How a Wearable Device Measures Heart Rate and Blood Flow with Lasers

This patent describes a wearable device that uses a single laser and two different optical sensors—an image sensor and a photodiode—to measure both blood flow patterns (SPG) and blood volume changes (PPG) from biological tissue.

What it covers

This patent details a wearable device equipped with a special optical sensor module. This module uses an image sensor to capture light reflected from your body tissue, and a separate photodiode to do the same. A single laser light source illuminates the tissue, and both sensors pick up the reflected light. The image sensor processes its data to create a speckleplethysmography (SPG) measurement, which shows tiny changes in blood flow, while the photodiode processes its data for a photoplethysmography (PPG) measurement, which tracks changes in blood volume. A key feature is that the distance between the image sensor and the photodiode is less than half the distance between the image sensor and the laser light source. For example, a smartwatch could use this to get more detailed heart health data.

What it doesn't cover

• —Does not cover non-wearable devices that perform similar optical measurements.
• —Does not cover systems that use light sources other than a laser to illuminate the tissue.
• —Does not cover devices that do not include both an image sensor and a photodiode for measurement.
• —Does not cover devices where the distance between the image sensor and photodiode is 50% or more of the distance between the image sensor and the light source.
• —Does not cover systems that only generate either SPG or PPG measurements, but not both simultaneously.

The clever bit

The novelty lies in integrating both an image sensor for detailed speckle patterns (SPG) and a photodiode for overall blood volume changes (PPG) into a single, compact optical module within a wearable device, all while using one laser and a specific sensor arrangement for optimal data capture.

Why it matters

Combining both SPG and PPG measurements in a single, compact wearable device could offer more comprehensive and accurate insights into cardiovascular health. PPG is widely used for heart rate, but SPG can detect more subtle blood flow dynamics, potentially identifying issues earlier or with greater precision. This could lead to more advanced health monitoring features in consumer devices and medical wearables.

Real-world examples

• 1.Smartwatches with advanced health tracking
• 2.Fitness trackers monitoring heart rate and blood oxygen
• 3.Wearable medical sensors for continuous vital sign monitoring
• 4.Smart rings with health features