Abstract: In a coherent optical correlation system for detection of object images at unknown angular orientations, a holographic spatial filter in the transform plane of the system is rotated until a correlation beam is produced. The spatial filter is mounted on a rotating cylinder which carries a first mirror placed in the path of the correlation beam emitted from the filter and disposed to direct the beam toward the axis of rotation of the cylinder and a second mirror on the axis and intercepting the beam for directing the correlation beam substantially along the axis. A motor drives the cylinder about its axis and an optical encoding device associated with the rotating cylinder provides an electronic indication of the cylinder orientation at any given instant.

Abstract: Coherent optical correlation is applied to an article having circular features as well as noncircular features. A spatial filter is constructed for a typical part with the noncircular features masked out. The filter is placed in the transform plane of the optical correlation system so that the system will produce correlation signals indicating the presence, the coordinate position and angular orientation of the part within the field of view of the system.

Abstract: The orientation of an industrial part such as a microcircuit chip having a pattern of dominant parallel lines is determined by an optical method. An image of the parallel line pattern is smeared or defocused in a known direction such that the resultant smeared image of the part reveals the lines in sharp detail when they are parallel to the known direction of smearing and are blurred if the lines are angularly displaced from the known direction. By rotating the image of the pattern relative to the smear direction and determining the angle at which maximum sharpness occurs, the angular orientation is determined. By correlating the pattern of sharp lines of the smeared image with a similar reference pattern of known position, the positional orientation of the part is also determined. When two angularly displaced families of parallel lines are present on the object, positional coordinates relative to two axes are determined.