evolution of computer

evolution of computer

The Origins of Television

Inventors conceived the idea of television long before the technology to create it appeared. Early pioneers speculated that if audio waves could be separated from the electromagnetic spectrum to create radio, so too could television waves be separated to transmit visual images. As early as 1876, Boston civil servant George Carey envisioned complete television systems, putting forward drawings for a “selenium camera” that would enable people to “see by electricity” a year later.“Visionary Period, 1880’s Through 1920’s,” Federal Communications Commission, November 21, 2005, http://www.fcc.gov/omd/history/tv/1880-1929.html

During the late 1800s, several technological developments set the stage for television. The invention of the cathode ray tube (CRT) by German physicist Karl Ferdinand Braun in 1897 played a vital role as the forerunner of the television picture tube. Initially created as a scanning device known as the cathode ray oscilloscope, the CRT effectively combined the principles of the camera and electricity. It had a florescent screen that emitted a visible light (in the form of images) when struck by a beam of electrons. The other key invention during the 1880s was the mechanical scanner system. Created by German inventor Paul Nipkow, the scanning disk was a large, flat metal disk with a series of small perforations arranged in a spiral pattern. As the disk rotated, light passed through the holes, separating pictures into pinpoints of light that could be transmitted as a series of electronic lines. The number of scanned lines equaled the number of perforations, and each rotation of the disk produced a television frame. Nipkow’s mechanical disk served as the foundation for experiments on the transmission of visual images for several decades.

In 1907, Russian scientist Boris Rosing used both the CRT and the mechanical scanner system in an experimental television system. With the CRT in the receiver, he used focused electron beams to display images, transmitting crude geometrical patterns onto the television screen. The mechanical disk system was used as a camera, creating a primitive television system.