Phase measurement deflectometry based on dual-frequency nonlinear fringes.

Area of Science:

• Optical Metrology
• 3D Surface Measurement
• Precision Engineering

Background:

• Traditional phase measurement deflectometry (PMD) faces challenges in high-precision 3D measurement of large curvature mirrors, including edge compression, phase ambiguity, and phase jumps.
• Phase unwrapping in PMD is critical but often hindered by discontinuities, limiting accuracy for complex surfaces.

Purpose of the Study:

• To develop an advanced phase measurement technique for high-precision 3D measurement of large curvature mirrors.
• To address and overcome the limitations of traditional PMD, specifically edge compression, phase ambiguity, and phase unwrapping discontinuities.

Main Methods:

• A dual-frequency nonlinear fringe pattern and a corresponding phase extraction and compensation model were proposed.
• An adaptive mirror curvature distribution was achieved using a combination of nonlinear radial fringes and tangential fringes with varying density.
• High-frequency components were utilized for precise phase measurement, while low-frequency components resolved high-frequency phase ambiguity.

Main Results:

• The proposed method demonstrated a significant improvement in accuracy for steep mirrors, achieving a Root Mean Square Error (RMSE) of 0.05558 μm.
• This represents a 37.71% improvement in RMSE compared to traditional methods.
• The Peak-to-Valley (PV) value was 0.41792 μm, marking a 43.58% enhancement, indicating superior detection performance.

Conclusions:

• The dual-frequency nonlinear fringe pattern method effectively addresses the limitations of traditional PMD for complex mirror metrology.
• The proposed technique significantly enhances the precision and reliability of 3D measurements for large curvature optical components.
• This advancement offers improved detection performance crucial for optical component manufacturing and quality control.