Mirror Camera project

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Re: Mirror Camera project

Postby Harry Dalek » Thu Jul 31, 2014 11:58 am

gary wrote:Ok, I am with you now - you are using the xtal to control the motor speed and the syncs are being generated (correctly) from the line scanner opto sensor - that's the arrangement you definitely would want when it is working as a camera as it will also align the sync with the start (or end) of each video line.

Yes belt drives can be problematical if you get slippage, which is why many go for a direct drive. None-the-less your signals seem very serviceable - it looks like you are nearly ready to start testing as a camera?


OK Gary
i was not going to go further unless i had fixed things i hadn't thought of ,your reassurance to go on to the next step i will try again will not take to long to wack it together again ...

Yes the belt drive is not the best way to go i will think again when i connect a motor to some thing in the future .
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: Mirror Camera project

Postby gary » Thu Jul 31, 2014 12:11 pm

Just one thing Harry for my interest if you don't mind. That video signal you used in those last tests - what sample rate was it created at? (actually if you could post it that would be good).
gary
 

Re: Mirror Camera project

Postby Harry Dalek » Thu Jul 31, 2014 1:30 pm

gary wrote:Just one thing Harry for my interest if you don't mind. That video signal you used in those last tests - what sample rate was it created at? (actually if you could post it that would be good).


Gary some thing that comes to mind is the samsung is used as the play back device to the video mixer then recorded to the LG lap top and yes recorded at 48000 but the play back i am not sure ? the black sync was no video so all done on the LG but the white to black and test wavs were from samsung to video mixer to LG.
Thing i am thinking is can it play back at that rate i recall seeing recorder apps for the samsung only doing 44100 play back the same ?

The test card one were 2 old nbtv wavs i made ages ago on Doms software so i have no idea there .

The odd one out is your sawtooth made by you so that would be 48000 ,i copied that over to the samsung then played it back with VLC player app to my video sync mixer added the sync and recorded it at 48000 with audacity on the LG laptop .

So i am thinking the files on the samsung are the same but a play back by the phone problem ? i can send the files but i think they will be the same ?
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: Mirror Camera project

Postby gary » Thu Jul 31, 2014 1:44 pm

Ok, yes it would seem that your playback device (phone?) is at fault - that's ok - I was just wondering where the drift was coming from - cheers.
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Re: Mirror Camera project

Postby Harry Dalek » Thu Jul 31, 2014 4:00 pm

A small leap of encouragement but still early days .

I can tell the head amp is working .

But any case i did my first test just pointing the camera at the front window ,i can see a thick light line and it changes when i move the camera up and down or rock the frame mirror.

i was rocking the frame mirror and towards the end i waved my hand in front of the camera and i can see gaps of my fingers so thats good even if its just shadows ,i am still not sure if i have the optics right ,that was just a small part of the raster .

Camera is on its side and i have no frame control just yet having converted the line oscillator to a crystal means i need to build one ,if cameras are like monitors i found having a separate line and frame control so long as the line control was in sync you would always get some sort of picture with the frame either to narrow or to wide if the frame motor was running to fast or to slow ,but again for a camera i have no idea yet .

Results today look hopeful but a long way to go .
Attachments
firsttest.wav
towards the end moving my hand across i can see shadows of fingers
(1.86 MiB) Downloaded 572 times
test2.wav
moving a screw driver shaft
(1.47 MiB) Downloaded 597 times
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: Mirror Camera project

Postby Harry Dalek » Sat Aug 02, 2014 11:36 pm

Doing a few more tests i have found once again a flaw in the optical system ,my mirrors are to far apart .

I used a led closer to the line mirror while working and moved it across the distance of the line mirror and i could see on Garys viewer a repeated dot across all the lines so a line moving up and down with my movement .

Looking at what worked i drew a quick sketch at where the mirrors should be distance wise and some how i have to adjust my mirrors to around that position,so had another head scratching afternoon with optics and repositioning on my mind.

What i came up with is close to my sketch so hopefully it improves results ,doing this also gave me a chance to try resonance on the frame mirror still need to position the electro magnet behind the mirror.
Attachments
IMG_8898-crop.JPG
ruff sketch polygon frame mirror needs to be closer
IMG_8898-crop.JPG (150.21 KiB) Viewed 14022 times
IMG_8899.JPG
new idea to try
IMG_8899.JPG (308.43 KiB) Viewed 14022 times
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: Mirror Camera project

Postby Harry Dalek » Fri Aug 08, 2014 12:33 am

Have not done much since my last posting till today to see whats going on with the new mirror distances and such .

Still have a problem with full screen light detection it seems to be either the length of the frame mirror needs to be longer or perhaps a curved mirror ,just moving the frame mirror a little either side same plane as the line mirror i can see when pointing an led at the camera which makes a straight light line viewing the live video ,it can move the light line full top and to bottom of the screen so at the moment i have a little cut off point say a quarter from top and bottom .

Still very simple results just getting the frame mirror to vibrate i can see 2 images of the led i am pointing at the camera mirrors ,perhaps the frame mirror does have to vibrate twice as fast.
Attachments
IMG_8908.JPG
Testing out side housing
IMG_8908.JPG (270.4 KiB) Viewed 13984 times
MVI_8907_converted.gif
MVI_8907_converted.gif (7.36 MiB) Viewed 13984 times
MVI_8918.gif
MVI_8918.gif (5.41 MiB) Viewed 13984 times
MVI_8919 (1).gif
Vibrating the frame mirror you see 2 images of the led as oscillations stop line of light just via the line mirror
MVI_8919 (1).gif (4.78 MiB) Viewed 13984 times
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: Mirror Camera project

Postby gary » Fri Aug 08, 2014 10:51 am

Harry surely the mirror should perform one full sweep every (32/number of facets on mirror drum) rotations of the mirror drum? (assuming 32 lines per frame)

BTW If that is a vibrating mirror - actually what I would call an oscillating mirror - how are you handling the fact that it retraces?
gary
 

Re: Mirror Camera project

Postby Harry Dalek » Fri Aug 08, 2014 1:28 pm

gary wrote:Harry surely the mirror should perform one full sweep every (32/number of facets on mirror drum) rotations of the mirror drum? (assuming 32 lines per frame)

BTW If that is a vibrating mirror - actually what I would call an oscillating mirror - how are you handling the fact that it retraces?



Hi Gary

Oh i didn't know there was a difference between vibrating mirror and an oscillating mirror if i had to choose i would say the relay would be the first and this in resonance the other .

The retrace is as you picked up the reason i am getting 2 images at that last oscillation ,having a good look at it starts off at 4 then 2 as it ends which i think it speeds up as the oscillations end ? mmm i hope ! as i would think twice the frame speed it would drop to 1 if not it has me wondering how some of the other projects i have seen using Resonance for the frame mirror work .

I am mainly just trying it out of interest i would like to see what happens with a electro magnetic(old relay without the relay and spring) behind it and see what 25 hz does ,haven't really seen an on screen run with it yet and not tried it at that frequency .

Could be very wrong and wasting my time on it it just had me wondering how others had done it and what i read they had done was double the frame frequency ?
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: Mirror Camera project

Postby gary » Fri Aug 08, 2014 1:44 pm

Well the mirror is being swung back and forth right? Or have I missed something? In other words the mirror would describe a sine wave when plotted against time. These things are usually built as galvanometers, you are using a relay in some way but it's hard to see how it's really working in the videos and diagrams but I have imagined it to be more-or-less the same action. Calling it a vibrating mirror is fine I suppose but for me it doesn't indicate the "action" of the mirror - it could just as easily refer to a mirror that's just vibrating randomly (which make could light shows).

I can't see how the speed is going to change the problem - you say doubling the speed but doubling it from what? I would have thought that doubling the speed of the "vibrating" mirror would just halve the number of lines per frame.

Perhaps you could tell us how you are working out your various speeds, or remind us if you already have (it's a long thread ;-))


Edit: oops yes you stated that it was 25 Hz, sorry
gary
 

Re: Mirror Camera project

Postby gary » Fri Aug 08, 2014 3:53 pm

Sorry Harry I think I have made a couple of incorrect assumptions, let me tell you what I think is happening and you can tell me if and where I am wrong.

I assume NBTVA standard 32 line

The polygon mirror is your line scan, and as it has 6 facets it would need to rotate at 400/6 revs per second (4000 rpm).

The vibrating or oscillating mirror is the frame scan @ 12.5Hz - but here we start to get into difficulties because an oscillating mirror doesn't have instantaneous flyback it scans one way and then back the other, presumabley at the same speed and thus you have an effective frame rate of 25Hz with each alternate frame having the frame scan direction reversed (actually it's worse than that because of the sinusoidal nature of the oscillation the speed of line scan varies along it's length). That accounts for your double image then I suppose. It also seems to me that you would want to halve your speed rather than double it. You would still have the frame direction changing every other frame but if you displayed the signal the same way it would be corrected!

So unless you have worked out a way to have the mirror trace a saw tooth rather than a sinusoidal path, It would seem you can still get a picture out of it but that it will be decidedly non-standard - but why should that stop you? LOL I might be coerced into adding your new standard to TBP...

BTW This is why Alan Short (and others) use either a cam operated mirror (or arm) or another mirror polygon - the cam gives near instantaneous flyback and the mirror polygon doesn't have any flyback at all.
gary
 

Re: Mirror Camera project

Postby Harry Dalek » Fri Aug 08, 2014 9:39 pm

gary wrote:Sorry Harry I think I have made a couple of incorrect assumptions, let me tell you what I think is happening and you can tell me if and where I am wrong.

I assume NBTVA standard 32 line


Hi Gary sorry i had to go out again so couldn't reply ,so at the moment looks like not unless i swap the swinging mirror with rotating mirrors .

I would not think to correct you on NBTV you know much more than i ever will ,i can try and explain best i can what i see if i do a working experiment .

My little achievements on this are a step forward i know its taking a while so hope i am not boring any one .

The polygon mirror is your line scan, and as it has 6 facets it would need to rotate at 400/6 revs per second (4000 rpm).


Yes i am working the little ex dvd motor thats what the polygons rotating at but my pulley system ratio the motor must be greater than that .

The vibrating or oscillating mirror is the frame scan @ 12.5Hz - but here we start to get into difficulties because an oscillating mirror doesn't have instantaneous flyback it scans one way and then back the other, presumabley at the same speed and thus you have an effective frame rate of 25Hz with each alternate frame having the frame scan direction reversed (actually it's worse than that because of the sinusoidal nature of the oscillation the speed of line scan varies along it's length). That accounts for your double image then I suppose. It also seems to me that you would want to halve your speed rather than double it. You would still have the frame direction changing every other frame but if you displayed the signal the same way it would be corrected!


I doubled checked Gary i could only find one of the projects so far using a resonance but Yep i was wrong it was half the frame frequency as you say ! ,perhaps then speculating instead of an image either side it will meet in the middle double the size just thinking whats happening .
Half the speed would i suppose tend to be easier for moving the mirror,but If using oscillating mirror may mean its not true NBTV standard ,if it can't do a 12.5 hz but half that oh well thats still interesting .
Does it mean the line has to be 800hz then a frame rate at 12.5 would work ...any case as is this is enough of a problem for me for now .

So unless you have worked out a way to have the mirror trace a saw tooth rather than a sinusoidal path, It would seem you can still get a picture out of it but that it will be decidedly non-standard - but why should that stop you? LOL I might be coerced into adding your new standard to TBP...


No no just a sine wave so at 6 hz fine for a still image but moving a little jerky :wink:

BTW This is why Alan Short (and others) use either a cam operated mirror (or arm) or another mirror polygon - the cam gives near instantaneous flyback and the mirror polygon doesn't have any flyback at all.
[/quote]

Yes i understand that cam makes a mechanical sawtooth ,he did try the speaker idea for the frame mirror for a simple camera i read but he must of had the same problem as here ..
The 2 625 line versions i saw use frame mirror resonance ...so at half frame rate they must also not be true standards either .
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: Mirror Camera project

Postby gary » Fri Aug 08, 2014 10:38 pm

This is just my opinion Harry but I think you should persevere with this arrangement if only for the "hell of it' - in principle it should be able to produce a reasonable picture and who cares if it isn't exactly to spec? I mean there are people on this forum who are (shhhhh) experimenting with entirely "electronic" systems - yes sacrilege I know, but if it makes them happy... and, more importantly, keeps them quiet... ;-)

If you put 6.25 Hz into your "vibrating" mirror then you should end up with 12.5 frames per second if my imagination serves me right (and heaven knows I am no Einstein or Tesla when it comes to "thought experiments").

I tell you what - if you continue your experiments with this I will write some software to reverse every second frame and display it correctly, hows that?

and yes you could up the line rate to 800 Hz and go 25 fps - why not? But can your motor/polygon do 8000 RPM???

BTW, what do you mean by resonance? I assume you are talking about a galvanometer type of set up?

I am not sure what they do in the 625 line oscillating mirror systems (I have never really been convinced they are real) but, in a CRT television system they actually require a finite fly-back period (can you image such inadequacy? tch tch) and I suppose it is possible for a very well designed galvanometer to replicate that, I am not sure.
gary
 

Re: Mirror Camera project

Postby Harry Dalek » Fri Aug 08, 2014 11:35 pm

Just a quick one Gary before i reply surprising results hooking up the electro magnet at 12 hz
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: Mirror Camera project

Postby gary » Fri Aug 08, 2014 11:48 pm

Good! I like surprises.
gary
 

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