Measurement Of Two-dimensional Small Angles Based On Interference Fringes

In the precise measurement, Measuring high precision of small angle has required. As a kind of two-dimensional small angles measurement with own great potential. Two-dimensional small angles measurement. For these requirements, the core contents of this paper involve in two aspects:principle and methods of two-dimensional small measurement and measurement of 2D angular displacement and arithmetic of signal processing based on interference fringes. Main research contents and creative points in the dissertation are as follows:Two-dimensional small angles measurement is built up, based on the relation between the interference fringes shape (direction and width) and the angle contained by two lights of Michelson interferometer. Optics principle of two-dimensional small angle measurement is built up. The relational expression of the interference fringes shape (direction and width) and the angle contained by two lights of Michelson interferometer is get by mathematical modeling. Then to simulate interference with the large simulation software of Matlab.Modulating the wavelength of the laser-diode (LD) by saw tooth modulation is applied. Because of affection of the environment light, the quality of LD, the electric noise and so on,when using Si-photoelectric detector (QPD), the information of interference fringes shape cannot be got in high precision, then wave modulation method has proposed. Loading different modulation circuit (such as sine wave, STW, triangular wave and so on)at both ends of LD,the laser wave can be changed, The status of interference fringes will change from static to dynamic.Using High Speed A/D Convert Card (250K) and software to collect QPD signal, and utilizing quadrant Si-photoelectric detector (QPD) as detection device. In view of the extracted directly determine the phase measurement accuracy, this paper presents a high precision by solving two phase modulated light intensity signal algorithm.The precision of the phase-different is important in this measurement. The paper process is as follows:first, using the convolution filter, and then apply the approximation method several times, repeatedly Digital band-filter, the use of relevant high-precision strike signal phase, this algorithm greatly inhibited the effects of noise and improve the overall measurement system accuracy.Finally, error analy the measurement system, the error derived mainly from as following:1, the Wavelength of the semiconductor laser is inconsistent, wavelength influence by outside. 2, the algorithm targeted at a constant frequency spectrum, when the spectrum changes, the introduction of errors.3,wavelength modulation, the modulation of non-related signals into the error.The theory and experiment results demonstrate this method owns high precision and stability to measure minute angle. The test precision and scope respectively are 0.05" and-50"～50" caculated by experiment data.