Optimization And Experiment On Seawater’s Refractive Index Measurement System

Turning to the ocean is the direction of human beings’ development today and in the future.The research of the sea is advanced by the countries all over the world totally and thoroughly,including the research of seawater.The salinity of seawater is an important parameter of the sea.The method of conductivity,which is a common way in the world,has some disadvantages.This paper used a method called the way of critical angle,which has better adaptability,to measure the salinity.This thesis is about analysis,simulation,image processing and experiments.Firstly,we introduced how to get the information of critical angle from the images,which includes superposition,wave filtering and differential.The key of this refractometer is the ability of measurement of refractive index which includes resolution and reliability.Therefore this paper simulated and optimized the optical system.Several ways to optimize this system has been proposed.Then we tested and evaluated these designs by experiments of calibration and measurement.According to the advantage and disadvantage of these systems,a design with better accuracy and stability was proposed.And then a prototype was made.Because this system will be used under the sea level,we designed a kind of waterproofed structure.After this,the author analyzed the feasibility of this refractometer with experiments of measurement.And then the corrected coefficient of temperature was proposed.According to the coefficient,we can correct the result of refractive index and get the salinity of seawater.Finally we tested the stability of this system and analyzed the deviation.We proved that the refractometer can be used to measure the salinity.