|
MICRO-ENDOSCOPE :
The novel micro-endoscopic system we present was designed and simulated using Zemax optical software in order to predict some key imaging parameters such as the magnification, the field of view, the resolution, the focal shift, etc. Classical epi-fluorescence (reflected light illumination) imaging configuration was considered. SolidWorks engineering software was used for the mechanical approach/simulations. The mechanical parts of the micro-endoscope were mainly printed using a 3D laser printer (hard plastic) at the theoretical resolution of 25µm or directly fabricated and assembled in the mechanical atelier.
TUNEABLE LIQUID CRYSTAL LENSES :
We used an optimized modal lens approach to design polarization-insensitive optical probe that requires relatively low driving voltages to perform endoscopic depth imaging. For a single LC lens a thin weakly conductive layer of ZnO film sheet resistance was cast over the hole-patterned electrode to form a the control layer used to generate a gradually varying electric field profile along the z-axis that was applied to the NLC layer. Two perpendicularly oriented double-layer NLC “half” lenses were required to form a custom four-layers design of the TLCL (tuneable liquid crystal lens).
GRIN PROBE :
To enable depth imaging our 4 layer TLCL was optically coupled to the imaging probe composed of 2 different GRIN lenses : imaging GRIN lens (high NA) and a coupling GRIN lens (low NA) which were glued together using index matched optical adhesive.
RESULTS :
Combination of the TLCL and the GRIN probe enabled a focal shift of approximately 90 ± 3µm while maintaining a constant magnification and a lateral resolution of ≈ 1µm. The potential of our system to visualise and differentiate small neuronal structures at variable focal depth was tested by imaging neurons, dendrites and also spines in thick brain sections and also in a free behaving mouse (Flex-GFP), in deep regions of the brain such as subventricular zone (SVZ) and rostral migratory stream (RMS).
|
