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Piranha4 8K Camera Color User's Manual
03-032-20156-00
Teledyne DALSA
4.
The sensor has 4K red and 4k blue alternating pixels. To create 8K red and 8k blue pixels, the blue
pixels located at the red position are determined by averaging the two adjacent blue pixels. The
same process is used for the red pixels. This is the only interpolation algorithm provided by the
camera.
5.
Color correction is available for those users that need to compensate for the spectral transmission
characteristics of the sensors color filters and the customers light source. This can be achieved by
imaging a MacBeth Chart© illuminated by the application‘s light source and processing the
image using a color correction demonstration tool provided as part of Teledyne DALSA‘s Sapera
Processing software. This tool will generate the desired color correction file that can be
downloaded to the camera.
Note:
Prior to imaging the MacBeth Chart©, the camera should have been calibrated with a white
reference in place of the MacBeth Chart© and color correction must be turned off. The calibration
process will ensure the camera output is uniform and white balanced.
6.
The introduction of offsets has limited value in color applications as it will cause color distortion.
However, the camera has the ability to add either a positive or negative offset as required by a
specific application. This offset can be useful when trying to measure dark noise where black
level clipping will cause an error in the result.
7.
A single overall system gain is applied equally to all three colors. It will therefore not cause color
distortion when changed.
8.
A factory setting for white LED color correction can be applied, if needed.
Calibration
The goal of calibration is to produce a uniform, white balanced and, if required, color corrected image at
the desired level out of the camera when it is imaging a uniform white object, using the optical setup of
the user‘s application.
The user should configure the camera to use the EXSYNC and exposure timing they desire plus adjust the
light level for normal operation. The lens should be at the desired magnification, aperture and be in focus.
As the white reference located at the object plane will be in focus, any features on its surface (e.g. dust,
scratches) will end up in the calibration profile of the camera. To avoid this, use a clean white plastic or
ceramic material, not paper. Ideally, the white object should move during the calibration process as the
averaging process of the camera will diminish the effects on any small variation in the white reference.
The user may wish to start the calibration process by evaluating the characteristics of their setup with no
calibration enabled. This can be readily achieved by disabling FPN, PRNU & color correction coefficients,
setting white balance red, green and blue gains to one, and the system gain to one.
Begin by adjusting the system gain until the peak intensity of the three colors is at the desired DN level.
You may want to use the white balance gains to adjust the peak of each color to be a similar DN value,
but this is not necessary. Before proceeding any further, it is desirable to complete an FPN calibration.
This is best performed using a lens cap to ensure no light gets into the camera
.
Once complete, a PRNU
calibration can be performed using a target value you want all the pixels to achieve. This target value can
be higher or lower than the peak values you observed while initially setting up the camera. Once PRNU
calibration is complete, it will take several seconds, all three colors should be at the target value, white
balance gains will have been adjusted to suit the cameras optimum setup for a balanced white output,
and the correction coefficient will be enabled. The system gain will remain as originally set. The
coefficient and gain parameters, timing and control configuration etc can be stored in any one of eight
