Fig. 4.

Data processing. (a) Two-dimensional Fourier transform of the raw interferogram, whose magnitude is shown in a logarithmic scale of base 10. (b) Cropping the spatial frequencies using masks defined by the physical numerical aperture. The circles are centered at the object zero frequency location corresponding to the illumination angle. Blue dots show the center points. (c)-(e) Phase maps after unwrapping, which correspond to + θ, normal, -θ beams, respectively. Scale bar is10 μm.