For the model 401 Automatic Polariscope System produced by VishnyCompany of USA

a new method for solving the instability automatically is given.The computer automatically descriminates the states of the phase meter. The servo-system controlling the spin of the quarter wave plates is controlled in differentmanners for different states of phase meter. The collected data are examined andcorrected automatically. This method substitutes the old one which needs humaninterference and therefore the automatical processing is readed. Furthermore

theprecision of photoethetic fringe orders in the erratic area is raised.