Extension for a Golf Range Finder

[polocouch]

TL;DR Summary

Hi guys, I have a golf range finder, I want to add a tube to the eye Port of said range finder and be able to view what I can view while my eye is directly against said port. Can anyone help me out here ? How is this possible?

 

[berkeman]

Welcome to PF.

So you want to be able to see the same display when your eye is a few cm away from the device? Can you say why? Have you tried holding your cellphone camera lens in the exit pupil of that device yet? You may be able to just make a simple holder for your phone to be able to see it on your phone display

https://en.wikipedia.org/wiki/Exit_pupil...

 

[DaveE]

In the world of geometrical optics, this is called "eye relief". If you exceed that distance you will have to build a telescope, not just a tube.

 

[polocouch]

Welcome to PF.

So you want to be able to see the same display when your eye is a few cm away from the device? Can you say why? Have you tried holding your cellphone camera lens in the exit pupil of that device yet? You may be able to just make a simple holder for your phone to be able to see it on your phone display

https://en.wikipedia.org/wiki/Exit_pupil...

I want to make the range finder seem much larger than it is, like a gag but I need the ability to see it through a longer tube. Not a truly functional reason

 

[polocouch]

In the world of geometrical optics, this is called "eye relief". If you exceed that distance you will have to build a telescope, not just a tube.

Thank you, I understand it can’t just be a tube I know there has to be a way to do it thanks that’s why I’m asking

 

[Tom.G]

Two lenses inside that tube:
One to grab the rangefinder image and send parallel rays down the tube.
One to refocus those parallel rays to form a viewable image.

If the first lens has a long focal length and the second lense a short focal length, you have a telescope (or microscope, depending on their spacing).

Equal focal lengths give you an image relay system, keeping the image the same size.

(OK, been decades since I've done this stuff so corrections are encouraged!)

Cheers,
Tom

 

[DaveE]

One to grab the rangefinder image and send parallel rays down the tube.
One to refocus those parallel rays to form a viewable image.

Nope. Parallel into means parallel out of a telescope, but not in the middle*. It's kind of the definition of these things.

Figure 3.15 (a) A Galilean telescope. (b) A Keplerian telescope.

https://www.routledgehandbooks.com/doi/10.1201/9781315373034-4

*although I suppose you could call a tube with no lenses a telescope with magnification of 1 and parallel rays everywhere.