May 14, 2009 Using a new approach based on more than 10 years of research, engineers at the UCLA Henry Samueli School of Engineering and Applied Science have demonstrated a camera that captures images at 6 million frames per second - that's a thousand times faster than any existing conventional camera. This new technique opens up new possibilities in medical research and among other things, may lead to image capture of individual cells in blood streams, opening up the possibility of detection of unhealthy or cancerous cell forms.
Researchers Keisuke Goda, Kevin Tsia and team leader Bahram Jalali developed the approach that captures each picture with an ultrashort laser, a flash of light a billionth of a second long. The technique overcomes the need for a CCD (charge-coupled device) or CMOS (complementary metal-oxide semiconductor) sensor used in modern digital cameras and unlike other high-speed imaging methods, does not require cooling of the camera or high-intensity illumination. Once captured, each pulse is converted into a serial data stream similar to the data in a fiber optic network. The laser pulses, each of which carries an entire picture, is then amplified and simultaneously slowed in time to enable capture with an electronic digitizer.
One of the problems with traditional cameras is that they become less and less sensitive at higher speeds, because less exposure means less time available to collect the photons between frames. In addition the signal at these speeds becomes weaker and more prone to noise. The new imager overcomes this problem via optical image amplification.
"Our serial time-encoded amplified microscopy (STEAM) technology enables continuous real-time imaging at a frame rate of more than 6 MHz, a shutter speed of less than 450 ps and an optical image gain of more than 300 — the world's fastest continuously running camera, useful for studying rapid phenomena in physics, chemistry and biology," said research co-author Goda, a postdoctoral researcher in the group.
The group has initially proven the camera in studies on the phenomena of laser ablation – capturing it in real time. It is anticipated that these studies will enable a better understanding and optimization of laser ablation, an important process in laser medicine. Another medical application that Jalali believes the camera is ideally suited for is the technique of flow cytometry, used in blood analysis. Traditional analyzers can count cells and determine their size but can’t take pictures of them, as traditional camera techniques are not sensitive enough. This new technique should not only overcome this problem but opens up the possibility for detection of individual cells such as diseased or cancerous forms. "The chance that one of these cells will happen to be on the small sample of blood viewed under a microscope is negligible," Jalali said. "To find these rogue cells — needles in the haystack — you need to analyze billions of cells, the entire haystack. Ultra-high-speed imaging of cells in flow is a potential solution for detection of rare abnormal cells."
The Research Paper was published in the April 30 issue of Nature.
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