Optical sound
Building on the principle first demonstrated by the Photophone of Alexander Graham Bell in 1880, optical sound was developed by several inventors with an interest in wireless communication through transmission of light, primarily for ship-to-ship use.
In 1914, he opened the Case Research Lab to experiment with the photoelectric properties of various materials, leading to the development of the Thallofide (short for thallium oxysulfide) Cell, a light-sensitive vacuum tube.
The Thallofide tube was originally used by the United States Navy in a top secret ship-to-ship infrared signaling system developed at Case's lab with his assistant Earl Sponable.
[1] Contemporary with the work of Case and Sponable was Charles A. Hoxie's Pallophotophone (from Greek roots meaning "shaking light sound"), manufactured by General Electric (GE).
Most of the inventions which led to optical sound-on-film technology employed the use of an electric lamp, called an 'exciter', shining through a translucent waveform printed on the edge of a film strip.
A fourth major contender for the sound film market - Warner Brothers' Vitaphone sound-on-disc system which synchronized large-size (16") phonographic records with a film's projector was used on early talkies, such as their' 1927 hit The Jazz Singer (which was marketed as being "all singing" though the talking was sporadic, used in only several isolated sequences), utilized Vitaphone discs, but by 1931, optical sound-on-film would supplant the separate sound-on-disc technology.
After the war, Theodore Case and Earl I. Sponable collaborated with fellow wireless communications pioneer Lee de Forest, inventor of the Audion tube, to apply their optical sound system to motion pictures.
[citation needed] There, he met Finnish inventor, Eric Tigerstedt ("Finland's Thomas Edison"), who improved Phonofilm's amplification system to be audible in a large theater.
Phonofilm was used mainly to record stage performances, speeches, and musical acts in and around New York City, but Hollywood movie studios expressed little interest in the system.
[2] In August 1926, Warner Brothers introduced their Vitaphone sound-on-disc system, developed by Western Electric, with the John Barrymore film Don Juan.
Case and Sponable went on to implement their optical sound-on-film innovations as the Movietone sound system, and the UK rights to Phonofilm were bought up by theater chain owner Isadore Schlesinger, who used the technology to release short films of British music hall performers through 1929.
While Lee de Forest struggled to market Phonofilm, Charles A. Hoxie's Pallophotophone had success as an optical recording device through the support of General Electric.
By the mid-1920s, GE adapted Hoxie's invention for motion picture sound playback, subsequently marketed as a commercial product by then-GE subsidiary RCA as the 'RCA Photophone'.
After 1931, Fox's feature film production moved to a two-machine system which Western Electric had developed from the RCA Photophone, with the advent of a light-valve invented by Edward C. Wente.
This continued until 1976, by which time optical sound recording had been converted to the Western Electric (dubbed "Westrex") stereo variable-area system.
As an early cinematic surround sound system, Disney had to refit each theatre with special Fantasound equipment that was later dismantled and put toward the war effort.
In 1971 toy manufacturer Mattel released the Optigan (short for optical organ), an organ-like synthesizer whose sound library was stored on interchangeable 12" clear acetate "program discs".
To the far left is the SDDS digital track (blue area to the left of the sprocket holes), then the Dolby Digital (grey area between the sprocket holes labeled with the Dolby "Double-D" logo in the middle), and to the right of the analog optical sound is the DTS time code (the dashed line to the far right.)
