A
refreshable Braille display or
Braille terminal is an electro-mechanical device for displaying
BrailleThe Braille system is a method that is widely used by blind people to read and write. Braille was devised in 1821 by Louis Braille, a blind Frenchman. Each Braille character or cell is made up of six dot positions, arranged in a rectangle containing two columns of three dots each...
characters, usually by means of raising dots through holes in a flat surface.
BlindBlindness is the condition of lacking visual perception due to physiological or neurological factors.Various scales have been developed to describe the extent of vision loss and define blindness...
computerA computer is a machine that manipulates data according to a set of instructions.Although mechanical examples of computers have existed through much of recorded human history, the first electronic computers were developed in the mid-20th century . These were the size of a large room, consuming as...
users, who cannot use a normal
computer monitorA monitor or display is a piece of electrical equipment which displays images generated by devices such as computers, without producing a permanent record. The monitor comprises the display device, circuitry, and an enclosure...
, use it to read text output. Speech synthesizers are also commonly used for the same task, and a blind user may switch between the two systems or use both at the same time depending on circumstances.
Because of the complexity of producing a reliable display that will cope with daily wear and tear, these displays are expensive.
A
refreshable Braille display or
Braille terminal is an electro-mechanical device for displaying
BrailleThe Braille system is a method that is widely used by blind people to read and write. Braille was devised in 1821 by Louis Braille, a blind Frenchman. Each Braille character or cell is made up of six dot positions, arranged in a rectangle containing two columns of three dots each...
characters, usually by means of raising dots through holes in a flat surface.
BlindBlindness is the condition of lacking visual perception due to physiological or neurological factors.Various scales have been developed to describe the extent of vision loss and define blindness...
computerA computer is a machine that manipulates data according to a set of instructions.Although mechanical examples of computers have existed through much of recorded human history, the first electronic computers were developed in the mid-20th century . These were the size of a large room, consuming as...
users, who cannot use a normal
computer monitorA monitor or display is a piece of electrical equipment which displays images generated by devices such as computers, without producing a permanent record. The monitor comprises the display device, circuitry, and an enclosure...
, use it to read text output. Speech synthesizers are also commonly used for the same task, and a blind user may switch between the two systems or use both at the same time depending on circumstances.
Because of the complexity of producing a reliable display that will cope with daily wear and tear, these displays are expensive. Usually, only 40 or 80 Braille cells are displayed. Models with 18-40 cells exist in some notetaker devices.
On some models the position of the
cursorIn computing, a cursor is an indicator used to show the position on a computer monitor or other display device that will respond to input from a text input or pointing device. The text cursor may be referred to as a caret in some cases. This term came about from older Unix systems that used the...
is represented by vibrating the dots, and some models have a switch associated with each cell to move the cursor to that cell directly.
The mechanism which raises the dots uses the piezo effect of some crystals, where they expand when a voltage is applied to them. Such a crystal is connected to a lever, which in turn raises the dot. There has to be a crystal for each dot of the display, i.e. eight per character.
The software that controls the display is called a
screen readerA screen reader is a software application that attempts to identify and interpret what is being displayed on the screen . This interpretation is then re-presented to the user with text-to-speech, sound icons, or a Braille output device...
. It gathers the content of the screen from the
operating systemAn operating system is an interface between hardware and user which is responsible for the management and coordination of activities and the sharing of the resources of the computer that acts as a host for computing applications run on the machine. As a host, one of the purposes of an operating...
, converts it into braille characters and sends it to the display. Screen readers for graphical operating systems are especially complex, because graphical elements like windows or slidebars have to be interpreted and described in text form. Modern operating systems usually have an
Application Programming InterfaceAn application programming interface is an interface in computer science that defines the ways by which an application program may request services from libraries and/or operating systems. An API determines the vocabulary and calling conventions the programmer should employ to use the services...
to help screen readers obtain this information, such as UI Automation (UIA) for Microsoft Windows or AT-SPI for GNOME.
A new development, called the rotating-wheel Braille display, was developed in 2000 by the
National Institute of Standards and TechnologyThe National Institute of Standards and Technology , known between 1901 and 1988 as the National Bureau of Standards , is a measurement standards laboratory which is a non-regulatory agency of the United States Department of Commerce...
(NIST) and although a second rotating display was designed at the
Leuven UniversityThe Katholieke Universiteit Leuven is the Flemish offshoot of the oldest university in the Low Countries which was originally founded in 1425 . Centrally located in the historic town of Leuven in Flanders, the K.U. Leuven is officially a Dutch-speaking institution. With 35,347 students in...
in Belgium both wheels are still in the process of commercialization. Braille dots are put on the edge of a spinning
wheelA wheel is a circular device that is capable of rotating on its axis, facilitating movement or transportation whilst supporting a load , or performing labour in machines. Common examples are found in transport applications. A wheel, together with an axle overcomes friction by facilitating motion by...
, which allows the user to read continuously with a stationary finger while the wheel spins at a selected speed. The Braille dots are set in a simple scanning-style fashion as the dots on the wheel spins past a stationary
actuatorAn actuator is a mechanical device for moving or controlling a mechanism or system. An actuator typically is a mechanical device that takes energy, usually created by air, electricity, or liquid, and converts that into some kind of motion....
that sets the Braille characters. As a result, manufacturing complexity is greatly reduced and rotating-wheel Braille displays, when in actual production, should be less expensive than traditional Braille displays.
History
The base of a refreshable braille display is a pure braille terminal. There, the input is performed by two sets of three keys plus a space bar (as in the
Perkins BraillerThe Perkins Brailler is a simple machine used to write braille. The Perkins Brailler is a "braille typewriter" with a key corresponding to each of the six dots of the braille code. By simultaneously pressing different combinations of the six keys, users can create any of the characters in the...
), while output is via a refreshable braille display consisting of a row of electromechanical character cells, each of which can raise or lower a combination of six (or in some cases, eight) round-tipped pins. Other variants exist that use a conventional
QWERTYQWERTY is the most used modern-day keyboard layout on English-language computer and typewriter keyboards. It takes its name from the first six characters seen in the far left of the keyboard's top row of letters...
keyboard for input and braille pins for output, as well as input-only and output-only devices. In 1951, David Abraham, a woodworking teacher at Perkins, created a portable braille terminal.
Braille computer monitor
The Braille computer monitor has rows and columns of rectangular cells. The cells include four rows and two columns of dots that can be felt for interpretation by the user. "The pins are driven by electromechanical impact drivers and are held in position by resilient elastomeric cords. The impact drivers are carried on a bi-directional printhead which travels beneath the movable pins. An erasing mechanism is provided to positively drive the pins downwardly to erase the characters produced by the printhead."
The Braille computer monitor is under the United States Patent 6700553.
External links