from
The Collaborative International Dictionary of English v.0.48
Stereoscope \Ste"re*o*scope\, n. [Stereo- + -scope.]
An optical instrument for giving to pictures the appearance
of solid forms, as seen in nature. It combines in one,
through a bending of the rays of light, two pictures, taken
for the purpose from points of view a little way apart. It is
furnished with two eyeglasses, and by refraction or
reflection the pictures are superimposed, so as to appear as
one to the observer.
[1913 Webster]
Note: In the reflecting stereoscope, the rays from the two
pictures are turned into the proper direction for
stereoscopic vision by two plane mirrors set at an
angle with each other, and between the pictures. In the
lenticular stereoscope, the form in general use, the
eyeglasses are semilenses, or marginal portions of the
same convex lenses, set with their edges toward each
other, so that they deflect the rays coming from the
picture so as to strike the eyes as if coming direct
from an intermediate point, where the two pictures are
seen apparently as one.
[1913 Webster] Stereoscopic