NVG - How do they work?
Sorry Sikhorsey, as shown in the diagram, gogs work by amplifying the light that comes in the front. If there's no light going in, there's nothing coming out. I've been there.
(a bear of little brain)
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L Peacock.
The 20/20 is the ability to read a certain size font at 20 feet (can't remember the size though) with each eye. Also these days referred to as 6/6 (same test, 6 metres).
20/20 is a good average but if you could read it further away you could, for instance, have 24/26 vision, or something like that. (As opposed to me with about 02/04 - out of 20).
The 20/20 is the ability to read a certain size font at 20 feet (can't remember the size though) with each eye. Also these days referred to as 6/6 (same test, 6 metres).
20/20 is a good average but if you could read it further away you could, for instance, have 24/26 vision, or something like that. (As opposed to me with about 02/04 - out of 20).
Join Date: Feb 2005
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You've educated me. But does that really mean 20/20 merely defines average vision, not perfect?
It is quite possible to obtain better vision. My near vision, for example is 20/15 & used to be 20/10 when a youngster - as did my distance vision (which is now marginally 20/20 on a good day
) 20/15 means that I can see at 20 feet what the average person has to move up to 15 feet to see.
I recall when my vision started to slowly degrade as I got older - when I got to 20/20 I thought "F*** me! This is what everyone else sees?!"
My understanding (from CAM orientation cse) is that the best one could expect (on average) was 6/18, which whilst not quite 'legally' blind
Realize that Hoffman & real-world are close, but not quite the same. Everything you put between your eyes & the goggles (like glasses or contacts) & the goggles & the object you're viewing (like windscreens, airborne dust, obscurants, etc.) & it degrades significantly.
Also, it is essential to be viewing through the exact centre of the goggles to obtain the best resolution. And the gogles need to be tilted to 0 in reference to your eyes. As your helmet sags a bit, your vision degrades as you look through a (potentially) less capable portion of the tube with a (potentially) less capable portion of your eye.
The key is the micro-channel plate. When I got my training as an NVG instructor several years ago, the early Gen III tubes were state-of-the-art. At that time, there were something like 3,000 tubes in the micro-channel plate, all lined internally with lead, & tilted at 8-degrees. All in something only slightly larger than a 10p piece. As the electrons are released by the photo-cathode, they will strike the edges of the tubes (why they're tilted) & as the electron bounces into the side of the tube, it releases two electrons, both of these will deflect off the tube at an angle equal to their impact angle & will likely strike the tube & each release two more electrons & so on & so on - so that the electrons end up multiplied something on the order of 3000-4000 times before they hit the phosphor screen.
So, yes, there must be SOME light entering. Sikhorsey, I have no doubt that you have flown on "zero illumination" nights, with no moon & <0.2 mlux w/cloud cover, but there's always SOME light about...if your goggles aren't scintillating, you've got adequate light. And the lower you fly on a dark night, the easier it is to see! So 50' is easier than 300' I'm at & I'm going twice as fast as you when I fly on those dark as ink nights!
