Mechanical Television primer

[albert]

Hi!- My name is Albert and I have been invited over to this forum by my friend Wolfgang Mayer.

While watching his incredible home cinema with all the latest technology some days ago, we thought it would be interesting to think back to how it all started in the 1920s.

So many things we take for granted today were the result of much headache, suffering and heartburn by the intrepid inventors who dedicated their lives to the idea of “seeing by wireless” or “radiovision” as the early experiments were called.
I am by no means a historian of television, but I love  to build things. So I started to research the early days with the idea to follow in the footsteps of the pioneers. I will try to let you follow this adventure.

Early television was a mechanical system. Before you laugh: Today’s sophisticated high end video projectors are full of mechanical parts. The creation of color images  with a black and white DMD device makes use of the idea of the color wheel, projecting the base colors in sequence. The ultra miniaturized DMD device is itself a mechanical system for switching single pixels.

It all started in 1883 when a young German student named PAUL NIPKOW sat in his little flat in Berlin around Christmas time and longed to see his family and parents back in Pomerania, where he came from. A train ticket was too expensive for him, and so he sat down and conceived a method to transmit images on a telegraph line.


He came up with the idea of  a fast-rotating disc with a series of holes punched into it. These holes were arranged in a spiral shape. A small window of the disc would be the scanning area. One hole in the disc traverses this window. As it exits the other side, the next hole moves across, but one hole diameter further to the inside of the disc. This way a scanning motion is imparted. the idea was so good it shaped the research and development of TV up until the 1930s when the first purely electronic tv systems started to emerge.



Young Nipkow patented his system as “electrical telescope” in 1883. But his invention came too early: Crucial parts of the system did not yet exist.  There had to be a way to capture the light across the Nipkow disc, and to amplify the very small currents created by the incoming beam of light . The photoelectric cell using selenium as the light sensitive element was still a very new invention, and in 1883 there was no way to amplify its signal. The patent proposes a clever controllable light source but at the time thiscould not be realized. So  Nipkow never made a dime from his invention.

[MrPixels]

Welcome to the forum Albert, very informative first post. Until now I was not aware of this rotating disc and the technology behind it as well as its place in history. Thank you for explaining everything I am smarter for reading your post. I hope other others read and appreciate your knowledge.
Keep up the good work.

[w.mayer]

Nice to see you here Albert.

As we spoke this is all very interesting things and I am sure many people will love to read all this.
In many Forums there was something inside from it from time to time but not a whole  section so very good to have it now here.
May some day I can share something from the 1980 years where CRT Projection was the King.

Sad I still can not see the pictures but lets wait a bit may the forum need some time to make it visible.
Cant wait to hear more from it and may some day I can see this first steps in TV with my own eyes.

[donaldk]

Thank you Albert. May I point out Mark Schubin's work, he traces the history back to the Werner von Siemens Electronic Eye of 1876, the first publicly discussed/presented selenium opto-electrical visual sensor. William von Siemens his brother in London discussed it the next year 1877. Nipkow seems to be building on this, as were many others. The word/term Television was launched at the Paris World fair in 1900, according one of his presentations. If one want's to paint with a really wide brush, there was a 'camera' in the 5th century bc;-).

http://dci-forum.com/news/2/mark-schubin-tracing-concept-television-1877-1876-siemens-electric-eye/1660/msg2750#msg2750

[donaldk]

Just as an aside, about Wolfgang's lacking images remark. Albert I see you attached the images, can you upload images to the media gallery? I still can't. In the past i could, but since september I get the wrong filetype error (jpg), in August it started with having other errors. The attachments show fine here. The big disadvantage to using attachments is that they all get hung at the bottom of the article. They can not be  coupled to a particular part of the article, to illustrate the text. Using the media gallery one can, by using the img tags.

[w.mayer]

Now I can see this images.

Just watch the Videolink.
Very good.

[donaldk]

Wolfgang I don't see a video link, just images. Or do you mean Mark's presentation?

[albert]

Thank you all for the comments. I hope we can get a lively discussion here!

Of course there were other people - not just Paul Nipkow. We must also mention the fact that very early attempts to transmit still images had been made at the end of the 19th century. From this the whole line of "FAX" technology branched off- my "Brockhaus" dictionary from 1908 shows this image as  a result of "Bild-Telegrafie"- still image transmission. Not bad huh? The machines resembled an old Edison phonograph or a small lathe. But remember this could take 20 to 30 minutes for a still image, a far cry from transmitting moving images.

[albert]

Now, let’s jump forward to the 1920’s. By this time the  first radio stations had taken up regular broadcasting services on the shortwave band.
The first television pioneers succeeded in transmitting silhouette images of a cross or a pair of scissors, but no one had been able to transmit a greyscale image so far. Many countries had their TV pioneers, in France it was René Barthélemy, in the U.S. an inventor named Jenkins, and in Germany we had Manfred von Ardenne and the Hungarian Denes von Mihály.

[w.mayer]

I saw the Videolink you had post.

[donaldk]

Mark is a fine historian, and a true gentleman. His presentations have recuring themes, but they culminated in the linked article in IEEE Xplore. He also has done talks about how the opera was the first to use all modern communications technologies. Aswell as the inspiration for TV: http://www.sportsvideo.org/blogs/?blog=schubin-cafe&news=the-polish-polymath-who-came-up-with-television-for-opera-in-1878. Dating back 'cable' and Pay-Per-view/Hear to the 1800s. On more direct engineering there are issues of contrast/MTF and resolution. Check out http://www.schubincafe.com/category/schubin-cafe/.

Is he always that nice;-)...

From: Mark Schubin
Date: Mon, 12 Dec 2011 13:09:45 -0500
Well, as long as we're throwing in arcana, I am the person responsible for killing what I believe to have been the only actual ongoing 625/50 NTSC broadcasts (in Barbados). I got them to switch to 525/59.94 NTSC. The power on the island remains 50 Hz, so many older TVs needed power-supply filtering.<\q>

More goodies, like RCA's PAL pre-decessor CPA, Color Phase Alternation http://www.earlytelevision.org/rca_cpa_restoration.html. And a colourwheel based NTSC monitor: http://www.earlytelevision.org/dumont_monitor_restoration.html#feb2813.

There also has been a mechanical light valve projector back in 1936 that had a big wheel with mirrors, as well as a lightvalve showing lightvalve projectors are nothing new and pre-date or co-date CRT projectors;-).  Now where is that early technology site with chronoloical ordering of technologies when you need it.

[albert]

Thanks for the link to the Schubin video-if you have the time to watch it, by all means do so. He shows that television was a long standing dream like heavier-than-air flight. And like that it became a reality as soon as certain principal inventions had been made.

Scottish inventor JOHN LOGIE BAIRD was one of the dominating figures in 1920s television history. He came from nowhere and succeeded where others in well equipped labs had problems. He had enormous effects on the beginning of the tv industry. But he fell to the wayside when electronic television became available.
He was the typical “lone wolf” inventor, who, after being largely unsuccessful with his “Baird Undersocks” that were supposed to keep your feet warm in the rainy English winters, decided to throw himself at the burgeoning field of television. He was plagued with health problems  all his life, and the determination he showed was all the more remarkable. He tackled the problems without a budget and was forced to haunt the London surplus shops where army material from WW I was sold at low prices. Some of his Nipkow discs were made from old hatboxes and his motor came from a garage sale. But his contraptions worked.
Baird overcame the basic problem of the Nipkow disc when this system was used as a camera: Only 0.1 % of the light passes though the holes in the disc to the photo-electric cell. He made a “lens disc” from plywood where he inserted glass lenses (from bicycle headlights) into the disc to form an image. These discs could not rotate at very high speed - he had an accident where one of these discs shattered and threw shards of glass across the room- so he made a secondary disc that rotated at high speed to interrupt the light beams from the lens disc and create more “resolution”.
He needed so much light for his first experiments that he would set people’s hair on fire when they were “televised”. So he did his first experiments with the head of a ventriloquist’s doll affectionately named “Stooky Bill.” This subject never complained and his features could be delineated with black paint.
With this whirling noisy contraption that barely held together he could transmit a grey scale image of “Stooky Bill” in his  Soho flat from one room to the next. He agreed to show his machine at the London department store “Selfridge’s” because he would have starved otherwise.

[albert]

Let's stay a bit longer with John Logie Baird:

On January 26. 1926 about 50 scientists from the prestigious ROYAL INSTITUTION climbed to Baird's attic laboratory in London to witness the first transmission of a live tv image of a person's face. With this feat J.L. Baird made history- he is recognized now as being the first inventor whose system was able to transmit greyscale images - albeit in very low resolution. - 30 lines- and 12.5 images per second.

Feb. 08. 1928: Baird made history again by transmitting the first live tv images across the Atlantic Ocean.

Still in the year 1928, Baird showed a first primitive color TV system with a rotating color filter. This might be called the birth of color-sequential tv, a technique used today in most consumer video projectors.

From 1929 to 1935, the BBC showed  experimental television via shortwave radio. Baird developed a machine called the TELEVISOR - for wealthy customers- since at the time it was quite expensive.
But it could also be built from a kit by  tech-savvy radio amateurs. These were the first to be able to see regular television anyway, since the running of these machines was far from "you push the button, we do the rest".
Thanks to Baird and other pioneers,  TV had quickly become a commercial reality, and made it from wooden contraptions in labs to something that would not look out of place in a consumer household.
The image quality was still very poor, but at least recognizable faces and other detailed objects could be clearly seen on the tiny  area of the Nipkow disc.

[w.mayer]

I think the last picture show the 32 line TV right?
WOW what happen less than 100 years ago and think what we will have in 100 years from now!

[albert]

Hi Wolfgang!

The picture was photographed off the rotating disc and according to the caption it shows a business partner of J.L. Baird, Oliver Hutchinson.  So then this would be a 30 line image, the later NBTV "club" standard is 32 lines.
Apparently this picture accompanied the article in the "TIMES" about Baird's successful demonstration for the Royal Society in 1926. Source: The English Wikipedia article on JL Baird.
It is really staggering to think about the development of TV in the past 100 years. We should put one of the rotating disc machines next to your projector one day!