Abstract: An apparatus for monitoring and determining the distances of points on a surface from a reference axis includes a light source, such as a laser, for projecting a main beam of light of relatively small diameter along an axis. A device, such as a diffraction grating, is provided for splitting the main beam of light into a plurality of discrete fractional beams of light. A further component, such as a diverging lens, angularly displaces the fractional beams relative to each other so the beams extend along a common plane towards a position for an object. Light reflected from the surface is projected onto a linear photodetector, the positions where the reflected fractional beams strike the linear photodetector being related to the distance from a reference axis to the points on the object where the fractional beams are reflected.

Abstract: An apparatus for monitoring and determining the distances of points on a surface from a reference axis includes a light source, such as a laser, for projecting a main beam of light of relatively small diameter along an axis. A device, such as a diffraction grating, is provided for splitting the main beam of light into a plurality of discrete fractional beams of light. A further component, such as a diverging lens, angularly displaces the fractional beams relative to each other so the beams extend along a common plane towards a position for an object. Light reflected from the surface is projected onto a linear photodetector, the positions where the reflected fractional beams strike the linear photodetector being related to the distance from a reference axis to the points on the object where the fractional beams are reflected.