Abstract：To meet the requirements of the observations of the high strain-gradient region in engineering site, the stress light images and the residual stress measurement based on the photoelastic coating and drilling method, we research the reflective photoelastic apparatus based on the photoelastic coating technology, analyze the principle of the polarizing system of orthogonal reflective photoelastic apparatus. Error theory is applied to verify the feasibility and validity of the instrument design. The test data from the clockwise and anticlockwise directions are equal precision, and the limit error of the measuring apparatus is provided. The results show that all test data by the photoelastic method can be obtained by the proposed instrument, and that the limit error satisfies the error requirements of principle errors.

Keyword：error;orthogonal;reflective photoelastic apparatus;stress image;