Swimming Pool Game 'Marco Polo' Used To Develop Robot Control

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ScienceDaily (Mar. 25, 2009) — Scientists have used a popular kids swimming pool game to guide their development of a system for controlling moving robots that can autonomously detect and capture other moving targets.

Engineers from Duke University and the University of New Mexico have used the simple pursuit-evasion game "Marco Polo" to solve a complex problem -- namely, how to create a system that allows robots to not only "sense" a moving target, but intercept it.
Such systems have broad applications, ranging from security systems to track unwanted intruders like enemy ships or burglars, to systems that create radiation or environmental hazard maps, or even track endangered species.
The main challenge facing researchers is developing the artificial intelligence to control the robots and their sensors without direct human guidance.
The goal of the game "Marco Polo" is for the person who is "it" to tag another person, who then becomes the new pursuer. However, pursuers must keep their eyes closed. At any time, the pursuer can call out "Marco," and everyone else must respond by saying "Polo." In this way, the pursuer can gradually estimate where the targets are in the pool and where they might go.
"Games give us a good way of making these highly complex problems easier to visualize," said Silvia Ferrari, assistant professor of mechanical engineering and materials science at Duke's Pratt School of Engineering. Ferrari and colleague Rafael Fierro, associate professor of electrical engineering at the University of New Mexico, published the results from their latest experiments online in the Journal on Control and Optimization, a publication of the Society for Industrial and Applied Mathematics.
"Just as in 'Marco Polo,' we needed to create a way that permits mobile robots to detect other moving objects and make predictions about where the targets might go," Ferrari said. "When done efficiently, the mobile sensor switches from pursuit mode to capture mode in the shortest amount of time."
Ferrari's laboratory had already developed a similar type of algorithm, known as cell decomposition, in which space is broken down into a series of distinct cells. Past experiments allowed a robot to move through space without colliding with stationary obstacles.
The latest experiments included not only robots equipped with camera sensors, but also stationary camera sensors, which allowed for "coverage" of all the cells within the space.
"The idea is that multiple sensors are deployed in the space to cooperatively detect moving targets within that space," Fierro said. "As the sensor makes more detections, it is better able to predict the likely path of the intruder. The ultimate path taken by the robot sensor is one that maximizes the probability of detection and minimizes the distance needed to capture the target."
While the security and military applications of this type of detection system are obvious, Fierro also points out that the new algorithms can be used in other ways to detect targets that aren't necessarily intruders.
"Targets could be completely different things, like mines or explosives, or chemical or radiation leaks," Fierro said. "The robots can use their sensors to keep track of the detected locations and build a 'map' to let people know where to go or not to go."
The algorithms could also be used to help explain natural phenomena, such as the behaviors of members of a wolf pack as they chase and capture their prey.
The latest experiments were conducted at the University of New Mexico and involved intruders moving in straight lines at a constant speed.
"We are now developing algorithms that will more closely mimic the real world by giving intruders the ability to take evasive actions," Ferrari said. "The other main issue is to ensure that all the different mobile sensors can communicate with each other at all times and coordinate their activities based on that communication."
The research was supported by the National Science Foundation, Office of Naval Research and U.S. Army Research Office.
Other members of the research team were Duke's Chenghui Cai and Kelli Baumgartner, and Oklahoma State University's James McClintock and Brent Perteet.
Adapted from materials provided by Duke University, Pratt School of Engineering.

New Way To Produce Electronic Components Can Lead To Cheap And Flexible Electronics

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ScienceDaily (Mar. 25, 2009) — Flexible display screens and cheap solar cells can become a reality through research and development in organic electronics. Physicists at Umeå University in Sweden have now developed a new and simple method for producing cheap electronic components.

“The method is simple and can therefore be of interest for future mass production of cheap electronics,” says physicist Ludvig Edman.
Organic chemistry is a rapidly expanding research field that promises exciting and important applications such as flexible display screens and cheap solar cells. One attractive feature is that organic electronic materials can be processed from a solution.
“This makes it possible to paint thin films of electronic materials on flexible surfaces like paper or plastic,” explains Ludvig Edman.
Electronic components with various functions can then be created by patterning the film with a specific structure. Until now it has proven to be problematic to carry out this patterning in a simple way without destroying the electronic properties of the organic material.
“We have now developed a method that enables us to create patterns in an efficient and gentle way. With the patterned organic material as a base, we have managed to produce well-functioning transistors,” says Ludvig Edman.
A thin film of an organic electronic material, a so-called fullerene, is first painted on a selected surface. The parts of the film that are to remain in place are directly exposed to laser light. Then the whole film can be developed by rinsing it with a solution. A well-defined pattern then emerges where the laser light hit the surface.
A key advantage with this method of patterning is that it is both simple and scalable, which means that it can be useful in future production of cheap and flexible electronics in an assembly line process.
Other researchers involved in developing the method are Andrzej Dzwilewski and Thomas Wågberg.
The findings are presented in the publication Journal of the American Chemical Society.
Journal reference:
Andrzej Dzwilewski, Thomas Wågberg and Ludvig Edman. Photo-Induced and Resist-Free Imprint Patterning of Fullerene Materials for Use in Functional Electronics. Journal of the American Chemical Society, 2009; 131 (11): 4006 DOI: 10.1021/ja807964x
Adapted from materials provided by Vetenskapsrådet (The Swedish Research Council), via AlphaGalileo.

Nanotech Batteries For A New Energy Future

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ScienceDaily (Mar. 20, 2009) — Researchers at the Maryland NanoCenter at the University of Maryland have developed new systems for storing electrical energy derived from alternative sources that are, in some cases, 10 times more efficient than what is commercially available.

In order to save money and energy, many people are purchasing hybrid electric cars or installing solar panels on the roofs of their homes. But both have a problem -- the technology to store the electrical power and energy is inadequate.
Battery systems that fit in cars don't hold enough energy for driving distances, yet take hours to recharge and don't give much power for acceleration. Renewable sources like solar and wind deliver significant power only part time, but devices to store their energy are expensive and too inefficient to deliver enough power for surge demand.
Researchers at the Maryland NanoCenter at the University of Maryland have developed new systems for storing electrical energy derived from alternative sources that are, in some cases, 10 times more efficient than what is commercially available. The results of their research are available in a recent issue of Nature Nanotechnology.
"Renewable energy sources like solar and wind provide time-varying, somewhat unpredictable energy supply, which must be captured and stored as electrical energy until demanded," said Gary Rubloff, director of the University of Maryland's NanoCenter. "Conventional devices to store and deliver electrical energy -- batteries and capacitors -- cannot achieve the needed combination of high energy density, high power, and fast recharge that are essential for our energy future."
Researchers working with Professor Rubloff and his collaborator, Professor Sang Bok Lee, have developed a method to significantly enhance the performance of electrical energy storage devices.
Using new processes central to nanotechnology, they create millions of identical nanostructures with shapes tailored to transport energy as electrons rapidly to and from very large surface areas where they are stored. Materials behave according to physical laws of nature. The Maryland researchers exploit unusual combinations of these behaviors (called self-assembly, self-limiting reaction, and self-alignment) to construct millions -- and ultimately billions -- of tiny, virtually identical nanostructures to receive, store, and deliver electrical energy.
"These devices exploit unique combinations of materials, processes, and structures to optimize both energy and power density -- combinations that, taken together, have real promise for building a viable next-generation technology, and around it, a vital new sector of the tech economy," Rubloff said.
"The goal for electrical energy storage systems is to simultaneously achieve high power and high energy density to enable the devices to hold large amounts of energy, to deliver that energy at high power, and to recharge rapidly (the complement to high power)," he continued.
Electrical energy storage devices fall into three categories. Batteries, particularly lithium ion, store large amounts of energy but cannot provide high power or fast recharge. Electrochemical capacitors (ECCs), also relying on electrochemical phenomena, offer higher power at the price of relatively lower energy density. In contrast, electrostatic capacitors (ESCs) operate by purely physical means, storing charge on the surfaces of two conductors. This makes them capable of high power and fast recharge, but at the price of lower energy density.
The Maryland research team's new devices are electrostatic nanocapacitors which dramatically increase energy storage density of such devices - by a factor of 10 over that of commercially available devices - without sacrificing the high power they traditionally characteristically offer. This advance brings electrostatic devices to a performance level competitive with electrochemical capacitors and introduces a new player into the field of candidates for next-generation electrical energy storage.
Where will these new nanodevices appear? Lee and Rubloff emphasize that they are developing the technology for mass production as layers of devices that could look like thin panels, similar to solar panels or the flat panel displays we see everywhere, manufactured at low cost. Multiple energy storage panels would be stacked together inside a car battery system or solar panel. In the longer run, they foresee the same nanotechnologies providing new energy capture technology (solar, thermoelectric) that could be fully integrated with storage devices in manufacturing.
This advance follows soon after another accomplishment, the dramatic improvement in performance (energy and power) of electrochemical capacitors (ECC's), thus 'supercapacitors,' by Lee's research group, published recently in the Journal of the American Chemical Society. Efforts are under way to achieve comparable advances in energy density of lithium (Li) ion batteries but with much higher power density.
"The University of Maryland's successes are built upon the convergence and collaboration of experts from a wide range of nanoscale science and technology areas with researchers already in the center of energy research," Rubloff said.
The Research Team
Gary Rubloff is Minta Martin Professor of Engineering in the materials science and engineering department and the Institute for Systems Research at the University of Maryland's A. James Clark School of Engineering. Sang Bok Lee is associate professor in the Department of Chemistry and Biochemistry at the College of Chemical and Life Sciences and WCU (World Class University Program) professor at KAIST (Korea Advanced Institute of Science and Technology) in Korea. Lee and Rubloff are part of a larger team developing nanotechnology solutions for energy capture, generation, and storage at Maryland. Their collaborators on electrical energy storage include Maryland professors Michael Fuhrer (physics), associate director of the Maryland Nanocenter Reza Ghodssi (electrical and computer engineering), John Cumings (materials science engineering), Ray Adomaitis (chemical and biomolecular engineering), Oded Rabin (materials science and engineering), Janice Reutt-Robey (chemistry), Robert Walker (chemistry), Chunsheng Wang (chemical and biomolecular engineering), Yu-Huang Wang (chemistry) and Ellen Williams (physics), director of the Materials Research Science and Engineering Center at the University of Maryland.
This work was partially supported by the Laboratory for Physical Sciences and by the university's Materials Research Science and Engineering Center under a grant from the National Science Foundation
Adapted from materials provided by University of Maryland, College Park.

New Organic Material May Speed Internet Access; Telecom Breakthrough Mimics The Settling Snow

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ScienceDaily (Mar. 21, 2009) — The next time an overnight snow begins to fall, take two bricks and place them side by side a few inches apart in your yard.

In the morning, the bricks will be covered with snow and barely discernible. The snowflakes will have filled every vacant space between and around the bricks.
What you will see, says Ivan Biaggio, resembles a phenomenon that, when it occurs at the smallest of scales on an integrated optical circuit, could hasten the day when the Internet works at superfast speeds.
Biaggio, an associate professor of physics at Lehigh University, is part of an international team of researchers that has developed an organic material with an unprecedented combination of high optical quality and strong ability to mediate light-light interaction and has engineered the integration of this material with silicon technology so it can be used in optical telecommunication devices.
A description of this material was published on online in the journal Nature Photonics on March 15.
The material, which is composed of small organic molecules with high nonlinear optical susceptibilities, mimics the behavior of the snowflakes covering the bricks when it is deposited into the slot, or gap, that separate silicon waveguides that control the propagation of light beams on an integrated optical circuit.
Just as the snowflakes, being tiny and mobile, fill every empty space between the two bricks, Biaggio says, the molecules completely and homogeneously fill the slot between the waveguides. The slots measure only tens of nanometers wide; 1 nm is one one-billionth of a meter, or about the width of a dozen carbon atoms.
"We have been able to make thin films by combining the molecules into a material that is perfectly transparent, flat, and free of any irregularities that would affect optical properties," says Biaggio.
The slot between the waveguides is the region where most of the light guided by the silicon propagates. By filling the slot, say Biaggio and his collaborators, the molecules add an ultra-fast all-optical switching capability to silicon circuitry, creating a new ability to perform the light-to-light interactions necessary for data processing in all-optical networks.
The nanophotonic device obtained in this way, says the group, has demonstrated the best all-optical demultiplexing rate yet recorded for a silicon-organic-hybrid device.
Multiplexing is the process by which multiple signals or data streams are combined and transmitted on a single channel, thus saving expensive bandwidth. Demultiplexing is the reverse process.
In tests, the novel hybrid device was able to extract every fourth bit of a 170-gigabit-per-second telecommunications data stream and to demultiplex the stream to 42.7 gigabits per second.
Biaggio's group is part of an international collaboration that includes scientists from the Institute of Photonics and Quantum Electronics at the University of Karlsruhe in Germany, the Photonics Research Group at Ghent University in Belgium, and the Laboratory for Organic Chemistry at the Swiss Federal Institute of Technology (ETH) in Zurich. Biaggio is affiliated with Lehigh's Center for Optical Technologies (COT). Another group member, Bweh Esembeson, earned a Ph.D. in physics from Lehigh earlier this year and is now an applications engineer with Thorlabs Inc. in New Jersey.
The silicon-organic-hybrid device and its breakthrough properties were presented for the first time as a postdeadline contribution at a meeting of the optical telecom industry last spring and at several other scientific conferences, and Biaggio's group published an article titled "A High-optical Quality Supramolecular Assembly for Third-order Integrated Nonlinear Optics" in the October 2008 issue of Advanced Materials.
A nonlinear optical answer to bandwidth demand
As Internet users demand greater bandwidth for ever faster communications, scientists and engineers are working to increase the speed at which information can be transmitted and routed along a network. They are hoping to achieve a major leap in velocity by designing circuits that rely solely on light-waves process data.
At present, data must be converted back and forth from optical signals to electrical signals for managing its progress within the optical telecommunication network. This limits the flexibility and the speed of optical telecommunication. All-optical circuits, experts say, could unleash the full potential of optical telecommunication and data processing.
All-optical circuits require nonlinear optical materials with good optical quality. A nonlinear optical response occurs in a material when the intensity of light alters the properties of the material through which light is passing, affecting, in turn, the manner in which the light propagates.
Biaggio's group is working with a small organic molecule called DDMEBT that possesses one of the strongest nonlinear optical responses yet observed when compared to its relatively small size. The molecule can condense from the vapor phase into a bulk material. The high, off-resonant bulk nonlinearity and large-scale homogeneity of this material, says Esembeson, represent a unique combination not often found in an organic material.
"Between high optical nonlinearity in a molecule and ability to actually fabricate a bulk plastic with excellent optical quality, there is always a compromise," he says.
The DDMEBT bulk material possesses 1,000 times the nonlinearity of silica glass. This organic material, however, is difficult to flexibly structure into nanoscale waveguides or other optical circuitry. Silicon, on the other hand, is structurally suited to the dense integration of components on photonic circuit devices. And silicon technology is mature and precise. It enables the creation of waveguides whose nanoscale flatness facilitates the control of light propagation.
"With pure silicon," says Biaggio, "you can build waveguides that enable you to control light beam propagation, but you cannot get ultrafast light-to-light interaction. Using only silicon, people have achieved a data switching rate of only 20 to 30 gigabits per second, and this is very slow.
"We need higher-speed switching to achieve a higher bit rate. Organic materials can do this, but they are not terribly good for building waveguides that control propagation of tightly confined light beams."
To combine the strengths of the DDMEBT and the silicon, Biaggio and his collaborators have fashioned silicon-organic hybrid (SOH) waveguides where silicon waveguides are covered with DDMEBT.
"We have combined the two approaches," he says. "We start from a silicon waveguide designed to guide the light between two silicon ridges . Then we use molecular beam deposition to fill the space between the ridges with the organic material [DDMEBT], creating a dense plastic with high optical quality and high nonlinearity where the light propagates.
"We combine the best of both technologies."
One of the group's singular achievements, he says, is the filling-in process.
"The key question was whether we could put the DDMEBT between the two silicon strips. There is a lot of research in this area, but no one had been able to make an organic material completely and homogeneously cover such a silicon structure, so that it spreads out and fills all the spaces. Homogeneity is necessary to prevent light scattering and losses.
We now achieved this by using a molecular structure that decreases inter-molecular interactions and promotes the formation of a homogeneous solid state. We then heated the molecules to a vapor phase and used a molecular beam to deposit the molecules on top of the silicon structure. The molecules were able to homogeneously fill the nanometer scale slot between the silicon ridges and to cover the whole structure we needed to cover.
"Our collaborators in Karlsruhe, who have state-of-the-art equipment for characterizing optical communications systems, were able to reliably switch individual bits out of a 170 gigabits per second data stream, which is impressive, but the organic material would be able to support even faster data rates"
The researchers summed up their achievements in one of their forthcoming articles: "To the best of our knowledge, this is the first time that nonlinear SOH [silicon-organic hybrid] slot waveguides were used in high-speed optical communication systems. We believe that there is still a large potential for improving the conversion efficiency and the signal quality."
Journal reference:
C. Koos, P. Vorreau, T. Vallaitis, P. Dumon, W. Bogaerts, R. Baets, B. Esembeson, I. Biaggio, T. Michinobu, F. Diederich, W. Freude & J. Leuthold. All-optical high-speed signal processing with silicon–organic hybrid slot waveguides. Nature Photonics, 2009; DOI: 10.1038/nphoton.2009.25
Adapted from materials provided by Lehigh University.

Carbon Nanotubes Are Superior To Metals For Electronics, According to Engineers

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ScienceDaily (Mar. 20, 2009) — In the quest to pack ever-smaller electronic devices more densely with integrated circuits, nanotechnology researchers keep running up against some unpleasant truths: higher current density induces electromigration and thermomigration, phenomena that damage metal conductors and produce heat, which leads to premature failure of devices.

But University at Buffalo researchers who study electronics packaging recently made a pleasant discovery: that's not the case with Single-Walled Carbon Nanotubes (SWCNTs).
"Years ago, everyone thought that the problem of cooling for electronics could be solved," said Cemal Basaran, Ph.D., professor in the UB Department of Civil, Structural and Environmental Engineering and director of the Electronics Packaging Lab in UB's School of Engineering and Applied Sciences. "Now we know that's not true. Electronics based on metals have hit a wall. We are done with metals."
Single Walled Carbon Nanotubes are extremely thin, hollow cylinders, measuring no thicker than a single atom. Thousands of times stronger than metals, they are expected to one day replace metals in millions of electronic applications.
Basaran and his doctoral student Tarek Ragab have spent the past four years performing quantum mechanics calculations, which prove that in carbon nanotubes, higher current density does not lead to electromigration and thermomigration; it also produces just one percent of the heat produced by traditional metals, such as copper.
Basaran will present the findings in November when he delivers a keynote lecture at the American Society of Mechanical Engineers (ASME) International Mechanical Engineering Congress and Exposition in Orlando.
The findings demonstrate yet another tantalizing property of CNTs, he said.
"It has been assumed that for carbon nanotubes, the electrical heating process would be governed by Joules law, where resistance in a circuit converts electric energy into heat," said Basaran. "We are the first to show mathematically, from a quantum mechanics point of view, that carbon nanotubes do not follow Joules law."
According to Basaran, this essential difference between metals and carbon nanotubes lies in the way they conduct electricity.
"Even though carbon nanotubes are conductive, they do not have metallic bonds," he said. "As a result, they do not conduct electricity the way that traditional metals do."
In conventional metals, he explained, conduction causes a scattering of electrons within the lattice of the material so that, when electrons move during conduction, they bump into atoms. This creates friction and generates heat, the same way a household iron works.
"On the other hand, in carbon nanotubes, electric conduction happens in a very different, one-dimensional 'ballistic' way," he said. "The electrons are fired straight through the material, so that the electrons have very little interference with the atoms."
He drew an analogy, using the difference between a conventional railroad train and a magnetically levitated train.
"In the conventional train, you have friction between the wheels and the track," said Basaran. "Through the generation of heat, that friction causes a loss of energy. But with a magnetically levitated train, the wheels and track are not in direct contact. Without that friction, they can travel much faster."
The minimal amount of friction gives carbon nanotubes a tremendous advantage over conventional metals, said Basaran. The unique properties of carbon nanotubes will allow engineers to realize a host of smaller, faster and more powerful new devices that right now cannot exist because of the limitations of conventional metals.
"When an electric car finally is manufactured, its batteries probably will be based on carbon nanotubes," said Basaran. "You can't use traditional metals in the engines because they run so hot."
Much of Basaran's $1 million-plus funding at UB comes from sources like the U.S. Navy, which is interested in sophisticated electronics systems that could operate under very demanding conditions, such as the electric ship the Navy is building.
Basaran's unique perspective comes from decades of research, which has fundamentally changed what is known about the high current density performance properties of metals and their limitations.
He also sounded a cautionary note, pointing out that current research and development expenditures on carbon nanotubes in the U.S. electronics industry are very small when compared to those of our Asian competitors.
"If the industry continues this way, when carbon nanotube-based electronics become a reality, U.S. electronics manufacturers may be in a position similar to U.S. car manufacturers today, because they have failed to keep up with advances in engineering," he said.
Adapted from materials provided by University at Buffalo.

Nanoscopic Probes Can Track Down And Attack Cancer Cells

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ScienceDaily (Mar. 20, 2009) — A researcher has developed probes that can help pinpoint the location of tumors and might one day be able to directly attack cancer cells.

Joseph Irudayaraj, a Purdue University associate professor of agricultural and biological engineering, developed the nanoscale, multifunctional probes, which have antibodies on board, to search out and attach to cancer cells.
A paper detailing the technology was released last week in the online version of Angewandte Chemie, an international chemistry journal.
"If we have a tumor, these probes should have the ability to latch on to it," Irudayaraj said. "The probe could carry drugs to target, treat as well as reveal cancer cells."
Scientists have developed probes that use gold nanorods or magnetic particles, but Irudayaraj's nanoprobes use both, making them easier to track with different imaging devices as they move toward cancer cells.
The magnetic particles can be traced through the use of an MRI machine, while the gold nanorods are luminescent and can be traced through microscopy, a more sensitive and precise process. Irudayaraj said an MRI is less precise than optical luminescence in tracking the probes, but has the advantage of being able to track them deeper in tissue, expanding the probes' possible applications.
The probes, which are about 1,000 times smaller than the diameter of a human hair, contain the antibody Herceptin, used in treatment of metastatic breast cancer. The probes would be injected into the body through a saline buffering fluid, and the Herceptin would find and attach to protein markers on the surface of cancer cells.
"When the cancer cell expresses a protein marker that is complementary to Herceptin, then it binds to that marker," Irudayaraj said. "We are advancing the technology to add other drugs that can be delivered by the probes."
Irudayaraj said better tracking of the nanoprobes could allow doctors to pinpoint the location of known tumors and better treat the cancer.
The novel probes were tested in cultured cancer cells. Irudayaraj said the next step would be to run a series of tests in mice models to determine the dose and stability of the probes.
The research was funded through a National Institute of Health grant, as well as by the Purdue Research Foundation. Irudayaraj is head of a biological engineering team that includes postdoctoral researcher Chungang Wang and graduate student Jiji Chen.
Adapted from materials provided by Purdue University.

Fast Camera Shows Even Small Variations In Blood Circulation

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ScienceDaily (Mar. 20, 2009) — Burns or other disorders that disrupt the blood flow in tissues will soon be easier to assess thanks to a camera that is capable of imaging blood circulation in real time.

Compared to an earlier version, the new optical perfusion camera (TOPCam) from Twente, the Netherlands, is a significant improvement with regard to speed, so that even small variations in blood circulation are immediately visible. The camera is now ready for clinical application. Researchers of the Institute for Biomedical Technology (BMTI) of the University of Twente are publishing an article on the camera in the March number of Optics Express.
After earlier successful tests at the Martini Hospital in Groningen, the Netherlands, the researchers have made a number of significant improvements to the camera. The speed of the earlier version was commended by doctors and nurses, but real-time images of variations in the blood circulation were not yet possible. They are now, though, according to researcher Wiendelt Steenbergen: “We can now see rapid variations in blood circulation, too, for example when the circulation gets going again after occlusion of an arm or after a transplant.” The measured reaction gives an immediate impression of the condition of the vascular bed.
The researchers were able to reach these high speeds by using a broad laser beam to simultaneously illuminate the entire area of skin in question. Images are made of the tissue with a high-speed camera. Laser light that is scattered by moving red blood cells gives variation in the clarity of the pixels as a result of the Doppler Effect. Up till now it had been a problem transferring all the data to the computer quickly enough, but real time images are now enabled by making better use of the camera memory.
Now that the newest modifications have been made, the camera is ready for clinical application, Steenbergen says. The TOPCam is also suitable for other applications such as the assessment of blood circulation in diabetics. This research, which was carried out by the BMTI, was financed by the Technology Foundation (STW).
Journal reference:
Matthijs Draijer, Erwin Hondebrink, Ton van Leeuwen, and Wiendelt Steenbergen. Twente Optical Perfusion Camera: system overview and performance for video rate laser Doppler perfusion imaging. Optics Express, 2009; 17 (5): 3211-3225 DOI: 10.1364/OE.17.003211
Adapted from materials provided by University of Twente.