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The world's first mechanical television system


Jay Sadie:
[float=left][smg id=404 width=200][/float]German engineering student, Paul Gottlieb Nipkow proposed and patented the world's first mechanical television system in 1884. Paul Nipkow devised the notion of dissecting the image and transmitting it sequentially. To do this he designed the first television scanning device. Paul Nipkow was the first person to discover television's scanning principle, in which the light intensities of small portions of an image are successively analyzed and transmitted.

While some nineteenth century scientists, such as Guglielmo Marconi, concentrated upon transmitting audio signals, Nipkow was interested in the notion of transmitting a visual signal. At the young age of 23, he proposed a method that was capable of the task and received a patent for his invention. What Nipkow referred to as an electric telescope, was actually the forerunner of modern television. The innovative system was based upon a simple device known as the Nipkow disk.

In 1873, the photoconductive properties of the element selenium were discovered, the fact that selenium's electrical conduction varied with the amount of illumination it received. Paul Nipkow created a rotating scanning disk camera called the Nipkow disk, a device for picture analyzation that consisted of a rapidly rotating disk placed between a scene and a light sensitive selenium element. The image had only 18 lines of resoution.

[float=right][smg id=405 width=500 caption="The Nipkow Disk"][/float]According to R. J. Reiman author of Who Invented Television: The Nipkow disk was a rotating disk with holes arranged in a spiral around its edge. Light passing through the holes as the disk rotated produced a rectangular scanning pattern or raster which could be used to either generate an electrical signal from the scene for transmitting or to produce an image from the signal at the receiver. As the disk rotated, the image was scanned by the perforations in the disk, and light from different portions of it passed to a selenium photocell. The number of scanned lines was equal to the number of perforations and each rotation of the disk produced a television frame. In the receiver, the brightness of the light source would be varied by the signal voltage. Again, the light passed through a synchronously rotating perforated disk and formed a raster on the projection screen. Mechanical viewers had the serious limitation of resolution and brightness.

Nipkow once used his device to transmit a visual image from London to Paris, but the system was never developed for commercial use. Ironically, at the time, investors could not foresee a practical use for it, and therefore, Nipkow received little recognition during his lifetime for the feat. He spent most of his life as a railway engineer and died in Berlin, Germany on August 24, 1940. However, Nipkow paved the way for future developments in television and the horizontal-scanning method he first conceived continues to be an essential element in modern-day electronics.

No one is sure if Paul Nipkow actually built a working prototype of his television system. It would take the development of the amplification tube in 1907 before the Nipkow Disk could become practical. All mechanical television systems were outmoded in 1934 by electronic television systems.

Despite the fact that the Nipkow disk was never used for television, the disk is currently used extensively in reflected light confocal scanning microscopy to produce images that can be viewed in real time through the microscope eyepieces.


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