Laser ElectroOptic System For Rapid ThreeDimensional (3D) Topographic Mapping Of Surfaces
Abstract
A method is described for highresolution remote threedimensional mapping of an unknown and arbitrarily complex surface by rapidly determining the threedimensional locations of M x N sample points on that surface. Digital threedimensional (3D) locations defining a surface are acquired by (1) optically transforming a single laser beam into an (expanded) array of M x N individual laser beams, (2) illuminating the surface of interest with this array of M x N (simultaneous) laser beams, (3) using a programmable electrooptic modulator to very rapidly switch on and off specified subsets of laser beams, thereby illuminating the surface of interest with a rapid sequence of mathematical patterns (space code), (4) image recording each of the mathematical patterns as they reflect off the surface using (a) a wavelengthspecific optically filtered video camera positioned at a suitable perspective angulation and (b) appropriate image memory devices, (5) analyzing the stored images to obtain the 3D locations of each of the M x N illuminated points on the surface which are visible to the camera or imaging device, and (6) determining which of the laser beams in the array do not provide reflections visible to the imaging device. Space coding of the light beams allows automatic correlation of the camera image (of the reflected spot pattern from the surface) with the projected laser beam array, thus enabling triangulation of each illuminated surface point. Whereas ordinary laser rangefinders aim and project one laser beam at a time and expect to receive one laser beam reflection (bright dot image) at a time, the present system is optical (nonmechanical and vibrationfree) and can collect all the data needed for highresolution 3D topographic mapping (of an M x N sample of surface points) with the projection of as few as 1 + log2N light patterns. In some applications involving a rapidly changing timedependent environment, these 1 + log2N patterns can be projected simultaneously in different wavelengths to allow virtually
 Publication:

Optical Engineering
 Pub Date:
 December 1981
 DOI:
 10.1117/12.7972842
 Bibcode:
 1981OptEn..20..953A