Communication is ensured through an exchange of information, which can be achieved using different types of communication media. The way a man provides information to a technical system represents a very specific category of communication. Input information is mediated to a technical system through various peripheries, e.g. a keyboard, mouse, light pen or a punch tape for a computer. Whenever there appear some reasons, which restrain human users from using standard peripheries, we are facing a serious problem.
There are some health problems that make usage of a personal computer rather difficult. Namely, this is the case of severe motoric handicaps, which make any sort of manipulation with fine objects impossible. Since grasping any small object becomes a challenge for the corresponding patients they are prevented from utilizing a computer mouse, the basic PC periphery, in a standard way. During the last ten years computers became so frequent and common instruments that one cannot do without them in everyday life. That is why it is necessary to search for new means, which will support man-computer communication.
On the other hand, ICT can serve as a unique means of contact with the world for many handicapped persons. Computer can ensure number of services for challenged people: in the most severe cases ICT can substitute for some of their missing abilities and act as the main mediator of contact with the environment. ICT is ready to support education requirements as well as become a tool for training, rehabilitation and development of various abilities (e.g. memory or speech function). The choice of an appropriate computer periphery becomes a crucial question, which has to be resolved with respect to the complex needs of the specific challenged person also taking into consideration the financial aspect. The market offers numerous gadgets ranging from simple electromechanical switches and special trackballs or keyboards to special sophisticated systems for control of a cursor position.
There were analysed various options how to design new computer peripheries at the Department of cybernetics of the Czech Technical University in Prague (http://cyber.felk.cvut.cz) and we have developed the system I4Control®, which offers a means to control a computer through eye movements.
Location of the camera in the device
During the design phase priority was set on creation of an appliance, which is reliable but cheap, universal, easy to install and utilize. We have decided for videooculography (VOG) as the principal method used for gaze tracking, because this solution is sufficiently precise, relatively cheap and first of all it is non-contact, which makes it user-friendly as there is no need to glue electrodes or to apply special contact lenses.
The sensor input of the I4Control® system is ensured by a tiny camera, which is fastened to the head of the user using a spectacle frame. This ensures that the same type of image is obtained independently of the movements of the user (user's head does not have to be fixed). The main parameters for the choice of the camera have been its price and size. It was verified during the preliminary experiments that a simple black&white PAL camera with a CCD sensor (discrimination 208 x 156 points) fully meets our requirements.
The second part of the I4Control® system includes the control module which processes the PAL signal from the camera. Here, the PAL signal is digitalized, the pupil is detected (using classic filtering), and its position is calculated and expressed in the appropriate coordinate system. The output of the control module provides information about the requested modification of a cursor position, namely the difference [Δx, Δy]. This value is transmitted using standard USB interface into a PC.
Working with the I4Control® System
At the beginning, the system I4Control® has to be correctly calibrated for a specific user. The user is asked to fix his/her gaze on the centre of the screen to specify the stable position - it is set and recorded by pressing the red switch of the control module. From now on, the user has two options: he/she can control the cursor position using eye movements only or both eye and head movements (if the handicap allows for that). The green switch of the control module ensures the choice between both these alternatives.
The system does not transfer a position of the computer cursor directly on the spot, which is being observed by the user. It just ensures that the cursor flows in the same direction as eyes of the user with respect to a stable position set during the calibration phase. This means that the actual eye position does not effect the cursor position directly, but it changes the direction of cursor movement (in the same way as a joystick). The system evaluates the present position of the user's eye, compares it to the stable position and consequently makes the choice of corresponding actions. It works in an incremental mode: as long as an eye is out of the stable position the system keeps sending signals instructing the cursor to move on in the corresponding direction (given by the actual position of an eye in the coordinate system of the camera), this is stopped once an eye is back in the stable position. There is another action, which can stop the cursor movement, namely when the user closes his/her eye. This is interpreted as a signal "to click" - one can emulate either click or double-click, the duration of the time interval with closed eyes distinguishes both options. This duration can be set for individual users so that spontaneous blinks can be filtered out.
Text Editing using I4Control®
The resulting system emulates a standard PC mouse. Such a choice facilitates simple installation since I4Control® can be connected to any PC through a standard USB interface. As soon as this is ensured the user can control through eye (sometimes complemented by a head) movements all installed computer programs communicating with a mouse. Consequently, handicapped users can work with a software keyboard, which is provided by many operation systems (e.g. from OS Windows 2000 up) and write the text. This tool opens new horizons for handicapped users, who can fully utilize text editors and get access to writing e-mails or to surfing the Internet.
Gertie - An Educational Toy
One has to get used to utilizing his or her eyes for control of foreign objects. The training can become a fun provided there are available appropriate tools. We have designed and created a special toy car called Gertie, which can be controlled by eye movements. It is intended to help the user to master the communication with a technical appliance through I4Control®.
The toy is constructed from LEGO and it can be controlled using following simple signals provided by the user-driver: if he/she looks up the car goes forward, if he/she looks down the car goes back. The car turns left or right when the user-driver looks in the same direction. And sufficiently long eye blink is interpreted as a directive to rotate the car locator.
Advantages of the I4Control® System
- communication - the appliance can be connected to any PC using standard USB interface
- emulation of a PC mouse - this feature ensures that the user can work with any mouse-controlled PC applications installed on the used computer, the user can utilize all SW tools he/she is used to
- mobility - the appliance is small, compact and easy to transport
- simple installation - the appliance is as simple to install as the PC mouse
- straightforward utilization - after initial calibration for the individual user, there is no need to repeat this process during later usage
- low price
The system I4Control® has been tested in a number of experiments. The pilot testing was ensured in the Jedlička's Institute and School for Handicapped Youngsters. In the group of the first users there was a boy who lost his hand after an accident as well as a boy with muscular atrophy. The system I4Control® was very well accepted and the students were able to master it very quickly. It took about ten minutes and they were able to "list through" special e-learning materials, write in a text editor as well as draw simple pictures.