Abstract

With confocal imaging it is possible to obtain three-dimensional images in scattering biomedical samples¹ because of the effective suppression of out-of-focus scattered light achieved by the spatial filtering (Fig. 1). Limits of the confocal technique are reached when either (i) the ballistic light intensity, which decays exponentially with the thickness L of the scattering sample, approaches the noise level of the detection system, or (ii) the diffuse light that passes through the spatial filter becomes comparable to the intensity of the ballistic light. These limits depend on the average transport mean free path length ℓ and scattering mean free path length ℓ_s in the sample as well as on the sample structure. Imaging through a thickness L/ℓ_s ≈ 24 is possible with respect to limit (i) for illumination powers well below the damage threshold of biomedical samples and typical photodiode detectors.

© 1996 Optical Society of America