The Ultra-thin Metal Strip Thickness Measurement System

Entrusted by China physics research institute, a differential white light interfering device is presented to measure the thickness of ultra-thin metal foil. Design, manufacture and debug of the hardware should be carried on after finishing the feasible demonstration of the theory. In addition, we should carry on research of the data processing algorithm and the writing of software. The main research work in this thesis are theory feasibility research, research of the data processing algorithm and demonstration of algorithm feasibility.Based on the theory of interference, the theoretical feasibility of the differential white light interference system has been demonstrated. The request has also been proposed while designing the measurement device according to calculation in the range of error permission. We can choose the experimental components and guide the installation in view of the above.A filtering and getting rid of noise method based on the wavelet theory has been proposed according to the characteristics that the differential white light interference spectrum data is composed of low frequency and high frequency components, and the frequency change is non-linear. So the low frequency data needed can be extracted. According to characteristic of algorithm. The condition of measurement has been put forward and layers of wavelet filtering have been estimated. The extreme value method when dealing with white light interference spectrum has also been modified, and with this method more accurate thickness of metal foil can be received.A new data processing method of white light interference spectrum based on the minimum mean-square deviation was proposed. This method overcomes the poor anti-noise ability of present commonly used extreme value method. The method assumes that the corresponding mean-square deviation of optical intensity is minimum when the fitting values are most close to the measured values. The dependability of this method has been verified through the numerical emulation. This method utilizes the usable measuring data after normalization to calculate the mean-square deviation with the corresponding fitting optical intensity values. The corresponding theoretical values when the mean-square deviation is minimum can be obtained by approximate method, which is the optical path difference measured actually. Experimental results indicate that not only optical path distance obtained by this method has the higher precision than the extreme value method, but also this methodimproves the anti-interference ability effectively.The algorithm based on the wavelet theory dealing with the differential white lightinterference spectrum data proposed in this thesis has been realized in the programming environments of VC ++6.0, among them wavelet filtering has called the MATLAB functions. The programs have been verified through the artificial data and actual measurement data. At the end of the thesis, the presumption perfecting this system has been proposed.