Comparison of Correlation between 3D Surface Roughness and Laser Speckle Pattern for Experimental Setup Using He-Ne
Suganandha Bharathi Jayabarathi1,2, Mani Maran Ratnam2
1Faculty of Engineering and Computer Technology, AIMST University, Semeling, Bedong 08100, Kedah, Malaysia.
Sensors (Basel, Switzerland)
|August 26, 2022
Summary
A He-Ne laser setup demonstrated superior correlation between 3D surface roughness and laser speckle patterns compared to a laser pointer setup. This study highlights the effectiveness of He-Ne lasers for surface roughness analysis using speckle patterns.
Area of Science:
- Optics and Photonics
- Materials Science
- Surface Metrology
Background:
- Laser speckle patterns arise from the interference of scattered laser light on rough surfaces.
- Previous research correlated 3D surface roughness with speckle features using laser pointers and DSLR cameras.
- A comparative analysis between laser pointer and He-Ne laser experimental setups for surface roughness measurement was lacking.
Purpose of the Study:
- To compare the effectiveness of two experimental setups in correlating 3D surface roughness with laser speckle pattern features.
- To evaluate the performance of a He-Ne laser and spatial filter setup against a laser pointer and DSLR camera setup.
- To investigate the influence of illumination angles (30°, 45°, 60°) on the correlation between surface roughness and speckle characteristics.
Main Methods:
- Two experimental setups were employed: one with a He-Ne laser, spatial filter, and CCD camera; the other with a laser pointer and DSLR camera.
- Laser beams were directed at surfaces at 30°, 45°, and 60° angles.
- Matlab was used to extract Gray Level Co-occurrence Matrix (GLCM) and non-GLCM features from captured speckle patterns.
- Extracted features were correlated with 3D surface roughness parameters, and the coefficient of determination (R² ) was calculated.
Main Results:
- The He-Ne laser setup yielded better correlation results (R² ≥ 0.7) across all tested angles (30°, 45°, 60°) compared to the laser pointer setup (R² ≥ 0.7 only at 30° and 45°).
- For the He-Ne laser setup, mean and R-normalized features showed significant correlations at specific angles (45°, 60° and 30°, respectively).
- For the laser pointer setup, GLCM correlation and specific roughness parameters (S, S, S, S) showed notable correlations at 30° and 45° illumination angles.
Conclusions:
- The experimental setup utilizing a He-Ne laser, spatial filter, and CCD camera provides more reliable correlations between 3D surface roughness and laser speckle pattern features.
- The choice of laser source and illumination angle significantly impacts the accuracy of surface roughness characterization using speckle pattern analysis.
- This study establishes a novel correlation methodology using a He-Ne laser system and provides a critical comparison with a simpler laser pointer approach.
