How to conduct research on fingerprint recognition algorithms? 5

1) Optical fingerprint recognition technology.

Optical technology, as the name suggests, is definitely related to light. The principle of this is the following diagram.

Popular Science: What is the principle of fingerprint recognition?

To put it simply, after the finger is pressed on the fingerprint collector, the internal light source hits the light on the finger, and after the finger is reflected, it is gathered on the recognizer to obtain a fingerprint image.

2) Ultrasonic technology.

Ultrasonic under-screen fingerprint recognition is to set up an ultrasonic sensor at the bottom of the screen to complete the fingerprint recognition work through ultrasound, the schematic diagram is as follows.

In 1684, the English plant morphologist Grew published the first scientific study of fingerprints**.

In 1809, Bewick trademarked his fingerprint.

In 1823, the anatomist Purkije divided fingerprints into nine categories.

In 1880, Faulds advocated the use of fingerprints in the journal Nature to identify criminals.

In 1891, Galton proposed the famous Galton classification system. Subsequently, police departments in the United Kingdom, the United States, and Germany successively adopted fingerprint identification as the main method of identification. With the development of computer and information technology, the FBI and the Paris Police Department began to research and develop the Automatic Fingerprint Identification System (AFIS) for criminal investigation in the sixties.

Automatic fingerprint identification system.

In the 90s of the 20th century, automatic fingerprint identification systems for personal identification were developed and applied.

1. Iodine vapor method: smoked with iodine vapor, because iodine can dissolve in the grease on the fingerprint print, and the fingerprint can be displayed. This method can detect:

Fingerprints from months ago.

2. Silver nitrate solution method: spray silver nitrate solution to the fingerprint, and the sodium chloride on the fingerprint will be converted into silver chloride insoluble. After the light.

Irradiation, silver chloride decomposes into silver particles, which will show brownish-black fingerprints like a photo studio film, which is a common method in criminal investigation. This method.

Fingerprints older than longer can be detected.

3. Organic chromogenic method: because fingerprint contains a variety of amino acids, a reagent called dihydropolytrione is used, and it is used with amino groups.

The acid reaction produces a purple substance, which can detect fingerprints. This method can be checked out.

Fingerprints from a year or two ago.

4. Laser detection method: the fingerprint is irradiated with a laser to show the fingerprint. This method can detect fingerprints up to five years old.

This is a comparison with a fingerprint graph, using various computer algorithms.

Common fingerprints are central pouch-shaped, radial ring-shaped, long ring-shaped, tent-shaped arch, and arbitrary rows.

The method of detecting fingerprints can first be high-tech, and then you can also use adhesive tape to glue your thumb, and then you can see a fingerprint.

If I want to observe this, you know the strongest one.

Powder manifestation method. Choose metal or non-metallic powders that contrast with the color of the surface of the object, and use the characteristics of fingerprints with low adhesion to turn colorless fingerprints into colored fingerprints with layers.

Silver nitrate method. More than 98% of the substances in sweat are water, which is a variety of organic or inorganic substances, including sodium chloride. Silver nitrate reacts with sodium chloride and decomposes silver ions after being exposed to light, thus revealing gray-black fingerprints.

Laser irradiation method. The use of laser irradiation on the surface of the substance can make the trace substances in the colorless fingerprint fluoresce, and it has a good effect on the colorless fingerprint on paper, glass, wood, plastic, textiles and metal receptors.

Photographic extraction. This is one of the commonly used methods, one is not to damage the fingerprint and its receptors, and the other is to objectively and truly reflect the relationship between the fingerprint receptor and the surrounding environment and other objects. Take a single fingerprint with the size of the original fingerprint.