b. Opaque Projector. Unlike the overhead projector, an opaque
projector reflects light from the surface of an opaque object rather
than passing through it. You would use this type of projector to
display the pages of a magazine or book, photographs, charts, etc., up
to 10 inches in size. It also can project any relatively small, flat
objects such as cams, gears, and coins without prior preparation. Most
opaque projectors use a 1000watt lamp.
(1) Using the opaque projector. This projector has three
positions that function the same as the older overhead projectors, with
the first position from off (middle position) controlling the operation
of the blower. An opaque projector has a feedbelt that feeds material
into the projector smoothly. Place the copy on the feedbelt, turn the
feedbelt handle, and center the image on the screen. If you have a
thick copy, insert it into the projector by unlocking the carriage,
moving it down with the copy space handle, and inserting the copy. Once
you have the image on the screen, use the focusing knob to adjust the
clarity of the picture.
(a) Advantages of the opaque projector. To protect the copy
from the heat generated by the lamp, this projector has a heat filter.
Additionally, the carriage has a glass pressure plate to help keep
photos and books flat for projection.
(b) An advantage of this projector is the pointer window and
handle. This window projects a small arrow on the screen that you use
to emphasize points on the screen. Moving the pointer handle up and
down moves the arrow vertically on the screen, and moving the pointer
handle left and right moves the arrow horizontally on screen.
(c) You also have the capability of increasing or decreasing
the magnification with this projector. To increase the magnification,
loosen the lens screw and move the lens back in its mount. To decrease
the magnification, pull the lens out, but no more than one inch.
(2) Cleaning an opaque projector. To ensure an opaque projector
also presents the image clearly, you must clean the optical element's
external surfaces with a lintfree cloth or lens tissue occasionally.
(The manufacturer seals the lens; therefore there are no internal
surfaces for the operator to clean.) To gain access to the rear surface
lens, secondary mirrors, and parabolic reflector, open the rear of the
projector.
The most important and delicate optical surface you must clean is the
front surface mirror. Do not touch the mirror, leave
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