Expanding the dynamic range of a measuring system that implements the phase triangulation method

Abstract

The article is devoted to the development of phase triangulation and structured illumination methods for measuring the geometry of objects with arbitrary light-scattering surface properties. A method for expanding the dynamic range of a measuring system that implements the phase triangulation method is proposed. The method is based on automatic adjustment of the exposure time of the photodetector, excessive collection of experimental data, and complex regression analysis. The results of experimental studies of the effectiveness of the proposed method for expanding the dynamic range of the measuring system are presented. It is shown that the classical approach to image interpretation using a photodetector with a fi xed exposure duration almost always leads to a high level of error over the entire range of light-scattering properties of the surface. For low exposure values, there is an increase in the measurement error in the region of the dark surface, since the signal level there turns out to be signifi cantly weaker than for the bright regions of the measured surface. For large exposure values, an increase in the error is observed when measuring the bright area of the measured surface, since the signal is outside the dynamic range of the photodetector. The proposed method of image interpretation with an extended range of the measuring system demonstrates an error level less than or comparable to the results of image interpretation with a fi xed exposure for all measured light-scattering properties of the surface. The proposed method makes it possible to perform automated measurements without additional optimization of the photodetector parameters for the light-scattering properties of the surface of the measured object.