Basic principle of fingerprint recognition

Fingerprint, because it has no changing the sex, uniqueness and convenience all the life, has already nearly become the pronoun that the biological characteristic discerned. Fingerprint refers to people’s protruding concave indignant line line that produces on the skin of terminal front of finger. The permutation of the line with regular line forms different line types. Line starting point, terminal point, combine some of line and branching order, detail characteristic some (minutiae) to call fingerprint . Fingerprint recognition mean until different detail characteristic of fingerprint order, distinguish promptly. Because fingerprint of everybody different, even if the same ten of people mean, fingerprint has obvious differences too, so fingerprint can be used in the identity to appraise. In fact, our country has utilized fingerprint (the impression of the hand) for a long time in ancient times Come to sign. In 1684, the plant morphological family Grew issued the first scientific thesis of research fingerprint. Bewick regarded one’s own fingerprint as the trade mark in 1809. Anatomist Purkije divided fingerprint into nine kinds in 1823. In 1880, Faulds recommended using fingerprint for discerning criminals in Nature. Galton put forward famous Galton’s categorised system in 1891. Later, the department of police of Britain, U.S.A., Germany,etc. successively adopted the main method that the differentiation law of fingerprint was appraised as the identity. With the development of the computer and information technology, FBI and police office of Paris, France began to research and develop the automatic recognition system of fingerprint (AFIS) in the sixties Used in the criminal case to track down. At present, the police offices from all parts of the world have already adopted the automatic recognition system of fingerprint extensively. In the 1990s, were used in the automatic fingerprint recognition system that the personal identity was appraised and receive development and application.

Because the position where the right-falling stroke tallies is not totally the same each time, impetuses are different will bring the deformation in various degree, a large amount of fuzzy fingerprint exists again, how to draw the characteristic and realize correctly that matches correctly, it is a key to the recognition technology of the fingerprint. Fingerprint recognition technology involve pattern process, pattern-recognition, machine study, computer vision, mathematics morphology, light wave person who analyze numerous disciplines.

The recognition system of fingerprint is a typical mode recognition system, including the fingerprint picture is obtained, dealt with, the characteristic is drawn and than the reciprocal module.

The fingerprint picture is obtained: Gather the appearance and can gather the fingerprint picture of the living subject through special fingerprint. At present, gather the appearance mainly having a living subject optics type, electric capacity type and press the sense type in fingerprint. As to the thing that technical indicators such as resolution ratio and area of gathering,etc., the trades of public security men have already formed the international and domestic standard, but the others still lack and seek unity of standard. Can be divided into and pressed down and printed fingerprint and level to press down the fingerprint of printing rollingly on the whole according to gathering the fingerprint area, the trades of public security men generally adopt and press down the fingerprint of printing rollingly. In addition, can obtain the fingerprint picture through the scanner, digital camera,etc. too.

The fingerprint picture is compressed: The fingerprint database of the large capacity must be stored after compressing, in order to reduce the memory space. The main method includes JPEG, WSQ, EZW,etc..

The pattern process of fingerprint: Fingerprint regional detection, picture quality judge, direction picture and frequency estimate, picture strengthen, fingerprint picture two value and thinning.

Fingerprint classification: The line type is the basic classification of the fingerprint, divided according to pattern and triangular basic shape of centre. The shape subordinated toing type of the line, name with the form of the centre line. Ten fingerprint analytic approaches in our country divide fingerprint into three major types, nine kinds of shapes. General, the automatic recognition system of fingerprint divides fingerprint into the bow-shaped line (arcual line, account shape line) , dustpan appear line ‘ Left dustpan, right dustpan) , fight shape line and miscellaneous shape line,etc..

Fingerprint shape and detail characteristic are drawn: Fingerprint shape characteristic include in the center ‘ Have, leave) Until trigonometry a bit ‘ Left deviation, right) Wait, detail of fingerprint characteristic order, include line starting point, terminal point of line, combine some mainly and branching order.

Fingerprint is to right: Can follow the line shape of fingerprint to match thickly, and then utilize the fingerprint shape and detail characteristic to match accurately, provide the similar scores of two pieces of fingerprint. On the basis of the ones that employed, arrange in an order or provide the judgement result that is the same fingerprint to the similar score of fingerprint.

In the present computer employs, include a lot of very secret file protect, mostly use ” User ID + password ” Method it comes to be to carry on user identity authentication and visit it control. However, if once the password is forgotten, or is stolen by others, the security questions of computer system and file have been threatened.

With the progress of science and technology, the recognition technology of fingerprint has already begun to enter in PC World slowly. A lot of companies and research institutions have all made very great breakthrough progress in the field of recognition technology of fingerprint at present, put out a lot of fingerprint recognition and perfect application products that combined of traditional IT technology, these products have already been approved of by more and more users. Commercial field in which the recognition technology of fingerprint is used for having high expectations for security more, move, work field Fujitsu, Samsung, IBM to have much achievement international famous brand have technology and applicant comparatively ripe fingerprint recognition system in commercial affair, carry on the simple introduction to the application of fingerprint in the notebook computer of recognition system below.

As everyone knows, the identity when the note-books of some brands adopted the recognition technology of fingerprint to be used in user’s log-in two years ago is appraised, however, the fingerprint system put out at that time is an optical recognition system, according to the present statement, it should be the recognition technology of the 1st generation of fingerprint. Optical fingerprint recognition system can penetrate the top layer of skin because of the light ‘ Fatal character skin layer) ,So can only scan the surface which points the skin, or scan the fatal character skin layer, but can’t deepen the genuine leather layer.

In this case, the clean intensity with superficial finger, influence the result discerned directly. If, users glue more dusts on the finger, perhaps will discern the situation making mistakes. And, if people make a fingerprint hand mould, may pass the recognition system according to the finger, as to user, it is not very safe and steady that use.

So the second generation of electric capacity type transducer appears, the transducer technology of electric capacity is to adopt permutation and transducer electric board which replaces the order, the form of replacing the board is two electric capacities board, and mountain valley and ridge of fingerprint become non-conductor between the boards. The transducer that the constant between the two is dielectric measures and changes in next life and becomes the fingerprint picture. But because transducer surface use silicon to be material apt to damage, lead to the fact service life reduce, and it and ridge unsmooth to come to form fingerprint picture so difficult finger discerning rate low to dirty finger wet finger,etc. through mountain valley of fingerprint.

Develop until today, the fingerprint recognition technology of the third generation of biological radio frequency appears, the transducer technology of radio frequency is to transmit the micro- radio frequency signal out through transducer, which penetrates the finger epidermis layer detects the line of the inner layer, to obtain the best fingerprint picture. Do finger correctly, Chinese finger, do finger difficult finger through can be up to99@%, Anti-counterfeit fingerprint ability is strong, the discernment principle of the sensitive device of fingerprint only reacts to skin of people’s genuine leather, having stopped the question of artificial fingerprint fundamentally, the wide warm district: Suitable for very cold or very scorching area. Because the radio frequency transducer produces the high-quality picture, the technology of radio frequency is the most reliable, have a solution most effectively. In addition, the high-quality picture also allows to reduce the transducer, does not need to sacrifice the dependability of authentication, lower costs and make radio frequency transducer thought apply to, can move, receive constrained field any with size.

This entry was posted on Wednesday, December 2nd, 2009 at 3:20 pm and is filed under Fingerprint, Fingerprint Recognition. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.