Each of the different wavelengths of light travel a different distance into the skin before being reflected back to the reader's digital camera. After five pictures have been taken, software analyzes how the wavelengths of light were changed by their trip through the skin and calculates the finger's ''spectral signature,'' as Dr. Rowe calls it.
With financing from the National Institute of Standards and Technology, researchers at Cross Match were simultaneously developing their own under-the-skin method. But instead of analyzing the effect skin has on light waves, the Cross Match system sees what happens to extremely high-frequency sound waves when they make a similar journey.
While the ultrasound system works, Mr. Murray said, it is such a dramatic change in approach that developing products based around it will take time.
Lumidigm has run into delays as well. While the company clearly demonstrated that its system could distinguish human fingers from fakes, it was also clear that the idea of substituting spectral signatures or blood vessel patterns for surface finger prints will take some time to gain acceptance.
Through a licensing agreement, the two companies have found what they hope will be a short-term solution to their problems. Cross Match plans to build a hybrid reader that will examine fingerprints the traditional way while using the Lumidigm technology to expose fakes. Because it uses standard components, Mr. Murray said the device should be available for sale next year. At the same time, because it also relies on the traditional method of matching fingerprint databases, the new device can be used with current security systems with little modification.
Mr. Murray at Cross Match predicts that while the device will initially be of interest to government departments like homeland security, corporations will ultimately be its biggest market. Businesses that require criminal background checks are increasingly using fingerprint scanners as part of the hiring process, he said.