Epidiascope

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epidiascope

[‚ep·ə′dī·ə‚skōp]
(optics)
An optical projection system for forming an enlarged real image of a flat opaque object, in which light is reflected from the object and then from a mirror before being focused by a projection lens. Also known as episcope.
An optical projection system which can easily be altered to project either transparent or opaque objects.

Epidiascope

 

a device for forming an image of an opaque object on a screen as well as for projecting a transparent image, or diapositive, of an object onto a screen. An epidiascope is a projector whose optical system consists of a combination of an episcope and a diascope (see Figure 1).

In diascopic projection, the diapositive is illuminated by a light beam directed through it; thus, the image formed on the screen is sufficiently bright even with a weak light source and projection lenses with low transmission characteristics. Episcopic projection requires the use of light sources that are more powerful and high-transmission lenses.