User`s manual

Operation and Features
Basler L304kc 3-43
Draft
Enabling DSNU Shading Correction
Once you have a complete set of DSNU shading values in place, you can enable and use DSNU
shading correction. With the DSNU correction feature enabled, the camera will use the DSNU
shading values to apply the appropriate offset to each pixel to correct for DSNU.
You can enable DSNU shading correction with the Camera Configuration Tool Plus (CCT+) or by
using binary read/write commands from within your own application to set the camera’s control
and status registers (CSRs).
With the CCT+
With the CCT+ (see Section 4.1), you use the Shading Mode parameter in the Image
Enhancement parameters group to enable DSNU shading correction.
By Setting CSRs
You enable DSNU shading correction by writing a value to the Mode field of the Shading Mode
CSR (see page 4-32).
See Section 4.2.2 for an explanation of CSRs and Section 4.3.1 for an explanation of using read/
write commands.
3.10.1.3 PRNU Shading Correction
In theory, when a line scan camera with a digital sensor captures lines with the camera viewing a
uniform, light-colored target in bright light, all of the pixel values in the captured lines should be
near their maximum gray value and they should be equal. In practice, slight variations in the
performance of the pixels in the sensor, variations in the optics and variations in the lighting will
cause some variation the pixel values output from the camera. This variation is know as Photo
Response Non-uniformity (PRNU). The PRNU shading correction feature on L304
kc cameras can
correct for the variations caused by PRNU.
Generating a Set of PRNU Shading Values
Before you can use PRNU shading correction, you must generate a set of PRNU shading
correction values. To generate a set of values, perform the following steps:
1. Place a uniform white target in the field of view of the camera. Adjust your lighting, optics, line
rate, exposure mode, exposure time, gain and camera temperature as you would for normal
system operation.
2. Perform several capture cycles and examine the pixel values returned from the camera. The
pixel values for the brightest pixels in each line should be about 90 to 95% of maximum.
a) If the pixel values for the brightest pixels are at 90 to 95% of maximum, go on to step 3.
b) If the pixel values for the brightest pixels are not at 90 to 95% of maximum adjust your
lighting and/or lens aperture setting to achieve 90 to 95%.
c) If you can not achieve 90 to 95% output by adjusting the lighting and/or aperture, then
adjust the gain settings to achieve the correct output.
3. Perform several capture cycles and examine the pixel values in each line. In each line, the
values for the darkest pixels must not be less 1/2 of the values for the lightest pixels in the
line. (If the values for the darkest pixels are less than 1/2 of the value for the lightest pixels,
the camera will not be able to fully correct for shading variations.)
a) If the values for the darkest pixels are not less than 1/2 of the value for the lightest pixels,
go on to step 4.
b) If the values for the darkest pixels are less than 1/2 of the value for the lightest pixels, it
usually indicates extreme variations in lighting or poor quality optics. Make corrections as
required.