Market profile: multispectral imaging.

When a team of Brigham Young University researchers was invited to Herculaneum to resurrect writing from excavated scrolls, many' of the participants were skeptical. Not only were the papyrus fragments 2,000 years old, but they had been cooked and pressed into solid black discs when the city was overrun by ash and lava in 79 A.D. In spite of the dismal condition of the texts, scientists using multispectral imagers outfitted with special filters were able to decipher the words buried under layers of seemingly impenetrable carbon.

The dramatic results produced by multispectral imaging are based on a fundamental scientific principle--different biological substances will reflect light at different wavelengths. The human eye is capable of detecting light only in a short wavelength range, from about 400 to 700 nm. A light-sensitive instrument implanted in an imager called a charge coupled device, or CCD, can extend the range of detectable wavelengths into the near infrared, to about 1,100 nm. By pairing a CCD with filters that limit the captured light to a band as narrow as 10 nm, scientists can observe even minute compositional anomalies, such as the residue of ink embedded deep within old rolls of paper.

Originally created by NASA for analyzing planetary surfaces, multispectral imaging has in the years since found its way into a myriad of research and industrial roles. While imagers are still installed in satellites to bore down through fog and cloud cover and to identify variations in the Earth's topography, they have proven equally useful in more commonplace tasks like inspecting truck brakes at weigh stations; pinpointing weed-laden sections of fields for spraying; grading meat and produce; identifying sources of radiant heat; and ensuring product size consistency quickly and accurately, regardless of differences in color.

Over the last few years, the imaging industry has undergone consolidation, in particular under the aegis of Roper Industries. In November 1999, Roper acquired Redlake, a prominent digital motion analysis and imaging company, $9 million. Last year, in an effort to further increase its color and multispectral product lines, Redlake bought DuncanTech, a leading camera producer.

To collect data, most cameras use one of two methods: a single sensor and multiple receptors to detect red, green and blue color bands; or a spinning filter wheel to capture the colors sequentially. While a filter wheel can produce better resolution, it can create blurry images if the target is moving.

DuncanTech's MS4100 camera--its top-of-the-line model--includes three separate CCD sensors and boasts a resolution of 6.2 million pixels. It can be configured for RGB imaging, which allows for high-quality color pictures, or color-infrared (CIR), which is suitable for multispectral uses.

In many ways, though, multi-spectral imaging remains a niche market and a significant number of companies producing cameras and accessories are very small. The Los Angeles-based Tetracam, for instance, builds low-cost multispectral cameras for agriculture. Its Tetracam ADC enables users to take either red/green or near infrared photographs. While manufacturers like Tetracam tend to design cameras for specific fields, many are also willing to construct custom models for customers. Other manufacturers include FLIR Systems and the French company CEDIP Infrared Systems.