Illuminated display

DETAILED DESCRIPTION This invention provides an improved illuminated display for clearly and durably communicating information to an observer positioned forward of the display.
A display of the invention is formed from a material having an index of refraction substantially greater than 1.
A plurality of prisms are formed on the rear surface of the display and are arranged in a shape which is representative of the information to be communicated.
The prisms redirect the light entering them into a collimated light beam having a transverse cross section which is in the general shape of the display.
As the collimated beam passes through the forward surface of the display, it is directed to be readily visible by the observer.
In an especially useful embodiment of the invention, the display comprises an operator display having a generally circular cylindrical rearward portion which defines a circular cylindrical space and a peripheral flange portion which is disposed radially outward from and forward of the cylindrical portion.
A support means mounts the cylindrical portion and holds the indicator lamp within the cylindrical space.
The prisms are formed on the rearward surface of the flange portion.
Light emitted from the filament passes through the cylindrical portion before being redirected by the prisms into generally parallel rays in the shape of the display which pass through the forward surface of the flange portion.
In another aspect of the invention, the prisms comprise a series of concentric ridges.
Each ridge has an entrance surface and a reflecting surface.
Light emitted from the filament enters the entrance surface and is refracted so that it is incident upon the reflecting surface at a relatively large angle.
The ray is thereby reflected by total internal reflection at the reflecting surface so that the ridges act as catadioptric prisms.
In another aspect of the invention the forward surface of the flange portion is slanted rearwardly.
Light from the reflecting surface of the ridges is refracted by the forward surface to be generally parallel to the horizontal axis of the cylindrical portion