Laser confocal radius measurement method for unpolished spheres

Area of Science:

• Optical Engineering
• Metrology
• Surface Science

Background:

• Accurate radius measurement is crucial for optical sphere processing.
• Existing methods face challenges with unpolished surfaces.
• Need for efficient and precise measurement techniques in optical manufacturing.

Purpose of the Study:

• To propose and validate a novel laser confocal radius measurement method for unpolished spheres (CRMUS).
• To assess the precision and applicability of CRMUS in real-time optical processing.
• To improve efficiency in optical sphere manufacturing.

Main Methods:

• Utilized laser confocal focusing technique to identify critical points on the unpolished sphere.
• Employed a distance measurement interferometer to determine the distance between cat's eye and confocal positions.
• Developed a partially coherent optical theoretical model for CRMUS analysis.

Main Results:

• CRMUS can measure the radius of unpolished spheres with surface roughness below 0.15 μm.
• Experimental validation using Schott BK7 demonstrated a relative expanded uncertainty of less than 20 ppm.
• The method accurately determines the radius by measuring the distance between cat's eye and confocal positions.

Conclusions:

• The proposed CRMUS is a viable and highly accurate method for measuring unpolished sphere radii.
• CRMUS offers significant potential to increase processing efficiency in optical manufacturing.
• The technique provides high precision suitable for demanding optical component fabrication.