Light Emitting Diode Array.
The LED array (Figure 2-20) converts video drive signals to visible
light.
The LED array consists of one multi-element LED array with
integral individual current-normalizing series resistors.
The video
drive signals from the video postamplifier control drivers are
applied to the current-normalizing series resistors, which are
connected to the LEDs and generate normalized current signals in each
LED. The visible light emitted by the LED array varies directly with
the input drive signals.
The LED array contains 180 elements of
gallium arsenide phosphide (GaAsP) diodes arranged in a format
matching the IR detector array with only the center 60 elements used
for video display.
LEDs located outside of the video display
illuminate the boresight diode at the center of scan mirror travel in
order to produce a boresight pulse. Operating current for the three
boresight elements is provided by the DC-DC converter.
The LEDs,
when forward-biased, emit visible red light at a wavelength of 6,600
Angstrom units (A). When the LED array is scanned by the back of the
scan mirror, a visible scene is formed corresponding to the IR scene
scanned simultaneously by the front of the scan mirror.
Scene
brightness depends on the BRT and CRT control settings.
Figure 2-20.
Light Emitting Diode Array.
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MM4812
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