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The first demonstration of cellular microsurgery in living cells, a digital camera that can make home holograms, and improvements in face recognition technology were among the technical highlights at the 2003 Frontiers in Optics conference. Co-sponsored by the Optical Society of America and the APS Division of Laser Science, the annual event provides up-to-the-minute advancements in optics and photonics research, and features a breadth of significant topics from medicine to astronomy and computing.
The meeting was held October 5-9, 2003, in Tucson, AZ, and also featured a joint plenary session with three world-renowned keynote speakers: Presidential Science Advisor John Marburger, Roger Angel (University of Arizona) on the observation of extra-solar planets, and Harvard University's Gerald Gabrielse on cold anti-hydrogen.
Entangled Photons for Long-Distance Calibration
Testing optical devices such as telescopes and spectrometers often requires a carefully calibrated source of photons, which are then sent to an optical device to see how it responds.
But when the optical device is located in hard-to-reach places such as aboard the International Space Station, it's not always easy or cost-effective to carry a calibrated source to the optical instrument. Researchers at the University of Maryland, Baltimore County, have developed a scheme to accurately test optical equipment at remote locations.
Giuliano Scarcelli and coworkers have built a prototype of a system that allows them to precisely characterize optical devices at a distance by taking advantage of the fact that entangled photons have very special relationships.
If the state of one of a pair of entangled photons is measured, the state of the other photon can be unequivocally calculated from quantum mechanical rules.
The researchers first create a pair of entangled photons. One photon is sent to a monochromator, where its characteristics are precisely recorded. The second photon is sent to the device to be tested, and the device's response to the single photon signal is recorded and sent back to the lab.
Because the researchers know the state of the second photon by looking at the first, they can determine the response of the remote optical device to a well-known signal, and can interpret the remote device's measurements.
So far, the researchers have experimentally confirmed their results on instruments located at two meters from the entangled photon source, but longer distance tests are feasible in principle.
Eric Mazur of Harvard University discussed the use of very short laser pulses to alter single biological structures. Using this technique, the researchers have demonstrated "cellular microsurgery" in living cells, by eliminating a single mitochondrion or cutting the strands of a cytoskeleton. Furthermore, the researchers have performed "nano-neurosurgery" in living nematodes, by cutting individual axons in the organism without killing the nerve cell or disrupting the surrounding tissue. Compared to traditional biochemical or mechanical methods of manipulating tissue, femtosecond micromanipulation is more selective and precise and less invasive, opening the door to many new studies, which the researchers are currently pursuing with colleagues at Harvard Medical School and its biology department. Such studies could identify new clinical uses of femtosecond lasers in surgery at the cellular level and also unlock mysteries of the brain.
Optical Telescopes Could Detect Life Beyond Solar System
Wesley Traub of the Harvard-Smithsonian Center for Astrophysics discussed telescope designs that could potentially detect signs of life on planets beyond our solar system. Examining up to 150 nearby stars, these new telescopes would obtain highly detailed images in the visible part of the light spectrum. Besides having the ability to detect new planets, such high-resolution visible images could indicate planetary oxygen, water, ozone, air, and possibly even land plants (by recording the distinctive light that would be reflected by chlorophyll). To capture these features, scientists on NASA's Terrestrial Finder Program propose the design of a state-of-the-art "coronagraph," a telescope that blocks out the central light from a star to detect much fainter surrounding objects. "This will be far, far better a telescope than has ever been built," Traub says, "and today there are teams of people working to make such a telescope and to send it to space sometime in the coming decade."
Improvements in Face Recognition Technology
Secure access to physical and virtual spaces is becoming increasingly important for security. Passwords and PINs can be lost or forgotten. However, using biometrics (for instance a face, fingerprint or iris) for matching a live subject to a stored template, security can be improved.
At Carnegie Mellon University, Vijayakumar Bhagavatula and his team have been developing methods to achieve improved biometric verification using a tool called "correlation filters." This approach provides several advantages such as graceful degradation (part of the face can be occluded and it is still recognized), shift-invariance (images do not have to be centered) and smaller error rates. The same methods were also applied for fingerprint and iris recognition.
Making Holograms with Digital Cameras
Combining digital photography with computer number-crunching, a research group headed by Joseph Rosen from Ben-Gurion University in Israel has developed a promising new method of recording holograms of any three-dimensional scene. In addition to making it easier for industry to produce holograms, the new method can potentially give consumers the ability to make 3-D movies of events, by using digital cameras and special computer software. Conventional holographic recording requires lasers and complicated optical systems. In contrast, Rosen and his students, David Abookasis and Youzhi Li, use a standard digital camera to take a set of many pictures of the 3-D object from different points of view. The set of pictures is sent to a computer, and mathematically processed with a new algorithm developed by the researchers. The computer output is a hologram, which can be printed out on a hardcopy transparency or on a screen such as an LCD. When this hologram is properly illuminated, a real 3-D image of the original object is reconstructed in front of the viewer's eyes. According to Rosen, their hologram is the only non- laser technique that recovers all the 3-D effects of the original.
-Compiled by Philip Schewe, AIP
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