4 Functionality
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b l a c k r e f e r e n c e
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Figure 4.35: Schematic presentation of the offset correction algorithm
How to Obtain a Black Reference Image
In order to improve the image quality, the black reference image must meet certain demands.
The detailed procedure to set the black reference image is described in Section
6.1.5.
•
The black reference image must be obtained at no illumination, e.g. with lens aperture
closed or closed lens opening.
•
It may be necessary to adjust the black level offset of the camera. In the histogram of the
black reference image, ideally there are no grey levels at value 0 DN after adjustment of
the black level offset. All pixels that are saturated black (0 DN) will not be properly
corrected (see Fig. 4.36). The peak in the histogram should be well below the hot pixel
threshold of 1008 DN @ 12 bit.
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Camera settings may influence the grey level. Therefore, for best results the camera
settings of the black reference image must be identical with the camera settings of the
image to be corrected.
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Histogram of the uncorrected black reference image
Grey level, 12 Bit [DN]
Relative number of pixels [−]
black level offset ok
black level offset too low
Figure 4.36: Histogram of a proper black reference image for offset correction
58
Summary of Contents for SM2-D1312-TI6455
Page 1: ...User Manual SM2 D1312 TI6455 VisionCam PS CMOS DSP Camera MAN060 05 2013 V1 0...
Page 2: ......
Page 4: ...2...
Page 8: ...CONTENTS 6...
Page 48: ...4 Functionality Figure 4 28 Example of decimation 2 on image of injection needle 46...
Page 80: ...4 Functionality 78...
Page 110: ...6 Framework Functionalities 108...
Page 116: ...8 Warranty 114...
Page 118: ...9 References 116...
Page 122: ...A Pinouts 120...
Page 123: ...B Revision History Rev 1 0 May 2013 First version 121...