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J Biophotonics. 2017 Jun;10(6-7):762-774. doi: 10.1002/jbio.201500261. Epub 2016 Mar 8.

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

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Centre for Optics, Photonics and Lasers, Department of Physics, Engineering Physics and Optics, University Laval, 2375 Rue de la Terrasse, Quebec City, QC, Canada, G1V 0A6.
Quebec Mental Health Institute, 2601 chemin de la Canardière, Quebec City, QC, Canada, G1J 2G3.
Department of Psychiatry and Neuroscience, Faculty of Medicine, University Laval, 1050 avenue de la Médecine, Quebec City, QC, Canada, G1V 0A6.


We present a motion-free system for microendoscopic imaging of biological tissues at variable focal depths. Fixed gradient index and electrically tunable liquid crystal lenses (TLCL) were used to build the imaging optical probe. The design of the TLCL enables polarization-independent and relatively low-voltage operation, significantly improving the energy efficiency of the system. A focal shift of approximately 74 ± 3 µm could be achieved by electrically controlling the TLCL using the driving frequency at a constant voltage. The potential of the system was tested by imaging neurons and spines in thick adult mouse brain sections and in vivo, in the adult mouse brain at different focal planes. Our results indicate that the developed system may enable depth-variable imaging of morpho-functional properties of neural circuitries in freely moving animals and can be used to investigate the functioning of these circuitries under normal and pathological conditions.


adaptive 3D imaging; brain; gradient index lenses; liquid crystal lenses

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