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Under-display ultrasonic fingerprint sensors do capture information from below the surface of a finger, but that does not mean ordinary phones map your blood vessels. Commercial readers use returning sound echoes to reconstruct fingerprint features in three dimensions. Vessel imaging has been demonstrated in laboratory studies, not established as a routine feature of mass-market phones.
What an under-display ultrasonic fingerprint sensor detects
An ultrasonic reader sends sound pulses through the display stack and interprets the echoes that return from a finger. The resulting data can represent three-dimensional fingerprint structure rather than only a flat surface image. Qualcomm says its 3D Sonic technology scans fingerprint pores and can work through glass or metal, including when fingers are wet or contaminated.
That acoustic depth is what makes “see beyond the skin” plausible as a description of the underlying technology. It does not, by itself, mean a phone is producing a map of the vessels beneath the fingerprint. The sensor’s commercial purpose is fingerprint recognition; evidence of vessel imaging comes from separate research systems.
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Does a phone map the blood vessels in your finger?
There is laboratory evidence that ultrasound-based systems can image vessels beneath a fingerprint, but it does not establish that current consumer phones routinely do so.
#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
Under-display experiment using a phantom
A 2021 IEEE Sensors Journal study described an under-display ultrasonic fingerprint-recognition experiment that imaged a vessel beneath a fingerprint. The researchers used a 40 MHz PZT-5H sensor and produced 500 × 500 DPI images in a two-layer phantom. That is a research demonstration using a constructed test sample, not proof that a phone’s built-in reader maps vessels in everyday use.
Research using ultrasound and photoacoustics
A separate 2021 Scientific Reports study used a 15 MHz ultrasound/photoacoustic array to obtain three-dimensional images of fingerprints and subdermal vessels from wet and dry fingers. Its authors noted that conventional ultrasonic fingerprint sensors have limited sensitivity to subdermal vascular structures and presented vessel sensing as a possible future direction for stronger liveness detection.
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
These studies show that vessel imaging is an active research capability under particular experimental conditions. They do not show that a consumer phone generates a medical-quality vascular map, measures blood sugar, or diagnoses a health condition.
Ultrasonic and optical readers compared
| Feature | Optical under-display reader | Ultrasonic under-display reader |
|---|---|---|
| What it captures | A two-dimensional image of the fingerprint surface. | Acoustic echo information that can represent three-dimensional fingerprint structure. |
| How it reads through a display | Uses an optical image of the finger surface through the display area. | Sends sound pulses through display layers and interprets their echoes. |
| Wet or contaminated fingers | Not established in the supplied sources. | Qualcomm says its 3D Sonic technology can work with wet or contaminated fingers. |
| Liveness and spoof resistance | Not established in the supplied sources. | Depth and acoustic information may aid liveness checks, but the degree of protection depends on the implementation; Qualcomm’s security statement is a vendor claim. |
| Vessel imaging | Not established in the supplied sources. | Demonstrated in laboratory research, but not established as a routine consumer-phone feature. |
| Size and thickness | Not stated in the supplied sources. | Qualcomm specifies its 3D Sonic Max package as 20 × 30 mm and 150 µm thick. |
The comparison describes broad differences, not a guarantee that every phone using one type will behave alike. Reader performance depends on the particular sensor and device implementation.
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
What Qualcomm 3D Sonic Max specifications mean
Qualcomm specifies the 3D Sonic Max sensor package at 20 × 30 mm, 150 µm thick, with a 600 mm² 3D fingerprint reproduction. The company says it can read two fingers at once and is 17 times larger than its predecessor, the 3D Sonic Sensor. These are Qualcomm’s product specifications and claims; they describe the sensor, not a blood-vessel imaging feature.
Qualcomm’s 2017 announcement reported scanning through OLED display stacks up to 1,200 µm thick, cover glass up to 800 µm thick, and aluminum up to 650 µm thick. Those are figures from that announcement, not universal limits for every ultrasonic reader or current phone.
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.
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. Availability depends on market and can change; check the specifications for the exact regional model before buying. The presence of this sensor does not establish that either phone maps blood vessels.
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What ultrasonic scanning can—and cannot—say about security
Capturing depth and acoustic information can give a fingerprint system more data for liveness checks than a simple flat image, but it does not make spoofing impossible. Qualcomm stated in a 2019 article: “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.” That is the vendor’s security claim, not independent proof that every device using ultrasonic recognition detects blood flow or defeats all presentation attacks.
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.;
Qualcomm’s 2019 article also discussed possible healthcare uses—including heart-rate, BMI, and blood-sugar monitoring—as potential future OEM applications. Those possibilities should not be confused with validated features of current phones. The cited laboratory vessel-imaging work likewise does not establish a consumer medical measurement.
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