  Forward-viewing endoscopic optical coherence tomography (OCT) provides 3D
imaging in vivo, and can be combined with widefield fluorescence imaging by use
of a double-clad fiber. However, it is technically challenging to build a
high-performance miniaturized 2D scanning system with a large field-of-view. In
this paper we demonstrate how a 1D scanning probe, which produces
cross-sectional OCT images (B-scans) and 1D fluorescence T-scans, can be
transformed into a 2D scanning probe by manual scanning along the second axis.
OCT volumes are assembled from the B-scans using speckle decorrelation
measurements to estimate the out-of-plane motion along the manual scan
direction. Motion within the plane of the B-scans is corrected using image
registration by normalized cross correlation. En-face OCT slices and
fluorescence images, corrected for probe motion in 3D, can be displayed in
real-time during the scan. For a B-scan frame rate of 250 Hz, and an OCT
lateral resolution of approximately 20 micrometers, the approach can handle
out-of-plane motion at speeds of up to 4 mm/s.
