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expo-nential, or logarithmic, behavior
of the human eye. HDR is helpful
in traffic applications for subduing
glaring reflections when reading
license plates or countering the over
exposure effects of bright headlights.
The desired logarithmic response in a
CMOS sensor can be achieved on-chip
in several different ways:
● by sequential image capture using
widely varying exposure times,
thereby recording the light and dark
areas separately,
● by equipping the sensor's odd and
even rows with different sensitivi-
ties for light and dark and calculating
an appropriate average value for all
regions of the image (Figure 6), or
● by using a piece-wise linear
response (PLR), which delivers a more
logarithmic ramping of the sensor's
response curve (Figure 7).
The user can choose the best suited
method depending on the applica-
tion, as they all have their specific
benefits and drawbacks.
Enhanced NIR Sensitivity
Extending the spectral range of CMOS
sensors to the near-infrared realm is
becoming more and more important
as a market trend (Figure 8). This
especially applies to traffic applications
but also to machine vision, because it
allows the illumination of the scene to
be monitored with flash lights that are
invisible to the human eye.
Pieter Willems is Manager
Standard Products at CMOSIS in
Antwerp, Belgium.
Figure 8: Enhanced sensor sensitivity in the near infrared, as
demonstrated in the CMV family of CMOSIS.
Figure 9: The CMV Series sensors of CMOSIS were developed for
machine-vision applications.
Table 1: Key specifications of the CMV Series.
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