Method to measure 3D deformation using defocused images of objects with artificial speckle features

Area of Science:

• Experimental Mechanics
• Optical Measurement
• Digital Image Processing

Background:

• Accurate 3D deformation measurement is crucial for material science and engineering.
• Existing methods may have limitations in simplicity or accuracy for certain applications.

Purpose of the Study:

• To present a novel, non-contact method for measuring three-dimensional (3D) deformation.
• To establish a theoretical and experimental basis for the proposed measurement technique.

Main Methods:

• Acquiring defocused images of objects with artificial speckle features.
• Calculating in-plane coordinates using camera parameters and defocused distance.
• Determining depth via the relationship between defocused distance and image blur (blur band width).
• Employing digital image correlation (DIC) to track point displacements before and after deformation.

Main Results:

• A novel method for 3D deformation measurement based on defocused images was developed.
• The relationship between defocused distance and blur degree was theoretically and experimentally defined.
• The method successfully obtained 3D deformation by tracking point displacements using DIC.
• The technique's reliability was confirmed through two validation experiments.

Conclusions:

• The proposed method offers a viable approach for measuring 3D deformation.
• Defocused image analysis combined with DIC provides accurate displacement data.
• This technique has potential applications in various fields requiring precise deformation analysis.