Non-uniform illumination correction based on multi-scale Retinex in digital image correlation

Area of Science:

• Optical Measurement
• Digital Image Correlation (DIC)
• Image Processing

Background:

• Digital image correlation (DIC) measures displacement and strain fields by analyzing speckle images.
• Non-uniform illumination during image acquisition degrades DIC accuracy.
• Existing methods struggle with uneven lighting due to object size or light source variations.

Purpose of the Study:

• To introduce a multi-scale Retinex algorithm for correcting non-uniform illumination in DIC.
• To evaluate the impact of non-uniform illumination on DIC measurement accuracy.
• To validate the effectiveness of the proposed correction method in real-world experiments.

Main Methods:

• Numerical simulations of speckle images with varying non-uniform illumination.
• Application of a multi-scale Retinex algorithm for illumination correction.
• Experimental validation using rigid body rotation and uniaxial tensile tests.

Main Results:

• Non-uniform illumination significantly affects DIC measurement accuracy.
• The multi-scale Retinex algorithm effectively reduces or eliminates illumination non-uniformity.
• Experimental results demonstrate a significant improvement in DIC measurement accuracy after correction.

Conclusions:

• The multi-scale Retinex algorithm is a feasible and effective solution for non-uniform illumination in DIC.
• This correction method enhances the reliability and accuracy of optical measurement techniques.
• The study highlights the importance of addressing illumination variations for precise DIC analysis.