Patent US 4,644,394

An apparatus and method are shown for inspecting the externally threaded surface of an object such as a pipe. A video camera is mounted in a translational frame for movement in x,y,z planes. The translational frame is mounted in a rotational assembly which rotates the frame about the circumference of the pipe threads to be inspected. The video signals from the camera are digitized and sent to a computer processor where the signals are interpreted to position the camera as it moves linearly along the axis of the pipe threads and to detect defects and discontinuities in the threaded surface of the pipe being inspected.