Development of a combined optical and X-ray interferometer (COXI) at KRISS

The objective of COXI is to provide a means for the calibration of transducers or laser interferometers in the nanometer range in terms of the standards of length. The basic idea of COXI is to combine an X-ray interferometer with an optical interferometer in such a way that one can obtain the angstrom resolution of the X-ray interferometer over the extended measurement range. The limited measurement range and speed of an X-ray interferometer can be increased in COXI by using the optical interferometer as the main ruler and the X-ray interferometer as a linear interpolator. This was first suggested and reported by researchers in NPL, PTB, and IMGC. This paper gives a brief description of the basic principle, overall configuration and major components of the COXI which is under development at the Korea Research Institute of Standards and Science (KRISS), aimed at a measurement uncertainty of 0.1 nm over 1 mm range.