Hope you don't mind whether a federal officer sees how you look beneath your clothes, because Raleigh-Durham International Airport is about to get seven more full-body scanners.

The Transportation Security Administration has been using just one scanner at RDU, at the Terminal 2 checkpoint, since 2008. In the next several months, others will be installed in Terminals 1 and 2. It's part of a plan to put 450 more full-body scanners in operation at U.S. airports by the end of the year, with another 500 coming in 2011.

The machines create three-dimensional video images with electromagnetic waves that penetrate clothing and bounce off the body. The pictures reveal the traveler's skin - and any dense object such as a harmless wallet or a hidden knife.

"The advantage these machines offer is the ability to screen passengers for both metal and non-metallic items that can be concealed beneath their clothing, and to do it without touching them," said Jon Allen, a TSA spokesman based in Atlanta.

The TSA began using body scanners a few years ago for secondary screening of travelers who might trip an alarm in the walk-through metal detector - and for other travelers that TSA says are selected at random.

Other travelers have been subjected to a physical pat-down, and Allen said that is still an option for anyone who objects to a full-body scan.

When the new scanners are installed this year, the TSA will start using them for primary screening as an alternative to the metal detectors.

The scanner now at Terminal 2, which looks like an oversize glass telephone booth, will be moved out front alongside the metal detectors. All new scanners installed at airports this year will be used in the same way, Allen said.

Some travelers will continue to walk through the metal-detector portal as their carry-on bags are X-rayed. Others will skip the metal detector and step into the scanner booth instead.

It takes about 5 seconds to record a body image, and another 10 to 12 seconds for a TSA worker to examine it.

Where travelers now remove keys, belt buckles and other metal items for the walk-through metal detector, the full-body scanner will require additional preparation, Allen said. Wallets and other dense, non-metal items also will have to be removed in advance.

The cost of safety?

Civil libertarians have criticized the body scan as a virtual strip-search. But travelers at RDU and other airports have repeatedly said they accept checkpoint delays and intrusive searches as part of the cost to keep air travel safe.

The TSA says it takes steps to protect privacy. The body-scan image is viewed only by an officer in a remote room, where he or she cannot see the traveler who is being screened. Facial images are blurred. And the TSA says the images cannot be printed, shared or saved.

Charlotte-Douglas International Airport, which has two full-body scanners at its B and D checkpoints, is also on the list to receive more machines this year. While Raleigh-Durham uses what is called millimeter-wave scanning technology, TSA agents get similar results at Charlotte and some other airports with X-ray "backscatter" imagery.

Kimberly Walton, a TSA attorney, said RDU should have the seven new machines by the end of summer. She discussed the scanner plans during a meeting May 14 at an Apex mosque between representatives of several federal agencies and members of the local Muslim community.

Walton said the TSA is testing automatic recognition technology that might eliminate the need for human officers to examine the images. This could ease the concerns of modest travelers, she said.

Allen said that in the past year, the TSA's full-body scanners have caught 60 travelers attempting to conceal narcotics, weapons or other illegal items inside their clothes.

bruce.siceloff@newsobserver.com or 919-829-4527.