Assistive Technologies for the Blind

Technology for Reading, Writing, and Note Taking

For straightforward text, reading machines and optical character recognition software (available in both desktop and handheld units) can scan printed material and read it aloud in artificial (“synthetic”) [Page 65]speech. Audio recordings from the National Library Service and other sources provide access to many publications. These “talking books” are now available on CDs and other digital media. The National Federation of the Blind provides a service giving access to spoken versions of newspapers and magazines, downloaded via telephone, with sections and articles selected via touch-tone commands.

Braille, a tactile code using raised dots for letters and numbers, is used for reading and writing by blind individuals. A simple stylus is often used to punch raised dots into paper for short notes and labels, but Braille translation software and printers (“embossers”) for computer output are now commonplace. Mechanical and electronic Braillers are also available, with a Braille keyboard (six keys corresponding to the dots in a Braille character, and a space bar) coupled to a print head that embosses the Braille characters on paper. Electronic “refreshable” Braille displays mechanically present a line of Braille characters that are replaced by the next line when the reader activates a control switch. These are used for displaying computer output and for compact personal Braille notetak-ers, which provide much of the functionality that a notebook computer does for the sighted.

For an individual with low vision, some books are available in large print, and individuals can readily produce their own large print text using a computer. The inverse of the Snellen acuity fraction approximates the magnification needed to read small print. For example, someone with 20/60 acuity is likely to need 60/20 = 3 times magnification for normal reading. For this amount of magnification, common optical magnifiers (available with built-in illumination) will suffice. “Reading telescopes” attached to spectacle frames facilitate comfortable posture, farther away from the reading material. A strong positive spectacle lens or “add” focused an inch or two away from the face gives 8 to 16 times magnification compared with a normal reading distance of 16 inches. Even larger magnifications (as much as about 60) can be obtained with closed-circuit television (CCTV) magnifiers that display a magnified video image on a television-type monitor. (At high magnifications, only two or three letters may be visible at a time, slowing reading and making scanning more difficult). Writing materials can also be placed under the unit's camera. The advent of liquid crystal displays (LCDs) has produced handheld versions with a miniature camera underneath an inch-thick screen measuring about 6 by 3 inches, providing as much as 10 to 12 times magnification with a larger field of view than an optical magnifier. Most electronic magnifiers offer a contrast reversal option (i.e., displaying white print on a dark background), which can reduce glare. Some can be mounted on the head, or used for reading text at both near and far (e.g., the blackboard in a classroom).

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