Implementation And Application Of Underwater Structure Surface Measurement System Of 40-camera Array

With the further development of the "Marine Age" in the 21 st century,the measurement of the appearance of underwater structures has received increasing attention from people.At present,there has been no mature technology and complete system for measuring the surface of underwater structures.People still need to spend a lot of manpower and material resources to measure the appearance of underwater structures.Therefore,this project aims to design a 40-camera array underwater measurement system to realize rapid and real-time measurement of underwater structures surface with large field-of-view and near-distance.In this paper,according to the measurement requirements of small distance and large field of view in underwater environment,a measurement scheme using camera array structure was proposed.In hardware selection,the system used 40 PAL camera modules to form the camera array,55 5050 SMD LED lamp beads to provide lighting,Matrox-Morphis-QxT image acquisition card which supports 16 channels of simultaneous acquisition,as well as Graphics workstations that support RAID technology and multiple PCI-E x4 interfaces.Large field-ofview and fast measurement of the structure appearance is realized,and at the same time the hardware basis for realizing the 40-channel real-time measurement is provided.In order to measure the surface appearance of the cylindrical structure and overcome the measurement error of the flowing water,the system designed the grouping array structure of the butterfly hollow truss.The power supply design used a 24-wire harness structure and independent lighting circuits to reduce signal attenuation and electromagnetic interference.The waterproof design adopted IP68 waterproof grade and stainless steel plate as the frame material,and designed 3 waterproof arrays with arm-supported structures to achieve waterproofing and angle adjustment of the 40 camera array.By comparing several commonly used enhancement algorithms,the multi-scale Retinex algorithm with color compensation was used for image enhancement.First,the noise interference is eliminated by operations such as the logarithmic transformation and the convolution of Gaussian functions.Then,the scale parameters and color factors are introduced to achieve the color restoration of images by weighted summation.Experiments showed that the algorithm can uniformly improve the brightness of the image,significantly reduce the blurring at the details,and effectively remove the shadows and spots in the underwater measurement environment.In software design,based on the MIL library functions,Qt multithreading technology was used to design memory buffers and mutexes,which ensures the security of threads and realizes multi-threaded synchronous image acquisition.At the same time,the man-machine interface,image processing and image display module were designed to realize synchronous acquisition and display of 40 cameras,real-time transmission and processing,as well as quick preview and storage.The system simulated the measurement environment in the laboratory and verified that this system could achieve underwater image acquisition.Finally,an actual measurement environment was set up in Zhuji,Zhejiang,and field measurements were made on the Zhuji Bridge.The measurement results show that the system can measure the appearance of underwater structures through the 40-camera array in an underwater environment,which verifies the availability of the system.