Patent ID: 7965394

Claim:
A method for identifying dynamic characteristics of a vibratory object, comprising the steps of: (a) defining a scan frequency range while setting a series of scan frequencies within the scan frequency range; (b) acquiring a differential fringe density index of the vibratory object by the use of a two-dimensional image scanning procedure, wherein the step (b) further comprises the steps of: (b1) making an evaluation to determine the height of the vibratory object; (b2) acquiring an interferogram of the vibratory object under strobed light of different phases; (b3) performing an image processing procedure upon the interferogram to obtain a processed image correspondingly; (b4) estimating the spatial frequency domain of the processed image for obtaining and thus recording a differential fringe density index corresponding to the processed image; and (b5) changing the height of the vibratory object and thereafter repeating the step (b2) to step (b5); (c) altering the scan frequency while repeating the steps from (b) to (c) if the altered scan frequency falls in the defined scan frequency range; otherwise, directing the method to proceed to step (d); and (d) analyzing the differential fringe density index through peak detection so as to obtain a dynamic characteristic of the vibratory object; wherein the differential fringe density index is a difference of two fringe density indexes respectively corresponding to the two neighboring scanning frequencies, and the fringe density index is related to an numerical operation performed upon pixel values in the processed image, such as the clarity or contrast of the processed image.