
Second Harmonic Generation Imaging184
to OCA with refractive index of 1.51 and axial resolution of 1.5 and 2.0 μm at depths of 40 and 80 μm,
respectively. A striking contrast is seen with oil immersion objective where the sample cleared with an
OCA with refractive index of 1.51 showed virtually no change in axial resolution over the same depth
(Figure 8.11b). By matching all the refractive indices, Young etal. [42] demonstrated the improvement of
both the imaging depth and axial resolution in kidney tissue over the entire working distance (150 μm)
of a 60× NA1.4 oil immersion objective.
8.8 Alternative Investigation of Optical Clearing:
A