3M
Overhead Projector 9800 Series
Section 1 – Introduction
1-4
9800 Service Manual
3M 1996
1.3X Magnifier Lens
The 1.3X magnifier lens is used to enlarge the image
of LCD panels. When the magnifier lens is rotated
into position under the projection lens, light will pass
through the magnifier lens and then into the
projection lens. With the magnifier lens, the focal
length is reduced to 292 mm (11.5 in.).
Projection Lens
The projection lens collects the light and images
transmitted from the Fresnel lens and 1.3X magnifier
lens (if used) and projects them onto the surface of the
projection mirror. The projection lens is raised or
lowered by the focus mechanism to obtain the
sharpest projected image. The focal length of the
projection lens is 342 mm (13.5 in.).
The 9800 projector has an open head design with
triplet lens and 1.3X magnifier lens. Figure 1-4.
Open Head
Triplet Lens
FL=342 mm, 13.5 in.
9800–51I
1.3X Magnifier Lens
FL=292 mm, 11.5 in.
Figure 1-4. Projection Heads
Projection Mirror
The projection mirror redirects the light from the
projection lens to the projection screen. The angle of
the mirror determines the height of the projected
image on the projection screen.
The distance from the projection mirror to the
projection screen determines the size of the projected
image. Using the magnifier lens and/or LCD panels
will alter the projector to screen distances. Refer to
Section 1-2-5.
1-2-2. Cooling
Cooling of the overhead projector is accomplished by
a motor-driven fan located inside the projector body.
Cooling air is drawn into the projector through the
ventilation slots (A) and exits through opening B.
Figure 1-5.
It is important not to restrict the flow of cooling air by
placing the projector too close to the wall (leave
approximately one foot clearance) or placing objects
too close to the ventilation slots or under the projector
or by leaving foreign objects inside the projector.
B
A
9800–52I
A
Figure 1-5. Cooling
