Fig. 1: Concept of probe-beam multiplexing in the spatial-frequency and time domains.

a An object (here, an apple) is uniformly illuminated in real space. The frequency content of the resulting image is band-limited and is mainly localized in the central region of Fourier space. b Illuminating the same object with a sinusoidal intensity modulation produces two ‘image copies’ of the object in two unexploited regions, symmetrically located in Fourier space with respect to the origin. Their actual locations (i.e. the distance from the origin) depend on the spatial-frequency k of the modulation pattern. c By varying the pattern orientations, ‘image copies’ can be moved to different non-overlapping regions in the Fourier domain, thus allowing for the implementation of a multiple-illumination scheme without any mutual interference. d By judiciously implementing multiple spatially modulated and temporally delayed patterns, a dynamic scene can be imaged. Despite being overlapped in the multiplexed image captured by the camera, these frames are well separated in Fourier space, and can be extracted and recovered computationally.