
12 Pixel Data Processing
12.2
Image Correction
12.2.1
Overview
The camera possesses image pre-processing features, that compensate for non-uniformities
caused by the sensor, the lens or the illumination. This method of improving the image quality
is generally known as ’Shading Correction’ or ’Flat Field Correction’ and consists of a
combination of offset correction, gain correction and pixel interpolation.
Since the correction is performed in hardware, there is no performance limita-
tion of the cameras for high frame rates.
The offset correction subtracts a positive or negative calibration value from the live image and
thus reduces the fixed pattern noise of the image sensor. In addition, defect pixels can be
removed by interpolation. The gain correction can be used to flatten uneven illumination or to
compensate shading effects of a lens. Both offset and gain correction work on a pixel-per-pixel
basis, i.e. every pixel is corrected separately.
The camera is calibrated in the factory with the default camera settings. If the camera is
operated with an exposure time that differs greatly from the factory defaults then it makes
sense to recalibrate the FPN correction of the camera. The calibration of the FPN correction
requires the following steps:
1.
Obtain a black reference image (
Correction_SetBlackRef
) (see Section 12.2.2).
2.
Obtain a grey reference image (
Correction_SetGreyRef
) (see Section 12.2.3).
3.
Enable
Correction_AutoThreshold
or set the correction thresholds manually (see Section
4.
Let the camera calculate the calibration values by sending the command
Correction_Calculate
. The new calibration values are now active in the camera.
5.
It is recommended to test the calibration values by examining images grabbed with the
FPN correction enabled (e.g. setting
Correction_Mode
to
OffsetGainHotpixel
).
6.
The reference images and the calibration values are now stored in the camera’s volatile
memory (RAM), i.e. the new calibration is lost if the camera power is switched off. To
store the calibration values permanently, send the command
Correction_SaveToFlash
.
Note, that this overwrites the factory calibration. i.e. the calibration performed at the
production of the camera.
Do not set any reference images when gain or LUT is enabled! Read the follow-
ing sections very carefully.
There are two independent calibration sets that are activated by the setting
of
Sensor_PixelFormat
(
Mono10
/
Mono12
). All operations regarding the image cor-
rection calibration affect only the calibration set of the current setting of
Sen-
sor_PixelFormat
. This also applies to the command
Correction_SaveToFlash
which
only stores (overwrites in flash memory) the calibration data for the current set-
ting of
Sensor_PixelFormat
. Example: if
Sensor_PixelFormat
is set to
Mono10
and
the image correction is calibrated as described above, then the calibration of the
Mono12
setting is not modified. To calibrate the camera also for
Mono12
, set
Sen-
sor_PixelFormat
to
Mono12
and do the calibration again.
68 of 143
MAN093 08/2021 V1.1
Содержание MV4 Series
Страница 8: ...CONTENTS 8 of 143 MAN093 08 2021 V1 1 ...
Страница 12: ...1 Preface 12 of 143 MAN093 08 2021 V1 1 ...
Страница 16: ...3 Product Specification Figure 3 1 Photonfocus MV4 UV 10 GigE GT camera series 16 of 143 MAN093 08 2021 V1 1 ...
Страница 40: ...4 Image Acquisition 40 of 143 MAN093 08 2021 V1 1 ...
Страница 42: ...5 Exposure Control 42 of 143 MAN093 08 2021 V1 1 ...
Страница 52: ...6 Counter Timer 52 of 143 MAN093 08 2021 V1 1 ...
Страница 64: ...10 Image Format Control 64 of 143 MAN093 08 2021 V1 1 ...
Страница 66: ...11 Frame Rate 66 of 143 MAN093 08 2021 V1 1 ...
Страница 82: ...12 Pixel Data Processing 82 of 143 MAN093 08 2021 V1 1 ...
Страница 92: ...12 Pixel Data Processing 92 of 143 MAN093 08 2021 V1 1 ...
Страница 96: ...13 Precautions 96 of 143 MAN093 08 2021 V1 1 ...
Страница 120: ...16 Troubleshooting 120 of 143 MAN093 08 2021 V1 1 ...
Страница 126: ...19 Support and Repair 126 of 143 MAN093 08 2021 V1 1 ...
Страница 128: ...20 References 128 of 143 MAN093 08 2021 V1 1 ...
Страница 132: ...A Pinouts 132 of 143 MAN093 08 2021 V1 1 ...