Chromatic confocal spectral interferometry

Area of Science:

• Optics and Photonics
• Metrology
• Microscopy

Background:

• Topography measurements require precise depth sensing.
• Existing methods like spectral interferometry and chromatic confocal microscopy have limitations in range or resolution.
• A hybrid approach could overcome these limitations.

Purpose of the Study:

• To introduce and validate Chromatic Confocal Spectral Interferometry (CCSI) as a novel topography measurement technique.
• To demonstrate CCSI's capability for single-shot, high numerical aperture (NA) white-light interferometric detection.
• To show CCSI's ability to retrieve object depth position using interferometric signal phase.

Main Methods:

• Combining spectral interferometry and chromatic confocal microscopy.
• Utilizing a confocally filtered and chromatically dispersed focus for detection.
• Acquiring interferometric signals and analyzing their phase (modulation frequency) for depth retrieval.

Main Results:

• CCSI enables white-light interferometric detection with high NA in a single shot.
• The method successfully retrieves the depth position of reflecting or scattering objects.
• The depth range of the sensor is decoupled from the objective's NA due to the dispersed focus.

Conclusions:

• CCSI is a pioneering interferometric method for topography measurements.
• This technique offers a unique combination of high NA detection and depth positioning.
• CCSI advances metrology by decoupling sensor depth range from objective NA.