 |
|
a larger diameter collimated laser beam. The main types of beam expanders: Keplerian and Galilean. In its
simplest form, the Galilean type consists of a positive and a negative focal length lens whereas the Keplerian
type consists of two positive focal length lenses. Both designs provide a certain angular magnification, called
the Expander Power. The beam diameter is first increased in size by this power and then the beam divergence is
reduced by the same power. This combination yields a beam that is not only larger, but one that is also highly
collimated. The result is a smaller beam at a large distance when compared to the laser alone. See the below
equation:
|
BL |
= |
ß + ØL (0.3048) |
|
BL |
= |
Beam Diameter (mm) at distance
L |
|
ß |
= |
Increase in Beam Diameter |
|
|
= |
Beam Diameter (mm) x Expander
Power |
|
Ø |
= |
Decrease in Beam
Divergence |
|
|
= |
Beam Divergence (mrad) Expander
Power |
|
L |
= |
distance
(ft.) |