Abstract: A dual mode illumination system for optical inspection of products for surface defects and defects in holes in the product includes a first light source for providing illumination along an axis of one or more holes in the product to be inspected, the first light source being positioned on a first side of the product, a second light source providing illumination of the surface of the second side of the product to be inspected, a beam splitter for redirecting light from the second light source to a light sensor while passing light from the first light source to the light sensor. The second light source may be located adjacent to a second side of the product to be tested with the axis of illumination parallel to a major plane of the product. The light sensor may be a video camera connected to a data processing and display system.

Abstract: An optical inspection system is provided in which the background video component of an analog video source which limits imaging integrity is removed enhancing the system's ability to process a wider range of image sources with increase digitizing sensitivity. The overall effects of background and background variations are nulled stabilizing the effective signal to noise ratio, thereby increasing inspection capability of the system and improving the system's process window for effective and efficient inspection.

Abstract: An optical imaging surface inspection system and method are provided. The system comprises an illumination source for illuminating an image pattern on a surface to be inspected, a video camera for detecting a portion of the light reflected from the surface and outputting an analog video signal, a dynamic thresholding circuit for converting the analog video signal into a digital representation of the image pattern, and means to compare a known accurate digital representation of the image pattern to the digital representation provided by the dynamic thresholding circuit. The method includes the steps of illuminating the surface, scanning the surface with the video camera, separating the video signal into a black level signal component and a white level signal component, detecting successive peak levels in the white level signal component and outputting a corresponding variable peak voltage. A variable threshold voltage is determined by selecting a percentage of the variable peak voltage.