Preface -- Contents -- 1 Disability and Assistive Technology Systems -- Learning Objectives -- 1.1 The Social Context of Disability -- 1.2 Assistive Technology Outcomes: Quality of Life -- 1.2.1 Some General Issues -- 1.2.2 Definition and Measurement of Quality of Life -- 1.2.3 Health Related Quality of Life Measurement -- 1.2.4 Assistive Technology Quality of Life Procedures -- 1.2.5 Summary and Conclusions -- 1.3 Modelling Assistive Technology Systems -- 1.3.1 Modelling Approaches: A Review -- 1.3.2 Modelling Human Activities -- 1.4 The Comprehensive Assistive Technology (CAT) Model -- 1.4.1 Justification of the Choice of Model -- 1.4.2 The Structure of the CAT Model -- 1.5 Using the Comprehensive Assistive Technology Model -- 1.5.1 Using the Activity Attribute of the CAT Model to Determine Gaps in Assistive Technology Provision -- 1.5.2 Conceptual Structure of Assistive Technology Systems -- 1.5.3 Investigating Assistive Technology Systems -- 1.5.4 Analysis of Assistive Technology Systems -- 1.5.5 Synthesis of Assistive Technology Systems -- 1.6 Chapter Summary -- Questions -- Projects -- References -- 2 Perception, the Eye and Assistive Technology Issues -- Learning Objectives -- 2.1 Perception -- 2.1.1 Introduction -- 2.1.2 Common Laws and Properties of the Different Senses -- 2.1.3 Multisensory Perception -- 2.1.4 Multisensory Perception in the Superior Colliculus -- 2.1.5 Studies of Multisensory Perception -- 2.2 The Visual System -- 2.2.1 Introduction -- 2.2.2 The Lens -- 2.2.3 The Iris and Pupil -- 2.2.4 Intraocular Pressure -- 2.2.5 Extraocular Muscles -- 2.2.6 Eyelids and Tears -- 2.3 Visual Processing in the Retina, Laternal Geniculate Nucleus and the Brain -- 2.3.1 Nerve Cells -- 2.3.2 The Retina -- 2.3.3 The Optic Nerve, Optic Tract and Optic Radiation -- 2.3.4 The Lateral Geniculate Body or Nucleus.

2.3.5 The Primary Visual or Striate Cortex -- 2.3.6 The Extrastriate Visual Cortex and the Superior Colliculus -- 2.3.7 Visual Pathways -- 2.4 Vision in Action -- 2.4.1 Image Formation -- 2.4.2 Accommodation -- 2.4.3 Response to Light -- 2.4.4 Colour Vision -- 2.4.5 Binocular Vision and Stereopsis -- 2.5 Visual Impairment and Assistive Technology -- 2.5.1 Demographics of Visual Impairment -- 2.5.2 Illustrations of Some Types of Visual Impairment -- 2.5.3 Further Types of Visual Impairment -- 2.5.4 Colour Blindness -- 2.5.5 Corrective Lenses -- 2.6 Chapter Summary -- Questions -- Projects -- References -- 3 Sight Measurement -- Learning Objectives -- 3.1 Introduction -- 3.2 Visual Acuity -- 3.2.1 Using the Chart -- 3.2.2 Variations in Measuring Visual Acuity -- 3.3 Field of Vision Tests -- 3.3.1 The Normal Visual Field -- 3.3.2 The Tangent Screen -- 3.3.3 Kinetic Perimetry -- 3.3.4 Static Perimetry -- 3.4 Pressure Measurement -- 3.5 Biometry -- 3.6 Ocular Examination -- 3.7 Optical Coherence Tomography -- 3.7.1 Echo Delay -- 3.7.2 Low Coherence Interferometry -- 3.7.3 An OCT Scanner -- 3.8 Ocular Electrophysiology -- 3.8.1 The Electrooculogram (EOG) -- 3.8.2 The Electroretinogram (ERG) -- 3.8.3 The Pattern Electroretinogram -- 3.8.4 The Visual Evoked Cortical Potential -- 3.8.5 Multifocal Electrophysiology -- 3.9 Chapter Summary -- Glossary -- Questions -- Projects -- Reference Sources -- 4 Haptics as a Substitute for Vision -- Learning Objectives -- 4.1 Introduction -- 4.1.1 Physiological Basis -- 4.1.2 Passive Touch, Active Touch and Haptics -- 4.1.3 Exploratory Procedures -- 4.2 Vision and Haptics Compared -- 4.3 The Capacity of Bare Fingers in Real Environments -- 4.3.1 Visually Impaired People's Use of Haptics Without any Technical Aid -- 4.3.2 Speech Perceived by Hard-of-hearing People Using Bare Hands.

4.3.3 Natural Capacity of Touch and Evaluation of Technical Aids -- 4.4 Haptic Low-tech Aids -- 4.4.1 The Long Cane -- 4.4.2 The Guide Dog -- 4.4.3 Braille -- 4.4.4 Embossed Pictures -- 4.4.5 The Main Lesson from Low-tech Aids -- 4.5 Matrices of Point Stimuli -- 4.5.1 Aids for Orientation and Mobility -- 4.5.2 Aids for Reading Text -- 4.5.3 Aids for Reading Pictures -- 4.6 Computer-based Aids for Graphical Information -- 4.6.1 Aids for Graphical User Interfaces -- 4.6.2 Tactile Computer Mouse -- 4.7 Haptic Displays -- 4.7.1 Information Available via a Haptic Display -- 4.7.2 What Information Can Be Obtained with the Reduced Information? -- 4.7.3 Haptic Displays as Aids for the Visually Impaired -- 4.8 Chapter Summary -- 4.9 Concluding Remarks -- Questions -- Projects -- References -- 5 Mobility: An Overview -- Learning Objectives -- 5.1 Introduction -- 5.2 The Travel Activity -- 5.2.1 Understanding Mobility -- 5.2.2 Assistive Technology Systems for the Travel Process -- 5.3 The Historical Development of Travel Aids for Visually Impaired and Blind People -- 5.4 Obstacle Avoidance AT: Guide Dogs and Robotic Guide Walkers -- 5.4.1 Guide Dogs -- 5.4.2 Robotic Guides and Walkers -- 5.5 Obstacle Avoidance AT: Canes -- 5.5.1 Long Canes -- 5.5.2 Technology Canes -- 5.6 Other Mobility Assistive Technology Approaches -- 5.6.1 Clear-path Indicators -- 5.6.2 Obstacle and Object Location Detectors -- 5.6.3 The vOICe System -- 5.7 Orientation Assistive Technology Systems -- 5.7.1 Global Positioning System Orientation Technology -- 5.7.2 Other Technology Options for Orientation Systems -- 5.8 Accessible Environments -- 5.9 Chapter Summary -- Questions -- Projects -- References -- 6 Mobility AT: The Batcane (UltraCane) -- Learning Objectives -- 6.1 Mobility Background and Introduction -- 6.2 Principles of Ultrasonics -- 6.2.1 Ultrasonic Waves.

6.2.2 Attenuation and Reflection Interactions -- 6.2.3 Transducer Geometry -- 6.3 Bats and Signal Processing -- 6.3.1 Principles of Bat Sonar -- 6.3.2 Echolocation Call Structures -- 6.3.3 Signal Processing Capabilities -- 6.3.4 Applicability of Bat Echolocation to Sonar System Design -- 6.4 Design and Construction Issues -- 6.4.1 Outline Requirement Specification -- 6.4.2 Ultrasonic Spatial Sensor Subsystem -- 6.4.3 Trial Prototype Spatial Sensor Arrangement -- 6.4.4 Tactile User Interface Subsystem -- 6.4.5 Cognitive Mapping -- 6.4.6 Embedded Processing Control Requirements -- 6.5 Concept Phase and Engineering Prototype Phase Trials -- 6.6 Case Study in Commercialisation -- 6.7 Chapter Summary -- Questions -- Projects -- References -- 7 Navigation AT: Context-aware Computing -- Learning objectives -- 7.1 Defining the Orientation/Navigation Problem -- 7.1.1 Orientation, Mobility and Navigation -- 7.1.2 Traditional Mobility Aids -- 7.1.3 Limitations of Traditional Aids -- 7.2 Cognitive Maps -- 7.2.1 Learning and Acquiring Spatial Information -- 7.2.2 Factors that Influence How Knowledge Is Acquired -- 7.2.3 The Structure and Form of Cognitive Maps -- 7.3 Overview of Existing Technologies -- 7.3.1 Technologies for Distant Navigation -- 7.3.2 User Interface Output Technologies -- 7.4 Principles of Mobile Context-aware Computing -- 7.4.1 Adding Context to User-computer Interaction -- 7.4.2 Acquiring Useful Contextual Information -- 7.4.3 Capabilities of Context-awareness -- 7.4.4 Application of Context-aware Principles -- 7.4.5 Technological Challenges and Unresolved Usability Issues -- 7.5 Test Procedures -- 7.5.1 Human Computer Interaction (HCI) -- 7.5.2 Cognitive Mapping -- 7.5.3 Overall Approach -- 7.6 Future Positioning Technologies -- 7.7 Chapter Summary -- 7.7.1 Conclusions -- Questions -- Projects -- References.

8 Accessible Global Positioning System (GPS) and Related Orientation Technologies -- Learning Objectives -- 8.1 Defining the Navigation Problem -- 8.1.1 What is the Importance of Location Information? -- 8.1.2 What Mobility Tools and Traditional Maps are Available for the Blind? -- 8.2 Principles of Global Positioning Systems -- 8.2.1 What is the Global Positioning System? -- 8.2.2 Accuracy of GPS: Some General Issues -- 8.2.3 Accuracy of GPS: Some Technical Issues -- 8.2.4 Frequency Spectrum of GPS, Present and Future -- 8.2.5 Other GPS Systems -- 8.3 Application of GPS Principles -- 8.4 Design Issues -- 8.5 Development Issues -- 8.5.1 Choosing an Appropriate Platform -- 8.5.2 Choosing the GPS Receiver -- 8.5.3 Creating a Packaged System -- 8.5.4 Integration vs Stand-alone -- 8.6 User Interface Design Issues -- 8.6.1 How to Present the Information -- 8.6.2 When to Present the Information -- 8.6.3 What Information to Present -- 8.7 Test Procedures and Results -- 8.8 Case Study in Commercialisation -- 8.8.1 Understanding the Value of the Technology -- 8.8.2 Limitations of the Technology -- 8.8.3 Ongoing Development -- 8.9 Chapter Summary -- Questions -- Projects -- References -- 9 Electronic Travel Aids: An Assessment -- Learning Objectives -- 9.1 Introduction -- 9.2 Why Do an Assessment? -- 9.3 Methodologies for Assessments of Electronic Travel Aids -- 9.3.1 Eliciting User Requirements -- 9.3.2 Developing a User Requirements Specification and Heuristic Evaluation -- 9.3.3 Hands-on Assessments -- 9.3.4 Methodology Used for Assessments in this Chapter -- 9.4 Modern-day Electronic Travel Aids -- 9.4.1 The Distinction Between Mobility and Navigation Aids -- 9.4.2 The Distinction Between Primary and Secondary Aids -- 9.4.3 User Requirements: Mobility and Navigation Aids -- 9.4.4 Mobility Aids.

9.4.5 Mobility Aids: Have They Solved the Mobility Challenge?.