Optical Flat Instrument Information
A round optical grade piece of glass, lapped and polished to be extremely flat on one or both sides. Monochromatic light is then passed through the glass, creating interference bands of light used to determine flatness of other surfaces (optical, metallic, ceramic, etc.). When viewed through the optical flat, if the bands of light are curved or unevenly spaced, the surface is not flat.

Common Uses
- Measuring flatness of a flat lapped or polished surface, such as micrometers, gage blocks and snap gages
Common Types
- Wavelengths
- Coatings
- Sizes (Diameter, Thickness)
- Flatness
Measurement Parameter
Flatness
Calibration Discipline
Calibration Equipment Used
ULM System