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Rifles, Reloading, Optics, Equipment
Long Range Scopes and Other Optics
eye relief margin
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<blockquote data-quote="LouBoyd" data-source="post: 342093" data-attributes="member: 9253"><p><strong>Re: eye relief margin (more for night vision scopes)</strong></p><p></p><p>My previous explanation of eye relief behavior does not apply to night vision scopes which use image intensifiers or CRT or LCD screens. On those there is no tunnel effect with eye relief other than seeing the full area of the display with the eye close and at long eye relief only seeing a portion of the display though the eyepiece unless the eyepiece is huge. This is because the light exiting the eyepiece has no angular relationship to the hight which entered the objective. Night vision scopes have no distinct exit pupil. The light exiting the eyepiece does not converge to a spot as with a conventional scope and instead just expands. Night vision scopes always waste a lot of light from their output screen. That's why night vision scopes need a flexible eye shield to keep from being visible by someone else with a night vision scope or even a conventional scope. </p><p></p><p>The lack of angular information also the reason that any night vision scope with a front projection reticle (or a software generated reticle in a video scope) may have fuzzy focus if the objective is out of focus but it cannot have any parallax error resulting from eye position offset as an optical scope does. Night vision scopes with a separate reticle after the intensifier (or video screen) can have parallax error, but if it does it can't be removed by adjusting the objective lens focus or the eyepiece focus. Some NV scopes have a third (internal) reticle focus. (AN/PVS-12 for example). Some import NV scopes have a reticle affixed to the glass of the phosphor screen which introduces parallax error which cannot be removed.</p></blockquote><p></p>
[QUOTE="LouBoyd, post: 342093, member: 9253"] [b]Re: eye relief margin (more for night vision scopes)[/b] My previous explanation of eye relief behavior does not apply to night vision scopes which use image intensifiers or CRT or LCD screens. On those there is no tunnel effect with eye relief other than seeing the full area of the display with the eye close and at long eye relief only seeing a portion of the display though the eyepiece unless the eyepiece is huge. This is because the light exiting the eyepiece has no angular relationship to the hight which entered the objective. Night vision scopes have no distinct exit pupil. The light exiting the eyepiece does not converge to a spot as with a conventional scope and instead just expands. Night vision scopes always waste a lot of light from their output screen. That's why night vision scopes need a flexible eye shield to keep from being visible by someone else with a night vision scope or even a conventional scope. The lack of angular information also the reason that any night vision scope with a front projection reticle (or a software generated reticle in a video scope) may have fuzzy focus if the objective is out of focus but it cannot have any parallax error resulting from eye position offset as an optical scope does. Night vision scopes with a separate reticle after the intensifier (or video screen) can have parallax error, but if it does it can't be removed by adjusting the objective lens focus or the eyepiece focus. Some NV scopes have a third (internal) reticle focus. (AN/PVS-12 for example). Some import NV scopes have a reticle affixed to the glass of the phosphor screen which introduces parallax error which cannot be removed. [/QUOTE]
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