| Several new resolution enhancement schemes for fluorescence microscopy are experimentally implemented and tested using beads and biological samples. The first scheme, 3D structured illumination microscopy (SIM), makes use of the simple fact that fluorescence emission is the multiplication of the illumination and the sample's dye structure. If the illumination is structured such as a sinusoidal pattern, the recorded image would contain high-frequency components encoded in terms of low frequencies. In so doing, normally undetectable high-resolution information is given a chance to appear in the observable region, and is thus made effectively detectable. We are able to double the resolution both laterally and axially of the conventional microscope with 3D SIM. The second scheme, called I5S, also uses structured illumination, but with a Sagnac-like interferometer setup consisting of two opposing objective lenses used for illumination and fluorescence detection. Interference in both illumination, which gives rise to more complicated structured illumination pattern than 3D SIM, and detection can be achieved. The combined interferometric effect is seven-fold enhancement in axial resolution as well as doubled lateral resolution. Finally, we introduce a more complicated I5S scheme in which both emission wavefronts, instead of just one of them, are recorded by two CCD cameras simultaneously. The complementary phase relationship between the two wavefronts can be utilized in estimating and then correcting the phase error often difficult to avoid in I5S experiments. |
