TM 11-6720-239-35
is a real, fixed image. The image striking the
rangefinder lens is movable and is shifted from
left to right to coincide with a portion of the fixed.
a. Shutter Circuit. Prior to taking a picture, the
image projected on the eye lens. The movable
operator must first set the FILM SPEED dial of
image is shifted by the focusing mechanism. This
the aperture wheel and lighting selector control.
is accomplished by turning the turret assembly,
This action closes certain contacts of light selector
upon which the movable image lens is mounted,
switch S5, located on the aperture wheel. The
through a small radius of arc so that the image
contact selected is determined by the position of
striking the mirror is shifted to the left or right.
the aperture wheel, which in turn is a function of
As the range finder is focused, the following
the combined operation of the aperture wheel and
actions take place:
lighting selector control. The closed contacts of S3
(1) The image passing through the rangefin-
connect one of the four RC timing circuits (C1
der lens is inverted by the movable image lens and
through C4 and R4 through R8) in series with
strikes the mirror.
photocell V1. When the shutter is cocked battery
(2) The inverted movable image striking the
B1 is not connected. Depressing the shutter re-
mirror is reversed by the mirror and projected
lease button causes the shutter release tip to close
through the small opening in the movable image
battery switch S1, applying battery B1 power to
aperture plate to the amber colored center of the
the magnet L1 hold and capacitor bypass circuits.
magnifying frame.
In the magnet hold circuit, current flows from the
(3) The movable image passing through the
positive (+) side of the battery, through battery
center of the magnifying frame is again inverted,
switch S1 to one side of the coil of electromagnet
but not reversed, and projected onto the beam
L1, and through variable resistor R1 to the base
splitter.
of transistor Q2. As soon as the current at the
(4) The image striking the beam splitter is
base of Q2 is high enough to trigger Q2, current
reversed, resulting in a real image, and projected
flows through the coil of electromagnet L1, the
onto the eye lens. The movable image, projected
collector and emitter of Q2, and potentiometer R3
onto the eye lens is smaller than the fixed image
to the negative (-) side of the battery. The ener-
derived through the objective lens. The fixed
gized electromagnet holds the closing blade in its
image occupies the entire eye lens area. The mov-
open position. In the capacitor bypass circuit, cur-
able image occupies a small amber square super-
rent flows from the positive side of the battery,
imposed on the center of the fixed image.
through battery switch S1, photocell V1, resistor
R6 and timing switch S2, to the negative side of
b. Viewfinder. The fixed image formed on the
the battery. Timing switch S2 bypasses the timing
eye lens through the action of the objective lens
capacitors (C1 through C4) and resistors (R4,
and beam splitter, is also the viewfinder image.
R5, R7, R8). Shortly after closing battery switch
The Albator line, dotted amber line framing the
S1, the shutter release tip trips the slide latch
fixed image, is formed by light passing through
releasing the opening blade and opening timing
the sliding mask assembly. The sliding mask as-
switch S2. The film is now being exposed to light,
sembly is comprised of two movable masks which
and the timing circuit is brought into operation.
are linked together. As the camera is focused
Opening timing switch S2 breaks the capacitor
from infinity to 3 feet, the Albator line con-
bypass circuit and the battery current is applied
tracts, to compensate for the reduced image size,
to timing capacitor C1, and through the applicable
and moves down and to the left to compensate for
contacts of light selector switch S5 to the pre-
parallex. As the camera is focused, the following
viously selected combination of timing capacitors
actions take place in the viewfinder.
(C2, C3, C4) and resistors (R4, R5, R7, R8). Cur-
(1) Light passes through the frosted glass
rent now flows from the positive side of the bat-
and sliding mask assembly to form the Albator
tery through battery switch S1, photocell V1, and
image.
the selected timing capacitors or capacitor/resis-
(2) The Albator image is projected to the
tor combinations to the negative side of the bat-
edge of the movable image aperture plate and re-
tery. The selected capacitors now begin to charge
flected through the outer edge of the amber col-
ored magnifying frame.
at a rate determined by photocell V1. The photo-
cell acts as a variable resistor which is controlled
(3) After passing through the magnifying
frame, the Albator image is reflected off the beam
by the light shining on it. If the light shining on
splitter onto the eye lens.
the photocell is bright, its resistance will be lower,
1-5
