  In recent years, image-scanning microscopy (ISM, also termed
pixel-reassignment microscopy) has emerged as a technique that improves the
resolution and signal-to-noise compared to confocal and widefield microscopy by
employing a detector array at the image plane of a confocal laser scanning
microscope. Here, we present a k-space analysis of coherent ISM, showing that
ISM is equivalent to spotlight synthetic-aperture radar (SAR) and analogous to
oblique-illumination microscopy. This insight indicates that ISM can be
performed with a single detector placed in the k-space of the sample, which we
numerically demonstrate.
