Common-path point-diffraction phase-shifting interferometer

A common-path point-diffraction phase-shifting interferometer comprising:

• a source for providing linearly polarized light having a polarization axis;
• a partially transmitting half wave plate with a diffractive feature, said half wave plate having a fast axis that is oriented at 45 degrees to said polarization axis, wherein said partially transmitting half wave plate generates from said light, when incident thereon, an object beam and a reference beam along a common optical axis so that said object beam has a first intensity and first polarization and said reference beam has a second intensity and second polarization;
• a phase modulator oriented with its axis parallel to said polarization axis;
• and
• an adjustable polarizer for adjusting said first intensity of said object beam and said second intensity of said reference beam to be substantially equal and in the same polarization state so as to generate a near unity contrast interferogram.

A common-path point-diffraction phase-shifting interferometer, comprising:

• a light source for providing light;
• a partially transmitting half wave plate with a diffractive feature, wherein said partially transmitting half wave plate generates from said light, when incident thereon, an object beam and a reference beam along a common optical axis so that said object beam has a first intensity and first polarization and said reference beam has a second intensity and second polarization;
• a linear polarizer positioned between said light source and said partially transmitting half wave plate for linearly polarizing said light along a polarization axis;
• and
• an adjustable polarizer for adjusting said first intensity of said object beam and said second intensity of said reference beam to be nearly equal and in the same polarization state so as to generate a near unity contrast interferogram.

A method of characterizing the shape of an optical wavefront, comprising the steps of:

• transmitting a beam of light through a test system;
• linearly polarizing the beam of light along a polarization axis either before or after transmitting it through the test system;
• separating said linearly polarized beam of light into an object beam and a reference beam extending along a common axis so that the object beam has a first intensity and first polarization and the reference beam has a second intensity and second polarization;
• and
• adjusting the first intensity of the object beam and the second intensity of the reference beam to be substantially equal and in the same polarization state so as to generate a near unity contrast interferogram that provides information about the shape of the optical wavefront.

A method of generating an interference pattern, comprising the steps of:

• providing a beam of linearly polarized light having a polarization axis;
• generating a first beam of light having a first intensity and first polarization and a second beam of light having a second intensity and second polarization;
• providing a shift in phase between said first beam of light and said second beam of light;
• after said shifting step, combining said first and second beams of light so that they interfere with each other to create an interference pattern, wherein said combining step involves adjusting said first intensity of said first beam and said second intensity of said second beam to be substantially equal and in the same polarization state so as to generate a near unity contrast interference pattern.

A common-path point-diffraction phase-shifting interferometer comprising:

• a source for providing linearly polarized light having a polarization axis;
• a device that generates from said light, when incident thereon, an object beam and a reference beam along a common optical axis so that said object beam has a first intensity and first polarization and said reference beam has a second intensity and second polar ion, wherein said device is not a half wave plate;
• a phase modulator oriented with its axis parallel to said polarization axis;
• and
• an adjustable polarizer for adjusting said first intensity of said object beam and said second intensity of said reference beam to be substantially equal and in the same polarization state so as to generate a near unity contrast interferogram.

A common-path point-diffraction phase-shifting interferometer, comprising:

• a light source for providing light;
• a device that generates from said light, when incident thereon, an object beam and a reference beam along a common optical axis so that said object beam has a first intensity and first polarization and said reference beam has a second intensity and second polarization, wherein said device is not a half wave plate;
• a linear polarizer positioned between said light source and said device for linearly polarizing said light along a polarization axis;
• and
• an adjustable polarizer for adjusting said first intensity of said object beam and said second intensity of said reference beam to be nearly equal and in the same polarization state so as to generate a near unity contrast interferogram.

An interferometer, comprising:

• a source of polarized light;
• a half wave plate having a pinhole that generates from said polarized light, when incident thereon, an object beam and a reference beam along a common optical axis so that said object beam has a first intensity and first polarization and said reference beam has a second intensity and second polarization;
• and
• an adjustable polarizer for adjusting said first intensity of said object beam and said second intensity of said reference beam to be nearly equal and in the same polarization state so as to generate a near unity contrast interferogram.