A triplet lens is a

compound lens A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), ...

consisting of three single

lenses A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), ...

. The triplet design is the simplest to give the required number of

degrees of freedom Degrees of freedom (often abbreviated df or DOF) refers to the number of independent variables or parameters of a thermodynamic system. In various scientific fields, the word "freedom" is used to describe the limits to which physical movement or ...

to allow the lens designer to overcome all

Seidel aberration In optics, aberration is a property of optical systems, such as lenses, that causes light to be spread out over some region of space rather than focused to a point. Aberrations cause the image formed by a lens to be blurred or distorted, with th ...

The three lenses may be cemented together, as in the Steinheil triplet or the

Hastings triplet A triplet lens is a compound lens 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 three lenses may be c ...

. Or a triplet may be designed with three spaced glasses, as in the Cooke triplet. The former has the advantage of higher optical throughput due to fewer air-glass interfaces, but the latter provides greater flexibility in aberration control, as the internal surfaces are not confined to have the same radii of curvature. BelOMO 10× achromatic triplet loupe 1

Jewellers' loupes typically use a triplet lens.

References

Lenses 3 (number) {{optics-stub

See also

References