We demonstrate an imaging diffractive optical element (DOE) that is free of coma and
other first-order aberrations. The DOE was holographically recorded on a properly
curved surface and thereby satisfies the Abbe sine (aplanatic) condition. Experimental
results as well as numerical ray-tracing simulations indicate that the off axis aberrations
of the curved DOE are much smaller than those of a flat DOE. Because the recording
of the DOE involves a single step and only readily available: spherical and plane
waves, it is extremely simple. (C) 2001 Optical Society of America.