Performance of a grating groove density measuring system by diffraction method

A grating groove spacing measurement system is established and checked by a sample grating. By detailed error analysis and error sources control, small spacing variation of either plane or concave grating can be determined with accuracy of ΔN/N=2×10~(-4). It is an efficient grating spacing measurement tool for the variable spacing grating as well as the constant spacing grating at NSRL.