2 0 H a M e s i l a S t . , N e s h e r 3 6 8 8 5 2 0 , I s r a e l
P O B 2 5 0 0 4 , H a i f a 3 1 2 5 0 0 1 , I s r a e l
T e l : ( + 9 7 2 ) - 7 2 - 2 7 2 3 5 0 0 F a x : ( + 9 7 2 ) - 7 2 - 2 7 2 3 5 1 1
Page no. 33 | Configuration Interface
Where P(x,y) is the pixel at offset X in horizontal and Y in vertical. Pdark is the offset of the vertical of the specific
row/column that was measured during the calibration stage. Gain is the gain of the specific row/column that was
measured during the calibration stage.
7.7.3.1
Dark field calibration process
The dark field correction is the easiest one to calibrate. It only requires a reference image to be recorded without
illumination on the image sensor.
Follow these steps to perform dark field calibration process:
1.
For this calibration, the light should be blocked from the sensor. This can be achieved by removing the
lens and covering the sensor with a solid cap or closing the lens with a cap
2.
Set the “Field Calibration Mode” to “Dark” (1)
3.
Start camera’s stream either in free run or by applying an external trigger
4.
Initiate the selected calibration with “Field Calibration Start” command Execute (2)
5.
Stop camera’s stream
6.
Enable the Dark filed correction (3)
7.
Start camera’s stream either in free run or by applying an external trigger
7.7.3.2
Flat field calibration process
The choice of which light intensity to use for the bright field calibration requires a little bit more thought. If you
perform the calibration with a light intensity too close to camera saturation you might compensate the camera
too much and actually introduce more PRNU for low light intensities. If you use a weak light intensity, the
differences in photo response might be too small and you under-compensate the sensor. In general a light intensity
that gives a signal somewhere around 40% of the sensor full scale should give the optimal result. Follow these
steps to perform flat field calibration process:
1.
Prepare light source. Uniform light should be applied across the sensor. This can be achieved by removing
the lens and setting a uniform light source, such as diffused light or integrating sphere, in front of the
camera
2.
Set the “Field Calibration Mode” to “Flat” (1)
3.
Start camera’s stream either in free run or by applying an external trigger
4.
Initiate the selected calibration with “Field Calibration Start” command Execute (2)
5.
Stop camera’s stream
6.
Enable the Flat filed correction (3)
7.
Start camera’s stream either in free run or by applying an external trigger
NOTES:
1.
The Flat field calibration should be performed after the Dark field calibration has already be performed for the
selected camera settings.
2.
To summarize, depending on the flat field correction variant, reference images have to be recorded in dark and in a
bright field. Make sure the sensor is really dark when performing a dark field calibration and performing a bright field
calibration in a light intensity range around 40% of the sensor full scale.
3.
Errors might show up when a sudden peak in intensity is present in the reference scene as the correction is a low
frequency correction.
