DOI:10.1068/p3103ed

Charles Wheatstone was born two centuries ago, but one instrument he invented continues to influence the scientific lives of many researchers in vision. The stereoscope (figure 1) was invented in the early 1830s, and it opened a new world for the study of binocular vision. That world was the laboratory, and with the aid of the stereoscope the methods of physics could be applied to the investigation of spatial vision. Wheatstone was able to manipulate the pictures presented to each eye and observe the depth that was produced. In so doing, he found that: ``the projection of two obviously dissimilar pictures on the two retin × when a single object is viewed, while the optic axes converge, must therefore be regarded as a new fact in the theory of vision. It being thus established that the mind perceives an object of three dimensions by means of the two dissimilar pictures projected by it on the two retin×, the following question occurs: What would be the visual effect of simultaneously presenting to each eye, instead of the object itself, its projection on a plane surface as it appears to that eye?.... The stereoscope is represented by figs. 8. and 9.; the former being a front view, and the latter a plan of the instrument' ' (Wheatstone 1838, pages 372 ^ 373 and 375)