Figure 4. Demonstration of flow stream monitoring through a scattering sample.

(a) Illustration of the experimental set-up. An external single-photon-counting module (SPCM) was used to detect the excited fluorescence through the fluorescence filter. (b) A light focus was created with TRUME. (c) Photon counts recorded by the SPCM as the optical focus probed the flowing microspheres. (d) Image of the fluorescent microspheres after passing through the optical focus in the x direction. Scale bar, 10 μm.