Optophone

The optophone is a device, used by people who are blind, that scans text and generates time-varying chords of tones to identify letters. It is one of the earliest known applications of sonification. Dr. Edmund Fournier d'Albe of Birmingham University invented the optophone in 1913,^[1] which used selenium photosensors to detect black print and convert it into an audible output which could be interpreted by a blind person. The Glasgow company, Barr and Stroud, participated in improving the resolution and usability of the instrument.^[2]

Detail view of the optophone

Only a few units were built and reading was initially exceedingly slow; a demonstration at the 1918 Exhibition involved Mary Jameson reading at one word per minute.^[3] Later models of the Optophone allowed speeds of up to 60 words per minute, though only some subjects are able to achieve this rate.^[4]

Tone generating method of the FM-SLIT reading machine (above), and Frequency-time plot of its output (below).

See also

• Optacon