1.18 Use Cases
105
1.18.2.1.2
Defect pixel detection using mvIMPACT Acquire
As mentioned, the defect pixel list can be gener-
ated using mvIMPACT Acquire. Since there are three types of defects, mvIMPACT Acquire offers three calibration
methods for detection:
1.
leaky pixel
(in the dark)
which indicates pixels that produce a higher read out code than the average
2.
hot pixel
(in standard light conditions)
which indicates pixels that produce a higher non-proportional read out code when temperatures are rising
3.
cold pixel
(in standard light conditions)
which indicates pixels that produce a lower read out code than average when the sensor is exposed (e.g.
caused by dust particles on the sensor)
Note
Please use either an Mono or RAW Bayer image format when detecting defective pixel data in the image.
1.18.2.1.2.1
Detecting leaky pixels
To detect leaky pixels the following steps are necessary:
1. Set
gain
(
"Setting -
>
Base -
>
Camera -
>
GenICam -
>
Analog Control -
>
Gain = 0 dB"
)
and
exposure
time
"Setting -
>
Base -
>
Camera -
>
GenICam -
>
Acquisition Control -
>
ExposureTime = 360 msec"
to the given operating conditions
The total number of defective pixels found in the array depend on the gain and the exposure time.
2. Black out the lens completely
3. Set the (Filter-)
"Mode = Calibrate leaky pixel"
4. Acquire an image (e.g. by pressing
Acquire
in wxPropView with
"Acquisition Mode = Single
←
-
Frame"
)
The filter checks:
Pixel > LeakyPixelDeviation_ADCLimit // (default value: 50)
All pixels above this value are considered as leaky pixel.
1.18.2.1.2.2
Detecting hot or cold pixels
Note
With "Mode = Calibrate Hot And Cold Pixel" you can execute both detections at the same time.
To detect hot or cold pixels the following steps are necessary:
1. You will need a uniform sensor illumination approx. 50 - 70 % saturation (which means an average gray value
between 128 and 180)
2. Set the (Filter-)
"Mode = Calibrate Hot Pixel"
or
"Mode = Calibrate Cold Pixel"
or
"Mode = Calibrate Hot And Cold Pixel"
3. Acquire an image (e.g. by pressing
Acquire
in wxPropView with
"Acquisition Mode = Single
←
-
Frame"
)
MATRIX VISION GmbH
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