INTERFEROMETRY METHOD USING TWO WAVELENGTHS FOR ANGULAR DISPLACEMENT MEASUREMENT

Abstract

At the present time moire interferometry is commonly used for control of objects attitude position and their geometric shape. Method of angular displacement measurement using moire is offered in this research. The method is based on use of digital moire fringes which are formed by subtraction of interference patterns intensity. Laser source with different wavelengths were used for creation of these interference patterns. Moire fringes are formed from fringe patterns by means of Hilbert transform. Using moire fringes result precision and sensitivity increase because small shift of the interference fringes result large shift of moire fringes. Consequently, there is a possibility to make measurement with submicron resolution if conversion coefficient of the moire pattern has large value. Experimental setup using the digital moire pattern for angular measurement was made and tested. It has displayed feasibility of the offered method. Measurement error of experimental setup is equal to 0.8% in the range ± 2.5 ' then laser sources with wavelength 632 nm and 532 nm are used. For accuracy increasing laser sources with wavelength difference 5-10 nm are necessary.