Method for measuring geometric dimensions of micro parts based on a telecentric camera

Area of Science:

• Metrology
• Optical Engineering
• Manufacturing Technology

Background:

• Precision measurement is crucial for industries like semiconductors and electronics.
• Traditional vision-based measurement methods using ordinary lenses suffer from distortion and magnification variability, limiting accuracy.
• Telecentric cameras offer a solution by minimizing these optical aberrations.

Purpose of the Study:

• To propose a high-precision measurement method for micro-parts using a telecentric camera.
• To develop accurate telecentric camera calibration and sub-pixel edge detection techniques.
• To validate the system's performance through experimental evaluation.

Main Methods:

• A high-precision, single-image telecentric camera calibration method was developed.
• An improved Zernike moment sub-pixel edge detection algorithm, inspired by the Steger algorithm, was implemented.
• A measurement system was built to test camera calibration, system calibration, and practical performance.

Main Results:

• The telecentric lens exhibited a low relative magnification error of 0.7%.
• The system achieved a maximum mean absolute error of 0.84μm over a 2.1 mm measurement range.
• Experimental validation confirmed the method's high precision and stability.

Conclusions:

• The proposed telecentric camera measurement method significantly improves accuracy for micro-part geometric dimension inspection.
• The enhanced calibration and edge detection techniques provide reliable technical support for manufacturing precision assessment.
• This approach addresses limitations of traditional optical measurement systems in high-precision applications.