Lenses

A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. Lenses are classified as single lenses, cylindrical lenses and achromatic lenses. A simple lens is a lens consisting of a single optical element. A compound lens is an array of simple lenses with a common axis; the use of multiple lenses allows more optical aberrations to be corrected than is possible with a single lense. Lenses have many applications ranging from the simple collection of a laser beam to precise imaging and image transfer.

Lenses	Materials	Illustration	Description
Plano-convex	BK7, Germanium,  Zinc Selenide, Barium Fluoride, Calcium Fluoride, Silicon		Positive focus length. Most suitable where one conjugate is more than five times the other, e.g. in sensor application or for use with near collimated light.
Double-convex	BK7, Germanium,  Zinc Selenide, Barium Fluoride, Calcium Fluoride, Silicon		Most suitable where the conjugates are on opposite sides of the lenses and the ratio of the distances is less than 5:1, e.g. as simple image relay components.
Plano-concave	BK7, Germanium,  Zinc Selenide, Barium Fluoride, Calcium Fluoride, Silicon		Negative lens with the form most suitable where one conjugates is more than fives times the other, e.g. producing divergent light from a collimated input beam.
Double-concave	BK7, Germanium,  Zinc Selenide, Barium Fluoride, Calcium Fluoride, Silicon		Negative lens with the form most suited to producing diverging light or a virtual image, where the input light is converging.
Cylindrical Lens	BK7, Germanium,  Zinc Selenide, Barium Fluoride, Calcium Fluoride, Silicon		Used to provide focusing power in one section only. For illumination or detection of light from line sources. Also used to anamorphic compression of beams and images