||The English used in this article or section may not be easy for everybody to understand. (June 2012)|
It has four main elements:
- an electric light bulb,
- a reflector and "condensing" lens to direct the light to the slide,
- a holder for the slide
- a focusing lens.
A flat piece of heat absorbing glass is often placed between the condensing lens and the slide, to avoid damaging the slide. This glass absorbs infrared. Light passes through the transparent slide and lens, and the resulting image is enlarged and projected onto a screen. So the audience can view its reflection.
The image may be projected onto a translucent "rear projection" screen. That is used for continuous automatic display for close viewing. This form of projection also avoids that people who look at the show interrupt the light stream or bump into the projector.
Slide projectors were common in the 1950s and 1960s as a form of entertainment; family members and friends would gather to view slideshows.
As of October 2004, Kodak no longer manufactures slide projectors. It is also increasingly difficult in some countries to locate photo processors who will process slide film.