Sekundäärilinssi

Sekundäärilinssi, often translated as secondary lens, is a term used in optics to describe a lens element that is not the primary lens responsible for the initial focusing of light. In complex optical systems, such as telescopes or microscopes, the primary objective lens gathers and converges light from a distant object. Subsequent lenses, or lens groups, may be employed to further modify this light path, correct aberrations, or magnify the intermediate image. These subsequent lenses are considered secondary lenses.

The function of a secondary lens can vary. It might be used to re-image the light onto a different focal plane, to correct optical distortions like chromatic aberration or spherical aberration introduced by the primary lens, or to adjust the magnification of the system. For example, in a refracting telescope, the objective lens is the primary, and the eyepiece acts as a secondary lens system that magnifies the image formed by the objective. In compound microscope objectives, multiple lens elements work together, with the overall objective acting as a primary system, and individual elements within it can be considered secondary in relation to each other's contribution to the final image formation. The design and placement of secondary lenses are critical for achieving high-quality optical performance, sharpness, and color fidelity.