Balluff MATRIX VISION mvBlueNAOS, Technical Manual

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1.18.2.1.5 List-based defect Pixel correction on the camera As described before, it is possible to upload lists
of defect pixel onto the camera. Different algorithms can be used to determine whether a pixel is defective or not,
which is dependent of how much it is allowed a pixel to deviate, temperature, gain, and exposure time. As described
before, the list-based correction is deterministic, meaning it is exactly known which pixels will be corrected.
Anyhow, the list-based correction has some disadvantages:
• A default list is stored in the camera during production, but this might to fit to the target application because
of much different temperature / exposure time setting
→
It is necessary to create the list using a detection algorithm (or mvIMPACT Acquire support)
• During time and sensor aging, new defects could/will appear
• It doesn’t work in binning/decimation modes
• The memory for storing defective pixels is limited
1.18.2.1.6 Adaptive / algorithm-based correction on the camera In this case, the camera performs detection
and correction on-the-fly without using any defect-list.
The adaptive correction addresses the above-mentioned disadvantages of the list-based method. While the correc-
tion itself (this is which pixels are used to correct an identified defect) is the same, no static information from a list is
used, instead they are detected "on the fly".
To use reasonable thresholds, knowledge of the noise statistics of the sensor is used to detect the outliers. These
will be corrected also on the fly. Because this is a dynamic approach, it also works in binning/decimation modes
and would also detect new appearing defects.
Nevertheless, there are some disadvantages:
• It is non-deterministic
• Wrong positives can be detected, meaning non-defect pixels could be treated as defect
• If pixels are at the edge of the used thresholds, it could be corrected in one frame, but not in the next
On mvBlueFOX3 cameras, the adaptive correction is always used if:
• There is no list stored on the camera
• Binning or decimation is used
1.18.2.2 Optimizing the color/luminance fidelity of the camera
Purpose of this chapter is to optimize the color image of a camera, so that it looks as natural as possible on different
displays and for human vision.
This implies some linear and nonlinear operations (e.g. display color space or Gamma viewing LUT) which are
normally not necessary or recommended for machine vision algorithms. A standard monitor offers, for example,
several display modes like
sRGB , "Adobe RGB" , etc., which reproduce the very same color of a camera color
differently.
It should also be noted that users can choose for either
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