DoF-Dependent and Equal-Partition Based Lens Distortion Modeling and Calibration Method for Close-Range Photogrammetry

Abstract

Lens distortion is closely related to the spatial position of depth of field (DoF), especially in close-range photography. The accurate characterization and precise calibration of DoF-dependent distortion are very important to improve the accuracy of close-range vision measurements. In this paper, to meet the need of short-distance and small-focal-length photography, a DoF-dependent and equal-partition based lens distortion modeling and calibration method is proposed. Firstly, considering the direction along the optical axis, a DoF-dependent yet focusing-state-independent distortion model is proposed. By this method, manual adjustment of the focus and zoom rings is avoided, thus eliminating human errors. Secondly, considering the direction perpendicular to the optical axis, to solve the problem of insufficient distortion representations caused by using only one set of coefficients, a 2D-to-3D equal-increment partitioning method for lens distortion is proposed. Accurate characterization of DoF-dependent distortion is thus realized by fusing the distortion partitioning method and the DoF distortion model. Lastly, a calibration control field is designed. After extracting line segments within a partition, the de-coupling calibration of distortion parameters and other camera model parameters is realized. Experiment results shows that the maximum/average projection and angular reconstruction errors of equal-increment partition based DoF distortion model are 0.11 pixels/0.05 pixels and 0.013°/0.011°, respectively. This demonstrates the validity of the lens distortion model and calibration method proposed in this paper.

Characteristics of Deformation and Stability of Ultra-Deep Pit in Plateau Alluvial–Lacustrine Gravel Strata

“…Figure 6 shows the configuration of monitoring items at the top of the pit walls. Close-range photogrammetry technology uses images obtained from close-distancetarget photography to determine the spatial positions of manual marking points [31][32][33][34]. A FUJIFILM-XT20 non-metric camera was used in the lab-scale geophysical model test to this end.…”

Improvement of an LCD-Based Calibration Site for Reliable Focus-Dependent Camera Calibration

“…Thereafter, the extended model was modified to calibrate wider-angle and largerformat lens distortions (Fraser and Shortis, 1992). This model has been further developed and optimized for recently manufactured high-precision digital sensors and lenses (Li et al, 2020;Lu and Cai, 2020).…”

“…They are officially implemented in several photogrammetric software packages (Rahman et al, 2004;Zhang et al, 2010) and open sources for computer vision (OpenCV team, 2021). Recently, planar LCD panels displaying checker or circular patterns have been frequently utilized in relevant approaches (Han et al, 2016;Tan et al, 2017;Sels et al, 2019;Li et al, 2020). This type of calibration site can be set up on any occasion when a flat display panel is available and can provide enough luminance without requiring external lighting sources.…”