Date: Dec 12, 2005 Source: MDA (
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Summary:
QED Technologies®, Inc. (QED), has developed a system that uses a liquid that quickly alters its physical state to solid and back to a liquid (depending on exposure to an electromagnetic field) to polish large, lightweight optics faster and more precisely. MDA funded QED's technology for its potential in large, lightweight optics for space-based and ground-based missile defense. The system should save the planners of space missions time and money, and QED, which already has thriving commercial business selling smaller systems, has been building a machine that will process large lightweight optics exceeding 1 meter in size.
Technology Description:
The instrument that QED has developed circulates a special liquid known as a magnetorheological fluid in a closed-loop filtered system. This fluid, with about the viscosity of mineral oil, travels from a nozzle toward a motion-controlled arm that holds the optic and that rests above a strong electromagnetic field. As the fluid enters the field, it almost instantly transforms into a solid state, polishing the optic as the optic is moved mechanically over the device. (For larger optics, the instrument moves over the surface of the optic, to avoid dropping or damaging the heavy optics.) The slurry-like solid maintains a clay-like viscosity while exposed to the field. After leaving the field, it returns to a liquid state. The fluid is vacuumed into a filtering system and continuously reused. The approach is called magnetorheological finishing (MRF®).
Since the system polishes on a tangent to the optic rather than by a normal direct force, the system is less likely to create defects in the mirror surface. The automated approach also offers the ability to measure and correct for print-through effect—the quilted or ridged pattern that sometimes bleeds through from the back of an optic when making it lightweight.
QED expects to process optics that will weigh less than 10 kg per square meter. (Large optics under 50 kilograms (kg) per square meter are considered lightweight.) The company's techniques also can be used to craft aspherical optics, which do not produce the aberrations of spherical optics.
QED officials say they can produce optics with a quality exceeding ?/10 or ?/20 (peak --to valley)—that is, 10 or 20 times as small as the wavelength of light at which the optic will be used. By comparison, ?/6 is typical for high-quality camera optics.
MDA Origins:
The company was awarded an MDA Phase I SBIR contract in 2003. MDA funded QED's technology for its potential in large, lightweight optics for space-based and ground-based missile defense. The company asserts that the project will address MDA needs by improving optics that the agency and its customers can use to make skyward observations as well as sky-based observations. Such sky-based observations require equipment that must be launched into space. And in launches, weight is important, since each additional pound adds significant dollars to the overall launch cost. (By way of example, a piece of glass 1 meter in diameter and 4 inches thick can weigh several hundred pounds. Removing most of the glass from the piece and leaving only a thin sheet to produce as light a piece as possible is desirable.) QED expects that ultimately MDA prime contractors would be interested in machines that could produce optics as large as several meters.
Spinoff Applications:
The high-precision technique that QED is developing will enable large optics such as mirrors for space-based telescopes to be made thinner and lighter. Lightweight optics are inherently weak or fragile, making them difficult to polish without deformation or damage. And conventional polishing of large, lightweight optics is often done manually, taking months to complete. But QED's approach, which uses interferometry and customized software to analyze optics before polishing and to guide the polishing instrument, promises to reduce the process time to only days or weeks.
Company officials also see application of their technology in the production of silicon or compound semiconductor wafers, which must be flat with as few defects as possible. According to QED, its MRF technique also could ensure uniformity of thin films applied to such wafers.
QED boasts that its technique will provide benefits in the areas of time and precision, offering cost advantages in the optics-polishing process. Also, QED's focus on producing lightweight optics should offer savings for users of large optics in satellites and other spaceborne applications, where each added pound can amount to thousands of additional dollars in launch costs.
Commercialization:
The company, founded in 1996, already sells polishing machines that can handle optics up 1 meter in size. By building on its MDA-funded work for larger, lightweight optics, QED now sells a new line of custom-built machines and company researchers are now building a machine that will process large, lightweight optics up to 4 meters in size.
For military applications, QED expects that ultimately MDA prime contractors would be interested in machines that could produce optics up to 4 meters in diameter. The company also expects its technology to find use in other industries with precision-polishing needs. Other companies have developed proprietary, automated polishing techniques, but QED officials maintain that their company's MRF technique still promises greater speed.
In QED's current product line of MRF systems, a positioning machine-tool head moves the lens into the pathway of the thin film of MR fluid that is being spun on the top edge of a wheel, with an electromagnet inside pulling the fluid against the wheel. Developing systems for larger optics (like those addressed by the MDA-funded project) would require the lens to remain fixed while the MRF system is moved.
QED claims that its emerging and existing systems can provide three key advantages over all other existing polishing systems: effective shaping (flats, spheres, and aspheres); surface integrity improvement (absence of micro-cracks); and thickness control (silicon on insulator (SOI) applications).
Company Profile:
QED is a pioneer and provider of magnetorheological finishing (MRF), delivering production-ready systems. The MR fluids were first developed in Russia by the company's research manager, who was recruited to the University of Rochester by one of the company's founders, who saw the technology's potential.
QED was founded in 1996 and already sells polishing machines that can handle optics up to 1 meter in size. To date, the company has sold more than 100 machines, each ranging in price from $250,000 to $1,000,000. As it built on its MDA-funded work for larger, lightweight optics, QED developed a new line of custom-built machines for large (i.e., up to 1 meter) optics and company researchers are now building a machine that will process large lightweight optics up to 4 meters.
QED continues to develop a line of technologies for precision finishing, providing deterministic surface-shape correction in minutes. The company has been awarded the Photonics Spectra Circle of Excellence Award, as well as the Laser Focus World Commercial Technology Achievement Award, a Department of Defense Technology Achievement Award, the R&D 100 Award, and, most recently, the American Business Ethics Award.
QED employs about 45 people (mostly technical researchers) and performs research and development, application engineering, testing, prototype design, service, and sales. Its core competencies are in the areas of magnetic fields, fluid mechanics, advanced mathematics (software), metrology and optics.
