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Beam Expander Theoretical Research and Selection Guide
Posted on:
2022-04-22
The Beam Expander expands the diameter of a collimated input beam to a larger collimated output beam. Beam expanders are often used in applications such as laser scanning, interferometry or telemetry. Today's laser beam expanders are all afocal system designs developed from a well-established optical telescope foundation. In such systems, object rays enter the optical axis of the inner optical element in a parallel manner and exit in a parallel manner. This means that the entire system has no focal length.
Traditionally, optical telescopes were mainly used to observe distant objects, such as celestial bodies in the universe. Optical telescopes can be mainly divided into two categories: refracting telescopes and reflecting telescopes. Refractor telescopes use lenses to refract or bend light, while reflecting telescopes use mirrors to reflect light.
Beam Expanders can be divided into two categories: Kepler-style telescopes and Galileo-style telescopes. A Kepler-style telescope consists of lenses of positive focal length separated by the sum of their focal lengths. The lens closest to the observed object or source image is called the objective lens, and the lens closest to the human eye or image is called the imaging lens.
The Beam Expander consists of a positive and negative lens, the lenses are also separated by the sum of their focal lengths. However, because one of the lenses is negative, the distance between the two lenses is shorter than that of a Kepler-style telescope. Using the effective focal length between the two lenses gives a good approximate total length, while using the back focal length gives the most accurate length.
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