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Optical sound is a means of storing sound recordings on transparent film. The technology was first developed in the 1920s as a sound-on-film format for motion pictures, eventually superseding all of other sound film technologies until the advent of digital sound would become the standard in cinema projection booths. Optical sound has also been used for multitrack recording and for creating effects in some musical synthesizers. ==Naval use prior to motion pictures: 1914-21== Optical sound was first developed by several inventors with an interest in wireless telegraphy through transmission of light, primarily for ship-to-ship communications. The idea was that sound pulses could be electrically converted into light pulses, beamed out from one ship and picked up by another, where the light pulses would then be re-converted back into sound. A pioneer in this technology was American physicist Theodore Case. While studying at Yale, Case became interested in using modulated light as a means to transmit and record speech. In 1914, he opened the Case Research Lab to experiment with the photo-electric properties of various materials, leading to the development of the Thallofide (short for thallium oxysulfide), 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. Case and Sponable's system was first tested off the shores of New Jersey in 1917, and attending the test was Thomas Edison, contracted by the Navy to evaluate new technologies. The test was a success, and the U.S. Navy used the system during and after World War I. Contemporary to the work of Case and Sponible was Charles A. Hoxie's Pallophotophone (from Greek, meaning "shaking light sound"), manufactured by General Electric (GE). Similar to Case's infrared system used by the Navy, the Pallophotophone was also intended for transoceanic wireless telegraphy, but was then adapted for recording speech. With GE's backing, Hoxie's invention was used in 1921 to record President Calvin Coolidge and others for radio broadcasts. Case, Sponible and Hoxie's work all became instrumental to the development of sound-on-film in the years following World War I. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Optical sound」の詳細全文を読む スポンサード リンク
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