Discussion and Future Directions for Eye Tracker Development

Eye and gaze tracking have a long history but there is still plenty of room for further development. In this concluding chapter for Section 6, we consider future perspectives for the development of eye and gaze tracking.

Evaluating Eye Tracking Systems for Computer Input

When a human uses an eye tracker for computer control, the eye is called upon to do ‘double duty’. Not only is it an important sensory input channel, it also provides motor responses to control the computer. This chapter discusses methods of evaluating the interaction. When an eye tracker is used for computer input, how well does the interaction function? Can common tasks be carried out efficiently, quickly, accurately? What is the user’s experience? How are alternative interaction methods evaluated and compared to identify those that work well, and deserve further study, and those that work poorly, and should be discarded? These are the sorts of questions that can be answered with a valid and robust methodology for evaluating eye trackers for computer input.

Computer Control by Gaze

This chapter provides an overview of gaze-based interaction techniques. We will first explore specific techniques intended to make target selection easier and to avoid the Midas touch problem. We will then take a look at techniques that do not require the use of special widgets in the interface but instead manipulate the rendering on the basis of eye gaze to facilitate the selection of small targets. Dwell-based interaction makes use of fixations; recent research has looked into the other option, using saccades as the basis for eye gestures. We will also discuss examples of how eye gaze has been used with other input modalities (blinks and winks, keyboard and mouse, facial gestures, head movements, and speech) to speed up interaction. Finally, we will discuss examples of interaction techniques in the context of a specific area of application: navigating information spaces.

Safety Issues and Infrared Light

Infrared light is the most common choice for illumination of the eye in current eye trackers, usually produced via IR light-emitting diodes (LEDs). This chapter provides an overview of the potential hazards of over-exposure to infrared light, the safety standards currently in place, configurations and lighting conditions employed by various eye tracking systems, the basics of measurement of IR light sources in eye trackers, and special considerations associated with continuous exposure in the case of gaze control for communication and disabled users. It should be emphasised that any eye tracker intended for production should undergo testing by qualified professionals at a recognised test house, in a controlled laboratory setting. However, some knowledge of the measurement procedures and issues involved should be useful to designers and users of eye tracking systems.

Eye Tracker Hardware Design

Designing an eye tracker involves choosing the most appropriate hardware components. A variety of hardware components are available for building an eye tracker, but it is not obvious which ones are the most appropriate. The common factors to consider are: sensitivity to low light, conditions, camera speed, camera fidelity, weight, the working distance of the user, light emission levels (for safety), and cost. This chapter discusses the hardware components used in most eye trackers. It is our hope that the overview provides sufficient understanding of the hardware components that it could be used to make your own eye tracker.

Eye Anatomy, Eye Movements and Vision

This chapter introduces the basics of eye anatomy, eye movements and vision. It will explain the concepts behind human vision sufficiently for the reader to understand later chapters in the book on human perception and attention, and their relationship to (and potential measurement with) eye movements. We will first describe the path of light from the environment through the structures of the eye and on to the brain, as an introduction to the physiology of vision. We will then describe the image registered by the eye, and the types of movements the eye makes in order to perceive the environment as a cogent whole. This chapter explains how eye movements can be thought of as the interface between the visual world and the brain, and why eye movement data can be analysed not only in terms of the environment, or what is looked at, but also in terms of the brain, or subjective cognitive and emotional states. These two aspects broadly define the scope and applicability of eye movements technology in research and in human computer interaction in later sections of the book.

Conclusion and a Look to the Future

Gaze-controlled computers had already been utilized successfully for well over two decades before the COGAIN project started. However, those actually benefitting from the technology were comparatively few compared to the numbers who needed it. During the five year course of the project, however, systems, software and strategies were developed that made this technology potentially available, given appropriate support and technology, to groups who might not have even considered eye control a possibility. As a result, gaze control technology was opened up to a much wider group of people. In this final chapter, we sum up research presented in this book and close it by presenting some future trends and areas with high potential for applied use of eye tracking and gaze interaction.

Communication and Text Entry by Gaze

There are several ways to write by gaze. In a typical setup, gaze direction is used to point and dwell-select letters on an on-screen keyboard. Alternatively, if the person cannot fixate, the eyes can be used as switches using blinks or rough gestures to select items. This chapter introduces different ways to enter text by gaze and reviews related research. We will discuss techniques to enhance text entry by gaze, such as word and letter prediction, and show how the possibility of adjusting the duration of the dwell time affects learning and typing speed. In addition, design issues such as keyboard layout and feedback are raised, with practical examples and guidelines that may aid in designing interfaces for gaze-based text entry.

Features of Gaze Control Systems

Severely disabled people will often spend a significant part of their waking day using gaze control. Technology has a positive impact on many areas of their life. What simple features do people who have severe and complex disabilities need to use gaze control technology? In this chapter, we consider features that are enhancing the effective use of this innovative and rapidly growing method of computer control. It also provides practical hints in finding and choosing the best gaze control system for each individual.

Image Analysis

This chapter focuses on the image processing part of eye tracking systems. Basic knowledge of image processing is assumed. After an overview of the possible input images and some remarks on preprocessing of the images, we will focus on the detection relevant features such as pupils and glints. The last part of this chapter focuses on estimating positions of these features. It is not possible to present a comprehensive solution for an eye tracker in this chapter; however, we will indicate possible yet simplified methods in the different steps of processing and demonstrate how images can be processed to obtain real-time performance. The program code is given in Matlab (Octave) language for clarity.