Ultrasonic fingerprint sensors:
Ultrasonic fingerprint sensors are a type of biometric authentication technology commonly used in smartphones and other devices for securely identifying users. Unlike traditional capacitive fingerprint sensors, which rely on electrical conductivity, ultrasonic sensors use sound waves to create a 3D map of the user’s fingerprint.
Here’s a detailed explanation of how they work:
- Transmitter and Receiver Array: The ultrasonic sensor consists of a small array of ultrasonic transmitters and receivers, typically embedded beneath the display glass or within a designated area on the device.
- Ultrasonic Pulse Generation: When the user places their finger on the designated area of the screen, the sensor emits a series of ultrasonic pulses. These pulses are usually in the range of 20 to 40 kHz, which is beyond the range of human hearing.
- Reflection and Refraction: The ultrasonic pulses propagate through the glass or surface of the display. When they encounter the ridges, valleys, and pores of the user’s fingerprint, they undergo reflection and refraction.
- Time-of-Flight Measurement: The sensor measures the time it takes for the ultrasonic waves to travel from the transmitter to the fingerprint’s surface and back to the receiver. This time-of-flight measurement is incredibly precise, often in the range of nanoseconds.
- Creating a 3D Image: Based on the time-of-flight data collected from multiple points on the fingerprint’s surface, the sensor constructs a detailed 3D map of the fingerprint. This map includes information about the unique features, such as ridge patterns and minutiae points.
- Authentication: The captured fingerprint data is compared to the stored fingerprint template. If the match is within an acceptable threshold, the device grants access to the user.
- Secure Processing: To enhance security, the device typically processes the fingerprint data within a secure enclave or dedicated hardware module, safeguarding it from unauthorized access.
Advantages:
Mobile ultrasonic fingerprint sensors offer several advantages over other types of fingerprint sensors commonly used in smartphones and other mobile devices:
- Accuracy: Ultrasonic sensors can capture highly detailed 3D images of fingerprints, leading to more accurate and reliable authentication compared to other types of sensors.
- Resistance to Spoofing: Ultrasonic sensors are less susceptible to spoofing attempts using fake fingerprints made from materials like silicone or latex. Their ability to capture the unique 3D characteristics of a fingerprint makes them more secure against spoofing.
- Consistency: They can perform reliably in various environmental conditions, including when the user’s fingers are wet, dirty, or have minor cuts or abrasions. This consistency ensures reliable performance in real-world usage scenarios.
- Design Flexibility: Integrating ultrasonic sensors into the display allows for more flexibility in device design. Manufacturers can create sleeker and more seamless designs without the need for a dedicated fingerprint sensor button or separate sensor hardware on the device’s surface.
- User Experience: The integration of the fingerprint sensor into the display enhances the user experience by providing a seamless and intuitive unlocking mechanism. Users can conveniently unlock their devices by simply placing their finger on the designated area of the screen.
- Privacy: Ultrasonic sensors provide an additional layer of privacy since they typically process the fingerprint data locally on the device and encrypt it before storing or transmitting it.This helps protect users’ biometric information from unauthorized access or interception.
- Fast and Secure: Ultrasonic fingerprint sensors offer fast and secure authentication, allowing users to unlock their devices quickly while maintaining a high level of security. The detailed 3D mapping of fingerprints enables precise and reliable authentication with minimal false rejection rates.
Overall, mobile ultrasonic fingerprint sensors provide a combination of accuracy, security, convenience, and design flexibility, making them a preferred biometric authentication solution for smartphones and other mobile devices.