What is a collimator?
A collimator (Latin: collineare: to lead in a straight line) is a lens or mirror system in an optical setup according to which divergent radiation emanating from a point light source is aligned parallel and imaged to infinity. The optical setup can also consist of a single spherical or aspherical lens.
In contrast to camera lenses, collimators often only image correctly near to their optical axis and are in such cases not suitable for image generation.
What do you need a collimator for?
A collimator is used to align divergent radiation parallel.
What types of collimators are there?
In an optical setup, mirror or lens systems are used as collimators.