Ultrasonic fingerprint sensors can detect structure beneath the skin, but that does not mean ordinary phones map your blood vessels. Qualcomm says its 3D Sonic sensors use sound to capture three-dimensional fingerprint details; vessel imaging has been demonstrated in laboratory studies, not established as a routine feature of consumer phones.
How an under-display ultrasonic fingerprint sensor works
An ultrasonic reader sends sound pulses through the display and interprets the echoes that return from the finger. Those echoes contain depth information, allowing the sensor to reconstruct three-dimensional fingerprint structure rather than relying only on an image of the surface. Qualcomm says its 3D Sonic technology scans details including pores and can operate through glass or metal, including when a finger is wet or contaminated.
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That ability to sense beneath the surface is what makes the phrase “sees beyond the skin” plausible. It describes acoustic sensing of structures in a finger; it does not, by itself, mean that a phone creates a detailed map of the user’s blood vessels.
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Do phones map blood vessels?
There is laboratory evidence that ultrasound can image a vessel beneath a fingerprint, but it should not be confused with a deployed phone feature.
#1 Best Overall
- HC-SR04 Ultrasonic Sensor：This is a device that can use sound waves to measure the distance of an object. It measures distance by emitting a sound wave of a specific frequency and listening to the bounce of that sound wave. The distance between the sonar sensor and the object can be calculated by recording the time elapsed between the generation of the sound wave and the bounce of the sound wave
- Working Voltage: 5V DC；Quiescent current: less than 2mA
- Ranging Distance：2cm - 450 cm；High precision: 0.3 cm
- Effectual Angle: <15°
- Test mode ：Test distance = ((Duration of high level)*(Sonic :340m/s))/2
What the 2021 studies demonstrated
- A 2021 IEEE Sensors Journal study reported an under-display ultrasonic fingerprint-recognition experiment that imaged a vessel below the fingerprint. The researchers used a 40 MHz PZT-5H sensor and produced 500 × 500 DPI images in a two-layer phantom. A phantom is a laboratory model, not a test proving that a consumer phone maps vessels in a living finger.
- A separate 2021 Scientific Reports study used a 15 MHz ultrasound/photoacoustic array to produce three-dimensional images of fingerprints and subdermal vessels from wet and dry fingers. The authors noted that conventional ultrasonic fingerprint sensors have limited sensitivity to subdermal vascular structures and described vessel sensing as a possible future direction for stronger liveness detection.
These results establish a research capability, not a medical feature in current mass-market phones. They do not show that a phone produces a medical-quality vessel map, measures blood sugar, or diagnoses a health condition.
Ultrasonic vs. optical fingerprint readers
| Comparison | Optical reader | Ultrasonic reader |
|---|---|---|
| What it captures | A two-dimensional image of the fingerprint surface. | Acoustic echoes used to reconstruct three-dimensional fingerprint structure. |
| Depth information | Surface image; sub-surface depth information is not established in the cited material. | Can capture depth-related structure. Qualcomm says its 3D Sonic technology scans pores. |
| Operation through a display | Not stated in the cited Qualcomm materials. | Designed to send sound through display layers; Qualcomm’s 2017 announcement reported scanning through OLED stacks up to 1,200 µm thick. |
| Wet or contaminated fingers | Performance is not stated in the cited materials. | Qualcomm says its technology can work with wet or contaminated fingers. |
| Spoof resistance and liveness | Comparative test results are not stated in the cited materials. | Depth and acoustic information may support liveness checks. Qualcomm’s claims are vendor statements, not independent comparative test results. |
| Vessel imaging | No vessel-imaging capability is established in the cited materials. | Shown in laboratory research; routine vessel mapping by a consumer phone is not established. |
The table describes the evidence available for these particular comparison points, not a claim that every optical or ultrasonic sensor behaves identically. Qualcomm’s reported 2017 material limits also included cover glass up to 800 µm and aluminum up to 650 µm; those figures describe that announcement, not a guarantee for every present-day display or sensor.
Rank #2
- NON-CONTACT DISTANCE SENSING: Add object detection to robot navigation, parking-distance prototypes, automatic lids, counters and interactive projects; each HC-SR04 uses a 40 kHz ultrasonic burst and echo timing to estimate distance
- 5-PACK FOR REPEATABLE PROTOTYPING: Use multiple HC-SR04 modules across builds, compare sensor positions or keep spares for testing and replacement; each module integrates an ultrasonic transmitter, receiver and control circuit
- 5 V MODULE WITH 3-450 CM RANGE: Connect VCC, Trig, Echo and GND, use a 10 µs trigger pulse and measure Echo duration; resolution is 0.3 cm with an effective angle under 15°, while the controller board and external power source are not included
- PROTECT 3.3 V GPIO: The HC-SR04 operates from 5 V and its Echo output is 5 V, so use a voltage divider or suitable level shifting with 3.3 V inputs; keep the module dry and use it for prototyping rather than calibrated measurement
- FOR ROBOTICS & STEM PROJECTS: Suitable for distance measurement, object detection, automatic lids, parking alerts, robot navigation and other hands-on electronics builds
What Qualcomm claims about security
Ultrasonic capture adds acoustic and depth information that may help distinguish a real finger from a flat image or mold. Qualcomm wrote in 2019: “Our ultrasonic sensor for fingerprint recognition can detect blood flow within the finger and actually prevent hackers from spoofing the device with a photo or a mold of your finger.” This is Qualcomm’s vendor claim; it is not proof that every device using an ultrasonic reader detects blood flow or prevents every spoofing attack.
Qualcomm also mentioned potential future healthcare uses such as heart-rate, BMI, and blood-sugar monitoring as possible OEM applications. Those examples should not be read as validated capabilities of a fingerprint sensor or as features available on the phones discussed here.
Rank #3
- Document link: https://tinyurl(DOT)com/Fringerprint-Sensor
- Storage Capacity: 240 fingerprints
- This module can be controlled through the serial port, or using the computer's serial port
- The product consists of optical fingerprint sensor, high-speed DSP processor, high-performance fingerprint matching algorithm, ultra-large capacity FLASH chip and other hardware and software
- This fingerprint module has stable performance, complete functions, and has multiple functions such as fingerprint collection, fingerprint registration, fingerprint matching, and fingerprint search
Which phones use Qualcomm 3D Sonic Max?
Qualcomm named the vivo X90 Pro+ and iQOO 11 Pro as the first Snapdragon 8 Gen 2 phones with 3D Sonic Max. Qualcomm’s announcement identifies those models; it does not establish current availability in every country, or confirm that every regional version has the same hardware. Check the specification sheet for the exact model and market before buying.
3D Sonic Max specifications
| Specification | Qualcomm’s stated figure | Qualification |
|---|---|---|
| Sensor package dimensions | 20 × 30 mm | Qualcomm product specification. |
| Thickness | 150 µm | Qualcomm product specification. |
| Fingerprint reproduction area | 600 mm² | Qualcomm Technologies, 2023. |
| Two-finger reading | Can read two fingers at once | Qualcomm-described capability; not a claim that every phone enables this in every app or use case. |
| Size versus predecessor | 17 times larger | Qualcomm’s 2023 comparison with the predecessor 3D Sonic Sensor. |
The large sensing area is a practical distinction from smaller fingerprint readers: Qualcomm says the sensor can capture two fingers at once. The stated area and size comparison concern the sensor, not the amount of vascular detail it can resolve.
Quick Recap
Best Value
- ultrasonic sensor, is a kind of sensor that applies ultrasonic technology to detect the distance of objects.
- The sensor adopts closed split waterproof design, the protection grade can reach IP67;
- Compact structure, fixed screw hole design, to solve the user installation and fixing problems;
- Low power consumption design, according to the actual application scenarios, the power consumption can be reduced to applicable;
- Wide range of sensor applications, suitable for various scenarios of object proximity and presence detection, parking management system, robot obstacle avoidance, automatic control, etc.;
Rank #4
- JSN-SR04T ultrasonic distance measuring module working voltage: 5V; Static current: 5mA; Total current work: 30mA; Working range: 21cm-5M; Working frequency: 40KHZ; Detecting angle: 50 degree
- JSN-SR04T ultrasonic distance measuring module provides a measurement range of 21cm-500cm. Blind area is 25cm.
- Ultrasonic distance measure module Small size, easy to use, strong anti-jamming, high accuracy, low voltage and low power consumption. JSN-SR04T integrated with sealed waterproof stripline probe, this sensor suitable for wet and harsh measurement occasions.
- JSN-SR04Tintegrated ultrasonic distance module for horizontal distance messurement,Obstacle avoidance, automatic control, Traffic control, Security, industrial control, has a variety of modes that can be modified manually, suitable for testing and teaching experiments in different occasions.
- NOTE: The device is waterproof, but it couldn't work underwater. JSN-SR04T V3.0 is updated to version 3.0, which solves the problem of blind spot data beating and improves the stability of the product.
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