Fig. 2.

(a) Principle of operation: A glass plate (GP) was introduced into the imaging beam and the resulting two imaging sub-beams (A, B) are incident on a capillary tube. (b) OCT Doppler overlay image generated from the plane cross-sectioning the capillary tube showing the three sub-images (AA, BB, AB/BA) generated from the two delay-encoded sub-beam paths (A, B). The illuminating sub-beams have different effective angles of incidence resulting in different Doppler images. (c) Diagram defining the vectors, angles and velocities used for absolute flow calculation (see description in text).