These 2D systems work well if the camera is directly in front of the person, Forrester points out. But if the face is at an angle to the camera, which happens with surveillance tapes or photos, the recognition is reduced significantly.
One problem can be caused by light casting shadows on the face, but other factors that affect 2D accuracy include facial hair, shadows, glasses, sunglasses, hats and aging.
According to suppliers, 3D systems take care of many of the problems encountered with 2D systems. These systems look at face shapes, contours, the width of the nose and depth of the eyes for up to 20,000 points.
"When you get that many points, you can even differentiate between identical twins," Forrester says.
"The match made by the software is based on a statistical score," says Paul Schuepp, president and CEO of Animetrics Inc.
"The scoring technique is part of the face recognition algorithm, and the score is about how close the incoming face image or probe comes to the face or faces in a gallery."
Certain criteria are set that define the score boundaries, so a high score means the comparison is a match or most likely, a medium score means the comparison is possible but not assured, and a low score means that it's most likely not a match.
"The point is the facial recognition software does not know if the match is definite. It's all about statistics," Schuepp says.
"This is the same for fingerprint or iris matching, but the face is the most difficult," he says. "It's ever changing with many variables such as expressions or head rotation, and the environment has an effect with lighting, shadows and background."
Atick notes that in addition to making a topographical "map" of the face for comparison purposes, a new technology emerged on the market four years ago that identifies micro-features and performs a skin texture analysis. "Every person's skin is different, like a canvas is unique for each painting," Atick says. "Now the new generation of facial recognition software can take the topography and fuse it with the skin texture signal. You get a higher accuracy and have a higher confidence that the match is correct."What's available
ALIVE Tech Inc. offers both 2D and 3D systems. "Most sheriff departments have a 2D database of mugshots," Forrester says, "but we recommend 3D systems for most law enforcement applications."
Animetrics sells facial recognition software with a family of products under called FACEngine ID, according to Schuepp.
"We have versions that do surveillance such as watch list searching in uncontrolled conditions," he says. "We offer authentication versions for access control, and we have the capability of generating a 3D rendering of a face from a 2D photo."
"The 3D information of the face is used to make our facial recognition algorithms better and work more robustly in uncontrolled conditions," Schuepp continues. "But the 3D rendering also is an useful output from a product we call FORENSICA. It is being used for the Amberview program, part of the missing children U.S. Amber Alert system."
L1 has various subsidiaries to market its own technology and offers L1 Identity Solutions for various applications the customer or department needs. For example, Identix has a well-known surveillance package called Argus. It allows real-time checks in public places to nab shoplifters and similar applications.
"Sagem offers five main kinds of facial recognition applications that may be combined to provide what a customer needs," McNeil says. These include civil enrollment, identity management, criminal identification, crime solving and covert surveillance. For instance, Sagem has a video surveillance product that performs a real-time assessment between a live face capture and a stored enrollment image.
Suppliers say there are many applications for face recognition products in law enforcement.
"The most common include searching large databases for bad guys, the most wanted or suspects," Schuepp says. "They can help with verification of travelers at border crossings, check people against blacklists, such as shoplifters, perform remote surveillance and analyze collected surveillance video."