Fig. 1.

(a) Diagram of qOBM assembly. Four LEDs, two red (630 nm) and two green (530 nm), sequentially illuminate the target from some distance off axis and at some angle (45° in this work), and an image is produced with an inverted microscope. (b) Top-down view of imaging apparatus indicating the entry positions of the four LEDs. (c) Representative photon visitation in the source-detector plane. (d) Example angular distribution overlaid on a unit sphere, which is smoothed and projected onto a flat surface to produce (e) the effective source distribution in spatial frequency space. (f) The effective optical transfer function of the difference image.