Glossary

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Open-Vocabulary Detection(also: Open-Vocabulary Object Detection, OVD)

A class of computer vision object detection models that accept arbitrary text queries at inference time rather than being restricted to a fixed set of pre-trained classes. Instead of only recognizing, for example, the 80 COCO categories, an open-vocabulary detector (such as…

OpenDyslexic(also: Open Dyslexic)

A free, open-source typeface specifically designed to improve readability for people with dyslexia. The font uses heavier bottom portions on letters to help prevent visual rotation and uses unique letter shapes to reduce confusion between similar characters. However,…

OpenSCAD

An open-source, code-based 3-D computer-aided design (CAD) application that uses a scripting language to define 3-D models through constructive solid geometry operations. Unlike visual modeling tools, OpenSCAD creates models from textual descriptions of geometric primitives and…

Optacon(also: Optical-to-Tactile Converter)

A historical assistive device developed in the 1970s that enabled blind people to read printed text by converting visual images of letters into tactile vibration patterns felt with the fingertip. Users would move a small camera across printed text while their other hand rested…

Optical Braille Recognition(also: OBR)

A technology that uses cameras or optical sensors to detect and interpret embossed Braille characters, converting them into digital text. Optical Braille recognition works by capturing images of Braille pages and analysing the patterns of raised dots — typically by detecting…

Optical Character Recognition(also: OCR, Text Recognition)

Technology that converts images of text—whether typed, handwritten, or printed—into machine-readable text data. OCR is used in accessibility to extract text from images, documents, video frames, and real-world scenes, enabling screen readers to read text that would otherwise be…

Optical Character Recognition (OCR)(also: OCR, Text Recognition)

Technology that converts images of text — such as scanned documents, photographs of signs, or PDF pages stored as images — into machine-readable text that can be processed by screen readers, search engines, and other software. OCR is a critical tool for making scanned documents…

Optical Flow

A computer vision method that estimates the apparent motion of objects between consecutive video frames by tracking pixel displacement patterns. Optical flow calculates velocity vectors showing movement direction and speed across an image. In assistive technology, optical flow…

Opticon(also: Optical-to-Tactile Converter)

An early assistive technology device developed by Dr. James Bliss in the 1960s that converts printed text into a tactile vibrating pattern that can be read with the fingertip. The Opticon uses a small camera to scan printed characters and reproduces them as patterns of vibrating…

Option Repertoire

A type of technology repertoire where a person has multiple tools that can each independently address the same access barrier, choosing between them based on context. For example, a person might use fidget toys, background music, or noise-canceling headphones to manage sensory…

OrCam(also: OrCam MyEye, OrCam Read)

A family of wearable assistive devices made by OrCam Technologies that use a camera and on-device AI to read printed text aloud, identify faces and products, and recognize colors and banknotes for blind and low vision users. The flagship OrCam MyEye clips magnetically to the arm…

Orca(also: GNOME Orca)

A free, open source screen reader for the GNOME desktop environment on Linux and Unix-like operating systems. Orca provides access to graphical applications through speech synthesis, braille output, and magnification. It uses the AT-SPI (Assistive Technology Service Provider…

Orientation and mobility(also: O&M)

A professional discipline and set of skills that enable people with visual impairments to travel safely and independently through their environment. Orientation refers to understanding one's position relative to the surrounding environment using sensory cues, landmarks, and…

Orthosis(also: Orthotic, Orthotic Device, Brace)

An externally applied medical device used to modify the structural and functional characteristics of the neuromuscular and skeletal system. Orthoses support, align, prevent, or correct deformities and improve the function of movable parts of the body. Common types include ankle…

Orthotics(also: Orthosis, Orthoses, Orthotic Device)

Externally applied devices used to modify the structural and functional characteristics of the neuromuscular and skeletal systems — including braces, splints, and supports for the spine, limbs, hands, feet, and neck. Orthoses stabilize joints, correct alignment, redistribute…

Overlap Error(also: Key Overlap Error, Simultaneous Key Press Error)

A typing error that occurs when two keys are pressed down at the same time, typically when a finger accidentally activates an adjacent key while moving toward the intended key, or when a user's hand rests on a key unintentionally. Overlap errors are particularly common among…

P300(also: P3, P300 Component, P3b)

The P300 is an event-related potential (ERP) component — a positive voltage deflection in EEG brain signals that peaks approximately 300 milliseconds after a person perceives a rare or task-relevant stimulus among frequent non-target stimuli. It is named for its polarity…

PC-Talker(also: PCTalker)

A Windows screen reader developed by the Japanese company KGS Corporation, widely used by blind and low-vision users in Japan. PC-Talker provides speech output for Windows applications and the web and integrates with the companion Net Reader Neo browser tailored to…

PDF Remediation(also: PDF Tagging, PDF Accessibility Remediation, Document Remediation)

The process of adding structural tags to an existing PDF document to make it accessible to assistive technologies such as screen readers. Remediation involves identifying logical content elements (headings, paragraphs, lists, tables, images), assigning appropriate tags,…

PHANTOM(also: PHANTOM Omni, PHANTOM Desktop, SensAble PHANTOM)

A family of force-feedback haptic devices originally developed by SensAble Technologies (now part of 3D Systems). PHANTOM devices use a pen-like stylus that users grasp while motors apply forces to create the sensation of touching virtual objects or being guided along…

PS5 Access Controller(also: PlayStation Access Controller, Access Controller)

Sony's highly customisable controller for PlayStation 5, released in 2023 and designed for players with limited motor control. It has a flat disc layout with interchangeable button caps and analog stick attachments, 3.5 mm expansion ports for external switches, and…

Pacing Aid(also: Pacing System, Time Management Aid)

An assistive technology that helps individuals with cognitive impairments manage the timing and sequence of activities in daily routines. Pacing aids provide cues — visual, auditory, or tactile — to indicate whether the user is on schedule, ahead, or behind, without requiring…

Page Magnification(also: Page Zoom, Web Page Magnification)

An accessibility feature that enlarges the entire visual presentation of a web page, including text, images, and layout elements, to make content easier to see for people with low vision or visual fatigue. Unlike text-only size increases, page magnification scales all page…

Page Turner(also: Page Turning Aid)

Any device, tool, or person that assists a musician in turning the pages of a music score during performance. Traditional page turners are human assistants who sit beside a musician and turn pages on cue. Technological alternatives include Bluetooth foot pedals for digital…

Panning(also: Screen Panning, Viewport Panning)

The act of moving the visible area of a screen magnifier or viewport across a webpage or application to view content that extends beyond the currently displayed portion. For screen-magnifier users, panning is a fundamental but often arduous interaction technique, requiring…

Pantograph(also: Haptic Pantograph)

A haptic input device that allows users to explore a two-dimensional surface by physically moving a stylus or finger pad across an exploration area, while receiving tactile feedback from an attached tactile display. In accessibility applications, the pantograph enables people…

Paradox of the Active User

The Paradox of the Active User, identified by Carroll and Rosson (1987), refers to the observation that computer users systematically avoid investing time in learning more efficient tools or methods, even when doing so would yield significant long-term productivity gains. Users…

Parallax(also: Visual Parallax, Binocular Parallax)

Parallax is the apparent displacement or difference in position of an object when viewed from two different vantage points. In human vision, binocular parallax — the slight difference between the images seen by each eye due to their spatial separation — is a primary cue for…

Parametric design(also: Parametric modeling)

A design approach in which objects are defined by adjustable parameters (dimensions, angles, ratios) rather than direct geometric manipulation, allowing users to customize designs by changing numerical values without needing 3D modeling expertise. Parametric design is…

Passive Infrared Sensor(also: PIR Sensor, PIR, Motion Sensor)

A passive infrared sensor detects movement by measuring changes in ambient infrared radiation in its field of view — typically body heat from a person moving across the detection zone. PIR sensors are inexpensive, low-power, and require no active emission, which makes them a…

Passive Pin Retention

A mechanical technique used in refreshable Braille display design where pins are held in their raised or lowered positions by a passive mechanical structure rather than by continuously powered actuators. In traditional Braille displays, each pin requires its own actuator to…

Passive Sensing(also: Passive Monitoring, Ambient Sensing)

The collection of behavioral and physiological data through sensors without requiring active user input. In mental health contexts, passive sensing uses smartphone sensors (GPS, accelerometer, microphone), wearable devices (heart rate monitors, electrodermal activity sensors),…

Passive notification(also: Automatic notification, Push notification)

Information delivered to a user automatically without requiring active input, triggered by context such as location, time, or system state. In assistive navigation for people with visual impairments, passive notifications are preferred because users' hands and attention are…

Pedestrian Dead Reckoning(also: PDR, Inertial Navigation)

A localization technique that estimates a pedestrian's position by tracking their movement from a known starting point using inertial sensors (accelerometers and gyroscopes) found in smartphones. The accelerometer detects individual steps through peak detection, while the…

Pedestrian Detection(also: Person Detection, Human Detection)

A computer vision task that identifies and locates people in images or video frames, typically using deep learning models such as convolutional neural networks. In accessibility applications, pedestrian detection is used in wearable assistive technologies for blind and low…

Pedestrian Navigation System(also: Pedestrian GPS, Walking Navigation)

A navigation system designed specifically for people travelling on foot, as opposed to systems designed for car drivers. Pedestrian navigation systems must account for footpaths, crosswalks, stairs, pedestrian bridges, and indoor routes that vehicle-focused systems typically…

Peltier Module(also: Peltier Device, Thermoelectric Module, TEC Module)

A Peltier module is a thermoelectric device that creates a temperature difference when electrical current is applied, with one side heating up and the other cooling down. In assistive technology, flexible Peltier modules are used to provide thermotactile feedback — controlled…

Pen-based Interface(also: Stylus Interface, Pen Computing, Digital Pen Interface)

A computer interaction method that uses a stylus or digital pen as the primary input device, typically in combination with a graphics tablet or touchscreen. Pen-based interfaces can support handwriting recognition, gesture commands, and direct manipulation of on-screen objects.…

People with Severe Motor Disabilities(also: PSMD)

A term used in assistive technology and human-robot interaction research to describe individuals whose motor impairments are severe enough that they cannot reliably use their hands or arms for everyday tasks, and who therefore depend on hands-free control modalities such as eye…

Perceptual Bandwidth(also: Sensory Bandwidth, Information Bandwidth)

Perceptual bandwidth refers to the rate at which a sensory channel can transmit information to the brain. In accessibility contexts, the concept highlights the fundamental asymmetry between vision and hearing: vision has extremely high bandwidth, allowing a sighted person to…

Perceptual Computing(also: Perceptual Intelligence)

A computing paradigm in which systems use sensors such as cameras, microphones, and motion detectors to perceive and interpret human behaviour, including gestures, facial expressions, speech, and body movement. In accessibility contexts, perceptual computing enables interfaces…

Perceptual User Interface(also: PUI, Natural User Interface)

A human-computer interaction paradigm that uses natural human capabilities such as vision, speech, gestures, and body movement as input modalities rather than relying on traditional devices like keyboards and mice. Perceptual user interfaces leverage sensors and computer vision…

Perkins Brailler(also: Brailler, Braille Writer)

A mechanical device for writing braille, manufactured by the Perkins School for the Blind since 1951. The Perkins Brailler has six keys corresponding to the six dots of a braille cell, a space bar, a backspace key, and a line advance key, allowing users to emboss braille…

Person-Technology Match(also: PTM, Matching Person and Technology)

A systematic approach to selecting assistive technology by evaluating the fit between a person's specific abilities, needs, preferences, and environment and the features and demands of available technologies. The person-technology match process recognizes that the most…

Personal Assistant(also: Virtual Assistant, Digital Assistant, Voice Assistant)

A software agent that can perform tasks or provide services based on user commands or queries, typically through voice interaction. Popular examples include Amazon Alexa, Google Assistant, Apple Siri, and Microsoft Cortana, often embedded in smart speakers, smartphones, and…

Personal Digital Assistant(also: PDA, Handheld Computer, Pocket PC)

A portable handheld computing device popular in the late 1990s and early 2000s that combined features like a calendar, contacts, note-taking, and basic application support in a pocket-sized form factor with a touchscreen interface. In accessibility research, PDAs like the iPAQ…

Personal Object Recognizer(also: Teachable Object Recognizer, Custom Object Classifier)

A computer vision system that allows individual users to train their own object recognition models by providing a small number of example photos and custom labels. Unlike generic object recognizers that use pre-defined categories, personal object recognizers let users define…

Personal Safety Management(also: PSM)

Personal Safety Management refers to the informed, agential, and proactive participation of an individual in maintaining their own physical safety. Coined in accessibility research by Branham et al. (2017), the concept highlights how people with disabilities — particularly those…

Personal Voice(also: Voice Banking, AI Voice Clone)

A technology that creates a synthetic replica of a person's voice from recorded speech samples, enabling text-to-speech output that sounds like the individual rather than a generic electronic voice. Apple's Personal Voice feature (iOS 17+) allows users to train an AI model of…

Personal emergency response system(also: PERS, PER system, Medical alert system)

A device, typically a wearable pendant or wristband with a button, that allows a person to summon help in an emergency. Despite being the mainstream solution for older adults living alone, PERS devices suffer from poor adoption: users forget to wear them, find them stigmatizing,…