1. A method for obtaining a focused image of an object comprising the steps of: illuminating said object; obtaining amplitude and phase information of a wavefront of said illumination emanating from said object, in an arbitrary plane at which said wavefront does not necessarily generate a focused image; and using processing circuitry: calculating by means of mathematical solutions of the propagation properties of said wavefront, the form of the wavefront at a series of additional planes down the propagation path of said wavefront; and determining at which of said additional planes said wavefront has the form of a focused image.