EmVision Lensed Fiber-Optic Probe
Raman Lensed 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 probe uses seven low hydroxyl (OH) content 300-micron core, 0.22 NA collection fibers. A donut shaped long-pass filter that rejects the laser light and passes the Raman light from the sample is positioned in front of these seven fibers. These fibers surround a stainless steel tube inside which is the laser delivery fiber assembly. The laser delivery fiber is a 300-micron core low OH, 0.22 NA fiber which has a band-pass filter positioned in front of it. The two piece converging front 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 fused silica. 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 sapphire.
The probe uses epoxy to bond the required individual components together. The fibers, lenses and other components are placed inside a 2.1mm stainless steel needle tube.
Exploded View of the Raman Lensed Fiber-Optic Probe
The above image shows the exploded view of the probe distal tip illustrating the Raman laser excitation region and how the Raman collection cone(s) are directed to a complete overlap with the laser cone at the surface of the lens. Only the Raman excitation light and one collection fiber cone is illustrated, but all the collection light is altered in the same fashion as the one illustrated. Therefore, Raman scattered light collection is from a cylindrically symmetrical region within the region of Raman excitation.
Zemax Software Ray Trace
Illustrated in red is the excitation light. The collected light is illustrated by the blue rays. Only the Raman excitation light and one collection fiber cone is illustrated, but all seven of the collection fibers light patterns are altered in the same fashion as the one shown. As can be seen from the tracing, the probe is designed to be an efficient superficial collection probe.