Author Topic: What's wrong with my Electrophysics Micronviewer?  (Read 2583 times)

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Offline Bill W

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #25 on: June 11, 2021, 09:53:44 am »
My room lights are incandescent, so emit almost 100% visible light.

No, will be 5% visible and a lot of NIR through to LWIR 'heat'.

That is why a 10W LED is as bright as a 100W incandescent - 5W of heat vs 95W of heat

Offline Ultrapurple

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #26 on: June 11, 2021, 12:02:21 pm »
Many of the things you're experiencing are just down to the fact that it's a vidicon-based camera. In particular, the interference when your hand is near the front of the tube is perfectly normal. It's mainly down to the (necessarily) extremely high input impedance of the first video amplifier.

May I suggest you buy an old vidicon based security camera such as a Pye Lynx (or even the camera that the MicronViewer is based on) and experiment with that? Apart from the different frequency response a visible light vidicon camera will behave much the same as the NIR one, except that you won't care if you damage it.
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Offline Ben321

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #27 on: June 11, 2021, 10:51:39 pm »
or even the camera that the MicronViewer is based on

Wait. So there's also a visible-light version of the Micronviewer? What company made it. And what's its model number?
 

Offline Ben321

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #28 on: June 11, 2021, 10:53:56 pm »
My room lights are incandescent, so emit almost 100% visible light.

No, will be 5% visible and a lot of NIR through to LWIR 'heat'.

That is why a 10W LED is as bright as a 100W incandescent - 5W of heat vs 95W of heat

I made a big OOPS there. I meant to say since my room has LED lights INSTEAD OF incandecent lights. That's why I was able to verify that the specs that say this SWIR camera can also see visible light, are certainly correct. The lights in my ceiling emit nearly 100% visible light, because they are LEDs.
 
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Offline Ultrapurple

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #29 on: June 11, 2021, 11:23:20 pm »
or even the camera that the MicronViewer is based on

Wait. So there's also a visible-light version of the Micronviewer? What company made it. And what's its model number?

I believe I read on EEVblog that the MicronViewer was based closely on a CCTV camera but I can't remember which. A quick search should find the answer.

It doesn't surprise me that the camera can see in the visible spectrum:

The 7290A uses a PbS coated Vidicon tube and has a bandwidth of 0.4um to 1.9um.

0.4um is violet, verging on UV. The tricky thing with the MicronViewer is keeping visible light out - an 850nm or 950nm screw-in photographic-type filter from eBay is a good place to start. Expect to pay <US$20, but do be careful to get the right physical size to screw into the front of the lens (ie not the tube end). 850nm is usually cheaper than 950 - I don't know why - but I do think you will get better imaging 'value' from a 950nm filter.

I have done a lot of playing with 700, 750 and 850nm filters on 'full-spectrum' DSLRs and the world does look different with the different filters. Have a look here for a few sample images taken with these filters. There is no benefit in paying top dollar for a top brand filter: the resolution of the Micronviewer is far lower than even the shoddiest filter's performance.

Why 950nm? A 'full-spectrum' digital camera with a silicon sensor will respond down to almost 1.1um so by putting onto the MicronViewer a low pass filter as close as you can get to the silicon cutoff, the less overlap you will get. 'Full-spectrum' DSLRs are fairly easy to obtain, or you can just (destructively) modify a used camera. I use a converted Nikon D600 as my main full-spectrum camera, but I also have a couple of Fuji IS Pro bodies.
« Last Edit: June 11, 2021, 11:40:57 pm by Ultrapurple »
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Offline _Wim_

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #30 on: June 12, 2021, 05:57:33 am »
I believe I read on EEVblog that the MicronViewer was based closely on a CCTV camera but I can't remember which. A quick search should find the answer.

Yes, at least the 7290 (non A version) I got is based on the ITC510 CCTV camera: https://www.eevblog.com/forum/thermal-imaging/swir-electrophysics-micronviewer-7290a-user-manual/msg3265658/#msg3265658

As to seeing in the visible spectrum, these camera's are essentially a vidicon based camera, where the vidicon has an improved sensitivity (see attached datasheet) towards the IR, but they operate as a "normal" vidicon in the visible. That is why it can be very useful to install a long pass filter on the camera lens.
 

Offline Ben321

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #31 on: July 08, 2021, 05:27:47 am »
I believe I read on EEVblog that the MicronViewer was based closely on a CCTV camera but I can't remember which. A quick search should find the answer.

Yes, at least the 7290 (non A version) I got is based on the ITC510 CCTV camera: https://www.eevblog.com/forum/thermal-imaging/swir-electrophysics-micronviewer-7290a-user-manual/msg3265658/#msg3265658

As to seeing in the visible spectrum, these camera's are essentially a vidicon based camera, where the vidicon has an improved sensitivity (see attached datasheet) towards the IR, but they operate as a "normal" vidicon in the visible. That is why it can be very useful to install a long pass filter on the camera lens.

Wait, there's a non-A version? I know there's a standard version of the Micronviewer (with model number which ends with an A), and an extended wavelength model that can see beyond 2000nm (which ends with an A-EX if I remember correctly, with EX meaning extended). I never knew a model ever existed without the A at all.
 

Offline Ben321

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #32 on: July 08, 2021, 05:52:07 am »
On another note, this camera DOES appear to require a 50ohm impedance on the TV (or video-capture card) to work correctly. In order to try to further debug my Micronviewer (read some of the various problems I've encountered, even after getting a working power supply, on the first page of this thread), I decided to connect the camera up to my Picoscope. Even though I bought the cheapest Picoscope, which has a theoretical maximum sample rate of 1 million smp/sec, I found it has an actual maximum sample rate of 6.25 million smp/sec. This lowers the horizontal resolution I'm able to capture at (about 395 total pixels per line including all h-sync and blanking, with only about 325 image pixels per line). However, this is still plenty of pixels to get a good idea of what an image should look like. After using my Picoscope as a high speed digitizer to capture raw samples to a WAV file (using my own custom Picoscope recorder software that pushed the Picoscope to its maximum possible samplerate, which the official software doesn't do), I used Goldwave audio editor to center the signal values on the blanking level, and then used some of my own custom software to read the sync pulses to get all the lines to line up (end result looks like a film strip with many pictures), and then loaded that into Gimp's raw image viewer and cropped the result to be the size of a single field (I didn't do any interlacing to get a frame, just cropped it to a single field).

The result, while not as good as a dedicated video capture card, still should give a good idea of what you would see on a TV (and has for many other video sources I've used this technique with). But it didn't. I have captured many pics using a USB video capture dongle (that's how I got the pics from the first page), and what I saw from this Picoscope capture shows no similarity in the image content. The sync and blanking areas are correct, but the image content area is messed up real bad. I suspect this is because my Picoscope is a high-impedence input (I think it's 1MOhm) while I know that video signal sources expect to be connected to a low input impedance device (usually about 50 Ohms), and some (like this camera it seems) will not even generate a usable image UNLESS they are connected to a low input impedance device.

I've attached the picture captured using my above described method to this post.

Do you know if there's a 50 Ohm BNC or RCA adapter I could get, that is designed to go between an oscilloscope and a video signal source? It would be like a normal coaxial adaptor or extender, except instead of having a completely isolated pin connector and outer shield connector, it would have a 50 Ohm resistor between the center pin and the outer shielding connector, to give it the 50 Ohm DC resistance that video signal sources are usually plugged into (allowing all video signal sources to work with high-impedance input oscilloscopes).

 

Offline DaJMasta

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #33 on: July 08, 2021, 06:16:56 am »
Video signals are typically 75 ohms, and this one should be no exception.  I'd put a T connector on the scope input and a 75 ohm termination one one side, then the camera input into the other.  If you need to capture the video output as well, the video receiver should take care of the termination, so you'd just want your scope in a high impedance input mode.  If your picoscope is really only getting that low of a samplerate, its input bandwidth is probably too low for the signal and subsequently the input capacitance too high to capture the signal properly - a video signal could take up to 6MHz of bandwidth (don't think this one goes that high), so to make sure your measurement  instrument isn't effecting signal quality too much, I'd probably look for a minimum 50MHz bandwidth frontend with a 1M ohm or more rated input.  Overkill from what's required, but good enough that you shouldn't have any significant video detriment from the frontend of your scope.
 

Offline Ben321

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #34 on: July 08, 2021, 08:25:36 am »
Video signals are typically 75 ohms, and this one should be no exception.  I'd put a T connector on the scope input and a 75 ohm termination one one side, then the camera input into the other.  If you need to capture the video output as well, the video receiver should take care of the termination, so you'd just want your scope in a high impedance input mode.  If your picoscope is really only getting that low of a samplerate, its input bandwidth is probably too low for the signal and subsequently the input capacitance too high to capture the signal properly - a video signal could take up to 6MHz of bandwidth (don't think this one goes that high), so to make sure your measurement  instrument isn't effecting signal quality too much, I'd probably look for a minimum 50MHz bandwidth frontend with a 1M ohm or more rated input.  Overkill from what's required, but good enough that you shouldn't have any significant video detriment from the frontend of your scope.

Thanks. I just ordered those now on Digikey. It should take 4 days for shipping it said, so when I get it I'll let you know the results.
 

Offline Fraser

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #35 on: July 08, 2021, 11:14:34 am »
I have resisted commenting on this thread as there are other forum members with far more practical knowledge of this camera than me. I will, however, make few comments now….

The first sample picture you showed us displays a rotated rectangle. That is image burn and, at fist look, appears to be a rectangular mask created geometric burn with the imaging Vidicon tube having been rotated after the burn occurred. I then thought more about this and it could just be that he camera spent its life observing a rectangular test table and the tables image has burnt into the cameras target. The correct Vidicon tube orientation may be checked as detailed in the data sheets. Vidicon tubes are designed to be orientated in a certain way within the deflection yoke.

The images produced by your camera appear reasonably good with only the unusual vignetting on the left hand side causing concern. Please check the camera with the filter cartridge removed from its slot ro ensyre that he filter cartridge is not causing the problem though incorrect positioning in its carrier. That vignetting has the appearance of such a circular filter holder misalignment.

The camera is supposed to be 75 Ohm output impedance and too high an impedance just causes the amplitude of the signal to increase beyond the specification for a standard composite video signal. The effect of this is to really mess up the video signal image content when recorded by a video capture system.

The Micron viewer was originally released as the 7290 model and it was basically a modified commercial Ikegami CCTV camera. As the Vidicon tube of a CCTV camera and SWIR camera have similar needs this was an obvious path for Electrophysics to take and saved development time.

The 7290 appears to have existed with at least two different ‘Donor’ CCTV camera platforms as might be expected as models became obsolete. The 7290A appears to be a completely new custom camera design, likely built under contract for Electrophysics when the original ‘Donor’ CCTV cameras became obsolete and no new models were released due to the introduction of CCD digital imaging technology. The 7290A model uses more modern components in its design and it was the same hardware up until the camera was discontinued. The 7290A could be fitted with the standard or extended range SWIR Vidicon tube as you know and there was also a handheld portable version that was battery powered and fitted with an electronic viewfinder….. much like very early monochrome home video camera systems.




« Last Edit: July 08, 2021, 04:52:48 pm by Fraser »
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Offline Ben321

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #36 on: July 08, 2021, 08:55:36 pm »
I have resisted commenting on this thread as there are other forum members with far more practical knowledge of this camera than me. I will, however, make few comments now….

The first sample picture you showed us displays a rotated rectangle. That is image burn and, at fist look, appears to be a rectangular mask created geometric burn with the imaging Vidicon tube having been rotated after the burn occurred. I then thought more about this and it could just be that he camera spent its life observing a rectangular test table and the tables image has burnt into the cameras target. The correct Vidicon tube orientation may be checked as detailed in the data sheets. Vidicon tubes are designed to be orientated in a certain way within the deflection yoke.

The images produced by your camera appear reasonably good with only the unusual vignetting on the left hand side causing concern. Please check the camera with the filter cartridge removed from its slot ro ensyre that he filter cartridge is not causing the problem though incorrect positioning in its carrier. That vignetting has the appearance of such a circular filter holder misalignment.

The camera is supposed to be 75 Ohm output impedance and too high an impedance just causes the amplitude of the signal to increase beyond the specification for a standard composite video signal. The effect of this is to really mess up the video signal image content when recorded by a video capture system.

The Micron viewer was originally released as the 7290 model and it was basically a modified commercial Ikegami CCTV camera. As the Vidicon tube of a CCTV camera and SWIR camera have similar needs this was an obvious path for Electrophysics to take and saved development time.

The 7290 appears to have existed with at least two different ‘Donor’ CCTV camera platforms as might be expected as models became obsolete. The 7290A appears to be a completely new custom camera design, likely built under contract for Electrophysics when the original ‘Donor’ CCTV cameras became obsolete and no new models were released due to the introduction of CCD digital imaging technology. The 7290A model uses more modern components in its design and it was the same hardware up until the camera was discontinued. The 7290A could be fitted with the standard or extended range SWIR Vidicon tube as you know and there was also a handheld portable version that was battery powered and fitted with an electronic viewfinder….. much like very early monochrome home video camera systems.

The amplitude is not actually exceeding the specs of my scope. It maybe in the camera itself overdriving some kind of limiter circuit, but on the scope end it wasn't overdriving anything.


As for the images captured with a video capture dongle, I'm not so sure that the vignetting is caused by the misalignment of the filter holder, because when I remove the lens the filter hole appears exactly centered. My hypothesis is that it's an H-Offset adjustment issue with the deflecting coil.

Another issue I notice is at the left edge of the image where it fades out has a serrated edge to it, not just following the contour of the darkest parts of the image.

Also there appears to be a signal gain/offset issue in the image. where even the darkest parts of the image (even with the lens cap in place) aren't actually black. Instead they always are above black as a dark gray. The only part that is truly black is outside of the actual image (just to the left of where the vignetting is occurring on the left side of the image).
 

Offline Ben321

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #37 on: July 13, 2021, 11:38:47 pm »
So just an update now. I have done some repair work on the camera itself.
See this picture uploaded previously for reference to what the image was like before repairs.
https://www.eevblog.com/forum/thermal-imaging/whats-wrong-with-my-electrophysics-micronviewer/?action=dlattach;attach=1226891;image
Notice that the actual image is offset to the right of the frame.
Notice that edge of the vignetting isn't circular, but instead suddenly drops from gray to black, where the darkness of the image is too low, which depends on not only vignetting but also image content, making an irregularly shaped vignetting area.
Notice how the edge of the left edge of the image, where it drops into vignetting, has a serrated look to it (kinda like the teeth on a comb) instead of simply being a normal edge.

As for the repairs, my first one was to correct the horizontal offset of the electron beam. My hunch was that the reason the picture was shifted too far to the right, was more than just a lens miss alignment. The filter tray wasn't pushing the lens or anything, although the lens itself (if it had maybe been dropped by the previous owner, as I bought the lens with another CCTV camera on eBay) could have its internal optics slightly out of alignment. However, I figured that even that optical missalignment wouldn't account for such a large image offset as I was observing here. So I went with my hunch that the reason the image appeared too far to the right was that the electron beam was scanning to far to the left, and so I adjusted the H-center potentiometer to move the image to the right. My hunch was correct! I was able to bring the right part of the image back into the frame, something that would not have been possible if the lens was simply out of alignment, and the lens was projecting the image onto the tube's surface outside of the light sensitive area. I didn't completely recenter it though (just pretty close to center, enough to see the full right side of the actual image), because this lens is used and does have trouble focusing as good as it should (though it does focus pretty good), and so some of the optics in the lens may be slightly out of alignment (thus somewhat contributing to the horizontal offset issue), and I don't want to accidentally overcorrect for horizontal offset using the electron beam scanning controls, because if I get a new lens that's better quality, I don't want to need to re-correct the horizontal offset again.

My next repair was to fix the strange brightness issues that caused the brightness of a given pixel to jump from gray suddenly to black when the amount of light exposing that pixel was too low. For this I adjusted the black pedestal potentiometer (which I suspected I needed to do. Black pedestal refers to the 7.5 IRE offset for black above blanking level (0 IRE) in the NTSC specification. I had a lot of trouble with getting it set, because for this to be set, I needed to keep the image black, but even a capped lens wouldn't have worked for this, because with the case off (needed to adjust the potentiometer) the tube was still exposed to light. I eventually gave up on this effort, put the black pedestal potentiometer back to where it was to start with, and decided to close the case, just being happy that I'd recentered the image.

After putting the case back on and testing it, I noticed if I bumped the case by accident (for example while handholding the camera and pointing it around at different things, but accidentally bump it into something nearby) the image would flicker briefly with horizontal lines through it, and sometimes the overall image brightness would change (sometimes for just a second, but other times it would stay at a new brightness level). And it didn't even need to be a hard tap. Any kind of momentary mechanical force, a "bump" (but not a constant pressure being applied to the case), even if only a very LIGHT TAP, was able to cause this. This seemed to indicate that SOMETHING is loose SOMEWHERE (hopefully not a bad solder point, because I would never try to do a solder repair on something this rare and valuable, because it could be broken even worse if I made any mistakes). This issue of what must be a loose connection somewhere, has actually been an issues since I first powered on the camera to test it after I bought the replacement power supply for it.

I thought to myself then, I wonder what happens if I INTENTIONALLY tap it, will that flickering get better or worse? So I tried tapping the case several more times, and the coolest thing happened after I stopped tapping it after the last tap. I noticed that ALL of the remaining issues were gone! No more sudden dropoff from gray to black. Vignette was now perfectly circular. And the left edge of the image was no longer a serrated edge like the teeth on a comb. Just like in a movie, where somebody gives a few whacks to a broken piece of equipment, and it suddenly starts working, this ACTUALLY WORKED IN REAL LIFE for this camera!

Of course, if there's a loose connection still, this may have temporarily made the connection better, but I wonder how loose the connection is, and if it's still loose, how strong of an accidental tap will it take to bring back the same problems I fixed by intentionally tapping the case. Whatever the case, I immediately captured a picture from it just after getting it fully working, and I've attached that picture to this post.
 

Offline Bill W

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #38 on: July 14, 2021, 09:20:36 am »
Of course, if there's a loose connection still, this may have temporarily made the connection better, but I wonder how loose the connection is, and if it's still loose, how strong of an accidental tap will it take to bring back the same problems I fixed by intentionally tapping the case. Whatever the case, I immediately captured a picture from it just after getting it fully working, and I've attached that picture to this post.

Good to see it looking a lot better.

The problem could be a bad pot.  The images you posted show rather prehistoric open frame carbon track pots. They can get very 'noisy' and touch sensitive over time.

Bill

Offline Fraser

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #39 on: July 14, 2021, 12:05:17 pm »
Not wanting to cause unwarranted concern but I have seen similar ‘image offset’ behaviour in cathode Ray tubes that have been dropped in transit. The cause of the offset was found to be a misaligned electron gun that was no longer in correct axial alignment with the tube body. The electron gun is often mounted on a combination of stiff wire and glass supports that form a cage on which the various parts of the electron gun and associated grids are mounted. If a cathode Ray or Vidicon tube are exposed to a drop event that does not result in implosion, the whole ‘cage’ that supports the electron gun can shift downwards towards the point of impact due to kinetic energy.
You may be able to correct fir this gun offset with the positioning controls that act upon the deflection coils and it would appear that you have been able to do so in this case.

Regarding intermittent connections in equipment….. there is an age old technique fir finding such…… use a small plastic handled screwdriver …. Hold it by the metal tip and use the insulated handle as a miniature hammer to gently tap the the PCB’s in a methodical manner working across their surface and monitoring the effect on a display. Some microphony  is normal. The vidicon tube may be tested in a similar manner by tapping its deflection you’re gently. Vidicon tubes are microphonic so you will see some weird effects on the image and this is normal. This technique will often identify an area of a PCB that is sensitive to vibration and may contain a dry joint or failed component. It is also worth removing the Vidicon tube from the deflection yoke and visually inspecting the electron gun end of the tube and the target contact that is mounted at the front of the deflection yoke assembly.
« Last Edit: July 14, 2021, 12:07:29 pm by Fraser »
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Offline Fraser

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #40 on: July 14, 2021, 12:11:12 pm »
Last comment…. As you likely already know, your current lens is designed for a small sensor so you are seeing vignetting. You need a lens that is designed for a 1” Vidicon tube but you may get away with one designed for a 3/4” tube as well. I found the 25mm 1” Vidicon tube compatible lens to be the most easily obtained. Anything smaller, like 12mm or 8mm  is often designed for a 3/4” or smaller tube.
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Offline Fraser

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #41 on: July 14, 2021, 12:25:55 pm »
For information… pictures of the internal electron gun arrangement in camera tubes…..

They are quite robust in terms of alignment but they are not designed to withstand ‘drop event’ impacts.
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Offline Ben321

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #42 on: July 15, 2021, 09:56:28 pm »
On another note, this camera DOES appear to require a 50ohm impedance on the TV (or video-capture card) to work correctly. In order to try to further debug my Micronviewer (read some of the various problems I've encountered, even after getting a working power supply, on the first page of this thread), I decided to connect the camera up to my Picoscope. Even though I bought the cheapest Picoscope, which has a theoretical maximum sample rate of 1 million smp/sec, I found it has an actual maximum sample rate of 6.25 million smp/sec. This lowers the horizontal resolution I'm able to capture at (about 395 total pixels per line including all h-sync and blanking, with only about 325 image pixels per line). However, this is still plenty of pixels to get a good idea of what an image should look like. After using my Picoscope as a high speed digitizer to capture raw samples to a WAV file (using my own custom Picoscope recorder software that pushed the Picoscope to its maximum possible samplerate, which the official software doesn't do), I used Goldwave audio editor to center the signal values on the blanking level, and then used some of my own custom software to read the sync pulses to get all the lines to line up (end result looks like a film strip with many pictures), and then loaded that into Gimp's raw image viewer and cropped the result to be the size of a single field (I didn't do any interlacing to get a frame, just cropped it to a single field).

The result, while not as good as a dedicated video capture card, still should give a good idea of what you would see on a TV (and has for many other video sources I've used this technique with). But it didn't. I have captured many pics using a USB video capture dongle (that's how I got the pics from the first page), and what I saw from this Picoscope capture shows no similarity in the image content. The sync and blanking areas are correct, but the image content area is messed up real bad. I suspect this is because my Picoscope is a high-impedence input (I think it's 1MOhm) while I know that video signal sources expect to be connected to a low input impedance device (usually about 50 Ohms), and some (like this camera it seems) will not even generate a usable image UNLESS they are connected to a low input impedance device.

I've attached the picture captured using my above described method to this post.

Do you know if there's a 50 Ohm BNC or RCA adapter I could get, that is designed to go between an oscilloscope and a video signal source? It would be like a normal coaxial adaptor or extender, except instead of having a completely isolated pin connector and outer shield connector, it would have a 50 Ohm resistor between the center pin and the outer shielding connector, to give it the 50 Ohm DC resistance that video signal sources are usually plugged into (allowing all video signal sources to work with high-impedance input oscilloscopes).

Regarding the above quoted post, and its attached picture, I have now gotten a BNC T adapter and a 75ohm BNC terminator. When using the same technique to get an image from the raw signal from the Picoscope I still get some kind of waveform added to the image (in the actual picture portion of the video signal), but less strong now, and also at a higher frequency than before. I've attached an image of the captured frame (or more accurately the first field of the frame). As with before, the width of the image is limited to only about 300 pixels wide, due to the lower than ideal sample rate of 6.25 MSPS. This also could be adding in some unfortunate lower frequency noise if there are strong, instead of weak, signals near the upper part of the video signal's bandwidth, because it would be at a frequency greater than the nyquist limit of the scope, and thus the frequency would appear to be lower than it actually is. The only real way around this issue, is to get a more expensive Picoscope with a wider bandwidth. The specs on my Picoscope (which is the cheapest one) is that it officially has a maximum samplerate of 1 MSPS, but I contacted someone there and they told me it could be pushed up to 6.25MSMP but would likely drop some buffers because of the scope's small internal memory (a problem I haven't had on my computer, which appears to be because my computer is fast enough to get the data before the scope's hardware buffer overflows). However, even at 6.25 MSPS, the nyquist limit is less than the highest possible frequency from a video signal following NTSC specifications.

By the way, I noticed in the spectrogram for this signal that there's a strong wideband signal appears in the middle of the spectrum, so it is at about 1.5 times the nyquist frequency (3 quarters of the sample rate) of my Picoscope.
« Last Edit: July 15, 2021, 10:06:58 pm by Ben321 »
 

Offline Ben321

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #43 on: July 15, 2021, 10:21:36 pm »
Then I remembered something important. My Picoscope has a 6.25MSPS limit for streaming mode (capturing a long signal up to several seconds). But it has a higher limit for triggered block mode (only sending a buffer of data when there's a trigger, instead of as fast as possible). This mode will miss things between buffers during the trigger reset period, but it can run much faster. And Picoscope official software itself can use this mode quite well and display the graph. This mode runs much faster easily capturing signal at 500ns per division (with 10s of samples per division, so the sample rate is very high). In this mode I can see that the video signal's image data is NOT a continuously varrying voltage level, but instead it seems a series of PULSES. are these being sent at the rate of the camera's pixel clock? Not sure, but the video image signal is definitely chopped up. Here's a screenshot of the signal in the official Picoscope software.

Any idea what might be causing this? Is this a defect in the camera?
 

Offline Ben321

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #44 on: July 16, 2021, 07:57:57 pm »
Given the pieces of textual information and attached images that I've provided in the last 2 posts, is there anybody here with enough technical knowledge of vidicon tube camera techonlogy, that they would be able to diagnose the latest problem issue I've noticed with my camera? It is an issue with the video signal output from the camera that only becomes obvious when actually measuring the signal with an oscilloscope (even with a 75ohm resistor in parallel with the scope's input). My USB video capture dongle has NO PROBLEM with this. What I'm noticing is that in the image portion of the signal (not blanking or syncing portions), there appears to be a series of pulses at a frequency that I'm guessing must be near the pixel clock frequency. These pulses also I've observed have TWICE the voltage that they should for a given optical input to the camera. For example, in a region that's pure white, which should have a signal voltage of 0.7 volts, I'm observing on my oscilloscope a voltage of about 1.4 volts! And, yes the scope does have its 75ohm resistor in place on a T adapter (white voltage pulses would have been about 2.8 volts without that adapter).

I think that my camera must be expecting some kind of capacitance across the input of the video input device it's connected to, and that capacitance would average out the pulses, creating a constant signal with half the amplitude of the pulses. Do most video input devices have a smoothing capacitor across their input like that? I knew about the 75 ohm parallel resistance, but was unaware of any parallel capacitance that would be required for monitoring the output of a video camera with an oscilloscope.

Can somebody here tell me what is going on? Is this just a defective camera? Is there actually supposed to be a signal smoothing capacitor across the output of the camera, inside the camera, but the capacitor is broken?
« Last Edit: July 16, 2021, 08:08:16 pm by Ben321 »
 

Offline Ben321

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #45 on: July 17, 2021, 08:34:44 am »
Come on people. SOMEBODY HERE must know what's going on with the signal here. I even posted a screenshot showing its strange waveform in my Picoscope software. Yet nobody seems to be able, or willing, to help here. And that's despite the fact that I was SURE that with all the people here with extensive technical knowledge, that SOMEBODY would be able to help me. Yet NOBODY seems to be able to. Or maybe its just my long paragraphs are making you not want to read them? Well guess what. Those long paragraphs are long, because they contain IMPORTANT INFORMATION regarding my latest issue. Lots and lots of important information, that you will need to read to fully understand my latest issue. And you will need to understand my exact issue if you are going to help me. So please don't just run away because you see a long paragraph. I NEED YOU GUYS' HELP to fix this latest issue.
 

Offline Fraser

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #46 on: July 17, 2021, 11:24:46 am »
Before anyone can help you they need reliable, trustworthy, data to analyse. We currently do not have enough accurate data to comment.

Some food for thought…..

1. Does the camera display a normal image on a monitor without any evidence of herring bone pattern or noise bars ? If so, why do you think you are not seeing the unusual signal that you think you have from your oscilloscope readings ? Are those oscilloscope readings trustworthy ?

2. Attach your oscilloscope to the video output of another camera, video recorder or other trustworthy source of a known good video signal. Capture the signal and analyse it by comparing to the many examples of a baseband video signal that are available on the internet (use Google to find them) Only when we are certain that your Oscilloscope system is giving you readings that may be trusted will we be able to comment on them.

3. People have busy lives and we cannot spend time analysing other people’s electronic issues if we are not confident that the supplied data is accurate. We need to see a complete picture. In this case I would want to see a complete oscilloscope image of a line scan and field scan waveform in order to assess the signal. I would also expect the oscilloscope used for such to have adequate bandwidth and sampling rate for a 6MHz complex signal..

I would not spend time analysing a partial signal of unknown validity as that could just waste my time and does not help you if incorrect assumptions are made by me about what I am seeing.

I strongly suggest that you spend some time on eBay and find a decent 20MHz Analogue oscilloscope as these are quite common and inexpensive. An analogue oscilloscope rarely lies to you and is a great general purpose test instrument. A DSO introduces the challenge of both true bandwidth and sampling rate. If the Sampling rate is inadequate you basically get an inaccurate display of a signal. You need the decent sampling rate for single shot complex signals and not the over sampling spec for signals that do not change. For video work I would want a DSO with at least 60 Ms/s true, single shot, real time sampling rate.

Please analyse your cameras image and if there is no evidence of unusual ‘noise’ then suspect your oscilloscope captures as potentially invalid.

The change in video signal amplitude is interesting however. A video signal needs to stay within the video standard if a monitor is to correctly display it. An incorrect video signal level would certainly be worth further investigation.
« Last Edit: July 17, 2021, 05:07:23 pm by Fraser »
Cogito, ergo sum
 

Offline Ben321

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #47 on: July 17, 2021, 08:54:19 pm »
Before anyone can help you they need reliable, trustworthy, data to analyse. We currently do not have enough accurate data to comment.

Some food for thought…..

1. Does the camera display a normal image on a monitor without any evidence of herring bone pattern or noise bars ? If so, why do you think you are not seeing the unusual signal that you think you have from your oscilloscope readings ? Are those oscilloscope readings trustworthy ?
Mostly normal image on a TV or video capture card, but I have seen some vertical bar noise on the camera at times (usually just to the right of a very bright area in the image), and very prominently over the entire image with the case off (which is necessary to make potentiometer adjustments). Usually it's not a problem for normal viewing (so long as the case remains on), but that still doesn't mean that the signal is in spec for an NTSC video signal source. It just means that so far the display I've tested it on and the dongle I've tested it on have not had a problem with the out-of-spec signal, because it was "close enough" that the dongle could compensate. By the way, there's one semi-professional dongle I tried to use, but it never detected the signal. It definitely is built to exact NTSC specs, and expects any sources connected to it to also use proper NTSC specs. It rejects any signals out of spec. And that was a $200 USB video capture device from the professional video equipment company Black Magic Design. The funny thing is the dongle that did work actually was a cheap dongle I bought for like $5 at a yard sale, and comes from some company called SIIG that I'd never heard of before. I just Googled that cheap dongle, by the way, and found the dongle in question costs $50 from SIIG's own website, but that's still only one quarter the cost of the more expensive one.

2. Attach your oscilloscope to the video output of another camera, video recorder or other trustworthy source of a known good video signal. Capture the signal and analyse it by comparing to the many examples of a baseband video signal that are available on the internet (use Google to find them) Only when we are certain that your Oscilloscope system is giving you readings that may be trusted will we be able to comment on them.
I have never before had an issue with another NTSC video signal source on my PicoScope. The high frequencies are always weaker than the low frequencies (due to the camera having a proper lowpass filter that blocks frequencies above about 4.5MHz and attenuates signals smoothly up to that point (the higher the frequency the lower the amplitude, evidence of a simple RC filter, as every video source is supposed to have on its output to band-limit the signal), so even if the signal bandwidth exceeds the nyquist frequency this would only add a small amount of low amplitude medium frequency noise to the rest of the signal. This Micronviewer is either designed well out of spec for the NTSC signal bandwidth, or has drifted out of spec overtime. I hope to put it back in spec.

3. People have busy lives and we cannot spend time analysing other people’s electronic issues if we are not confident that the supplied data is accurate. We need to see a complete picture. In this case I would want to see a complete oscilloscope image of a line scan and field scan waveform in order to assess the signal. I would also expect the oscilloscope used for such to have adequate bandwidth and sampling rate for a 6MHz complex signal..
Good point. I'll probably end up buying a better Picoscope at some point, but the one that would best capture the full bandwidth of an NTSC signal costs about $1200. I'm not quite ready to spend that much money yet, but probably will sometime later. My current Picoscope is the cheapest one, and cost about $120.

I would not spend time analysing a partial signal of unknown validity as that could just waste my time and does not help you if incorrect assumptions are made by me about what I am seeing.
Fair enough.

I strongly suggest that you spend some time on eBay and find a decent 20MHz Analogue oscilloscope as these are quite common and inexpensive. An analogue oscilloscope rarely lies to you and is a great general purpose test instrument. A DSO introduces the challenge of both true bandwidth and sampling rate. If the Sampling rate is inadequate you basically get an inaccurate display of a signal. You need the decent sampling rate for single shot complex signals and not the over sampling spec for signals that do not change. For video work I would want a DSO with at least 60 Ms/s true, single shot, real time sampling rate.
Unfortunately I have a space issue. I don't have enough space for any more large devices in my room, like an analog CRT oscilloscope. And I can't exactly put my equipment outside of my room. My room is my bedroom, and I am living in an apartment with my parents, so the only place for me to store my personal equipment is in my own bedroom.
« Last Edit: July 17, 2021, 08:57:18 pm by Ben321 »
 

Offline Bill W

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #48 on: July 17, 2021, 09:52:35 pm »

I have never before had an issue with another NTSC video signal source on my PicoScope. The high frequencies are always weaker than the low frequencies (due to the camera having a proper lowpass filter that blocks frequencies above about 4.5MHz and attenuates signals smoothly up to that point (the higher the frequency the lower the amplitude, evidence of a simple RC filter, as every video source is supposed to have on its output to band-limit the signal), so even if the signal bandwidth exceeds the nyquist frequency this would only add a small amount of low amplitude medium frequency noise to the rest of the signal. This Micronviewer is either designed well out of spec for the NTSC signal bandwidth, or has drifted out of spec overtime. I hope to put it back in spec.



The image looks like a video instability, maybe caused by having the laptop and picoscope connected.  The tube signal is only a few nA into meg-ohms.

As for not being detected by a 'strict' video dongle, I would be more suspicious of the sync timing than the vertical amplitude.  The vidicon era thermals were all mono (RS-170 not NTSC) and might use a 'close enough' sync generator at relatively low clock rate. 
What is the sync generator and crystal ?
CD22402 known not to be great.

Offline Ben321

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Re: What's wrong with my Electrophysics Micronviewer?
« Reply #49 on: July 17, 2021, 10:19:25 pm »
The image looks like a video instability, maybe caused by having the laptop and picoscope connected.  The tube signal is only a few nA into meg-ohms.
My Picoscope has a BNC T-adapter with 75ohm terminator resistor connected to it now, so the camera no longer sees the Picoscope as a high impedance load, and while that has improved it, it hasn't fixed it. Do most vidicon era cameras expect to have a smoothing capacitor in parallel with the load, either at the camera end or load end of the coaxial cable?

As for not being detected by a 'strict' video dongle, I would be more suspicious of the sync timing than the vertical amplitude.  The vidicon era thermals were all mono (RS-170 not NTSC) and might use a 'close enough' sync generator at relatively low clock rate. 
What is the sync generator and crystal ?
CD22402 known not to be great.

I have no idea what the sync signal source is for an Electrophysics Micronviewer. There's a couple ways the level could be an issue. If the level is too high, the capture dongle might intentionally reject the signal due to it thinking it's not a valid video signal. Also since using pulses of too high of a level (though usually outside of the picture area, unlike from my camera where they are inside the picture area) is a technique used by Macrovision for copyprotection, and since modern consumer video capture equipment is required by copyright law to respect copyprotection signals, it could be mistakenly seeing the out-of-spec image signal levels as being copyprotection signals, and thus refusing to capture the signal.

As for the difference between RS-170 and NTSC, the fact is that NTSC was actually developed to be compatible with RS-170 (using 59.94Hz field rate instead of 60Hz field rate) so that NTSC color video would still be viewable on older monochrome TV sets. So even a strict NTSC video capture device should not be so strict as to block RS-170 monochrome signals. If it's that strict, that seems like a defect in the capture device, or possibly that the camera itself is outputting a signal that as well out of spec for either NTSC or RS-170.
« Last Edit: July 17, 2021, 10:24:32 pm by Ben321 »
 


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