Skin spectroscopy recognizes skin by its optical properties. The system uses a sensor to illuminate a small patch of skin with multiple wavelengths of visible and near-infrared light. The light is reflected back after being scattered in the skin and is then measured for each of the wavelengths. The system analyzes the reflectance variability of the various light frequencies as they pass through the skin.
Because the optical signal is affected by chemical and other changes to the skin, skin spectroscopy also provides a sensitive and relatively easy way to confirm that a sample is living tissue.
Limitations. This type of system is best used for applications with moderate environmental conditions since having to require users to remove gloves could slow down the access control process to unacceptable levels.
Applications. This technology is ideally suited to layering in dual biometric systems, helping to build ultra high-performance systems that measure two or more independent biometric identifiers. Because skin spectroscopy-based systems require contact with skin, fingerprint sensors and hand/finger geometry systems are particularly compatible with it.
Some vendors’ sensors can operate on nearly any portion of the skin, making them ideal for integration into consumer products in ways that easily and conveniently ensure security. Initial designs show system sensors to be small, fast, and durable. Their low cost and low power consumption, and the algorithm’s processing efficiency and low memory requirements, make this technology promising for use in portable devices if it is perfected. Smart phones, PDAs, and other mobile products could provide general-purpose authentication capability for applications ranging from m-commerce to physical security.
Vein biometric systems (also called vascular pattern recognition systems) record subcutaneous infrared absorption patterns to produce distinctive identification templates. Veins and other subcutaneous features present large, robust, stable, and largely hidden patterns that can be conveniently imaged within the wrist, palm, and dorsal surfaces of the hand.
The user places his hand under an imager, which takes an image of the back of the hand. The main dorsal blood vessels have higher temperatures than the surrounding tissue, so they appear brighter in the image. The system carefully selects the region of interest of the hand and extracts the vein patterns. After it reduces the noise reduction, it separates the vein patterns from the background. Since blood vessels grow as people grow, only the shape and distribution of the veins is considered.
Limitations. Obviously, extremely dirty hands cannot easily be identified using a vein pattern recognition system. Also, current systems use cameras that are not portable—or certainly less portable than other technologies.
Applications. The technology can be applied to small personal biometric systems and to generic biometric applications, including intelligent door handles and locks.
Some businesses are using vein recognition technology for such applications as time and attendance (to prevent buddy punching), allowance and payment control, login and information protection, safe deposit box access, e-commerce, and membership management.
This developmental system works by exploiting the natural level of salt in the human body. The system uses an electric field and salt’s natural conductivity to measure a tiny electrical current that is passed through the body. (The electrical current is approximately one-billionth of an amp, which is less than the natural currents already present in the body.) Speeds equivalent to a 2,400-baud modem have been claimed, yielding a data transfer rate of up to 400,000 bits per second.
Applications. Applications for this kind of biometric technology could include authentication of data transfer devices carried on the body, such as watches, mobile phones, and pagers. Also, applications could include “waking up” household appliances or devices as one enters a room.
Facial thermography refers to the pattern of heat in the face caused by the flow of blood under the skin. IR cameras capture this heat to produce a thermal pattern. Because the vein patterns in a person’s face are distinctive to each person, the IR thermal pattern they produce is also distinctive.
Limitations. While the underlying vein and tissue structure is stable, the dynamic nature of blood flow causes fluctuations and the appearance/disappearance of secondary patterns. Environmental conditions (such as ambient temperature) and the introduction of alcohol or drugs, for example, can alter the thermal signature of the face.
Applications. This technology is better suited to determine “liveness” of the subject (no thermal image indicates no life) than identification. Facial thermography, used in conjunction with other biometric technologies, could indicate a rested or fatigued person or determine physical condition, although this has never been demonstrated in any commercially available technology.
One major technical advantage of this technology is that it does not use infrared illuminators but rather relies on the infrared emissions generated by the face itself. This capability is extremely useful in surveillance applications, especially when it is necessary to detect people in dark places or at night.