ALLIED Vision Technologies Stingray F-504 - Manual (Page 133)

Description of the data path
STINGRAY Technical Manual V4.4.4
131
How to store shading image
There are two storing possibilities:
• After generating the shading image in the camera, it can be uploaded to
the host computer for nonvolatile storage purposes.
• The shading image can be stored in the camera itself.
The following pictures describe the process of automatic generation of cor-
rection data. Surface plots and histograms were created using the ImageJ
program.
• On the left you see the source image with non-uniform illumination.
• The surface plot on the right clearly shows a gradient of the brightness
(0: brightest  255: darkest pixels).
• The histogram shows a wide band of gray values.
By defocusing the lens, high-frequency image data is removed from the
source image, therefore its not included in the shading image.
Figure 58: Shading correction: Source image with non-uniform illumination
surface plot
histogram
255.0
0.0
48
0.0
p
ix
els
640.0
pixe
ls
256 0
Count: 307200 Min: 79
Mean: 135.337 Max. 19
StdDev. 30.497 Mode:88 (4200)