1.b. Outline of the physiology of vision paragraph summarizes the thesis in information engineering "Geometry of vision, problems of recovery and display of stereoscopic sequences," conducted by Giuseppe Colace at the RAI Research Centre. Rapporteur Eng. Gianfranco Barbieri, co-rapporteur ing. Mario Muratori.
Our eyes are composed of a bulb and some outbuildings such as the extrinsic muscles, which are used to to rotate the bulb inside his home, the glands, the lacrimal and lids, which serve to lubricate the sclera.
The bulb, roughly spherical in shape, and consists of three walls called tunics that, proceeding from the outside, are the sclera, the choroid and retina, the latter home to the receptors of light.
The image focused on the retina and impressed by the system of "slow" composed of the dioptric media-from 'outside to inside: the cornea, aqueous humor, lens and vitreous body (of which only the lens has the ability to deform, at the instigation of the intrinsic muscles, to get the exact focus of the image on the retina). The iris diaphragm and which has in its central element of the body with the pupil size varies. In this way the iris adjusts as a result of a reflection photomotor said, the intensity of light reaching the retina within optimal limits (a little 'nell'occlusore as a camera. The photoreceptors of the retina, which differ in rods and cones, collect and transform the light stimulus in nervous excitement through biochemical reactions. This stimulus is then conveyed via the optic nerve, the cortical centers, dedicated to vision, present in the brain.
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Despite the man has two eyes, not seeing double, thanks to the fusion process (sensory). This process allows the recognition of the observed objects and is therefore crucial for learning and, consequently, for the knowledge. The visible image of each point constituting an observed object, called object point is projected on the retina in a couple of points, one for each eye, called retinal points. When fixing on an object, the optical axes converge eye, intersect at a particular point called fixation. His image projected on the retina, particularly the fovea, is form on a pair of retinal points, one for each eye, from which nerve impulses that originate in the vision system "fuses" in a single step. For this reason these are called corresponding retinal points, are not symmetrical from an anatomical point of view, but are functionally coupled because of the phenomenon of sensor fusion. For each fixation point there is a curve called oroptero (from the greek oros, limit and opt, observer), composed of all the points of real space for which the merger occurs. This is achieved because their images projected on the retina are formed on pairs of corresponding retinal points, one for each retina. In other words, all points of real space lying sull'oroptero are perceived as individual points.
Since the observed objects and to recognize they must be perceived as unique, the cerebral cortex continuously governs the direction of observation by eye movements, so that the images fall on corresponding retinal points.
The fusion takes place not only for points lying sull'oroptero, but also for those who are in a restricted area, called Panum's area, which extends in front and behind it, and that has a shape similar to that shown in the figure.
centers responsible for vision, analyzing the retinal disparity between his image on the retina, and about the fixation point.
object points that lie outside of the Panum are seen as double, a phenomenon called diplopia. The images of these points covered points are formed on the retina, which was not paired are called disparate and do not lead to the merger. To realize this phenomenon, we can perform a simple experiment in the figure: we put before our eyes at a distance of about 20 cm. the left forefinger. If at this point we fix it we will see single, if standing between our faces and the index finger of the right hand we will see it as double vision (diplopia Crusade) and the same feeling if we place it between the index left hand and infinity (homonymous diplopia). Changing fixation point diplopia occurs for other objects, thus focusing the index of the right hand (without moving), we will double the finger of his left hand. If an object is perceived as a double between the eyes and place el'oroptero crusade and if we talk about disparities and place among the infinite oroptero speak of inequality of the same name. Usually we do not appreciate the so-called physiological diplopia because our attention is focused on the object you are observing, and then our brain ignores the double images.
Experiment reproduce the effect of "diplopia"
