Telecentric entrance pupil - Optics

[Wminus]

Hi. As you guys know, an object-telecentric system (a system with constant magnification) has per definition an entrance pupil that is infinitely far away. One can construct such a system by taking a lens and placing an aperture stop (AS) at its focal point.

My issue is that I am struggling to ray-trace the aperture stop (AS) through the telecentric system. I just can't get the "infinitely far away entrance pupil" condition without also assuming that the aperture stop has a diameter approaching zero.

I am assuming paraxial approximation and geometrical optics. Is perhaps this the reason behind my difficulties?

 

[Andy Resnick]

Not sure- there's nothing particularly bizarre about telecentric lenses. Here's some additional info that may help you:

http://www.lhup.edu/~dsimanek/3d/telecent.htm

https://www.schneideroptics.com/ecommerce/CatalogSubCategoryDisplay.aspx?CID=1439

 

[Wminus]

Not sure- there's nothing particularly bizarre about telecentric lenses. Here's some additional info that may help you:

http://www.lhup.edu/~dsimanek/3d/telecent.htm

https://www.schneideroptics.com/ecommerce/CatalogSubCategoryDisplay.aspx?CID=1439

I think I forgot about the paraxial approximation. With thin lenses and paraxial approximation, any object at a focal point will produce an image infinitely far away from the lens. In this case the object is the aperture, and hence its image will be infinitely far away.

Anyway, if you are skilled with optics, could you please help me here? https://www.physicsforums.com/threads/optics-Newtonian-telescope.804709/ I simply can't seem to find the entrance and exit pupils!

 

[Andy Resnick]

I think I forgot about the paraxial approximation. With thin lenses and paraxial approximation, any object at a focal point will produce an image infinitely far away from the lens. In this case the object is the aperture, and hence its image will be infinitely far away.

Anyway, if you are skilled with optics, could you please help me here? https://www.physicsforums.com/threads/optics-Newtonian-telescope.804709/ I simply can't seem to find the entrance and exit pupils!

I don't know about 'skilled', but I responded to the above thread...