The stereoscope is an optical instrument that allows an observer to see with the right eye a drawing or photograph of a three-dimensional object, a landscape or scene as he or she would see it with the right eye if he looked at it from a certain position and to see at the same time with the left eye a drawing or photograph of the same subject as he or she would see with the left eye on looking at it from the same position.
Stereoscopic photographs are usually taken with a camera having two objectives placed at the mean distance between pupils of approximately 6.5 cm; one plays the role of the right eye and the other that of the left eye, but such images can also be obtained by taking two photographs from the corresponding positions with a normal camera.
Through the stereoscope the right eye sees the image that it would see if it were in the position of the right objective and the left eye the image the left eye would see from the position of the left objective; ...continues