Dialyte lens
Encyclopedia
A dialyte lens is a compound lens
design that corrects optical aberrations where the lens elements are widely air-spaced. The design is used to save on the amount of glass used for specific elements or where elements can not be cemented because they have dissimilar curvatures. The word dialyte means "parted", "loose" or "separated".
Hamiltonian telescope and Alexander Rogers 1828 proposals for dialytic refractor. The goal was to combine a large crown glass
objective
with a much smaller flint glass
down stream to make an achromatic lens
, since flint glass at that time was very expensive. Dialyte designs were also used the Schupmann medial telescope designed by German optician Ludwig Schupmann
near the end of the 19th century and in John Wall's
1999 "Zerochromat" retrofocally corrected dialytic refractor.
: the outer pair are biconvex and the inner pair are biconcave. The symmetrical structure provides good correction for many aberrations.
The Aviar type of lens (Taylor Hobson
) is similar but is considered to have a different origin, from the splitting of the central biconcave element of the Cooke triplet
. The resulting two biconcave elements are closer together than in the Dialyte/Celor
design.
Lens (optics)
A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens consists of a single optical element...
design that corrects optical aberrations where the lens elements are widely air-spaced. The design is used to save on the amount of glass used for specific elements or where elements can not be cemented because they have dissimilar curvatures. The word dialyte means "parted", "loose" or "separated".
Dialyte telescopes
The idea of widely separating the color correcting elements of a lens dates back to W. F. Hamilton's 1814 catadioptricCatadioptric
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,...
Hamiltonian telescope and Alexander Rogers 1828 proposals for dialytic refractor. The goal was to combine a large crown glass
Crown 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...
objective
Objective (optics)
In an optical instrument, the objective is the optical element that gathers light from the object being observed and focuses the light rays to produce a real image. Objectives can be single lenses or mirrors, or combinations of several optical elements. They are used in microscopes, telescopes,...
with a much smaller flint glass
Flint glass
Flint glass is optical glass that has relatively high refractive index and low Abbe number. Flint glasses are arbitrarily defined as having an Abbe number of 50 to 55 or less. The currently known flint glasses have refractive indices ranging between 1.45 and 2.00...
down stream to make an achromatic lens
Achromatic lens
An achromatic lens or achromat is a lens that is designed to limit the effects of chromatic and spherical aberration. Achromatic lenses are corrected to bring two wavelengths into focus in the same plane....
, since flint glass at that time was very expensive. Dialyte designs were also used the Schupmann medial telescope designed by German optician Ludwig Schupmann
Ludwig Schupmann
Ludwig Ignaz Schupmann was a German professor of architecture and an optical designer...
near the end of the 19th century and in John Wall's
John Wall (inventor)
John Wall is a British design engineer, amateur astronomer, amateur telescope maker and member of the British Astronomical Association, now living Coventry England.-Biography:...
1999 "Zerochromat" retrofocally corrected dialytic refractor.
Dialyte camera lenses
There are many types of dialyte camera lenses. One type is a symmetrical design consisting of four air spaced lensesLens (optics)
A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens consists of a single optical element...
: the outer pair are biconvex and the inner pair are biconcave. The symmetrical structure provides good correction for many aberrations.
The Aviar type of lens (Taylor Hobson
Cooke Optics
Cooke Optics Ltd. is a camera lens manufacturing company based in Leicester, known earlier as Taylor, Taylor and Hobson and then Taylor Hobson. T. S. Taylor, an optician, his brother W. Taylor, an engineer, and a Mr Hobson, a businessman, formed the company in 1886.The name Cooke originally came...
) is similar but is considered to have a different origin, from the splitting of the central biconcave element of the Cooke triplet
Cooke triplet
The Cooke triplet is a photographic lens designed and patented in 1893 by Dennis Taylor who was employed as chief engineer by T. Cooke & Sons of York...
. The resulting two biconcave elements are closer together than in the Dialyte/Celor
Celor lens
A Celor lens is a highly corrected lens of the Dialyt type, designed for process photography, involving reproduction at or near 1:1 scale....
design.