. Physiological optics : being an essay contributed to the American encyclopedia of ophthalmology . Fig. 23.—Curves Showing the Spherical Aberration of the Cornea. (After Brud- zewski.) The abscissae indicate the distance from the visual axis in millimeters; theordinates show the refraction in diopters. where the angle w and the distance y must be variable and experi-mentally obtainable. 46. It is known that a spherical surface has positive aberration. Aspherical cornea of 40 diopters has at 4 millimeters from the axis anaberration of about 3 diopters. But such a spherical surface may bemade a
. Physiological optics : being an essay contributed to the American encyclopedia of ophthalmology . Fig. 23.—Curves Showing the Spherical Aberration of the Cornea. (After Brud- zewski.) The abscissae indicate the distance from the visual axis in millimeters; theordinates show the refraction in diopters. where the angle w and the distance y must be variable and experi-mentally obtainable. 46. It is known that a spherical surface has positive aberration. Aspherical cornea of 40 diopters has at 4 millimeters from the axis anaberration of about 3 diopters. But such a spherical surface may bemade aplanatic, i. e., free from aberration and therefore focussingall incident parallel light at a point, if the curvature is sufficientlyand properly flattened out at the borders. An ellipsoid of revolu-tion which has an eccentricity equal to the inverse of the index of 64 PHYSIOLOGICAL OPTICS refraction is such an aplanatic surface. The question which thennaturally arises is whether or not there is sufficient flattening of thecornea in the peripheral portions as to correct its aberration. Theexp
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