Fig. 1.

a) Schematic diagram of the instrument and noncontact and contact probes. The DCS setup consists of 785 nm laser, single photon counting detector (SPCD), correlator (Corr), and laptop (PC). Laser light is split in two; one for contact probe, and another for noncontact probe. In the probe tip, the larger red dot at the center represents source fiber, and other three black dots represent detector fibers. The separations between source and detector fibers were 3mm. The open circle is the source position. Lens setup for noncontact probe is also shown with f1 = 60mm, f2 = 40mm. Filter was 785/10 nm band-pass. b) Picture of the noncontact probe.