Photon Focus DR1-D1312(IE)-G2, User Manual

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4.2 Pixel Response
4.2.1 Linear Response
The camera offers a linear response between input light signal and output grey level. This can
be modified by the use of LinLog
®
as described in the following sections. In addition, a linear
digital gain may be applied, as follows. Please see Table 3.2 for more model-dependent
information.
Black Level Adjustment
The black level is the average image value at no light intensity. It can be adjusted by the
software. Thus, the overall image gets brighter or darker. Use a histogram to control the
settings of the black level.
In CameraLink
®
cameras the black level is called "BlackLevelOffset" and in GigE
cameras "BlackLevel".
4.2.2 LinLog
®
Overview
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
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
®
technology. At low intensities each pixel shows a linear
response. At high intensities the response changes to logarithmic compression (see Fig. 4.10).
The transition region between linear and logarithmic response can be smoothly adjusted by
software and is continuously differentiable and monotonic.
LinLog
®
is controlled by up to 4 parameters (
Time1
,
Time2
,
Value1
and
Value2
).
Value1
and
Value2
correspond to the LinLog
®
voltage that is applied to the sensor. The higher the parameters
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
®
feature.
LinLog1
In the simplest way the pixels are operated with a constant LinLog
®
voltage which defines the
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. 4.12).
.
4.2 Pixel Response 39