An object displacement detection method includes capturing n images of an object for obtaining n sets of image dots, where the object corresponds to an ith set of image dots in an ith image of the n images; performing (n−1) difference calculations using the n sets of image dots to obtain (n−1) sets of difference image dots, where a jth set of difference image dots of the (n−1) sets of difference image dots is generated by performing a jth difference calculation of the (n−1) difference calculations using a (j+1)th set of image dots and a jth set of image dots of the n sets of the image dots; and determining the object has displaced when a sum of numbers of the (n−1) sets of difference image dots reaches a first threshold.