1. A method to detect one or a plurality of defective pixels in a spatial light modulator, comprising the actions of: providing an electromagnetic radiation source to illuminate said spatial light modulator, arranging a reference pattern in said spatial light modulator, illuminating said spatial light modulator, determining a position of a reference pixel in said spatial light modulator by detecting a relayed image of said reference pattern in a detector arrangement, arranging a first pattern in said spatial light modulator, illuminating said spatial light modulator, detecting a relayed image of said first pattern in said detector arrangement, arranging at least a second pattern in said spatial light modulator, illuminating said spatial light modulator, detecting a relayed image of said at least a second pattern in said spatial light modulator analyzing said relayed images of said first pattern and said at least a second pattern to detect differences between said images and theoretical images thereof.