Optical waveguides – Noncyclindrical or nonplanar shaped waveguide
Reexamination Certificate
1998-11-19
2001-03-20
Bovernick, Rodney (Department: 2874)
Optical waveguides
Noncyclindrical or nonplanar shaped waveguide
C385S901000, C362S035000, C362S559000, C040S547000
Reexamination Certificate
active
06205282
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a fiber-optic device for illumination of a light permeable information-bearing medium, such as a traffic, information or advertising sign, which comprises one or more preferably plastic panels, arranged over each other, operating as a display device, in which the light issuing from the fiber-optic device propagates parallel to a display plane thereof, which have means for two-dimensional or planar light distribution and in front of or on which transparent information entities are arranged.
So that the traffic, information or advertising sign is designed so that it is sufficiently visible in poor lighting conditions (nights, tunnels, eta), self-illuminating systems are increasingly utilized in addition to signs and billboards that are lighted from the outside with headlights. A closed system with a transparent (glass) front panel with interior illumination, preferably by fluorescent lights, is standard according to the state of the art.
The essential disadvantages of this prior art embodiment include the following: problems with water-tightness, susceptibility to vandalism, expensive maintenance and a comparatively uneven or nonuniform optical appearance of the illuminated sign.
On the other hand, fiber-optically illuminated information-bearing media are known which have no weaknesses in regard to the above-described mechanical properties and which also have a clearly improved appearance.
In the fiber-optically illuminated information-bearing medium described in German Patent Document DE 295 08 596 U1 the information bearing-medium to be illuminated comprises one or more plastic panels arranged on each other which are illuminated by fiber-optic means parallel to the display plane. Microstructures in the panels or mechanical modifications in the panels arranged over each other in a multi-panel system, which are typically made of acrylic glass, provide uniform light distribution over the entire panel surface. In microstructured panels the information entities to be illuminated are placed on or in special foils or sheets (e.g. “Diamond Grade” of 3M) that are glued outside on the panels to illustrate the desired information entities.
The fiber-optic component used is designed especially for the dimensions of the display to be illuminated. In most cases a discharge lamp is used as the light source.
In the known embodiments the light guide bundle is directly coupled with its light output ends at the plastic panels. Because of that the penetration depth of the light diffusely leaving the fiber-optic device in the object to be illuminated is limited. Also when the power of the lamp illuminating the fiber-optic components is increased, the light density gradient in the object itself is comparatively large. Further because of that the length of the individual arms of the fiber-optic device is limited, whereby the maintenance of the sign, which must be performed in comparatively inaccessible locations (e.g. over a road), is made more difficult.
Since a unique fiber-optic illumination arrangement is designed and built for each display in the current state of the art, currently such fiber-optic devices are very expensive and have high production costs.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a fiber-optic device for illumination of an information-bearing medium of the above-described kind in which the light density gradient at comparatively reduced lamp power is clearly reduced, the maintenance for displays in comparatively inaccessible locations is easier and the production costs for the fiber-optic devices are reduced.
According to the invention the fiber-optic device suitable for the various display requirements of various display devices is assembled in a modular manner from standardized parts of a standardized fiber-optic system with standardized different multi-arm light guides, and light outlet bodies acting as optical attachments that adjust the beam or propagation angle of the light issuing from them to provide light intensities of greater uniformity over an entire angular range are arranged in or on the individual arms of the fiber optic systems.
Use of optical attachments in front of the individual arms of the light guide bundle causes a greater direct penetration depth of the light leaving the fiber-optic device in the object to be illuminated. Because of that a reduction of the power of the light source is advantageously possible and also the light density gradient in the object is clearly reduced.
The optical attachment is preferably a light outlet body for fiber-optic light guides according to German Patent Document DE 42 25 323 C1, in which a tapered extension section whose jacket and/or end surfaces forms the light outlet surface is connected to the light outlet end surface.
The best illumination characteristics are obtained when this light outlet body has a truncated conical central region connected to a conically tapered extended section. The extended section can also be in the form of a pyramid, a cone or a truncated pyramid of similar form.
The optical attachment comprising a front-standing device causes an adjustment of the light propagation angle to provide more uniform light intensities over the entire angular range, whereby the advantages described herein were obtained. Furthermore the information provided in the above-described DE document extends the disclosure of the present invention by reference.
The improved optical properties allow the use of individual arms of a longer length in the fiber-optic component and thus a simplified maintenance of the illumination device, also of signs, which are mounted in inaccessible locations.
The increase of the light yield through the optical attachment is also so large that the sign or the billboard can be operated with a halogen reflector lamp with a maximum of only 50 watts of power. An economical production (price per piece about 30% less than comparable state-of-the-art fiber-optic systems) is possible by use of standard systems for mass-producing the fiber-optic device. The adjustment to specific display specifications occurs by variation of the number of standard parts employed, its arm number and the characteristics of the optical elements. Typically about 120 individual arms are sufficient for illumination of 1 m
2
of display surface.
If the specific illumination device is assembled in a modular manner like standard fiber-optic systems from its standard components, it can be used for a variable signal sign with fiber-optics as described in the Schott handbook “Variable signs according to the Schott System” of March 1996.
This standard system comprises
light sources or illuminating elements,
filters and
light guides with optical attachments.
The light sources are the central component of the system. The reflector lamp, the only part of the system that wears out, the light guides and if necessary colored filters, are assembled in it in a compact manner. They are so constructed that a uniform illumination of the light guide ends is guaranteed. If the light sources contain an illumination element, a simple device comprising a safety circuit with a reserve lamp may be provided, so that the system can operate with unchanging light engineering properties during failure of the main lamp.
These light sources can be operated with a light distributor to provide light simultaneously to two light guides. Because of that the required number of reflector lamps and the required electrical equipment is reduced.
In regard to the light guides with an optical attachment the standard system has a number of light guides which differ in the number of individual arms, the length of the light guides and the propagation characteristics/propagation angle of the optical attachments. Thus the system contains 20, 40, 60, 80, 100, 105 and 120-arm light guide arms of different standard lengths as standard components, among others with an active individual arm diameter of from 1.0 to 1.5 mm.
REFERENCES:
patent: 3962702 (1976-06-01), Kriege
patent: 5102227 (
Bovernick Rodney
Schott Glas
Stahl Michael J
Striker Michael J.
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