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Tuesday, 9 de December de 2008

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3D face scans by lasers may help spot terrorists

A new research has suggested that 3D laser scans of peoples faces could be a more strong option in spotting terrorists.

Security services around the world are devising software to match CCTV photos of faces with image archives, to catch known criminals and terrorists.

However, the technology struggles to overcome problems caused by variations in lighting and the position of peoples faces between photos.

Now, according to a report in New Scientist, a US research suggests that 3D laser scans could be a more robust option in tricky real-world conditions.

Dirk Colbry, at Arizona State University, and colleague George Stockman at Michigan State University, took 300 laser scans of 111 different faces using a commercial scanner.

The devices stationary camera records a series of images while a horizontal plane of laser light passes over a persons face.

Software then extracts a three-dimensional model of the face from the photos.

Colbry and Stockman showed that they could match different scans of the same face even when lighting was different, or the angle from which the images were taken was off by as much as 30 degrees.

Facial recognition accuracy is gauged by a figure called equal error rate - the point at which false positives equal false negatives.

The 3D scans achieved a figure of 1 percent, which is considered good for facial recognition systems.

The software recognizes faces by matching anchor points, such as the tip of the nose or the corners of the eyes, in two photos or 3D scans.

Anchor points in 2D images appear to be more strongly affected by differences in lighting or angles than in 3D images, according to Colbry.

According to William Smith, a lecturer on computer vision at the University of York, the new work confirms that 3D images can be useful for verification.

Colbry said that scanners could eventually capture profiles without the subjects suspecting.

Security checks often force people to stand still in queues, providing good opportunities for covert imaging, he said.