Hole Inspection Method and Apparatus

An inspection apparatus initially involves an illuminator for directing an illuminating light beam towards a hole having two extremities and an internal surface extending between the two extremities. The inspection apparatus also involves a lens assembly for imaging the internal surface of the hole into the flat image. The lens assembly has a cylindrical field of view as well as a cylindrical depth of view. The cylindrical depth of field extends at least between the two extremities of the hole. The inspection apparatus further involves an image capturing device for capturing the flat image, and an image processing unit for performing inspection of the flat image to thereby inspect the internal surface of the hole. More specifically, the internal surface of the hole between the two extremities thereof is substantially in-focus along the flat image.