Polaroid ProCam Repair Manual page 34

Energizing Solenoid 2 releases the Catch Pawl which swings down and engages
one of the teeth along the periphery of the Quintic lens (Figure 1-30). The moving
lens is thus halted at a point where, in combination with the taking lens and fixed
Quintic lens, it is in proper focus for the subject distance as measured by the
Transducer.
SOLENOID 2
Figure 1-30. Catch Pawl Holds Quintic in Place
With the lens system now focussed, Solenoid 1 is de-energized. Since the Catch
Pawl moved out of the way in the previous step, the Walking Beam is free to pivot
under spring action. This releases the Shutter Blades as in previous Polaroid
shutter systems. At the first instant of Shutter Blade release after Solenoid 1 is de-
energized (actually 20ms after it is deenergized), an opening created by the
position of the three Shutter Blades allows light from the Encoder LED to again
reach the Encoder photodiode (Figure 1-31). (The position of the Quintic lens in
its focussed or stopped setting is such that a "window" is lined up between the
Encoder LED and the photodiode). This light pulse is the First Light Detect and
serves as the starting point for all exposure measurements.
ENCODER
CIRCUIT
ENCODER LED
OPENING HERE AS SHUTTER
BLADES START TO OPEN
CATCH PAWL
ENCODER
PHOTODIODE
Figure 1-31. First Light Detect
1 - 28
MOVING QUINTIC
LENS STOPPED IN
PROPER FOCUS
QUINTIC LENS IN
FOCUSED POSITION