Linlog - Photon Focus CameraLink MV1-D1312 series User Manual

4 Functionality
Black Level Adjustment
The black level is the average image value at no light intensity. It can be adjusted by the
software by changing the black level offset. Thus, the overall image gets brighter or darker.
Use a histogram to control the settings of the black level.
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4.2.2 LinLog

Overview
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The LinLog technology from Photonfocus allows a logarithmic compression of high light
intensities inside the pixel. In contrast to the classical non-integrating logarithmic pixel, the
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LinLog pixel is an integrating pixel with global shutter and the possibility to control the
transition between linear and logarithmic mode.
In situations involving high intrascene contrast, a compression of the upper grey level region
can be achieved with the LinLog
response. At high intensities the response changes to logarithmic compression (see Fig. 4.7).
The transition region between linear and logarithmic response can be smoothly adjusted by
software and is continuously differentiable and monotonic.
G r e y
V a l u e
1 0 0 %
0 %
Figure 4.7: Resulting LinLog2 response curve
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LinLog is controlled by up to 4 parameters (Time1, Time2, Value1 and Value2). Value1 and Value2
correspond to the LinLog
Value1 and Value2 respectively, the stronger the compression for the high light intensities. Time1
and Time2 are normalised to the exposure time. They can be set to a maximum value of 1000,
which corresponds to the exposure time.
Examples in the following sections illustrate the LinLog
LinLog1
In the simplest way the pixels are operated with a constant LinLog
knee point of the transition.This procedure has the drawback that the linear response curve
changes directly to a logarithmic curve leading to a poor grey resolution in the logarithmic
region (see Fig. 4.9).
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technology. At low intensities each pixel shows a linear
L i n e a r
R e s p o n s e
V a l u e 1
V a l u e 2
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voltage that is applied to the sensor. The higher the parameters
S a t u r a t i o n
W e a k c o m p r e s s i o n
R e s u l t i n g L i n l o g
R e s p o n s e
S t r o n g c o m p r e s s i o n
L i g h t I n t e n s i t y
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feature.
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voltage which defines the