What is optical fingerprint sensor?

optical fingerprint sensor mainly uses the principle of light refraction and reflection to collect fingerprints. Put the finger on the optical lens, under the irradiation of the built-in light source, the light is shot from the bottom to the prism, and is emitted through the prism, and the Angle of refraction of the emitted light on the uneven line of the fingerprint on the finger surface and the light reflected back will be different. It is projected on CCD with prism to form a digital fingerprint image that can be processed by fingerprint algorithm. The ridge line (the grain line with a certain width and direction in the fingerprint image) is black, and the valley line (the concave part between the grain line) is white.

In simple terms, the optical fingerprint sensor is like a tiny camera: when you press your finger, it takes a picture of your fingerprint. So your fingerprints are taken and then passed on to the back-end processor for processing.

Technically, when you put your finger on it, the light emitted by the collecting head will be blocked by your finger. Because there are ridges (raised parts) and valleys (concave parts) on the fingerprint, the light will have different reflection principles after encountering them, resulting in the return of light and dark. The reflected light is refracted through the prism and hit the sensor to create an image.

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advantage

Advantage 1: Strong environmental adaptability and easy to clean up

The optical fingerprint sensor module has strong adaptability to the environment. The acquisition window is generally made of tempered glass, which can enhance the resistance to pressure, wear, acid and stain corrosion to a certain extent. It has good adaptability to the temperature of the working environment, and the surface is easy to clean. Special environment of high temperature and dust.

Advantage 2: Long life span

The optical fingerprint module has good stability, the optical fingerprint recognition technology has been tested and improved for a long time in the market, and the optical fingerprint scanner has a good adaptability to the market environment, and the theoretical life is long.

Advantage 3: Low cost

optical fingerprint sensor module has a low cost, optical fingerprint scanner developed earlier, has a mature industry scale, and can be modular mass production, and the raw materials used by optical fingerprint module are relatively cheap. Therefore, the cost of optical fingerprint head is generally cheaper than semiconductor fingerprint head.

shortcoming

Disadvantage 1: Lack of accuracy

There are some inherent defects in the identification accuracy of optical fingerprint scanner. The optical fingerprint module is the imaging of the fingerprint ridges and valleys reflecting different light. Users with shallow fingerprints, too dry fingerprints or peeling fingerprints are prone to misidentification.

Disadvantage 2: Large size

Compared with the capacitive fingerprint sensor, the optical fingerprint sensor module is larger.

Disadvantage 3: High power consumption

Because the optical fingerprint sensor needs to emit very strong light during verification, it consumes a lot of power.

The advantages of the optical fingerprint sensor module are mainly strong anti-static ability, good system stability, long service life, particularly high sensitivity, and can provide high-resolution fingerprint images, and the technology is also the most mature. Therefore, many companies are now widely used, mainly for fingerprint door locks, safe deposit boxes, car fingerprint anti-theft.

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