Annular Beam Shaping in Multiphoton Microscopy to Reduce Out-of-Focus Background

Figure 1

Schematic illustration of the concept of annular laser beam to reduce out-of-focus signal in MPM for the two conditions (a) where Gaussian beam profile is implemented and (b) for annular beam illumination. The figure illustrates the hypothetical relative contribution of fluorescence signal, , as a function of depth, . While comparing conditions given equal photon fluences in the focal region, the Gaussian illumination (a) is expected to generate elevated levels of out-of-focus signal from the incoming planes where the laser power is at a maximum compared to annular illumination (b).