Abstract
Abstract. There are many intertidal zones and island reefs in the coastal area, the traditional shipborne acoustic measurement method is extremely inefficient, so the coastal area three-dimensional integrated measurement has always been a difficult point in the field of remote sensing. Because the sea blue-green light window has good transparency and the laser point cloud data can quickly and accurately distinguish the characteristics of shallow sea water topography. At present, the most effective detection method for coastal areas in the world is the airborne dual-frequency laser radar detection technology, which has high measurement rate and wide coverage. The laser outputs both 1064nm and 532nm dual-wavelength laser, 1064nm laser forms sea surface echo, and 532nm laser penetrates sea water to form shallow sea and deep sea echo. However, during the propagation of seawater, the number of photon scattering increases with the increase of water depth, which will cause the attenuation of the echo signal. As a result, the detection of weak light in the large dynamic range is not high, which has been a difficult point for near-shore airborne sounding. To solve this problem, we designed a split-field, three-channel optical receiving system. The ZEMAX simulation results show that the dual-channel laser radar three-channel receiving optical system effectively reduces the optical crosstalk between the optical components and the channels, and achieves energy harvesting in different water depth channels. The structure dynamically compresses the photoelectric signal and improves the signal to noise ratio.
Highlights
The airborne dual-frequency lidar detection technology uses this transmission window to emit blue-green band lasers and 1064 nm infrared light from the aerial platform to the seawater, and measures the depth of the seawater according to the time difference of the laser reflection on the sea surface and the sea floor(Guo 2013) .The use of high repetitive frequency lasers to extract dynamic large-scale weak optical signals, to achieve the identification of weak optical signals, but can not meet the accuracy of water and land data acquisition
The device adopts a method of splitting the beam and dividing the field of view, and the 1064 nm echo is reflected by the dichroic beam splitter into the sea channel
The 532 nm echo of the small field of view is reflected into the shallow sea channel and is in the single quadrant PMT
Summary
The coast has many intertidal zones and island reefs. The traditional detection method uses multi-beam detection technology to achieve shallow sea mapping by surface scanning, but in the actual application process, the blind zone has many dead angles and low efficiency (Yang 2011(1)). The airborne dual-frequency lidar detection technology uses this transmission window to emit blue-green band lasers and 1064 nm infrared light from the aerial platform to the seawater, and measures the depth of the seawater according to the time difference of the laser reflection on the sea surface and the sea floor(Guo 2013) .The use of high repetitive frequency lasers to extract dynamic large-scale weak optical signals, to achieve the identification of weak optical signals, but can not meet the accuracy of water and land data acquisition. As the water depth increases, the number of photon scattering increases, and the more photons that eventually exceed the range of the received field of view, the greater the effect on the laser pulse echo signal. Considering the requirements for miniaturization and light weight of the product, the field of view of the Cassegrain optical system cannot be made too large, and the receiving field of the deep water channel takes 50 mrad
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