A method for discriminating a type of disc. The invention also discloses methods to produce such PL polarizers. A controller may cause an interocular distance and a convergence angle between the left and right cameras to be set based on a maximum allowable disparity, the focal length of the lenses, and a convergence distance. Target A is designed to have an offset Xa between its first and second structures portions; target B is designed to have an offset Xb between its first and second structures portions; target C is designed to have an offset Xc between its first and second structures portions; and target D is designed to have an offset Xd between its first and second structures portions. In a CMOS device, performance can be improved by utilizing stress and manufacture processes can be simplified.