Overhead Transparency Projector

The overhead transparency projector (fig. 16-10) must be kept as clean as possible for obvious reasons - dirt, dust, hair and other foreign objects that attach themselves to the outside lenses or optical stage will be distracting to the viewer and result in an unprofessional presentation.

Clean the outside lenses and optical stage with an approved lens cleaner or a mild detergent solution and a clean, soft, lint-free cotton cloth. Do not use paper

Figure 16-10. - Overhead transparency projector.

Figure 16-11. - Opaque projector.

cloths because they may scratch these surfaces. Rinse and dry all optical surfaces after cleaning them. Permanent damage can result if they are not rinsed and dried thoroughly. Any accumulated surface dirt on the mirrors should be removed with a camel hairbrush only.

Opaque Projector

Simple care and occasional cleaning keeps the opaque projector (fig. 16-11) in good working order. Clean its optical elements (projection lens, parabolic reflector, secondary mirrors, front surface mirrors and projection lamp) by wiping them with a lint-free rag, damp chamois or lens tissue.

The front surface mirrors are the most important optical elements of the opaque projector. When you compare an ordinary mirror to a front surface mirror, you will see that the reflective coating of the front surface mirror is fully exposed, hence its name. The coating of a regular mirror is located at the rear of the glass. Consequently, the front surface mirrors of an opaque projector are extremely delicate. Do not get your fingerprints or other marks on it. If the mirrors are not soiled, then any dust accumulation can be removed with a soft camel hair brush. If they are badly soiled, wipe them very gently with a lint-free cloth or lens tissue. (Use extreme caution when you use the cloth or tissue - they can scratch the surface of the mirror.)

Carousel Slide Projector

The cleaning procedures for the Carousel slide projector (fig. 16-12) are essentially similar to those used for the opaque projector. The Carousel uses a standard mirror, so you should remove surface dirt with a camel hairbrush. l l