Abstract: Masks used in the production of integrated circuits are analyzed and tested by a scanning spot from a laser beam comparing the position signal of the scan from a mask against a data base representing another mask which may be selected at random. Apparatus includes a laser, means to form and scan a minute spot from said laser, an x-y stage to move a mask under the scan, a detector, and means to compare scan results.

Abstract: Methods and apparatus are disclosed for measuring and monitoring vibrational or similar motion in mechanical elements. Retroreflectors on the elements are illuminated with monochromatic light, preferably a laser, and the reflected beams form an interference pattern. Shifts in the interference fringes correspond to motion which changes the relative length of the paths of reflected light and these shifts are counted or analyzed to monitor such motion. Both micro and macro motion can be monitored.

Abstract: A system is disclosed for detecting, locating and monitoring floating objects and other subject matter at sea on another body of water or in other location of difficult access. A floating unit contains several retroreflecting elements and is placed at a location where detection is desired. For example, rescue or monitoring can be facilitated by detecting the floating unit from the air. Detection may include air borne signal apparatus such as a scanning laser beam or ordinary light source and air borne detection apparatus for detecting and analyzing a reflected signal.