Monochromatic Check light is required for gauging flatness of finished parts with the help of Optical Flats.
Red band for high accuracy and blue band for normal accuracy requirements.
It is essential that surfaces which are to be measured should be made reflective.
Optical flat which is placed over the surface to be measured, will
reflect the light emitted from the source, interference lines appear on
the surface in various patterns and their deviation from the straight
reference line depicts the extent of out of flatness of surface being