As THE expert for light in many different areas, OSRAM also provides some very nifty solutions for wearable devices. Read our interview with WT | Wearable Technologies Conference 2017 EUROPE speaker Chris Goeltner who is product manager at Osram Opto Semiconductors to learn more.
With what can you help wearable product makers exactly?
The field of wearables is growing very fast. LED technology is used in many applications within this sector: from precise heart rate measurements to iris scans and fingerprint recognition. Wearables also require LED for the display lighting, light sensors, etc.
We therefore offer a broad portfolio of LED for the wearable application.
There is an increasing interest in medical measurement methods that can be integrated into so-called wearable gadgets such as watches, smartphones or fitness bracelets. It started with fitness trackers determining the step frequency by using acceleration sensors. Now optical sensors expand the possibilities of self-observation, as they also offer a straightforward measurement of the heart rate and oxygen saturation of the blood. Biofy sensors are a typical area of expertise in which we can support our partners and customers in providing the latest and best-suited LED and sensor products, based on our high-efficiency chip technology.
Our R&D team is driving the evolution in many ways: the LED technology is becoming even more efficient, consumes even less energy, offers a higher sensitivity and also becomes even more compact.
The new IR Topled D5140 photodiode from Osram Opto Semiconductors e.g. requires considerably less pc board space than before. It enables more compact sensors to be produced for monitoring fitness levels, for example in fitness armbands. The spectral sensitivity of the D5140 has been optimized for visible light and allows precise heart rate measurements using red or green light. The component is also ideal as an ambient light sensor.
Measuring heart rate with light has been a revolution for the wearable market. Were you involved in this game changer?
Yes, we certainly were. In addition to light emission, Osram Opto Semiconductors develops and produces photodetectors and offers a full line of optical sensors. They are used in automotive and mobile applications, including heart rate monitoring, ambient light, and proximity sensing. Our key differentiator is the knowledge of the respective application ecosystem that allows our customers fast time to market success. Osram components are being used by the majority of the leading brands in the wearables market.
How it works: The proven SFH 2440 and the new extremely compact IR Topled D5140 are ideal for optical sensors for pulse rate measurements, on the wrist for instance. It works by shining visible light on the surface of the skin, some of which is absorbed or reflected to the detector. As arterial blood absorbs more light than the surrounding tissue, the strength of the detector signal changes with the volume of blood through which the light passes. The periodicity of the signal indicates the heart rate. However, infrared light which shines onto the measuring point from the surroundings and disperses in the body also reaches the photodiode. In practice, the sensor consisting of juxtaposed light source and detector is located directly on the skin, usually on the wrist or fingers. Due to the location the measurement is made at different wavelengths – green light has established itself as the best option for the wrist, red and infrared light for the finger.
The Topled D5140 offers an outstanding signal-to-noise ratio because it registers the reflected light particularly well while at the same time suppressing the infrared light. Thanks to its short switching time, the light signal modulated with the heart rate can be time-resolved perfectly. The IR Topled D5140 allows our customers to design more compact sensors, preserving the high signal quality offered by the SFH 2440.
OSRAM recently introduced a new broadband infrared LED. What is special about this new emitter?
Near IR spectroscopy is one of the fast growing mobile consumer applications (e.g. for food freshness detection). In order to allow for the required miniaturization, a single LED light source replaces what has been implemented by a whole cluster of lights with different wavelengths. For the first time, Osram Opto Semiconductors is using converter technology for infrared emitters. The result is a LED that emits broadband infrared light in a wavelength range from 650 to 1,050 nanometers (nm). The main application is near-infrared spectroscopy, for example for analyzing food.
The basis of the SFH 4735 is a blue 1 mm2 chip in UX:3 technology. Its light is converted into infrared radiation with the aid of a phosphor converter developed specifically for this application. A residual blue component in the light helps users target the area they want to investigate. The emission spectrum of the SFH 4735 has a homogeneous spectral distribution in the infrared range. The chip is mounted in the proven and compact Oslon Black Flat package which is characterized in particular by good thermal resistance.
Applications fields: In addition to professional application fields the new infrared LED opens this measurement technique up to the consumer market. One option would be a compact sensor – like a USB stick – which would be used with an appropriate smartphone app to measure calories, freshness or nutritional content. Compact units for spectroscopic chemical analyses open up a completely new range of applications in consumer electronics. Experts expect that it will be possible in the near future to integrate spectrometers directly in mobile devices. The new technology is a natural extension of biomonitoring, in other words, the trend for measuring various vital signs such as pulse rate and calorie consumption. A smartphone spectrometer will enable users to monitor the food they eat in a similar manner.
What is your favorite wearable at the moment? Do you wear a wearable regularly?
I have tested dozens of wearable products in the past year. My personal key requirements are: time is permanently displayed, GPS function for outdoor navigation without a cell phone, accurate heart rate measurement for heart rate variability data, battery life of at least a week. Depending on the particular lifestyle every user has his/her favorite set of features, manufacturers are scrambling to bring out new and diversified models to increase their market share.
You can meet Chris in person in Munich on February 7-8 next year at our WT | Wearable Technologies Conference 2017 EUROPE. Register here.
