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Operation and Features
3.9 Image Enhancements
3.9.1 Shading Correction
In theory, when a digital camera captures an image of a uniform object, the pixel values output
from the camera should be uniform. In practice, however, variations in optics and lighting and
small variations in the sensor's performance can cause the camera output to be non-uniform even
when the camera is capturing images of a uniform object. L800
shading correction feature that allows the camera to correct the captured image for variations
caused by optics, lighting and sensor variations. There are two types of shading correction
available on L800
3.9.1.1 Guidelines When Using Shading Correction
When using the shading correction feature, make sure to take the following guidelines into
account:
• Any time you make a change to the optics or lighting or if you change the camera's gain set-
ting or exposure mode, you must generate a new set of PRNU shading values. Using out of
date PRNU shading values can result in poor image quality.
• When you generate the DSNU and PRNU shading values, correction values will be calcu-
lated for all of the pixels in the sensor regardless of how the AOI (see Section 3.7) parame-
ters are set. If you change the AOI settings, you do not need to generate new shading
values.
3.9.1.2 DSNU Shading Correction
In theory, when a line scan camera with a digital sensor captures a line in complete darkness, all
of the pixel values in the line should be near zero and they should be equal. In practice, slight
variations in the performance of the pixels in the sensor will cause some variation in the pixel
values output from the camera when the camera is capturing lines in darkness. This variation is
know as Dark Signal Non-uniformity (DSNU). The DSNU shading correction feature on L800
cameras can correct for the variations caused by DSNU.
Generating a Set of DSNU Shading Values
Before you can use DSNU shading correction, you must generate a set of DSNU shading
correction values. To generate a set of values, perform the following steps:
1. Cover the camera lens, close the iris in the camera lens, or darken the room so that the
camera will be capturing lines in complete darkness.
2. Begin capturing lines either by generating an ExSync signal to trigger line capture or by
setting the camera for free-run exposure.
3. Signal the camera to generate a set of DSNU shading values:
a) You can start the generation of a set of DSNU shading values with the Camera
Configuration Tool Plus (see Section 4.1). With the CCT+, you use the Shading Value
Generate parameter in the Image Enhancement parameters group to start the generation
of a set of DSNU shading values.
b) You can also start the generation of a set of DSNU shading values by using a binary write
command (see Section 4.3) to write a value to the Generate field of the Shading Value
Generate CSR (see page 4-39).
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cameras, DSNU shading correction and PRNU shading.
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cameras are equipped with a
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BASLER L800
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Troubleshooting
