A meniscus corrector is a negative meniscus lens that is used to correct

spherical aberration In optics, spherical aberration (SA) is a type of aberration found in optical systems that have elements with spherical surfaces. Lenses and curved mirrors are prime examples, because this shape is easier to manufacture. Light rays that strik ...

image-forming optical system 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 traditiona ...

s such as

catadioptric telescope A catadioptric optical system is one where refraction and reflection are combined in an optical system, usually via lenses ( dioptrics) and curved mirrors ( catoptrics). Catadioptric combinations are used in focusing systems such as searchlights ...

s. It works by having the equal but opposite

of the

objective Objective may refer to: * Objective (optics), an element in a camera or microscope * ''The Objective'', a 2008 science fiction horror film * Objective pronoun, a personal pronoun that is used as a grammatical object * Objective Productions, a Brit ...

it is designed to correct (usually a spherical mirror).

Types

Meniscus correctors are used as full aperture correctors, most commonly in a Maksutov telescope sub type called the Gregory or “spot” Maksutov–Cassegrain telescope. They are also used in the Bouwers meniscus telescope. There are Maksutov variations that use the same principle but place the meniscus lens as a sub-aperture corrector near the focus of the objective. There are other sub-aperture meniscus corrector catadioptric telescopes such as the Argunov–Cassegrain telescope and the Klevtsov–Cassegrain telescope.

Invention

The idea of using the spherical aberration of a meniscus lens to correct the opposite aberration in a spherical

dates back as far as W. F. Hamilton’s 1814

Hamiltonian telescope Hamiltonian may refer to: * Hamiltonian mechanics, a function that represents the total energy of a system * Hamiltonian (quantum mechanics), an operator corresponding to the total energy of that system ** Dyall Hamiltonian, a modified Hamiltonian ...

, in Colonel A. Mangin's 1876

Mangin mirror In optics, a Mangin mirror is a negative meniscus lens with the reflective surface on the rear side of the glass forming a curved mirror that reflects light without spherical aberration if certain conditions are met. This reflector was invented i ...

, and also appears in

Ludwig Schupmann Ludwig Ignaz Schupmann (23 January 1851 in Geseke (Westphalia), Germany – 2 October 1920 also in Geseke) was a German professor of architecture and an optical designer. He is principally remembered today for his Medial and Brachymedial telescopes ...

’s Schupmann medial telescope near the end of the 19th century. After the invention of the wide-field

Schmidt camera A Schmidt camera, also referred to as the Schmidt telescope, is a catadioptric astrophotographic telescope designed to provide wide fields of view with limited aberrations. The design was invented by Bernhard Schmidt in 1930. Some notable e ...

in the early 1930s, at least four optical designers in early 1940s war-torn Europe came up with the idea of replacing the complicated Schmidt corrector plate with a simpler meniscus lens, including Albert Bouwers, Dmitri Dmitrievich Maksutov, K. Penning, and

Dennis Gabor Dennis Gabor ( ; hu, Gábor Dénes, ; 5 June 1900 – 9 February 1979) was a Hungarian-British electrical engineer and physicist, most notable for inventing holography, for which he later received the 1971 Nobel Prize in Physics. He obtained ...

. All of these designs used full aperture correctors (a ''meniscus corrector shell'') to create a wide-field telescope with little or no

coma A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to respond normally to painful stimuli, light, or sound, lacks a normal wake-sleep cycle and does not initiate voluntary actions. Coma patients exhi ...

astigmatism Astigmatism is a type of refractive error due to rotational asymmetry in the eye's refractive power. This results in distorted or blurred vision at any distance. Other symptoms can include eyestrain, headaches, and trouble driving at n ...

. Albert Bouwers built a prototype meniscus telescope in August 1940 and patented it in February 1941. His design had the mirror and meniscus lens with surfaces that had a common centre of curvature, called a "''concentric''" or "''monocentric''" telescope. The design had an ultrawide field of view but did not correct

chromatic aberration In optics, chromatic aberration (CA), also called chromatic distortion and spherochromatism, is a failure of a lens to focus all colors to the same point. It is caused by dispersion: the refractive index of the lens elements varies with the w ...

and was only suitable as a monochromatic astronomical camera. Dmitri Maksutov built a prototype for a similar type of meniscus telescope, the Maksutov telescope, in October 1941, and patented it in November of that same year. His design corrected most spherical aberration and also corrected for chromatic aberration by placing a weakly negative-shaped meniscus corrector closer to the primary mirror.

’s 1941 design was a non-monocentric meniscus corrector.Handbook of Optical Systems, Survey of Optical Instruments, by Herbert Gross, Hannfried Zügge, Fritz Blechinger, Bertram Achtner, page 806
/ref> Wartime secrecy kept these designers from knowing about each other's design, making each invention independent.

Types

Invention

See also

References

Further reading