Adjustable refractive power from diffractive moiré elements.

We show how suitable combinations of cascaded diffractive optical elements (DOEs) can form a combined "moiré DOE" of adjustable refractive power and high diffraction efficiency. The optical power can be adjusted continuously by a mutual rotation of one DOE with respect to the other. Fresnel lenses and axicons of variable refractive power or spiral phase plates of adjustable helical charge can be realized this way.