Patent ID: 6751880
Filing Date: 2004-06-22
Classification: G01C

Abstract:
An apparatus for providing at least one temporary visible reference line on a non-smooth surface characterized by a tendency to scatter incident visible light in random and non-uniform manner, comprising:a first group of laser sources, including a first laser source disposed at a first elevated location relative to the surface, said first laser source being operative to emit a first laser beam having a wavelength of between 400 nm and 750 nm and to direct visible light from said beam along a selectable path upon the surface so as to form a temporary visible line anywhere within a first region of the surface, and a second laser source disposed at a second elevated location relative to the surface, said second laser source being operative to emit a second laser beam having a wavelength of between 400 nm and 750 nm and to direct visible light from said second laser beam along the selected path so as to form, with light from said first laser beam, a composite temporary visible line within the first region; a second group of laser sources, including a third laser source disposed at a third elevated location relative to the surface and to the same lateral side of the surface as said first laser source, said third laser source being operative to emit a third laser beam having a wavelength of between 400 nm and 750 nm and to direct visible light from said third laser beam along a selectable path upon the surface so as to form a temporary visible line anywhere within a second region of the surface, and a fourth laser source disposed at a fourth elevated location relative to the surface and at the same lateral side of the surface as said second laser source, said fourth laser source being operative to emit a fourth laser beam having a wavelength of between 400 nm and 750 nm and to direct visible light from said fourth laser beam along the selected path so as to form, with light from said third laser beam, a composite temporary visible line anywhere within the second region; and a controller, responsive to line projection commands, adapted to selectively operate either the first group of laser sources or the second group of laser sources so as to project a composite temporary visible line on the non-smooth surface.