New chip can turn your cell phone into a projector

Washington: Imagine giving a presentation that is projected on a conference room wall via your cell phone! Such a technology may be on its way, thanks to a new light-bending silicon chip developed by researchers.

The light-bending silicon chip from at California Institute of Technology (Caltech) researchers acts as a lens-free projector and could one day end up in your cell phone. The new chip uses an integrated optical phased array (OPA) to project the image electronically with only a single laser diode as light source and no mechanically moving parts.

Ali Hajimiri and his colleagues could bypass traditional optics by manipulating the coherence of light - a property that allows the researchers to "bend" the light waves on the surface of the chip without lenses or the use of any mechanical movement. Using a series of pipes for the light - called phase shifters - the OPA chip similarly slows down or speeds up the timing of the waves, thus controlling the direction of the light beam.

To form an image, electronic data from a computer are converted into multiple electrical currents; by applying stronger or weaker currents to the light within the phase shifter, the number of electrons within each light path changes - which, in turn, changes the timing of the light wave in that path. The timed light waves are then delivered to tiny array elements within a grid on the chip. The light is then projected from each array in the grid, the individual array beams combining coherently in the air to form a single light beam and a spot on the screen. As the electronic signal rapidly steers the beam left, right, up, and down, the light acts as a very fast pen, drawing an image made of light on the projection surface.

Hajimiri and his colleagues have used the silicon chip to project images in infrared light, but additional work with different types of semiconductors will also allow the researchers to expand the tiny projector's capabilities into the visible spectrum. "In the future, this can be incorporated into a cell phone. Since there is no need for a lens, you can have a phone that acts as a projector all by itself," researchers said.