May 6, 1920] 



NATURE 



295 



The Optophone: An Instrument for Reading by Ear. 



By Dr. E. E. Fournier d'Albe. 



THE type-reading optophone, an instrument 

 designed to enable blind people to r^ad 

 ordinary print, was described in Nature in 1914 

 (vol. xciv., p. 4). At the British Scientific Pro- 

 ducts Exhibition of 1918 some public reading 

 demonstrations were given with a somewhat 

 improved apparatus exhibited by the writer and 

 by Mr. W. Forster Brown (see Nature, vol. cii., 

 p^ 10, September 5, igi8). These demonstrations 

 sufficed to show that all the essential problems 

 of type-reading had been solved, but the instru- 

 ment then exhibited had certain defects which 

 militated against its prolonged and convenient use 

 by blind persons. Thus, the displacement along 

 the Hne of type was effected by turning a handle, 

 which no blind person would care to use by the 

 hour. The construction of the apparatus generally 

 was not sufficiently solid and substantial, in view 

 of the fact that it had to be put into the hands of 

 a necessarily somewhat clumsy operator. 



After the close of the exhibition the construc- 

 tion of the instrument was undertaken by Messrs. 

 Barr and Stroud, Ltd., of Glasgow, the well- 

 known makers of range-finders and fire-control 

 apparatus for the British and foreign navies. A 

 great deal of thought and care has been bestowed 

 upon the instrument by Dr. Archibald Barr, and 

 the result has been a thoroughly sound, compact, 

 and practical instrument, such as was shown by 

 Dr. Barr in his lecture to the Royal Philosophical 

 Society of Glasgow on March 24 last. 



The general principle of the apparatus is shown 

 by Fig. 1. A siren disc, D, is run at about 

 30 revolutions a second by means of the small 

 magneto-electric motor shown. It contains five 

 circles of square perforations, the innermost circle 

 having twenty-four perforations, the outermost 

 forty-two, the other circles being intermediate 

 and corresponding to the relative frequencies of 

 certain notes of the diatonic scale. A line of 

 light in a radial direction is provided by the 

 festoon lamp L, and the image of the filament of 

 this lamp is thrown upon the print by a system 

 of three lenses on the other side of the selenium 

 tablet S. The axis of the concavo-convex lens C 

 is slightly tilted out of the axis of the other lenses 

 for a purpose which is specified below. The 

 general result of the optical system is to give a 

 line of luminous dots on the print, each dot having 

 a different musical frequency. The light con- 

 stituting these dots is diffusely reflected back on 

 to the selenium, which is put in circuit with a 

 battery and a high-resistance telephone receiver. 

 Those dots which fall on white paper produce a 

 note of their own musical frequency in the tele- 

 phone, while those which fall on black are extin- 

 guished. We thus get what may be called a 

 "white-sounding" optophone, in which the black 

 letters are read by the notes omitted from he 

 NO. 2636, VOL. 105] 



scale rather than by the notes which remain sound- 

 ing. All the reading demonstrations hitherto 

 undertaken have been given with a "white-sound- 

 ing " optophone. 



A modification of this principle, introduced by 

 Messrs. Barr and Stroud in consultation with tfie 

 writer, is the provision of a second selenium 

 preparation in the form of a cylindrical rod, the 

 top of which can be seen at B (Fig. i). This rod 

 receives the light reflected by the concave surface 

 of the lens C, which produces a real image of the 

 line of dots on a generator of the cylindrical rod, 

 and by turning this rod about its axis the image 

 can be made more or less effective as desired. 

 By balancing the effect on B against the effect 

 on S, when white paper alone is exposed, a silence 

 can be produced in the telephone, and the effect 

 of the passage of a black letter is to make a sound 

 which varies in accordance with the formation of 

 the letter. This is the principle of what may be 

 called a " black-sounding " optophone, and 



Fit;. I. — Skeleton apparatus showing the principle of the optophone. 



although its advantage over the white-sounding 

 type has yet to be proved, there is little doubt 

 that the learning of the alphabet sounded on the 

 new principle will be easier, though in the writer's 

 opinion the ultimate speed acquired by either black- 

 sounding or white-sounding will be approximately 

 the same. It is interesting in this connection to 

 note that Miss Mary Jameson, the blind girl who 

 gave the demonstrations at the 1918 Exhibition, 

 now reads habitually at a speed of about twenty- 

 five words a minute with a " white-sounding " 

 optophone made by Messrs. Barr and Stroud, and 

 finds, indeed, that when the instrument is adjusted 

 for a lesser speed reading becomes more difficult. 



The present construction adopted by Messrs. 

 Barr and Stroud is shown in Fig. 2. The disc, 

 lamp, lenses, and selenium, as well as the motor, 

 are all mounted in the swinging "tracer," which 



