Define the zone before defining the defect limit
A small defect across a functional narrow line may interrupt a reading, while a similar mark outside the active field may have no optical effect. Identify active tracks, clear apertures, alignment marks, clamp areas and edge exclusion zones on the DWG. Apply the agreed criteria to the relevant zone.
Describe defects by their effect on the pattern
A particle, excess film and missing film can look similar in an overview photograph but require different decisions. Record position and size as well as type, and state whether removable contamination is assessed before or after the agreed cleaning step.
| Observation | Potential functional effect | Useful inspection record |
|---|---|---|
| Excess opaque film | Narrows a clear feature or bridges adjacent regions | Coordinate, extent and affected clear feature |
| Missing opaque film | Light leakage, pinholes or a broken dark feature | Location relative to the critical track or mask feature |
| Edge irregularity | Changes local linewidth or edge detection | Measurement area and edge-detection method |
| Surface contamination | Scattering, obscuration or apparent pattern defects | Inspection state and agreed cleaning/reinspection result |
Compare measurements made under matching conditions
Record the datum, inspected area, support, temperature where relevant and the method used for edge or surface evaluation. For optical density or reflectance, include the wavelength and geometry. For flatness, identify whether the result describes the surface or an optical wavefront.
A fraction of a wavelength needs the reference wavelength and PV/RMS convention. In reflective interferometry, wavefront optical path difference and physical surface departure are not interchangeable. A report saying only “one-sixth wave” is insufficient for comparing acceptance results.
Agree the decision rule near a tolerance limit
A result near a limit needs its measurement uncertainty and the agreed decision rule. Do not silently round a result into compliance or treat uncertainty as an extra manufacturing allowance. Define the report resolution and the handling of borderline results before the delivery inspection.
Make the report identify the measured part
A useful record ties results to a drawing revision and part or lot identifier. For pattern measurements, include the feature coordinates or a labelled map so the customer can repeat the check at the same position. Distinguish measured values from nominal values copied from the drawing.
- Identify the inspected features, sampling scope, units and measuring conditions.
- If traceable calibration is required, state the required traceability and uncertainty; request the relevant service explicitly.
- Where a correction is agreed, retain the corrected area and reinspection result in the record.
Separate incoming-part checks from mounting effects
Before diagnosing a pattern defect after installation, check the film side, seating surface, clamping or bonding region and the image/readhead plane. A part that changes shape under mounting load needs an installed-condition review. Preserve the incoming inspection reference so that assembly effects can be compared with the delivered component.