secondary mirror assembly, and front surface mirror assembly
are contained. The hinged door is secured by means of two cap-
tive screws. A hinged light shield is located just inside the access
door and secured by one captive screw. A carrying handle is
located on the top of the housing, and hand-holes to facilitate
carrying are located in the front and rear of the housing.
The bottom of the housing is provided with a 10- by 10-inch
(2)
opening, normally closed by a spring actuated undercarriage
feeding mechanism a n d the cooling fan and motor. It is
mounted on parallel arms, which pivot on shoulder- screws,
fastened to the base of the projector.
The upper portion of the front of the housing forms a shelf
(3)
on which the lens assembly is mounted. The lens assembly is
equipped with a rack and pinion focusing device operated by a
focusing knob, and it is connected to the housing by means of
a bellows.
(4)
An optical pointer control knob is located on the side of the
housing, near the access door. On the front, in line with this
knob, is the aperture through which the pointer arrow is
projected. On the lower portion of the front are located on
ON-OFF switch, two fuse holders, the power cable receptacle,
elevating leg set screws, and a hand-hole.
ped with a 41
-inch diameter, 22-inch focal length projection anastig-
matic lens which is fully coated for maximum light transmission. The
lens barrel is anodized aluminum. The lens mount consists of an
aluminum casting and includes the pinion and focusing shaft which
is part of the rack and pinion focusing mechanism. The lens is held
in the mounting casting by means of a clamping screw, which clamps
the cast ing around the lens. A lens cap is provided to cover and protect
the lens when it is installed in the lens mount.
surface mirror picks up the light from the illuminated surface of the
copy and directs it toward the lens. The front surface mirror assembly
consists of a mounting frame, which has three pivoted mounting screws
on the back and two retaining channels on the forward side. One
mirror retaining channel is riveted to the frame; the other channel is
fastened with screws to permit replacement of the mirror in the event
of damage. The front surface mirror is designed for maximum light
reflection and minimum optical distortion.
e. Secondary Mirror Assembly (figs. 4 and 8). The secondary mirrors
5
