1. Types

2. See also

3. References

In optics, a doublet is a type of lens made up of two simple lenses paired together. Such an arrangement allows more optical surfaces, thicknesses, and formulations, especially as the space between lenses may be considered an "element." With additional degrees of freedom, optical designers have more latitude to correct more optical aberrations more thoroughly.

Types

Doublets can come in many forms, though most commercial doublets are achromats, which are optimized to reduce chromatic aberration while also reducing spherical aberration and other optical aberrations. The lenses are made from glasses with different refractive indices and different amounts of dispersion. Often one element is made from crown glass and the other from flint glass. This combination produces a better image than a simple lens. Some Trilobites, which are now extinct, had natural doublet lenses in their eyes.^[1] Apochromats can also be made as doublets.

Doublets can be air-spaced, cemented, or "oiled". Oiled doublets hold the optical fluid in place with surface tension alone. In a cemented doublet, the lenses are held together by an adhesive with mechanical strength, such as optically transparent epoxy. Canada balsam was traditionally used for this purpose. Some doublets use no adhesive between the lenses, relying on external fixturing to hold them together, either because the optical design requires a gap or because thermal expansion differences between the two lenses won't allow cementing.^[2] These are called "un-cemented", "air-spaced" or "broken contact" doublets.^[3] A sub-type of air-spaced doublet is the dialyte, a design where elements are widely spaced to save on the amount of glass used or where the elements cannot be cemented because they have strongly dissimilar curvatures.^[4]

See also

• Achromatic lens
• Triplet lens

References

• Aleksandr Yarkin
• Aleksandr Yaroslavich Nevskij
• Aleksandr Yashan
• Aleksandr Yatsevich
• Aleksandr Yatskevich
• Aleksandr Yatsko
• Aleksandr Yedeshko
• Aleksandr Yefremenko
• Aleksandr Yefremov
• Aleksandr Yefremov (politician)
• Aleksandr Yegurnev
• Aleksandr Yeliseyenok
• Aleksandr Yenko
• Aleksandr Yerkin
• Aleksandr Yermakovich
• Aleksandr Yermilov
• Aleksandr Yerokhin
• Aleksandr Yerokhin (footballer, born 1985)
• Aleksandr Yeschenko
• Aleksandr Yeshchenko
• Aleksandr Yeshkin
• Aleksandr Yevgenyev
• Aleksandr Yevgenyevich Nechayev
• Aleksandr Yevgenyevich Nikulin
• Aleksandr Yevgenyevich Zaikin