Stereobase
The stereobase is the distance between the optical viewpoints of the left and right cameras in a stereoscopic imaging system. It is also commonly called the interaxial distance.
Changing the stereobase changes the difference between the two recorded views and therefore affects the strength of perceived depth. A wider stereobase usually produces stronger depth, while a smaller stereobase usually produces gentler depth. The appropriate value depends on the subject distance, focal length, image format, intended display, and acceptable parallax.
For a physical camera rig, the stereobase should be measured between the two optical centres or entrance-pupil positions—not simply between the outer edges of the camera bodies.
Stereobase = the distance between the left-eye and right-eye camera viewpoints.