Question

Where are the Galilean Beam Expander and Keplerian Beam Expander used? Give at least two examples of each and elaborate on their uses.

Answer 1

First of all we will see what are Beam expanders.

Beam expanders which are also known as collimators are used in systems with a long beam path to keep the beam parallely alligned, or to vary the focus spot size for a given focusing lens. Beam expanders are very useful in the applications which include interferometry, laser scanning and remote sensing.

Both Galilean Beam Expander and Keplerian Beam Expander are used in laser technology ,telescopes, i.e. refracting telescopes are divided into two types,namely Keplerian and Galilaen.

Used as Telescope:

A Keplerian telescope’s lenses have positive focal length and consists of two focusing lenses which are separated at a distance which is actually the sum of their focal lengths.

In the Galilean design one of the lenses is negative. Galilean telescope’s lenses, as Keplerian telescope’s lenses are separated by the sum of their focal lengths. One of the advantage of using this is its more compact design than Keplerian.