2-11
2. AW (Auto White balance) control
AW control compensates the Red component gain and Blue component gain shown in the camera block
diagram to keep the white balance in the camera picture under every kind of light source.
Basic input data for AW control are three of the following.
(1) R, G, B levels of sections divided a picture into 48 sections.
(2) Data on existence/absence of infrared rays in the light source. This data is used for judging the
sort of the light source.
(3) Illumination judged with the exposure compensation parameters (iris/ AGC gain/ shutter speed).
The white balance is controlled by the following setting referring to the R, G, B data on the section that is
judged as a white (uncolored) part of the picture according to the three kinds of data mentioned above.
Red component gain
=
Green level
/
Red level
Blue component gain
=
Green level
/
Blue level
Besides the white balance control, balance among color phases is controlled by the parameter control in
the color signal processing from RGB to C signal depending on the light source.
1) Light source judging process
IR FLICKER BRIGHT LIGHT
DC component AC component (Over 4000 Lx)
SOURCE
Yes Yes Yes HAROGEN
Yes Yes No
∗
Yes No Yes OUT DOOR
Yes No No OUT DOOR
No Yes Yes FL LIGHT
No Yes No FL LIGHT
No No Yes FL LIGHT
No No No FL LIGHT
∗
: OUT DOOR or HAROGEN (not FL LIGHT)
Table 2-3-1 Light source judging process
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