A prototype fiber-based imaging spectrometer was developed to provide snapshot hyperspectral imaging tuned for biomedical applications. The system is designed for imaging in the visible spectral range from 400 to 700 nm for compatibility with molecular imaging applications as well as satellite and remote sensing. An 81×96 pixel spatial sampling density is achieved by using a custom-made fiber-optic bundle. The design considerations and fabrication aspects of the fiber bundle and imaging spectrometer are described in detail. Through the custom fiber bundle, the image of a scene of interest is collected and divided into discrete spatial groups, with spaces generated in between groups for spectral dispersion. This reorganized image is scaled down by an image taper for compatibility with following optical elements, dispersed by a prism, and is finally acquired by a CCD camera. To obtain an (x,y,λ) datacube from the snapshot measurement, a spectral calibration algorithm is executed for reconstruction of the spatial–spectral signatures of the observed scene. System characterization of throughput, resolution, and crosstalk was performed. Preliminary results illustrating changes in oxygen-saturation in an occluded human finger are presented to demonstrate the system’s capabilities.
We present the development of a 5 mm, piezo-actuated, ultrafast laser scalpel for microsurgery with a capability to deliver energies in excess of 1 μJ per pulse. Having previously established that the maximum energy deliverable was limited by cladding damage in photonic badgap fibers, we utilized a large, 35μm cored inhibited-coupling Kagome fiber that allowed the delivery of micro-Joule energy femtosecond pulses. To maintain diffraction limited performance over the entire scan range of the piezo-actuated fiber tip, special objective lenses were developed and manufactured out of a high-refractive index Zinc Sulfide (ZnS) crystal. The probe was packaged in hypodermic 304SS stainless steel with a form factor minimizing in-line configuration. The probe’s performance was tested via metal and tissue ablation studies, characterizing highspeed ablation parameters and uniformity of ablation over the scan area. Additionally, we studied the nonlinear performance of ZnS and Calcium Fluoride (CaF2) as materials for refractive optics and determined the maximum energy deliverable through our probe using these optical materials. The high energy delivery through the probe system should allow for fast and effective tissue ablation.
We present a proof-of-principle prototype of a fiber-based snapshot spectrometer to provide high spatial and spectral sampling for biomedical application such as cell signaling or diagnostics. An image is collected by a custom fiber bundle and then divided into spatial groups with spaces in between for dispersion. The image is later scaled down by an image taper (to scale down the image size and allow smaller optical components), dispersed with a prism and captured by a CCD camera. An interpolation algorithm is used to locate each wavelength and reconstruct the image for each spectral channel. The fiber bundle is fabricated by aligning multi-mode bare fiber ribbons as matrix, gluing together in Teflon molds, laser cutting and polishing. We present preliminary finger occlusion results obtained with the spectrometer where the oxy- and deoxy-hemoglobin spectrum could be differentiated.
A miniature laser ablation probe relying on an optical fiber to deliver light requires a high coupling efficiency objective with sufficient magnification in order to provide adequate power and field for surgery. A diffraction-limited optical design is presented that utilizes high refractive index zinc sulfide to meet specifications while reducing the miniature objective down to two lenses. The design has a hypercentric conjugate plane on the fiber side and is telecentric on the tissue end. Two versions of the objective were built on a diamond lathe—a traditional cylindrical design and a custom-tapered mount. Both received an antireflective coating. The objectives performed as designed in terms of observable resolution and field of view as measured by imaging a 1951 USAF resolution target. The slanted edge technique was used to find Strehl ratios of 0.75 and 0.78, respectively, indicating nearly diffraction-limited performance. Finally, preliminary ablation experiments indicated threshold fluence of gold film was comparable to similar reported probes.