Key Surface Defects Inspection Standards for Precision Optical Windows
Key Surface Defects Inspection Standards for Precision Optical Windows
Surface defects such as scratches, digs, bubbles and stains directly affect optical performance of optical windows, domes and lenses. These flaws can cause light scattering, hot spots, imaging distortion or reduced component service life. For high-precision optical systems, surface quality grade is one of the most critical technical specifications.
The widely used Scratch-Dig Specification
Scratch-Dig (S/D) standard is the common surface quality specification for optical components. It contains two numbers: scratch value and dig value.
For example: 60-40.
- Scratch: Defines the maximum allowable width of linear scratch marks on optical surface. Smaller number = stricter standard.
- Dig: Defines the maximum allowable diameter of point pits, chips and digs. Smaller number = higher quality.
Typical grade reference:
- General industrial optical window: 80-50
- Marine monitoring optical dome: 60-40
- High-precision laser / medical optics: 40-20 or stricter
Main Surface Defects We Inspect
- Scratches: Linear marks generated during polishing or handling. Long scratches will scatter light and interfere imaging.
- Digs / pits: Round or irregular indentations on optical surface.
- Bubbles & inclusions: Internal material impurities inside glass substrate.
- Stain & residue: Coating contamination or cleaning marks after finishing.
Felix Glass QC Workflow for Surface Inspection
Our QC team performs visual inspection under controlled light source. Critical high-grade optical parts use microscope inspection. All finished optical windows and domes will be checked for surface defects before packaging. We mark the surface quality grade in inspection report for each batch.
How to choose suitable surface grade
You do not always need the strictest scratch-dig grade. Higher grade increases cost and lead time. Our optical engineers help you select proper surface quality standard balancing optical performance and budget.
View our optical windows and optical domes product pages for optical component quality control details.
Contact us via the Request Quote page to discuss your optical surface requirements.
