Nontranslational three-dimensional profilometry by chromatic confocal microscopy with dynamically configurable...

Area of Science:

• Optical Metrology
• Microscopy Techniques
• Surface Characterization

Background:

• Traditional 3D surface measurement often relies on mechanical scanning, which can be slow and introduce errors.
• Confocal microscopy offers high resolution but typically requires mechanical sample or objective movement for depth profiling.

Purpose of the Study:

• To develop and validate a confocal microscope profilometer capable of 3D quantitative measurements without mechanical translation.
• To assess the system's resolution, accuracy, and scanning speed using various objective lenses.

Main Methods:

• The system integrates chromatic depth scanning with a diffractive optical element and a digital micromirror device for configurable transverse scanning.
• Measurements were performed using objective lenses including 40x, 60x, and 100x.
• The system's performance was evaluated on a four-phase-level diffractive element and an integrated-circuit chip.

Main Results:

• With a 100x objective, the microscope achieved stable measurements over a 320 µm x 240 µm area with a depth resolution of 0.39 µm at a 3-Hz scan rate.
• The longitudinal field of view was 26.4 µm, and the full width at half maximum (FWHM) of the longitudinal point-spread function was 0.99 µm.
• 3D measurements demonstrated resolution and accuracy equivalent to conventional mechanical scanning methods.

Conclusions:

• The developed confocal microscope profilometer provides efficient and accurate 3D surface measurements without mechanical scanning.
• This non-contact, high-resolution technique is suitable for characterizing micro-optical elements and integrated circuits.
• The system offers a promising alternative to traditional profilometry for advanced surface metrology.