Dynamic control of polarization mismatch and coma aberrations in rod-GRIN assemblies.

We describe the use of stacked electrically tunable liquid crystal lenses (TLCLs), along with rod gradient index (GRIN) fixed focus lenses, for endoscopic applications. Architectural and driving conditions are found for the optimization of total aberrations of the assembly. Particular attention is devoted to the coma and polarization aberrations. The coma aberration is reduced by stacking two TLCLs with "opposed" pre-tilt angles (all molecules are in the same plane), and then two such doublets are used with cross oriented molecules (in perpendicular planes) to reduce the polarization dependence. The obtained adaptive rod-GRIN lens enables a focus scan over 80µm (with exceptionally low RMS aberrations ≤0.16µm), making possible the high-quality observation of neurons at various depths.

Miniaturized microscope for non-invasive imaging of leukocyte-endothelial interaction in human microcirculation.

We present a miniature oblique back-illumination microscope (mOBM) for imaging the microcirculation of human oral mucosa, enabling real-time, label-free phase contrast imaging of individual leukocytes circulating in the bloodstream, as well as their rolling and adhesion on vascular walls-the initial steps in leukocyte recruitment that is a hallmark of inflammation. Using the mOBM system, we studied the leukocyte-endothelial interactions in healthy and locally inflamed tissue and observed drastic changes in leukocyte movement (velocity and displacement profile). Our findings suggest that real-time imaging of leukocyte dynamics can provide new diagnostic insights (assessment of inflammation, temporal progression of disease, evaluation of therapeutic response, etc.) that are not available using conventional static parameters such as cell number and morphology.

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

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.