Mangin mirror
Encyclopedia
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
. This reflector was invented in 1876 by a French officer Alphonse Mangin as an improved catadioptric
reflector for search lights and is also used in other optical devices.
with spherical surfaces of different radii with the reflective coating on the shallower rear surface. The spherical aberration
normally produced by the simple spherical mirror surface is canceled out by the opposite spherical aberration produced by the light traveling through the negative lens. Since light passes through the glass twice, the overall system acts like a triplet lens
. The Mangin mirror was invented in 1876 by a French military engineer named Colonel Alphonse Mangin as a substitute for the more difficult to manufacture parabolic reflecting
mirror for use in searchlights. Since the catadioptric design eliminated most of the off-axis aberration found in parabolic mirrors, Mangin mirrors had the added advantage of producing a nearly true parallel beam of light. They saw use in the late 19th century as reflectors for naval search lights. Its use in military applications was limited, since glass reflectors of any kind were thought to be too fragile and susceptible to enemy gunfire.
such as search lights, headlamp
s, aircraft gunsights and head-mounted display
s. Many Catadioptric telescopes use negative lenses with a reflective coating on the backside that are referred to as "Mangin mirrors", although they are not single-element objectives like the original Mangin, and some, like the Hamiltonian telescope, predate the Mangin's invention by over 60 years. Catadioptric mirrors similar to the Mangin are found in the Klevtsov–Cassegrain, Argunov–Cassegrain telescopes, and Ludwig Schupmann
's Schupmann medial telescope. They are also used in compact catadioptric photographic lens designs that save on mass since aberration can be corrected by mirror itself.
Optics
Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
, a Mangin mirror is a negative meniscus lens with the reflective surface on the rear side of the glass forming a curved mirror
Curved mirror
A curved mirror is a mirror with a curved reflective surface, which may be either convex or concave . Most curved mirrors have surfaces that are shaped like part of a sphere, but other shapes are sometimes used in optical devices...
that reflects light without spherical aberration
Spherical aberration
thumb|right|Spherical aberration. A perfect lens focuses all incoming rays to a point on the [[Optical axis|optic axis]]. A real lens with spherical surfaces suffers from spherical aberration: it focuses rays more tightly if they enter it far from the optic axis than if they enter closer to the...
. This reflector was invented in 1876 by a French officer Alphonse Mangin as an improved catadioptric
Catadioptric
A catadioptric optical system is one where refraction and reflection are combined in an optical system, usually via lenses and curved mirrors . Catadioptric combinations are used in focusing systems such as search lights, headlamps, early lighthouse focusing systems, optical telescopes,...
reflector for search lights and is also used in other optical devices.
Description
The Mangin mirror's construction consists of a concave (negative meniscus) lens made of crown glassCrown glass (optics)
Crown glass is type of optical glass used in lenses and other optical components. It has relatively low refractive index and low dispersion...
with spherical surfaces of different radii with the reflective coating on the shallower rear surface. The spherical aberration
Spherical aberration
thumb|right|Spherical aberration. A perfect lens focuses all incoming rays to a point on the [[Optical axis|optic axis]]. A real lens with spherical surfaces suffers from spherical aberration: it focuses rays more tightly if they enter it far from the optic axis than if they enter closer to the...
normally produced by the simple spherical mirror surface is canceled out by the opposite spherical aberration produced by the light traveling through the negative lens. Since light passes through the glass twice, the overall system acts like a triplet lens
Triplet lens
A triplet lens is an optical device consisting of three single lenses. The triplet design is the simplest to give the required number of degrees of freedom to allow the lens designer to overcome all Seidel aberrations....
. The Mangin mirror was invented in 1876 by a French military engineer named Colonel Alphonse Mangin as a substitute for the more difficult to manufacture parabolic reflecting
Parabolic reflector
A parabolic reflector is a reflective device used to collect or project energy such as light, sound, or radio waves. Its shape is that of a circular paraboloid, that is, the surface generated by a parabola revolving around its axis...
mirror for use in searchlights. Since the catadioptric design eliminated most of the off-axis aberration found in parabolic mirrors, Mangin mirrors had the added advantage of producing a nearly true parallel beam of light. They saw use in the late 19th century as reflectors for naval search lights. Its use in military applications was limited, since glass reflectors of any kind were thought to be too fragile and susceptible to enemy gunfire.
Applications
Mangin mirrors are used in illumination and image forming opticsImage-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 criteria for comparison among optical systems, such as large telescopes....
such as search lights, headlamp
Headlamp
A headlamp is a lamp, usually attached to the front of a vehicle such as a car or a motorcycle, with the purpose of illuminating the road ahead during periods of low visibility, such as darkness or precipitation. Headlamp performance has steadily improved throughout the automobile age, spurred by...
s, aircraft gunsights and head-mounted display
Head-mounted display
A head-mounted display or helmet mounted display, both abbreviated HMD, is a display device, worn on the head or as part of a helmet, that has a small display optic in front of one or each eye .- Overview :...
s. Many Catadioptric telescopes use negative lenses with a reflective coating on the backside that are referred to as "Mangin mirrors", although they are not single-element objectives like the original Mangin, and some, like the Hamiltonian telescope, predate the Mangin's invention by over 60 years. Catadioptric mirrors similar to the Mangin are found in the Klevtsov–Cassegrain, Argunov–Cassegrain telescopes, and Ludwig Schupmann
Ludwig Schupmann
Ludwig Ignaz Schupmann was a German professor of architecture and an optical designer...
's Schupmann medial telescope. They are also used in compact catadioptric photographic lens designs that save on mass since aberration can be corrected by mirror itself.