Electrically switchable lens exploits holography and diffraction

17 Jun 2002

DigiLens, of Sunnyvale, California, US, has developed a liquid crystal-based lens that provides customized diffraction gratings depending on which of its layers are 'switched on'.

The application specific integrated lens (ASIL) has different computer holograms imaged onto each layer. Each hologram corresponds to a different diffraction grating, enabling different optical effects.

One of the main applications for the lenses will be colour filters and magnifying optics for microdisplays, tiny displays on silicon chips. These light valves are very small and light but the conventional optics to accompany them are bulky and noisy.

Jonathan Waldern, DigiLens' founder and CEO, says that one of the main limiting factors for diffractive gratings in colour filtering applications is that they tend to transmit only a very narrow band of wavelengths. ASIL allows diffraction gratings that transmit red, blue or green light to be layered on top of each other. These layers can be switched on and off in turn, at frequencies greater than 85 hertz, giving the full spectrum of colour with no flicker. Waldern says that any optical effect that can be produced with conventional lenses can be written onto ASIL.

The current ASIL prototypes are mounted on glass substrates that are just 0.2 millimetres thick. The company is now developing the devices on plastic thin films. Waldern says that the lightness of the lens is particularly important for near eye and handheld applications such as cell phone displays or mobile computing.

DigiLens has been working closely with microdisplay manufacturers. Microdisplays are expected to sell for about USD 20 or 25 and ASILs will probably have similar prices. Waldern hopes that ASIL will be in full production in the second quarter of 2000.