 According to trigonometry relations,

formula_1

formula_2

formula_3

where(xp, yp, zp) are coordinates of P in the left camera's coordinate system, f is focal length of the camera.Visual disparity is defined as the difference in image point location of a certain world point acquired by two cameras,

formula_4

based on which the coordinates of P can be worked out.Therefore, once the coordinates of image points is known, besides the parameters of two cameras, the 3D coordinate of the point can be determined.