A4Vision's Evans countered that 3-D systems are not as dependent on ideal light, camera angles or factors such as facial hair. He added that the more expensive 3-D makes sense as customers upgrade their hardware to include more sophisticated security cameras.
Both Identix and A4Vision claim their systems are accurate enough to distinguish between identical twins.
But both have their shortcomings. Something as simple as a toothy smile -- considered "an extreme facial expression" -- can throw off either kind of recognition system.
The entire face-scanning industry is still reeling from the black eye of several failed test programs in recent years.
In one trial in 2002, a 2-D face-recognition system at Boston's Logan International Airport -- where two planes used in the Sept. 11 attacks departed -- failed to identify 39 percent of volunteers who had their images stored in the experiment's database.
"They were failures," said Atick, whose 2-D company was involved in the Logan trial. "Actually, they were good lessons for the industry, and the industry has since learned from those."
Results are improving. A U.S. government test of face systems released in 2003 found that 2-D systems correctly identified 90 percent of people who had their images stored in the database in "controlled indoor" settings, according to the Face Recognition Vendor Test of 2002. The study also found that 1 percent of the matches made were "false positives" -- the computer identified the person being scanned as a different person stored in the database.
The 2005 test is looking at 3-D scanning, but results are not yet available.
Fisch said face-scanning is still not as accurate as fingerprinting or iris scans. "Both the 2-D and 3-D need to prove they have high accuracy before they are going to have widespread deployment," he said.
But face-scanning companies say their systems are easy to use on large crowds at airports and border crossings because they don't require cooperation from the user, such as touching a fingerprint reader. They add that many people don't want to give their fingerprints because that method is associated with being a criminal.
Cameras are everywhere in modern society -- a fact that delights some and scares others.
The American Civil Liberties Union says the widespread use of face scanning could bring Big Brother-like government surveillance, where a person could be tracked by ubiquitous cameras posted in airports, shopping malls and other public areas.
"It's going to result in people being asked to account for their whereabouts all the time," Barry Steinhardt, director of the Technology and Liberty Program at the ACLU, said of the technology.
He added that law enforcement potentially could follow a person from the airport, to the shopping mall, to other public places where cameras are mounted. He sees potential abuse: "Why is that black man in the white neighborhood?"
Those selling face-scanning gear downplay those fears.
Miami International Airport has about 2,000 cameras providing security, said Jonathan Forrester, director of marketing for AWT, a Georgia-bases system integrator for security systems that sells Geometrix's face-scanning equipment.
He added that an "average citizen" in New York City may be captured by as many as 75 security cameras over the course of a day. Such systems, Forrester said, could protect people from identify theft or could help nab criminals or terrorists.
Added Atick of Identix: "The ACLU has taken the stance that the technology is bad. Society has a right to determine where it's needed. We have cops, but we don't deploy them in the bedroom."
Evans sees the technology becoming more widely accepted. A4Vision -- which still collects around 65 percent of its revenue from test programs, not actual deployments -- is backing a proposed international standard for 3-D technology. It's a process that he said should take no more than two years.
In the meantime, he knows what customers want: "Speed is everything with this. Accuracy is everything with this."