
MCM20014
MOTOROLA
5
enables enhanced sensitivity in the entire visual spec-
tral range and a lag free operation.
The nominal photoresponse of the MCM20014 is shown
in
Figure 3
.
Figure 3. MCM20014 Nominal spectral response
In addition to the imaging pixels, there are additional
pixels called dark and dummy pixels at the periphery of
the imaging section (see
Figure 2
). The dark pixels are
covered by a light blocking shield rendering the pixels
underneath insensitive to photons. These pixels provide
the sensor means to measure the dark level offset
which is used downstream in the signal processing
chain to perform auto black level calibration. The dum-
my pixels are provided at the array
’
s periphery to elimi-
nate inexact measurements due to light piping into the
dark pixels adjacent to active pixels. The output of these
pixels should be discarded.
Electronic shuttering, also known as electronic expo-
sure timing in photographic terms, is a standard feature.
The pixel integration time can be widely varied from a
small fraction of a given frame readout time to the entire
frame time. This feature can be especially useful in sit-
uations such as imaging of fast moving objects where
maximum available integration time is long enough to
cause smear or blurring or when imaging a bright scene
where there are enough photons to cause an early sat-
uration of the pixel.
2.1.2 Color Separation and Fill Factor Enhancement
The MCM20014 family is offered with the option of
monolithic polymer color filter arrays (CFAs). The com-
bination of an extremely planarized process and propri-
atary color filter technology result in CFAs with superior
spectral and transmission properties. The standard op-
tion (Part # MCM20014IBBN) is a primary (RGB)
“
Bay-
er
”
pattern (see
Figure 4
), however, facility to produce
customized CFAs including complementary (CMYG)
mosaics also exists. Depending on the application, the
choice between primary or complementary filter mosa-
ics should be made. In general, primary mosaics are
used in still video while complementary are used in real
time video applications.
Applications requiring higher sensitivity can benefit from
the optional micro-lens arrays shown in
Figure 5
. The
lenslet arrays can improve the fill factor (aperture ratio)
of the sensor by 1.5-2x depending on the F number of
the main lens used in the camera system. Microlenses
yield greatest benefits when the main lens has a high F
number. As a caution, unoptimized F numbers can lead
to optical aberrations hence, care should be taken when