Apparatus and methods for surface contour measurement

A method for synthesizing a wrapped cycle map corresponding to a fringe pattern of a predetermined spacing on a surface, said method comprising the steps of:

• a) providing two sources of radiation having a spatial distribution of spectral regions;
• b) illuminating said surface with said radiation from each of said sources to produce a first fringe pattern at a first position on said surface;
• c) moving said first fringe pattern to a second position on said surface;
• d) generating a first wrapped cycle map in response to said first and second positions of said first fringe pattern;
• e) changing said first fringe pattern to generate a second fringe pattern at a first position;
• f) moving said second fringe pattern to a second position;
• g) generating a second wrapped cycle map in response to said first and second positions of said second fringe pattern;
• h) subtracting said second wrapped cycle map from said first wrapped cycle map;
• and
• i) wrapping said difference between said second wrapped cycle map and said first wrapped cycle map to generate a wrapped cycle map corresponding to said fringe pattern of said predetermined spacing.

A method for determining, on an object having a surface, three-dimensional position information of a point on said surface of said object, said method comprising the steps of:

• a) generating a first and a second beam of radiation, said first and second beams of radiation having a first frequency and being coherent with respect to one another;
• b) illuminating said surface with said second beam of radiation;
• c) generating a first interference pattern at a first position in response to said first beam of radiation and radiation from said second beam of radiation scattered by said surface;
• d) moving said first interference pattern to a second position;
• e) generating a first wrapped cycle map in response to said first and second positions of said first interference pattern;
• f) estimating intensity cycles in said first interference pattern;
• g) changing said first interference pattern to generate a second interference pattern at a first position;
• h) moving said second interference pattern to a second position;
• i) generating a second wrapped cycle map in response to said first and second positions of said second interference pattern;
• j) estimating intensity cycles in said second interference pattern in response to estimated intensity cycles in said first interference pattern;
• and
• k) calculating said three-dimensional position information in response to said estimated intensity cycles in said second interference pattern and said second wrapped cycle map.

A method for determining, on an object having a surface, three-dimensional position information of a point on said surface of said object, said method comprising the steps of:

• a) generating a first and a second beam of radiation, said first and second beams of radiation being coherent with respect to one another;
• b) illuminating said surface with said second beam of radiation;
• c) generating a first interference pattern in response to said first beam of radiation and radiation from said second beam of radiation scattered by said surface;
• d) phase shifting one of said first and second beams of radiation with respect to the other of said first and second beams of radiation to generate a first phase shifted interference pattern;
• e) generating a first wrapped cycle map in response to said first interference pattern and said first phase shifted interference pattern;
• f) changing said first interference pattern to generate a second interference pattern;
• g) phase shifting one of said first and second beams of radiation with respect to the other of said first and second beams of radiation to generate a second phase shifted interference pattern;
• h) generating a second wrapped cycle map in response to said second interference pattern and said second phase shifted interference pattern;
• i) subtracting said second wrapped cycle map from said first wrapped cycle map;
• and
• j) wrapping said difference between said second wrapped cycle map and said first wrapped cycle map to generate a wrapped cycle map.

A method for determining, on an object having a surface, three-dimensional position information of a point on said surface of said object, said method comprising the steps of:

• a) projecting a first cyclical pattern to produce a first projected pattern at a first position on said surface;
• b) moving said first projected pattern to a second position;
• c) generating a first wrapped cycle map in response to said first and second positions of said first projected pattern;
• d) estimating cycle numbers in said first projected pattern;
• e) changing said first projected pattern to generate a second projected pattern at a first position;
• f) moving said second projected pattern to a second position;
• g) generating a second wrapped cycle map in response to said first and second positions of said second projected pattern;
• h) estimating cycle numbers in said second projected pattern in response to said estimated cycle numbers in said first projected pattern;
• and
• i) determining said surface in response to said estimated cycle numbers in said second projected pattern and said second wrapped cycle map.

A method for synthesizing a wrapped cycle map corresponding to a projected cyclical pattern of a predetermined spacing on a surface, said method comprising the steps of:

• a) projecting a first cyclical pattern to produce a first projected pattern at a first position on said surface;
• b) moving said first projected pattern to a second position on said surface;
• c) generating a first wrapped cycle map in response to said first and second positions of said first projected pattern;
• d) changing said first projected pattern to generate a second projected pattern at a first position;
• e) moving said second projected pattern to a second position;
• f) generating a second wrapped cycle map in response to said first and second positions of said second projected pattern;
• g) subtracting said second wrapped cycle map from said first wrapped cycle map;
• and
• h) wrapping said difference between said second wrapped cycle map and said first wrapped cycle map to generate a wrapped cycle map corresponding to said projected cyclical pattern of said predetermined spacing.

A method for mitigating the effects of speckle on a measurement of a point on a surface of an object, said method comprising the steps of:

• a) generating a coherent fringe pattern from two sources of radiation separated by a distance;
• b) projecting the coherent fringe pattern onto the surface of the object;
• c) detecting the fringe pattern and the speckle in an image of the surface of the object;
• d) translating the two sources such that the fringe pattern remains substantially stationary and the speckle changes;
• e) detecting the new fringe pattern and the changed speckle in an image of the surface of the object;
• and
• f) determining the fringe pattern substantially without speckle in response to the detected fringe patterns and the change in speckle.

A method for mitigating the effects of speckle on a measurement of a point on a surface of an object, said method comprising the steps of:

• a) generating a coherent fringe pattern from two sources of radiation separated by a distance;
• b) projecting the coherent fringe pattern onto the surface of the object;
• c) detecting the fringe pattern and the speckle in an image of the surface of the object;
• d) translating the object laterally with respect to the two sources of radiation along a path parallel to the equiphase plane of the fringe pattern such that the fringe pattern remains substantially stationary with respect to the surface of the object and the speckle changes;
• e) detecting the new fringe pattern and the changed speckle in an image of the surface of the object;
• and
• f) determining the fringe pattern substantially without speckle in response to the detected fringe patterns and the change in speckle.

A method for mitigating the effects of speckle on a measurement of a point on a surface of an object, said method comprising the steps of:

• a) projecting a coherent fringe pattern onto the surface of the object;
• b) providing a lens having a transmission function having a gradual transmission drop off at the lens edge;
• and
• c) detecting the fringe pattern in an image of the surface of the object, wherein the transmission function substantially reduces the speckle influence on the measurement.

A method for mitigating the effects of speckle on a measurement of a point on a surface of an object, said method comprising the steps of:

• a) generating a first fringe pattern from two sources of radiation having a first frequency and separated by a distance;
• b) changing said first fringe pattern to generate a second fringe pattern by changing said first frequency to a second frequency;
• and
• c) changing said distance in response to the difference between said first frequency and said second frequency, wherein the ratio of said distance to the difference between said first frequency and said second frequency is substantially constant.

A method for projecting fringes onto a surface of object, said method comprising the steps of:

• a) providing two sources of radiation separated by a distance, each of said sources having a spectral distribution and being coherent with respect to the other of said sources;
• b) illuminating said point on said surface of said object with said radiation from each of said sources;
• c) moving one of said sources relative to the other of said sources;
• d) detecting radiation scattered by said point on said surface of said object;
• and
• e) calculating position information in response to said movement of said sources and said detected radiation scattered by said point on said surface of said object.

An apparatus for projecting fringes onto a surface of an object, said apparatus comprising:

• a) two sources of radiation separated by a distance, each of said sources having a spectral distribution and being coherent with respect to the other of said sources;
• b) control system moving each of said sources relative to the other of said sources;
• c) a detector positioned to receive radiation scattered from said point on said surface of said object;
• and
• d) a processor receiving signals from said detector, said processor calculating position information in response to said movement of said sources and said received radiation scattered from said point on said surface of said object.

A method for determining, on an object having a surface, three-dimensional position information of a point on said surface of said object, said method comprising the steps of:

• a) providing two sources of radiation, each of said two sources of radiation having a spectral distribution and being coherent with respect to the other of said two sources;
• b) providing a detector at said point on said surface;
• c) illuminating said point on said surface of said object with said radiation from each of said sources;
• d) moving each of said sources relative to each other;
• e) detecting said radiation at said point on said surface of said object;
• and
• f) calculating position information in response to said movement of said sources and said radiation detected at said point on said surface of said object.

An apparatus for determining, on an object having a surface, three-dimensional position information of a point on said surface of said object, said apparatus comprising:

• a) two sources of radiation, each of said sources having a spectral distribution and being coherent with respect to one another;
• b) a control system moving each of said sources relative to each other;
• c) a detector positioned at said point on said surface of said object to receive radiation illuminating said point on said surface of said object;
• and
• d) a processor receiving signals from said detector, said processor calculating position information of said point on said surface of said object in response to said movement of said sources and said radiation received at said point on said surface of said object.