TM 9-2350-277-10
OPERATE AN/VAS-5 DRIVER'S VISION ENHANCER (DVE) (M58 ONLY) -- Continued
0035 02
WARNING
The AUTO LEVEL and AUTO GAIN modes do not react instantly to rapidly changing scenery
(shade to sun, sun to shade). The AUTO LEVEL and AUTO GAIN modes require one or two
seconds to compensate. The automatic gain and level features will adjust faster than manual
adjustments. If necessary, slow or stop vehicle.
a.
AUTO GAIN -- The AUTO GAIN position provides the best image for driving conditions. For AUTO GAIN
mode, the control must be in the full counterclockwise detent position. In the AUTO position, the sensor video gain
is adjusted automatically. In this position, the internal circuitry examines the INFERRED video scene, determines
the hottest and coldest extremes, and adjusts the video gain accordingly. The AUTO GAIN mode should normally
be used while driving the vehicle.
b.
Manual GAIN adjustment -- When the vehicle is stationary, in some viewing conditions it may be helpful to adjust
the SENSOR GAIN control. Rotate the SENSOR GAIN control clockwise out of detent position. Choose a scene
within DVEs FIELD OF VIEW (FOV). Adjust the SENSOR GAIN control until objects and background features
range from near black to near white. At some settings it may be helpful to also make a slight readjustment of the
SENSOR LEVEL control. The optimum gain setting varies with the scene and background. The manual operation
should be used only when the vehicle is stationary. It may be useful for viewing imagery having very high thermal
difference scenes, such as nearby vehicles, factories, or fires. It is also useful for viewing low thermal difference
scenes, such as featureless desert terrains or wet fields during or after a rain, where increased gain (using manual
operation) may enhance detail resolution.
NOTE
The POLARITY switch is non-functional on the commander's display.
NOTE
There are two short periods each day called crossover periods or diurnal cycle when most
natural objects are about the same temperature. This is when they have cooled down at night
and as they are heating up in the early morning. Since objects are near the same temperature,
there is little temperature difference for the DVE to use, degrading the image display quality.
This is also what happens when a heavy rain makes all natural objects close to the same
temperature.
8.
POLARITY switch -- The scene polarity preference is selected by using the POLARITY switch. With the switch in
WHT-HOT (up position), hot objects in the scene appear lighter on a darker background. With the switch in BLK-HOT
(down position), hot objects in the scene appear darker on a lighter background. A small rectangle in the lower left
corner of the display indicates the switch position. A dark rectangle indicates the BLK-HOT switch position; a white
rectangle indicates the WHT-HOT switch position.
NOTE
Drive ONLY in the straight-ahead and level 0 degree detent viewing positions.
9.
Azimuth movement -- Full azimuth FIELD OF REGARD (FOR) is achieved by unlocking the Head Mirror and then
moving the azimuth control left or right 180 degrees from the straight-ahead position. Releasing the Azimuth Lock
control and moving the azimuth to the center position, the Head Mirror will automatically lock into the 0 degree
straight-ahead position. Sensor rotates as part of the hatch swivel plate.
0035 02-6
Change 4