Alternative communication systems for people with severe motor disabilities: a survey <s> EOG signal <s> The human retina consists of an electrically-charged nerve membrane. This potential is a constant value for a given adaptation without stimulation; it is the retinal resting potential. The retinal resting potential causes an electric field around the eyeball, centered on the optical axis, which can be measured by placing electrodes near to the eye. As a result, the motion of the eye causes a measurable change of DC voltage between the surface electrodes. The same vector coordinate system employed in the modern computer mouse may be adapted for use with our electro-ocular interface. Such a device would provide a relative position of gaze and have application in both hands-busy and assistive research. The theory behind our device, hardware design, the experimental results, and efficacy of the system are presented. <s> BIB001 </s> Alternative communication systems for people with severe motor disabilities: a survey <s> EOG signal <s> Bio-based human computer interface(HCI) has attracted more and more attention of researches all over the world in recent years. In this paper, an EOG-based HCI system is introduced. It is composed of three parts: EOG amplifying and acquisition, EOG pattern recognition and control command output. Three plane electrodes are employed to detects the EOG signals, which contains the information related to the eye blinking and vertical( or horizontal ) eye movements referred to pre-designed command table. An online signal processing algorithm is designated to get the command information contained in EOG signals, and these commands could be used to control the computer or other instruments. Based on this HCI system, the remote control experiments driven by EOG are realized. <s> BIB002
The EOG signal is the electrical signal generated by the difference of potential between the cornea and the retina, from 2 to 20 mV but with recorded signals ranging from 15-200 μV BIB001 . This potential is due to the large presence of active nerves in the retina compared to the front of eye BIB002 . Several experiments show that the corneal part is a negative pole while the retina is a negative one in the eye. Then, analyzing the eyeball as a dipole eye movements can be registered through the EOG, with each degree representing 14 to 16 μV in horizontal and also vertical way. Sampling rate for electrooculogram acquisition should reproduce components up to 15 Hz BIB001 . Traditionally, for EOG recording are placed five Ag/AgCl self-adhesive electrodes: (i) one pair above the eyebrow and below the eye to record vertical movements; (ii) one pair next to the lateral canthus, to record horizontal movements and (iii) one over a neutral site, acting as reference.