance photonic fence for night remote intrusion detection, especially in bad environmental
conditions. The photonic fence is established by the synchronization of a pulsed infrared laser and a gated imaging sensor.
Since the wavelength of the laser is invisible, the photonic fence is also invisible. Only when targets pass the fence, their
image information can be collected. Objects and backgrounds out of the fence are all filtered directly which decreases the
complexity of image processing about target extraction. For the fence, its location can be easily adjusted by the delay
time between the laser pulse and the gate pulse, and its thickness can be set by changing the gate time and the laser pulse
width. Furthermore, target space information can also be estimated in terms of the range information of the photonic
fence.
KEYWORDS: Picosecond phenomena, Field programmable gate arrays, 3D image processing, Stereoscopy, Signal generators, Data transmission, Phase shifts, Control systems, Pulsed laser operation, 3D acquisition
3D range-gated imaging with stepping delay is a novel technology developed in recent years. 3D timing control signal
based on delay line and logical AND gate technology is proposed innovatively in order to satisfy the distance precision
of centimeter of 3D imaging in complex background. 3D timing control signal is produced through FPGA nanosecond
timing generation module and picosecond timing adjustment module. Simulation and experiment show that the delay
precision of the timing signal designed in this paper is 150 picoseconds, and the narrowest pulse width is close to the
limitation of TTL signal (1ns level). The timing control signal designed in this paper can be widely used in 3D
range-gated imaging because of its high timing control precision, compact construction and flexible parameter setting.
Keywords: range-gated, picosecond, timing control, FPGA, delay line
We present a flash trajectory imaging technique which can directly obtain target trajectory and realize non-contact
measurement of motion parameters by range-gated imaging and time delay integration. Range-gated imaging gives the
range of targets and realizes silhouette detection which can directly extract targets from complex background and
decrease the complexity of moving target image processing. Time delay integration increases information of one single
frame of image so that one can directly gain the moving trajectory. In this paper, we have studied the algorithm about
flash trajectory imaging and performed initial experiments which successfully obtained the trajectory of a falling
badminton. Our research demonstrates that flash trajectory imaging is an effective approach to imaging target trajectory
and can give motion parameters of moving targets.
Based on the semiconductor laser whose spectral line with width is compressed to be less
than 1.2Mhz, a system was designed to measure and improve the amplitude and frequency of the
real-time microvibration with sinusoidal modulation. real-time microvibration measurement was
executed without alignment problem in the interferometry; and low-frequency disturbance of
environment could be eliminated. Suggestions were also given to consummate the system. The system
also has resistance against the low frequency disturbance of the environment.
622Mbits/s free space laser communication system is developed. IT's communication rate is 622Mbits/s. The whole system include three parts which are signal in and out circuit, laser driver and receive circuit and optical antenna. The communication principle is introduced. The experiment result shows that the transmission of data and image are satisfied with demands of design. It have a definite market value.
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