We have a series of patents related to the Moiré Diffractive Optical Elements (MDOEs):

MDOEs are pairs of diffractive optical elements which can act as tunable Fresnel lenses, axicons or other optical elements upon mutual rotation.



Short  Demo Video
 (AVI, ~40MB)




Two specially designed diffractive optical elements (DOEs) are placed very closely behind each other. A rotation of one element around the central axis leads to a Moiré pattern which determines the optical properties of the joint DOE.

Optical elements with properties that are continuously adjustable by a mutual rotation include:

  • varifocal diffractive lenses
  • flat zoom lenses
  • axicons with a variable refractive power (for applications as beam couplers in fiber optics),
  • continuous phase shifters (for applications in interferometers or frequency sideband generation),
  • spiral phase plates with a variable helical index (for holographic optical tweezers to produce doughnut beams or for spiral phase contrast in optical microscopy).

More details on MDOEs

Application scenarios for varifocal Fresnel lenses:  Advantages of MDOEs: 
  • human-eye-like imaging systems
  • lenses in environments with restricted space (cell phones etc.)
  • inspection systems (continuous distance scanning)
  • laser scan heads (fast z-control, high damage threshold)
  • collimation lenses in illumination systems (overhead projection, microscope illumination)
  • for flashlight focusing
  • for adjustable eyeglasses
  • as multi-purpose lenses for experimental setups in research laboratories, optical development, and prototyping.
  • very wide range of focal lengths adjustable with a single MDOE
  • diffraction limited point-spread-function
  • lightweight optics
  • thin (entire element can be less than 1 mm thick)
  • can be used for both, micro-optics and large scale lenses (e.g. overhead projector lenses)
  • compatible with high laser power
  • no position change of optics necessary to change the focal length
  • dispersion of diffractive element may counteract dispersion of refractive elements (e.g. when combined with a plano-convex lens).


Stefan Bernet and Monika Ritsch-Marte, "Multi-color operation of tunable diffractive lenses," Opt. Express 25, 2469-2480 (2017).

Walter Harm, Stefan Bernet, Monika Ritsch-Marte, Irina Harder, and Norbert Lindlein, Adjustable diffractive spiral phase plates, Opt. Express 23, 413-421 (2015).

Walter Harm, Clemens Roider, Alexander Jesacher, Stefan Bernet, and Monika Ritsch-Marte, "Dispersion tuning with a varifocal diffractive-refractive hybrid lens," Opt. Express 22, 5260-5269 (2014).

Stefan Bernet, Walter Harm, and Monika Ritsch-Marte, Demonstration of focus-tunable diffractive Moiré-lenses, Optics Express, Vol. 21 Issue 6, pp.6955-6966 (2013)

Stefan Bernet and Monika Ritsch-Marte, Adjustable refractive power from diffractive moiré elements, Applied Optics  47, 3722-3730 (2008)

Coverage in Optoelectronic News World  and Laser Focus World



Grand Prix at the South Korean Inventors’ Fair KIWIE 2011 (Press release)
Supported by Transidee