Spitzberg L A, Chen S
Optical Designs, Inc., Houston, Texas.
Optom Vis Sci. 1994 Oct;71(10):613-8. doi: 10.1097/00006324-199410000-00003.
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.
一种新型立式放大镜专为低视力患者设计，并已发展成为一种实用工具。这种变焦放大镜与目前现有的单透镜放大镜相比具有两个符合人体工程学的优点：当放大倍数改变时它能保持聚焦（变焦），并且它有更长的工作空间，允许使用同一个放大镜进行阅读和书写。这种双透镜变焦放大镜包含一个固定的正透镜和一个可移动的负透镜。利用对称条件，给出并求解了两个透镜焦距的一阶方程。设计了一组三个变焦放大镜——低倍、中倍和高倍——每个都有一个位置方便的清晰图像，放大倍数范围为2倍。这些装置的等效视放大率（对于+2.50D的附加镜）范围为6至23D。工作空间大约是同等放大倍数的单透镜立式放大镜的两倍。
