Grating phase extraction method of grating projection imaging system

The invention discloses a grating phase extraction method of a grating projection imaging system, solves the problem of how to overcome grating phase nonlinear errors and intensity noise in the prior art, and belongs to the technical field of digital grating projection three-dimensional measurement. The method comprises the following steps of: 1, forming a matrix X by using acquired N index grating images through neighborhood expansion; 2, constructing a covariance matrix C according to the matrix X, and diagonalizing the covariance matrix C to obtain a diagonal matrix D: D = ACAT; wherein after the background item of the index raster image is removed, A is an orthogonal transformation matrix, D is N rows and H * W columns, and [] T represents transposition; and step 3, obtaining a principal component matrix: obtaining principal components Ic and Is of the first two maximum characteristic values in the P, and obtaining an index grating phase according to the Ic and the Is, where (i, j) is a camera pixel coord