Optical glass ZK9 and ZF4 cemented lenses achromatic lenses
An achromatic lens, also referred to as an achromat, typically consists of two optical components cemented together, usually a positive low-index (crown) element and a negative high-index (flint) element. In comparison to a singlet lens, or singlet for short, which only consists of a single piece of glass, the additional design freedom provided by using a doublet design allows for further optimization of performance. Therefore, an achromatic lens will have noticeable advantages over a comparable diameter and focal length singlet.
An achromatic lens comes in a variety of configurations, most notably, positive, negative, triplet, and aspherized. It is important to note that it can be a doublet (two elements) or triplet (three elements); the number of elements is not related to the number of rays for which it corrects. In other words, an achromatic lens designed for visible wavelengths corrects for red and blue, independent of it being a doublet or triplet configuration. Refer to Figures 1 — 4 for illustrations of each type.
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Most commonly used and the earliest example of an achromatic lens is the achromatic doublet. An achromatic doublet is made from a pair of glasses, of which one is typically a concave and another is convex. The concave element of the doublet is composed of flint glass (with higher dispersion); the convex element, however, is made up of crown glass (with low dispersion). These two elements are placed (cemented) next to each other in such a manner that the chromatic aberration of the one element is balanced by the chromatic aberration of another. There are various types of achromatic lenses, which differ in the type of lens elements and optical properties.
++ Achromatic lens doublet as picture show is cemented by a diameter 21mm double convex spherical lens and a concave convex lens with diameter 21mm, used for optical instrument. Please contact us freely if it's interesting, we'd like to provide a best solution for your project and a best price for your reference. Thanks.