An exemplary imaging device includes an optical sensor having an optical axis, a lens positioned to focus light from a scene onto the optical sensor, a matrix of variable-phase optical elements that are dimensioned to introduce at least two different phase delays into a wavefront of a light signal received from the scene through the lens, a housing that secures the matrix of variable-phase optical elements between the optical sensor and the lens, and a processing subsystem programmed to determine a phase difference associated with the light signal based on the at least two different phase delays. Related systems and methods are also provided.