Flying Spot Scanner Construction Journal

A build of a 32 line flying spot scanner.

Moderators: Steve Anderson, Dave Moll, Andrew Davie

Postby Harry Dalek » Fri Mar 14, 2014 11:27 am

Lawnboy wrote:It's been a bit of a frustrating week. I started making the disc mask to replace the one I was using for testing purposes (just a piece of cardboard with a square hole in it), and noticed that something was a little off. Turns out that the disc is about a quarter of an inch too far in so the raster is not in the center of the projector gate. Earlier in the project I replaced the base with a thicker, more sturdy piece of wood and transferred the measurements and screw holes over directly, but apparently something went wrong. The projector was designed to take full-size slides so the gate is large enough to handle the miscalculation without shading any of the holes, but the raster comes out of the lens a bit crooked and misses part of the mirror. I will try to reposition it this weekend.


When i was making my small one using a old dvd housing i used the part that ejects the dvd to move the nipkow from side to side for a position control.

My raster was to bent over a bit to i didn't worry to much about it it was more trouble to fix it i just moved the camera over a bit on its tripod.

Keep working looks good.
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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Postby Lawnboy » Tue Mar 25, 2014 6:58 am

Over the past few weeks there have been a few changes to the scanner. I have decided to drop the motorcycle mirror from the front of the unit and replace it with a door covering the lens with a mirror mounted on the inside. I found that when the projector was in proper focus the lens is actually inside the scanner case rather than sticking out a bit where I could grab onto it. There is no focus knob on this projector so the lens has to be turned manually for focusing. There was also a peculiar problem when using the motorcycle mirror mounted on a ball joint. Trying to raise or lower the raster with the mirror causes it to rotate, so even a slight adjustment in height causes the raster to appear crooked. In fact, reflecting it straight up turns it a full 90 degrees! Not something I would have expected. I also think it looks a bit more professional without the chrome mirror protruding from the front. The disc mask is also complete and installed, but appears a bit too tall so I may have to fine tune it with some vinyl electric tape.
There are still a few bugs to work out. The system will only sync to its internal generator, not an external signal. I did some probing and found that the internal waveform generator is set to a much higher output level (about 2.5v) than my Ipod or CD player can provide. This doesnt make sense since Ive used that same circuit in other monitors without a problem so I must have made a mistake with a resistor or something.
I'm still thinking of a way to get the timing LED to flash once per frame rather than once per line. I was initially thinking about using a monostable 555 triggered by the line pulse with a time constant of a little over one NBTV line. Only when the missing pulse comes around can it actually complete its cycle, thus generating a frame pulse. I'm not sure if it works that way, so maybe a multivibrator would be a better option?
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Postby Harry Dalek » Tue Mar 25, 2014 3:48 pm

Lawnboy wrote:I'm still thinking of a way to get the timing LED to flash once per frame rather than once per line. I was initially thinking about using a monostable 555 triggered by the line pulse with a time constant of a little over one NBTV line. Only when the missing pulse comes around can it actually complete its cycle, thus generating a frame pulse. I'm not sure if it works that way, so maybe a multivibrator would be a better option?


There are 2 ways

Yes the monostable idea as in this circuit or 1 hole just for that placed in the correct position on your Nipkow opto fork idea or use both is a PLL idea but the sample might be pointless for a mechanical system as the 31 or 32 pulses are more useful controlling a motor but if you just want to see a Led come on .

I like the mirror door good idea and will protect your lens when shut.
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Postby Lawnboy » Thu Mar 27, 2014 7:54 am

Thanks Harry. I will try to modify the circuit you sent. It seems like the easiest way to do things. Is that from a CRO converter?
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Postby Harry Dalek » Thu Mar 27, 2014 9:36 am

Lawnboy wrote:Thanks Harry. I will try to modify the circuit you sent. It seems like the easiest way to do things. Is that from a CRO converter?


Theres another from one of the news letters but its about the same uses same monostable chip i should try it my self on the current experiments .

Yes its from that scope monitor ,keep working on the camera looks good .
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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Postby Lawnboy » Mon Mar 31, 2014 9:03 am

I got an image! Last night I hooked everything up just to see if the photocell would respond to my hand waving in front of it. Right now the scanner and monitor are using different sync sources so I was just looking to see if the overall image brightness changed when I moved my hand around. As I powered it up, a strange white blob appeared through the interference patterns on my monitor. After carefully matching the frequencies on both sync generators I tried again, and there was my hand! I was also able to see several other objects that I placed in front of the scanner. The problem is that the image is drowned out by mains hum coming from the lamp, so I will have to build a rectifier to smooth its output. No pictures yet due to the lack of stable sync, but I should have some soon. A big step forward!
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Postby gary » Mon Mar 31, 2014 9:32 am

Lawnboy wrote:I got an image! Last night I hooked everything up just to see if the photocell would respond to my hand waving in front of it. Right now the scanner and monitor are using different sync sources so I was just looking to see if the overall image brightness changed when I moved my hand around. As I powered it up, a strange white blob appeared through the interference patterns on my monitor. After carefully matching the frequencies on both sync generators I tried again, and there was my hand! I was also able to see several other objects that I placed in front of the scanner. The problem is that the image is drowned out by mains hum coming from the lamp, so I will have to build a rectifier to smooth its output. No pictures yet due to the lack of stable sync, but I should have some soon. A big step forward!


Congratulations Byron, there is nothing like the feeling of seeing that first image!

Are you recording the signal into a PC? We would all like to see your results. If so may I suggest, if you haven't already done so, you take a feed of your sync pulse from the camera and make that the right channel of a stereo feed going into the PC - that way it is easy to timebase correct any speed variations on the disk - great for "debugging".
Perfecting an NBTV system is like trying to slam a revolving door...
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Postby Harry Dalek » Mon Mar 31, 2014 6:45 pm

Adding to the Congratulations you stuck to it and got it going !

I had a problem with mains hum but mine was because the lap top i use and i suppose they all are like that no earthing on the power supply when i tried earthing the mic plug that fixed it .

Any case please do as Gary already asked when you can post some camera experiments love to see them.
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Postby Lawnboy » Tue Apr 01, 2014 9:31 pm

Thanks guys. Yes, I do plan on uploading some clips once I get the noise situation figured out. Now that I've played around with it more, I think the noise is more EMI than hum coming through the lamp. The head amp is built dead bug style on a piece of copper clad board and placed in a small aluminum enclosure (see pics). Should the enclosure be electrically connected to the ground plane? Right now the amp is running from a 9v battery, so I don't think ground loops are the issue. I also modified the original circuit a bit, replacing the first BC109C with an MPSA18 and using a BC109C in place of the 2N3704.
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Postby Harry Dalek » Wed Apr 02, 2014 8:52 pm

Hi well in my case there was no earthing on the head amp because plugging it into the laptop it had no earthing ...
The head amp was fine while listening via a crystal ear phone so i could tell that wasn't the problem but when i plugged it into the laptop i was getting noise .

You should be fine if your using a desktop..if you are using those luxeons powered by mains AC i recalled a simple one i pulled apart they were in series with a circuit as you think it could be that .

Try your head amp with a crystal ear phone point it at the light in your scanner you should hear the mains hum if thats the problem if its clean you will hear that too you will know the difference.... .i recall the head amp could pick up a lights mains hum from a room the other end of the house

On the head amps light sensitive diode trany your using you might find areas lines brighter than others as the larger the surface area more even the light detection reason i used solar cells for the surface area it could detect more light raster lines more even than a tiny light S Trany.
i was using very low low light levels so was more than likely worse in my case.
Some thing that might be useful in your scanner would be perhaps a way to adjust the flying spot scanners light level you might find that easier due to your large light levels than adjusting the mixer circuit to get better shades ?
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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Postby Lawnboy » Thu Apr 03, 2014 9:30 pm

Thanks Harry, I will try the headphone trick. I don't have any crystal 'phones so I will have to make due with regular ones for now. I should also mention that the room was not completely pitch black during the test. There were a few indicator neon/LEDs scattered around and maybe a little street light leakage through the blinds but I would be very surprised if the amp picked those up. I know I wont have much time this weekend to work on it but hopefully I can find a few minutes this next week.
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Postby Harry Dalek » Thu Apr 03, 2014 10:11 pm

Lawnboy wrote:Thanks Harry, I will try the headphone trick. I don't have any crystal 'phones so I will have to make due with regular ones for now. I should also mention that the room was not completely pitch black during the test. There were a few indicator neon/LEDs scattered around and maybe a little street light leakage through the blinds but I would be very surprised if the amp picked those up. I know I wont have much time this weekend to work on it but hopefully I can find a few minutes this next week.


Just on the head amp its very interesting to hear it work via crystal ear phone ..turn your plasma on and all hell breaks loose ,fluros mains hum or raw more like it ..it will pick up streets light mains hum ,any light with something modulated on it even the lap tops screen it'll pick that up too.

If your Leds are flashing at a fast rate it might be that , good thing about the ear phone you can tell if you have a clean signal if you try it in a dark room pitch black you just get static , try turning a light on some where far from the room and open the door a bit you'll hear the hum of the mains.

It really is Dxing with light you'll see that when you experiment again with the scanner working move the head amp close and away from the object your filming it will fade in and out of the static .

I had to have my head amp with the solar cells as close as i could to what ever i was trying to film you should have better range than i had .

Good luck on the noise problem let us know how you go .
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: Flying Spot Scanner Construction Journal

Postby Lawnboy » Sun Apr 13, 2014 2:55 pm

Last weekend I got the noise issue figured out (all I had to do was ground the case and put it all together properly), and got both discs to lock to a common sync source, and now that the forum is back up and running its time to post some snapshots from my monitor! I was really impressed at the greyscale reproduction. I fully expected the images to be contrasty and harsh, but they are not, even with the gamma correction applied in the monitor. The photocell was taped to the top corner of the scanner so the light appears to come from above. The white blob in the images is the reflective hub of the Nipkow disc in the background. There is still some noise in the form of a wavy pattern when an object is present (not visible in the long exposure photos), no doubt noise from the lamp, which will have to be rectified. The photocell will pick up objects within about 4 or 5 feet, but beyond that it dims quickly. I am hoping a lens or reflector placed on the sensor will help with that. So far I am very satisfied with the results!
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Re: Flying Spot Scanner Construction Journal

Postby Harry Dalek » Sun Apr 13, 2014 8:26 pm

Lawnboy wrote:Last weekend I got the noise issue figured out (all I had to do was ground the case and put it all together properly), and got both discs to lock to a common sync source, and now that the forum is back up and running its time to post some snapshots from my monitor! I was really impressed at the greyscale reproduction. I fully expected the images to be contrasty and harsh, but they are not, even with the gamma correction applied in the monitor. The photocell was taped to the top corner of the scanner so the light appears to come from above. The white blob in the images is the reflective hub of the Nipkow disc in the background. There is still some noise in the form of a wavy pattern when an object is present (not visible in the long exposure photos), no doubt noise from the lamp, which will have to be rectified. The photocell will pick up objects within about 4 or 5 feet, but beyond that it dims quickly. I am hoping a lens or reflector placed on the sensor will help with that. So far I am very satisfied with the results!


Yes great results much better than i ever did !
Again due to the surface area solar cell gives you would collect heaps more light and a bit easier than that large flat lens that you might find in over head projectors but your results are great how far can you focus your raster , i was surprised by a pdf on FS television system i downloaded used on a plane i didn't think the Flying spot scanner idea was used apart from a studio .
I didn't know it was a camera monitor i should pay attention more are you going to mix the sync with video and record a file but no need to prove any thing here the video snaps are spectacular.
You should be very proud of the great work very very well done .
I am starting on a new project as well due to finding a old laser printer on a nature strip last week love those polygon mirrors !
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: Flying Spot Scanner Construction Journal

Postby Lawnboy » Tue Apr 22, 2014 5:37 am

This weekend I finished a rectifier to smooth out the ripples in the lamp brightness. It works, but I am concerned about the inrush current. I am using a 25A (@125v) 400 PIV full wave bridge rectifier with 2x470uF = 940uF 200WV filter caps and a 5W 22k bleeder resistor. The switches I am using are rated at 6A, but I wonder how long they will last while switching a 300W tungsten lamp along with the rectifier. Would it be better to leave the rectifier powered up even when the lamp is off?
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