LiDAR has become a key technology for autonomous driving. However, with the popularization of LiDAR, the laser signals emitted by multiple LiDAR at the same time in road environment will cause mutual interference, also known as crosstalk. Overcoming crosstalk has been a challenge that must be faced. Firstly, this paper analyzes the photon arrival time histogram characteristics of Time-Correlated Single Photon Counting LiDAR in the case of crosstalk. Then, the basic principle of interference suppression methods based on Pseudo-Random Pulse Position Modulation is introduced. Finally, we use interference suppression ratios to analyze the interference suppression effectiveness under different cumulative cycles and different random dynamic ranges. The simulation results show that when the laser repetition rates of the two LiDAR are the same, the larger the cumulative cycle number, the greater the interference suppression ratio; With the same cumulative number of cycles, the larger the random dynamic range of pulse position modulation, the greater the interference suppression ratio.
With the increasing frequency of space activities, space satellite systems are fully involved in joint operations. Numerous imaging and reconnaissance optical imaging satellite systems are arduous to evade and warn actively, and passive protection is cumbersome to implement. Therefore, developing new reflective imaging satellite reconnaissance systems and materials is particularly important. In countering optical imaging satellites, active jamming materials can form aerosol jamming smoke screens on the action path of the target to be protected. The jamming signal transmitted in all directions can suppress the imaging accuracy of the optical satellite to the target and form an effective deception. CsPbBr3 perovskite quantum dots show great potential in anti-detection and active jamming due to their high absorption and emission efficiency, size-dependent excellent photoelectric properties, and low exciton binding energy. However, it is still challenging to synthesize CsPbBr3 nanosheets with wide band emission for active interference. This paper uses the template induction method to regulate the morphology of the CsPbBr3 crystal. CsPbBr3 nanospheres and nanocubes were synthesized by the recrystallization method. CsPbBr3 nanospheres were induced to self-assemble on CsPbBr3 nanocubes to synthesize CsPbBr3 nanosheets with wideband emissions. It maintained a strong quantum confinement effect, a simple synthesis process, high stability, and excellent photoelectric performance. The induced synthesis process was recorded by field emission transmission electron microscope. The nanosheets were face-to-face, close, and perpendicular to the carbon film substrate. The balance of van der Waals force and elastic repulsion force between ligands under thermodynamics determines the lamellar spacing of nanosheets in the self-assembled state. UV-Vi's absorption spectra further proved the change of morphology during self-assembly. The nanosheets were also very stable under 200kV electron beam bombardment. The fast Fourier transform patterns of the nanosheet demonstrated that the assembled NCs were orthogonal, with no crystal transition in the assembly process. X-ray photoelectron spectroscopy showed that the crystal is composed of CS, Pb, and Br elements. The assembly process did not change the ion state and element composition on the surface and inside. The photoluminescence spectrum showed that the emission wavelength of the nanosheets was 493nm, and a uniformly tunable emission wavelength was generated between 468-506nm. The disappearance of the tail band in the long wavelength region demonstrated that the defects in the self-assembly process were significantly reduced. The quantum yield increased from 65.78% to 67.33%, which directly confirmed that the large absorption cross section and defect reduction brought by the unique sheet structure were conducive to the conversion of excitation light in the active interference process. This paper provides an idea for the theoretical study of morphology regulation of perovskite nanocrystals and other system nanocrystals. Most importantly, the high coincidence between the steady-state fluorescence spectrum and the response curve of the Si-based CCD attested that quantum dots could be used to interfere with the optical imaging system based on CCD actively.
In order to remove or at least significantly reduce the interference caused by incident laser, the detection for the laser spot in infrared image is indispensable. According to the shape and gray distribution characteristics of laser spots, the laser spot is identified and located in the infrared image by using the SIFT feature matching algorithm. In order to verify the effectiveness of this method, interference laser irradiation experiments with different laser powers are carried out. The experimental results show that this method can accurately detect laser spots in infrared images, and can adapt to different sizes of laser spots.
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