The electromagnetic spectrum, from radio waves to gamma rays, provides numerous “windows” through which to examine the world. Each band of frequencies offers different kinds of information that can be used for science and technology. At the border between radio waves and infrared light lies the extremely high frequency (EHF) band of radio waves. These waves have frequencies of 30–300 GHz, corresponding to wavelengths between 1 mm and 10 mm, and, thus, are commonly called millimeter wave.

Millimeter wave technology has important applications in communications, radar and radio astronomy, but a newer class of applications uses millimeter waves as an imaging technology. Many organic materials are relatively transparent to millimeter waves, thus the primary use for millimeter wave imaging is in security screening. These imaging systems can image a person’s shape regardless of clothing, allowing security personnel to identify threats or contraband.

There are two main types of millimeter wave products for security purposes, individual body scanners and passive monitoring systems. A body scanner is a booth in which passengers are scanned one at a time. These are active systems that have both millimeter wave generators and detectors. The systems inspect the subject from different angles, and then reconstructs the data into a three-dimensional image that can be reviewed by an operator.

Passive millimeter wave systems use the fact that warm bodies give off millimeter waves naturally, so a detector can use a subject’s own thermal emissions for imaging purposes. Passive systems can be incorporated into individual portals, or used in a standoff mode to identify threats in a crowd of people.

Although security makes up the primary application for millimeter wave imaging, other applications have been explored in academia and research labs. Millimeter wave imaging can be used in the nondestructive testing of construction materials or other samples for defects and corrosion, but these applications have not become very significant. Another application is in the clothing industry. Following its acquisition of Intellifit in 2009, Unique Solutions Design markets the Intellifit VFR (virtual fitting room), a booth-style system that uses millimeter wave imaging to provide sizing information for custom-made clothing.

In 2009, the total market for millimeter wave imaging was about $40 million, but the market is expected to grow tremendously in the next few years. In February, millimeter wave market leader L-3 Communications received a $165 million indefinite delivery order from the US Transportation Security Administration for millimeter wave security products. Other important security market participants include QinetiQ, Smiths Detection, Brijot Imaging and Millivision, in which L-3 has a minority interest. Walleye Technologies has a stronger emphasis on nondestructive examination than other vendors, which are primarily involved in the security market.

Millimeter Wave Imaging at a Glance:

Leading Suppliers

• L-3 Communications

• QinetiQ

• Smiths Detection

Largest Markets

• Security

• Nondestructive Testing

• Custom Clothing

Instrument Cost

• $125,000–$300,000