Appendix 1: Region Of Interest (Roi) - Helios 3120HD Series Operation Manual

Appendix 1: Region of Interest (ROI)

The ROI sets the area of the detector that the AGC will react to.
Changing the ROI to ignore an unimportant area of the scene can often improve image quality in the more
important area of the scene. Since the AGC algorithm looks for the number of pixels with a given value and
distributes those pixels evenly, disregarding unimportant pixels may have a beneficial effect on the output.
An example situation of this would be excluding the sky. The sky is very cold and having a large portion of
the scene containing the sky will drastically change the output of the AGC algorithm. The same is true for
bodies of water, large items that are particularly hot or cold, etc. The user is encouraged to try different ROI
settings for a particular scene.
The sample images shown above represent potential image improvements that can be achieved by adjust-
ing the ROI to match the scene being viewed. In images A and B, the sky consumes a large percentage of
the image. When the ROI is set for full screen as in image A, the AGC automatics respond more to the sky
than the area of importance. By changing the ROI to ignore the sky as shown in image B, the image qual-
ity can be noticeably improved. However, if the camera is tilted down to view a different scene as shown in
images C and D, the smaller region of interest in image D may not produce as good of an image as image
C with the full screen ROI.
For this reason, the ROI is included as part of the 5970 preset feature. An operator can store a preset view-
ing scene A/B with the ROI set per image B, and store another preset viewing scene C/D with the full screen
ROI as shown in image C.
The operator must be aware that when manually moving the camera away from a preset position, all of
the camera parameters established as part of the last preset position will remain in effect. The operator
may need to RECALL the User Settings or the Factory Default settings to regain the best overall operating
parameters.
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