Tech Briefs

Optically Driven Deformable Mirrors

There is no wiring on the back sides of these mirrors. NASA’s Jet Propulsion Laboratory, Pasadena, California Optically driven deformable mirrors may eventually supplant electrically driven deformable mirrors in some adaptive-optics and active-optics applications. Traditionally, the mirror facets in electrically driven deformable mirrors are actuated, variously, by means of piezoelectric, electrostrictive, microelectromechanical, liquid-crystal, or thermal devices. At least one such device must be dedicated to each facet, and there must be at least one wire carrying a control or drive signal to the device. If a deformable mirror comprises many (e.g., thousands) of facets, then wiring becomes a major problem for design, and the problem is compounded in cases of piezoelectric or other actuators for which high drive voltages are required. In contrast, in optically driven mirrors, the wiring problem is eliminated.

Posted in: Briefs, ptb catchall, Tech Briefs, Photonics

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Automatic Alignment of Displacement-Measuring Interferometer

Corrections are derived from fluctuations associated with circular dithering of a laser beam. NASA’s Jet Propulsion Laboratory, Pasadena, California A control system strives to maintain the correct alignment of a laser beam in an interferometer dedicated to measuring the displacement or distance between two fiducial corner-cube reflectors. The correct alignment of the laser beam is parallel to the line between the corner points of the corner-cube reflectors: Any deviation from parallelism changes the length of the optical path between the reflectors, thereby introducing a displacement or distance measurement error.

Posted in: Briefs, ptb catchall, Tech Briefs, Photonics, Measurements, Electronic control systems, Lasers, Test equipment and instrumentation

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Even Illumination From Fiber-Optic-Coupled Laser Diodes

Emerging light beams would be shaped by diffractive fiber-optic tips. Marshall Space Flight Center, Alabama A method of equipping fiber-optic-coupled laser diodes to evenly illuminate specified fields of view has been proposed. The essence of the method is to shape the tips of the optical fibers into suitably designed diffractive optical elements. One of the main benefits afforded by the method would be more nearly complete utilization of the available light.

Posted in: Briefs, TSP, ptb catchall, Tech Briefs, Photonics, Exterior lighting, Fiber optics, Lasers

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Excimer Leverages Litho Lessons for kHz Micromachining

Features developed for lithography light sources are creating a mid-tier excimer laser niche. Coherent, Santa Clara, California Ultraviolet lasers currently are used in a very diverse range of industries and applications. This is because their high-energy photons directly can break inter-atomic bonds in many materials, and the short wavelength enables a high degree of spatial resolution (see Figure 1). Amongst ultraviolet lasers, excimers are unique in their ability to deliver a combination of high pulse energy and high average power. Because of these advantages, excimers are used in applications as diverse as ophthalmic corrective procedures, low-temperature silicon annealing for flat-panel displays, drilling inkjet nozzles, and treating the cylinder liners of diesel engines for greener automobile performance.

Posted in: Briefs, ptb catchall, Tech Briefs, Photonics, Lasers, Manufacturing equipment and machinery, Reliability

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Solving Complex Engineering Challenges of Large Composite Aerostructures

Large-scale composite parts present unique design and manufacturing challenges in aerospace.Composites are becoming the material of choice for the manufacture of large, complex aerostructures. The aft section of the jumbo Airbus A380 and the wings of the military transport Airbus A400, for example, are all made of carbon-fiber composites. Boeing, for the first time, is building an all-composite airframe and wings for its groundbreaking 787 airliner. Because of these and other recent manufacturing achievements, there is little doubt that composite materials will be used extensively in many future aircraft programs — from wide-body jets and commercial airliners to regional, business, and “very light” airplanes.

Posted in: Briefs, Manufacturing & Prototyping

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Repairing Fractured Bones by Use of Bioabsorbable Composites

Less surgery would be necessary, and full strength would be restored sooner.A proposed method of surgical repair of fractured bones would incorporate recent and future advances in the art of composite materials. The composite materials used in this method would be biocompatible and at least partly bioabsorbable: that is, during the healing process following surgery, they would be wholly or at least partly absorbed into the bones and other tissues in which they were implanted. Relative to the traditional method, the proposed method would involve less surgery, pose less of a risk of infection, provide for better transfer of loads across fracture sites, and thereby promote better healing while reducing the need for immobilization by casts and other external devices. One requirement that both the traditional and proposed methods must satisfy is to fix the multiple segments of a broken bone in the correct relative positions. Mechanical fixing techniques used in the traditional method include the use of plates spanning the fracture site and secured to the bone by screws, serving of wire along the bone across the fracture site, insertion of metallic intramedullary rods through the hollow portion of the fractured bone, and/or inserting transverse rods through the bone, muscle, and skin to stabilize the fractured members. After the bone heals, a second surgical operation is needed to remove the mechanical fixture(s). In the proposed method, there would be no need for a second surgical operation.

Posted in: Briefs, TSP, Bio-Medical, Medical

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An Alternative for Emergency Preemption of Traffic Lights

This system resolves potential conflicts among emergency vehicles.An electronic communication and control system has been developed as a prototype of advanced means of automatically modifying the switching of traffic lights to give priority to emergency vehicles. This system could be used alternatively or in addition to other emergency traffic-light-preemption systems, including a variety of systems now in use as well as two proposed systems described in “Systems Would Preempt Traffic Lights for Emergency Vehicles” (), NASA Tech Briefs, Vol. 28, No. 10 (October 2004), page 36. Unlike those prior systems that depend on detection of sounds and/or lights emitted by emergency vehicles, this system is not subject to severe range limitations. This system can be retrofitted into any pre-existing traffic-light control system, without need to modify that system other than to make a minimal number of wire connections between the two systems.

Posted in: Briefs, TSP, Electronics & Computers

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