MONOCHROMATIC LIGHT M027
A single (mono) color (chromatic) light is used with an optical flat to read seal face flatness.
We use a helium light source that emits a pink light with a wavelength of 0.000023 inches (0.6 microns). This light is used with an optical flat to read the light bands of flatness.
After the readings are taken they are compared to a chart that illustrates various flatness patterns.