The objective of synthetic array heterodyne detection is to isolate regions of a large area detector surface into virtual pixels.
The second problem synthetic array detection solves arrises, not in pixel imaging but when the signal is not spatially coherent across the surface of the detector.
In this case, the beat frequencies arising are differently phased across the detector surface and these destructively interfere producing a low signal output.
For any finite size prism you cannot get enough dispersion to create resolved (non-overlapping beamlets) that differ by less than a megahertz.
The lasers needed for this must be of sufficiently narrow spectral purity that they can interfere coherently with the signal source.
In particular this approach allows the use of inexpensive, high power or pulsed lasers as sources because no frequency control is required.
This method scales to larger numbers of pixels since AOD's with thousands of resolvable spots (each with a different frequency) are commercially available.
One can also independently change the Heterodyne gain on each pixel individually simply by making the LO beamlet more or less strong.
In the case of imaging, the signals must not be changing faster than the Nyquist time constant implied by the difference frequency between adjacent pixels.
(For non-imaging applications—such as when one is simply trying to collect more light but is limited by the spatial incoherence—that aliasing is not important since it does not change the incoherent sum of the pixels.)