Diffractometric methods for absolute measurement of diffraction-grating spacings

We propose one- and two-wavelength methods of absolute measurement of diffraction-grating spacings based on the Littman configuration for autocollimation. The one-wavelength method has been applied to measure on the Littman configuration for autocollimation. The one-wavelength method has been applied to measure the spacing of a grating with a nominal value of 2160 grooves/mm. The grating spacing was measured to be 463.16 nm, with an experimental standard deviation of 0.24 nm. It has been demonstrated that the both methods can provide direct traceability in the submicrometer region in terms of wavelength standards for applications in the field of nanometrology. (C) 1999 Optical Society of America.