The device is designed for determining double refraction in flat blanks and products of transparent and weakly tinted materials, and is used for quantitative assessment of double refraction value by Senarmon method with an error of not greater than 10 nm, for assessment of double refraction distribution in an object by interference tinting, for examining distribution of double refraction in an object with circularly polarized light. 
       Instrument advantages are: its large observable field allows monitoring of large blanks and products and simultaneous monitoring of a few specimens.