Lateral-scanning through-focus microscopy for high-speed three-dimensional localization of subsurface defects

Area of Science:

• Optical Metrology
• Materials Science
• Quality Control

Background:

• Accurate 3D localization of subsurface defects is vital for manufacturing and inspection.
• Traditional optical methods face limitations in achieving both large field of view and high localization accuracy.

Purpose of the Study:

• To develop an advanced microscopy technique for precise 3D localization and detection of subsurface defects.
• To overcome the limitations of conventional optical measurement techniques in transparent samples.

Main Methods:

• Proposed a lateral-scanning through-focus microscopy system.
• Utilized optical axis tilting to capture defects at varying depths within a single image.
• Integrated horizontal scanning for extended field of view 3D localization.

Main Results:

• Achieved sub-pixel accuracy in 3D defect localization using ring light illumination on SiO2 samples.
• Demonstrated a relative standard deviation of 0.77% for depth measurements.
• Validated wide-field 3D localization capability with microsphere samples.

Conclusions:

• The proposed lateral-scanning through-focus microscopy enables accurate wide-field 3D localization of subsurface defects.
• Ring light illumination significantly enhances localization accuracy and precision.
• The system offers a promising solution for non-destructive testing in transparent materials.