A new chip for 3D imaging

A 3D image produced by the new NCI chip. The image, taken from roughly half a meter (1.5 feet) away, shows the height of a US penny at various points. Credit: Ali Hajimiri/Caltech

A usual digital camera sensor picks up the direction of light and creates a specular digital image. It cannot measure the distance of the objects being photographed, so it is not good to create a 3 D image. 

Suppose you want to provide instruction to a 3D printer to replicate an object. The image captured by your digital camera would not do since it does not contain the information about the depth. 

There are accurate ways to capture an object in 3D but they are cumbersome and expensive (based on multiple laser beams). They are based on LIDAR, Laser Imaging Detection and Ranging, where the coherent light of Lasers is used as a reference to compare the reflected light from an object. The differences in phase (these are due to the distance of the detector from the object) is the information needed to calculate the depth.

Now a team of researchers at Caltech have invented a chip that uses nanophotonic coherent imaging technology. With it each pixel in the sensor acts like a LIDAR to detect both the luminosity and the distance of the light reflecting object with extreme accuracy (see photo). Each pixel is basically an interferometer that can compare the laser light illuminating the object with the one reflected by the object.

The sensor can be very small and correspondingly cheap to manufacture. It could be embedded in a cell phone, along with the laser. and you could take a few picture of an object to have a specific software working out the instruction to a 3D printer to print an exact replica. 
So far the team has been able to create a chip with just 16 pixels in a four by four matrix. This matrix is 300µm per 300µm. A sensor the size of the one used by an iPhone 5 would contain over 3000 pixels sufficient to provide the resolution needed to print an object a few inches in size.

By placing more of these matrixes side by side they expect to be able to produce a chip with the required resolution (one matching the 3D printer resolution, no need to reach a photographic resolution here).

Interesting opportunities opening up for do-it-yourself at home. A tap is leaking in your bath because the washer is wasting out?  Take a photo of the washer and print a new one with your 3D printer and replace it. Voilà! Fix done.

Author - Roberto Saracco

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