Optics question - inverted image (1 Viewer)

I have read that a prism is required to correct the inverted image on binoculars and terrestrial spotting scopes etc. A friend alerted me that rifle scopes do not have a prism and do not have an inverted image. Can someone explain if this is correct, and if it is correct why the prism is needed on binoculars but not a rifle scope?

Thanks in advance

Tvc15_2000 said:

I have read that a prism is required to correct the inverted image on binoculars and terrestrial spotting scopes etc. A friend alerted me that rifle scopes do not have a prism and do not have an inverted image. Can someone explain if this is correct, and if it is correct why the prism is needed on binoculars but not a rifle scope?

Thanks in advance

Click to expand...

Most rifle scopes use an erector lens system, which is usually two lens, to turn the upside down image right side up. I'm not an optics expert but I believe erector lens are used in rifle scopes because prisms are not practical in the relatively narrow scope bodies that rifle scopes have, usually one inch or 30mm. Prisms are used in binoculars and spotting scopes because they revert the image back with more efficiency, concerning light transmission, than two additional lens would.

I was unfamiliar with the term "erector” and “erector system". That was a great tip and I was able to do some searches and find lots more about it.

Thank You!
TVC