Figure 2.

Schematic of the steps followed for the extraction of the OI for a model SHG image. Initially, the 2D Fourier transform of the image shown in panel (a) is calculated, as shown in (b). The coordinates of the Fourier image are transformed so that the spatial frequency is lowest at the origin and increases as we move toward the image edges (c). The frequency components along different orientations are represented by the amplitude along a specific angle θ from the horizontal (d). The information in each map can be compacted into a line plot of the spatial frequency averaged intensity as a function of the angle θ (e). From such plots the OI of each image is calculated.