In
optics, an image-forming optical system is a system capable of being used for
imaging. The diameter of the aperture of the main objective is a common criterion for comparison among optical systems, such as large telescopes.
The two traditional systems are
mirror-systems (
catoptrics) and
lens-systems (
dioptrics), although in the late twentieth century,
optical fiber was introduced. Catoptrics and dioptrics have a
focal point
Focal point may refer to:
* Focus (optics)
* Focus (geometry)
* Conjugate points, also called focal points
* Focal point (game theory)
* Unicom Focal Point, a portfolio management software tool
* Focal point review, a human resources process for ...
, while optical fiber transfers an image from one plane to another without an optical focus.
Isaac Newton is reported to have designed what he called a ''
catadioptrical phantasmagoria'', which can be interpreted to mean an elaborate structure of both mirrors and lenses.
Catoptrics and optical fiber have no
chromatic aberration, while dioptrics need to have this error corrected. Newton believed that such correction was impossible, because he thought the path of the light depended only on its color. In 1757
John Dollond was able to create an achromatised dioptric, which was the forerunner of the
lenses
A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements ...
used in all popular photographic equipment today.
Lower-energy X-Rays are the highest energy electromagnetic radiation that can be formed into an image, using a
Wolter telescope. There are three types of Wolter telescopes
is typically the longest wavelength that are handled optically, such as in some large telescopes.
References
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Optics
Telescopes