Low cost 3d camera operates ‘at the speed of light’

The so-called nano-camera is expected to find use in medical imaging, collision avoidance devices and gesture recognition technology. The device relies on Time of Flight technology like that used in Microsoft's second generation Kinect device, in which the location of objects is calculated by how long it takes a light signal to reflect off a surface and return to the sensor. However, unlike the new Kinect and other similar systems, the MIT camera is able to capture translucent and semi-transparent objects in 3d. What's more, the device is expected to cost just $500 (approx. £309), considerably less than other solutions on the market which come with a hefty $500,000 price tag. In a conventional Time of Flight camera, a light signal is fired at a scene, where it bounces off an object and returns to strike the pixel. Since the speed of light is known, it is then simple for the camera to calculate the distance the signal has travelled and therefore the depth of the object it has been reflected from. Unfortunately though, changing environmental conditions, semitransparent surfaces, edges, or motion all create multiple reflections that mix with the original signal and return to the camera, making it difficult to determine which is the correct measurement. Instead, the new device uses an encoding technique commonly used in the telecommunications industry to calculate the distance a signal has travelled. "We use a new method that allows us to encode information in time," said researcher Ramesh Raskar. "So when the data comes back, we can do calculations that are very common in the telecommunications world, to estimate different distances from the single signal." The idea is said to be similar to existing techniques that clear blurring in photographs. The nano-camera probes the scene with a continuous-wave signal that oscillates at nanosecond periods. This allows the team to use inexpensive hardware – off the shelf leds can strobe at nanosecond periods, for example - meaning the camera can reach a time resolution within one order of magnitude of femtophotography at a very low cost. "By solving the multipath problem, essentially just by changing the code, we are able to unmix the light paths and therefore visualise light moving across the scene," noted Raskar. "So we are able to get similar results to the $500,000 camera, albeit of slightly lower quality, for just $500."