In this project, the main idea is to provide a communication channel between a computer and a person suffering from diseases such as ALS or paralysis. These diseases prevent patients from using their lip and arm muscles. Our project will make use of EOG signals from near patient’s eyes. A special electronic circuit will convert EOG(Electrooculogram) signals to digital and processable signals. With this said, we will be able to determine when and to which direction the person moves his/her eyes. This will pave the road for many applications to be built on. In this project, we aim to detect the person’s eye movements. The proper way to do that is to use EOG signals around the eyes. There are comparisons of EOG and other well-known methods such as EEG. These comparisons show that EOG based HMI can be significantly faster.1 After capturing EOG signals using appropriate sensors, we will apply several hardware filtering methods. Then, we will amplify those low power signals to be able to perform computations by a microprocessor. We will use instrumentation amplifiers specialized for medical purposes for amplification and filtering. Our next step will be to classify the EOG signals.
Electrooculography (EOG) is a method, which graphically analyzes electric potential differences existing between retina and the cornea. In this method designers/engineers try to analyze different signals obtained by electrodes placed near the eye. Electric potential differences with different amplitudes on different electrodes give an idea about the position of user’s eyes. Our purpose in this project is to control of electronic devices by analyzing EOG signals and generating commands accordingly. There are paralyzed people, thousands in our country and millions all over the world1. Successfully designed EOG based control system will make them independent of someone’s help at least for certain activities. Electrooculograms are convenient and efficient means of recording eye positions2. There are different available systems for controlling devices such as a wheelchair3 or other human machine interfaces (HMIs)4. Electrooculograms are signals that are easy to amplify and remove artifacts from. They are very low frequency bio-signals and their amplitudes are much higher with respect to EEG signals. This makes amplification and filtering circuit designs easy and low cost. Corneal-retinal potential (CRP) differences are can be measured by the help of electrodes placed near to eyes and cheekbones as shown in the following figure.
Figure 1. Example electrode placement points on face.
(VU: Vertical Up, VL: Vertical Low, HL: Horizontal Left, HR: Horizontal Right, REF: Reference point for In-Amps, GND: Electrical Ground.)
Figure 2. Symbolic, different angle of horizontal eye movement effect and their voltage levels.
Different angle of eye movements results with proportional voltage amplitudes at the output of the circuit. In the following figure, relation between eye movement and amplitude of electrooculogram is shown. This creates an opportunity for us to design a system that can analyze exact position of the eyes with very high accuracy and precision.
Electrooculogram technology has the potential to improve many people’s life, and transform the way we live. Ophthalmological diagnosis is definitely the most promising one among all. A large number of paralyzed people are having huge difficulties communicating with their loved ones. Our EOG project promises a new hope for such people. This system is going to be non-invasive, meaning that it will be just another accessory and will be easy to use. Our project will also be used for investigating how vision works in different activities during the day. Quite a lot of researchers all around the world are working on the subject of monitoring body activities through eyes. Sleep quality monitoring is an example for potential use of this technology. Eugene Aserinsky had discovered REM sleep (part of the sleep in which we dream) in 1953 using EOG and proved that our eyes move rapidly during this phase of the sleep6. Compared to video recording eye tracker systems, goggles using EOG technology is capable of using lower power and assure a more suitable design. EOG can also be used for entertainment purposes with proper software support. It is already in use for performance capture technology used in animation movies. With captured eye movements of the actors/actresses, the animations are almost indistinguishable from the real scenes.
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