US Patent 11182586 Background subtraction method, image module, and optical fingerprint identification system

A background subtraction method includes: obtaining a first background image corresponding to a first object, wherein the first object has a first reflectivity; obtaining a second background image corresponding to a second object, wherein the second object has a second reflectivity, and the first reflectivity is different from the second reflectivity; calculating a plurality of relative values of the first background image relative to the second background image so as to obtain a mask image; obtaining a target image; subtracting the second background image from the target image so as to obtain a first background-removed image; and calculating and outputting a second background-removed image according to the first background image, the second background image, the first background-removed image and the mask image.