Starting at the beginning with Mirror Screws

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Re: Starting at the beginning with Mirror Screws

Postby Harry Dalek » Thu Oct 05, 2017 4:28 pm

McGee2021 wrote:I seem to be getting the feeling that you want to make a kerr cell, but, then again, i did just have to skim over the last few post very quickly! Anyway, i found a list of extremely dangerous and pretty safe chemicals that have a high kerr constant. Might i suggest Anethole, a sweetener?

https://www.nist.gov/sites/default/file ... crd435.pdf


I have a great interest in vintage television on how things work .....its something i have never really tried it might go on my to do list but i would never try it with that nasty chemical i am not that Brave .
The Kerr cell i sort of feel is a pinched idea slight change of the Faraday device .
If i find information of use i like to post it up the forum is a good diary for stuff to retrieve later ..... as to wanting to make one for sure but i wouldn't have any use for it at the moment as i am working on camera ideas but it would be a nice thing to try for a future projection monitor ..time time time arrrr
Yes that's a good list i will have a look at it depends on what you can track down Anethole would be one to track down ,the first Kerr cell just used glass i think you were having a go at one any luck on the design ? Anethole is found in essential oils plant oils so that would be a easy one depends on how pure it has to be or it matters for a test at least .

Steve
I don't think this would work with a bare mirror screw. Remember, when viewing, it doesn't create any real image (that could be reversed in principle by a camera) at all.... instead, just a series of virtual images depending on where the viewer stands.


OH it would need a shutter perhaps that's a good reason i have never read about a mirror screw camera ! :wink:

However, if you modified a mirror screw to give a projected image on a screen, using a lens say, then I guess you could use it in reverse as a camera.


Size is a problem as in its silly to use a large monitor mirror screw for use when a small one would be better for a camera ....just some thing i was wondering about and if it crossed your mind .

My opinions could be wrong. I may have made a mirror screw but I still don't really understand the optics in sufficient depth! Karen is much better in this regard.


Don't worry i am the same on the optics side all trial and error with me , reason i pushing my self on camera ideas its some thing i have to learn .

Yes they could of done with Karen back in the early days would of given Baird and the others a run for their money .

Keith
I have come across this video before its a great idea but it was beyond my lab skills anyway ,i had thought of LCDs before ,i am not sure they could handle the high amount of light a faraday or kerr device could may be if you put a few in parallel then i bet they could .
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: Starting at the beginning with Mirror Screws

Postby Robonz » Thu Oct 05, 2017 5:20 pm

Harry. LCD projectors use LCD's as optical shutter and they have extremely bright light sources so they can work. i suspect you could get an LCD from the trash and cut a piece out of it and add some copper tape down two sides, seal it up and it might just work. It would be fun to try, that's for sure. I do know they have really nice polariser sheets and you would need those anyway.

I have been watching your camera builds and really respect your efforts. Keep on building!

Cheers
Keith
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Re: Starting at the beginning with Mirror Screws

Postby Harry Dalek » Thu Oct 05, 2017 6:17 pm

Robonz wrote:Harry. LCD projectors use LCD's as optical shutter and they have extremely bright light sources so they can work. i suspect you could get an LCD from the trash and cut a piece out of it and add some copper tape down two sides, seal it up and it might just work. It would be fun to try, that's for sure. I do know they have really nice polariser sheets and you would need those anyway.

I have been watching your camera builds and really respect your efforts. Keep on building!

Cheers
Keith


Yes i forgot about those Keith i have not really come across any in my scrapping rounds but for sure then good enough for the job ! .
I am sort of more interested in the older Classic ways they did the light control than using today's or not quite today's technology so hearing Steve had a go at a Kerr cell and others i had always been interested to see some one have a go on one for our hobby ...
I just came across a warning if experimenting with nitrobenzene so it does explode using the other suggestion in a post or 2 pack would be wise ...I should start a topic for the Kerr cell or light control taking over Steves Mirror screw postings here .
I have to get back to the flying spot camera work been on holiday and came back having to go right back to work ,i am working out the best place to insert horizontal sync pulse that's where i left off it seems to make a big difference .
I also have to finish off the higher line rate monitor so i can test the flying spot here ,like every thing here there are no plans to copy from apart from past
go's trial and error ideas .
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Re: Starting at the beginning with Mirror Screws

Postby albertMunich » Fri Oct 06, 2017 4:47 am

Hello out there, I am glad there is life in the thread again.

The idea that the cell must be activated to work is interesting. Wonder what happens there at the molecular level...something like an electret?

Would LCD shutters from 3D shutter glasses work as light valves when cooled properly?- sheet polarizers would be the weak point on a Kerr cell as they tend to overheat and lose their effect in very strong light. Nicol prisms would be thermically more stable....

In conjunction with a mirror screw would a functioning light valve be a requisite for a projection device?

I do not completely understand what a Kerr cell would be able to do that a high power led source could not?

If you hit that stuff with 30 kv, and then shoot an arc or xenon light through the cell, you get even more of an explosion risk...duck and cover!
I wonder if the cell could not be made very thin & small so there is a minimum of explosive liquid in there.—is there a problem with convection currents and a minimum thickness the light has to travel for the effect to be visible?

I wonder what type of light valve they used for early sound-on-film systems...probably some kind of galvanometer.

I have returned home and would like to get ahead to experimenting with 3d printing of slats/pieces for mirror screws as soon as I find the time.
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Re: Starting at the beginning with Mirror Screws

Postby Harry Dalek » Fri Oct 06, 2017 10:58 am

albertMunich wrote:Hello out there, I am glad there is life in the thread again.

The idea that the cell must be activated to work is interesting. Wonder what happens there at the molecular level...something like an electret?

Would LCD shutters from 3D shutter glasses work as light valves when cooled properly?- sheet polarizers would be the weak point on a Kerr cell as they tend to overheat and lose their effect in very strong light. Nicol prisms would be thermically more stable....

In conjunction with a mirror screw would a functioning light valve be a requisite for a projection device?

I do not completely understand what a Kerr cell would be able to do that a high power led source could not?

If you hit that stuff with 30 kv, and then shoot an arc or xenon light through the cell, you get even more of an explosion risk...duck and cover!
I wonder if the cell could not be made very thin & small so there is a minimum of explosive liquid in there.—is there a problem with convection currents and a minimum thickness the light has to travel for the effect to be visible?

I wonder what type of light valve they used for early sound-on-film systems...probably some kind of galvanometer.

I have returned home and would like to get ahead to experimenting with 3d printing of slats/pieces for mirror screws as soon as I find the time.


I can't say i have seen or heard of a working kerr cell in the NBTV world with a monitor have to check the old newsletters ,they must of worked well back in the day ,they had projection televisions that would taken a hell of a lot of light to work as yes all had to be heat proof as well if they used arc light or filament type thus the glass prisms work be good .

I agree the risk of a spark using nitro benzene is is very high at KV very likely ! I would say any experiments should be done with a safer chemical these days and keep the nitro benzene idea in the LAB...i saw one selling on ebay how the hell you could post it is beyond me if it broke you would be in so much trouble posting a toxic chemical .

They used them with mirror screws so that must oi worked as well ....the idea of them is great just use some thing safer even if it doesn't work as well .

I read you and i think Keith are thinking of slats Keith laser cut mirrors and you 3d printing it ...it came across my mind if printing the slat middle of that slat perhaps have a groove in the middle of it for gluing the mirror on as the mirror slat would have to lay flat on the printed slat or each mirror will be not lay flat ..a problem i had many times gluing mirrors for projects with a groove it still can and be glued with out a problem .
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Re: Starting at the beginning with Mirror Screws

Postby albertMunich » Sat Dec 16, 2017 2:11 am

Hi everyone-
haven't posted here since summer but MUCH has been going on-
I have begun to make a Nipkow disc NBTV machine with Club disc & circuits. I wanted to start at the beginning before attacking anything "fancy."
I have it up and running- it was quite interesting to make it- and I'm beginning to get to the sync problem. Vic Brown has been of tremendous help to me- he patiently answered my questions. But I don't want to hijack this thread.
I still think about the mirror screw and about getting it done with 3D printing. May I ask where things are at the moment? In summer, there were several people who started 3d printing slats. Has anything come of this? I will start to look into this myself during the Christmas holidays.
I begin to look into the possibility of getting PLA or ABS parts "plated" with nickel or silver to make them reflective. There might be a way to do this.

As regards the Kerr cell, I found that German LEYBOLD company still sells one complete with the liquid for school experimental purposes!

https://www.leybold-shop.de/physik/phys ... 47331.html

Of course you will have to supply the high voltage....and the bomb proof environment!
Have read up a lot on early television - the American Radio history pages are a gold mine of information. What I really did not know was the sophistication of the Scophony system. Jaw dropping.
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Re: Starting at the beginning with Mirror Screws

Postby McGee2021 » Tue Dec 19, 2017 1:30 am

albertMunich wrote:As regards the Kerr cell, I found that German LEYBOLD company still sells one complete with the liquid for school experimental purposes!

https://www.leybold-shop.de/physik/phys ... 47331.html

Of course you will have to supply the high voltage....and the bomb proof environment!
Have read up a lot on early television - the American Radio history pages are a gold mine of information. What I really did not know was the sophistication of the Scophony system. Jaw dropping.


Wow! I have been looking for a kerr cell for quite a bit now, and the only thing i have found is from a company called Thor Labs. I might look into buying this for my mirror drum, for historical accuracy purposes. One drum with a laser, and one with a kerr cell. The American Radio History site really is a goldmine of information. Recently they uploaded a couple more of the 1934 issues of Television magazine, an extremely important resource to anybody interested in the history of mechanical television. As for Scophony, i was trying to build a receiver that was slightly larger than the normal one, minus the extremely large amount of valves needed. Unfortunately, i have been focusing all of my efforts into my televisor, so its on hold. Anyway, hopefully someone will bring us back on topic to Panrock's Mirror Screw.
John Logie Baird was obviously the man who sowed the seeds but did not reap the harvest.
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Re: Starting at the beginning with Mirror Screws

Postby Panrock » Sat Feb 15, 2020 12:19 am

Years pass... thoughts crop up about this year's convention - and I have wheeled out the grand old 120-line Mirror Screw again and run it up. After a day lost amidst the confusion of understanding how it all connects up (see pic), it turns out to still work - rather well.

One thing irks me though. Because this is a large screw and it carries 120 lines, the working deflection angle is small and the picture has to be viewed from right across my lounge, from where it appears rather small. I think the answer would be to place a giant maginifying lens of very weak optical power (focal length greater than distance across room) at the viewing position. One would then see a much larger picture through this lens placed at the other end of the room. The position of the lens could be optimised to centre on the 'best' image corrected by Karen's Timing Corrector, discouraging viewing of the inferior images to either side.

But how to make a lens several feet across with an ultra-weak converging characteristic? You can't buy things like this off the shelf (I think). Has anyone got any ideas how this could be done :?:

Thanks.

Steve O
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Re: Starting at the beginning with Mirror Screws

Postby Harry Dalek » Sat Feb 15, 2020 10:51 am

Panrock wrote:Years pass... thoughts crop up about this year's convention - and I have wheeled out the grand old 120-line Mirror Screw again and run it up. After a day lost amidst the confusion of understanding how it all connects up (see pic), it turns out to still work - rather well.

One thing irks me though. Because this is a large screw and it carries 120 lines, the working deflection angle is small and the picture has to be viewed from right across my lounge, from where it appears rather small. I think the answer would be to place a giant maginifying lens of very weak optical power (focal length greater than distance across room) at the viewing position. One would then see a much larger picture through this lens placed at the other end of the room. The position of the lens could be optimised to centre on the 'best' image corrected by Karen's Timing Corrector, discouraging viewing of the inferior images to either side.

But how to make a lens several feet across with an ultra-weak converging characteristic? You can't buy things like this off the shelf (I think). Has anyone got any ideas how this could be done :?:

Thanks.

Steve O


I would not use a lens with it as is ,it will increase the size alright but also weaken the light you would have to again increase the light to compensate .
Have you ever come across the lasers that have the lens that produces a laser line if you got a very bright laser with that lens pointed at your mirror screw i would say it would be brighter ..all you would have to do it modulate the laser which is easier enough PWM.
Perhaps a screen in this case might be able to be used than direct off the mirrors cinema style ? or viewing from behind Tv style.
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The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: Starting at the beginning with Mirror Screws

Postby Panrock » Sun Feb 16, 2020 12:10 am

Interesting comments from you Harry.

Yes, this might indicate a whole new direction for the project. What I really need are three line laser diode torches - red, green and blue. The reflection deflection angle is 6 degrees, so a back projection screen of reasonable size could be not too far away.

One thing I can try now is to shine my existing (red) laser pen at the mirror-screw through a horizontal acrylic rod (to give a vertical fan pattern) and look at the effect.

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Re: Starting at the beginning with Mirror Screws

Postby Viewmaster » Sun Feb 16, 2020 12:55 am

Be careful guys, reflected laser light is dangerous to the eyes.
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Re: Starting at the beginning with Mirror Screws

Postby Panrock » Sun Feb 16, 2020 1:12 am

A very good point and timely advice. Thanks Albert.

Especially here, when laser light may be going off in unexpected directions.
Time to dust off my laser goggles, which filter red and infra-red, methinks.
And still be careful.

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Re: Starting at the beginning with Mirror Screws

Postby Harry Dalek » Sun Feb 16, 2020 9:31 am

Yes that's why i mentioned the screen direct viewing a laser of a mirror screw or drum is some thing i have not tried rather a screen or wall reflection...a laser pen will dim every fast trying to make a raster with it ..still i don't like direct viewing with lasers just in case .

The good thing about laser line is you can adjust its line size to your mirror drum just by distance to it or adjusting the lens for focus they are rather good i think have one but never had a need for the lens yet .

i forgot you had a colour for your mirror screw wonder if something like this would work with the line lens bit of searching and thinking about it would come up with a solution .
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Re: Starting at the beginning with Mirror Screws

Postby Panrock » Mon Feb 17, 2020 2:21 am

That's an interesting device, Harry.

I am very fortunate here to be able to call on Karen's unit, which provides panel controls giving separate delays for the red, green and blue channels - in effect 'convergence' controls. So the lines-of-light - or lasers - don't need to be combined into one source (with the associated losses).

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Re: Starting at the beginning with Mirror Screws

Postby Harry Dalek » Mon Feb 17, 2020 9:41 pm

Panrock wrote:That's an interesting device, Harry.

I am very fortunate here to be able to call on Karen's unit, which provides panel controls giving separate delays for the red, green and blue channels - in effect 'convergence' controls. So the lines-of-light - or lasers - don't need to be combined into one source (with the associated losses).

Steve O


Oh that's good Karen's a genius with this stuff ..
That's very useful ! i will be watching with interest Steve i hope it go's well .
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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