GE Brivo OEC 715 Service Manual page 247

Brivo OEC 715/785/865 Mobile C-Arm X-Ray Product Service Manual
Definition for iris and Shutter position:
Make all iris and shutter leaves' penumbra (One/both/all of the leaves) is just out of
image circular mask.
Methods for measuring Iris diameter:
Situation_1. In below left image:
Via opening Iris, two opposite leaves are just out of circular mask. Other leaves have
been out of image (Image intensifier output window). Measure the linear distance
between two leaves' penumbra margins as the diameter of Iris.
Situation_2. In below right image,
Via opening Iris, only one leaves is just out of circular mask. Other leaves have been
out of light image (Image intensifier output window). So the linear distance between
two leaves' penumbra can't be measured. Herein measure the linear distance between
the leave margin and 180° light image (Image intensifier output window) margin as
the diameter of Iris.
4-36
Measurement margin
Circular mask