Handbook of Biomedical Optics

222 Handbook of Biomedical Optics

collection bers in dierent spatial locations relative to a 2 mm

diameter sapphire ball lens, excitation light is refracted at dif-

ferent incidence angles compared to the tissue surface, which

allows for depth sensitivity in measurements. A view of the

probe and ball lens in “shallow” mode is shown in Figure 11.4a.

A picture of the probe using the “shallow” bers illuminating a

cuvette with Rhodamine dye is shown in Figure 11.4b demon-

strating the highly divergent source rays.

Experiments using water and tissue phantoms have con-

rmed that the “shallow” channel provides a signicant increase

in sensitiv ...