Low-cost 3D-imaging chip to be incorporated into smartphones

AUTHOR: Inavate

A new, tiny, high-resolution 3-D imager being developed at Caltech (California Institute of Technology) could give users an almost exact copy of an object within minutes.  The chip, once integrated in to a smartphone, would enable users to take a picture, send it to a 3D printer, which would then produce an accurate replica of the original object within minutes.

To make an exact copy of an object with a 3D printer, the first step is to produce a high-resolution scan of the object with a 3D camera that measures its height, width, and depth. Such 3D imaging has been around for decades, but the most sensitive systems generally are too large and expensive to be used in consumer applications.

A cheap, compact yet highly accurate new device known as a nanophotonic coherent imager (NCI) promises to change that. Using an inexpensive silicon chip less than a millimeter square in size, the NCI provides the highest depth-measurement accuracy of any such nanophotonic 3D imaging device.

The work, done in the laboratory of Ali Hajimiri, the Thomas G. Myers Professor of Electrical Engineering in the Division of Engineering and Applied Science, is described in the February 2015 issue of Optics Express.

In a regular camera, each pixel represents the intensity of the light received from a specific point in the image, which could be near or far from the camera—meaning that the pixels provide no information about the relative distance of the object from the camera. In contrast, each pixel in an image created by the Caltech team's NCI provides both the distance and intensity information. "Each pixel on the chip is an independent interferometer—an instrument that uses the interference of light waves to make precise measurements—which detects the phase and frequency of the signal in addition to the intensity," says Hajimiri.

The new chip uses an established detection and ranging technology called LIDAR, in which a target object is illuminated with scanning laser beams. The light that reflects off of the object is then analysed based on the wavelength of the laser light used, and the LIDAR can gather information about the object's size and its distance from the laser to create an image of its surroundings.

The first proof of concept of the NCI has only 16 coherent pixels, meaning that the 3D images it produces can only be 16 pixels at any given instance. However, the researchers also developed a method for imaging larger objects by first imaging a four-pixel-by-four-pixel section, then moving the object in four-pixel increments to image the next section.

In the future, Hajimiri says, the current array of 16 pixels could also be easily scaled up to hundreds of thousands. One day, by creating such vast arrays of these tiny LIDARs, the imager could be applied to a broad range of applications from very precise 3D scanning and printing to helping driverless cars avoid collisions to improving motion sensitivity in superfine human machine interfaces, where the slightest movements of a patient's eyes and the most minute changes in a patient's heartbeat can be detected on the fly.

The study was published in a paper titled, "Nanophotonic coherent imager." In addition to Hajimiri, other Caltech coauthors include former postdoctoral scholar and current assistant professor at the University of Pennsylvania, Firooz Aflatouni, graduate student Behrooz Abiri, and Angad Rekhi (BS '14). This work was partially funded by Caltech Innovation Initiative.

read the full paper here.