Fringe direction weighted autofocusing algorithm for gear tooth flank form deviation measurement based on an...

Area of Science:

• Optical Metrology
• Precision Engineering
• Image Processing

Background:

• Laser interferometry is crucial for measuring gear tooth flank form deviation.
• Limitations in lens depth of field cause focused and defocused regions in interferograms, leading to measurement errors.
• Accurate evaluation of interferogram definition is essential for reliable metrology.

Purpose of the Study:

• To develop a robust method for evaluating interferogram definition in laser-based gear metrology.
• To address the challenges posed by gray gradients and fringe patterns in traditional definition evaluation algorithms.
• To enhance the accuracy of gear tooth flank form deviation measurements.

Main Methods:

• Proposed a novel method combining nonsubsampled contourlet transformation (NSCT) with fringe direction weighting coefficients.
• Evaluated fringe direction information within interferograms.
• Applied NSCT to decompose interferograms into multi-scale and multi-directional sub-images.
• Developed an improved definition evaluation function utilizing NSCT outputs and directional information.

Main Results:

• The proposed NSCT-based method effectively handles gray gradients and fringe complexities in interferograms.
• Simulations and experimental results demonstrated the feasibility and accuracy of the new definition evaluation technique.
• Significant reduction in measurement errors caused by defocused regions was observed.

Conclusions:

• The NSCT combined with fringe direction weighting offers a superior approach for interferogram definition evaluation in gear metrology.
• This method enhances the precision of form deviation measurements for gear tooth flanks.
• The findings contribute to advancing accurate optical measurement techniques in engineering.