BOBCAT HD-SDI
Hardware User’s Manual
Imperx, Inc.
Rev. 1.4
6421 Congress Ave.
6/2/2014
Boca Raton, FL 33487
+1 (561) 989-0006
54 of 175
2.11.
WHITE BALANCE
2.11.1.
White Balance
The color representation in the image depends on the color temperature of the
light source. Bobcat has built in algorithm to compensate for this. When white
balance correction is enabled, the camera collects the luminance data for each
of the primary colors R, G and B, analyzes it, and adjusts the color setting in
order to preserve the original colors and make white objects to appear white.
The algorithm collects data from the entire image, and can work in six different
modes – “Off”, “Once”, “Auto” and “Manual”, “Indoor 3200K”, and “Outdoor
5600K”. When set to “Off” no color correction is performed. When set to
“Once” the camera analyzes only one image frame, calculates only one set
correction coefficients, and all subsequent frames are corrected with this set of
coefficients. When set to “Manual” the camera uses the correction coefficients
as entered from the user. In “Auto” mode the camera analyzes every frame, a
set of correction coefficients are derived for each frame and applied to the next
frame. All Bobcat color cameras support white balance feature.
2.12.
DYNAMIC BLACK LEVEL CORRECTION AND TAP BALANCING
2.12.1.
Black Level Correction
As was described in the Gain and Offset section, the reference black level on
each CCD output fluctuates around 0V. The AFE offset correction works on
the entire image and if there are noise fluctuations on a line level, the AFE is
not capable of correcting them. The camera has a built in dynamic signal-to-
noise correction feature to compensate for this effect. In the beginning of each
line the CCD has several black (masked) columns. The dark level for each tap
is sampled over several of these masked pixels and the average per tap black
level floor is calculated for each frame. The average floor level for each tap is
then subtracted from each incoming pixel (from the corresponding tap) from
the next frame.
2.12.2.
Tap Balancing
Since the camera has two separate video outputs coming out of the CCD, there
is always some offset misbalance between the video outputs. Thus, changing
the AFE gain leads to a change in the offset level and to a further misbalance
between the two video signals. To correct the balance between two signals at
any particular gain, BOBCAT series of cameras have static and dynamic
balancing algorithms implemented in the firmware. The algorithms compares
the black and bright levels of the adjacent pixels around the tap line, and
adjusts the gain and offset for each tap accordingly, until the balance has been
