Research On Hardware Of Automatic Measurement System Of Transmissivity And Reflectivity

Automatic transmissivity and reflectivity measurement with high accuracy and high stability is very important while studying coating technics. A set of instrument, measuring transmissivity and reflectivity automatically in the angle range from 5°to 80°, is introduced. Its absolute accuracy and stability were both better than 1.0E-4, while measuring the samples whose transmissivity and reflectivity are less than 50% .Firstly, the principle of the automatic instrument is analyzed and compared with DF transmissivity and reflectivity measurer.Secondly, the design of optical system, preamplifier and mechanism, as well as the selection of Silicon Solar Cell, are all introduced in the paper. According to the theoretic model of Silicon Solar Cell and preamplifier, the transform errors and noise are analyzed. The wiring between preamplifier and data acquisition card is analyzed in detail. The matching problem of preamplifier and the different measuring method of data acquisition is also discussed emphatically. After analyzing the cause and influence of crosstalk of data acquisition, the corresponding solution is presented.Thirdly, the influence of sample's orientation is analyzed. Contraposing the three positional errors of sample, one method of coaxial adjustment is presented by using the centering of quadrantal Silicon Solar Cell. Then, an objective criterion is built.Lastly, errors of the measurement are analyzed. The reflectivity of standard sample is measured to evaluate the absolute accuracy and stability, indicating that the instrument can meet the requirements of application.