Surface inspection is best processed using line scan cameras, primarily due to lighting considerations. This camera system uses an encoding device or clock that is tied into the drive train that moves the web. The encoder clocks the camera to build an area image, line by line, for a specified number of lines. The image can then be processed. In what’s known as a double buffer mode of operation, as one image can be processed the next image is being captured, thus providing 100% coverage. Such technology can be used to control slitter width or inspect graphics, typically at line speeds of 1000 in/min or more. In some systems, we have mixed area scan cameras and line-scan cameras to make a full part inspection.
In this example, 2 cameras are used to locate the part as it comes out of the oven and determine its rotation. A third camera is used to check the embossed part number and a fourth camera (line scan) is used to inspect a coating on the cylindrical side walls.
A second example illustrates a hi-speed line scan camera performing an inspection of a friction liner on a steel clutch core ring. This analysis is used to measure geometrical aspects of the liner as well as to check for defects in the friction material.