Characterization of smartphone lens distortion and displacement measurement based on sampling moiré method

Deformation monitoring of structures such as engine shafts and bridges is an important method for structural health monitoring. Currently, commonly used deformation measurement methods are based on image processing with industrial or DSLR cameras, which present challenges such as the inconvenience of carrying the imaging equipment. Therefore, this study innovatively proposes the use of mobile phones as an alternative image acquisition device. To explore the feasibility of using mobile phone images for deformation measurement, this study employs the sampling moiré method to measure lens distortion in mobile phones. Two-dimensional grating images captured by mobile phone lenses were analyzed in combination with a standard grating to measure and assess the distribution characteristics of normal and shear strain for different phone lenses. Based on these characteristics, phone lenses with lower distortion, along with appropriate magnification and acquisition regions, were selected for displacement measurement. The resulting measurement accuracy reached ±0.7 %, demonstrating that the rear camera of the Honor 70 mobile phone at 2x magnification is suitable for rigid body displacement measurement.