Technological Landscapes: High-Speed Laser Scanners

During the years 1905 to 1917 the theoretical physicist Albert Einstein published papers on the special and general theories of relativity, the photoelectric effect, Brownian-motion and the theoretical basis for nuclear energy. In addition, he published the Quantum Theory of Radiation that included the statistical probability for Light-Amplification-by-Stimulated-emission-Radiation, now known as the “LASER”.

It was not until 1960 that the first working laser was invented by Theodore H. Maiman at the Hughes Research Laboratories, Malibu, California. Although the invention provided considerable excitement within industry and academia, no one knew what to do with it. Aside from burning holes in Gillette razor blue-blades to demonstrate the power of a coherent bundle of photons, it was just a spectacular beam-of-light phenomenon. Unless there was a way to move the laser beam to perform useful work it would remain a “solution looking for a problem."

In 1980, the entrepreneurs of the newly-formed company Cambridge Technology, Inc. (originally located in Cambridge, MA) discovered a way to precisely deflect a laser beam and make it a useful tool. Their patented product, called a “galvanometer” (shortened eventually to “galvo”) was capable of moving a beam of light in a controlled and precise manner. Their president, Redmond P. Aylward, noted that the precision of such a typical optical scanner -- known as a “galvo-scanner” -- was so high that the beam at a distance of one kilometer would be only off target by a millimeter, or, an error of about four-hundredths of an inch.

However, the full potential of the laser could only be realized if the galvo-scanner was designed to withstand high-optical-powers so that it would not become just another blue-blade. What was needed was the reliable and safe control of a powerful millionth-of-a-second pulsed, 10,000-watt beam of light that wants to melt every component in a system that is vibrating several thousand times a second.

The core of the galvo-scanner is the galvanometer, which is essentially a motorized mirror mount. The mirror used to deflect (steer) the laser beam is mounted on its shaft. The attached photograph illustrates a variety of Cambridge Technology galvo-scanners designed to steer laser beams that measure one-tenth to three inches in diameter.

The rest of the galvo-scanner consists of an electromechanically driven control-system that provides precise location information. There is a myriad combination of scanning possibilities available using galvo-scanners. For example, to create a two-dimensional image requires two galvo-scanners located at right angles to each other. In addition, three-axis scanners are also available to scan large two-dimensional and three dimensional surfaces. Typical high-performance scanning mirrors are designed in beryllium and are nickel plated to withstand high laser powers.

To use the terms “ubiquitous” and “laser” in the same sentence would appear to be an oxymoron. Not so. High-speed laser scanning is far more common than one would expect. The ability to rapidly remove material in a controlled and precisely located manner has created numerous applications.

The protection of jewelry through engraving is one example of this type of application. No longer are environmentally-unfriendly chemicals and consumables required if a laser scanner is used for this purpose. Tiny, yet fully legible unique designs such as photo images, lines of poetry and marriage vows can be readily laser-beam-scribedon a piece of jewelry. Serial numbers can then be added to protect against piracy.

What has become an everyday event is the LASIK eye surgery procedure used to reshape the cornea to improve our sight. The laser used for this procedure uses two galvo-scanners to control this intricate reshaping of the cornea.

A more exotic application of the Cambridge Technology galvo-scanner occurred when a three-dimensional laser system provided by Neptec, Inc., Ottawa Ontario, was deployed in orbit on a NASA Shuttle Discovery flight to find the damaged ceramic panels that protected the Shuttle from reentry heat.

Today, Lexington-based Cambridge Technology is part of the global GSI Group’s Optical Scanning Products Division (the GSI Group is headquartered in Bedford). Cambridge Technology’s galvo-derivative products are used world-wide in other diverse applications such as DNA analysis, laser entertainment, digital radiography, micro-machining and welding. The “solution looking for a problem” has been resolved through the forty-year dedicated efforts of the Cambridge Technology
pioneers.

This effort would have pleased Einstein, the theoretical physicist who predicted the laser.

“One should not pursue goals that are easily achieved," said Einstein, according to Anne Rooney's Einstein in His Own Words. "One must develop an instinct for what one can just barely achieve through one’s greatest efforts."