The Design of a Zoom Stand Magnifier—A New Low Vision Device

Autor: Larry A. Spitzberg, Shuai Chen
Rok vydání: 1994
Předmět:
Zdroj: Optometry and Vision Science. 71:613-618
ISSN: 1040-5488
DOI: 10.1097/00006324-199410000-00003
Popis: A new stand magnifier has been designed for low vision patients and developed into a working instrument. This zoom magnifier has two ergonomic advantages over the currently available single lens magnifiers: it stays in focus (zooms) as the power is changed and it has a longer working space to allow both reading and writing with the same magnifier. This two-lens zoom magnifier contains a stationary plus lens and a movable minus lens. Using a symmetry condition, first order equations are presented and solved for the two lens powers. A family of three zoom magnifiers was designed--low, medium, and high power--each with a conveniently positioned sharp image with a 2-fold range of power and magnification. The equivalent viewing powers of the units (for a +2.50 D add) range from 6 to 23 D. The working spaces are approximately double that of comparable power single lens stand magnifiers.
Databáze: OpenAIRE
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