Development Of Probe - Type Refractive Index Measuring Instrument

Liquid refractive index is an important parameter of liquid, there are many connections between refractive index and other factors, such as the density of the fluid, electromagnetic properties, concentration, composition, ambient temperature,so they can be measured by the change of liquid refractive index. The methods of refractive index measurement is divided into geometric measurement and waving measurement. The geometric measurement method is based on the law of refraction or reflection, it is relatively simple, and most of the existing measuring instruments are based on it. Waving method of measuring liquid refractive index is to utilize the wave nature of light, and the refractive index was measured by intervene or diffraction with the liquid, this method experiment device generally is more complicated, and the operation is complex, so the usage in the practical application is relatively narrow.The traditional production of refractive index measurement in the laboratory and industry have some limitations, the waving method needs a large number of quantity, it is not apply to the rare and precious liquid and easily affected by external factors, it is not easy to achieve on-line detection in industrial production; The geometrical optics measuring instrument is the most common refractometer, its operation is relatively complicated, and need testing samples, it is not suitable for the measurement in a close system, and it is poor on real-time performance. In order to solve these problems, we design a new type liquid refractive index measuring sensor device, and the actual measurement result of several kinds of liquids is ideal. During debugging assembly, the important parts of the whole device were compared by us in the selection, and some parts are made in the laboratory, there are including the choice of light source on the comparison of varieties traditional light sources, we fund that the green light conductor laser device is the best choice; we compared the quality of several concentrating equipments, such as convex lens, concave mirrors and self-focusing lens, the result is not very ideal, and finally we made a light concentrating equipments; Respectively, the selection of optical glass in different type and degree frosted glass was done, we use the homemade imaging sensor glass; Pictures were collected by CCD or CMOS, finally we choose Microsoft’s H-D3000cameras filming because of the practical factors such as the cost; The Image processing contain calibration and the pixel calculation, the calibration method has two kinds, one is material selection and the other one is using the known refractive index liquid, the later calibration method is more accurate, the calculation of pixels is based on the relationship between light intensity and pixels, especially on the edge color scanning, and the accuracy of measurement will have a big improvement. This device has several bright points, such as simple structure, convenient operation, low requirement for operating environment, without closing space, strong anti-jamming capability, it is relatively convenient in industrial production measurement and analysis,it can display the dynamic change of liquid refractive index on real-time; finally this device realized the purpose of online detection in industrial production, overcome the disadvantages of tedious work of samples testing and affected the production process in real time, it has broad applications and practical values in the industrial production.The main work of this article1. Several measuring methods and applications of refractive index of liquid were given, as well as the existing variety of refractive index sensor, analyses their advantages and disadvantages.2. Designing and describing the basic structure of a refractive index measuring instrument which is based on the principle of shading effect, and the prototype was made in the laboratory.3. The detailed description of this device is given, including spray paint glass manufacturing, the homemade light concentrating equipment, as well as the design of image acquisition and image processing system.