A meniscus corrector is a negative meniscus lens that is used to correct spherical aberration in image-forming optical systems such as catadioptric telescopes. It works by having the equal but opposite spherical aberration of the objective it is designed to correct (usually a

spherical mirror A curved mirror is a mirror with a curved reflecting surface. The surface may be either ''convex'' (bulging outward) or ''concave'' (recessed inward). Most curved mirrors have surfaces that are shaped like part of a sphere, but other shapes are ...

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 The Maksutov (also called a "Mak") is a catadioptric telescope design that combines a spherical mirror with a weakly negative meniscus lens in a design that takes advantage of all the surfaces being nearly "spherically symmetrical". The negativ ...

. They are also used in the

Bouwers meniscus telescope Albert A. Bouwers (1893–1972) was a Dutch optical engineer.Ian Ridpath, "Bouwers telescope", ''A Dictionary of Astronomy'', 199first sentence of article/ref> He is known for developing and working with X-rays and various optical technologies as a ...

. 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 objective 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, and also appears in Ludwig Schupmann’s Schupmann medial telescope near the end of the 19th century. After the invention of the wide-field Schmidt camera 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. 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 ni ...

. Albert Bouwers built a prototype

meniscus telescope A meniscus corrector is a negative meniscus lens that is used to correct spherical aberration in image-forming optical systems such as catadioptric telescopes. It works by having the equal but opposite spherical aberration of the objective it i ...

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 ...

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. Dennis Gabor’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