Advantages and disadvantages of capacitive fingerprint scanner and optical fingerprint sensor

Advantages and disadvantages of capacitive fingerprint scanner and optical fingerprint sensor:

The fingerprint is composed of ridge line and valley line. Ridge line is the raised part of fingerprint texture, and valley line is the concave part of fingerprint texture.

The optical fingerprint sensor is the oldest and most widely used fingerprint acquisition technology, the optical fingerprint scanner was started in 1971, its principle is the total reflection of light. The light shines on the glass surface with the fingerprint, and the reflected light is obtained by the CCD. After the light is illuminated by the glass to the valley, it is fully reflected at the interface between the glass and the air, and the light is reflected to the CCD, while the light emitted to the ridge is not fully reflected, but is absorbed by the contact surface between the ridge and the glass or diffusely reflected to other places, so that a clear fingerprint image is formed on the CCD. optical fingerprint scanner has many advantages: It has experienced the test of practical application for a long time, can withstand a certain degree of temperature change, has good stability, and can provide images with a resolution of more than 500dpi, and the sensitivity of fingerprint recognition is very high. In addition, optical fingerprint senso generally adopts tempered glass. To a certain extent, the fingerprint acquisition instrument can be well protected, and the service life is very long. The temperature range of fingerprint recognition is between minus 20 degrees and 85 degrees. In view of these characteristics, it has gradually become the mainstream fingerprint acquisition technology on the market.

Two.

The principle of capacitive fingerprint scanner is: On a "plate" integrated with thousands of semiconductor devices, the finger is attached to it and forms the other side of the capacitor (inductance). Because the finger plane is uneven, the actual distance between the convex point and the concave point contacting the plate is different, and the capacitance/inductance value is not the same. The device summarizes the different values collected according to this principle. We're done collecting fingerprints. capacitive fingerprint scanner has the advantages of small size and high recognition rate. Of course, the capacitive fingerprint sensor, which has great potential and represents the future development direction, also has certain limitations. It is easily affected by static electricity. In serious cases, the sensor may not collect images and even be damaged. Finger sweat salts or other dirt, as well as finger wear and tear will cause image acquisition difficulties, surface scratch resistance is poor, its wear resistance is not as good as glass; Large area manufacturing cost is high, so the image taking area is small.

Dry fingers in winter are better than optical fingers, and with the improvement of technology, I believe that capacitive fingerprint sensor will be more widely used in the future. The disadvantage of the optical fingerprint sensor module is that the size of the optical fingerprint module is larger than that of the capacitive fingerprint module, and the dry finger recognition decreases in winter.

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