Explainer: Hand Geometry Recognition
Hand geometry recognition is the longest implemented biometric type, debuting in the market in the late 1980s. The systems are widely implemented for their ease of use, public acceptance, and integration capabilities. One of the shortcomings of the hand geometry characteristic is that it is not highly unique, limiting the applications of the hand geometry system to verification tasks only.
Hand geometry systems have the longest implementation history of all biometric modalities. David Sidlauskas developed and patented the hand geometry concept in 1985 and the first commercial hand geometry recognition systems became available the next year. The 1996 Olympic Games implemented hand geometry systems to control and protect physical access to the Olympic Village. Many companies implement hand geometry systems in parallel with time clocks for time and attendance purposes. Walt Disney World has used a similar “finger” geometry technology system for several years to expedite and facilitate entrance to the park and to identify guests as season ticket holders to prevent season ticket fraud.
The devices use a simple concept of measuring and recording the length, width, thickness, and surface area of an individual’s hand while guided on a plate. Hand geometry systems use a camera to capture a silhouette image of the hand. The hand of the subject is placed on the plate, palm down, and guided by five pegs that sense when the hand is in place.
The resulting data capture by a Charge-Coupled Device (CCD) camera of the top view of the hand including example distance measurements.
The image captures both the top surface of the hand and a “side image” that is captured using an angled mirror. Upon capture of the silhouette image, 31,000 points are analyzed and 90 measurements are taken; the measurements range from the length of the fingers, to the distance between knuckles, to the height or thickness of the hand and fingers. This information is stored in nine bytes of data; an extremely low number compared to the storage needs of other biometric systems.
The enrollment process of a hand geometry system typically requires the capture of three sequential images of the hand, which are evaluated and measured to create a template of the user’s characteristics. Upon the submission of a claim, the system recalls the template associated with that identity; the claimant places his/her hand on the plate; and the system captures an image and creates a verification template to compare to the template developed upon enrollment. A similarity score is produced and, based on the threshold of the system, the claim is either accepted or rejected.