Single-pixel detectors used to make 3D images without a camera
Researchers at the University of Glasgow’s School of Physics and Astronomy have found a way to make sophisticated 3D images without using conventional digital cameras. Their system uses simple, cheap detectors which have just a single pixel to sense light instead of the millions of pixels used in the imaging sensors of digital cameras. The technology could be used to create much more affordable forms of 3D imaging.
“Single-pixel detectors in four different locations are used to detect light from a data projector, which illuminates objects with a rapidly-shifting sequence of black-and-white patterns similar to crossword puzzles”, said Miles Padgett, Kelvin Chair of Natural Philosophy at the University, who led the team of researchers which developed the technique. “When more of the white squares of these patterns overlap with the object the intensity of the light reflected back to the detectors is higher. A series of projected patterns and the reflected intensities are used in a computer algorithm to produce a 2D image.”
The technique the team use is called 3D computational imaging, or ‘ghost‘ imaging, and the system they have created can produce detailed images of objects in just a few seconds. Four detectors give images, each of which contain shadows which provide clues about the 3D shape of the object. Combining the four images using a well-known ‘shape from shade’ technique allows the creation a full 3D image of the object.
Conventional 3D imaging systems which use multiple digital camera sensors to produce a 3D image from 2D information need to be carefully calibrated to ensure the multi-megapixel images align correctly. Our single-pixel system creates images with a similar degree of accuracy without the need for such detailed calibration.
“It might seem a bit counter-intuitive to think that more information can be captured from a detector which uses just a single pixel rather than the multi-megapixel detectors found in conventional digital cameras”, said Baoqing Sun, who is the lead author on the paper. “However, digital camera sensors have a very limited sensitivity beyond the spectrum of visible light, whereas a single-pixel detector can easily be made to capture information far beyond the visible, reaching wavelengths from X-ray to TeraHertz.”
In other words, single-pixel detectors can detect wavelengths far beyond those digital cameras are currently capable of. This means that single-pixel detectors which cost just a few pounds each are now capable of producing images across a far wider spectrum than 3D imaging systems currently on the market which cost tens of thousands of pounds.
The system’s unique capabilities and low cost could make it a valuable tool for a wide range of industries. When created, a more portable version of the system could be used to look for the telltale gases which leak from the ground where oil can be found, or it could be tuned into the terahertz range to probe just below the skin to search for tumors or other medical conditions. University of Glasgow researchers plan to continue working on the system and seek for commercial partners to commercialize their technology.
For more information, read the paper published in the journal Science: “3D Computational Imaging with Single-Pixel Detectors”.
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