Consumer Electronics

Ultrasonic sensors often play the role of an "environmental perception hub." Their non-contact, low-power, and anti-interference characteristics make them an essential complement to optical and infrared technologies. With advancements in miniaturization and algorithms, ultrasonic sensors are expected to integrate more deeply into smart homes, health wearables, and interactive entertainment, driving consumer electronics and intelligent industries towards "invisible intelligence."

Core Principle: Emission and Reception of Ultrasonic Waves

Ultrasonic sensors work based on the piezoelectric effect and primarily consist of an emitter and a receiver:

1. Emitter: A piezoelectric crystal (such as ceramics) is excited by an electrical signal to generate high-frequency vibrations (usually between 20 kHz and 40 kHz) that emit ultrasonic pulses.

2. Receiver: Captures the reflected echo from an object. By calculating the time or phase difference between emission and reception, and combining it with the sound speed (approximately 340 m/s, affected by temperature), the distance to the target is computed:
   <math xmlns="http://www.w3.org/1998/Math/MathML">Distance(d)=v×Δt2\text{Distance} (d) = \frac{v \times \Delta t}{2}</math>.

3. Derived Technologies:

   • Doppler Effect: Detects the speed of moving objects (e.g., respiratory or heart rate monitoring).

   • Beamforming: Uses a multi-probe array to achieve directional emission of ultrasonic waves, improving detection accuracy (e.g., obstacle avoidance in robotic vacuums).

Typical Applications in Consumer Electronics

1. Smartphones and Mobile Devices
   Technological Advantages:

   • Ultrasonic fingerprint recognition can penetrate thick glass (above 0.8mm), working better in wet or dirty conditions, making it more reliable than optical fingerprint sensors.

   • Air gestures require no camera, ensuring stronger privacy and functionality in low-light conditions.

2. Smart Homes and IoT
   Technical Challenges:

   • Ultrasonic interference can occur when multiple devices operate simultaneously (e.g., multiple robotic vacuums in one room). This can be mitigated using frequency hopping technology or pulse encoding.

3. Wearables and Health Monitoring
   Emerging Applications:

   • Ultrasonic Communication (USS): Transmits data through ultrasonic pulses (e.g., 0.1-1 meter for short-range pairing). It is resistant to electromagnetic interference, making it suitable for hospitals or sensitive areas.

   • Example: Some smart locks use ultrasonic signals to unlock when a phone is nearby.

4. AR/VR Interaction
   Principle: Ultrasonic sensors in headsets track hand positions to enable virtual control without the need for physical controllers (e.g., for grabbing virtual objects).
   Challenges: Must be integrated with visual sensors (like cameras) to resolve issues with "line-of-sight" blocking (since sound can bypass obstacles, but light cannot).

5. Airborne Ultrasonics
   Principle: Directional ultrasonic beams create a "sound channel" in the air, allowing only specific individuals to hear the sound (e.g., smart speakers directing sound to particular listeners).
   Example: Sony’s “ultrasonic focusing” technology used in TVs for directed sound fields.

Technical Advantages and Challenges

Advantages:

1. Strong Environmental Adaptability:

   • Unaffected by light, color, or smoke; works in dark, underwater, or dusty environments (e.g., gesture control in bathrooms).

2. Low Power Consumption and Miniaturization:

   • Single emissions consume only milliwatts of power, suitable for battery-powered devices. Sensors can be miniaturized to 5mm×5mm (e.g., micro probes in phones).

3. Cost-Effectiveness:

   • The mass production cost of piezoelectric sensors is low, making them ideal for large-scale integration into consumer products.

Future Trends

1. Deep Integration with AI:

   • Example: Neural networks optimize ultrasonic echo signal processing to enhance detection accuracy in complex environments (e.g., distinguishing pets from furniture).

2. Multi-Function Integration:

   • Single sensors will simultaneously perform distance measurement, gesture recognition, and respiratory monitoring (e.g., multi-mode ultrasonic chips integrated into smartphone front modules).

3. Green and Energy-Efficient Design:

   • Development of self-powered ultrasonic sensors (e.g., using piezoelectric energy harvesting) to reduce standby power consumption in devices.