Paul Nipkow

Inventor of mechanical television

Paul Gottlieb Nipkow

(1860-1940) was a german physicist who pioneered television. Nipkow noticed that the metal Selenium had a special ability: its conductivity depended on light. Perhaps this could be used to convert an image to electricity? December 1883 he found a way to send a moving picture by wire; television was born.

But how did he manage to squeeze images through an electrical cord? Let's take a short look at two inventions that preceded it: telegraph and telephone.

Optical telegraphs

has existed since the dawn of mankind, smokesignals a primitive, local telegraph. Waving flags are also an ancient invention. However, a modern non-electrical system was invented in 1794. It had some severe limitations as the optical sensor was the human eye. Thus its speed was not the speed of light, but of human vision. But with the aid of the newly discovered telescope it was still an obvious improvement and could span a great distance quickly. Their were used almost a century.

The electrical equivalent appeared in 1852 as a quite simple yet efficient device. If letters, numbers and other characters are translated to a simpler trinary alphabet (consisting of 'dot', 'line' or 'nothing'), then it is quite easy to transmit a sentence, turning the current on and off repeatedly. The telegraph is essentially a digital system. Its elements simple but numerous. Read more...

The telephone

faces a harder problem, because sound has to be transmitted in realtime. Furthermore sound is a much more complex datatype than text. An italian inventor Antonio Meucci solved that problem in 1849 by utilizing an analog device, capable of transmitting the dual aspects of sound (quality and quantity = what kind and how loud). The telegraph need only concern itself about detecting whether the current is on or off. The telephone needs both amplitude and frequency. It also incorporates the invention of a microphone and a loudspeaker. Meucci called his invention "teletrophone". It had a good fidelity, but a very weak signal. Read more...

Television

is actually a misleading name, since it omits the aspect of sound. A stream of images quickly becomes nonsense without any speech (or at least some text). But the omission is understandable. The telephone already existed and only needed to be syncronized with television. But transmitting a live image is much more difficult than text or sound. Sound is a 1 dimensional problem, even though the technical solution faces two aspects. Any image is 2 dimensional. Add time and we have a 3-dimensional puzzle to solve. (Colours would be nice too, as reality is seldom black/white/grey.)

The challenge:

How does an electrical cord with 1 dimension provide a solution to this triple challenge? Nipkow combined elements from both telegraph and telephone. First the images is broken down in bits (the digital part). But each bit contains a continuum of values, ranging from pitchdark to bright light (the analog aspect). The ingenious device that did all this is a simple disc known as 'Nipkows disc'.)

Nipkows disc:

The disc has a spiral of holes cut into it, positioned so they scan every part of an image in turn as the disc revolves. Light from each point turns into an electrical current. This electrical signal lights up a second light at the other end of the wire. This light flickers because the amount of current it receives depends on the brightness of the image being scanned. Light from this bulb passes through a second disc spinning at the same speed, then projects the picture onto a screen.

Later:

Nipkows original system had some severe limitations. It offered only 18 lines of resolution, and it wasn't much sensitive to light. However, he lived to see the modern electronic version developed, so television could be done without the mechanical disc.

Worlds first official and regular television started in Berlin 1935. But BBC broadcasted daily scheduled television programs from 1929 until 1939 when the outbreak of war end their transmissions. 1936 saw rhe first commercial television broadcast by BBC, and the Olympic Games is broadcast for the first time in Germany. Then WW2 arrived. Had it not been for the war, modern television could have started as early as the 1940'ies...

Now:

Nipkows disc was long ago abandoned by television, but has recently resurfaced in modern microscopy (in an amplified version). Read more...

Paper version A4: pdf / word