Camera-based heart rate monitors, typically found in smartphones and other devices, work by using the device's camera and light source (usually an LED flash) to detect changes in blood flow in your fingertip or skin.
Here's a breakdown of the process:
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Illumination: The device's light source shines light onto your skin, typically through your fingertip when you place it over the camera lens.
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Light Absorption and Reflection: Blood absorbs certain wavelengths of light and reflects others. The amount of light absorbed or reflected changes slightly with each heartbeat as blood volume fluctuates in the capillaries near the skin's surface.
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Camera as a Sensor: The camera acts as a sensor, capturing the subtle changes in light reflection or absorption. It's essentially measuring the variations in color and opacity caused by the pulsating blood flow.
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Signal Processing: Sophisticated algorithms analyze the captured video data to identify the rhythmic changes that correspond to your heartbeat. These algorithms filter out noise and other interfering factors to isolate the heart rate signal.
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Heart Rate Calculation: Based on the identified rhythmic patterns, the device calculates your heart rate in beats per minute (BPM).
In short, these monitors use photoplethysmography (PPG), a non-invasive optical technique, to measure blood volume changes in the microvasculature. While convenient, it's important to note that the accuracy of camera-based heart rate monitors can be affected by factors like:
- Movement: Excessive movement can introduce noise and distort the signal.
- Pressure: Applying too much or too little pressure on the camera lens can affect readings.
- Skin Tone: Skin pigmentation can impact light absorption and reflection, potentially affecting accuracy.
- Ambient Light: Strong ambient light can interfere with the sensor's ability to detect subtle changes.
Therefore, while these monitors offer a convenient way to track your heart rate, they may not be as accurate as dedicated heart rate monitors like chest straps or pulse oximeters, especially during strenuous activity.
