What is the recognition technology of the fingerprint?
Everybody line of skin including fingerprint is in the pattern, break some and intersect to to have nothing in common with each other, it is only and not changing all one’s life to appear. In view of the above, we can corresponding to stand up one with fingerprint of him, through compare fingerprint and fingerprint data that keep in advance of him, can verify its true identity, this is recognition technology of fingerprint.
Information such as the line of the human fingerprint of main foundation of fingerprint recognition, detail characteristic or appraised the identity to operation by the operator, benefit from the integrated manufacturing technology of modern electron and fast and reliable algorithm and study, begin daily life to enter into us already, become living beings measure learn, studying and deepening most at present, it is most extensive to employ, develop the ripest technology.
Fingerprint recognition algorithm
With dealing with the difference artificially, the general biological recognition technology company does not store the picture of fingerprint directly, but use different digitized algorithms to find and combine on the fingerprint picture than the characteristic to fingerprint. Each fingerprint have several unique, characteristic that can measure order, each characteristic have about 5 characteristics to order, ten fingers of ours produce the characteristic that 4900 pieces of independence can be measured at least, this is enough to state fingerprint recognition to be a more reliable differentiation way.
Discern fingerprint is mainly launched from two respects: Population characteristic and some characteristic.
Population characteristic
The population characteristic refers to those with characteristic that human eye can be observed directly. Including the line shape, mode district, some of core, some of trigonometry and line count etc..
Line shape: The fingerprint expert generally divides fingerprint into three big classes according to the trend of the line of spine and distribution situation on the basis of practising for a long time – -Ring type (loop, is also called the shape of fighting) , bow-shaped (arch) , the volution (whorl) .
Mode district: I.e. including population characteristic area at the fingerprint, area can say fingerprint which type does it belong to from then on. Some fingerprint recognition algorithms only use the data of district of the mode, some use the intact fingerprint made.
The core is clicked: Lie in fingerprint line advance gradually in the centre, it is reading fingerprint and as consulting ordering at being than to fingerprint. A lot of algorithms are based on the core and clicked, can only deal with and discern that has cores fingerprint lighted.
The trigonometry is clicked: Lie in first branching since the core is clicked order or not broken a bit, either two stripe way assemble place, isolate a bit, roll over, transfer place to, or it is a bit stranger to point to these. Some trigonometries are offered the place that count beginning that is followed of a line of fingerprint.
The line is counted: I.e. the quantity of the line of fingerprint in district of mode. While calculating the line of fingerprint, generally connect key some and trigonometry to click first, the quantity of this line and fingerprint with crossing line can think it is a line of the fingerprint that is counted.
Some characteristic
Some characteristic refers to the nodal characteristic on fingerprint, these nodes with a certain characteristic are called the detail characteristics or characteristic to click. Two pieces of fingerprint will often have the same population characteristics, but their detail characteristic, but can not be all the same. The line of fingerprint is not continuous, smooth and straight, but often present cutting off, branching or transferring. These break some, some of branching and turning point on calling ” The characteristic is clicked ” ,Some of the characteristics are offered the affirmation information of only fingerprint, among them the most typical one terminates some to click with branching, include difference order, isolate some, ring ordering, short line,etc. still while being other. The parameter that the characteristic is lighted includes: Direction ( The node can be in certain direction) , camber ( Describe the line side to pace changing) , the position (describe by x/y coordinate in the nodal position, can be absolute, can click some of trigonometry or characteristic too) .
Gather the technology of the fingerprint picture
It is a very complicated problem to obtain the good fingerprint picture. Because fingerprint measured to use for quite young one epidermis only, so fingerprint gather apparatus should have fine resolution ratio enough in order to detail to win fingerprint. Fingerprint pictures used gather the apparatus at present, basically on the basis of three kinds of technological foundations: Optical technology, semiconductor silicon technology, ultrasonic technology.
Optical technology
It is the most remote, most popular technology of history to gather fingerprint through optical technology. Put the finger on the optical lens, the finger throws it in the coupling device of electric charge (CCD) with the prism under the circumstances that the built-in light source shines Go, and then form the line of spine (the line of line with certain width and trend in fingerprint picture) Black, valley line ( Sunken part between the lines of line) White digitization, many grey levels fingerprint picture that can be dealt with by the apparatus algorithm of fingerprint.
Gathering the apparatus in optical fingerprint has obvious advantages: It has already passed more long-time application to test, has met the variation of temperature to a certain extent, cheap, can achieve 500DPI high-resolution wait relatively comparatively. The shortcoming is: Because of requiring enough long optical distance, require the enough large size, and the too dry and too greasy finger will make the result of the optical fingerprint products bad.
Silicon technology (CMOS technology)
On later stage of 1990s, the technology based on effect of electric capacity of semiconductor silicon became more and more ripe. The silicon transducer becomes a polar plate of the electric capacity, the finger is another polar plate, it is bad to utilize spine and valley which point the line of line to the electric capacity between the smooth silicon transducers, form the grey level picture of 8bit.
The technological advantage of silicon can obtain picture quality better than optical technology on smaller surface, obtains resolution ratio (lower surface of Line 20000 decline causing the cost on the surface of 1cm * 1.5cm too and can be integrated in smaller apparatus) . The shortcoming is easy to be interfered with, the relative difference of dependability.
Ultrasonic technology
In order to overcome the optical technical equipment and deficiency of the silicon technical equipment, gather the apparatus to already present in a new kind of ultrasonic fingerprint. Its principle is to utilize supersonic wave to have ability to penetrate material, and is up to the return waves echo (on supersonic wave reaches surface of different materials of different production of the material of different size, it is different from intensity reflected that absorbed, penetrated) ,So utilize skin and air to acoustic difference of impedance, can distinguish fingerprint spine and position that valley locate.
The ultrasonic frequency that ultrasonic technology uses exceeds 1* 109Hz for 1* 104Hz, it is (the same as intensity of medical diagnosis) that energy is controlled the intensity that can’t harm to the human body . The technological products of supersonic wave can reach the best precision, it requires the clean intensity of finger and level relatively low, but it will be longer than two kinds of aforesaid products to gather time obviously.
The characteristic is picked up, proved and distinguished
After a high-quality picture is picked up, need a lot of steps to transform its characteristic into a template compounding, this course, known as the characteristic to pick up the course, it is a core of pointing scanning. After a high-quality picture is picked up, it must be changed into a useful form. If the picture is a grey level picture, relatively shallower part will be deleted, and relatively deeper part has been turned into deceiving. Picture of spine have 5 contract detailed to get one picture element, can accurate to orient spine to be a bit more disconnectedly diverging in this way. The picture of the small detail comes from this picture dealt with. In this regard, even very meticulous picture have details out of shape and wrong details, these out of shape straining by wrong detail except that.
Except that localization and contained angle application of method of detail, can also divide the detail through type and quality of detail. The advantage of this method lies in the pace searched has greater improvement, one a prominent one, particular detail, it getting only and easy to make it succeed in not to match. Method which some manufacturers adopt is that the mode match the method, handle the fingerprint picture through inferring the data of a group of particular spines.
In respect to employing the method, the recognition technology of fingerprint can be divided into proving and distinguished.
Verification carries on than the course of the identity to confirming more one-to-one through fingerprint and a fingerprint that has already registered of gathering one live. Fingerprint is stored with certain compression form, and with their names or its identification(ID, PIN) Connected. Comparing with the scene subsequently, verify its identification first, then utilize systematic fingerprint to compared with fingerprint gathered live prove its identification is legal in coming. Prove that has actually answered such a question: ” Is he this person that he calls oneself? ” This employs the method that is used in the system more.
It is to compare the fingerprint in fingerprint and fingerprint database gathered to distinguish live with one by one, find out the fingerprint of matching on-the-spot fingerprint from it. This lets too ” More than one pair of match ” . It is to answer such a question to distinguish: ” Who is he? ”
Fingerprint is human body’s unique characteristic, its complexity is enough to offer the characteristic used for distinguishing. It is gradual and ripe with supporting technology relevantly, the recognition technology of fingerprint has already become most convenient at present, reliable, not encroaching on and biological recognition technology solution of cheap price through the development for many years, there is very great development potentiality in the application of markets.
The recognition technology of fingerprint mainly involves four functions: Read fingerprint picture, draw characteristic, keep data and than right. At the beginning of, read the picture that the apparatus read to human fingerprint through fingerprint, fetch after the fingerprint picture, should carry on preliminary treatment to the primitive picture, make it clearer. And then, it is expressed that fingerprint distinguishes the figure set up fingerprint of the software – -Characteristic data, kinds of folk prescription to conversion,can from changing fingerprint but characteristic data can last fingerprint from characteristic data, two pieces of different fingerprint will not produce the same characteristic data. Some algorithms make the node and direction information up to produce more data, information of these directions shows the relation between each node, still deal with the whole fingerprint picture in some algorithms. In a word, these data, are usually called the template, keep it for 1K size record. No matter how they make up, still the standard of no template so far, the abstract algorithm of no announcement too, but each manufacturer goes one’s own way. Finally, through the fuzzy method to compare of the computer, compare the template of two pieces of fingerprint, calculate their similar intensity, get the match results of two pieces of fingerprint finally.
Our palm and protruding concave indignant line that produce of skin on the finger, foot, surface of toe inboard will form various pattern. The existence of these lines has increased the frictional force on the surface of skin, enable us to pick up the heavy object with hand. People notice too, the line of the skin including fingerprint is in the pattern, break some and intersect to to have nothing in common with each other, that is to say, it is the only one. Depend on the uniqueness, we can getting corresponding man and his fingerprint, compare through the fingerprint that is kept to his fingerprint and in advance, can verify his true identity. This kind of technology of relying on body characteristic of the human body to verify the identity is called biological recognition technology, fingerprint recognition is one kind of the biological recognition technology. At present, from the practical viewpoint, the recognition technology of fingerprint is the identity differentiation method which is superior to other biological recognition technology. This is because the characteristic that fingerprint had nothing in common with each other, not basically changed all one’s life has already been generally acknowledged, have laid the good technological foundation for security personnel’s fingerprint automation recognition by research and practice of the automatic recognition system of fingerprint in the warnings of nearly twenty or thirty years. Especially the reliable, stage of moderate price that easy to operate, accurate that the existing fingerprint automatic recognition system has already reached, it is the practical living beings that determine the method.
Fingerprint refers to the protruding concave not smooth line that produces on the skin of terminal front of finger. The existence of these lines has increased the frictional force on the surface of skin, enable us to pick up the heavy object with hand. Though fingerprint is only a small part of the human skin, however, it contains a large amount of information. Line of skin the in pattern, break some and intersect be had nothing in common with each other, call them in information processing ” The characteristic ” ,Each finger of these characteristics is different. Depend on characteristic getting only, we can getting corresponding man and his fingerprint, through comparing his fingerprint characteristic and fingerprint characteristic kept in advance, can verify his true identity.
The automatic recognition system of fingerprint passes special photoelectric conversion equipment and computer picture treatment technology, gather, analyze to the fingerprint of living subject and than correctly, can distinguish the personal identity automatically, fast, accurate. What the system generally mainly includes to fingerprint picture gathering, fingerprint pattern process, characteristic drawing, characteristic value, than to with the course of matching etc.. The integrated manufacturing technology of modern electron makes the fingerprint picture read and deal with the apparatus to miniaturize, the operation pace of personal computer developed at full speed at the same time has offered and can carry on fingerprint on the computer even one-chip computer than the possibility to operation, and outstanding fingerprint is dealt with and guarantee to discern the accuracy of the result than to the algorithm.
In the computer system, fingerprint recognition can be used for starting the machine the log-in identity is confirmed, the visit authority of the long-range network data base and affirmation of identity, bank savings defend the encryption method that falsely claim as one’s own and deposit and withdraw at any branch bank, the insured’s identity is confirmed in insurance trade, the identity of the securities withdrawer of the futures is confirmed, the identity of treating the insurer of systematic Chinese medicine of health care is confirmed etc.. Record, at special card of use, pass fingerprint information scene than right, can prevent the fraud of pretending to be etc.. For example: Credit card, medical card, meeting card, deposit card, driving license, admission card for entrance examination, passport anti-counterfeit,etc..
The automatic recognition technology of the computer fingerprint is entering into our actual life from the science fiction and Hollywood film, perhaps one day, you needn’t hand-carry that bunch of keys, only need the finger to press, the door will be opened; Needn’t remember annoying password that either, can utilize fingerprint withdraw deposit, computer log-in. Believe for this day, will not be too far.
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