9
side of the AC power input to the dome. This is the "zero
phase delay" position. The phase delay between the AC
line zero crossing and camera vertical sync can range to
360 degrees, with respect to the original "zero phase"
position. The 360 degree range is divided into 362 steps
for NTSC cameras and 370 steps for PAL cameras, so
that very fine adjustment of the phase delay is possible.
Increase Phase Delay: Issuing this command increases
the line-lock phase delay by one step. (AUX 41 - On.)
Decrease Phase Delay: Issuing this command
decreases the line-lock phase delay by one step. The
phase delay commands have no effect when the camera
is in the internal crystal sync mode. (AUX 41 - Off.)
Sync Mode Selection (AUX 42)
Line-Lock Mode On: Issuing this command puts the
camera into the line-lock sync mode. The phase delay
will be at the most recently set position. (AUX 42 - On.)
Internal Crystal Mode On: Issuing this command puts
the camera into the internal crystal sync mode. In this
mode, the camera's vertical sync has no fixed
relationship to the AC power line. The vertical rate is
59.94 Hz for NTSC cameras and 50 Hz for PAL
cameras. (In line-lock mode, the vertical rate is 60 Hz
for NTSC cameras and 50 Hz for PAL cameras.) (AUX
42 - Off.)
AGC Mode Selection (AUX 43)
The camera includes an AGC circuit that automatically
increases camera sensitivity at low levels of illumination.
AGC On: Issuing this command turns the camera AGC
on. The AGC operates with its maximum range of 30 dB.
(AUX 43 - On.)
AGC Off: Issuing this command turns the camera AGC
off. The AGC operates with a fixed gain of 5 dB, resulting
in a loss of camera sensitivity, but improving the signal-
to-noise ratio. (AUX 43 - Off.)
Backlight Compensation (AUX 20)
Normally, the camera AGC averages the contents of the
entire field-of-view to determine the best AGC operating
point. If the field-of-view contains large brightly lit
background areas and a small dimly lit foreground
object, the camera AGC may select an operating point
that does not allow for adequate viewing of the
foreground object. The AutoDome series cameras have
a fixed zone backlight compensation mode to alleviate
this problem. With backlight compensation turned on, the
camera determines its AGC operating point by averaging
over a subset of the entire field-of-view, as shown in the
figure below. (Camera AGC must be ON for the
backlight compensation to function.) If the object of
interest falls inside this zone, its visibility will remain
relatively constant even if the background illumination
varies. To achieve the best picture quality, under most
lighting conditions, turn off the backlight compensation.
Use this mode only to specifically compensate for a
backlit condition.
Backlight Compensation Off: Issuing this command
disables the camera's backlight compensation mode.
(AUX 20 - Off.)
S929A64BE
Backlit Condition
Backlight Compensation OFF
Backlight Compensation On: Issuing this command
enables the camera's backlight compensation mode.
(AUX 20 - On.)
S929A66AE
Backlit Condition
Backlight Compensation ON
S929A65AE
line 80
line 200
Zone of AGC Operation
With Backlight Compensation ON
Highlight (AUX 21)
Highlight On: Issuing this command turns on the
highlight mode. This mode is an alternative method for
compensating a field-of-view that contains a brightly lit
background and a dimly lit foreground object. With
highlight mode turned on, a fixed center zone will appear
on the screen having a gain of approximately 10 dB
higher than the operating point determined by the AGC.
The camera continues to average the contents of the
entire field-of-view to determine the best operating point.
The advantage of using this mode is that the area
surrounding the lit object will not white-wash. Only
objects in the center zone will be amplified. This mode
could also help target the backlight compensation zone
