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Faster than a speeding bullet: ultra high-speed cameras show the eyes what they've been missing.

As early as the fourth century B.C., man has tried to capture images of that which he could not see with is own eyes. However, not until centuries later is it possible to capture micro-scale blast wave phenomena, particle imaging velocimetry, and ignition and combustion at speeds of millions of pictures per second. Shimadzu, Columbia Md.; DRS Data & Imaging Systems; Inc., Oakland, N.J.; and Cordin Co., Salt Lake City, Utah, among others, have manufactured ultra high-speed cameras that can clearly capture such phenomena.

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Some versions of these cameras use film; however, most of the newer models use a videotape recorder and solid-state imaging. For high-speed imaging to be useful, it must be fast, achieve low noise, and be operable under low light conditions. Advances in computers and peripheral digital technologies are allowing mainstream high-speed video cameras to contain solid-state imaging technology that handles images as digital signals, with image resolutions as high as 1,280 x 1,024.

Researchers use images of shock waves after an explosion to determine the causes of destructive phenomena and try to uncover countermeasures. For instance, explosive volcanic eruptions, thunder, and supernovae all generate shockwaves.

Shocking studies

Studying shockwage phenomena isn't always "about explosions, though. For example, in the medical field, extracorporeal shockwaves are used in water to pulverize and eliminate kidney stones in a patient's body.

Such extracorporeal shockwave treatment is also used for pain treatment and is currently being tested as a cancer therapy. In addition, methods are being developed to push water jets into blood vessels to rapidly re-establish blood flow.

Kazuyoshi Takayama, a leader in shockwave phenomena at Tohoku Univ., Japan, has been waiting for a revolutionary new high-speed camera to come along. His choice in ultra high-speed cameras is Shimadzu's HyperVision HPV-1, which was a 2006 R&D 100 award winner.

Takayama says that he previously used instantaneous light sources to record shockwave phenomena, as well as supercomputer simulations to determine the shockwave dynamics. His team also developed double-exposure holographic interferometry to accurately measure high-speed phenomena resulting from shockwaves at high resolutions. However, these methods were unable to take dynamic images at a high temporal resolution below one-millionth of a second.

According to Takayama, the HPV-1 allows researchers to "clarify unknown phenomena that previously lay in the realm of the imagination." He believes this technology will result in dramatic developments in dynamics research, such as fluid mechanics or material mechanics.

The HPV-1 uses an in situ image storage system charge-coupled device (CCD) image sensor. The HPV-1's sensor (SI-CCD) was jointly developed with Takeharu Etoh, professor at Kinki Univ., Mie, lapan. The SI-CCD incorporates a high-sensitivity design that expands the light sensitive area per pixel to handle recording high-speed phenomena.

With a conventional high-speed video camera, the faster the speed, the greater the decrease in spatial resolution. However, the spatial resolution of the HPV-1 does not deteriorate even at high frame rates. The camera maintains a 312 x 260-pixel resolution at all recording speeds which allows researchers a more detailed examination of high-speed phenomena. The HPV-i has the ability to record such phenomena as shock waves, ballistics, materials failure, ignition and combustion, biomedical imaging research, neuroscience, biomechanics, and sports science.

Shedding light on the subject

On the other hand, Cordin's Rotating Mirror CCD cameras (including model numbers 530, 535, and 550) use a mirror which spins at very high speeds and is driven by a gas turbine. Mirrors rotate at up to 1.2 million rpm. The mirror is usually made from a beryllium substratum with an aluminum overcoat. Beryllium is used because of its strength-to-weight characteristics that are high enough to withstand the centrifugal forces generated at these speeds. The thin, highly polished aluminum overcoat is protected by a vapor deposit quartz coating that creates a durable reflective surface.

Light enters the camera through lenses and is reflected by the spinning mirror. These cameras produce streak images by reflecting the thin line of light from the slit directly to the film track. Frame records are produced by a method described as the Miller principle for shuttering and image transmission. A bank of relay lenses and shuttering stops arranged in an arc coaxial with the film track receives light swept by the rotating mirror. As the light enters successive shuttering stops and associated lenses, an image is relayed to the film.

Rotating mirror cameras produce frame records up to 25 million frames/sec, and streak records up to 30 mm/[micro]s with a resolution that often exceeds the limits of the film.

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Cordin's model 550 camera is available with either electric drive or gas turbine drive. Although the electric drive is simpler and less costly to operate, the gas turbine drive allows for faster flaming rates. The fastest flaming rates with the gas turbine drive require helium fill for the camera and helium drive.

Cordin's model 510 camera is equivalent to the Brandaris 128, which Cordin developed in partnership with Erasmus Univ. Rotterdam, the Netherlands, in 2003. It is a lower resolution camera made for the fastest speeds--capable of 25 million frames/sec. The model 510 allows scientists to view ultrafast phenomena, such as ultrasound contrast agent bubbles that oscillate at a frequency of 1 MHz or more.

The 510 is able to accomplish this by replacing the negative film track of the rotating mirror camera with a highly sensitive ultra high-speed camera that records 128 digital frames at a speed of up to 25 million frames/sec (equivalent to 40 ns interframe time). The sweeping light a rotating mirror camera resembles that of the optical principle of a lighthouse--thus the reason for naming it Brandaris, after the Netherlands' most recognized lighthouse.

Programmable exposure

DRS Technologies' cameras use lenses from Nikon, Tokyo, Japan, and have a high-speed imaging system based on a new approach to intensified CCD technology that allows the user to capture images at flame rates of up to 100 million frames/sec. The user simply programs the exposure and interframe times to capture settings that will record minute details for laboratory and product testing environments, as well manufacturing environments requiring the ability to diagnose and solve production line problems.

Sold in two versions, the Ultra 4 and the Ultra 8, the cameras each weigh 12.7 kg and accept Nikon optics of 50 to 600 mm lengths. A periscope lens permits through-lens focusing. The Ultra 4 delivers four images at 960 x 960 pixel resolution and the Ultra 8 produces eight frames at a resolution of 580 x 580.

In addition to extremely high flame capture rates, the Ultras also feature an exposure rate of 1 ms to as low as 10 ns a rate that helps eliminate motion blur on extremely fast events. DRS achieves this performance with a 25 or 40 mm image intensifier mated to a microchannel plate. The key, says Todd Rumbaugh, DRS' U.S. manager of ultra high-speed cameras, is a gated intensifier working in tandem with a segmented beamsplitter.

"As photons and electrons are bouncing back and forth in the intensifier, you apply more voltage to gate it down 10 ns," says Rumbaugh. The signal is passed through the splitter, which acts as a kaleidoscope, directing light into quadrants onto the 2,048 x 2,048 CCD where they form the images. The difference between the Ultra 4 and Ultra 8 are the number of quadrants on the CCD. The center quadrant on the Ultra 8 is unused, and each camera pulls in extra data from the edges of the CCD.

Many of DRS Technologies' products are used for military defense purposes such as weapons separation testing and ammunitions trajectory tracking. However, according to Sean Pender, director of business development at DRS, the Ultra 4 and Ultra 8 will likely be used at universities with engineering departments, companies that need to study crack propagation, stress factors, and in the biomedical field.

"There is a big interest in the biomedical industry with using camera systems with electron microscopes," says Pender.

A clearer and closer view into the future

All in all, since the need for ultra high-speed imaging is growing, similar products will work their way onto the market, which will result in a strong competition in equipment performance. Hopefully this will help mankind get a clearer and closer view at the phenomena speeding around them.

RESOURCES

* Cordis, www.cordis.com

* DRS Technologies, www.drs.com

* Shimadzu, www.shimadzu.com
                                                           Frames
Company    Model   Description                            Resolution

Cordin

           530     Rotating Mirror CCU                   1,000 x 1,000
           535     Rotating Mirror CCU                   1,000 x 1,000
           510     Ultra high speed rotating minor CCU     640 x 480

Shimadzu

           HPV-1    Is-CCU                                 312 x 260

DRS Technologies

           Ultra 4  CCU                                   860 x 860
           Ultra 8  CCU                                   580 x 580

           Frame
 Model    Storage   Frames Per Second

 530         16     200,000 (electric drive)
 535         16     1 million (pas turbine drive)
 510        128     25 million

 HPV-1      100     20 to 1,000,000

 Ultra 4      4     500101 million
 Ultra 8      8     500 to 1 million
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Title Annotation:PHOTONICS
Author:Nieswand, Adria; Livingstone, Paul
Publication:R & D
Date:Jun 1, 2007
Words:1500
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