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The fingerprint identification instrument is a special instrument for identification through the biometric fingerprint of the human body. Fingerprints are unique and immutable for life, so it is very safe and convenient to use as one of the ways of identification. Fingerprint identification devices are widely used in identity verification occasions such as banking, social security, public security, time and attendance, access control, computer and network security, and Internet shopping payment methods.
The Chinese name fingerprint identification device is used for identity recognition. Advantages are safe and convenient. Principles of identification through human biometric fingerprints. Applications Banking, social security, public security, attendance, and access control.
The fingerprint identification device is a sensor (area type) based on the principle of living body acquisition and identification. It is an online or offline product composed of software and hardware such as high-performance fingerprint comparison algorithms. The work of the hardware part is to collect fingerprints and transfer them to the In the host, the identification and comparison tasks are completed by the fingerprint recognition software installed in the host. The product adopts the world’s most advanced living leather fingerprint collection technology, which prevents fake fingerprints, has a high recognition rate, is compact, durable, and is cost-effective.
The fingerprint identification instrument is a special instrument for identification through the biometric fingerprint of the human body. There are four main types of fingerprint image acquisition technologies: optical scanning equipment (such as a micro-prism matrix), temperature-sensitive fingerprint sensor, semiconductor fingerprint sensor, and ultrasonic fingerprint scanning.
Using optical technology to collect fingerprints is the oldest and most widely used technology. Place your finger on the optical lens, and use a prism to project your finger on the charge coupled device (CCD) under the illumination of the built-in light source to form ridges (the lines with a certain width and direction in the fingerprint image), which are black and valleys. The line (the concave part between the lines) is a white digitized multi-gray fingerprint image that can be processed by the fingerprint device algorithm.
Optical fingerprint collection technology has obvious advantages: it has been tested for a long time, adapts to temperature variation to a certain extent, can reach a higher resolution of 500DPI, etc., the most important is its low price. There are also obvious shortcomings: due to the requirement of a sufficiently long optical path, a sufficiently large size is required, and overly dry and overly greasy fingers will also deteriorate the effect of optical fingerprint products.
The limitations of optical fingerprint sensing are reflected in potential fingerprints (potential fingerprints are left after the finger is pressed on the platen), which will not only reduce the quality of the fingerprint image, but may also cause the overlap of the two fingerprints in severe cases. Obviously, it is difficult to satisfy Actual application needs. In addition, the coating of the platen and the CCD array will wear out over time, which may cause the quality of the collected fingerprint images to decrease. However, it has disadvantages such as inability to perform live fingerprint identification and poor applicability to wet and dry fingers.
Since the optical fingerprint recognition system cannot penetrate the skin surface (dead skin layer), the optical fingerprint recognition system can only scan the surface of the finger skin, or scan the dead skin layer, but cannot penetrate deep into the dermis. In this case, the cleanliness of the finger surface directly affects the recognition effect. If a lot of dust is stuck on the user’s finger, there may be an error in recognition. Moreover, if people make a fingerprint hand model according to their fingers, it may also pass through the identification system, which is not very safe and stable for users to use.
The temperature difference sensing recognition technology is made based on the principle of temperature sensing. Each pixel is equivalent to a miniaturized charge sensor, which is used to sense the temperature difference between the finger and the image area of the chip to generate a representative image information. Electrical signal.
Its advantage is that the fingerprint image can be obtained within 0.1s, and the sensor has the smallest volume and area, that is, the currently commonly referred to as sliding fingerprint identification device adopts this technology. The disadvantage is: subject to temperature limitations, the finger and chip will be at the same temperature after a long time.
In the late 1990s, the technology based on the semiconductor silicon capacitor effect became mature. The silicon sensor becomes one plate of the capacitor, and the finger is the other plate. The capacitance difference between the ridge and valley of the fingerprint line of the hand and the smooth silicon sensor is used to form an 8-bit grayscale image. The capacitive sensor sends out an electronic signal, which will pass through the surface of the finger and the dead skin layer, and reach the living body layer (dermis layer) of the finger’s skin, directly reading the fingerprint pattern. As it goes deep into the dermis, the sensor can capture more real data, is less susceptible to the influence of dust on the surface of the finger, improves the recognition accuracy, and effectively prevents recognition errors.
Semiconductor fingerprint sensors include semiconductor pressure-sensitive sensors, semiconductor temperature-sensing sensors, etc. Among them, semiconductor capacitive fingerprint sensors are the most widely used.
The semiconductor capacitance sensor judges which position is the ridge and which position is the ridge according to the difference between the ridge and ridge of the fingerprint and the capacitance formed by the semiconductor capacitive sensing particles. Its working process is to pre-charge the capacitive sensing particles on each pixel to a certain reference voltage. When the finger touches the fingerprint performance of the semiconductor capacitor, because the ridge is convex and the ridge is concave, according to the relationship between the capacitance value and the distance, different capacitance values will be formed at the ridge and the ridge. Then use the discharge current to discharge. Because the ridge and yu have different capacitance values, their discharge speeds are also different. The pixels under the crest (high capacitance) discharge more slowly, and the pixels under the ridge (low capacitance) discharge faster. Depending on the discharge rate, the positions of the ridges and ridges can be detected to form fingerprint image data.
Unlike optical equipment that uses manual adjustment to improve image quality, capacitive sensors use automatic control technology to adjust fingerprint image pixels and the sensitivity of fingerprint local areas, and combine feedback information to generate high-quality images in different environments. Due to the local adjustment capability, even images with poor contrast (such as areas where the fingers are lightly pressed) can be effectively detected, and the sensitivity of these pixels can be increased at the moment of capture to generate high-quality fingerprint images.
The semiconductor capacitive fingerprint sensor has the advantages of good image quality, generally no distortion, small size, and easy integration into various devices. The electronic signal sent out will pass through the surface of the finger and the dead skin layer to reach the living body layer (dermis layer) of the finger skin, and directly read the fingerprint pattern, thereby greatly improving the security of the system.
The most important advantage of semiconductor silicon sensing technology is that it can achieve live fingerprint recognition. It can also obtain better image quality than optical technology on a smaller surface, and a resolution of 200-300 lines can be obtained on a 25px×37.5px surface (the smaller surface also leads to a reduction in cost and can be integrated into more In a small device). Small size, low cost, high imaging accuracy, and low power consumption, so it is very suitable for use in security and high-end consumer electronic products, known as the second generation of fingerprint recognition technology after optics.
Ultrasonic fingerprint collection is a new type of technology. Its principle is to use the ability of ultrasonic waves to penetrate materials, and generate echoes of different sizes depending on the material (when ultrasonic waves reach the surface of different materials, the degree of absorption, penetration and reflection is different ). Therefore, by using the difference in acoustic impedance between the skin and the air, the location of the fingerprint ridge and ridge can be distinguished.
The ultrasonic frequency used by the ultrasonic technology is 1×104Hz-1×109Hz, and the energy is controlled to the extent that it does not damage the human body (the same intensity as the medical diagnosis). Ultrasonic technology products can achieve the best accuracy. It has low requirements for the cleanliness of fingers and surfaces, but its collection time will be significantly longer than the aforementioned two types of products, and it is expensive, and it cannot achieve live fingerprint recognition. Used sparsely.
Because of its maturity and cost reduction, fingerprint recognition has begun to be used for civilian purposes. Domestic biometrics will form a market worth tens of billions in the future, of which the security industry is one of the most important application fields, and the market space is huge. At present, the Luohu port has already used fingerprints for customs clearance. Will Germany apply fingerprint recognition to certain supermarkets? It is expected that fingerprint access control, fingerprint readers, fingerprint smart locks, fingerprint access control and attendance machines and related fingerprint identification systems will quickly spread to every security project and smart building. At present, the number of domestic access control installations is about 500,000 doors per year. Above, fingerprint recognition is only about 1% in access control applications, and generally the proportion in foreign countries should be about 20% or more. In other words, in the domestic security industry, the market gap of biometric products is about 95,000 units. Another obvious situation is that there are currently few companies specializing in the production and sales of fingerprint readers and fingerprint access control, so look at this in general. The market has two obvious characteristics: a large market and less competition.
Widely used in: identity authentication occasions such as banking, social security, public security, time and attendance, access control, computer and network security, and Internet shopping payment methods.
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