Currents


Machine revolutionizes lens-making

Engineers from the University and seven corporate partners, working with the U.S. Department of Defense, have developed the first system to automate the manufacture of unusually shaped lenses known as aspheres.

The development means aspheric lenses can be produced in minutes, not days, at a fraction of the current cost, say officials at the Center for Optics Manufacturing.

The savings in time and money will trickle down to products ranging from 35mm cameras and medical endoscopes to military-grade night-vision goggles.

High costs--up to $4,000 for a meticulously formed, doorknob-sized piece of glass--have limited the use of aspheres, despite their ability to deliver much better optical performance and image quality than traditional spherical lenses. The new asphere machining system greatly streamlines production; engineers believe the machine will push costs down to as little as $25 to $100 per lens.

"There isn't an optical device around that wouldn't benefit from aspheres," said Harvey Pollicove, director of COM, which is now testing the new machine. "Aspheres are used in nearly every application for which they're affordable, and every engineer who designs optical devices wants to use them."

Aspheres are well suited for a wide range of consumer goods, including compact disk players, photocopiers, and projection televisions; top-rated cameras and video camcorders now rely on three or four aspheres to achieve lightweight, compact designs with improved image quality.

Beyond the consumer realm, aspheres are used in virtual reality helmets, professional-quality movie cameras, surgical lasers, bar-code laser scanners, and in endoscopes to see inside the body.

The new machine might also provide a cheaper way to produce aspheric elements that are found in the $500,000 lenses now used to make computer chips by tracing out integrated circuits on wafers of silicon.

"Aspheres are better than spherical lenses in these applications because they bend light rays more precisely," said Donald Golini, president of the Rochester optics firm QED Technologies, which was not part of the consortium that developed the asphere grinder.

An aspherical lens or mirror focuses incoming rays to a single point, while spherical lenses cause blurring.

Since it focuses light more precisely, a single asphere can take the place of two or more spherical elements in many optical devices, such as night-vision goggles worn by soldiers. Replacing bulky groupings of three or four spherical lenses with an asphere or two would make the goggles 30 percent smaller and lighter, Pollicove says, while boosting image quality and resolution.

But aspheres' subtly irregular curves make them a real chore to produce. Most of today's manufacturers use a process Golini describes as "home-grown," rigging up expensive machines like high-precision lathes for double-duty as asphere grinders. The final painstaking round of hand-smoothing, known as "lapping," done by specialized artisans, can take hours or even days. The new process takes only 15 to 30 minutes.

"There's now no efficient way, and certainly no single machine, for making high-precision ground aspheres from start to finish," Golini said.

He expects that much of the demand for the new grinder will come from large companies that spend heavily on hand-crafted templates while developing new products.

"Since this new system will reduce initial tooling costs, it will make all plastic and glass molded aspheres more affordable, and it's much better suited to the task of producing high-precision aspheres than any of the previous techniques," Pollicove said.

"We've incorporated several new technologies into this machine," said Kevin Uhlig, vice president of machinery systems at Bridgeport, Conn.-based Moore Tool Co., the firm that built the new asphere grinder. "It's the first machine to fully automate asphere production; earlier machines couldn't muster the precision needed to shape aspherical lenses. It's also the first to successfully tackle the final round of smoothing, typically done by hand."

The machining system is expected to sell for about $250,000--roughly $100,000 less than the cost of the techniques now used to produce aspheres. COM is testing the wardrobe-sized, computer-controlled grinder, and Moore will begin selling the machine later this year.

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Last updated 7-27-1998
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