Image analysis – Applications – Personnel identification
Reexamination Certificate
1999-06-17
2003-12-23
Ahmed, Samir (Department: 2623)
Image analysis
Applications
Personnel identification
Reexamination Certificate
active
06668071
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The field of the invention relates to systems for optical identification and verification of personal identity. More particularly, this invention relates to the optical scanning of fingerprints (dactyloscopical systems) for personal identification as required in such areas as computer technology, criminology, medicine, banking, finance, security, admittance-control systems and firearm safety locks.
2. Description of the Related Art
There are several prior art optical security systems which store, process and identify fingerprint patterns by electronic devices. Optical dactyloscopical systems can be divided into two groups according to their functional capabilities: (1) systems that read fingerprint images from intermediate data storage units, such as, for example, traditional dactyloscopical cards (fingerprint cards) and utilize various types of tables to classify the fingerprints (see MORPHO Systems leaflet of 1992); and (2) systems obtaining dactyloscopical information directly from the finger, i.e. the so-called “live scanners.”
These two groups differ greatly from each other. First, the surface texture of data storage units, which can be dactyloscopical cards or dermal ridge patterns of a fingertip, may differ. The area of application constitutes the second major difference between the two groups.
Systems of the first group are used mainly by police and criminologists for the purposes of personal identification of criminals. Dactyloscopical cards are used along with the tracks collected at a crime site. However, these systems are not suitable for immediate identity verification. Regular scanners such as designed by Morpho Systems, are currently used to read such dactocards and tracks (see MORPHO Systems leaflet of 1992). However, these types of systems cannot process information available from dermal ridge patterns of a live fingertip.
Moreover, the use of fingerprint cards causes a considerable loss of information because registration and processing of each and every small detail of dermal relief is limited.
Systems of the second group, which process optical dactyloscopical information obtained from a “live” finger, may be subdivided into the following categories:
Category 1—Systems operating in reflected light; and
Category 2—Systems operating in penetrating light.
This subdivision is based on the functional principles of the system at the initial stage of transformation of the dactyloscopical image. For example, over the last ten years, systems such as one designed by Digital Biometrics utilizes miniature cameras and charge transfer devices (CCDs) to detect the reflected part of light from a finger surface.
These reflection-type operating systems take advantage of the effects associated with the complete inner reflection of the light, i.e., light that is reflected just from those places of the prism surface at which the dermal ridges of a finger directly contact the prism surface.
The dactyloscopical camera uses a series of lenses to fix the reflected image of the dermal pattern. Such reflection systems have many advantages over systems utilizing dactocards. Reflection systems allow for quick scanning and processing of information, and a user's fingers are not soiled from ink or ultraviolet-type stamping. However, these reflection systems also have some disadvantages due to their mode of operation. Some of these disadvantages are discussed below.
One disadvantage is that when a scanned finger is dry, the picture quality is reduced. This reduced quality results in a low probability of identification. The reason that a dry finger creates a problem is that when it touches the contact surface, the contact area is very small, making it impossible to produce a high-quality image. It has been proven that inaccuracy of at least one micron leads to a complete loss of dactyloscopical information. Such reflection systems attempt to compensate for this disadvantage by coating the contact surface with special contact substances, as disclosed in European Patent Application No. 304092, published Feb. 22, 1989. Another problem is that the low mechanical resistance of contact surface coatings causes the coating to come off after contact with several fingers.
Another disadvantage of using a series of lenses is that it principally leads to a significant drop in quality because of optical distortions and aberrations introduced by the lenses. Moreover, for each additional element introduced into the process of data transfer, additional errors are introduced. The use of a series of lenses enlarges the size of the device and decreases the mechanical stability and reliability. There have been attempts to seal hermetically the gaps between the lenses and the contact surface, especially to prevent loose particles from entering the gaps.
The above-mentioned disadvantages prevent widespread use of such reflection systems, allowing only for their occasional use in instances when neither the high security of automatic identification, nor the small dimensions of the device are prohibitive.
Russian Patent No. 2031625, published Mar. 27, 1995 discloses a light penetrating system and user identity verification method. In this system, a user's finger must be placed on a fiber optical surface of camera, and then, penetrating directed at the finger. The output signal of the camera is computer processed, and thus the fingerprint is verified. When a finger comes into contact with an optical fiber, the dermal ridges fit closely with the fiber contact surface, and the light diaphaning the finger meets the contact surface and thus the photosensitive elements. The light lost and are much less at areas where the finger contact is direct, as opposed to areas where the relief structure does not allow direct contact.
The method disclosed in Russian Patent No. 2031625 generally is free from the types of disadvantages which are natural to light reflecting systems of image processing. The method disclosed by that Russian patent distinguishes over light reflecting systems by providing a better quality fingerprint image. The presentable gradations of dactyloscopical pictures depend only on the dynamic characteristics of the camera used. Additionally, the existence of gaps between the skin and a contact surface does not result in a complete loss of the information. Further, the size of this gap is proportional to the amount of penetrating light.
However, the light penetrating system also suffers from certain disadvantages. The present inventors have discovered that there are undesirable variations in the contrast of the dactyloscopical picture at the entry surface of the camera. These undesirable variations are caused by the user's pulse, which provides variations in the bloodflow that affect the amount of light passing through the finger. Such instability of the image results in false pieces of information that decrease the quality of the image and increase the error rate.
Another disadvantage of the light penetrating system is the dependency of picture quality on the availability of outside natural light. Moreover, this prior art system does not distinguish between a live finger and a previously recorded fingerprint. Thus, the prior art light penetrating system is vulnerable to breach by a counterfeit image, making the system undesirable for use in code-locks and other security or access control systems.
Russian Patent No. 2031623 discloses a user identity verification system based on a camera with a fiber optical entry surface designed for finger contact. The finger placed on the entry area is diaphaned by a source of light or daylight, e.g. a liet bulb, which is installed opposite the contact surface. The camera is connected with a signal processing module.
Unlike the first type of light penetrating system, a device utilizing a fiber optical entry surface does not have any. lenses; therefore, it is free from all of the inaccuracies affecting identification introduced by aberrations of the optical lenses. Such devices are characterized by small dimen
Grekovich Alexandr Anatolievich
Minkin Viktor Albertovich
Romanova Ludmila Pavlovna
Shtam Alexandr Iliich
Tataurschikov Sergei Sergeevich
Ahmed Samir
Bali Vikkram
Stevens Davis Miller & Mosher LLP
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