Scanning Electron Microscope view of the moveable gratings used in the CDOE filter. The 0.5 cm sq CDOE area consists of hundreds of microgratings with a reflective aluminium covering, each one measuring 50 µm by 500 µm. Every second micrograting moves when a voltage is applied due to electrostatic attraction, springing back when the voltage is switched off. They move less than one micrometre (µm), which is one thousandth of a millimetre or a hundredth of a hair’s diameter.