Research On Underwater Blue-green Laser Imaging Technology Based On Area Block Scanning

Underwater laser imaging and underwater wireless optical communication are the research hotspots in the field of underwater optical technology.The unknown underwater environment is an important factor affecting the reliable transmission of underwater wireless optical communication systems.Therefore,it is of great significance to integrate the imaging system with the existing wireless optical communication system to detect the underwater environment and link detection.Rangegated imaging technology can effectively suppress the influence of backscattered light.However,semiconductor lasers in wireless optical communication systems cannot provide high-energy pulsed illumination light,and the image quality obtained by direct detection is poor.In this paper,the time-resolved image-enhanced IsCMOS image sensor is used as the detection device,and the semiconductor laser emitter of the underwater wireless optical communication system is reused as the lighting device.An underwater laser imaging system based on regional block scanning is proposed,designed and built.The experimental system is built to verify the experimental results under different conditions,which effectively improves the imaging performance.Finally,the paper further improves the image quality by optimizing the image set processing method.The main work of this paper includes:Firstly,an imaging scheme based on regional block scanning is proposed,which reduces the divergence angle of the pulse beam and scans the illumination in the field of view of the detector.The scanning system,scanning optical path and fusion algorithm in the system are designed,and a laser imaging system based on regional block scanning is built to solve the problem of poor image quality caused by insufficient illumination of semiconductor lasers.The experimental results show that the images obtained by small divergence angle scanning have better signal-to-noise ratio,contrast and brightness in different water turbidity environments in the range of 0-9NTU.Compared with the large divergence angle full field illumination method,the signal-to-noise ratio is increased by 7.32 dB and the contrast is increased by 5 times.Secondly,an optimization scheme for image set interception and fusion is proposed.The scheme detects and intercepts the region of interest of the original image set,and superimposes the intercepted image set to generate the result image.It solves the problem that direct fusion will superimpose part of the backscattered light in the image when the turbidity is large.In addition,median filtering is used to smooth the noise in the image,and the detection accuracy of the region of interest in the image is improved by template matching.After optimization,the noise ratio and contrast of the image signal are improved.Compared with the direct superposition fusion processing,the signal-to-noise ratio is increased by 1.41 dB and the contrast is increased by 32.94%.