Non-electric Television.

Forum for discussion of narrow-bandwidth mechanical television

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Postby Stephen » Wed Apr 11, 2007 12:08 am

DrZarkov wrote:What did Baird not invent? :D

As I skim through Mr. Baird's patent portfolio, there seems to be little that he did not invent with respect to fundamental television technology! He has patents for embedded synchronisation signals and means for generating and utilising them, line interlacing of every imaginable sort, colour television of the dot-sequential, line sequential, and field sequential types, stereo television and even a multi-stack magnetic disc video recording system with multiple record/reproduce and erase heads. In most cases his proposals were 20 to 30 years ahead of the technology for making them commercially feasible.
Last edited by Stephen on Wed Apr 11, 2007 1:38 am, edited 1 time in total.
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Postby DrZarkov » Wed Apr 11, 2007 1:02 am

It is really a pity that he died so young. Who knows what he would have done if he had the time?
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Postby Andrew Davie » Wed Apr 11, 2007 1:10 am

DrZarkov wrote:It is really a pity that he died so young. Who knows what he would have done if he had the time?


He would have spent all his time watching TV, probably! :roll:
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Postby DrZarkov » Wed Apr 11, 2007 2:44 am

I don't think so. Farnswoth did not even had a TV at home in the 50th! And do we watch a lot of TV? (O.k., I watch every single episode of Doctor Who and "Life on Mars", but that's it.)
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Club Standard for Non-electric Television?

Postby Stephen » Wed Apr 11, 2007 3:54 am

I was just thinking that if this crazy scheme actually worked "narrow bandwidth" would have little meaning because the transmission is completely non-electric and entirely by way of optical fibre. Conceivably the optical scanning elements could produce any number of scanning lines with any number of frames per second up to the limits of what the hot air engines and mechanical governors could stand.

Would high definition non-electric television using 19th century technology be possible? That would be a real hoot. Probably not, but certainly a 48 or 60 line 24 or 48 fps standard might be within reach. Obviously there would be no need to synchronise frame rate to mains frequency.
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Film recording.

Postby Steve Anderson » Fri Apr 13, 2007 2:26 pm

It would also be possible to record and reproduce images non-electrically. Imagine that one end of the optical fibre extends to a photographic film strip recorder instead of a display. The end of the optical fibre then generates a variable density "video" track on the moving film strip. For reproduction, a light source such as an oil mantle lamp illuminates the developed video track on the moving film strip and one end of an optical fibre receives the modulated light. The other end of the optical fibre serves as the modulated light source in the display.


This is the very same idea that movie sound recording has been done for a long time, instead of varying the intensity of the light the width of the sound track(s) is modulated. Much the same as an AM transmitter, the light is the 'carrier', the sound is the information.

The sound information can be seen on the left of the attached pictures.

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Non-electric Television.

Postby Stephen » Sat Apr 14, 2007 4:42 am

Most of the original optical sound recording schemes actually used the variable density technique. In fact, Charles E. Fritts patented the variable density optical recording technique for sound in 1880.

Commercialisation of optical sound recording started in the 1920s with the introduction of sound tracks on motion picture film. Three of the four sound on film processes were variable density, that is, Western Electric, Phonofilm, and Movietone. The fourth was the RCA Photophone variable area recording process. Although it was initially inferior in quality to the variable density systems, it soon surpassed them and became the preferred system.

The reason for this is simple. Variable density optical tracks require accurate exposure and development times to secure the best dynamic range and signal to noise ratio. These times often are at odds with the best exposure and development times for the accompaning picture frames. Thus there is a compromise.

Variable area optical tracks do not require such accurate processing since there is no variation in density of the tracks. Thus, exposure and development times for best picture frame quality is possible with no loss of sound quality.

By the way, it is probably obvious, but I failed to mention that the proposed non-electric television system is inherently full colour, since the transmission is all optical. Of course, if one were to include the intermediate film process to increase transmission distance or increase display brightness, the film would have to be of the colour type or monochromatic film with a colour splitter and three side-by-side optical tracks, one for each colour.
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Postby Roland » Mon Apr 23, 2007 10:46 am

DrZarkov wrote:The best method would be a Stirling-engine (http://en.wikipedia.org/wiki/Stirling_engine) I think. There are small Stirling-engines available from several webshops. Not cheap, but safe ;-)


It just so happens that on Saturday I was at a small Model Engineering show and picked up a book entitlied:

"Building Stirling Engines without a Lathe", by Kjeld Hoejfeldt, published by Camden Miniature Steam Services.

This is a very interesting little book which shows how to build Stirling engines from junk - in fact they have a distinctly mechanical TV look about them - using parts of scrapped VCRs etc.

There were some homemade Stirling engines on show which worked quite well and also more professionally built units which generally started at over 100 GBP - though looking at one of the catalogues I picked up there is a starter kit listed at 34 GBP.

According to the book - 200 or even 300 RPM is quite possible on the homemade engines which implies gearing would be required to drive a Nipkow disk at a sensible speed. The professionally machined units/kits can manage 10 times that amount and conceivably might allow for higher FPS.

Thinking about actually producing a working TV system I would have though that a camera/monitor would be the simplest option - or maybe a close circuit system with 2 Nipkow disks driven from the same line shaft.

I may yet get to build a Stirling Engine - but in many respects the real acid test of this system is not concerning the motor drive (which certainly can be solved) but whether fibre optics (or even old fashioned glass rods) can be sensibly used to transmit the light - without any sort of amplification.


:-)

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Non-electric Television.

Postby Stephen » Tue Apr 24, 2007 12:05 am

I agree about the acid test, Roland. The best approach would be to use two optical scanning elements coupled by a common drive shaft and a length of optical fibre or rod so as not to get sidetracked with scanning/synchronisation issues.

The key is to transfer as much light into and out of the glass fibre or rod as possible. Using apertured Nipkow discs would not work. Too much light would be wasted. Good potential candidates would be lens discs with reasonably fast lenses or mirror drums.

I wish that I had more time to try this myself in the near future. As a BP annuitant and former employee, I find the concept of warming up my oil or gas fired tellie most appealing.
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Re: Non-electric Television.

Postby Roland » Tue Apr 24, 2007 11:10 am

Stephen wrote:I agree about the acid test, Roland. The best approach would be to use two optical scanning elements coupled by a common drive shaft and a length of optical fibre or rod so as not to get sidetracked with scanning/synchronisation issues.


Yes - this is what I was thinking about. Avoids the synchronisation issue completely.

I too don't really have the time to pursue this - but I was thinking that at least initially I'd drive the shaft by electric as the Stirling engine can always be subsituted later when the concept has been proved.

I notice that fibre optic is relatively cheap - so buying a few metres of that shouldn't be a problem. If a bunch are grouped together you could get a light pipe the same size as an LED. I've already experimented with single LED displays which use a lens to spread the light over the picture area. As far as I know the same technique will work to collect the light in the first place.

However I haven't yet progressed past aperture disks. These obviously are not ideal - but maybe a 16 or even 8 line picture could be implemented which should allow each hole to be bigger and thus let more light through. Also the disk could have 2 or even 4 sets of holes around it to increase the FPS for a given RPS.

Other than that I thought of using halogen desk lights (or oil/gas lamps ;-) ) to light the subject and a darkened booth to view.

Its certainly got to be worth a go - maybe I'll find the time to start experimenting :-)

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Non-electric Television.

Postby Stephen » Wed Apr 25, 2007 3:48 am

It also seems to me that with symmetrical optics in each scanning device each one would become an optical transceiver so that such a system could be two-way, much like a string telephone or speaking tube for audio communication. In fact, if the system worked, one could add a speaking tube for full colour two-way audio-video communication using 19th century technology. That would be a nice exhibit for the next convention.

Now that I think of it, childhood fears that the people in the tellie could see and hear me would become a reality.
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Postby Roland » Thu Apr 26, 2007 10:51 am

I found this link for fibre optic, 12p a metre sounds good to me - though its only .5mm so a fair few metres (10, 20?) would be required to make a light pipe even 1m in length.

http://www.barrule.com/Workshop/scratch ... onics.html

As far as the disk is concerned - I think 8 scan lines per frame and 4 frames per revolution would be a good starting point. True the resolution is poor - but at least the refresh would be reasonable - and the holes could be a decent size.

If I could find a decent source of cheap lenses - I'd consider making a lens disk.

:-)

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Re: Non-electric Television.

Postby Roland » Thu Apr 26, 2007 10:54 am

Stephen wrote:fact, if the system worked, one could add a speaking tube for full colour two-way audio-video communication using 19th century technology. That would be a nice exhibit for the next convention.


Yes - in fact any form of non electric TV would be something different for the next convention. I am in the UK - but currently can't attend - but I suppose I might make a special effort if I had something really different to show ;-)

:-)

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Postby Roland » Wed May 02, 2007 10:54 am

Roland wrote:I found this link for fibre optic, 12p a metre sounds good to me - though its only .5mm so a fair few metres (10, 20?) would be required to make a light pipe even 1m in length.


I found another source worth checking out:

http://www.greenweld.co.uk/cgi-bin/sh00 ... 407#aQ6407

I've ordered some of the 730mm stuff with the main intention of making a decent light pipe between the 2 Nipkow disks. For a variety of reasons - not least space I might mount the 2 disks quite close to each other (I had originally planned on 1m apart) - so each 730mm piece may well get cut up so I can have a shorter thicker bundle of fibres.

Its also occured to me (and I'm sure its been discussed around here somewhere) that I could also use fibre optic to actually deliver the light direct to where the hole in the disk would normally be. The 12p/metre .5mm stuff might actually be better for this part of the solution - so I plan to order some of that stuff too.

I've not had much time to devote to this (goodness knows when I'll get the chance to actually build it) - but I still plan to use 4 spirals of 8 holes as this should provide more light to demonstrate what is likely to be a fairly marginal system at best.

:-)

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Postby Stephen » Wed May 02, 2007 11:06 am

Roland wrote:
Roland wrote:Its also occured to me (and I'm sure its been discussed around here somewhere) that I could also use fibre optic to actually deliver the light direct to where the hole in the disk would normally be. The 12p/metre .5mm stuff might actually be better for this part of the solution - so I plan to order some of that stuff too.
Yes, Roland, see my proposal for an optical fibre scanning element at http://www.taswegian.com/NBTV/images/OFSS.pdf . Referring to Figures 1 and 2, you would simply replace the modulated light source 4 (or photoelectric sensor) as shown with the end of the transmission fibre.

The optical commutator 6, just comprising the inner ends of optical fibres, would distribute the light to the outer ends that protrude through apertures in the scanning element. Such optical fibre scanning elements at each end should offer excellent efficiency.

I am glad that you are working on this. I wish that I had the time to do so.
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