Abstract
This paper describes recent trends of high-precision optical measurements. First, interferometric length-measuring methods are reviewed, wich inclnde fringe-counting methods, optical heterodyning techniques, synthetic-wavelength methods and two-color methods for an air refractive index. Secondly, the outline of measuring methods are presented of dimensions, length, gravity, water-density, fluxoid quantum, Avogardro's number, and earth strain in physics.
