Interferometer with multiple wavelength sources of different coherence lengths

A method for measuring surface characteristics of an object in a single shot, the method comprising:

• providing simultaneous radiation to the object that is positioned in a test arm of an interferometer, the radiation including light from at least three light sources including:
• a first laser light source emitting radiation at a first center wavelength,
• a second laser light source emitting radiation at a second center wavelength, and
• a broadband light source emitting radiation in a range of wavelengths that is different from emission wavelengths of the first and the second laser light sources, the radiation emitted by the broadband light source having a coherence length that is smaller than coherence lengths of the light emitted by each of the first and the second laser light sources;
• imparting at least three different phase shifts to the light that is emitted by each of the at least three light sources and is received at an image plane of the interferometer;
• simultaneously measuring intensity values associated with a plurality of interferograms formed at the image plane due to interference of light received from the at least three light sources;
• and
• computing a surface roughness and a depth value of the object based on the measure intensity values.

An optical interferometer for measuring surface characteristics of an object, comprising:

• at least two laser sources configured to operate at a first and a second center wavelength, respectively;
• a broadband source configured to operate at a range of wavelengths outside of the operating range of the at least two lasers;
• a phase mask array and a color filter arranged, respectively, to impart at least three different phase delays and provide spectral filtering corresponding to the emitted radiation from the at least two laser sources and the broadband source;
• and
• a pixelated sensor device to simultaneously measure intensity values associated with a plurality of interferograms formed due to interference of light from the at least two laser sources and due to interference of light from the broadband source after propagation through the phase mask array and the color filter, wherein the measured intensity values associated with the broadband source enable a determination of a surface roughness, and the measured intensity values associated with the at least two laser sources enable a determination of a surface topography.

An optical interferometer for measuring surface characteristics of an object, comprising:

• a test arm and a reference arm arranged to receive light from at least three light sources that include:
• at least two laser sources configured to operate at a first and a second center wavelength, respectively, and
• a broadband source configured to operate at a range of wavelengths outside of the operating range of the at least two lasers, wherein light from each of the at least three light sources is allowed to propagate through at least a section of the test arm, reflect from the object and reach an image plane, and light from each of the at least three light sources is allowed to propagate through at least a section of the reference arm, reflect from a reference optical component and reach the image plane;
• a phase mask array and a color filter arranged, respectively, to impart at least three different phase delays and provide spectral filtering corresponding to emitted radiation from the at least two laser sources and the broadband source;
• and
• a pixelated sensor device to simultaneously measure intensity values associated with a plurality of interferograms formed due to interference of light from the at least two laser sources and due to interference of light from the broadband source after propagation through the phase mask array and the color filter, wherein the measured intensity values associated with the broadband source enable a determination of a surface roughness, and the measured intensity values associated with the at least two laser sources enable a determination of a surface topography.