Inspection of surface flaws by comparator microscopy

Area of Science:

• Optical Engineering
• Materials Science
• Metrology

Background:

• Growing demand for precise surface quality control in optical components.
• Existing standards for flaws (digs, scratches) lack objectivity.
• Need for improved, quantifiable standards for both customers and suppliers.

Purpose of the Study:

• To address the lack of objective standards for optical surface flaws.
• To review current customer and supplier requirements for improved standards.
• To introduce and evaluate comparator microscopy as a new metrology technique.

Main Methods:

• Discussion of customer and supplier requirements for optical component standards.
• Review of recent attempts to establish more objective flaw assessment.
• Description of comparator microscopy: identifying line width that obstructs light equivalent to the flaw.

Main Results:

• Comparator microscopy demonstrates significant user-centric advantages.
• The line-equivalent width concept allows comparison of different national standard flaws.
• The technique is under consideration for an International Organization for Standardization (ISO) standard.

Conclusions:

• Comparator microscopy provides an objective and user-friendly method for assessing optical flaws.
• The line-equivalent width offers a quantifiable metric for flaw comparison.
• Future applications may include on-machine measurement of flaws and surface polish.