iWatch May Use Optical Sensors to Measure Heart Rate and
Apple's iWatch may include optical sensors designed to measure physical functions like heart rate
and oxygen levels, according to electronics analyst Sun Chang Xu of Chinese site Electrical
Engineering Times [Google sell my gift card Translation], who cites supply chain sources with
knowledge of the matter. Xu also indicated that while Apple had planned on glucose monitoring,
non-invasive methods have proven to be highly inaccurate and thus may not be
http://www.huffingtonpost.com/news/youtube/ included in the final product.
Measuring oxygen levels and heart rate are two features the iWatch has been previously rumored to
include and optical sensors, which are used in many medical and health-related products, are a
logical choice for the smart watch.
Pulse oximetry devices, which are often designed to fit over a finger, use optical sensors to measure
oxygen levels in the blood. These sensors are light-based, sending two wavelengths of light through
the skin. Differences in the way the light is absorbed allows the device to detect oxygen saturation in
the blood. The majority of pulse oximeters clip to a fingertip or an earlobe, suggesting a wrist-based
pulse oximeter is difficult, but not impossible, to develop.
Monitoring heart rate via optical sensor is a newer technology that is incorporated into several
fitness products including the Mio Alpha heart rate watch. Typical heart rate monitoring in the past
has required a chest strap, but with an optical sensor, a light shone on the skin can be used to
measure blood flow through capillaries, thus determining heart rate.
The Mio Alpha heart rate monitoring watch
MacRumors spoke to Mio founder and CEO Liz Dickinson about the possibility of an optical heart
rate measurement tool in the iWatch, and she believes the company would absolutely opt for electro-
optical sensing for such a function. She also suggested an iWatch with heart-rate measuring
capabilities would need to fit tightly to the wrist.
Having said that, using electro optical sensing requires a very specific type of design in order to
work accurately. The sensor needs to be in tight contact with the skin with little ability to move.
Perhaps Apple does not care about accuracy during motion but in any event, at the time readings
were being taken even if the person is still, the watch, or band, would need to be flush to the skin.
Electro-optical sensing also requires careful calibration to overcome interference from motion and
noise. The Mio Alpha incorporates a built-in accelerometer and noise filtration software to garner
accurate readings, and it is possible Apple might adopt some of the same technology.
Underside of the Mio Alpha heart rate-sensing watch (Courtesy of DC Rainmaker)
Over the course of the last several months, Apple has hired a number of health experts in fields
related to both heart rate monitoring and pulse oximetry. Two executives from pulse-oximetry
company Masimo joined Apple, including its former Chief Medical Officer. Several of Apple's health-
related hires have also been from C8 MediSensors, a company focused on non-invasive blood
ctly which health-related functions the final iWatch product might measure, rumors have indicated it
http://topyoutubevideos.com/ will include multiple sensors capable of not only measuring heart rate
and oxygen level, but also movement, sleep, hydration levels, and more.