We consider frequency‐doubling image conversion of a brilliant object by self‐interaction of its radiation within a nonlinear material. We have demonstrated that by placing the nonlinear material in the image plane of a lens, high‐resolution, three‐dimensional image conversion can be achieved, whereas for other positions of the nonlinear material crosstalk noise can be so severe as to make the resultant image unrecognizable. We have developed a theory of this type of image conversion which uses the formalism of Fourier optics. This theory is applied to a case which is very similar to more general image converters and this case is experimentally demonstrated.