Optical microscopy with extended depth of field

A method is described that allows the depth of field in optical microscopy to be extended, in principle without limit, while high-resolution, diffraction-limited imaging is retained. Experimentally, an extension of more than two orders of magnitude has been achieved. The images are found to be of high optical quality, and this is borne out by theoretical predictions. The resolution is shown theoretically to be similar to that in a conventional microscope of the same numerical aperture, and for some criteria an improvement is obtained.