Wearable Heart Rate Sensor Using Linear Light Source and Error Compensation
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Solution Overview
Problem
Conventional optical heart rate sensors are limited to wristwatch-type products due to the use of a single point light source, making it difficult to apply them to wrist-unattachable band-type products.
Innovation Solution
An apparatus with a heart rate sensor unit that employs a linear light source and four light receiving units, along with an acceleration sensor and display unit, allowing for accurate heart rate measurement even when not fully attached to the wrist, and a method for error compensation by comparing and weighting light signals received by these units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a point light source is used in the optical heart rate sensor, then the device structure is simple, but the device can only be applied to wristwatch-type products and not band-type products
Solution Approach 1:
The patent divides the single point light source into multiple light sources arranged in an array. This segmentation allows the light to cover a wider area and adapt to different wearing scenarios (wristwatch-type and band-type products), resolving the contradiction between structural simplicity and adaptability.
Solution Approach 2:
The optical sensor is designed with multiple light sources and corresponding photodetectors that can function in both wristwatch-type and band-type configurations. This multi-functionality enables the same device structure to be applied to different product types, resolving the adaptability issue.
2Device complexity
If a single photodetector is used, then the device structure is simple, but the light receiving efficiency is insufficient for accurate heart rate measurement
Solution Approach 1:
The single photodetector is segmented into multiple photodetectors arranged in an array, with each photodetector corresponding to a specific light source. This increases the total light receiving area and improves measurement precision while maintaining a relatively simple device structure through systematic arrangement.
Solution Approach 2:
Multiple photodetectors are combined to work together in detecting light signals from the blood vessel. Their outputs are processed collectively to enhance the signal-to-noise ratio and improve heart rate measurement accuracy, resolving the contradiction between structural simplicity and measurement precision.
3Ease of operation
If the sensor is not fully attached to the skin, then the device is more comfortable to wear, but the heart rate measurement becomes inaccurate
Solution Approach 1:
The optical sensor is divided into multiple light sources and photodetectors distributed across a larger area. This segmentation allows the sensor to maintain effective contact with the skin even when not fully attached, as different segments can independently detect light signals, thereby preserving measurement accuracy while improving wearing comfort.
Solution Approach 2:
The patent transitions from a single-point contact configuration to a distributed array configuration across two dimensions. This dimensional change allows the sensor to function effectively with partial skin contact, resolving the contradiction between wearing comfort and measurement precision.
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
Enables accurate heart rate measurement and enhanced light receiving efficiency, applicable to both wrist band and wrist watch types, with stable detection of heart rate signals and flexibility in signal weighting methods based on SNR and operation environment.
Implementation Method 1
PPG (photoplethysmogram) observes optical characteristics of bio tissues such as light reflectivity, absorptance and transmittance that show during volumetric change in blood vessel by using a light
Implementation Method 2
the optical pulse sensor estimates heart rate activities by measuring blood flowing in the blood vessel using an optical characteristic of bio tissues
Implementation Method 3
a curved light guide configured to refract the light emitted from the light source into a plurality of directions
Implementation Method 4
a reflective plate configured to reflect a light emitted to an outside from the light guide into an interior of the light guide
Data Source
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AI summary
The present disclosure relates to an apparatus for measuring bio-information, the apparatus including a heart rate sensor unit configured to measure heart rates by receiving a light that has entered and come out from skin, an acceleration sensor unit configured to output a step count by measuring the step count of a wearer, a display unit configured to display the measured heart rates and step count, and a wrist-wearable connection unit configured to electrically connect the heart rate sensor, the acceleration sensor unit and the display unit, whereby heart rate can be accurately measured using a line light source instead of point light source, even if the apparatus is not fully attached to a wrist. The apparatus includes a heart rate sensor unit configured to improve a light receiving efficiency using four light receiving units.