Patent ID: 8358830

Claim:
A method of detecting optical defects in a transparency, comprising the steps of: providing a digital image of the transparency, the digital image including a plurality of image pixels each having a grayscale intensity; detecting at least one candidate defect by performing the following: determining a grayscale intensity of each one of the image pixels; calculating an intensity gradient across adjacent pairs of the image pixels; assigning to each image pixel a gradient value comprising a maximum of the absolute value of the intensity gradients associated with the image pixel; constructing a gradient image comprising the gradient values assigned to corresponding ones of the image pixels; and identifying as candidate pixels the image pixels having a gradient value exceeding a gradient threshold, the candidate pixels comprising the candidate defect; identifying optical defects among the candidate defect by performing the following: determining the location of each one of the candidate pixels; clustering the candidate pixels into at least one pixel cluster based upon the relative locations of the candidate pixels; and comparing the quantity of the candidate pixels in the pixel cluster to a pixel quantity threshold to identify the candidate defect as at least one of an optical defect and an image defect.