Collimator
（重定向自Collimating lens）
![An example of an optical collimator with a bulb, an aperture (B), and a positive lens (L)](/Images/godic/202501/05/Collimator.svg4331.png")
![Collimators used to record gamma rays and neutrons from a nuclear test.](/Images/godic/202501/05/NNSA-NSO-1904332.jpg")
![How a Söller collimator filters a stream of rays. Top: without a collimator. Bottom: with a collimator.](/Images/godic/202501/05/Collimator2.svg4332.png")
![Collimator for a neutron stream, University of Washington cyclotron](/Images/godic/202501/05/UW_Collimator4332.jpg")
A collimator is a device that narrows a beam of particles or waves. To narrow can mean either to cause the directions of motion to become more aligned in a specific direction (i.e., make collimated light or parallel rays), or to cause the spatial cross section of the beam to become smaller (beam limiting device).