Low-intensity illumination for lensless digital holographic microscopy with minimized sample interaction

Area of Science:

• Biomedical Optics
• Microscopy
• Digital Holography

Background:

• Laser light exposure can damage live cells during optical microscopic imaging.
• Traditional methods to reduce damage, like lower intensity illumination, compromise image quality (resolution, noise).
• Label-free coherent digital holography is sensitive to laser-induced artifacts.

Purpose of the Study:

• To investigate the feasibility of lensless digital holographic microscopy (LDHM) in the low photon budget (LPB) regime.
• To enable high-resolution imaging of live cells with minimized laser-sample interaction.
• To assess image quality and resolution under LPB conditions.

Main Methods:

• Utilized low-cost, off-the-shelf components for LDHM setup.
• Operated LDHM in the low photon budget (LPB) regime, using illumination powers as low as 7 µW.
• Employed numerical denoising techniques to mitigate camera shot noise inherent to LPB imaging.
• Validated reconstructions using USAF 1951 amplitude sample and phase resolution test targets.

Main Results:

• LPB illumination (down to 7 µW) did not degrade contrast or resolution in phase and amplitude reconstructions.
• Numerical denoising effectively minimized hardware camera shot noise.
• High-quality, high-resolution optical complex field reconstruction was achieved for live glial restricted progenitor cells.
• Demonstrated the ability to image challenging, strongly absorbing and scattering biomedical samples.

Conclusions:

• Severely limiting the photon budget in LDHM is a viable approach for live cell imaging.
• This method minimizes sample interaction while maintaining high image quality and resolution.
• The technique offers potential for high-throughput cell culture imaging with improved signal-to-noise ratio and large fields-of-view.