The Collaborative International Dictionary
Iris diaphragm \I"ris di"a*phragm\ An adjustable diaphragm, reminiscent of the iris of the eye in its action, by which the diameter of an approximately circular opening may be controlled, as for regulating the aperture of a lens; it consists of a number of movable thin curved plates fastened at regular intervals around the inside of a ring, the positions of which are simultaneously adjusted by a single knob on the outside of the lens. It is used in cameras and microscopes.
WordNet
n. diaphragm consisting of thin overlapping plates that can be adjusted to change the diameter of a central opening [syn: iris]
Usage examples of "iris diaphragm".
A well-modulated iris diaphragm, stopping down rapidly when the sun comes out, can make all the difference between seeing a predator in time to escape and being dazzled for a fatal instant.
The nose cap of the second had opened fanwise, like an iris diaphragm, and a pair of jointed metal arms were folded inside, hugging a medium-sized diamond.