Caption: "Combination of porro prisms used in binoculars."
A porro prism is a type of prism used in optical devices to change the orientation of an image by total internal reflections.
Total internal reflection occurs when angle of incidence of light ray at an interface between optical media is too large to allow refraction: i.e., no refracted light ray is transmitted.
In this image, there are 4 total internal reflections.
This is clearly seen.
Credit/Permission: ©
Bob Mellish (AKA DrBob),
before or circa 2007
(uploaded to Wikipedia
by User:Pasixxxx,
2007) /
Creative Commons
CC BY-SA 3.0.
Image link: Wikipedia.
Local file: local link: optics_prism_porro_double.html.
File: Optics file:
optics_prism_porro_double.html.