METHOD AND APPARATUS FOR COMPARING DATA SIGNALS IN A CONTAINER INSPECTION DEVICE

The present invention relates to an apparatus and method for generating a comparison signal representing the deviation between two analog video signals representing light received from particular inspection points on an object being inspected. The comparison signal is generated with a magnitude representing the ratio between the values of the two video signals. The ratio is calculated with the one of the two video signals having the larger magnitude as the denominator. In order to calculate the ratio, the present invention first converts the two analog video signals to digital form and then determines the log of each of digitized video signal. Next, the negative difference between the two log signals is determined. The negative difference is then exponentiated to determine the ratio.