JP2008517325A - Dynamic message indicator - Google Patents

Abstract

  The illumination message indicator (10) includes a light emitting device (5), a translucent retroreflective film (2) arranged to be illuminated by the light emitting device (5), and an indicator (1). Are arranged in front of the translucent retroreflective film (2). The indicia (1) includes at least an active portion (11) configured to dynamically display variable information and may further include a passive portion configured to display invariant information.

Description

  The present invention relates to dynamic message indicators or displays, and more particularly to backlighting message indicators or displays for dynamically displaying variable information.

  Lighting message signs are generally known. The lighting sign can be front lighting or back lighting. Front writing message signs typically include signs such as bulletin boards or other displays in which light is illuminated toward the sign at an angle from the periphery of the sign.

  Backlighting message signs typically have a translucent surface through which light is seen and on which a message or display is placed. The uniformity of the light emitted from the translucent surface is important. Thus, the translucent surface often includes some element that diffuses light to reduce identification by the viewer of the light source in the sign housing. However, such diffusing elements absorb most of the light emitted by the light source. In order to provide sufficient brightness to be clearly visible to the viewer, the light source used for known backlighting message signs must be powerful. Several light sources are often used to provide sufficient brightness and to distribute the light emitted by the light source as uniformly as possible inside the housing. In order to provide sufficient space for such powerful light sources, known backlighting message indicators generally exhibit a large rear depth. Thus, the disadvantage of known backlighting message signs is high material consumption. Furthermore, due to the presence of several light sources, known backlighting message signs are high power consuming and generate a significant amount of heat.

  Active displays for dynamically displaying variable information are generally known. U.S. Pat. No. 5,394,308 discloses a lighting device for illuminating a liquid crystal display (LCD) panel from the back, which is asymmetric contrast when viewed in the vertical direction when illuminated uniformly. Indicates the ratio. A background lighting device for a liquid crystal display is also disclosed in US Pat. No. 5,667,289. The apparatus described therein comprises a distributed diffuser system for diffusing and reflecting light that enters the interior of the highly reflective internal plate, substantially the entire perimeter surface of the transparent plate, and the light entering the plate. Including. The diffusing system includes a pattern of diffusing elements whose area ratio is maximum at the center of the pattern. Thus, the diffusion system of the lighting device exhibits a complex structure. In particular, it is difficult to achieve balanced illumination of transparent plates.

  U.S. Pat. No. 5,452,532 discloses a road sign to indicate to the driver a message that can be customized under direct and backlighting conditions, wherein the message element and the background element represent a mosaic message. Placed in suitable mounting holes to form, each mosaic has a retroreflective portion surrounded by a translucent border. Due to the large size of the message elements, the display resolution is poor. Furthermore, the separation of retroreflective and translucent parts results in complex structure and efficiency problems. As the driver approaches the road sign, only a part of each element is illuminated, which results in a phantom effect.

  Despite the known lighting signs, there is a continuing need to provide further lighting message signs. Preferably, these labels have improved advantageous properties.

  The present invention provides an active lighting message indicator for dynamically displaying variable information that can be combined with a passive portion for displaying invariant information. Message beacons have improved luminance efficiency and reduced power consumption. Furthermore, the present invention can provide redundancy for both active and passive display elements by retroreflective backup after a power failure. Thus, even during a power failure, the sign can still provide useful information to the user. In addition, the message indicator provides the possibility to control the active part in the event of a power failure so that a default message is displayed, for example a pre-programmed message informing the viewer that the indicator is abnormal.

  The illumination message sign includes a light emitting device, a translucent retroreflective film arranged to be illuminated by the light emitting device, and an indicia, wherein the sign is disposed in front of the translucent retroreflective film. Is done. The indicia includes at least an active portion configured to dynamically display variable information and can further include a passive portion configured to display invariant information.

  In the message sign according to the invention, the light emitting device may comprise a light source and a light path that may be hollow or solid. The light emitting device can also include a large surface light source, such as a self-emitting light source based on inorganic electroluminescence (IEL) or organic light emitting diode (OLED) technology. The structure and function of such an OLED is described, for example, in the online magazine Shot Info 99/2001.

  The amount and distribution of light extracted from the front of the light guide can be improved by providing a back reflector located on the back and / or side of the light guide or self-emitting light source. Both the back reflector and the side reflector are preferably a diffuse reflection film, a specular reflection film, or a scattering reflection film having a high reflection efficiency. Placing a reflector, and in particular a highly diffuse or highly specular or highly scattering reflective film, along the back and / or side of the light path allows light to escape substantially only through the front. Providing a light path that can be used to illuminate the indicia with most of the light from the light source. Such a design is therefore highly efficient with regard to the required brightness, uniform illumination and power consumption.

  In the case of a hollow light guide, the light guide preferably includes a cavity having a main front surface and a main back surface. The front surface is defined as the cavity-facing surface facing the viewer, and the back surface is positioned substantially opposite the front surface and away from the viewing direction. The front and back surfaces can have any suitable shape, such as a square, rectangle, polygon, or circle. The translucent retroreflective film is disposed on at least a part of the front surface, and the reflector is arranged on at least a part of the back surface. Preferably, the retroreflective film covers substantially the entire front surface of the cavity. The reflector preferably covers substantially the entire back surface of the cavity. The light sources are arranged inside the cavity, preferably centered with respect to the vertical and / or horizontal dimensions of the front surface of the cavity. Within the cavity, light is numerous in the front, back, and any side until light strikes the front and translucent retroreflective film at an angle at which light is transmitted through the translucent retroreflective film from the front of the light path. It is transmitted by reflection.

  The translucent retroreflective film can be a bead, a prism, or can be provided with a cube corner, as is known to those skilled in the art. Typically, any type of translucent retroreflective film can be used. In particular, a light transmissive retroreflective film used for traffic signs can be used. For example, cube corner retroreflective films such as those described in U.S. Pat. No. 4,588,258, U.S. Pat. No. 5,122,902, and WO 98/20375 are disclosed in US Pat. Useful as a translucent retroreflective film for illuminated message signs according to the invention. The cube corner retroreflective films described in these references provide improved angularity along a number of viewing planes. The film can include at least one matched pair of cube-corner retroreflective elements that are rotated 180 ° relative to each other, with the three lateral mutually perpendicular surfaces of the elements being in a common plane. By the edges, defined at their base, the optical axes of the elements are tilted towards each other. Further, the article can include several types of prism retroreflective elements. In some embodiments, the base edges of the lateral faces of adjacent elements define a separation surface between the bases of the elements. In other embodiments, a portion of the element is removed to define a truncated surface on the element. A bead retroreflective film comprising retroreflective microspheres, as disclosed in US 4,005,538 traffic signs, can also be used.

  In front of the translucent retroreflective film, indicia are arranged in the form of graphics and / or characters, for example. In accordance with the present invention, in the general sense all indications are means arranged to give information to the viewer. The sign includes at least an active portion for dynamically displaying variable information. The active part can be operated by an electronically controlled shutter system, such as a dichroic LCD type system and / or a twisted liquid crystal system. A modular LCD display system useful in the present invention can provide a display of letters, numbers, and specific graphic symbols formed by an array of elements arranged in an individually controlled matrix element or mosaic structure. . Mosaic elements can be specifically designed to display letters and numbers, and matrix elements can also be suitable to show any kind of graphic art. The LCD display system can be based on ETN (enhanced twisted nematic) technology, the contrast ratio at certain wavelengths is improved over twisted nematic displays by using dyes doped with liquid crystals Is done. A suitable LCD display system is a modular LCD display system available under the trade name Geascript from Ulm, Germany AEG / MIS.

  In the active part, a display system, for example a modular LCD display system as described above, or a similar display system can form the indicia. Further, the marking film can be arranged between the translucent retroreflective film and the shutter system. The marking film in the active portion can be, for example, a colored film to give a colored appearance of the desired color to the markings displayed by the modular LCD display system as described above. Alternatively or additionally, the indicia can be formed on an indicia film, which can be displayed or covered by an active part shutter system. Thus, in monochrome mode, in white or in color, in a positive (black lettering, white or colored background) image, or in a negative (white or colored lettering on black background) image and / or Graphic information can be displayed.

  The indicia can further include a passive portion for displaying invariant information, as is generally known in the art.

  The indicia can be arranged, for example by displaying directly on a translucent retroreflective film, or can be supported by an additional film (indicating film). In a preferred embodiment of the invention, the marking film is laminated onto the transparent support film by a transparent optically clear adhesive. Most preferably, the adhesive has a refractive index of 1.3 or less. A translucent retroreflective film can also be adhered to the support film. This arrangement can be placed in front of the light emitting device and then removed. The light emitting device and the support film can be mechanically secured, for example, by a fixing bar arranged on the frame of the message sign. Alternatively, the translucent retroreflective film can be provided directly with the indicia displayed thereon or otherwise applied thereto. The marking film and / or translucent retroreflective film can be adhered directly to the front surface of the light emitting device, most preferably by an optically clear (transparent) adhesive having a refractive index of 1.3 or less.

  A suitable marking film to be used in the present invention is available from 3M Company under the trade name Scotchlite® ElectroCut® Film Series 1170. Is possible.

  If the light emitting device includes a light path and a light source, the light source emits light substantially along its length and is an elongated luminant, such as a light tube, such as a fluorescent tube, or Can be an elongate light source including several individual light emitters spaced apart from each other and / or arranged adjacent to each other along the length of the light source. Thus, the elongate light source can include a linear region of separate light emitting elements. The advantage of providing a plurality of light emitting elements arranged in rows or arrays instead of a common light source is that in the case of individual light emitting element failures, message sign illumination is still provided.

  The message sign according to the present invention can be used, for example, as a traffic sign or traffic information board, as an airfield sign, or as an advertising sign. The message sign according to the present invention combining active and passive display elements is particularly useful in multi-tier parking lots or as parking lot information boards.

  The present invention provides a message sign having a unique slim design and approximately 180 ° legibility. The message sign provides a redundant system after a power failure by combining backlighting with retroreflective features for both active and passive display elements. Luminance efficiency is significantly improved compared to known backlighting message signs, and thus power consumption is significantly reduced. Message indicators are cost competitive and even have an increased cost-benefit ratio over current backlighting systems. 30.000 hours, such as the Aura® Long Life Light fluorescent lamp available from Aura Light AB, Karlskrona, Sweden, for example, Karlskrona, Sweden From, for example, cold-cathode fluorescent lamps (CCFLs) and modern LED lamps with a rated lifetime up to 50.000 hours such as modern LED light sources arranged in rows or arrays, the lamp maintenance cycle is strongly Can be reduced or even eliminated. Additional energy savings can be obtained when using new generation lamp electronics.

  A further advantage of the message sign according to the invention is that the active display module can also be realized in non-lighting signs, in particular in non-backlighting signs. An active display module can be implemented in existing signs that may or may not be lit. In addition, sign manufacturers or remodelers can use their own stock materials. Due to the reduced size of the message sign housing, smaller aluminum extrudates can be used, thereby saving cost and weight.

  Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

  Throughout the drawings, the same elements and portions of different embodiments of the invention are designated by the same reference numerals.

  In FIG. 1, FIG. 1A and FIG. 1B, a first embodiment of a message sign according to the present invention is shown in more detail in a cross-sectional view. The frame 20 that forms the message sign housing 10 with the rear wall 30 is manufactured from an aluminum extrudate or plastic or other suitable material. A cavity 15 including a front surface 16 and a back surface 17 is formed inside the housing. The light source 5 is arranged inside the cavity 15. In the embodiment shown in FIG. 1, the light source 5 is, for example, a fluorescent lamp having a long rated life, such as an Aura® fluorescent lamp, or a fluorescent lamp, such as a cold cathode fluorescent lamp (CCFL). An elongated light source. However, other suitable light sources can be used. On the back surface 17 of the cavity, a high specular reflector or a highly diffuse reflector including a specular reflection layer or a diffuse reflection layer 4 and a support layer 6 is arranged. In FIG. 1, the back surface 17 that supports the reflector 4 is bent so that light emitted from the light source 5 toward the back surface 17 of the cavity 15 is redirected toward the front surface 16. The lamp electronics 22 can be arranged inside the housing 10 in an unused space between the reflector 4 and the rear wall 30.

  Alternatively, the reflectors can be arranged along the back and sides of the housing such that the housing 10 forms a cavity.

  The back reflector is preferably composed of a film. For example, such films are available from the 3M Company of St. Paul, USA (3M Company, St. Paul, USA) under the trade name Radiant Mirror Film VM 2000, VM 2002, or VM 2000 F1A6, Or available from Light Enhancement Film 3653-100. In the above arrangement, substantially all of the light emitted from the light source 5 can only exit through the front face 16 of the cavity 15 to create the illumination side of the light path.

  The light source instead comprises a plurality of light emitting diodes (LEDs) arranged in an array or cluster on the rear wall 30 of the housing 10 or on a separate layer between the rear wall 30 and the front surface 16 of the cavity 15. Can be included. In this case, a reflective film can be arranged between the LEDs. In addition, a solar reflective film that reflects infrared solar energy and transmits visible light can be arranged on the front surface 16. Thus, such a film reduces the heating of the cavity 15 by solar irradiation, and excessive heating may lead to LED degradation or even destruction. Suitable solar reflective films that can be used in the present invention are available, for example, under the trade name Automotive SRF 1100 from 3M Company of St. Paul, USA.

  The front surface 16 of the cavity 15 is formed by a sandwich structure of several layers including the translucent retroreflective film 2 and the marking film 1. On at least a part of the front surface, a further layer 11 comprising an electronically controlled shutter system, for example a liquid crystal cell, is arranged to form the active part of the marking. In the passive part, the marking film 1 is provided with markings in the form of letters, numbers or graphics. In the active part, the shutter system can be used to display or cover the markings provided on the marking film 1 as required. Alternatively, the use of a modular LCD display system (eg, a “Geascript” brand LCD display system available from the AEG / MIS Company, Ulm, Germany), Ulm, Germany. And the mosaic or matrix structure of the LCD elements allows individual information such as letters, numbers, and / or graphics to be displayed. A colored appearance of display information using a modular LCD system is provided by arranging a colored marking film 1 having a desired color under the LCD system in an area where the display information should appear in the desired color. be able to.

  The translucent retroreflective film 2 can be a bead film or a prism film, or preferably a cube corner film, as is known to those skilled in the art. Preferably, a cube corner film is used. Such a film to be used in the present invention is the trade name Scotchlite (R) Diamond Grade (R) Translucent Reflective Sheeting from 3M Company of St. Paul, USA. ) Available at 3990 T. The retroreflective properties of this film hit the marking film 1 and are used for both external light passing through the marking film 1 and internal light from the light emitting device. In the latter case, the translucent retroreflective film 2 along with the back reflector (support layer 6 and reflector layer 4) provides multiple light reflections through the cavity 15, resulting in a homogeneous illumination of the front of the cavity. Light emitted from the light source that strikes the translucent retroreflective film 2 at an angle within a certain range, for example, about −45 ° to + 45 ° with respect to a line perpendicular to the film, is an optical property of the translucent retroreflective film 2. Is reflected backward. Therefore, the light source can be arranged near the translucent retroreflective film 2 without destroying the illumination uniformity. This allows for improved brightness at the distance from the viewer to the sign as shown in FIG. 4 described below.

  As an alternative to a separate marking film 1, the marking can be displayed directly on the translucent retroreflective film 2. When using a display system, such as a modular LCD display system, in the active part, instead of providing a colored marking film, a colored translucent retroreflective film is used to give the desired color to the marking Can do.

  In the embodiment shown in detail in FIG. 1A, a cover layer 3 is provided to keep the sandwich structure including the translucent retroreflective film 2, the marking film 1 and the shutter system 11 in an adjacent position. The cover layer may be made of glass or transparent plastic, eg, GE-Lexan® available from GE Structured Products, Pittsfield, USA, Pittsfield, USA. it can. Alternatively, as shown in detail in FIG. 1B, the retroreflective film 2 and the marking film 1 are made with a light transmissive adhesive 6, for example, a stretch release type VP 5290 available from 3M Company of St. Paul, USA. Can be glued to each other and to the shutter system 11. Further, a sealing film 22 can be provided between the frame 20 and the outermost layer of the sandwich structure to protect the cavity against dust contamination, humidity, and the like.

  A sandwich structure comprising different layers as described above is mechanically secured to form the front surface of the cavity by any suitable mechanical fastening means such as a clamp. In the embodiment shown in FIG. 1, the housing 10 including the back wall 30 and the frame 20 protruding therefrom surrounds the cavity 15, the light source 5, and the layers of the sandwich structure. The sandwich layer is secured between the front part of the frame 20 and the fixing bar 21. The frame 20 defines an opening in which the front surface of the cavity is exposed. The frame 20 can be secured to the rear wall 30 by any suitable means, such as screws, clamps, etc., allowing assembly of the message sign.

  A second embodiment of a message sign according to the invention is shown in cross-section in FIGS. 2 and 2A. The difference between the message sign according to the second embodiment and the message sign according to the first embodiment of FIG. 1 is related to the structure of the light guide. According to FIG. 2, the message sign comprises a solid light guide 41 made of a transparent synthetic material, for example acrylic, such as polymethylmethacrylate or polycarbonate, and having a plate-like shape. The solid light guide 41 essentially replaces the substantially empty space between the front and back of the cavity of the first embodiment shown in FIG.

  The optical path 41 includes a main front surface 41a, an opposing main back surface 41b, and opposing side surfaces. The light source 5 ′ is arranged along at least one of the side surfaces (in the embodiment shown in FIG. 2, along the upper and lower side surfaces 20 of the light guide). The light source 5 'can be an elongated light source, for example, a linear lamp such as a cold cathode fluorescent lamp (CCFL). The lamp can be secured to the light path using a clear UV resistant silicone spot 52. Alternatively, the elongate light source can include a carrier strip that supports a number of LEDs arranged side by side to form a linear array, such as a printed circuit board. The light source 5 ′ provides edge illumination of the solid light guide 41.

  A high specular reflector or highly diffuse reflector 51 acting as a lamp reflector is provided along the side surface of the light guide 41 and on a part of the front surface 41a and the back surface 41b of the light guide adjacent to the light source 5a. This reflector is preferably adhered to the optical path 41 by an optically clear (transparent) adhesive having a refractive index of 1.3 or less. Other optically clear adhesives can also be used. Suitable adhesives are available from 3M Company, St. Paul, USA (eg, # 8141, # 8142, # 8161, or # 9483). A highly diffuse back reflector or a high specular back reflector 4 ′ is arranged to face the back surface 41 b of the optical path 41. The back reflector 4 'and the lamp reflector 51 are made of the same material and serve the same purpose as the back reflector 4 of the first embodiment of the invention shown in FIG.

  In order to further improve the uniformity of the illumination of the front surface of the light guide 41, the light guide 41 is provided with light scattering particles that are substantially homogeneously distributed within the material of the light guide 41 and have different light diffraction characteristics. be able to.

  In an alternative embodiment of the message sign according to the invention which uses a solid light path, the solid light path has a wedge-like shape including a narrow side and an opposing wide side, and the light source is wide of the solid light path. Arranged along the side. This tapered embodiment of the solid light path increases the number of reflections at the back of the light path within a narrow portion, i.e., a portion spaced from the light source, which compensates for the reduced intensity of the reflected light. The advantage is brought about. Thus, when the light sources are arranged along at least a portion of only one of the sides, the tapered configuration results in a more equal distribution of light.

  In the second embodiment of the present invention, the translucent retroreflective film 2 having the marking film 1 can be directly bonded to the front surface of the solid optical path 41 by the adhesive layer. This adhesive layer can preferably be a stretch release adhesive tape VP 5290 available from the 3M Company of St. Paul, USA. However, other optically clear adhesives can be used. The adhesive does not leave residue on the front of the light path so that the sign film 1 and the translucent retroreflective film 2 can be replaced with another combination of the sign film and the translucent retroreflective film. It must be possible to peel from the waveguide 41.

  FIG. 3 shows a photograph of the front of the message sign according to the invention. In the example shown in FIG. 3, the message sign is a parking lot information board including a passive part 101 and an active part 111. In the passive part, invariant information such as name and road to the parking lot is displayed, and the active part 111 displays variable information such as the number of free parking places in the parking lot. Furthermore, the message signs according to the invention can be used, for example, as parking sign indication signs, instruction signs for highways, driver feedback signs, eg signs indicating the actual speed of the car, or traffic signs, and traffic information boards Can be used. Other uses of active message boards or message boards that combine active and passive parts, such as traffic signs connected to traffic management controls, radio, or traffic signs remotely operated by a GPS / GMS communication system, Intended.

  The new active display module according to the invention can be realized in standard retroreflective-but non-illuminated-signs or information boards and in transilluminated and retroreflective signs or information boards. The message sign of the present invention has significant advantages in traffic safety due to the unique combination of lighting and retro-reflective sign features in one dynamic traffic sign or information board. In the message sign of the present invention, sign readability is never critical at any sign distance or viewing angle.

  The brightness of the message sign according to the invention with respect to the distance from the viewer to the sign is shown in FIG. The luminance value is determined as follows.

  The curve marked TGD VIP 3990T was determined with two sets of general optical measurements, after which the dependence on distance was calculated.

  The first set of measurements was taken with a LMT GOH (Photogoniometer) at a voltage of 13.0 volts, measured at the lamp socket, using a used VW Passat car right headlamp. Luminous intensity was defined over the horizontal and vertical angular range (± 5-15 degrees) that typically occurs for these applications.

  The second set of measurements was performed on the relevant part retroreflected by the Scotchlite® Diamond Grade® translucent retroreflective sheet TDG VIP 3990T, again in three angular ranges: the surface of the sheet. Obtained by measuring over a vertical angle and a horizontal angle with respect to an axis perpendicular to the angle between the incident beam and the retroreflected beam.

  Next, the curve shown in FIG. 4 was obtained by calculating the luminance for distances in the range of 0 to 200 m. The brightness itself does not depend on the distance, but for each distance between the sign and the vehicle, the sign itself is 10 m off the road and at a height of 3 m, and there are various distances between the sign and the vehicle. Different angles result from providing an angle. These angles increase significantly as the vehicle approaches the sign and the sign shift becomes significant, so the retroreflection actually approaches zero.

The following method was used for the lighting curve. The label was selected so that a brightness of 25 cd / m ² was obtained when measured in a direction perpendicular to the label surface, ie, with zero vertical and horizontal angles. The relative luminance is then measured using a remote photometer, eg, a PR 650 Spectra Colorimeter (Spectra Colorimeter from Photo Research in Chatsworth, Calif., USA), USA. Measured as a function. These measurements corresponded to providing a form of curve, which was then set to 25 cd / m ² for a distance of 200 m and the label brightness was chosen to have this value. Inside the signage, the light is not reflected back at an angle of more than 45 degrees, so that there is a significant increase in illumination beyond these angles and therefore also at a distance between the sign and the vehicle of less than 50 m. Is obtained.

  The total curve is an addition of the two above curves and shows that, unlike a simple retro-reflective sign, the sign according to the present invention provides higher brightness at a small distance between the sign and the vehicle.

  Although the invention has been described and illustrated with reference to specific exemplary embodiments thereof, it is not intended that the invention be limited to those exemplary embodiments. Those skilled in the art will recognize that variations and modifications can be made without departing from the true scope of the invention as defined by the claims. Accordingly, it is intended to embrace all such changes and modifications as fall within the scope of the appended claims and their equivalents.

1 is a cross-sectional view through a message sign according to a first embodiment of the invention including a hollow light guide. FIG. 2 is an enlarged view of a portion of a message sign, surrounded by 1A and indicated in FIG. 1B is an alternative embodiment of FIG. 1A. FIG. 6 is a cross-sectional view through a message sign according to a second embodiment of the invention including a solid light guide. FIG. 3 is an enlarged view of a portion of a message sign, surrounded by 2A in FIG. 2 is a photograph of the front side of a message sign according to the present invention. 6 is a graph showing the dependence of the brightness of a message sign according to the present invention on the distance from the viewer to the sign.

Claims (13)

A light emitting device;
A translucent retroreflective film arranged to be illuminated by the light emitting device;
A lighting message sign comprising a sign, wherein the sign includes an active portion disposed in front of the translucent retroreflective film and configured to at least dynamically display variable information; Lighting message sign.   The sign of claim 1, wherein the light emitting device includes a light source and a light guide having opposing main front and back surfaces.   3. A sign according to claim 2, further comprising a back reflector disposed on the back of the light guide, wherein the back reflector is preferably a diffuse reflector, specular reflector or scattering reflector.   The light guide is a hollow light guide including a cavity having the main front surface and the main back surface, the translucent retroreflective film is disposed on at least a part of the front surface, and the back reflector is at least one of the back surfaces. The sign according to claim 2 or 3, which is arranged in a part.   5. A sign according to claim 4, wherein the light source is arranged inside the cavity, preferably centered with respect to the vertical and / or horizontal dimensions of the front surface of the cavity.   The sign according to claim 2 or 3, wherein the light guide is a solid light guide.   The light guide has a side surface disposed between the main front surface and the main back surface, and the light source illuminates the solid light guide at least one of the side surfaces of the solid light guide. The sign according to claim 6, which is arranged along at least a part of the two.   8. A sign as claimed in any one of claims 2 to 7, wherein the light source comprises a plurality of light emitting elements, e.g. arranged in rows or arrays.   9. A sign as claimed in any one of the preceding claims, wherein the light emitting device is a self-emitting light source, for example based on IEL technology or OLED technology.   10. A sign as claimed in any one of the preceding claims, wherein the marking further comprises a passive part configured to display invariant information.   11. A sign according to any one of the preceding claims, wherein the active part of the sign comprises an electronically controlled shutter system, preferably a dichroic LCD type system and / or a twisted liquid crystal system.   A method for displaying alphanumeric and / or graphic information using the indicator according to any of claims 1-11.   The method according to claim 12, wherein variable information for guiding traffic is dynamically displayed.

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