Infrared scanning interferometry apparatus and method

An interferometry system for a measuring a surface profile of a measurement object, the interferometry system comprising:

• a broadband infrared source which during operation generates broadband infrared radiation comprising central wavelengths greater than about 1 micron, the broadband infrared radiation having a coherence length of less than 100 microns;
• a scanning interferometer which during operation directs a first infrared wavefront along a reference path and a second infrared wavefront along a measurement path contacting the measurement object, and, after the second wavefront contacts the measurement object, combines the wavefronts to produce an optical interference pattern, the first and second infrared wavefronts being derived from the broadband infrared radiation;
• a detector producing data in response to the optical interference pattern;
• and
• a controller which during operation causes the scanning interferometer to vary the optical path difference between the reference and measurement paths and analyzes the data as a function of the varying optical path difference.

An interferometry system for a measuring a thickness profile of a measurement object relative to a reference object, the interferometry system comprising:

• a broadband infrared source which during operation generates broadband infrared radiation comprising central wavelengths greater than about 1 micron;
• a scanning interferometer which during operation directs a first infrared wavefront along a reference path passing through the reference object and a second infrared wavefront along a measurement path passing through the measurement object, and subsequently combines the wavefronts to produce an optical interference pattern, the first and second infrared wavefronts being derived from the broadband infrared radiation;
• a detector producing data in response to the optical interference pattern;
• and
• a controller which during operation causes the scanning interferometer to vary the optical path difference between the reference and measurement paths over a range larger than the coherence length of the broadband source and analyzes the data as a function of the varying optical path difference.

An interferometry system for a measuring a thickness profile of a measurement object relative to a reference object, the interferometry system comprising:

• a broadband infrared source which during operation generates broadband infrared radiation comprising central wavelengths greater than about 1 micron and having a coherence length less than about 100 microns;
• a scanning interferometer which during operation directs a first infrared wavefront along a reference path passing through the reference object and a second infrared wavefront along a measurement path passing through the measurement object, and subsequently combines the wavefronts to produce an optical interference pattern, the first and second infrared wavefronts being derived from the broadband infrared radiation;
• a detector producing data in response to the optical interference pattern;
• and
• a controller which during operation causes the scanning interferometer to vary the optical path difference between the reference and measurement paths over a range larger than the coherence length of the broadband source and analyzes the data as a function of the varying optical path difference.

A method for measuring the profile of a surface of a measurement object, wherein the surface appears rough at visible wavelengths, the method comprising:

• providing broadband radiation for which the surface appears specular;
• directing a portion of the broadband radiation to reflect from the surface of the measurement object;
• directing another portion of the broadband radiation to reflect from a reference object;
• combining the reflected portions to form an optical interference pattern on a camera for each of multiple relative positions of the measurement object and a reference object, wherein optical path differences defined by the multiple relative positions of the measurement and reference objects span a range larger than the coherence length of the broadband radiation;
• and
• determining the surface profile based on the optical interference patterns.

A method for measuring the surface profile of a measurement object comprising:

• providing broadband radiation comprising central wavelengths greater than about 1 micron and having a coherence length of less than about 100 microns;
• directing a portion of the broadband radiation to reflect from the measurement object;
• directing another portion of the broadband radiation to reflect from a reference object;
• combining the reflected portions to form an optical interference pattern on a camera for each of multiple relative positions of the measurement object and a reference object;
• and
• determining the surface profile based on the optical interference patterns.

A method for measuring the thickness profile of a measurement object relative to a reference object comprising:

• providing broadband radiation comprising central wavelengths greater than about 1 micron and having a coherence length of less than about 100 microns;
• directing a portion of the broadband radiation through the measurement object;
• directing another portion of the broadband radiation through the reference object;
• combining the portions to form an optical interference pattern on a camera for each of multiple relative positions of the measurement object and a reference object;
• and
• determining the thickness profile based on the optical interference patterns.