Common methods of cracking a fingerprint sensor include creating a rubber model of a finger, copying a fingerprint onto a piece of tape, or getting a real finger from a person. Recently, we have found a combination of a fingerprint sensor and a heart rate sensor in several of the latest smartphones, which is expected to avoid this type of attack.
In general, a smartphone fingerprint sensor maps a fingerprint to an on-chip capacitor matrix that is large enough to cover a finger. Next, the observed fingerprint pattern is compared to the stored pattern recorded during training by a software algorithm, taking into account some variations caused by finger placement, rotation, and pressure.
The heart rate sensor operates on a different principle, sending an LED light source through human soft tissue reflected from the bone and receiving it by a sensor located near the LED. The amount of light received depends primarily on the amount of moisture (blood) in the soft tissue. When the heart is relaxed, the venous blood is less, and when the heart contracts, it expands significantly and produces a pulse.
The combination of a capacitive fingerprint sensor and a heart rate sensor eliminates the need for separate contacts for each function, which is the approach taken by Samsung's Galaxy Note 8 and S9 phones. It also adds security to confirm the unlocking of the phone with a living finger. Goodix is ​​equipped with this type of sensor in several smartphones currently shipping.
This combined sensor is actually smaller than the size of the fingerprint sensor alone. It adds a small chip to the capacitive fingerprint sensor chip to implement a small optical sensor array with only a small increase in chip cost. The added cost of this combined sensor comes primarily from external LEDs, as well as the addition of light-transmissive windows in the package (the cost of allowing the LED source to dissipate and allow reflected light to enter.
Goodix does not recommend heart rate detection sensors because simple heart rate sensors may be less accurate, but they must be responsible for monitoring heart rate. For the sake of safety, the exact heart rate number is not important – the key is pulse.
Therefore, the main advantage of the combination of fingerprint sensor and heart rate sensor is to make fingerprint recognition more secure and reliable. Next, we expect to add another temperature sensor to this type of fingerprint sensor combination to further ensure that the fingerprints are indeed from a lively blood.
Progressive Punching is an efficient self-riveting process of fixed rotor, which can realize large-scale and precise riveting operation and is suitable for mass manufacturing production line. The following is the introduction of progressive rotor self-riveting process:
First, determine the type and specification of the stator and rotor required for riveting, and prepare the rivets and riveting machines required for riveting. Rivet size should match the hole size of stator and rotor to ensure tight fit and firmness.
According to the size and riveting requirements of stator and rotor, the rivet is machined into the corresponding length and shape. Progressive punch riveting machine also needs to adjust, set, calibrate the position of the riveting head, pressure, speed and other parameters.
Insert the rivet into the stator hole, and start the progressive punching riveting machine with electricity. The rivet will exert force on the rivet head according to the set parameters, and form a large number of threaded processes on the inner wall of the stator hole, so that the rivet deformation is firmly connected with the stator.
Wait for the rivet deformation, riveting process is complete. The remaining rivet tail should be cut off and inspected after riveting is completed to ensure that the riveting is firm and reliable and the transmission system runs smoothly.
In general, the process of progressive impact fixed rotor self-riveting can improve the production efficiency, but also ensure the precision and stability of riveting. However, riveting machine adjustment requires specialized skills, so an operator familiar with the riveting process is required.
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