Here, following my little NV adventure I wanted to present to you one new implementation based on:
- cascade tube P8079HP
I am not yet in possession of the ideal gen III tube having a 25 mm protruding FOP screen which could be ideally coupled to the FOP of the photocathode of the P8079HP, but I recently acquired a MX 10160 (LITTON) (18 mm photocathode/embedded screen).
Therefore, while waiting this "holy grail" tube, I tried to build a Gen III + I hybrid tube with what I had available now: benefiting of a S/N better (I guess) from the Gen III than the Gen I, and benefiting for the tremendous gain offered Gen I cascade: chasing the butter and the money for the butter...
Such decision with my current available material involves some limitations:
- The only way for me to couple the screen of the Gen III (MX 10160) to the Gen I cascade (P80798HP) was to use a lens coupling (relay or "macro" lens).
- because of the size mis-match between the screen of the Gen III (18 mm diam) and the photocathode of the Gen I (25 mm), I had to accept to unfortunately magnify the image coming from the Gen III, which lead to decrease the coupling efficiency of the relay system:
I played by estimating the coupling efficiency of my relay system (f=20 mm, f/d= 0.9, T= 0.7, M= 1.4) and I obtained something around 0.07... more or less 7% of photons transmitted from the screen of the Gen III to the photocathode of the Gen I cascade.
But the photocathode of the P8079HP is at least fully covered and I benefit of the full FOV available with this tube.
See the following reference: "The research of Relay Lens Coupling in Image Intensified Camera" Sun X et all, Proc. of SPIE vol. 8912 89121E-1, 2013, (p. 5).
At least, I hope that magnification of the image coming from the Gen III (64 lp/mm) by X1.4, should help the following Gen I tube (40 lp/mm) to have access to some additional details.
Nevertheless I tried the adventure and obtained the configuration corresponding to the first drawing, and following photos below (some details on the relay optics/coupling lens and the final hybrid scope obtained.
In term of results:
- It works, greatly, I would say too much.... indeed, I intend to use my different NV projects in a "multi-purpose" idea, for astronomical viewing but also terrestrial one. But with this new configuration, despite the low coupling efficiency of the relay lens, it is now simply un-suitable for terrestrial viewing in night urban condition or country side condition with some light background coming from a diffusive clear sky because of remote light pollution, for instance...
even for astronomical viewing, if the sky is light polluted, it would be unusable without serious narrow band filtering, I guess.
when I tried, the ABC/anti blooming of the P8079HP ran immediately, my eye was flashed and washed up for one or two minutes. The target was, during night without moon, a dark corner of a football field away from any direct light, lampadair, and only exposed too the light pollution of the sky.
So, I kept on testing my system at home in some dark/pitch black room. I mean, impossible to sse my finger in front my nose after dark adaptation.
there, I was able to see without any ambiguity and difficulty details of the room, tiles frame, furniture structures and so on.... grainy image but fully usable.
I will try to do some fluorescence detection in my pitch black room, with some ceramic previously exposed to lights, or using some worn and attenuated watch needles or frame...
From now, I will also wait the next occasion to go under a really dark sky in country side, for testing sorrowly this system and its true capability.
If this test "on field" will confirm this potential, I will definitively invest in a set of narrow band filters, for sure!
But definitively it is very encouraging, despite the fact it became now something quite "specialized"...
The next setp, after filtering, would be to at least replace the current relay lens by a proper divergent taper optical fiber plate, or ideally to find the good Gen III tube as described above (my "holy grail").
I have also to do a proper solid longitudinal frame for the whole device, equipped wit a set of amovible flanges.
Thank you as usual for your patience for reading me. hoping it would bring some pieces of informations usefull for the community.
Clear skies for all!