Apr. 28, 2008 Sometimes the diagnosis of episodes of illness in schizophrenia, rotatory vertigo, or reading and writing deficits needs electro-oculography (EOG), performed using a special medical apparatus. Andreas Bulling, a doctoral student at the Wearable Computing Lab of ETH Zurich, has developed spectacles that could in future make this technique portable.
The expression Wearable Computing includes portable computer systems that a person wears on their body, for example as spectacles, a wristwatch, belt or piece of clothing. However, these portable computers are not operated actively and directly by the wearer as is usual with computer systems. Instead, they support everyday activities, rather in the sense of an intelligent navigation system, an easy-to-operate user interface or long-term medical monitoring.
Potential changes during eye movements
Andreas Bulling is developing a Wearable Eye Tracker in the context of his doctoral thesis. The special spectacles fitted with additional sensors record the wearer’s eye movements. This recording is based on the principle of electro-oculography (EOG), a technique that has been known for more than 30 years and in which eye movements are measured using electrodes – similar to an electrocardiogram (ECG). Currently, the recording takes place in a doctor’s surgery or in a clinic, using static apparatus, and usually needs to be assessed manually by the doctor.
The ETH Zurich researcher has now developed the Wearable Eye Tracker, which might some day replace conventional EOG and could allow for additional applications. The Wearable Eye Tracker can record eye movements while the wearer is moving. This involves using electrodes built into a spectacle frame to measure changes in electrical potential caused by eye movements. However, in contrast to a static EOG, the spectacles can do this for a period of up to eight hours without being connected to mains electricity.
The data is also stored directly in the instrument. In addition, the wearer can completely undertake normal everyday life. The plan in the future is for the spectacles also to recognise automatically the environment in which a person is situated at the time, and what activity he/she is carrying out. To be able to recognise these activities and surroundings, the spectacles must refer back to data already recorded and analysed.
Additional sensors for signal correction
The potential changes generated by the eye movements are transmitted via cables, also built into the spectacles, to a device about the size of a credit card that can be worn on the arm or carried in the trouser pocket for example. Andreas Bulling explains that “The development of the Eye Tracker required first of all the hardware design of the spectacles and the portable equipment to record the EOG signals. Then the next step necessitated the development of software that can process and analyse these signals immediately in real time.”
He says the device must also be able to correct the signals at the same time when necessary. For example ambient light changes the pupil diameter, which affects the EOG signal. Movements of the body, such as walking or running, change the signal as well. This is why the spectacles also contain a built-in light sensor and acceleration sensor, with which appropriate corrections can be made to the signals.
An initial functioning prototype of the Eye Tracker exists and is currently being tested and expanded with new functionalities. A Zurich industrial design company is working in parallel on a further development of the spectacles. The ETH Zurich researcher filed a patent application for his invention at the European Patent Office last October, and is now looking for licensees in the medical or games industries.
An interactive computer game requiring the imitation of eye gestures of various difficulty levels represented on a computer screen has been developed for demonstration purposes. If these are performed correctly, the player moves to the next level of the game.
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