Luminaire and light-emitting panel

Details Luminaire and light-emitting panel Luminaire and light-emitting panel

2002-10-25

2004-06-08

Davis, Cassandra (Department: 3611)

Card, picture, or sign exhibiting

Illuminated sign

Edge illuminated

C362S035000

Reexamination Certificate

active

06745506

ABSTRACT:

BACKGOUND OF THE INVENTION
The invention relates to a luminaire comprising a panel of a light-transmitting material,
which panel includes a light emission window, a rear wall opposite said light emission window and edge surfaces which are situated between the light emission window and the rear wall,
at least one of the edge surfaces of the panel being light transmitting,
at least one light source being associated with the light-transmitting edge surface, and
in operation, light originating from the light source being incident on the light-transmitting edge surface and spreading in the panel.
The invention further relates to a light-emitting panel for use in the luminaire.
Such luminaires are known per se and are also referred to as edge lighting systems. They are applied, inter alia, in so-called luminous signs, among other things, for advertising purposes. They can also be used in guiding boards, such as “exit”-signs, in billboards, traffic lights, systems for guiding traffic flows and as (dashboard) lighting in vehicles. Said luminaires are further used as back lighting, for example, for display devices, such as LCD-devices. Said luminaires are used both as interior lighting and exterior lighting.
In such luminaires, a tubular low-pressure mercury-vapor discharge lamp, for example a (compact) fluorescent lamp (TL), is generally used as the light source, and the light emitted, in operation, by said light source is coupled into an optical waveguide which generally forms a relatively thin and flat panel, which panel is made, for example, of a synthetic resin or glass, and light being transported through the panel under the influence of total internal reflection. A text or a logo, for example a brand name, is engraved in the optical waveguide, the engraving lighting up, in operation, as a diffuse luminous area. The engraving is formed, for example, by etching or by suitably providing scratches. A text or a logo may alternatively be provided by applying a (light-scattering) layer on the panel. A text or a logo may alternatively be provided on a tape applied to the panel, which tape may exhibit differences in refractive index.
Such a luminaire may also be provided with an alternative light source in the form of a plurality of opto-electronic elements, also referred to as electro-optic elements, such as electroluminescent elements, for example light-emitting diodes (LEDs). These light sources are generally provided so as to be close to or abut against a light-transmitting edge surface of the panel, so that, in operation, light originating from the light source is incident on the light-transmitting edge surface and spreads into the panel.
From DE-A 38 33 315 an LED edge lighting system is known, which comprises one or more light-emitting diodes which are coupled via optical waveguides to a light-emitting panel to cause a light surface or light symbol provided in or on the light emission window to light up. This light surface or light symbol is provided as a light-scattering layer on the surface of the panel, or as a light-scattering recess in the surface of the panel.
A luminaire of the type mentioned above has various drawbacks. For example, only a part of the light in the panel contacting the light symbol is coupled out of the panel, and, in addition, a part of the light is emitted in the direction of the rear wall. Besides, the light symbol lights up like a diffusely luminescent area. As a result, the attractiveness of the luminaire is reduced.
SUMMARY OF THE INVENTION
It is an object of the invention to obviate the above drawbacks. The invention more particularly aims at providing a luminaire of the type mentioned in the opening paragraph, in which light is coupled out so as to obtain a specific light distribution.
To achieve this, the luminaire is characterized in accordance with the invention in that
in the panel a plurality of deformities is provided for coupling light out of the panel via the light emission window,
said deformities being clustered so as to form at least one light symbol, and
said cluster having a configuration which corresponds to the shape of the light symbol.
The measure in accordance with the invention causes the attractive effect, the appeal and the attention value of the luminaire in accordance with the invention to be increased. The term “deformities” is to be taken to mean, in general, in the description and the claims of the current invention, means by means of which light can be coupled out of the panel. A deformity is an optical structure having a predetermined geometrical shape and dimensions. The use of deformities enables light to be coupled out of the panel in a well-defined manner. The light is coupled out in a predetermined direction, which direction may also depend upon the shape and the position of the deformity on the panel. This means, inter alia, that an observer who moves past the luminaire without specifically looking in the direction of the panel is struck at a certain moment “from the corner of his eye” by light emitted by the luminaire in accordance with the invention. This unexpected occurrence arouses the attention of the observer and “forces” as it were the observer to look at the luminaire. This results in an increase of the attention value of the luminaire.
The deformities serve as a secondary light source.
An additional advantage of these deformities is that clusters of deformities can be selectively illuminated. By virtue thereof, it becomes possible to make different light symbols light up independently from each other and/or sequentially. By making light symbols light up alternately, using control electronics, by causing the clusters of deformities associated therewith to couple light out of the panel, light objects that move as it were can be obtained (for example a man who seems to be walking), or a text can be made visible by making the letters light up one after the other. Also various, colored light sources can be alternately switched on and off, so that a light symbol lights up in various colors. In this manner, the luminaire in accordance with the invention obtains dynamic lighting possibilities with a high attention value.
A further advantage of these deformities is that more light is coupled out of the panel, which leads to a directed reflection of these deformities and hence an improved brightness of the luminaire. To direct the light which is coupled out of the panel by these deformities, preferably, a boundary surface of the deformities is provided with a specularly reflecting surface, for example a reflecting layer of aluminium or silver, or a reflective multilayer coating. In an alternative, preferred embodiment, the deformities are shaped such that, in the deformities, total internal reflection causes the light to be coupled out of the panel. An important advantage of total internal reflection as a way of coupling light out of the panel is that it is not necessary to locally provide the deformities with a reflecting surface.
In the known luminaire, light incident on the diffusely reflecting light symbol when being reflected to and fro in the panel is emitted in all directions, for example also in the direction of the rear wall. As a result, the brightness of the luminaire in a direction transverse to the panel is lower than that of the light source, leading to a reduction of the attractiveness of the luminaire.
It is to be noted that the provision of a plurality of deformities to couple light out of a luminaire is known per se. In such edge lighting systems, a plurality of light-extracting so-called “deformities” or “disruptions” are provided in the light-emitting panel. The shape and/or dimensions of these deformities may change gradually and/or the distance between the deformities in the panel may change gradually. However, the objective of such edge lighting systems is to obtain a light distribution which is as uniform as possible, said systems serving, in particular, as a lighting panel for, for example, (flat) display devices, such as, for example, liquid crystal display devices. The light distribution

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