Determining the refractive index distribution of optical components by dual-wavelength digital holographic microscopy with a liquid

A method is proposed for measuring the two-dimensional distribution of the refractive index in transparent micro-optical components. The proposed method combines dual-wavelength digital holographic microscopy with liquids to record holograms at different wavelengths and to numerically reconstruct the three-dimensional phase information to obtain the sample's distribution of the refractive index. A theoretical model is proposed for determining the two-dimensional distribution of the refractive index; an achromatic lens and plate are demonstrated experimentally. Unlike conventional scanning interferometry, the proposed method supports non-scanning measurement and direct observation, independent of the sample's shape, of the two-dimensional distribution of refractive indices in micro-optical elements.