Motion-free endoscopic system for brain imaging at variable focal depth using liquid crystal lenses

Area of Science:

• Neuroscience
• Optical Engineering
• Biomedical Imaging

Background:

• Microendoscopic imaging is crucial for visualizing biological tissues at cellular resolution.
• Achieving variable focal depths in microendoscopy typically requires bulky mechanical components or complex optical designs.
• Existing methods often lack the efficiency and adaptability needed for in vivo studies of neural circuits.

Purpose of the Study:

• To develop a motion-free microendoscopic imaging system capable of variable focal depth adjustments.
• To improve the energy efficiency and operational simplicity of optical probes for biological imaging.
• To enable depth-variable imaging of neural circuitries in freely moving animals.

Main Methods:

• Utilized fixed gradient index and electrically tunable liquid crystal lenses (TLCL) to construct an optical probe.
• Designed the TLCL for polarization-independent, low-voltage operation to enhance energy efficiency.
• Achieved focal shifts by electrically controlling the TLCL with driving frequency at constant voltage.

Main Results:

• Demonstrated a focal shift of approximately 74 ± 3 µm through electrical control of the TLCL.
• Successfully imaged neurons and spines in thick adult mouse brain sections.
• Validated in vivo imaging capabilities in adult mouse brains at different focal planes.

Conclusions:

• The developed system offers a novel approach for motion-free, depth-variable microendoscopic imaging.
• This technology has the potential to significantly advance the study of neural circuit morpho-functional properties.
• The system is suitable for investigating neural circuit function in both normal and pathological conditions in freely moving animals.