P.S.
@jeffl838
I apologize for the severe derailment of your thread.
Re: your original question, the way the PBM and NPBM were designed, they were not intended to be collimated.
Collimation involves rotating the eyepiece lens assemblies to align the optical shift of the image intensifer tubes and lenses to be in as close alignment as possible.
When light enters the objective lens, image intensifier tube, and eyepiece lens, it does not travel in a perfectly straight path, it experiences some shift as it goes through, so it does not translate perfectly parallel from the input to the output end.
This is why clip-on night vision devices are so expensive, and it is also an important part of building binocular systems, and there are test sets and direct support mainentance procedures for checking and setting collimation.
The PBM and NPBM were originally designed to allow units and organizations to have a “binocular-like” capability using fleeted PVS-14s that could not simply be sold or traded for dedicated binoculars.
The overall goal was to create a system that provided some of the benefits of a binocular system at a minimal cost and impact to the user—which also meant user-level installation.
Since removing/rotating eyepiece assemblies to set collimation is not a user-level task, in that sense, the PBM/NPBM are advertised as not being able to be truly collimated.
That being said, if you had access to a test set you could hypothetically try to collimate them, however, PVS-14 MX-11769 style image intensifiers allow for about three times the amount of optical shift that MX-10160 “aviation grade” image intensifiers commonly used in most binocular systems allow for, meaning that they may, depending on how far on the tolerance spectrum they are, be more difficult or impossible to properly collimate within the stated specs (1/2 rotation of the eyepiece assembly), and even if you can get them within tolerance, they may not be as close as they could be with MX-10160 format tubes.
There are some ways to “DIY” collimate that are not necessarily the same as using the correct tools/fixtures, however may get you closer than “factory,” however again, they require disassembly of the PVS-14, and to be done “to spec,” will require a re-purge. Instructions for how to do so “DIY” have been posted recently on ARFCOM as well, two good threads to check out have been written by tlandoe07 and cj7hawk.
The reality is that while collimation is certainly important and poor alignment can cause issues for some users, your brain is a wonderful tool, and can be remarkably forgiving.
Within reason, you brain can often adjust imperfect images enough to allow you to function normally without your having to go through much if any conscious effort.
It’s not “as good” as proper alignment, but it’s useable. I have used uncollimated goggles before—for me knowing what I should see, it’s immediately noticeable, however within 5-10 minutes, my eyes/brain have adjusted to it, and I no longer notice the misalignment, though I may feel a little crosseyed when I remove the goggles.
Now, some people are more or less sensitive to these kinds of optical alignment issues, I am not that sensitive.
For
some people the results on the extreme end can be an immediate headache. For most people, however, it simply limits the amount of time the goggles can safely be used before fatigue and processor (brain) burnout occurs, and they either have to stop using them, or if you’re talking about operating a vehicle or handling firearms, it simply becomes unsafe for them to continue doing so.
This is not something that’s likely to be noticed by most in individual use and in isolation in limited use.
Where it becomes more apparent is in the comparison of groups of people using different equipment, guys using poorly adjusted or misaligned systems get tired faster, have to take more breaks, have more “brain farts” as time goes on and their processors start getting overwhelmed and overworked. Certainly the overall system weight doesn’t help either, but again—considering that these requirements come from the aviation community and aviation systems, the need is fairly obvious, you don’t want guys starting to miss things and make poor decisions while operating an aircraft—and you can’t wait until the operator starts getting tired to pull the plug, because you still need to land the thing. In many cases a ground user could simply step back, take a break, flip their goggles up, and carry on.
That being said, it is, as I’ve noted in the various derails, a real thing, and part of building binocular goggles to spec, and even in ground use, an advantage to using a dedicated, built to spec binocular versus an uncollimated, bridged PVS-14.
The irony of the situation is that WhereNow&How isn’t wholly wrong in and that it’s not always a big deal for recreational ground-users, and articulating goggles, dedicated or not, are harder to collimate properly due to the rotational IPD adjustment that changes the relative position of the image intensifier (and hence the optical shift), which is why you don’t really see articulating goggles for aviation applications.
A lot of mil-specs are not necessarily relevant to most recreational and hobbyist users, do you really care that your PVS-14 can be submerged to 66 feet instead of only 5 or 10 feet?
What I do rather dislike, however, and sorry, I’m jumping off track a little bit here again, is the implication that I am simply “making shit up” to sell product, when I try to provide actual (and factual) technical information about products and why they may or may not be important to some applications, and why some things are considered better than others.
~Augee
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