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Parfocal lens. A parfocal lens is a lens that stays in focus when magnification / focal length is changed. There is inevitably some amount of focus error, but too small to be considered significant.
A zoom lens is a system of camera lens elements for which the focal length (and thus angle of view) can be varied, as opposed to a fixed-focal-length (FFL) lens (prime lens). A true zoom lens or optical zoom lens is a type of parfocal lens, one that maintains focus when its focal length changes. [1] Most consumer zoom lenses do not maintain ...
The focal length of an optical system is a measure of how strongly the system converges or diverges light; it is the inverse of the system's optical power. A positive focal length indicates that a system converges light, while a negative focal length indicates that the system diverges light. A system with a shorter focal length bends the rays ...
Birefringence means double refraction. It is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. [1] These optically anisotropic materials are described as birefringent or birefractive.
In optical engineering, an objective is an optical element that gathers light from an object being observed and focuses the light rays from it to produce a real image of the object. Objectives can be a single lens or mirror, or combinations of several optical elements. They are used in microscopes, binoculars, telescopes, cameras, slide ...
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