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Thermal images through cages
09-05-2012, 11:09 AM
Post: #1
Thermal images through cages
I use thermal imaging for research on thermal biology of birds and mammals. I have always been suprised when taking thermal images of caged birds that the wire mesh/cage bars often do not appear on the image and the full image of the bird can be seen.
I have 2 questions: (1) what is the physical explanation for this? and (2) what is the maximum bar width before they start to appear in the image?
Thanks, Dominic
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09-06-2012, 05:18 AM
Post: #2
RE: Thermal images through cages
Firstly there is an excellent post here http://forum.infraredtraining.com/showthread.php?tid=45

You will see the same thing with visual cameras, it depends on a number of factors, not just the bar width. The distance from the camera to the bar, distance from the bar to the object, depth of field, focal length etc etc should all have an influence.
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09-06-2012, 06:00 AM (This post was last modified: 09-06-2012 06:00 AM by Dominic McCafferty.)
Post: #3
RE: Thermal images through cages
Thanks, this is helpful to see how the focus of the grating dissapears. I guess that the closeness of the grid to the target is one of the most crucial factors: as viewed from a distance the grid is only blocking a relatively small percentage of the radiation received by the camera. It will reduce the total amount of radiation received and therefore this will account for the "defocussed grating adding its lower temperature radiation while blocking some of the target higher radiation at the same time". Hence the temperatures of birds I measure through a cage may be lower than if I measured them inside the cage.
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