Moire contouring of large objects by a scanning technique

There is considerable interest in evaluating the contour of large objects. Conventional moire techniques possess shortcomings which limit the size of the object which may be contoured. This limitation has been overcome by 'moire scanning'. A low-powered light source such as a I m.w. laser illuminates a small area on an object. By use of two electrically operated beam scanners, the small illuminated area is slowly scanned so as to trace a linear ruling on the object. An obliquely oriented view camera records the tracing as it is formed. The camera's shutter is kept open while the beam scans the entire object surface. The information recorded on the film may be superimposed with a similar recording of another object by either double exposure, or by superposition.