The word derives from two Greek roots: haploieides, single and skopeo, to view.
A stereoscope is a type of haploscope, but not vice versa.
The word has more currency in the medical field than elsewhere, where it refers to instruments designed to test binocular vision.
Reputedly the largest haploscope, with images of over a meter (in fact, 4 feet) square and a viewing distance for each eye of nearly five meters (16 feet), was constructed by Vaegan in about 1975 to research stereoacuity.
[2] The large images allowed very small retinal disparities to be presented.