Error estimation of 3D reconstruction in 3D digital image correlation

Abstract

Three-dimensional digital image correlation (3D-DIC) is widely used in various measurement fields. Once a DIC setup is established, different parameters, such as lens focal length, pixel size, stereo angle, and working distance, are easy to know or measure; the range of the matching error is generally 0.01–0.02 pixels. It would be very convenient if the measurement error could be estimated based on the parameters above without performing the entire DIC calculation process. In this study, a numerical simulation was conducted to study the variation of the 3D reconstruction error with the stereo angle in different measurement areas. It was found that the error of the center point was closely related to the error of the full field. Therefore, using simple parameters to describe the 3D reconstruction error of the center point is of great significance for estimating the overall error of a DIC system. The general solution of the 3D reconstruction equation was simplified on the premise that high order terms of pixel coordinates could be omitted. The derived error estimation formulas had a simple form and described the 3D reconstruction error of the center point in three directions. Through a set of static experiments, the 3D reconstruction error of a planar object under different stereo angles (from 10° to 120°) was studied. The matching error was calculated by a 2D-DIC software and inserted into the proposed formulas to obtain the estimated error. The estimated error was compared with the results of a 3D-DIC software, and the effectiveness of the proposed method was verified.