Correlation Study of 3D Surface Roughness of Milled Surfaces with Laser Speckle Pattern

Area of Science:

• Metrology
• Optical Engineering
• Materials Science

Background:

• Current research links laser speckle patterns to 2D surface roughness.
• Milled surfaces are inherently 3D, necessitating 3D roughness parameters for accurate assessment.

Purpose of the Study:

• To investigate the correlation between laser speckle pattern features and 3D surface roughness parameters.
• To evaluate the use of an inexpensive laser pointer without spatial filtering for speckle pattern generation.
• To determine the influence of illumination angle, aperture size, and shutter speed on this correlation.

Main Methods:

• Utilized an inexpensive laser pointer to generate speckle patterns from machined surfaces.
• Extracted characteristic features from laser speckle patterns using image analysis techniques.
• Correlated these features with 3D surface roughness parameters, specifically S10z.
• Investigated the impact of varying illumination angles, f-numbers, and shutter speeds.

Main Results:

• Achieved a high coefficient of determination (0.8955) between the gray level co-occurrence matrix descriptor 'energy' and the 3D surface roughness parameter S10z.
• Identified optimal conditions for illumination angle (45°), f-number (16), and shutter speed (1/100 s) for this correlation.
• Demonstrated the feasibility of using a simple laser pointer for surface characterization.

Conclusions:

• Laser speckle pattern analysis is a viable and cost-effective method for characterizing 3D surface roughness of milled parts.
• The 'energy' feature of the speckle pattern shows strong correlation with the S10z parameter.
• Optimized optical and imaging parameters enhance the accuracy of this non-contact measurement technique.