The airport in Oakland is set to become one of the first in the nation to increase its post-Sept. 11 security by deploying face-recognition technology, which is expected to get increased use in reaction to the terrorist attacks.

The Oakland system will not be used to scan crowds in the airport or to check passengers as they check in or board planes, a prospect that has been criticized by privacy advocates and civil liberties groups.

For now, the new system will be used only in interrogation rooms behind the scenes, to match suspects brought in for questioning to a database of wanted criminals' pictures.

Oakland police would like such a system in terminals as well, and are weighing their costs.

"As a result of the Sept. 11 incident, this would give us added capability of identifying someone," Sgt. Mark Schmid, manager of the Oakland police technology unit, said Wednesday.

The systems clearly are coming soon — one is already in place at Keflavik International Airport in Iceland, and at least two companies say they will be installing scanning cameras in major U.S. airports in coming weeks.

The Oakland system is expected to be up and running in about six weeks. It is made by Imagis Technologies of Vancouver, British Columbia, which has a $2.65 million contract to sell facial-recognition technology to Alameda County agencies. The company has deployed a similar behind-the-scenes facial recognition system at the Toronto airport.

Facial recognition cameras work by capturing an image of a face and translating it into a chunk of data that can be compared with records on file.

They are part of the growing field of biometrics, which is the identification of people by personal characteristics such as fingerprints, hand shape and voice and eye patterns. Several airports use biometric systems to grant and restrict employee access and to speed passengers through immigration checkpoints.

Police in Florida came under fire this year for using video cameras at the Super Bowl to take pictures of faces in crowds and run them through a criminal database.

Biometrics experts say face-recognition surveillance systems have severe limitations in crowded places — such as airport terminals — because the lighting has to be just right and a person has to be close to the camera and looking at it. The Defense Department is looking for ways to improve the technology.

But companies that make the systems say they would work well at airport security checkpoints and ticket counters. "It's a controlled environment," said Iain Drummond, Imagis' CEO.

The company that supplied that Super Bowl system, Viisage Technology Inc. of Littleton, Mass., said last week it had been chosen to install face-recognition cameras in a major airport it could not publicly reveal. CEO Tom Colatosti said Wednesday that the scanning cameras will perform their surveillance at security checkpoints.

Similarly, Visionics Corp. of Jersey City, N.J., soon will be deploying face-recognition cameras at "very visible" U.S. airports, said Joseph Atick, its chief executive. Such steps would increase security far more than the measure Oakland has taken, he said.

"It is a valuable tool," he said, "but not to be confused with scanning every passenger that steps in front of the camera."