KAC-1310 データシートの表示（PDF） - Unspecified
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KAC-1310 Datasheet PDF : 76 Pages
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IMAGE SENSOR SOLUTIONS
IMAGE SENSOR SOLUTIONS
White Balance Control PGA (WB Gain)
[For the purposes of illustration, the following
discussion assumes a Bayer RGB color pattern;
with the appropriate correlation (as shown in
Figure 13), the CMY Bayer pattern may be
substituted throughout.]
The sensor produces three primary color outputs,
Red, Green, and Blue. These are monochrome
signals that represent luminance values in each of
the primary colors. When added in equal amounts
they mix to make neutral color. White balancing is
a technique where the gain coefficients of the
Green1, Red, Blue, and Green2 pixels comprising
the Bayer RGB pattern are set so as to equalize
their outputs for neutral gray color scenes. Since
the sensitivity of the two green pixels in the Bayer
pattern may not be equal, an individual color gain
register is provided for each component of the
Bayer pattern.
Once all color gain registers are loaded with the
desired gain coefficients, white balance is
achieved in real time and in analog space. The
appropriate values are selected and applied to the
pixel output via a high speed path, the delay of
which is much shorter than the pixel clock rate.
Real time updates can be performed to any of the
gain registers. However, latency associated with
the I2C interface should be taken into
consideration before changes occur. In most
applications, users will be able to assign
predefined settings such as daylight, fluorescent,
tungsten, and halogen to cover a wide gamut of
illumination conditions.
Both DPGA designs use switched capacitors to
minimize accumulated offset and improve
measurement accuracy and dynamic range. The
white balance gain registers are 6-bits and can be
programmed to allow gain of 0.695x to 2.74x in
varying steps depending on which gain mode is
selected (RAW or LIN mode).
The WB Gain Stage (PGA WB) is a two-segment
piecewise Linear gain stage. In Raw Mode this
stage produces smaller gain steps for the first half
of its gain range, and larger gain steps for second
half of its gain range. This allows fine adjustment
for color ratios as well as a large gain swing.
If the piecewise linear mode is difficult to manage
and the fine steps are not required, this gain stage
can be placed into Lin1 Mode. In this mode every
other gain step is skipped for the first 1/3 of the
gain range. This produces the same gain range
but with uniform gain steps throughout the range.
C / G1 (0) 6
Y1 / R (1) 6
Y2 / B (2) 6
M / G2 (3) 6
6
DPGA
0.7x- 2.7x
G1(0) R(1)
B(2) G2(3)
C(0) Y 1(1)
Y 2(2) M(3)
Figure 13: Color Gain Register Selection
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KAC-1310 Rev 4 • www.kodak.com/go/imagers 585-722-4385 Email: imagers@kodak.com
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