Definition of aplanat in English:



  • A reflecting or refracting surface that is free from spherical aberration.

    • ‘All six lenses are fully corrected aplanats, so they can be mixed and matched in a focusing or non-focusing configuration to obtain the desired magnification.’
    • ‘We do not know what led him to this highly successful design, but it may have been an assembly of two Grubb-type landscape aplanats about a central stop.’
    • ‘When viewing resolution is less critical, the aplanats offer an economical alternative.’
    • ‘The term ‘aplanat’ means that the lens is corrected for coma, an image aberration which Rutten and & van Venroiij discuss very well in their book.’
    • ‘The aplanat is a variation of the simple Abbe, but usually of 3 element design which furnishes a more geometrically perfect cone of light, though its chromatic aberrations are similar to the Abbe's.’


Late 19th century: coined in German from Greek aplanētos free from error from a- not + planan wander.