Reduction of nonlinearity error in a computerized contact interferometer via digital scale image processing

The article describes a computerized contact (vertical) interferometer developed at the Moscow State University of Technology “STANKIN” on the basis of the Uversky interferometer. This computerized interferometer having a resolution of 1 nm is designed for automatic verification of gauge blocks of 0, 1, and 2 ISO tolerance grades (from 0.1 to 100 mm). The computerization of the Uversky interferometer significantly improves verification efficiency, while introducing additional measurement error associated with digital camera aberrations. A method and an algorithm for software-aided correction of this error are proposed. This correction is realized through the digital processing of a camera image. The method is based on approximating experimental data by polynomials in one variable of different degrees. The efficiency of the method was experimentally confirmed with respect to the computerized contact Uversky interferometer. The advantages of this method include the ease of implementation in the form of a computer program and the ability to promptly scale univariate algorithms and programs for polynomials in two and three variables. The obtained results can be used to improve the accuracy of measurement software for computerized interferometers and other optomechanical measuring instruments.