| 摘要 |
<p>The aid increases the visual angle using a single diaphragm. This has a circular hole of roughly a few tenths of a millimetre in diameter. This avoids light rays being refracted by the cornea or the lens of the eye. Rays going through the opening are centred on the cornea, pupil and eye lens and directed straight at the retina. This forms an image of the object looked at.</p> |
