1. A method of evaluating image correlation with speckle pattern, comprising steps of: (a) capturing a First Speckle-Pattern Image and at least one Second Speckle-Pattern Image of a target object at different times, separately; (b) obtaining a first modulation transfer function (MTF) curve of said First Speckle-Pattern Image and obtaining at least one second MTF curve of said at least one Second Speckle-Pattern Image; (c) obtaining a correlation value between said first MTF curve and said at least one second MTF curve; and (d) finishing evaluating said correlation value between said first MTF curve and said at least one second MTF curve when said correlation value meets a threshold.