PHYSIOLOGIC LENSLESS SPECTACLES

This article is only available in the PDF format. Download the PDF to view the article, as well as its associated figures and tables.

For a long time the following facts have been known :

1. Light passing through a small hole or a transparent spot in an opaque surface may, by virtue of its rectilinear propagation, be caused to form sharply defined images on a surface or screen of suitable character. Simple and practical cameras have utilized this principle.

2. Such a small hole in a diaphragm placed in the focal axis of a lens sharpens the image formed by the lens by reducing aberrations of various kinds due to imperfections in the lens, etc., but the image is less bright. The range of the screen on which apparent sharp focusing of the image may be obtained varies indirectly with the size of the hole in the diaphragm, and the actual measurements vary with different observers. For example, using an ordinary camera, with the diaphragm set at 1 inch (2.5 cm.), one worker obtained