Study On The Method Of Measuring Light Pollution At Sea With Color CCD Camera

With the development of lighting technology,many coastal cities have illuminated night scenes.However,due to the phenomenon of disordered lighting and excessive development and abuse of some coastal lighting projects,the light pollution has invaded the light environment of ships navigating at night as well as the safety of navigation by interfering the identifiability of the signal lights in the waters around the ship and the normal lookout of the officer.Besides,there are some other sources of light pollution on the sea,such as the lure lights of fishing vessels,the operational lighting of offshore oil fields,etc.In order to monitor the light pollution level of the marine environment,there need to make the light pollution quantitative by the related measurement tool,nevertheless,the traditional measurement tools have certain limitations during the measuring process.So in order to overcome the limitations of traditional measurement tools and better measure the marine light environmental parameters,a method for studying marine light pollution based on digital images of color CCD cameras is proposed.The contents of main work of the thesis as follows:(1)In order to reasonably analyze the measurement indicators required for the evaluation of marine light pollution,a theoretical analysis is carried out from the concepts and characteristics of marine light pollution,the influence mechanism of the visual performance of the ship officers,and photometry and chromatics.Moreover,it is concluded that the brightness and chromaticity are the important measurement indicators for evaluating recognizability and glare of signals.(2)Based on the CCD camera-imaging model,the principle of measuring brightness,azimuth angle,solid angle and illuminance of the camera is analyzed,and the parameters of RGB image,exposure time,aperture F and gray value needed to extract CCD camera image are obtained.(3)The calibration experiment is used to calibrate the color and brightness of the CCD camera,and the RGB correction formula and brightness calculation formula based on the digital image were obtained.In addition,the accuracy analysis of the brightness formula is performed.The results show that the linear fit is 0.9914 and the relative error of brightness measurement is within±5%.(4)Using the obtained color RGB correction formula and brightness formula,the light pollution generated by the lightening project of the Nanjing Yangtze River Bridge is measured and evaluated from the perspective of the ship officer:the brightness contrast the visual ergonomics of each buoy in the bridge area meets the standard requirement of 1.3.And the chromaticity value of the mixed light of floating light and background light at different measuring points are within the corresponding chromaticity range of the light specified in GB12708-91(The color of light signal on aids to navigation),which is in accordance with the standard chromaticity requirements of the beacon light.The brightness of the ship's light of the night navigation in the water area is within the range of 42.16cd/m2?94.19 cd/m2,which does not affect the recognition of other ships.It should be distinguished o the mast and tail lights of ships sailing nearby the water#1 light of 6#and 8#.The glare GR value is less than 50,which means that the comfort level is weaker than "uncomfortable".In summary,the image processing technology based on the color CCD camera in this paper is feasible for the measurement of marine light pollution and can provide a monitoring method for the prevention and control of marine light pollution.