Turning Eye Movement To Handwriting With New Device
The device, which is based on a visual illusion that enables the eyes to follow smooth and clear trajectories after only several hours of training, is described in the July 26 edition of the journal Current Biology. People can use the device like a pen for writing numbers, letters, figures, their signature, and even use their eyes to draw using a very simple technique that consists of an oculometer and a computer screen.
Whilst existing writing devices already use eye movements to enable a person to write, they only have a limited range of words or letters displayed on the screen that are stored in a database, yet the new device now allows users to draw their own figures. Even though the human eye can follow a moving object very efficiently, it is not capable of performing smooth, regular movements in front of a static background, and any attempts of doing so have, so far, resulted in a series of quite irregular jerks.
Jean Lorenceau, a researcher at the Centre de Recherche de l'Institut du Cerveau et de la Moelle Epinière (CNRS/UPMC/Inserm) developed the idea of using a visual illusion called reverse-phi to obtain smooth trajectories of the eye. Reverse-phi has been known since the 1970s, yet until now, there have been no applications to use this technique.
Reverse-phi creates an illusion by displaying several hundred disks whose luminance varies over time at a frequency of around 10-15 Hertz (Hz) on a screen.
Luminance is the intensity of a broad source in a given direction, divided by the apparent area of this source in the same direction. It is a photometric quantity, i.e. it depends on the sensitivity of the human eye.
When the user's eyes move over this flickering background, the person gains a clear impression that the disks move with the displacement of the eyes and because the human eye is capable of following with precision moving objects, the illusory movement of the disks, induced by the movement of the eyes, provides some kind of moving support that allows users to realize regular and non-jerky trajectories. The movement of a user's eye is recorded by an oculometer and very simple software translates these movements into a virtual on-screen image.
An oculometer records eye movements by analyzing images of the human eye captured by a camera to calculate the direction in which the subject is looking. The training process to manage eye movements and draw letters typically consists of 2 to 4 training sessions that are around 30 minutes long. According to trials, subjects first learned to perceive the reverse-phi movement and then to "cling" onto this movement, in a way similar to a surfer "clinging" onto a wave. By progressively learning to 'surf' on this visual illusion of movement, subjects were able to guide their eye movements at will.
The device enables well-trained individuals to write almost as fast as by hand, simply by using the movement of their eyes. At first, the concentration on the task of drawing figures can become tiring, although training enables creating automatisms that facilitate writing.
Patients suffering from limb paralysis would greatly benefit by being able to personalize their writing, create their own signature and overall would enhance their lives by being able to express themselves and communicate more freely and creatively. The next level of this research proposes the system to be trialed by people suffering from amyotrophic lateral sclerosis. According to Lorenceau's beliefs, the system also paves the way for other applications. For instance, it could be used to train pilots, surgeons, sportsmen, artists and other people, whose activities require precise oculomotor control. Another potential application could be to design security systems that are based on recognition of eye movements.
Written by Petra Rattue