Advancing visual roughness measurement: A full-reference imaging approach for light source interference elimination

• A novel full-reference imaging (FRI) approach for visual roughness measurement is firstly proposed. • The FRI method effectively eliminates light source brightness fluctuations' impact on roughness measurements. • The FRI method is validated through theoretical derivation, numerical simulation, and experimental verification. • The FRI method lays a solid foundation for the development of visual roughness measurement instruments. Presently, variations in light source brightness significantly affect visual roughness measurement methods. To tackle this, a Full-reference imaging approach (FRI) is introduced to capture comprehensive light field information, encompassing incident and surface-reflected light. Utilizing the energy ratio between these fields minimizes light source interference and improves measurement accuracy. Initially, a relationship model, drawing upon Lambert-Beer and light scattering principles, correlates surface roughness with reflected and reference light energy. Theoretical feasibility is established, followed by validation of the model's robustness through numerical simulations. An FRI device is then developed to experimentally verify the model, showing a reduced impact of light source brightness on roughness measurements. Results demonstrate that the measurement system exhibits high stability and can detect a minimum roughness of 0.007 μm even with significant variations in light source brightness.