Spatial-domain filter enhanced subtraction microscopy and application to mid-IR imaging.

Area of Science:

• Optics and Photonics
• Microscopy Techniques
• Biomedical Imaging

Background:

• Central solid-immersion lens (c-SIL) microscopy offers potential for high-resolution imaging.
• Conventional image subtraction methods struggle with the inherent side lobes of c-SIL point-spread functions (PSFs).
• Enhancing spatial resolution in mid-infrared (mid-IR) microscopy is crucial for various scientific applications.

Purpose of the Study:

• To investigate the enhancement of spatial resolution in mid-IR c-SIL microscopy through image subtraction.
• To develop and validate a novel filtering technique to overcome limitations of conventional subtraction methods.
• To demonstrate the improved resolution capabilities for sub-wavelength particle imaging.

Main Methods:

• Experimental investigation using mid-IR c-SIL microscopy at a wavelength of 3.4 µm.
• Acquisition of two images: one with a Gaussian beam PSF and another with a centrally hollow PSF generated by a silicon π-step phase plate.
• Development and application of a spatial-domain filter optimized for the periphery of both PSFs prior to image subtraction.

Main Results:

• Successfully resolved polystyrene beads with a separation of 1.4 ± 0.1 µm in water.
• The developed spatial-domain filtering significantly improved image subtraction performance compared to conventional methods.
• Simulations indicate the method's applicability and superiority for Gaussian and doughnut beams in visible and near-IR microscopy.

Conclusions:

• Spatial-domain filtering is an effective method for enhancing spatial resolution in c-SIL microscopy via image subtraction.
• This technique overcomes the limitations imposed by strong side lobes in c-SIL PSFs.
• The developed approach has broad applicability for improving resolution in various microscopy modalities.