Author Topic: Pyroelectric vidicon for MWIR?  (Read 241 times)

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Offline Ultrapurple

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Pyroelectric vidicon for MWIR?
« on: June 05, 2019, 11:52:03 pm »
I am a bear of very little brain, but I happened upon at least one graph that suggests the venerable pyroelectric vidicon has some sensitivity around 3µm. Does anyone know whether this has ever been exploited to make a MWIR PEV camera - and, lenses aside, what are the chances of converting my Argus 1 to MWIR?
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Offline Fraser

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Re: Pyroelectric vidicon for MWIR?
« Reply #1 on: June 06, 2019, 01:27:32 am »
Pevicons have been used in science since the later 1970’s and operated in the MWIR and LWIR bands in specialist spectrographic equipment. They can operate as low as 2um. The tube needs to be configured with the correct target material and band filtering however. Whilst the Pevicon used in the Argus 1 camera may contain a target material that will respond to MWIR, its Germanium window is likely coated for LWIR only. Bill W may know more about that specific tubes spectrum sensitivity.

Even if capable of MWIR, remember that Pevicons are not famous for their sensitivity. It was not unknown to see sensitivity figures of 1.0C with enhanced versions providing nearer to 0.2C. The P8092 is specified as having a sensitivity in the LWIR band of 0.2C. With the available energy present at room temperature in the MWIR band, that could be an issue. Bill W would be my guide on Pevicon capability though and I bow to his far greater knowledge of the technology.

Fraser
« Last Edit: June 06, 2019, 01:39:06 am by Fraser »
 

Offline Bill W

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Re: Pyroelectric vidicon for MWIR?
« Reply #2 on: June 06, 2019, 03:40:52 am »
Both,

The faceplates, although germanium, do look to have been wide band so the 3µm kick is for real at the tube itself.
The Argus 1 lens was pure 8-14µm though.
What you will not find is an Argus1 tube (P8231) with a different faceplate.  That tube size was internal use only.

What did exist are some 'standard' size tubes (P8092/3/4 and the later P8226) with special faceplates.  I know a few variants of P4428 and P4430 were made with tube faceplate and lens in ZnSe.
Scan to follow of the tube datasheet & faceplate options.
At a guess most of the more exotic tubes would have gone into Insight Vision cameras (Malvern)

Bill
 
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Offline Bill W

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Re: Pyroelectric vidicon for MWIR?
« Reply #3 on: June 06, 2019, 09:27:25 am »
Datasheet for one of the more 'techie' tubes which had explicit options for faceplates.  This was 'reticulated' - effectively pixelised -  to increase the spatial resolution, hence the 'high resolution' claim.
In Pevicon tubes the more fundamental limit on resolution was lateral thermal conduction.  Beam structure and focus were variables and generally worse in the common cameras where power and size were limited.

The datasheet for the standard P8092 is here:
http://www.fire-tics.co.uk/4221+4228.htm

Bill

Offline Max Planck

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Re: Pyroelectric vidicon for MWIR?
« Reply #4 on: June 07, 2019, 03:27:03 am »
The problem with uncooled systems in the MWIR band is the amount of energy available. Not enough at room temperature to get a decent result, unless an active configuration is used with some IR source.  IMHO, if talking passive design in the MWIR band, cooled is the answer.

Max
 
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