The invention discloses a method for detecting
residual stress of a
birefringent crystal, which is characterized by comprising the following steps of: fixing a sample to be detected on a sample loading table; the
imaging lens is used for acquiring light rays which sequentially penetrate through the
polarizer module, a sample to be detected on the sample loading table, the analyzer module and the
camera module in four states in three states that polarization axes of the
polarizer module and the analyzer module are mutually orthogonal and a polarization angle is gradually increased by 30 degrees, and in a state that the
polarizer module and the analyzer module are in parallel, and the
imaging lens is used for acquiring the light rays which sequentially penetrate through the polarizer module, the sample to be detected on the sample loading table, the analyzer module and the
camera module in the four states; collecting a
light intensity matrix set through a
camera module; acquiring a reference
light intensity matrix through normalized linear superposition, and performing pixel-by-pixel operation with the reference
light intensity matrix on the basis of the
first light intensity matrix, the second light intensity matrix and the third light intensity matrix to acquire corresponding phase
delay matrixes; eliminating natural
birefringence and updating a phase
delay matrix by deducting respective overall average phase
delay amount pixel by pixel; through pixel-by-pixel weighted stacking, isogradient lines are eliminated, and distribution information of
residual stress is obtained.