Differential ranging measurement system and method utilizing ultrashort pulses

An apparatus for profiling a surface of an object, comprising:

• means for generating a pulsed light beam;
• means for dividing said light beam into a plurality of spatially separate, parallel measurement light beams and a reference beam;
• means for directing said measurement light beams to said surface;
• means for scanning said measurement light beams across said surface;
• means for collecting portions of said measurement light beams reflected from said surface and combining said measurement light beams and said reference beam at a timegate providing an autocorrelation function of said beams;
• and
• means for measuring a differential distance between optical paths traveled by said measurement light beams, so as to obtain profile data on said surface.

An apparatus for examining a laminar surface, comprising:

• means for generating a pulsed light beam;
• means for dividing said light beam into at least one measurement light beam and a reference beam;
• means for directing said measurement light beam to said surface;
• means for collecting portions of said measurement light beam reflected from different lamina of said surface and combining reflected portions of said measurement light beam and said reference beam at a timegate providing an autocorrelation function of said beams;
• and
• means for measuring a differential distance between the different optical paths traveled by said measurement light beam, so as to obtain data on at least the thickness of said surface lamina.

An apparatus for measuring a differential positional deviation between at least first and second portions of an object from a remote location, comprising:

• means for generating a light beam of ultrashort pulses;
• means for dividing said light beam into at least a measurement beam and a reference beam;
• means for directing said reference beam to said first portion of said object, representing a reference portion;
• means for directing said measurement beam to said second portion of said object;
• means for collecting portions of said light beams reflected from said first and second portions and for combining the reflected beams at a time gate;
• said time gate obtaining an autocorrelation function of said beams, said function having maxima at time-separated locations corresponding to time of flight differences between said reflected beams;
• and
• detector means for determining a differential distance between said first and second portions, independently of any conjoint movement of said first and second portions.

A method for measuring a distance to an object, comprising the steps of:

• generating a light beam of ultrashort pulses;
• dividing said light beam into a plurality of light beams, including at least two measurement beams and a reference beam;
• directing said measurement beams to said object;
• and
• collecting portions of said measurement beams reflected from said object and combining said reflected beams and said reference beam at a time gate which provides an autocorrelation function of said beams;
• and
• measuring a differential distance in optical path traversed by said respective light beams.

An apparatus for determining the coordinates of a point on an object in a given Cartesian frame of reference from a remote location, comprising:

• means for generating a light beam of ultrashort pulses;
• means for dividing said light beam into a plurality of measurement beams and a reference beam;
• means for respectively directing said beams toward coordinate reference planes and said object;
• means for collecting portions of said light beams reflected from said object and said reference planes and for combining the reflected beams at a time gate;
• said time gate obtaining an autocorrelation function of said beams, said function having maxima at time-separated locations corresponding to time of flight differences between said reflected beams;
• and
• detector means for determining X and Y coordinates from at least the beams reflected from said coordinate reference planes, and for determining a Z coordinate from at least the beam reflected from said object.