Research on the DF-TSOM method for detecting subsurface defects of optical components

Area of Science:

• Materials Science
• Optical Physics
• Metrology

Background:

• Detecting nanoscale subsurface defects is crucial for material integrity.
• Traditional optical microscopy methods struggle with sub-micrometer defect detection.

Purpose of the Study:

• Introduce a novel dark field through-focus scanning optical microscopy (DF-TSOM) technique.
• Enable detection of hundred-nanometer scale subsurface defects.

Main Methods:

• Experimental validation using prepared subsurface defect samples (1 µm to 0.1 µm diameters).
• Comparison of DF-TSOM performance against traditional through-focus scanning optical microscopy (TSOM).

Main Results:

• DF-TSOM successfully detected subsurface defects as small as 0.1 µm in diameter.
• Traditional TSOM failed to accurately detect defects smaller than 0.4 µm.
• DF-TSOM demonstrated a tenfold improvement in contrast for 1 µm defects compared to TSOM.

Conclusions:

• DF-TSOM offers a highly sensitive and contrast-enhanced approach for subsurface defect detection.
• The technique simplifies hardware setup and shows potential for online monitoring.
• This method advances the capability for nanoscale defect inspection in transparent materials.