Figure 2 includes a simplified schematic representation of the optical subsystem of a 3D OCT system. This system is based partly on the same principles as those of the prior system. However, there are several important differences:
- Light from the source is fed through a more-complex fiber-optic subsystem, not only to a photodiode but to three single-mode optical fibers on a probe. Light emerging from the tips of these three fibers illuminates the specimen and creates a 3D interference pattern in the specimen.
- Light scattered from the specimen is collected and sent to the photodetector by a wider, multimode optical fiber. The probe containing the illuminating single-mode fibers and the light-collecting multimode optical fibers is significantly smaller and more rugged, relative to a lens-containing probe in a prior OCT system.
- Instead of utilizing lenses and a piezoelectric actuation of a reference mirror to effect scanning in Z and focusing in conjunction with mechanical scanning in X and Y, the system utilizes a combination of (1) amplitude modulation of the light in the three illuminating optical fibers and of a portion of the source light sent directly to the photodetector, (2) nonlinear detection, and (3) an advanced signal-processing technique that, among other things, exploits the 3D nature of the interference pattern in order to obtain (4) a 3D point-spread function that affords localization in X, Y, and Z. In principle, because mechanical scanning is no longer necessary, it is possible to achieve scanning at a video frame rate.
This work was done by Mikhail Gutin, Xu- Ming Wang, and Olga Gutin of Applied Science Innovations, Inc. for Glenn Research Center.
Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center, Innovative Partnerships Office, Attn: Steve Fedor, Mail Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135. Refer to LEW-18352-1.