Application Briefs

Improving Lens Performance With Transmitted Wavefront Error Testing

During design and manufacturing, optical systems and lenses are toleranced and tested to ensure the smallest possible performance error. Matching most optics manufacturing companies’ capabilities, lenses are traditionally toleranced with individual surface specifications — surface power and irregularity, or form, error. These tolerances and the associated tests control performance of a single surface, not the entire lens. Because lens designs are built around transmission characteristics such as spot size and RMS wavefront error, the performance of the entire lens, not the individual surfaces, is the true target. Transmitted wavefront error (TWE), which is the error in transmission of light through a lens, is the true target. For aspheric surfaces, traditional single-surface, three-dimensional surface form metrology is not easy. Aside from testing the true target, it may be easier and faster to make use of TWE for aspheric lenses. Using innovative metrology and developing a feed-forward manufacturing strategy, tolerancing and testing TWE can reduce risk in optical designs, improve performance and reduce cost and lead time.

Posted in: ptb catchall, Applications, Photonics, Application Briefs

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Brake System Development Accelerated With 3D Modeling

Tractair Ltd., based in Brough, UK, designs, manufactures and installs air and hydraulic brake systems for special applications. The company works closely with the design engineers of major international tractor manufacturers and other OEMs to ensure that the braking systems are fully integrated. The company has been closely involved in the development of air brakes for agricultural and other off-road vehicles since 1985 and continues to adapt available technologies to meet the demands of increasing loads and speeds handled by agricultural and construction vehicles, both on and off the highway.

Posted in: Applications, Motion Control, Application Briefs

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Motor System Enables Elevators to Ride Smoothly

Many factors have contributed to the fact that in the past five years, home elevator sales have doubled. These include the aging of the affluent baby-boom generation. In the next five years, an estimated 70 million people will be of retirement age; many of them will be looking at retaining their independence by staying in their own homes and adding features such as elevators to make living more accessible, or moving to customized homes that already include such advantages. According to a Florida State University study, a home elevator can add 10% to the selling price of a home.

Posted in: Applications, Motion Control, Application Briefs

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Spectrometer Selected for NASA Mission to Search out Lunar Water

QE65000 spectrometer Ocean Optics Dunedin, FL 727-733-2447 www.oceanoptics.com Scheduled to launch from NASA’s Kennedy Space Center (KSC) in Florida in October of 2008, the LCROSS (Lunar Crater Observation and Sensing Satellite) mission will venture to the Moon’s south pole. The mission will carry equipment from Ocean Optics named ALICE to help analyze the makeup of the lunar craters, with the goal of locating water below the Moon’s surface. The LCROSS mission will send a rocket crashing into the Moon at twice the speed of a bullet in order to study the resulting ejecta cloud. The impact is expected to generate a 2.2-million-pound plume of matter, which another spacecraft carrying ALICE will fly through, looking for signs of water and other compounds. Measuring the reflectivity of the plume, ALICE will enable scientists to distinguish between water vapor, water ice, and hydrated minerals with molecularly bound water.

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NASA Advanced Life Support Systems Group Uses Water Reclamation Prototype

DynaJets® and DynaSwirl® cavitating jet technologies DynaFlow Jessup, MD 301-604-3688 www.dynaflow-inc.com Water is a critical product of any life support system. An estimated 12,000 kg of expendables are required to sustain a single person in space for one year, of which water comprises 86%. It is therefore imperative that water be recycled in an efficient manner. Technology used on the International Space Station consisting of conventional physico-chemical processes has a water recovery efficiency of 80 to 90%. But the level of resupply and use of expendables remains too large for longduration remote space applications.

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Ruggedized Hard Disk Drives Keep Data Safe In Harsh Environments

Conventional hard disk drives (HDDs) are designed to reliably operate in the hospitable physical surroundings of interior deployments, which are typically characterized by mild temperatures, stable humidity and modest levels of vibration. By contrast, outdoor and mobile storage environments can entail anything from sweltering heat or sub-zero frost to oppressive dampness and pounding vibration. And all may be encountered miles above sea level. So it’s no surprise that bringing the benefits of HDD-based storage to outdoor and mobile settings such as automotive, industrial PC, field computing, and military applications poses a formidable challenge to engineers.

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Nanotechnology’s Role in Mid-Infrared Laser Development

Progress in developing improved semiconductor lasers with emission in the mid-IR spectral region (≈3 μm to ≈15 μm) has depended heavily on the use of nanometer-scaled structures. Mid-IR quantum cascade lasers (QCLs), for example, represent a “tour de force” of semiconductor nanotechnology where large band gap GaAs and InP based III-V semiconductor multiple quantum well (MQW) structures are used to engineer intersubband transition energies that enable mid-IR photon emission. First developed at Bell Labs and now demonstrated by many other groups, QCLs have offered great hope as a new mid-IR light source for applications such as trace gas sensing [1] and isotope ratio measurement [2]. However, from their first use [3], QCL operation has been complicated by high power inputs, typically a minimum of 5 watts, and associated high heat load in packaged systems. Considering the significant resources devoted to QCL development and the apparent lack of progress in reducing high power consumption levels over the last ten years, it is likely that this problem is fundamental to QCL design. QCLs require high applied voltages (>8 volts) to achieve the necessary band alignment and the cascade effect, so focusing on this contribution is not expected to be fruitful. The other contribution, high threshold current (≈300 mA), appears to be fundamental to all intersubband lasers where there are parallel energy versus momentum dispersion relationships for electrons associated with intraband laser transitions. Figure 1, which depicts E vs. k subband dispersion for a three-level QCL gain medium, shows that there is an efficient competing non-radiative relaxation pathway for excited electrons when they scatter with non-zone-center optical or acoustic phonons. Since low energy subband separation is required for mid-IR light emission and the sub-band dispersions are parallel, such electron-phonon scattering will always be an efficient upper laser state depopulation mechanism thus necessitating high electron currents to achieve population inversion. Note, as indicated in Figure 1, the deliberate use of electron-phonon resonance with longitudinal optical (LO) phonons in QCL designs to depopulate the lower laser transition subband states. Exploitation of such electrophonon resonance effects in reducing laser threshold currents will be discussed below within the context of interband IV-VI mid-IR lasers.

Posted in: ptb catchall, Applications, Photonics, Application Briefs

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