Abstract: A haploscope has a housing defining left and right viewing apertures disposed to permit substantial alignment with a subject's left and right eyes and permit viewing through the housing. Projection light sources for projection of left and right images are provided and the housing defines first and second light source apertures for transmission of light from the sources therethrough. The haploscope has first and second projection devices for projecting images using the light passing through respective ones of the first and second light source apertures. The housing has a rotary disc and a motor for rotating the rotary disk within the housing at a position permitting occlusion of the first and second light source apertures and the left and right viewing apertures. The rotary disc has at least one viewing aperture disposed to align with the left and right viewing apertures during rotation of the rotary disc such that only one of the left and right viewing apertures is not occluded at a given time.