SWIR Electrophysics Micronviewer 7290A - User manual ?

[_Wim_]

An interesting side comment, the Electrophysics 7290 and 7290A apparently have some military sensitivity dating back to when the N2606 tubes were used in military applications. Sadly such information restrictions can remain in place long after any real sensitivity has passed into history. This may be why the data sheet fir the Hamamatsu N2606 vidicon cannot be found on the web ?. EBay will not let me list the Electrophysics 7290A in the U.K. and state that it is on the U.S. Military list and only allowed to be advertised in the U.S?A with no export permitted !

That is crazy! I have seen many modern SWIR Ingaas cameras listed on Ebay with much higher resolution and sensitivity (and unfortunately also much higher price), and these were available worldwide.

A nice example is found here: https://www.benl.ebay.be/itm/NIT-WiDy-Sens-cooled-InGaAs-camera/274520123080?hash=item3feaaca6c8:g:Cn8AAOSw0MpfeYXh

A "bit" above my budget however...

[Fraser]

I agree.

EBay seem to have some text filter on item titles that checks against a restricted items list. The title “Electrophysics  7290A” triggered a statement that the item was on a Military controlled products list ! I even tried different titles but the 7290A bit still triggered the listing rejection. That was a first in my experience and I bought the camera from France via eBay !

Fraser

[_Wim_]

These 2 have just popped up:

https://www.benl.ebay.be/itm/Set-of-2-Electrophysics-7290-7290A-Micronviewer-Untested-For-parts-C485DS/233739306838?hash=item366bf2c756:g:WfwAAOSwM7tfBgw8

Title also includes "7290A" and export IS possible. Ebay sometimes acts very strange (also the search function)! Maybe it is ok if listed "for parts" 

[_Wim_]

@Fraser, just I quick question, the user manual you posted states "Decay lag after 50msec:45-60%". I interpreted this as the time constant is 50ms (1 decay time constant is around 60%), and that after 5 time constant the image would be fully updated (so 250 to 300ms for a full update)

In my camera (which uses the same tube, and normally this spec would be tube related) it takes more than 3 seconds, so I expect this is abnormal and probably due to the high beam current.

But to be sure, if you place or remove object in front of your camera, how long does it take for the image to get completely updated? 

[Fraser]

I noticed very little ghost effect on my camera. It behaved very much like a normal Vidicon CCTV camera. If I saturated the Tube target of any Vidicon it would suffer short term ghosting but that is to be expected.

Your units 3 second delay sounds very bad indeed and suggests that the target is not at all happy and suffering some form of saturation effect. I am no expert on Vidicon tubes however. I have worked on Vidicon cameras but not many that had weird faults or Vidicon issues beyond a burnt in image from static deployment. Maybe others on the forum will know more about what happens when a Vidicon target gets old and desensitised ? I know Vidicon tubes used to have an operational life of around 6000 hours but what effect that ‘wear’ has on the tube is not known to me. I assume sensitivity reduces over hours run and they become unacceptably insensitive at 6000 hours. The Target material may well degrade with hours run ?

Regarding the auction you referenced.... that one is likely allowed as it is a listing on eBay.com. I got the impression from the warning that I received from eBay that they thought the camera should not exist outside the USA due to export restrictions so could not be listed outside eBay.com ! Weird thinking and it does not explain how international shipping is allowed on that listing. I have often received a warning about the controlled nature of thermal cameras with regard to shipping when bidding on US auctions for such. Maybe the same would occur if I bid on those cameras ? EBay’s warning puts the responsibility on the buyer to not place the seller in a position where they break U.S Regulations applicable to such equipment ! Strange but true. It would not hold up in court though ! The seller is ultimately responsible fir export and export compliance.

Fraser

[_Wim_]

I did some more testing with a printed test pattern. If I place an opaque object in front of the test pattern, I still can see the test pattern for maybe more than 20 seconds and the opaque object never really becomes fully opaque. When removing the opaque object the decay is faster (around 3 to 5 seconds).

My best guess is the tube sensitivity is so low the gain is pushing too hard and the tube is constantly oversaturated. I cannot imagine this problem to be caused by anything else than the tube, because the test pattern remains clearly visible in the opaque object, and no electronic component can have this kind of "memory" effect, as the image is scanned line by line.

So my best chance is like you told to check all voltages and currents going to the tube, and hope that something is wrong there. Hopefully Hamamatsu will provide the datasheet for the N2606, because the required voltages and currents from the Ikegami datasheet cannot be trusted of course.

[_Wim_]

I used this test pattern btw: http://www.bealecorner.org/red/test-patterns/ISO_12233-reschart.pdf

[Fraser]

This reading material may be of interest

http://www.r-type.org/pdfs/pctdh.pdf

Fraser

[_Wim_]

This reading material may be of interest

http://www.r-type.org/pdfs/pctdh.pdf

Fraser

Thanks! Currently reading this one:
http://6bm8.lab.free.fr/Documentations/Tubes/Vidicon%20camera%20tubes.pdf
 
Seems extreme lag is caused by high dark current... Will read yours also. Seems like there is lots to know about these tubes, interesting!

[Fraser]

More reading

http://6bm8.lab.free.fr/Documentations/Tubes/Vidicon%20camera%20tubes.pdf

Fraser

[Fraser]

Ha ha it is the same as the one you are reading  Great minds think alike 

[_Wim_]

More reading

http://6bm8.lab.free.fr/Documentations/Tubes/Vidicon%20camera%20tubes.pdf

Fraser

I think that is the one I was already reading 

[_Wim_]

Ha ha it is the same as the one you are reading  Great minds think alike 

And post at the same time also...

[Fraser]

An interesting paper on Vidicon ageing.......

https://dacemirror.sci-hub.se/journal-article/be0e2b7f8628c837ae679d3f7fac1489/fafarman1968.pdf

The document seems to describe the symptom that you are seeing in your camera and it’s cause.

Fraser

[_Wim_]

An interesting paper on Vidicon ageing.......

https://dacemirror.sci-hub.se/journal-article/be0e2b7f8628c837ae679d3f7fac1489/fafarman1968.pdf

That link does not work for me. Can you post the link or the original paper so I can open it in sci-hub?

[Fraser]

Here you go

https://ieeexplore.ieee.org/document/1475417

It describes what appears to be happening in your Vidicon.

Fraser

[_Wim_]

It describes what appears to be happening in your Vidicon.

That's not good. I was still hoping is would be an electronic problems. There seems to be a problem with sci-hub, I still get "dacemirror.sci-hub.se refused to connect."

I will try again later.

[Fraser]

I will download it and send the PDF to you. Please PM me an email address.

It sounds like your tube has hit the end of its operational life and not due to Cathode poisoning

Fraser

[_Wim_]

This morning I lowered the target voltage from 27V to 8V, and the result is much better. Off course I need to open the aperture more (camera is now less sensitive), but in roomlight conditions I am still not with a fully open aperture (at 2.8, and lens goes to 1.4).

This lowers the lag to well below 1 second, which is much more workable.

VR302 was used to adjust the target voltage. So far I can say that the service manual from Ikegami matches perfectly with my camera. VR302 was turned up higher by somebody before (paint marking was broken), but now I am well below the the original position.

Hopefully Hamamatsu will provide the datasheet for the N2606, so I have more of an idea what the grid voltages should be, the dark current and a ballpark target voltage number (this seems to vary from tube to tube, and from what I have read, should be adjusted in relation with dark current).

I wonder is the "gain" adjustment on the 7290A is in fact target voltage adjustment. The 7290A has adjustable/auto gain, but the 7290 also has an internal jumper (J202) for ASC (automatic sensitivity control?) "on" or "off" , and this also affects the target voltage, and it could be that it is this jumper together with potmeter VR302 is brought externally to provide the adjustable/auto gain...

[Fraser]

If Hamamatsu do not provide the data sheet I will measure the various tube voltages on my 7290A camera for you. They are, of course, ‘as set’ by Electrophysics but should be a useable reference and better than nothing

If I get a chance I will measure them anyway as the information may still prove useful. I am a bit busy at the moment though.

Fraser

[_Wim_]

If Hamamatsu do not provide the data sheet I will measure the various tube voltages on my 7290A camera for you. They are, of course, ‘as set’ by Electrophysics but should be a useable reference and better than nothing

If I get a chance I will measure them anyway as the information may still prove useful. I am a bit busy at the moment though.

Fraser

Many thanks for that, but I have good hopes to receive the datasheet also.

I resoldered jumper J202 to the "on" position and turned up the target voltage (VR302) to the original position. Now target voltage is automatically adjusted between zero and the max set by VR302. This allows me to fully open the aperture without saturation, and even further improves lag.

Attached is the result I have filming the test image. Room lights are about 520 Lux (when lux meter is point to the ceiling), and about 200 lux (when lux meter is set next to camera lens pointing vs test image). Not the charpest, but of course this camera is not optimized for visible light I guess, and vidicon resolution is only about 600x600.

Capture device was a low cost "easier cap" USB dongle.

[_Wim_]

This is the result when a black even surface is filmed. Some small burn-ins (hard to capture, is better visible when moving an object in front of the camera), but looks quite even.

[_Wim_]

I measured the video signal with the scope, and it is a bit weak and not completely in spec. But when I try with an imaging source capture device instead of the low cost "easier cap" I get much butter results. I am currently working my way through the adjustments, but already very happy with the results so far...

[_Wim_]

The above picture is the best I could get after the adjustments. Some adjustments did not work however:
- pedastal level in video signal could not be adjusted using VR204, it is about 0.15Vpp instead of the recommended 0.1Vpp
- preamp output should be 0.3Vpp, but was only 0.08Vpp
- HF (VR203), LF (VR202) did not have any visible effect, so I left them in the same position
- gamma, width and height I left as is for the moment
- beam current is still almost at max, otherwise I do not have any output.

All in all I am quite satisfied with the result. The camera is for sure usable for the moment.

[_Wim_]

Received the datasheets for the N2606 from Hamamatsu! 

Typical target voltage is 40V, but at 27V I already have 20 seconds of lag  . But it will be good to check everything else.