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In the thin-film thickness wideband monitoring system, an accurate measurement of the spectral intensity signal is critical to improving precision of coating. Because of electron gun, ion source and baking, vacuum chamber is a complex environment with background light. Together with the inherent noise of linear CCD and quantization noise of A/D conversion, which are main factors affecting accurate measurement of spectrum intensity. This paper uses time and frequency multi-resolution properties of wavelet transform, adaptive threshold adjustment method is designed. According to the different characteristics of signal and the random noise processed by wavelet transform in different scales, the fine adjustment factor is added when the threshold is determined, on the hand, which makes the adaptive threshold of wavelet coefficient with positive Lipschitz index decrease, this is beneficial to preserve real signals of wavelet coefficient; on the other hand, which makes the one with negative Lipschitz index increase, this is favorable to filter out noise signal. By this method, both rejecting true probability and false declaration probability are reduced, the random noise is suppressed effectively, a very good filtering result is achieved, and finally the analysis accuracy of spectrum signal and the precision of systematic decision pause are improved.

The correct monitoring of thin-film thickness is one of the main problems during the course of optical thin-film component manufacture, in recent years, the method which is spectrum intensity measurement of thin-film component for controlling thin-film thickness has been one of the most effective methods. When this method is used Chow spectrum intensity is real-time, correctly measured is critical. Compared with the conventional method which is mechanical scanning by stepper motor driving the grating of monochromator and receiving by photoelectrical multiplier tube, in structure, the author combines the grating spectrometer with the linear CCD, which makes the problem of spectrum intensity real-time measurement better solved, the result is satisfied. In this paper, the structure of system affecting the spectrum intensity measurement accuracy is analyzed, By experiment, the relative parameters are determined, the spectrum wavelength is calibrated, root-mean-square error is 0.234nm, which is up to the requirement of monitoring wavelength resolution in the course of thin-film deposition; The algorithm is used for the real-time compensation of spectrum intensity measurement data, which make the effect of CCD photoelectrical response non-uniformity and nonlinear less; By changing the integral time magnitude, the rate of signal to noise of the spectrum signal is improved, it satisfies the requirement of real-time thin film thickness control.