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Optics of door security viewer

Optics of door security viewer - Physics Forum

Optics of door security viewer - Physics Forum. Discuss and ask physics questions, kinematics and other physics problems.


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  #1  
Old 07-08-2006, 09:54 AM
Jane
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Default Optics of door security viewer



What is the optical arrangement of lenses in a door security viewer and
what sort of powers might they be?

These teo are the sort of thing I mean:
[Only registered users see links. ]
[Only registered users see links. ]

I want to make my own viewer to watch birds immediately outside my
window! The viewer would go through my curtains.

Binoculars do not focus down enough to the 0.5 to 1.0 meters I need.

I have no idea of optics but I reckon I could probably build some sort
of lens arrangement if only I knew what arrangement I was aiming for.
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  #2  
Old 07-08-2006, 03:57 PM
2
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Default Optics of door security viewer

"Jane" <[Only registered users see links. ]> wrote in message
news:Xns97FA6EF2754421A7D4@127.0.0.1...


For gosh sake, just buy one. They are cheap enough.


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  #3  
Old 07-08-2006, 06:55 PM
tadchem
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Default Optics of door security viewer


Jane wrote:

It is a simple Galilean telescope. It uses lenses instead of mirrors.

The lenses have been selected to give a wide-angled view instead of a
magnified image.

They work like a wide-angled lens on a camera.

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  #4  
Old 07-09-2006, 05:39 PM
John C. Polasek
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Default Optics of door security viewer

On 8 Jul 2006 11:55:39 -0700, "tadchem" <[Only registered users see links. ]> wrote:


Look backwards through an opera glass and you'll get the same effect
with inverse (de)magnification.
The door has a positive longer FL lens inside, and a negative, shorter
FL lens outside. The angle is multiplied by the ratio of focal
lengths.
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  #5  
Old 07-09-2006, 10:28 PM
Jane
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Default Optics of door security viewer

On 08 Jul 2006, 2<[Only registered users see links. ]> wrote:


The overall length of one which fits a door will be far too small. I
want to build one because I have to.
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  #6  
Old 07-09-2006, 10:29 PM
Jane
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Default Optics of door security viewer

>>Jane wrote:




On 09 Jul 2006, John C. Polasek<[Only registered users see links. ].com> wrote:

That's it. Thank you!
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  #7  
Old 07-09-2006, 10:58 PM
2
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Default Optics of door security viewer

"John C. Polasek" <[Only registered users see links. ].com> wrote


Not really. The door lens is a "fisheye" type. It has a very wide view while
the reversed opera glass does not have a particularly wide view.


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  #8  
Old 07-09-2006, 10:58 PM
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Default Optics of door security viewer

"Jane" <[Only registered users see links. ]> wrote in message
news:Xns97FBEEFBE3A581A7D4@127.0.0.1...


Won't work the same at all.


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  #9  
Old 07-10-2006, 12:15 AM
John C. Polasek
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Default Optics of door security viewer

On Sun, 09 Jul 2006 23:28:07 +0100, Jane <[Only registered users see links. ]> wrote:

It works like I said, but it is important to have a low f-number on
the negative lens(big lens, short FL) so it doesn't vignette your
view.
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  #10  
Old 07-10-2006, 03:35 AM
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Default Optics of door security viewer

"John C. Polasek" <[Only registered users see links. ].com> wrote


Why don't you give a specific recommendation? Are you suggesting the OP
purchase a fisheye lens for a camera? That's nutz! She does not need the
acutance and corrections of a spendy camera lens. The rest, for example
utility glass, don't specify what F of the lens.



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