HD49815TF Datasheet, PDF (16/25 Pages) Hitachi Semiconductor – Digital Camera Signal Processor

HD49815TF
e. C gamma (γ) correction block
The C gamma correction circuit performs gamma processing on the RGB signal. It is set in State
Data SP_A3 [6 to 9]. Four kinds of values can be set independently, according to the input-signal
level, to acquire optimal gamma characteristics: the C gamma dark (to reduce the gain of the small
signals for improving S/N), C gamma coefficient (to control the expansion of the gamma curve), C
gamma knee (to decide the slope of the large signals), and C gamma limit (to perform high-clipping
processing for the input signal of the C gamma circuit).
f. YL matrix block
The luminance level changes according to the color temperature of the imaged object. Set State
Data SP_A5 [12, 13] for the luminance correction. To correct the luminance, create YL from the
three primary colors (R, G, and B) and convert it to the luminance signal level. The YL matrix
circuit creates the YL level from the RGB signal.
The YL matrix is set in State Data SP_A3 [11 to 13].
g. The axis-conversion (C-Y matrix) block
The C-Y (color-difference) matrix takes R-G and B-G as its input signals, and creates the R-Y and
B-Y color-difference signals by setting coefficients for those inputs.
The axis-conversion (C-Y matrix) circuits are set in State Data SP_A8 [0 to 5].
h. Base-clipping block
Since base clipping is performed on the color-difference signals, the base-clipping circuit has the
characteristics of clipping the sections near axes on a vector scope.
This circuit is set in State Data SP_A8 [8].
3. Luminance-signal-processing block
from
YL matrix
From
the input
line
memory
block
H.V Luminance
enhancer correction
+
Gamma
correc-
tion
Highlight
enhancer
Y Setup
To
the AWB-
detection block
Fade +
To
the zoom
function
7.5IRE
Figure 5 Luminance-Signal-Processing Block
a. H-enhancer function
The H-enhancer circuit allows the core level, the enhancer gain, and the noise coefficient to be set
independently to acquire optimal characteristics.
This circuit is set in State Data SP_A4 [4 to 7].
b. V-enhancer function
The V-enhancer circuit allows the enhancer coefficient to be set and can control the gain for only
those signal components that exceed the set core level.
This circuit is set in State Data SP_A4 [8 to 10].
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