Hello everyone.
My name is Atsuhiro Fujii from Ritsumeikan University in Japan.
Now, I will explain about our pulse wave generation method, disp2ppg.
This method inputs generated pulse data to the PPG sensor using display.
First, I will explain the background of my research.
With the growing awareness of health management, wearable devices that record biometric information have become widely used.
The most common technique of recording pulse data is called PPG.
It measures pulse data by irradiating LED light onto the skin and detecting changes in the light reflected through blood vessels.
Due to this mechanism, blood flow is necessary for the PPG sensor to measure the value.
A problem arises when wearable devices are used on artificial bodies.
The call, message, clock, and payment functions, and the acceleration, gyroscope, and GPS sensors equipped with wearable devices are available on artificial bodies.
However, the PPG sensor is unavailable on artificial bodies.
We can think of several methods to solve this problem, but another problem may arise.
The best solution we can think of is to let the sensor equipped with the device read arbitrary values.
This method requires user to wear an additional device, but does not require any modification to the smartwatch or application.
Our method inputs values to the PPG sensor without using blood flow, so users of the artificial body can also use commercially wearable devices and applications.
In addition, enabling the input of arbitrary pulse data also leads to the demonstration of the vulnerability of PPG sensors.
Pulse data is one of the most important biological information, as it is used to estimate respiratory rate, detect arrhythmia, predict emotions, and so on.
I will introduce proposed method.
The bloodstream absorbs and reflects the LED light.
To enable this property using displays, Colors that absorb and reflect LED light should be prepared.
Colors are grayscale data.
The more white the display is drawn, the brighter the reflected light will be, and the more black the display is drawn, the darker the reflected light will be.
The optimal Colors vary depending on the display-smartwatch combinations, so we conducted heuristically search and decide the optimal Colors.
I will explain the flow of proposed method.
First, the user wears an additional PPG sensor to acquire data and detect peaks.
The system calculates the heart rate by counting the number of peaks.
Next, prepare a number of Colors equal to the calculated heart rate, and draw them on the display in one minute.
Finally, the user can get the same heart rate on the smartwatch as the one obtained from the additional sensor.
The evaluation experiment was conducted using four displays and five smartwatches.
We used several smartwatches with different operating systems.
Therefore, the data acquisition flow differed depending on the smartwatch.
This is how the data was acquired using display D.
Enter the target heart rate to the console, and the smartwatch will acquire the heart rate.
SMART R was the only smartwatch that was able to correctly input the heart rate using display D.
Therefore, the evaluation of display D was conducted using only SMART R.
These are errors between the target heart rate and the measured heart rate.
Positive values indicate that the heart rate was higher than the target heart rate, and negative values indicate that the heart rate was lower.
The gray points indicate results where the values could not be obtained correctly.
The orange points indicate results with an error of 2.5 bpm or more.
In many results, the accuracy was very good, with errors of less than 3 bpm.
Here is conclusion.
We proposed disp2ppg, which inputs pulse wave to PPG sensor using display.
The evaluation experiment was conducted using four displays and five smartwatches.
As a result, the input error was within 3 bpm in most cases.
In the future, we will investigate a mechanism to automatically determine the optimal Colors.
The device will be miniaturized for attachment to a body part.
Now all finished.
Thank you for your attention.