EmVision Multi-Spectroscopy Fiber-Optic Probe
Multi-Spectroscopy Probe Design.
The probe design is described in detail in US patent 8,175,423 and US patent 8,702,321. An illustration of the probe is shown in the following image.
The EmVision multi-spectroscopy probe enables efficient excitation and collection of undistorted diffuse reflectance spectra (DRS) and intrinsic fluorescence spectra (IFS) in the UV/visible wavelength region, as well as Raman spectra at very high sensitivity in the near IR. The finished probe diameter is 2.1mm.
The multi-spectroscopy probe provides three 200 micron core fibers for DRS and IFS. This design allows the measurement areas of the different spectroscopies to overlap each other, i.e. sampling at the same location.
The Raman portion of the probe uses seven low hydroxyl (OH) content 300 micron core, 0.22 NA collection fibers. A donut shaped long pass filter is positioned in front of these seven fibers, which rejects the laser light and passes the Raman light from the sample. These seven fibers surround a stainless steel tube inside which is the laser delivery fiber assembly. The laser delivery fiber is a 200 micron core low OH, 0.22 NA fiber which has a band-pass filter positioned in front of it. The two piece converging lens is made of a plano convex 2mm diameter curvature sapphire back portion (the high refractive index bends the light sharply), with a flat front portion of 1mm thick plano magnesium fluoride which has virtually no Raman signature. This configuration allows overlap of the focus of the excitation source light and the region of collected light at the sample without interference from the magnesium fluoride. This is discussed in detail in US patent 8,175,423. An important aspect of the Raman portion of the probe is that the fibers are moved off the optical axis of the front lens allowing both accommodation of the three 200 micron core fibers used for DRS and IFS, and refraction of the light towards the three 200 micron fibers. This bending of the light creates (partial) overlap of the Raman, DRS and IFS spots.
The DRS and IFS portion of the probe uses three 200 micron core fibers arranged in a triangle as illustrated in the figure. One 200 micron fiber is a high OH fiber for UV light delivery for fluorescence excitation, while the two other 200 micron fibers are low OH fibers for visible light collection. These three fibers fit in the gap of the 300 micron Raman collection fibers that surround the stainless steel tube housing the Raman laser excitation fiber. The fibers then pass through holes that have been drilled in the long pass donut filter. This allows all DRS and IFS data to be collected in the same manner as has been normal practice using a standard fiber bundle probe.
The probe uses epoxy to bond the required individual components together. The fibers, lens and other components are placed inside a stainless steel tube with a 2.1mm OD.
Exploded View of the Multi-Specroscopy Fiber-Optic Probe
The above image shows the exploded view of the probe distal tip illustrating the Raman laser excitation region and how the light is angled toward the 200 micron fiber bundle used for DRS and IFS. Only the Raman excitation light is illustrated, but the Raman collection region is altered similarly to the laser light.
View of Probe Distal Tip
Front view of the probe distal end illustrates the fiber positioning in the probe. The fibers shown in blue are 300 micron core, low OH, 0.22 NA fibers used for Raman collection. The fiber shown in red is a 200 micron core, low OH, 0.22 NA fiber used for Raman excitation. The fiber shown in yellow is a 200 micron core, high OH, 0.22 NA fiber used for diffuse reflectance and fluorescence excitation, and he fibers shown in green are 200 micron core, low OH, O.22 NA fiber used for diffuse reflectance collection.