Stereoscope

While we see solid objects we see it as a three dimensional one. For several reasons, firstly, the different lighting of the different parts of objects enables us to perceive their shape. Secondly the strain we feel when accommodating our eye to get a clear perception of the object’s different parts that are at different distances from the eye also plays a role; this is not a flat picture in which all the parts of the object depicted are set at the same distance away. And thirdly, the most important cause is that the two retinal images are different, which is easy enough to demonstrate by looking at some close object, shutting alternately the right and left eye. Imagine now two drawings of one and the same object, one as seen by the left eye, and the other, as seen by the right eye. If we look at them so that each eye sees only its own drawing, we get instead of two separate flat pictures one in relief. The impression of relief is greater even than the impression produced when we look at a solid object with one eye only. As you see the stereoscope’s basic principle is extremely simple: all the more amazing, therefore, is the effect produced. I suppose most of you have seen various stereoscopic pictures. Some may have used the stereoscope to learn stereometry more easily. However, I shall proceed to tell you about applications of the stereoscope which I presume many of you do not know.