Acquisition and Recognition of Fingerprint Image in Fingerprint Scanner

In the Fingerprint Scanner, the fingerprint image collected by the fingerprint sensor is divided into offline scanning and live scanning. For example, fingerprints are collected at crime scenes, fingerprints are collected on paper, and fingerprints are collected on online sensors. In recent years, many technological innovations have been made in the sensors used in live scanning, and the main sensors are optical sensors, solid-state sensors and ultrasonic sensors.

(1) The optical sensor uses the principle of total reflection of light Rm, the light irradiates the glass surface with the fingerprint pressed, and the ccd obtains the reflected light to draw the fingerprint image. The amount of reflected light depends on the depth of the fingerprint ridges and grains on the glass surface and the skin and glass. The oil in between, the optical sensor is a common sensor for fingerprint acquisition, the optical sensor has good image quality, low cost, and durability. The disadvantage is that the acquisition device is bulky, and the image quality is easily affected by wet fingers.
(2) The solid-state sensor 58 uses a microcrystal array to draw fingerprint images through various techniques, the most common solid-state sensor is a silicon capacitor sensor, whose surface is an array of capacitors, and when the finger is placed on it, the skin forms another pole of the capacitor array. , the power of the capacitor changes with the distance of the sensor surface, another solid-state sensor is a pressure sensor, the surface of which is an elastic pressure sensor dielectric material, and they are converted into corresponding electrical signals according to the changes in the surface of the fingerprint, the third solid-state sensor It is a temperature sensor, the fingerprint image passes through the ridges on the device and the temperature away from the device, the solid-state sensor is small in size and low in power consumption, but is susceptible to static electricity, is easily damaged, and costs more than optical sensors.
(3) The ultrasonic sensor scans the fingerprint surface with ultrasonic waves, obtains the reflected signal, and draws the fingerprint image according to the reflected signal. Ultrasonic sensors are not sensitive to dirt and oils that accumulate on the skin. The images collected are of good quality, but at a high cost.