Optic flat is the most reliable and objective way to check the flatness of high precision parts. The wave-legnth of the monochromatic lamp is 589.3nm, each fringe shown on the parts surface equal to a flatness of 0.3um。Monochromatic lamp type-A is capable for the using of an optical flat with the diameter of 30mm～150mm, type-B is for capable for the using of an optical flat with the diameter as big as 300mm . The measuring instrument can be put in the pruduction area,stable and easy to use. For small, light and eay deformed parts,type-A is recommended to use, and for big,heavy parts, type-B is recommended instead.
