Flexible geometrical calibration for fringe-reflection optical three-dimensional shape measurement

Area of Science:

• Optical Metrology
• Precision Engineering
• Image Processing

Background:

• Accurate geometrical calibration is crucial for fringe-reflection testing systems, particularly for calibrating reflection ray directions.
• Traditional calibration methods based on the pinhole camera model are susceptible to pupil imaging aberrations.
• Existing workarounds, like using external stops, introduce challenges in precise geometrical measurements and signal-to-noise ratios.

Purpose of the Study:

• To introduce a novel and practical calibration method for fringe-reflection testing systems.
• To address the limitations of existing methods in accurately calibrating reflection ray directions.
• To provide a flexible and robust solution for geometrical calibration in optical metrology.

Main Methods:

• A new calibration method is proposed utilizing correspondence matching on a liquid crystal display (LCD).
• Points on the LCD at different positions are identified to correspond to the same camera pixels.
• This approach bypasses the need for precise pinhole geometrical measurements and overcomes low signal-to-noise issues.

Main Results:

• The proposed calibration method demonstrates simplicity and practicality in experimental settings.
• Successful application in fringe-reflection testing validates the method's effectiveness.
• The technique provides accurate calibration of reflection ray directions, enhancing system precision.

Conclusions:

• The developed calibration method offers a significant advancement for fringe-reflection testing systems.
• It provides a simple, practical, and flexible solution for accurate geometrical calibration.
• This method effectively overcomes the challenges associated with pupil imaging aberrations and low signal-to-noise ratios.