Opaque projector

The opaque projector, or episcope is a device which displays opaque materials by shining a bright lamp onto the object from above. The episcope must be distinguished from the diascope, which is a projector used for projecting images of transparent objects (such as films), and from the epidiascope, which is capable of projecting images of both opaque and transparent objects. 
A system of mirrors, prisms and/or imaging <a href="/facts/Lens_(optics)/ejlH6n5c">lenses</a> is used to focus an image of the material onto a viewing screen. Because they must project the reflected light, opaque projectors require brighter bulbs and larger lenses than <a href="/facts/Overhead_projector/M8V2Y4xa">overhead projectors</a>. Care must be taken that the materials are not damaged by the heat generated by the light source. Opaque projectors are not as common as the overhead projector.
Opaque projectors are typically used to project images of book pages, drawings, mineral specimens, leaves, etc. They have been produced and marketed as artists' enlargement tools to allow images to be transferred to surfaces such as prepared canvas, or for lectures and discourses.

Opaque projector open-in-new

Opaque projector