Abstract:
A data display device including a light-guide element made of an optically transparent material having at least two polished surfaces faced to one another, whereby at least one surface contains at least one gravure forming a diffuse-reflective character, and a light source arranged close to the light-guide element to illuminate said character.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a data display device including a light-guide element made of an optically transparent material having at least two polished surfaces faced to one another, whereby at least one surface contains at least one gravure forming a diffuse-reflective character, and a light source arranged close to the light-guide element to illuminate said character. 
     2. Description of the Prior Art 
     This invention is in the class of illumination engineering as well as in the class of advertising-information technologies. The claimed device may find its application in architecture as interior lamps doubling for functions of decorative luminaries. 
     The principle of action of the claimed device is based on well-known laws of geometric optics. Among these laws are:
     1) the law of conductivity of light beams in an optically transparent media having a refractive index n 1 &gt;1.0, these media being in contact with-another medium having a refractive index n 2 , with n 1 &gt;n 2 , for example, air (n 2 =1.0);   2) the law of diffuse reflection of light beams from local deformations of polished surfaces.   

     Due to the condition n 1 &gt;n 2  and owing to the polished reflecting surface, light beams do not escape the light-guide media if the condition of a limit angle of complete internal reflection is met (N. S. Kapany. Fiber Optics. Principles and Applications. Academic Press. N.Y. 1967). 
     What makes the claimed device the issue of the day is a new field of its application different from advertising-information purposes, by virtue of a fuller use of potentialities inherent in light-guide properties of optically transparent materials. 
     In advertising-information technologies, an extensive use is made of information screens called “Acryllights” produced by many advertising companies. All known “Acryllights” are made according to a uniform design of a device which comprises a light-guide element made of an optically transparent material having polished flat surfaces in the form of a light-guide plate (of a laminar rectangular shape), one of the surfaces being furnished with a set of engraved characters illuminated laterally through a polished surface by means of a light source. A principal drawback of the known device lies in its structural imperfection as dictated by a traditional approach to an information screen thought of as a plane. Such an approach comes into an apparent conflict with laws of light conductivity. These laws endow a light-guide element with “freedom of choosing any shape other than a rectilinear one” providing that the condition n 1 &gt;n 2  and the condition of full internal reflection are met. Another drawback of the device known from the art is associated with the use of luminescent light sources in “Acryllights”, above all in the form of tubes that are matched in length to the size of the light-guide plate. Diameters of the tube luminescent light sources exceed the thickness of the light-guide element, so the effectiveness of the lighting of diffuse-reflecting characters is low. Also, the size of luminescent light sources prevents some light-guide elements from being used in one unit. 
     The object of the invention is to procure a device for displaying data with enhanced visualization possibilities in respect to a data display device known in the art. 
     SUMMARY OF THE INVENTION 
     The above object is achieved by a data display device as mentioned above, characterized in that the device also includes: at least one additional light-guide element made of an optically transparent material having at least two polished surfaces faced to one another, whereby at least one surface contains at least one gravure forming a diffuse-reflective character, and at least one additional light source arranged to illuminate said diffuse-reflective character, whereby said light-guide elements being mounted at a distance one from each another such that the minimum distance between the guide-elements exceeds the red-light wavelength and each light source is being optically isolated from each another. Essential for the claimed device are the characterizing features namely introduction of extra light-guide elements conforming to the existing light-guide element and having (air) gaps between them, in combination with the use of light sources—preferably point light sources such as Light Emitting Diodes (LED&#39;s) and lasers—united in light-isolated groups according to the number of light-guide elements. So, the feature of conformity (similarity) of two and more light-guide elements generally dictates the use of curvilinear shapes within a single design. The presence of an air gap between light-guide elements guarantees a minor reflection of light-beams from the polished surfaces. (N. S. Kapany, Fiber Optics, Principles and Applications, Academic Press. N.Y. 1967) With curvilinear elements as well as with rectilinear elements, point light sources ensure highly effective illumination and provide a possibility to follow a curvilinear outline of any number of light-guide elements in a unit. Light isolation of groups of point light sources makes it possible to illuminate each light-guide element separately. Using the claimed device for demonstration of information makes it possible to achieve a benefit consisting in expansion of the device applications, in increasing the information capacity, in reducing power input and in adding to the failure operating time through the improvement of the device. There is a casual relationship between the benefit of the invention and distinguishing features of the claimed device as the feature of introduction of additional light-guide elements in combination with the feature of introduction of conforming light-guide elements ensures expansion of the device applications and provides an increase in information capacity of the claimed device due to making additional diffuse-reflective characters on the surfaces. 
     A mentioned above consists each light source of multiple point light sources. Small-sized point light sources used for illumination of diffuse-reflective characters make it possible to improve effectiveness of filling-in the internal volume of a light-guide element with light beams. Due to their size some few point light sources may be placed on small areas thus providing multiprogramming modes of their “on-off” action, which is effected in the device by means of the electronic programmed control unit. Accordingly, the distinguishing features of the claimed device are necessary and sufficient to achieve the benefit of the invention, with the said features being under legal protection in full measure. 
     Light-guide elements on the point source side are made curvilinear, with the curvature radius being no more than the thickness of the light-guide element. This is an additional feature specifying the structural possibility to widen the angle of the radiation directivity diagram of the point light sources. This feature is aimed at improving the effectiveness in illuminating a light-guide element while using highly intensive narrow-beam light sources. Restriction to the curvature radius is a structural parameter. All the light-guide elements of the claimed device are made curvilinear. This is an additional feature specifying conformity (similarity) of light-guide elements that may be united in a single light-guide unit. 
     In an embodiment of the invention the device comprises an electronic programmed unit electrically connected to said point light sources to control said point light sources. An advantage of the electronic programmed is that data can be displayed in numerous ways. For example, the data can be displayed in a dynamic way and/or in an three-dimensional way by switching specific point light sources on or off during specific times. 
     In another embodiment of the invention the point light sources in the form of solid-state semi-conductor light diodes (LED) are arranged in groups according to the number of light-guide elements relates to an essential distinguishing feature—“a point light source”. A doubtless advantage of light diodes, alongside with their small size, is their high intensity of radiation and various spectra of glow plus high reliability. 
     The light produced by said at least one light source is preferably guided by multiple fiber-optical light guides to the corresponding light-guide element. In an specific embodiment a rotatable (multicolored) light filter can be placed between said light source and said fiber-optical light guides. The light that is directed to the light-guide element can be considered as a multiplicity of individual point light sources. This characteristic specifies an essential feature of the presence of point light sources, which makes it possible to tackle some problems associated with an increase in intensity of illumination of diffuse-reflective characters in the device, where as changing the spectral composition of radiation is effected by means of the said set of moveable light filters collected in a colourgramme. Most light diodes designed for illumination are highly intensive and their angle of the directivity diagram is not over 45°. With such light diodes produced by the Hewlett Packard Co. (Electronic components ‘Hewlett Packard’. Concise catalogue. 1999. P. 3–7), a problem may arise in connection with redistribution of light radiation in favor of mirror-reflective components. For this problem to be solved, the surface of light-guide elements on the side of the point light sources is made oblique at an angle
 
φ=90°± A  
         where A is an angular parameter selected out of the interval of values 0°≦A≦U/2,   where U is an angle of the directivity diagram of point light sources.       

     Due to this declinations, the majority of axial beams of a light diode strike upon the polished side of a light-guide element at an angle equal to or lesser than the angle Uc. The angle Uc is the angle of full internal reflection at the interface of an optical medium having a gradient of refraction indices. Based on the theory of geometric optics (N. S. Kapany, Fiber Optics, Principles and Applications, Academic Press, N.Y. 1967) the limit beam angle of full internal reflection towards the axis of the light-guide element section is defined as
 
 Uc =arcsin 1 −n   1   2   /n   2   2  
         where Uc is a critical angle of full internal reflection;   n 2  is the refractive index of an optically transparent material of the light-guide element;   n 1  is the refractive index of a medium that is in contact with a light-guide element, for air n 1 =1.0.       

     Preferably an additional light source, more preferably at least one point light source, is provided for front illumination, are valid for a device having an additional light source for front-end illumination of diffuse-reflective characters. These features are used in case when it is necessary, constantly or on a program, to single out one or several characters by means of light, e.g. logotypes of a trademark. 
     Along-with the above-mentioned features, light-guide properties of optical materials can ensure illumination from two or more sides. However, this can be accompanied with undesirable optical effects of additive combination of light flows; or else some characters, on a program of illumination, should be imparted with an effect of a dynamically changeable altitude. In order for this problem to be solved, some features should be introduced to ensure light isolation of illuminated zones of diffuse-reflective characters. Therefore is at least one of light-guide element on the side of diffuse-reflective characters furnished with grooves positioned substantially across light beams issuing from the (point) light sources. The grooves are providing a ‘shade’ after turning-on an appropriate group of light diodes, thus screening the zone of diffuse-reflective characters. 
     Expansion of the claimed device applications suggests a non-traditional approach to shapes of light-guide elements themselves. So, in an embodiment of the invention at least one light-guide element is made in the form of a polygonal prism. This provides a possibility to create a device in the form of a piece of art doubling for functions of demonstration and illumination. In a specific embodiment of the device the light-guide element is made in the form of a set of trigonal prisms rotatable synchronously around the geometric axis relative to the (point) light sources. This geometry enlarges the volume of information-of the device at least three-fold by placing the information onto three surfaces composed of two or more rotatable prisms. The said distinguishing features make it possible to create such lighting devices as ‘prismatrons’. 
     A side of the light-guide, opposite to a side of the light-guide element being provided with the gravure, is provided with a polished mirror reflective surface. For example, diffuse reflections appear on ground portions of the said surfaces. For such a diffuse reflection to be implemented in the claimed device, the characters are preferably furnished with ground surfaces and the opposite side of a light-guide element is furnished with a mirror reflective covering. The combination of features defined by the presence of the ground characters and the mirror reflective covering serves to achieve uniformity of exposure of ground portions of the light-guide element. To achieve a uniform illumination of color slides with white light, one of the surface of one light guide elements is made fully ground. The light-guide element is in a preferred embodiment furnished with a transparent film on the surface which is opposite to the ground surface, such that the transparent film is arranged between at least two light-guide elements. This light-guide element can also be furnished with an additional group of light diodes which radiate additive white light, for example LEDs of HLMP-CW 15 or HLMP-CW 30 types from “Hewlett Packard” Corp. 
     In an embodiment of the invention the device has light-guide elements of laminated shape mounted a gap apart and opposite each other. The device is provided with an additional removable light-guide elements made of an optically transparent material in the form of parallelepipeds with polished sides where there are provided diffuse-reflective characters. The above parallelepipeds are mounted in the said gap so that they are in optical contact to light-guide plates. The combination of the above-mentioned distinguishing features is sufficient for embodiment of new designs of advertising-information screens displaying rapidly changeable information. To do so, it is sufficient to have an appropriate set of removable elements furnished with engraved characters. Considering that each optically transparent parallelepiped has four planes for appropriate information to be placed on them, the above-mentioned features enlarge informative capacity of the device by a factor of 2 or 4. 
     In the center of at least one light-guide elements are made holes having cylindrical polished internal surfaces which are optically coupled with an additional set of light diodes. 
     In a last embodiment the electronic programmed unit illuminates the point light sources sequentially. By such control data can be displayed in a dynamic and/or more dimensional way. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For further details of the invention, reference may be made to the accompanying non-limitative drawings wherein: 
       FIGS.  1 – 9 —embodiments of the claimed device; 
       FIGS.  10 – 12 —cross-sections of a light-guide plate with light diodes; 
       FIGS.  13 – 20 —a design of the claimed device with three light-guide elements; 
       FIGS.  21 – 23 —a design of the claimed device with fiber-glass light conductors; 
       FIGS.  24 – 25 —an embodiment of a light-guide plate with light isolation (shielding); 
       FIGS.  26 – 27 —an embodiment of the light-guide element with diffuse-reflective characters dynamically lighted—“the effect of motion”; 
       FIGS.  28 – 29 —a design of the data display device with additional front-end illumination of diffuse-reflective characters; 
       FIGS.  30 – 35 —embodiments of the data display device with ground and combined diffuse-reflective characters; 
       FIG.  36 —an embodiment of the data display device to illuminate slides; 
       FIG.  37 —an embodiment of the light-guide element in the form of a polygonal prism; 
       FIG.  38 —a design of the device in the form of a set of prisms; 
       FIGS.  39 – 43 —a design of the data display device in the form of a decorative luminary; 
       FIGS.  44 – 45 —a cross-section of the light-guide plate with a variable thickness of engraved diffuse-reflective characters; 
       FIGS.  46 – 47 —a design of the data display device in the form of a clock; 
       FIGS.  48 – 49 —a design of the data display device with removable light-guide elements; and 
       FIGS.  50 – 51 —a design of the data display device having illumination from inside. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a design of the data display device comprising at least two light-guide elements  1 ,  2  having polished surfaces. For an optical material, acrylic “organic” glass may be used. Engraved on the wide surface of the light-guide element  1 , on one or two sides, there are provided engraved diffuse-reflective characters (signs, litters, pictures)  3  to form in the aggregate an information unit, e.g. a logotype of a trade-mark. The wide polished surface of the light-guide element  2  is also furnished with diffuse-reflective characters located in the zone  4 . Structurally, the device in  FIGS. 1 and 2  is provided with light-guide plates  1  and  2  of a rectangular shape, with point radiators being mounted on their narrow polished sides to illuminate the characters  3  while the zone  4  being furnished with characters on the plates  1  and  2 , respectively. As is seen in  FIGS. 1 and 2 , the point radiators are provided with electric power-supply units to choose modes of ‘on-off’ action of the above radiators under electronic programs. For the point light sources, the device may use solid-state semiconductor diodes arranged in groups  5  and  6 . Electronic programmed unit  7  controls the action of the groups of light diodes  5  and  6 , respectively. An optically isolating plate  9  is mounted between the groups of light diodes  5  and  6 . In the gap  8  (L&gt;0.6 micrometer) between the light-guide elements  1  and  2  there is air having the refraction index n 1 =1. The elements  5 ,  6 ,  7 ,  8  are housed inside protective casings  10 . In manufacturing the data display device a problem arises at times as to redistribution of light flowing from light diodes  5  and  6  to enhance mirror-reflective constituents. In this situation the light-guide elements  1  and  2  that are in optical contact with the light diodes  5  and  6  can be provided a tilt at an angle φ, as shown in  FIG. 3 . 
     Light-guide properties of optically transparent materials enable one to make the light-guide elements  1  and  2  curvilinear, as is shown in  FIGS. 4 and 5 . For this design of the device, the above-mentioned elements  1  and  2  are made in the form of two coaxial cylinders that are inserted into each other and housed in the casing  10 . The characters  3  and  4  are made on cylindrical surfaces of the light-guide elements  1  and  2 . The bases of the cylinders of the elements  1  and  2  are illuminated by means of the light diodes  5  and  6  by means of the electronic programmed units  7 , as is shown in  FIG. 6 . Between the two light-guides elements  1  and  2  are the air gap  9  (ΔL&gt;&gt;0.6 micrometer). 
       FIGS. 7 to 9  show an embodiment of the data display device with light-guide elements  1  and  2  in the form of plates having in their front-end surface a shape different from a rectangular shape ( FIG. 7 ). In the above design a general problem associated with redistribution of light flow from the light diodes  5  and  6  is solved by forming a curvilinear outline of the narrow surface of the elements  1  and  2  ( FIGS. 8 to 9 ), with the curvature radius R being less than the thickness of the said elements. 
     In that event the curvilinear surface fulfils the role of a cylindrical diffusing lens to enlarge the angle U of the directivity diagram of the light diodes  5 ,  6  and to enhance the mirror-reflective constituent in their radiation. It especially becomes a live issue when using highly intensive light diodes having the directivity diagram with the angle U up to 20°–45°. 
     Let us consider cross-sections of the light-guide plates  1  shown in  FIGS. 10 to 12 . Light rays  11  from the light diode  5  undergo a number of mirror reflections from the polished surface of the plate  1 . This takes place in view of the presence of a gradient in the refraction factor at the interface of the two optical media having different refraction factors n 1 &gt;n 2 . In case there are no deformations on polished surfaces of the plate  1 , the light ray  11 , after multiple mirror reflections, will go out through the opposite face. If the surface of the plate is furnished with an engraved character  3  the principle of mirror reflection of the ray  11  is violated at this place with the ray  12  being diffusely reflected from engraved portions of the character  3 . In  FIGS. 10 to 12  these rays  12  are shown with thick arrows. Portions of the polished surface may be also referred to as belonging to diffuse-reflective deformations of polished surfaces of the element  1 . 
       FIG. 13  shows a structural embodiment of the data display device comprising three light-guide elements  1 ,  2  and  13 , two of which are made in the form of optical lens having flat-convex surfaces (the elements  2  and  13 ), while the element  1  has flat surfaces mated to surfaces of the elements  2  and  13 . As is evident from  FIG. 14 , diffuse-reflective characters  3 ,  4  and  14  are made on surfaces of all the light-conducing elements  1 ,  2  and  13  to form in the aggregate a united informative composition. The light-guide element  1  with the characters  3  shown in  FIGS. 15 and 16  may be made in the form of two plates (for example  1  and  1 *) having an air gap  9  between them. The element  1  ( 1 *) have a flat surface mated to two rows of the light diodes  5  that are electrically connected to the programmed control unit  7 . With reference to  FIGS. 17 and 18 , the additional light-guide “lens”  13  having a character-containing zone  14  placed on a flat surface  15  is furnished with a frosting convex surface  16  and a flat surface (at an angle φ) mated to a set of light diodes  17 . Light diodes  17  are operated from an additional power-supply unit  18 . The light-guide element  2  ( FIGS. 19 to 20 ) has a convex surface  19  and a flat surface  20  skewed at an angle φ and mated to a set of the light diodes  6 . The light diodes are energized from the unit  7  on an electronic program to control their on-off action. As an assembly, the data display device ( FIGS. 13–14 ) has two functions—demonstration of information and decorative illumination. 
     For light sources to illuminate the light-guide elements, use may be made in the device also of other point light sources. So, the device shown in  FIGS. 21 to 23  incorporates a set of light-guide elements  21  made of light conductors, e.g. glass-fiber or plastic-fiber. On one side, the edges of the light-guide elements  21  are mated to the surface of the light-guide plate  1  containing diffuse-reflective characters  3  where as the opposite edges are collected in a cable  22  with its edge being mounted in the immediate vicinity of a rotating color-programmed disc  23  lighted with an independent illuminator  24 . The color-programmed disc  23  is made of a set of light filters  25  ( FIG. 22 ). Advantages of this illumination are its high specific power of lighting and the small size to allow for arranging output edges  21  in three rows ( FIG. 23 ). 
     Light-guide properties of the light-guide elements  1 ,  2  and  13  carry considerable potentialities for designing a great diversity of various devices. For instance, when illuminating the diffuse-reflective characters on one or more sides a demand arises for ensuring light isolation of different portions of information: In tackling this problem a possibility appears to have separate illumination of-at least two informative zones.  FIGS. 24 and 25  show a design of the light-guide element  1  with diffuse-reflective characters located on one of flat surfaces. Two rows of light diodes  5  are placed at the top and at the bottom to illuminate the left and the right informative zones according to the embodiment as shown in  FIG. 24 . 
     For the above informative zones to be isolated, there are provided two engraved grooves  26 – 27  and  27 – 26  as deep as no more than one-half the thickness of the plate  1 . The above grooves  26  and  27  separate the informative “globe” zone from the “trade character” zone to ensure separate illumination of these zones.  FIGS. 26 and 27  show a structural embodiment of the data display device with dynamic illumination. This device has a rectangular plate  1  containing two informative zones with characters  28 —a static zone with characters  3  and a dynamic zone—separated with light-isolating grooves  26  and  27 . There is provided a set of light diodes  29  and a unit  30  to effect programmed electronic control over on-off action of the light diodes. When the light diodes are energized in succession the characters  28  will be illuminated in succession too to produce the effect of motion. 
     The device allows also for the use of additional sources of illumination which can directly illuminate any character or symbol in a front-end manner. So,  FIGS. 28 and 29  show such a device that is provided with a matrix of light diodes  31  mounted on a board  32  that is in a front-end position relative to the trade character  3 . An electronic programmed power-supply unit  33  provides the light diodes  31  with varied modes of front-end illumination. 
     Of interest may be a design of the device shown in  FIGS. 30 and 31 . It comprises light-guide plates  1  and  2  in the form of discs, with the disc  1  having a facet  34  to form a reflecting surface for radiation issued from light diodes  5 . Applied to the facet  34  and to the rear surface of the disc  1  is a mirror covering  35 . The other surface of the disc  1  is furnished with characters  37  made, by means of polishing a portion of a surface  36 , in the form of anti-reflective polished symbols, e.g. a trade mark. The disc  2 , in reference to the disc  1 , fulfils the high-priority protective role, but in some cases this disc may be also provided with independent illumination. The two discs  1  and  2  together with the set of light diodes  5  are housed in a protective casing  38 . Such a device may find its application as a glass decorative table board. 
     The principle of light conductivity combined with diffuse reflection may be valid to design flat luminaries that are meant for advertising information.  FIGS. 33 to 35  show two designs of such devices, one of which being made in the form of a disc ( FIGS. 32–33 ) and the other in the form of a rectangle ( FIGS. 34–35 ) with combination of diffuse reflecting zones and characters  3  (made by engraving) and  37  (made by polishing). The characters  3  are made on a portion of the polished surface of the light-polishing element  1  surrounded by a polished surface  36  containing a zone  37  of ‘anti-reflective polished characters’. 
     Due to a mirror reflecting layer  38 – 37  the frosting surface  36  is set off in the form of a lighting background to form appropriate characters in the zone  37  at borders of the polished portions. The light diodes  5  mounted on a skew facet  34  illuminate the mirror covering  35  and a frosting background  36  as well as diffuse-reflective characters  3 . The light diodes  5  are switched by the electronic programmed unit  7 . 
     The data display device shown in  FIG. 36  is made in the form of two light-guide plates  1 , 2  united in a single assembly. The diffuse-reflecting characters  3  are applied to the surface of the element  1 . Fixed in the gap between the elements  1  and  2  is a transparent film  39 . The surface  36  of the plate  2  is made filly ground, the other surfaces being polished. For the plate  2  and the film  39  to be illuminated, use is made of light diodes  40  irradiating white light. Intensity of irradiation of the light diodes  40  is regulated by the electronic programmed unit  41 . 
     The data display device shown in  FIG. 37  is made in the form of two light-guide elements  1  and  2 , one of which having the shape of a monolithic polygonal prism, e.g. a hexahedron. The element  2  is made in the form of a curvilinear prismatic element with the frosting surface  36 . Mating surfaces of the elements  1  and  2  are polished. One or two of these surfaces may contain characters  3  which, when illuminated by light diodes  31  in a front-end manner, are projected onto the frosting surface  36 . The rest of the characters placed in the zones  3  are made by engraving and, when illuminated by a set of the light diodes  5 , are reflected in a diffuse manner. All the elements are housed in the casing  10 . 
       FIG. 38  shows the evolution of the concept of a polygonal prism as a light-guide element. In a device like a “prismatron”, light-guide prisms are made hollow inside to form an equilateral triangle in the cross-section. Prisms, two or more in number, are assembled from light-guide rectangular plates  1 ,  2  and  13  which contain sets of characters  3  placed on all side surfaces thereof. In reference to their geometric axes  42 , the prisms are mounted rotatable synchronously at 120°. The rotation is effected by means of kinematic links  43 . According to the number of rotatable prisms ( 1 ,  2 ,  13 ), the sets of light diodes  5  are housed in boxes  44  which also contain the power-supply unit, motors for rotation and other equipment necessary to control a “prismatron”. The full informative field is formed by means of uniting the characters  3  placed accordingly on the three faces of the prisms when they are combined into one plane after rotation. 
       FIGS. 39 to 43  show a principal design of the data display device made in the form of a small-sized decorative luminary. This luminary consists of two light-guide elements  1  and  2  united into one unit. A set of characters  3  is placed on the surface of a plate  1  ( FIGS. 39 ,  40 ) and characters  4  on the surface of a plate  2  ( FIG. 41 ). In doing so, co-ordinates X 1  and X 2  of base points of the above characters  3  and  4  must be brought into coincidence. The surfaces of the light-guide element  2  are also furnished with two light-isolating grooves  26  and  27 . The element  1  is illuminated with a set of light diodes  5  placed in sphere-like recessions  45  with the radius R 1  to widen the angle U of the radiation directivity diagram of the above light diodes  5 . The light-guide element  2  is illuminated by a set of light diodes  6  and their interface with the element  2  is made skew in order to re-distribute light radiation. The surface  36  of the element  1  is made in the form of a frosting surface while the surface  38  is made in the form of a mirror reflective surface. The set of light diodes  29  is mated to the element  2  on the side and illuminates the character  4  ( FIG. 41 ) where as the light isolation (grooves  26 ,  27 ) presents an objection to mixing light rays issued from the light diodes  6  and light diodes  29 . 
     To solve the problem of how to ensure a uniform exposure of diffuse-reflective characters placed on big-sized light-guide elements, the characters  3  shown in  FIGS. 44 and 45  are provided with a variable thickness of engraved character-generating lines  46 . Degradation of illumination of the characters  3  ( 46 ) is first of all due to losses during multiple mirror reflections. As a consequence, the lines  46  of a variable thickness h enlarge the area of exposure to ensure uniformity of integral illumination of the entire character  3  along its whole length l. 
       FIGS. 46 and 47  show a draft embodiment of the data display device in the form of a clock. This device comprises four light-guide discs  1 ,  2 ,  13  and  47  connected to four appropriate groups of light diodes  5 ,  6 ,  17  and  29 . Here, the surfaces of the discs  1 ,  2 ,  13  and  47  are provided with characters  3  (an analogue to ‘an hour of the day’), characters  4  (an analogue to ‘minutes’), moveable characters  25  (an analogue to ‘seconds’) and characters  46  (an analogue to ‘the first or the second half of the day’ or to a firm&#39;s trade character). Discs  1 ,  2  and  13  have circularly positioned facets  34  to be illuminated by light diodes  5 ,  6  and  29 . A mirror covering  38  is applied to the surface of the light-guide disc  1 . All the elements of the device are housed in the casing  10 . 
       FIGS. 48 and 49  show the data display device in the form of an optically transparent duct made of light-guide plates  1 ,  2  and two side-members  47 . Inside the duct are light-guide elements  46  in the form of parallelepipeds. Beneath the duct, the elements  1 ,  2  and  47  are mated to light diodes  5  in the casing  10 . All light-guide parallelepipeds  13  are removable and allow for periodic renewal of information. From above, the device is provided with a protective removable housing  49 . 
     The data display device having central illumination is shown in  FIGS. 50–51 . The light-guide elements  1  and  2  having diffuse-reflecting characters  3  and  4  are provided with two coaxial holes  50 – 51  in the center. A set of light-diodes  52  is placed inside the holes  50 ,  51 . The holes  50 ,  51  are covered with plugs  53 ,  54  on both sides. 
     Such features as light-guide elements of new shapes different from rectilinear ones, conformity of these elements and the use of point light sources ensure the creation of data display devices that possess dynamic modes of information delivery.