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Stereoscopic acuity, also stereoacuity, is the smallest detectable depth difference that can be seen in binocular vision. ==Specification and measurement== Stereoacuity 〔Howard IP, Rogers BJ (2002) ''Seeing in Depth''. Vol. 1I. Chapter 19 Porteous, Toronto〕 is most simply explained by considering one of its earliest test, a two-peg device, named Howard-Dolman test after its inventors:〔Howard HJ (1919) A test for the judgment of distance. ''Amer. J. Ophthalmol.'', 2, 656-675〕 The observer is shown a black peg at a distance of 6m (=20 feet). A second peg, below it, can be moved back and forth until it is just detectably nearer than the fixed one. Stereoacuity is this difference in the two positions, converted into an angle of binocular disparity, i.e., the difference in their binocular parallax. Conversion to the angle of disparity ''dγ'' is performed by inserting the position difference ''dz'' in the formula : where ''a'' is the interocular separation of the observer and ''z'' the distance of the fixed peg from the eye. To transfer ''dγ'' into the usual unit of minutes of arc, a multiplicative constant ''c'' is inserted whose value is 3437.75 (1 radian in arcminutes). In the calculation a, dz and z must be in the same units, say, feet, inches, cm or meters. For the average interocular distance of 6.5 cm, a target distance of 6m and a typical stereoacuity of 0.5 minute of arc, the just detectable depth interval is 8 cm. As targets come closer, this interval gets smaller by the inverse square of the distance, so that an equivalent detectable depth interval at ¼ meter is 0.01 cm or the depth of impression of the head on a coin. These vary small values of normal stereoacuity, expressed in differences of either object distances, or angle of disparity, makes it a hyperacuity. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「stereoscopic acuity」の詳細全文を読む スポンサード リンク
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