The hybrid generates the A TRIG, ENERGY ERROR, and ENERGY VALID signals
each time the laser fires, once for RNG mode and repetitively for DES
mode.
The energy control function also monitors the temperature within the
transceiver. The overtemp comparator monitors the signals from the two
thermistors in the transmitter, RT1 and RT2. RT1 senses the temperature
within the laser cavity and produces the signal CAVITY THERMISTOR. RT2
senses the temperature outside the heat exchanger and produces the signal
EXHAUST THERMISTOR.
An overtemperature condition exists when the
temperature of the laser cavity exceeds the temperature of the exhaust by
a preset level. If an overtemperature occurs, the overtemp comparator
generates the signal OVERTEMP to the microprocessor.
When the
microprocessor receives OVERTEMP, it causes the LASER FAIL (red) light in
the LD/R eyepiece display to blink.
d. Receiver Function (figure FO-21 of appendix B).
The receiver
function receives the reflected laser pulse from the target to determine
its range. It determines the range of the target from either the first
or last reflected pulse received, depending on the mode selected.
When the LD/R fires in the rangefinding mode, the microprocessor U9 in
the control logic card A1A2 generates RCVR START. This signal activates
the receiver high voltage drive circuitry in the receiver card A2A4 and
resets the range counter U16 in the control logic card.
The A TRIG
signal generated from energy control A2A1A6 starts the range counter
counting. The range counter monitors the RNG1/RNG2 signal sent from the
MODE switch A1W2S2 to determine whether to stop counting at the first or
last pulse received. In the RNG1 mode, the range counter determines the
range of the first received reflected pulse.
In the RNG2 mode, it
determines the range of the last reflected pulse received.
The microprocessor also produces the Q/S TRIG-RCVR signal, which goes to
the receiver card to activate the threshold logic. This threshold offset
circuitry reduces the noise level of the receiver during the ranging
interval. When the light detecting diode of the video detector receives
the reflected laser pulse, the video amplifier produces the VIDEO signal.
A VIDEO signal generates for each laser pulse received and goes to the
range counter. Depending on the mode selected, the VIDEO signal stops
the range count on the first or last pulse received.
When the range counter has stopped counting, the range data goes to the
microprocessor via the input/output (I/O) expander U10.
The
microprocessor combines the range data with the azimuth and elevation
data. The microprocessor then sends the AZ, EL, and
24
OD1721
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