Meniscus lenses
Positive meniscus lens is a convex-concave lens
thicker at the center than at the edges. It is used to minimize
spherical aberration. When used in combination with another lens,
it’s will shorten the focal length, and increase the NA of system.
Negative
meniscus lens is a convex-concave lens thinner at the center
than edges. It increases the divergence of the beam without introducing
any significant spherical aberration. When used in combination with
another lens, it will increase the focal length, and decrease the
NA of the system.
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