are calculated according to the time spam that the two vertical synchronized signal 39 s positive triggers last vertical synchronized signals must be firstly detected about whether there is any incoming positive trigger signal entering in step s 204 if vertical synchronized signals do not contain any positive trigger horizontal synchronized signal interrupt enumeration shall then be deferred until a positive trigger signal is inputted on the contrary if a vertical synchronized signal positive trigger signal is inputted horizontal synchronized signal interrupt enumeration shall begin followed by verification of whether the synchronized signal interrupt value according to the counter 12 is 0 or otherwise step s 205 if 0 meaning an interrupt occurs at the first time the interrupting function by int pin of the microprocessor 10 is initiated step s 206 each time as the vertical synchronized signal is interrupted the enumeration adds up one count accordingly step s 301 to s 303 and calculation will be terminated at the second vertical synchronized signal positive trigger signal input when the second vertical synchronized signal interrupt value is inputted the enumeration of the horizontal synchronized signal interrupt will be terminated and in the meantime a horizontal synchronized signal interrupt value is obtained step s 207 by then the synchronized signal interrupt value from the counter 12 is.