Allied Guppy, Техническое руководство, Страница: 74 / 238

Description of the data path
GUPPY Technical Manual V4.0.1
74
One-push automatic white balance
It is activated by setting the one-push bit in the WHITE_BALANCE register
(see Chapter Status and control register for feature on page 181). The camera
automatically generates frames, based on the current settings of all registers
(GAIN, OFFSET, SHUTTER, etc.).
For white balance, in total eight frames are processed and a grid of at least
65536 samples is equally spread over the whole image area. The R-G-B com-
ponent values of the samples are added and are used as actual values for both
the one-push and the automatic white balance.
This feature uses the assumption that the R-G-B component sums of the sam-
ples are equal; i.e., it assumes that the average of the sampled grid pixels is
to be monochrome.
If the image capture is active (e.g. IsoEnable set in register 614h), the
frames used by the camera for white balance are also output on the 1394 bus.
Any previously active image capture is restarted after the completion of
white balance.
Automatic white balance can also be enabled by using an external trigger.
However, if there is a pause of >10 seconds between capturing individual
frames this process is aborted.
The following flow diagram illustrates the automatic white balance sequence.
Note
L
The following ancillary conditions should be observed for suc-
cessful white balance:
• There are no stringent or special requirements on the
image content, it requires only the presence of mono-
chrome pixels in the image.
• Automatic white balance can be started both during
active image capture and when the camera is in idle
state.