Abstract: A transparency is illuminated from the viewing side with a transparent planar structure producing ultraviolet light. A phosphorescent screen on the non-viewing side of the transparency produces visible light in response to the ultraviolet light to enhance the contrast. Back-illumination is used to provide adequate brightness in relatively dark areas.

Abstract: A transparency is illuminated from the back or non-viewing side through an array of apertures with a light source which is invisible to the viewer. This light passes through the apertures and, after passing through the transparency, is reflected back through the transparency to the aperture structure. The region between apertures is a light converter surface which converts the invisible light to visible light. The visible light passes through the transparency to the viewer with the multiple passes providing contrast enhancement. An additional visible light source is used to provide adequate brightness in relatively dense areas of the transparency.

Abstract: A transparency is illuminated from the viewing side with a light converter backing placed against the opposite side. The light reflected from the viewing surface of the transparency is rendered invisible to the viewer. A partially reflecting mirror is placed against the viewing side in regions of particularly low contrast to provide additional enhancement. Back illumination is used to provide adequate brightness in relatively dark areas.