In recent years, with the development of laser technology, lasers have provided a new way for underwater optoelectronic detection of targets. Due to the unique spectral, temporal, and spatial characteristics of lasers, blue-green lasers have a strong ability to penetrate seawater. Therefore, using blue-green lasers as light sources can significantly increase the underwater detection distance. This article takes into account the blue-green window effect of seawater, selects a 532nm solid-state pulse laser as the active light source, and selects a gated image intensifier with a gate width of nanosecond accuracy for underwater imaging.The high-power 532nm solid-state laser mainly consists of a laser, a laser power drive unit, a temperature control unit, and a beam divergence angle control unit. The laser adopts a diode pumped Nd: YAG pulse laser, with a wavelength of 532nm and adjusTab.repetition frequency. It has switch control, laser emission control, and output Pin signal. In order to ensure the best field of view, the laser divergence angle and the imaging detector reception angle are synchronously controlled in linkage.By calculating and using numerical control to maintain the divergence angle and reception angle consistent, it meets the field of view requirements and provides technical support for underwater target detection and recognition.
At present, the strategic adjustment of global military has a common trend. With the deepening of the exploration of China's Marine, river and groundwater resources, the military demand of territorial sea sovereignty defense is becoming increasingly urgent. The realization of underwater environment survey, target detection and positioning analysis technology has become an urgent problem to be solved in underwater equipment operation in many fields. The current underwater detection technology is mainly divided into acoustic detection and optical detection. Sound detection has small underwater attenuation, wide detection range and relatively mature technology, but its imaging target identification is difficult, real-time, and is easily subject to Marine noise interference. It is difficult to fully adapt to the needs of many underwater delivery platforms and deep-sea detection operations for high resolution imaging detection, observation and positioning. The underwater photoelectric imaging technology, it has become the necessary equipment for many underwater submersible, underwater operation system and target exploration systems. The underwater laser selected circular polarization imaging system consists of selected circular polarization imaging subsystem, underwater laser radiation source, synchronous timing control subsystem, power supply, integrated display control subsystem and sealing structure. The system mainly adopts the distance selection + polarization laser imaging method, reduces the influence of backscattering on imaging quality through the underwater circular polarization laser imaging system based on distance selection, and establishes the database of the characteristics of underwater circular polarization laser imaging; on this basis, an engineering prototype is built to provide application support for target detection, identification and industrialization.
Semiconductor laser is partially coherent beam, while the beam quality factor is based on fully coherent beam. The Wigner distribution function for partially coherent beam is used to analyze the semiconductor laser beam. The Wigner distribution function contains both spatial information and spatial frequency information in the phase space. A method for measuring the Wigner distribution function of semiconductor laser is reported. The intensity distribution of the beam caustics is measured by two focusing mirrors, and the Wigner distribution function of semiconductor laser is reconstructed. Based on the reconstructed Wigner distribution function, the light intensity of semiconductor laser is simulated. The simulated data are in good agreement with the experimental data. Through the properties of Wigner distribution function, the wavefront aberration and coherence of semiconductor laser are analyzed. The wavefront of semiconductor laser is symmetrically distributed around a point, and the wavefront on the left side of the laser diode array is larger than that on the right side. Due to the temperature difference of the laser chip, the coherence on both sides of the laser diode array is better than that in the middle of the laser diode array.
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