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Glossary Terms

The verb to Collimate is derived from the Latin collineare, to align.[1] It refers to the parallel alignment of light rays (making them collinear), or of two or more optical instruments (such as a large telescope with the smaller one used to direct it).

A collimator is an instrument for producing parallel rays, for use in adjustment of other instruments.[1] These parallel rays may be used to simulate the rays from an object at infinite distance, and so are appropriate in adjusting the focus scale of a camera lens at infinity.

It has become a common misuse to refer to this adjustment itself as 'collimation'. It is possible to check the infinity-focus position of a lens using the split prism focus aids commonly provided in a manual-focus SLR camera.


  1. 1.0 1.1 Concise Oxford Dictionary. Ninth edition, 1995, Oxford University Press, p259.