A CMM-Based Method of Control Point Position Calibration for Light Pen Coordinate Measuring System

Area of Science:

• Metrology
• Optical Measurement Systems
• Precision Engineering

Background:

• Light Pen Coordinate Measuring Systems (LPCMS) are vision-based portable techniques requiring accurate calibration.
• The precise determination of relative control point positions is critical for LPCMS functionality and measurement accuracy.
• Existing calibration methods face challenges in achieving high accuracy for control point positioning.

Purpose of the Study:

• To propose and validate a new, highly accurate method for calibrating the relative positions of control points in LPCMS.
• To leverage the precision of Coordinate Measuring Machines (CMMs) for enhanced LPCMS calibration.
• To improve the overall measurement accuracy and reliability of LPCMS.

Main Methods:

• A novel calibration approach utilizing a traditional Coordinate Measuring Machine (CMM) is presented.
• The light pen is mounted on the CMM's measuring arm, enabling controlled translational movements.
• Simultaneous image capture of control points and CMM readings are performed, with data processed using a coordinate transformation technique.

Main Results:

• The proposed method demonstrates excellent calibration repeatability for control point positions, reaching 10 μm.
• The overall Light Pen Coordinate Measuring System (LPCMS) exhibits a standard deviation of measurement of 30 μm.
• Mathematical processing of extensive data acquired through CMM-driven movements effectively reduces random error influence.

Conclusions:

• The CMM-based calibration method offers a high-accuracy solution for determining light pen control point positions.
• This technique enhances the precision and reliability of vision-based portable coordinate measuring systems.
• The proposed approach provides a robust foundation for advanced applications requiring precise metrology.