IMAGES AND THE EYE – OPTICS
Optics is the field that explores the production of images. In particular,
ptics is the study and use of light production, of light transport, and
f light and image detection. With this definition of optics, we note directly
that classical electrodynamics can describe only the transport of light. The production
and the detection of light are always quantum effects. Every lamp is a device based on
quantumphysics. Every detector of light, including the eye, is based on quantum physics.
Therefore, in this chapter we mainly explore the motion of light and the way it forms
images, and give only a short introduction into light sources and the eye.
Ways to produce images
Producing images is an important part of modern society. The quality of images depends
on the smart use of optics, electronics, computers and materials science. Despite the
long history of optics, there are still new results in the field. Images, i.e., two or threedimensional
reproductions, can be taken by at least six groups of techniques:
— Photography uses a light source, lenses and film – or another large area detector. Photography
can be used in reflection, in transmission, with phase-dependence, with
various illuminations, and with light sources and detectors for various wavelengths.
— Opticalmicroscopy uses a light source, lenses and film(or another large area detector).
If the illumination is through the sample, in transmission, one speaks of bright-field
microscopy. (Variations use coloured or polarizing filters.) If the illumination is from
the side, one speaks of oblique microscopy. If the illumination is confined to an outer
ring of light, one speaks of dark-field microscopy. An even more elaborate illumination
system, using plane waves, allows phase-contrast microscopy. (It was invented by
Frits Zernike in the 1930s and earned him the Nobel Prize in Physics in 1953.) If one
splits a polarized illumination beam into two components that pass the sample at
close (but not identical) locations, and then recombines them afterwards, one speaks
of differential interference contrast microscopy. If a sample is treated with a fluorescent
dye, the illuminating light is filtered out, and only the fluorescence is observed,
one speaks of fluorescence microscopy. The image quality of expensive microscopes
can be further improved with the help of a computer, with the help of deconvolution
— Telescopy is used most of all in geodesy and astronomy. The most advanced astronomical
telescopes can compensate star images for the effects of the turbulence of
the atmosphere; they can also take images at various wavelengths,