control function also provides the power for the operation of the
Q/switch and monitors the temperature of the laser cavity.
The Q/switch is the piece of the optics that releases the laser beam. It
releases the beam from the LD/R at the time required to produce optimum
output energy. The Q/switch requires a high voltage level to operate.
The 450 V power supply and the Q/switch trigger circuit located in the
energy control card A2A1A6 generate the Q/S TRIGGER signal to operate the
The 450 V power supply provides the 450 V to the Q/switch
trigger circuit. When the microprocessor, U9 of the control logic card
A1A2, issues the Q/S TRIG signal, the Q/switch trigger circuit discharges
the 450 V as Q/S TRIGGER and sends it to the Q/switch. The Q/S TRIGGER
signal causes the Q/switch to open and allows the laser beam to escape
from the laser cavity.
When the laser fires, the energy sense diode in the energy control card
receives a sample of the laser output. This energy sense diode generates
the signal ENERGY DIODE. The signal goes to the A trig gate, the energy
comparator, and the sample and hold circuit via an integrator.
hybrid unit U2 located in the energy control card contains these
The A TRIG gating circuit generates the A TRIG signal when it receives
the ENERGY DIODE signal. The A TRIG signal goes to the range counter U16
in the control logic card A1A2 to start the counter. The A trig gate
also produces a 2-microsecond signal to control sampling time in the
sample and hold circuit.
The sample and hold circuit receives the integrated pulse from the energy
sense diode via the integrator. It samples this signal while the A trig
gating signal is also present. The sample and hold circuit produces the
ENERGY ERROR signal. The ENERGY ERROR signal provides feedback to the
PFN power supply in the power supply card A1Al. This allows the PFN to
adjust the intensity of the flash from the flashlamp. The laser output
is proportional to the intensity of the light produced by the flashlamp.
The intensity of the flashlamp, in turn, is proportional to the PFN
voltage. The ENERGY ERROR signal is a step-waveform with a range of +14
V to -14 V, with 1 V step increments.
The energy comparator receives the ENERGY DIODE pulse and compares its
signal strength with a preset level. The comparator generates the ENERGY
VALID signal when the sampled laser output exceeds the preset level.
This signal indicates to the microprocessor that the laser output is
If the laser output is below the comparator level, the
the LASER FAIL (red) light in the LD/R eyepiece display to light.