Images And The Eye – Optics

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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

techniques.

— 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,

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