Collimators, Autocollimators and Collimation

Collimators, Autocollimators and Collimation Demystified

Updated 14 July 2020

An Autocollimator is a device that projects an image, usually focused at infinity, and allows the reflection of that image (typically by a mirror) to be observed through an eyepiece and small angular deflections of the image to be measured accurately against a graduated reticle.

In industry, autocollimators are most frequently used for the non-contact measurement of small angles. Angles as small as 1 arc second (1/3600 degree) can be measured. This can be done effectively and accurately at long distances.

During the U.S. Apollo manned space program, the arms connecting the Saturn V rocket to its tower were aligned using autocollimators.

In optical testing of photographic and cinematographic lenses, autocollimators are used with special reticles to observe focus. In conjunction with a Focal Plane Micrometer very accurate measurements of focus, down to 0.001 mm [0.00004 in], can be made with properly calibrated equipment and proper procedures.

Back focus of photographic and cinematographic lenses is always set at infinity focus (∞ mark on the focus scale), using an autocollimator, or a non reflex collimator and focal plane microscope.

Other distances on the focus scale of a cine lens are normally calibrated at the appropriate finite distance using a high resolution focus target and a focal plane micrometer. Cooke Optics in UK for example has a 10m [33 ft] focus system mounted on one end of the lens assembly floor.

Lens Testing Systems main page


All text and photos ©2016-2020 CinemaTechnic and Jorge Diaz-Amador. All text, images and other content on this site are original copyrighted works. CinemaTechnic and Jorge Diaz-Amador own exclusive rights to this content under the United States Copyright Act of 1976. Unauthorized use and/or duplication of this material without express and written permission from this website’s author and owner is strictly prohibited.

We are now actively monitoring for infringing websites that copy our content. Protection Status Protected by Copyscape

Optics and Optical Testing for Digital Cinema

error: Content is protected !!