A tiny lidar device could turn mobile phones into powerful 3-D scanning devices. Based on a silicon chip less than a square millimeter in size, the nanophotonic coherent imager (NCI) provides the highest depth-measurement accuracy of any such nanophotonic 3-D imaging device, according to its developers at the California Institute of Technology. The device operates on a modified time-domain frequency-modulated continuous-wave (FMCW) ranging scheme that allows it to overcome the traditional resolution limits of frequency-domain detection, the researchers said. It is capable of high-resolution 3-D reflective and transmissive imaging, as well as index contrast imaging. A 3-D image with microscale resolution produced with a nanophotonic coherent imaging chip from roughly half a meter away. Courtesy of Dr. Ali Hajimiri/Caltech. “Each pixel on the chip is an independent interferometer … which detects the phase and frequency of the signal in addition to the intensity,” said professor Dr. Ali Hajimiri. “By having an array of tiny lidars on our coherent imager, we can simultaneously image different parts of an object or a scene without the need for any mechanical movements within the imager.” The first proof-of-concept NCI is a 4 × 4-pixel array on an active area of 300 μm2. Working section by section, the researchers used the device to piece together a 3-D image of the front of a U.S. penny from half a meter away, with 15-μm depth resolution and 50-μm lateral resolution. The array could be easily scaled up to hundreds of thousands of pixels, Hajimiri said. One day, he said, the concept could be applied to a broad range of applications from very precise 3-D 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 minute changes in a patient’s heartbeat can be detected on the fly. “The small size and high quality of this new chip-based imager will result in significant cost reductions, which will enable thousands of new uses for such systems by incorporating them into personal devices such as smartphones,” he said. The research was published in Optics Express (doi: 10.1364/OE.23.005117). For more information, visit www.caltech.edu.