There is provided an imaging device capable of improving the image quality of a reconstructed image in lensless imaging, and a method for operating the imaging device. In lensless imaging, a selection filter is provided that, for each of a plurality of regions into which an imaging surface on the imaging element is divided, allows only the modulated light having optical characteristics that are orthogonal to each other between the regions adjacent to each other, to pass through. With a sub-area set for each selection filter as a unit, the modulation mask converts the incident light into modulated light having optical characteristics corresponding to the selection filter based on at least one of polarization and spectroscopy. The present disclosure can be applied to an imaging device.