Iris Diaphragm

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iris diaphragm

[′ī·rəs ′dī·ə‚fram]
(anatomy)
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Iris Diaphragm

 

a type of stop that is often used in photographic lenses and other instruments to adjust the brightness of the image and to vary the depth of field. It consists of thin, opaque, crescent-shaped vanes that overlap one another, thus forming an approximately circular opening. By moving the stop ring on the lens or a lever connected to it, all the vanes are turned simultaneously, so that the objective’s opening (aperture ratio) is varied smoothly.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.