Probe design and characterization for a multimode fiber based endomicroscope
Date Issued
2014
Date
2014
Author(s)
Tsen, Chen-Feng
Abstract
In the presented thesis, we have successfully demonstrated sub-micron fluorescence imaging using our multimode fiber-based endomicroscope. Multimode fibers have a large number of degrees of freedoms in a small diameter, and have high numerical aperture which provides high resolution to an endoscopic system. However, light gets scrambled while propagating through a multimode fiber due to the intermodal coupling of the propagating modes. By using digital phase conjugation, we compensate for the scrambling problem of light propagating through a multimode fiber and generate a high contrast reconstructed focus spot at the distal end of the fiber. The digital implementation enables the dynamic control of light transmission through the multimode fiber and enables the endomicroscope to perform the scanning without mechanical scanners. In order to acquire images deep inside biological tissues, an ultrathin rigid needle probe is required. We have successfully fabricated the forward-viewing needle probe with the 26 gauge clinical needle of which the outer diameter is 450 μm. The sub-micron resolution has been obtained by distinguishing two adjacent 1 μm fluorescence beads with the needle probe. We also designed a high numerical aperture (NA>0.4) ultrathin (D=250 μm) side-viewing imaging probe by attaching GRIN lenses and a prism mirror at the distal end of the multimode fiber. The simulation results shows that with our side-view imaging probe design, the resolution of 0.8 μm could be obtained at 532 nm. The plots of the numerical aperture versus the off-axis distance and working distance of the probe has been shown, giving us the information on the field of view.
In conclusion, a high-resolution scanner-free multimode endomicroscope has been presented. Sub-micron resolution has been achieved by imaging 1 μm fluorescence beads with the forward-view needle probe. An ultrathin, high numerical aperture side-viewing probe is also designed.
Subjects
數位光學相位共軛
波前塑型技術
多模態光纖內視鏡
數位全像術
Type
thesis
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