April 30, 2009
Researchers Unveil World’s Fastest Camera
Reporting their discovery in the science journal Nature, a team of researchers say they have devised the fastest imaging system the world has ever seen.
Their camera is able to capture more than six million images a second, each with a length of less than half a billionth of a second.
The device works using a pulsating laser that is dispersed in space and then stretched in time and then recaptured electronically. The camera also utilizes just one detector, rather than millions as is typical of most modern digital cameras.
According to the researchers, the new technology will be critical in analyzing a number biological phenomenon like diseased cells in flowing samples of blood.
The high-tech new gadget has been christened the Serial Time-Encoded Amplified imaging, or Steam.
The new imaging technique works by manipulating so-called "supercontinuum" laser pulses "“ tiny laser pulses that last less than a millionth of a millionth of a second and contain an incredibly broad spectrum of colors.
The device uses two optical elements to spread the tiny beam of light into an ordered, two-dimensional stream of colors, which is then used to illuminate the sample being observed. Most of the light from this "2-D rainbow" is the absorbed by the sample, but a portion of it is reflected back along its original path.
Because the spreading of the beam is extremely ordered and regular, the reflected colors carry back detailed spatial information about the sample.
"Bright spots reflect their assigned wavelength, but dark ones don't," explained UCLA professor Bahram Jalali, who led the project. "When the 2-D rainbow reflects from the object, the image is copied onto the color spectrum of the pulse."
When the returning pulse of light travels back through the dispersive optical elements, it becomes a tiny compact image of the object in the form a series of distributed colors.
As the color spectrum of the miniscule image would be impossible for traditional electronics to untangle, the researchers then route the tiny pulse into a so-called dispersive fiber "“ a fiber-optic cable able to assign different speed limits for the different colors of light. Thus, the red part of the spectrum travels through the cable ahead of the blue part and consequently reaches the end of the cable separate from the blue part.
The light is then captured with a standard photodiode as it emerges from the fiber-optic cable and is converted into a two-dimensional image that represents a 440 trillionth of a second long picture of the object.
Researchers used a laser that fired some six million pulses a second, though they say that with some additional research, they can take that number to ten million a second "“ more the 200,000 times faster than modern video cameras.
Unlike most other cameras used in scientific research, the Steam camera is able to capture a continuous feed of images and does not need to be triggered by the operator to take a picture of a specific event. Researchers say this makes it ideal for capturing random events that occur spontaneously and thus cannot be triggered.
The team says that analyzing flowing blood samples offers the perfect application for the Steam's capabilities.
Because cameras are unable to make images of individual cells in a given volume blood, standard practice has had to make do with manually imaging a few cells from random samples.
"But what if you needed to detect the presence of very rare cells that, although few in number, signify the early stages of a disease?" asks the lead author of the study, Keisuke Gode.
Tumor cells circulating in the blood may be a perfect example, added Dr. Gode. Though these important cells can be precursors to metastasis, because they may only constitute a minuscule fraction of the total cells in the blood, they are nearly impossible to detect using current imaging techniques.
"The chance that one of these cells will happen to be on the small sample of blood viewed under a microscope is virtually negligible," he added.
With the Steam camera, however, millions of quickly moving cells can be individually imaged.
The next step for the team is to develop a technique to allow 3-D imaging capable of the same time resolution, and to increase the number of pixels in each image to at least 100,000.
"Our next step is to improve the spatial resolution so we can take crystal clear pictures of the inner structures of cells," said Professor Jalali.
"We are not there yet, but if we are able to accomplish this, then there is no shortage of applications in biology."
Image Caption: The new camera can take snaps every 163 nanoseconds. Credit: NAture/T.Sato
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