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  • T-rays Advance 1-pixel Camera
Oct 2008
HOUSTON, Oct. 15, 2008 -- A terahertz version of the single-pixel camera developed by Rice University researchers could lead to breakthrough technologies in security, telecom, signal processing and medicine.

The research describes a way to replace the expensive, multipixel sensor arrays used in current terahertz imaging (T-rays) systems with a single sensor.

Two keys to the system are the ongoing development of a modulator that would feed a rapid-fire series of randomized images to the sensor, and the compressed sensing algorithm that turns the raw data into an image.

The advances "could make for very inexpensive security and scientific cameras in the near future," said Richard Baraniuk, Rice's Cameron Professor in Electrical and Computer Engineering, who helped make a proof-of-concept prototype that used 600 sheets of copper (which blocks terahertz radiation) through which random holes had been punched as the modulator.

An illustration of the components of the experimental Terahertz camera, based on the single-pixel camera developed by a team of Rice researchers. (Image: Rice University)

"There's very good reason to believe you could build a terahertz modulator that could do that same task electrically, and very fast," said Daniel Mittleman, a Rice professor in electrical and computer engineering, who is testing a 4-by-4 array of metamaterials supplied by Los Alamos National Laboratory that become opaque to terahertz radiation when a voltage is applied.

"There are lots of applications for terahertz imaging, if you could make a real-time imager that's sensitive enough. Some of them are pretty science-fictiony, but some are pretty realistic," Mittleman said. "I think this is really promising."

Terahertz radiation, which occupies space in the electromagnetic spectrum between infrared and microwave, penetrates fabric, wood, plastic and even clouds, but not metal or water. Unlike x-rays, T-rays are not harmful, and cheap T-ray cameras may someday be used for security screening in airports, supplementing traditional x-ray scanners and walk-through portals.

In addition, hyperspectral capabilities inherent in even basic single-pixel cameras make them useful for all kinds of things, said Kevin Kelly, associate professor in electrical and computer engineering. "Current cameras break an image down into red, green and blue. But this system breaks down every pixel into all the individual wavelengths that make up a color.

"If you want to know whether that green object over there is a bunch of trees or a tank painted green, this system will tell you," he said.

Rice introduced its research into the single-pixel camera two years ago. The technology made waves when it was introduced, and advances have come quickly, particularly in the compressive sensing algorithms that make it possible to do with one pixel what takes commercial digital cameras millions.

In addition to Baraniuk, Mittleman and Kelly, coauthors of a paper on the work recently published online in Applied Physics Letters were Rice graduate students Wai Lam Chan and Dharmpal Takhar and undergraduate student Kriti Charan.

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A light-tight box that receives light from an object or scene and focuses it to form an image on a light-sensitive material or a detector. The camera generally contains a lens of variable aperture and a shutter of variable speed to precisely control the exposure. In an electronic imaging system, the camera does not use chemical means to store the image, but takes advantage of the sensitivity of various detectors to different bands of the electromagnetic spectrum. These sensors are transducers...
Denoting the use of binary notation; i.e., the representation of data by bits (1 or 0).
The technology of generating and harnessing light and other forms of radiant energy whose quantum unit is the photon. The science includes light emission, transmission, deflection, amplification and detection by optical components and instruments, lasers and other light sources, fiber optics, electro-optical instrumentation, related hardware and electronics, and sophisticated systems. The range of applications of photonics extends from energy generation to detection to communications and...
Contraction of "picture element." A small element of a scene, often the smallest resolvable area, in which an average brightness value is determined and used to represent that portion of the scene. Pixels are arranged in a rectangular array to form a complete image.
1. A generic term for detector. 2. A complete optical/mechanical/electronic system that contains some form of radiation detector.
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