SNR compensation for 3D imaging of turbid biological samples by two-photon fluorescence excitation
Abstract
We present a pre-detection technique for compensating the loss of detected fluorescence signal in two-photon fluorescence (TPF) imaging through an optically-thick biological sample. The signal-to-noise ratio (SNR) of the fluorescence image from deeper portions of the sample decreases due to multiple scattering caused by the inhomogeneities along the propagation paths. By modulating the average input power of a near-infrared mode-locked laser, the quadratic increase of the localized two-photon fluorescence intensity with respect to the excitation intensity is utilized to maintain the SNR of the axial images at different focal plane positions.