Abstract
LONDON. Optical Society, April 10.—J. W. French: The unaided eye. After a brief historical introduction, the principal dioptric features of the eye were considered, particularly those relating to the pupil reflexes. By means of a simple pupilometer the diameter of the pupil when applied to optical instruments was measured. The variations of the pupil with varying illumination of the whole retina, of the macula lutea, and of several zones of constant area were also measured and the results discussed. It would appear that for the macula lutea the pupil area varies as the fifth root of, the illumination. The zone around the macula lutea is more sensitive, and the sensitiveness diminishes thereafter towards the margin of the retina. So far as the pupil reflexes are concerned, the two eyes are quite independent of each other; while the pupil area of the one eye under constant illumination remains constant, the other eye under simultaneous variation of the illumination varies in accordance with the above law. The variation of the pupil area with accommodation is quite: independent of the illumination, and is determined bv the refractive power of the crystalline lens.—T. Smith: The spacing of glass-working tools. In constructing optical systems the exact curvatures for the surfaces determined by calculation need not be employed, but the departures must lie between limits which will be functions of the nominal curvatures. It follows that a system of properly spaced tools should suffice to meet all normal requirements. The basis on which a system should be constructed is discussed, and a proposed standard list of tools is derived from an aberrational condition, together with assumed extreme relations between aperture and focal length and between anerture and radius of curvature. The total number of tools, which is finite, occurs as an independent variable in the formula on which the system is constructed, and in the absence of experimental investigations this must be. determined by comparing the results obtained from an arbitrarily assumed value with the lists that manufacturers have found from experience to be reasonablv spaced. A comparison between the list derived by assuming the total number of different curvatures in the complete set to be one thousand and the lists of two makers shows satisfactory agreement.
Article PDF
Rights and permissions
About this article
Cite this article
Societies and Academies. Nature 103, 159–160 (1919). https://doi.org/10.1038/103159a0
Issue Date:
DOI: https://doi.org/10.1038/103159a0