Abstract: A method of inspecting a transparent container for refractive defects includes positioning a light source in spaced relationship with respect to a detector which is operatively associated with a processor for receiving electrical signals from the detectors responsive to light passing through the container being received by the detector. The method includes positioning a grid filter having a plurality of alternating dark and light bands adjacent the light source so as to provide a multiple intensity gradient to the container. The container is positioned between the light source and the detector with the grid filter serving to provide adjacent alternate light and dark bands of light impinging on the container. Refractive defects will cause a distortion of the intensity gradient which will be received by the detector. In a preferred embodiment, a plurality of light and dark bands are generally horizontally oriented and produces a generally triangular wave having a constant absolute slope.

Abstract: A method and apparatus are provided for inspecting glass containers for checks. The container finish is illuminated from the exterior and light reflected from a check is detected by the apparatus. In one embodiment, the glass container finish is inspected for horizontal and related diagonal checks and, in another, the glass container finish is inspected for vertical and related diagonal checks. The checks redirect the normal beam of light and thereby permit the reflected light to be delivered to a detector which converts the received light into a corresponding electrical signal which is compared to a standard in order to determine whether the container should be rejected. The method eliminates incorrect inspection results due to reflection of light caused by threads, lugs, mold seams, takeout beads and the sealing surface of the container mouth. The vertical and horizontal embodiments may be combined into a single system which inspects for vertical, horizontal and diagonal checks.