Dual-wavelength slightly off-axis digital holographic microscopy

Area of Science:

• Optics and Photonics
• Microscopy Techniques
• Metrology

Background:

• Digital holographic microscopy (DHM) is a powerful tool for 3D imaging.
• Traditional DHM faces limitations in axial measurement range due to phase ambiguity.
• Extending the measurement range is crucial for various applications.

Purpose of the Study:

• To introduce a dual-wavelength digital holographic microscopy technique.
• To enhance the axial measurement range of DHM without phase ambiguity.
• To demonstrate real-time measurement capabilities.

Main Methods:

• Utilizing a dual-wavelength configuration with a slightly off-axis setup.
• Synthesizing a beat wavelength (157 nm separation) to extend the unambiguous axial range.
• Employing a Bayer mosaic filtered color CCD camera for high wavelength selectivity and real-time acquisition.

Main Results:

• Achieved an extended axial measurement range in the micrometer scale.
• Demonstrated real-time measurement of specimens.
• Validated the technique's practicability through experiments on a vortex phase plate and a rectangular phase step.

Conclusions:

• The proposed dual-wavelength DHM effectively overcomes the axial range limitation of conventional DHM.
• The technique offers a practical solution for real-time, high-resolution 3D metrology.
• This advancement has potential applications in fields requiring precise microscopic measurements.