An optical beam expander (also known as a collimator or up-collimator) is a two, or more, element optical system that changes the divergence characteristics and the size of the beam. They take a beam of light and expand its size. They are also used to reduce the beam diameter which may be useful when using acousto- or electro-optic modulators. They are typically used in systems with a long beam path to keep the beam collimated, or to vary the focus spot size for a given lens.
A laser beam expander works in such a way that the input beam is expanded to a larger diameter. The concepts are derived from the fundamental principals of telescopic design. When a collimated laser beam is input to one side of the beam expander, a collimated beam is output from the opposite end. The object space and image space rays converge at infinity. This characteristic defines a beam expander as an afocal system. 
There are two types of afocal beam expanders, named after their historical precedents. A Galilean beam expander consists of one diverging lens and one converging lens. The lenses are separated by the sum of their focal points, except that the diverging lens has a negative focal length. A beam input into the diverging lens propagates to the converging lens without reaching an intermediate focal point. A Keplerian beam expander has two converging lenses, separated by the sum of their focal lengths. A collimated input beam converges to a focal point between the two lenses, then diverges to the output lens.
Creating and selecting an optical beam expander takes the same attention to detail as selecting other optical components. Universe Optics specializes in designing and manufacturing high-quality, precision lenses for your specific application.
Laser systems have become commonplace in applications across industries from medical treatment to materials processing. Beam expansion or reduction is a common application requirement in most labs using lasers or light sources and optics. A laser beam expander is often a crucial element in the success of individual systems. For high-powered sources, the addition of a beam expander can provide a controlled reduction of power density. Reducing divergence can assist in alignment and reduce the spot size at the final focus at the beam. Reducing divergence to control collimation also benefits demanding laser applications, particularly in long-path-length systems. Variable laser beam expanders may be necessary to compensate to variations in laser source beam size from unit to unit.
A multiple-prism beam expander is a unique beam magnification means which expand a light beam without focusing it and with the added option of achromaticity. A multiple-prism beam expander usually deploys two to five prisms to yield large, one-dimensional beam expansion factors. The use of this type of beam expander can be found in such applications as: Astronomy, Iterferometry, Intracavity beam expansion and Extracavity beam expansion, and Microscopy.
Whether your design is an afocal optical beam expander or a multiple-prism beam expander, UKA using cutting edge technology to create the precise lens.