USING THE DIGITAL VERNIER FRINGES FOR MEASUREMENT OF OBJECTS LINEAR DISPLACEMENT
The digital vernier fringes formed by means of subtraction of diffraction pattern images using radiation sources with different wavelengths are offered for increase of linear measurement sensitivity and accuracy. It is shown, that conversion factor of displacement for the digital fringes depends on the ratio of wavelengths and this fringes can be extracted from image by means of Hilbert transform. Calculations and experiment show that proposed method allows to measure image shift with subpixel error (to 1/30 pixel of detector) and to reduce the discretization error of measurement. This method using digital vernier fringes can be used for linear displacement sensor creation heaving measurement error to 0,05 %.