Another recent technique is the "magic eye" autostereograms. Current 3D movies are usually viewed with polarized glasses instead of red-green so the movies can be in color. 3D movies were viewed with red-green anaglyph glasses in the 1950s. Brewster stereoscopes (different design, but same in concept) were popular around 1900 with photographed stereo pairs. Stereograms have been part of popular culture in each generation since Wheatstone. Viewed through red-green glasses, one eye sees the red image and the other eye sees the green image. One way is to superimpose two half images, one in red and one in green. The basic concept is to present slightly different images to the two eyes. There are lots of ways to make and view stereograms. The shifts mimic differences which ordinarily would exist between the views of genuine 3D objects. The two images in a stereogram are slightly different, with features in one image shifted to slightly different positions in the other image. Stereogram: A pair of images (such as E/E' above) that are viewed using a stereoscope (or a red-green anaglyph). If you put your face in front of a pair of angled mirrors, and put two slightly different pictures off to the sides, your left eye will see the left picture (E') and your right eye will view the right-hand picture (E). Stereoscope: One way to view stereo image pairs is to use a mirror stereoscope. It is further to the left from the right eye's perspective. You'd have to cross (converge) your eyes to fixate on it. It lies further to the right from the right eye's viewpoint than from the left eye's viewpoint.Ĭrossed disparity: An object closer than the horoptor has crossed disparities. You'd have to uncross (diverge) your eyes to fixate on it. Uncrossed disparity: An object farther away from you than the horoptor has uncrossed disparities. The geometric horopter (the set of points with zero disparity) is a circle that includes the fixation point and the optical centers (lenses) of the two eyes. Horopter: imaginary 3D surface in the room in front of you that includes the object you are fixating on and all other points in 3D space that project to corresponding positions in the two retinae. However, the disparity also depends on the distance to the fixation as well, so that disparities must be further interpreted using estimates of the fixation distance. Wheatstone correctly pointed out the advantage of having two eyes to see objects in 3D depth. Before that, people were confused, thought that having two eyes posed a problem because couldn't figure out how you could see only one image when viewing the world with two eyes. Wheatstone (1838) was first to figure this out. The amount of disparity depends on the depth (i.e., the difference in distance to the two object and the distance to the point of fixation), and hence it is a cue that the visual system uses to infer depth. As you can see, the distance between the two fingers is different in your left than in your right eye their relative positions in the two retinae are disparate.īinocular disparity is defined as the difference in the location of a feature between the right eye's and left eye's image. Fixate the more distance hand, and alternately view the scene with your left eye and then your right. Stereo Vision Stereopsis: greek for "solid sight".Ĭlose one eye, and hold up your two index fingers, one fairly close to your face and one as far as you can reach.
Movement cues (parallax, kinetic depth effect).Monocular, physiological cues (blur, accommodation, etc.).Pictorial depth cues (texture, shading, perspective, etc.).binocular rivalry and the neural correlates of visual awareness.disparity selectivity of binocular neurons in V1.fusion, suppression, diplopia, binocular rivaly.random-dot stereogram and the correspondence problem.Binocular disparity, crossed and uncrossed displarity, dependence on depth and distance, horopter.Perception Lecture Notes: Depth, Size, and Shape Perception Lecture Notes: Depth, Size, and Shape Professor David Heeger What you should know about this lecture
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