NBTV Camera Question

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NBTV Camera Question

Postby Harry Dalek » Wed Apr 11, 2012 9:29 pm

Gary did very well on he's camera in this post,well worth a look again if any one missed it .
http://www.taswegian.com/NBTV/forum/vie ... sc&start=0
I was wondering about nbtv cameras and sync can you make a camera without it for a start ?
Looking at this circuit for the dome sensor i was thinking the circuit could be made simpler with a LM311....looks to me like the trany one has uses a bit of feed back.
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Re: NBTV Camera Question

Postby gary » Wed Apr 11, 2012 11:28 pm

harry dalek wrote:Gary did very well on he's camera in this post,well worth a look again if any one missed it .
http://www.taswegian.com/NBTV/forum/vie ... sc&start=0


Urk! that was NOT a very good result, and was deliberately so as it was just a quick and nasty lash up to test my timebase correction software.

If you are considering building a camera (and I highly recommend that you do) may I suggest you start with a flying spot arrangement? - I have found this method MUCH easier to get going - the inconvenience of a darkened room is insignificant to compared to the ease of construction.

harry dalek wrote:I was wondering about nbtv cameras and sync can you make a camera without it for a start ?


Harry it is VERY easy to add sync, just add an encoder print out as used on the MUTR monitor (available on this forum as a PDF file) and use the reflective sensor I sent you to pick up a signal from it and record it directly on to the right channel of your sound card. It can then be later mixed into the video signal or used directly into the sync circuit of a mechanical monitor - easy peasy.

Note that it is desireable to have the camera disk spinning at 750 RPM but it is not essential IF those sync pulses are recorded. If they are not it is still possible to stabilise the picture but it is much more difficult. None of my cameras have the disk running at exactly 750 RPM but they all have some form of sync pulse attached which allows the picture to be time base corrected or synced to a monitor. I attach another example where the disk was running from just a 5v power supply.

harry dalek wrote:Looking at this circuit for the dome sensor i was thinking the circuit could be made simpler with a LM311....looks to me like the trany one has uses a bit of feed back.


Harry this circuit is optimised for low noise - this is VERY important for good results - having said that the camera that produced the attached video has just a single BC108 as the front end preamp.

Whilst good results can be obtained I can assure you getting even these admittedly basic results can be very rewarding and educational - give it a go!
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Postby gary » Thu Apr 12, 2012 12:07 am

And this was the simple lash up used to produce the above video:
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Re: NBTV Camera Question

Postby Harry Dalek » Thu Apr 12, 2012 5:42 pm

Gary that result would make me happy ! i will have a look at the other video in a sec as well.

I am still doing the other project but thinking about how to do it and what i have handy ! so getting bits together ,i want to use a old 80s video camera lens looks good for a start and don't have to worry about that part of it .

So yes i am considering building a camera,i didn't think of the flying spot idea ...i have to ask here and think it must ? that the light falling on the object from the nipkow light box have to be focused on the object or the focusing is done on the sensor or both ?

As i was thinking about it i was going the lens nipkow and sensor idea in a box.... i suppose it wouldn't be to hard converting one to the other .

I was asking about the sync thing just to do it in stages in testing ...i'd most likly just use the old laptop as a monitor for a start ...i suppose the sync could to taken right of the disk opto fork hall effect idea again mmm.

I would like to get results that are ok but the mind is willing the hands have their own mind

:roll:

Oh i will give it a go gary just looking into how to tack it all together with other bits i find in my shed .
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Postby Harry Dalek » Thu Apr 12, 2012 6:01 pm

gary wrote:And this was the simple lash up used to produce the above video:


Hi gary my internet is crap today trying download the avi got to 10% so is that you there in the video ! i will try to download some more but looks good ,thanks for posting the step up you used i don't think i have seen a camera on the forum before .

Looks to me like its a slide projector with the nipkow between the lens and light yes and the dome sensor on th other side picking it all up ...?
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Postby gary » Thu Apr 12, 2012 6:59 pm

Yes that's me Harry - the quality of the video is poor enough to let me get away without scaring anyone I think. ;-)

The first video (the one you referred to) was from a camera of the type you were intended to build. I find this type more difficult to build and you really need at least one, but preferably a pair of bulls eye lenses as well as the object lens you show.

With the FSS you don't need a lens system in front of the dome sensor, however you can improve the cells light catching ability by using a large fresnel lens (i.e. those used for reading A4 sized pages of text).

The light spot coming from the nipkow disk needs to be focussed on the subject, I have used an old projector for simplicity - if you can pick one up from your dump shop or somewhere it will save you a lot of work.

I can't recommend the recording of a sync signal right at the beginning - you will get frustrated if you can't lock on to the picture - it's worse than having a monitor not synced believe me.

Having said that Chris Long's Camera experiments virtually never used sync - he did try to make the motor speed as constant as possible though. I have posted an example of those experiments somewhere on this forum in the past as well.

Your biggest problem will be noise in the electronics - it is imperative that you box them in a shielded container of some kind (I used a biscuit tin in that last lash up) . I also ran all of the electronics from batteries to avoid the problems with noisy PSUs and bad layouts etc., at least as much as possible.

There is a very good article on FSS cameras by Doug Pitt in V23-2 of the newsletter. I highly recommend you read that if you intend building one.
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Postby Harry Dalek » Thu Apr 12, 2012 9:35 pm

Gary got to see the rest of the video looking at the camera must be like looking at a monitor video free..i am wondering how bright it must be i know it must be bright enough to project but does not look like its blinding you .

I rather your first camera system as i was thinking of making it cd sized but i do like what you told me the other system is easier.

OH old projectors yes i come across those all the time i have at least 2 in my shed ,pulled 2 others to bits a year ago for the lens,i think i still have a small one which might be right for the job

Thanks fo rthe information that Gary i will have a read of the news letter for sure ,i read Klaas saying these things are harder than monitors and from what you say sounds like they do have their own touchy problems.

Time to do some reading !
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Postby gary » Thu Apr 12, 2012 9:47 pm

harry dalek wrote:i am wondering how bright it must be i know it must be bright enough to project but does not look like its blinding you .


No it's just a twinkle as the spot is very small.

harry dalek wrote:I rather your first camera system as i was thinking of making it cd sized


Well that's fine but please make sure you understand the optics involved (plenty of information in the newsletters). Also note that with a CD sized disk the accuracy of your mechanics is pretty extreme. I have only attempted a monitor at that size and that was pretty hairy - none-the-less it can be done.

BTW it may not have been noticeable but my disk was a bead disk which allows the light source to be less bright - but others have had great success with normal apertures.

OH old projectors yes i come across those all the time i have at least 2 in my shed ,pulled 2 others to bits a year ago for the lens,i think i still have a small one which might be right for the job

harry dalek wrote:Thanks fo rthe information that Gary i will have a read of the news letter for sure ,i read Klaas saying these things are harder than monitors and from what you say sounds like they do have their own touchy problems.


And that is true, but as you can see you can achieve (admittedly poor) pictures with some very basic mechanics - good luck!

(Personally I reckon you haven't really gotten into NBTV until you build a camera) ;-)
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Postby Klaas Robers » Fri Apr 13, 2012 7:05 am

However, if I see the work of Eddy Greenhough at CD nr 3, the Toby Jug, That is not bad at all. Eddy solved the sync problem by using the same disk for the camera and for the monitor. You will need a Nipkow disc with 1½ spiral, but that saves you alot of problems......

Untill you like to record the signal. Then there is no sync and indeed it is very difficult to add that at that stage. It took me at least one full day of computerwork before a good enough sync was under the video signal.

Chris Long managed to do this by placing two discs on a long spindle. Then as well the synchronisation problem is solved mechanically. And still you learn a lot from it.

I once had the idea that we should rebuild the flying spot scanner that was used in the Baird BBC studio. Nice photo's of it in the book of Don Mclean. But also ther I can't oversee the optical problems.
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Postby gary » Fri Apr 13, 2012 9:24 am

Yes having the monitor on the same shaft is a good way of ensuring sync - and as the first half dozen of my cameras were done that way I can't disagree that it is a good way to go.

However, when I built mine I didn't have the advantage of a computer to record the signal and analyse it. I did record some on tape but all but a very little of that remains.

Adding sync via a print out encoder and the reflective sensor and the recording on the right channel of a stereo recording is so easy that it is hardly worth NOT doing. And I guess I am being a little selfish because then Harry can post his results for us all to look at ;-).

OTOH, Harry, I know from previous posts that you like to tread the steps of the early experimenters so perhaps for your first effort the monitor/camera on the same shaft IS the way to go. We could get to see a video of the results at least...

edit: Because it is so easy to do, I think that even if do go the dual camera/monitor route that you should add the sync on the right channel - you won't regret it later when you want to view a recording.
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Postby Harry Dalek » Fri Apr 13, 2012 4:19 pm

Yes Gary Klaas yes the monitor and camera on the same shaft is the easiest was to go ,i have a design in my head with the bits i have for a stand alone camera ,i think i will try the flying spot idea a bit different .

I will run it by you in case you think i am wasting my time as i want to try a laser with out the lens this spreads the light as a projectors lenses would do to the light ,would be nice a replacement ...and drops the size of the thing i have this handy....reading the flaws with a normal flying spot camera in day light i was thinking more so using the green laser i have, if i use one wavelength of light with either a dome sensor or light trany with a green fliter ...the thing might reject most of the day light in a room and still work ,i am not sure the light wave length the dome sensor is sensitive to so its an idea ..... i could do it with a red laser also as i have a few of those .

In any case i will go with the lens i showed and i have a tiny cd dvd player dc motor and disc mount that saves construction time trying to mount a disc of some sort and has the added advantage of easy removal and size what i want to try.

I know i could more than likely do it combining the sync with the video but the idea on sync on one channel and video on the other letting the pc sound recording program do it is a easy step for sure .
Using the same disc as a monitor has been done i do like the idea of that .


When i was thinking first of how i would see or test the Camera idea i was thinking of using one of the live NBTV programs to view...never really looked into if yours gary or doms does this as i use them for wav recordings when i do but i suppose i would have to combine the sync with the video in a circuit for that .

I think my step next is hooking up the lens to the disc ,making the nipkow and working out the light and seeing if i can focus the projected spot of light see how that scanning works .

One thing that i did when i first became interested in mechanical television in the 80s was try to make a nipkow camera monitor with just seeing some pictures in a book ,well my system i didn't amplify the light from the light trany i used it to control a oscillator i suppose this was FM instead to modulate the light ,i was thinking at the time it would give a cleaner signal to do the light modulating...i know that worked ,used a neon nixie tube...would not of crossed my mind to use leds back then perhaps the cost .
As i recall i got shadows no wonder no lens and i think had the holes to big,lets see if i can do better 30 years later fingers crossed .



:shock:
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Postby gary » Fri Apr 13, 2012 4:32 pm

Harry, I don't have time just now for a full blurb, but I can't see how you are going to use a laser (which may be dangerous anyway) with a nipkow disk as the beam will only be picked up by one or two apertures - if you use a mirror drum that would be different.

FFS can work in daylight too, as long as the lighting is constant (i.e. DC)

TBP CAN be used without sync providing your motor speed is constant - eg a stepper or synchronous motor.

More later...
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Postby Harry Dalek » Fri Apr 13, 2012 7:24 pm

gary wrote:Harry, I don't have time just now for a full blurb, but I can't see how you are going to use a laser (which may be dangerous anyway) with a nipkow disk as the beam will only be picked up by one or two apertures - if you use a mirror drum that would be different.

FFS can work in daylight too, as long as the lighting is constant (i.e. DC)

TBP CAN be used without sync providing your motor speed is constant - eg a stepper or synchronous motor.

More later...



Hi Gary

The laser would be used with out a lens its like a strong torch removing the its lens its out of focus you get a giant round circle....i wasn't thinking of looking into it more things...but i will take the advice danger it down just an idea on the light it would be no need if as you say they can work in room light.

I was looking at the old camera skeleton looks like i can use it as a base for the rest just need to cut a little aluminum off to mount the disc .
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Postby gary » Sat Apr 14, 2012 4:39 pm

I see Harry, it's just that I wouldn't think under those circumstances that the laser would be bright enough - their intense brightness depends on them being collimated.
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Postby Harry Dalek » Sat Apr 14, 2012 5:34 pm

gary wrote:I see Harry, it's just that I wouldn't think under those circumstances that the laser would be bright enough - their intense brightness depends on them being collimated.


Gary

Yes normally so but this Green laser pretty bright with out a lens as well i was going to try it as a nipkow projector it would be interesting to see if it could do it its 100mw one ...i think it could but the distance who knows might just be good for a few cm after the nipkow gets done dimming the light.

Well today i mounted the lens and drive disc which will be the nipkow ...i need a mask after i should think before the light ,but any way i have it so the case is bolted to the old dvd laser drive geared arm so i can adjust the future nipkow just in the right position left or right ....
Sorry about the poor photos today kids have taken my camera for an outing ....
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