Head-Held Smartphone Ballistocardiogram Sensing for Passive Biometrics

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Solution Overview

Problem

Existing mobile devices require active user interaction or separate wearable accessories for biometric measurements, limiting convenience and integration.

Innovation Solution

Mobile computing devices, such as smartphones, utilize an inertial measurement unit to detect motion signals when held against the user's head, converting them into a ballistocardiogram signal to passively obtain biometric information like heart rate and variability, using machine learning and spectral analysis to ensure accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a wearable computing device is used for passive biometric measurement, then measurement convenience is improved, but additional accessories are required

Engineering Contradiction:

Improvemeasurement convenienceVSAvoidadditional accessories

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent combines the biometric measurement functionality with the existing mobile computing device that the user already carries. The inertial measurement unit and processing capabilities are integrated into the mobile device itself, eliminating the need for separate wearable accessories while maintaining passive measurement convenience.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The mobile computing device is designed to perform multiple functions including biometric measurement, telephony, and computing. By making the mobile device universal, it can serve as both a communication tool and a health monitoring device, removing the need for dedicated wearable biometric sensors.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If an optical solution is used for active heart rate monitoring, then biometric measurement capability is improved, but active user interaction is required

Engineering Contradiction:

Improvebiometric measurement capabilityVSAvoidactive user interaction

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The system performs biometric measurement automatically without requiring user initiation or cognitive engagement. The mobile device autonomously captures motion signals from the inertial measurement unit, processes them through the ballistocardiogram model, and generates health metrics without the user needing to actively participate in the measurement process.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent replaces the optical measurement system with a mechanical/inertial sensing approach. Instead of using light-based optical sensors that require finger placement, the system uses an inertial measurement unit to detect mechanical motions of the head, converting physical motion into biometric data through signal processing.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If passive biometric measurement is implemented using existing sensors, then user convenience is improved, but measurement accuracy may be compromised

Engineering Contradiction:

Improveuser convenienceVSAvoidmeasurement accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent transforms the raw motion signals from the inertial measurement unit into ballistocardiogram signals through specific signal processing transformations. By changing the parameters and representation of the measured data, the system extracts cardiac information from general head motions, maintaining accuracy while using convenient passive sensing.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces a ballistocardiogram signal model as an intermediary between the raw motion signals and the final biometric measurements. This intermediate representation helps isolate and enhance cardiac-related signals from other head motions, improving measurement accuracy while maintaining the convenience of passive sensing.

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Passive biometric measurements provide comprehensive health data without additional accessories, enhancing user convenience and accuracy by leveraging existing sensors for continuous health monitoring.

Implementation Method 1

determine a ballistocardiogram signal based on the one or more motion signals detected by the inertial measurement unit

Methodology Applied

Scientific EffectBallistocardiogram:

Data Source

PatentUS20260020777A1Obtaining Biometric Information of a User Based on a Ballistocardiogram Signal Obtained When a Mobile Computing Devie is Held Against the Head of the User

Publication Date: 2026.01.22 GOOGLE LLC

AI summary

A mobile computing device includes one or more memories to store one or more instructions. an inertial measurement unit. and one or more processors. The one or more processors execute the one or more instructions stored in the one or more memories to: control the inertial measurement unit to detect one or more motion signals generated when the mobile computing device is held against a head of a user of the mobile computing device. determine a ballistocardiogram signal based on the one or more motion signals detected by the inertial measurement unit. obtain, based on the ballistocardiogram signal. biometric information of the user, and output the biometric information of the user.