Patent Publication Number: US-11650364-B2

Title: Light distribution element

Description:
FIELD OF THE INVENTION 
     Generally, the present invention relates to light-transmissive substrate optics. In particular, the present invention concerns a light distribution element, such as a lightguide, for example, with improved illumination uniformity. 
     BACKGROUND 
     Typical light distribution element (e.g. a lightguide element) is based on provision of optical patterns, which control light extraction, outcoupling and uniformity distribution. Additionally, almost all lightguide elements utilize brightness enhancement films provided as separate optical layers, which films/layers operate with already outcoupled light and/or incident light with an angle of incidence exceeding the critical angle, in order to control light distribution angles. Due to provision of separate layers, optical management in the final design is always challenging, and multiple designs need to be completed in order to achieve desired performance. 
     Illumination systems can be defined for transmissive, lightguide and reflective elements. Basic illumination distribution and uniformity can be controlled with optical structures. Another option is to utilize light reflecting layers, which provide local control over light passing through the layer. Some prior art solutions are based on low refractive index coating or cladding, having the refractive index (R i ) values lower than that in surrounding media. Incident light, arriving at angles of incidence larger than the critical angle relative to surface normal, undergoes total internal reflection and does not penetrate through such low R i  layer. Prior art is also teaches the solutions with voids or apertures in a substrate layer or a cladding, in which the refractive index is the same or higher than a surrounding medium, such as a lightguide medium. Those voids or apertures allow light rays to pass through the coating or cladding layer. Such types of layers are based on specific low R i  materials, which require more know-how and advanced processing- and production technologies. In most instances, costs for these materials is a critical factor, which limits utilization thereof in high volume production. 
     In the U.S. Pat. No. 10,139,550 (Thompson et al) a non-continuous cladding layer is disclosed with discrete voids, wherein another material has been utilized to fill those voids in order to achieve light passages to a second medium. Also the document US 2009/0086466 (Sugita et al) teaches a non-continuous cladding layer with filled voids. The document WO 2019/026865 (Sugino et al) discloses a discreet, non-continuous cladding layer forming a pattern with low R i , in which the refractive index has been modified and managed such, as to form light passages from a first medium to a second medium. All mentioned documents teach low R i  coating- or cladding layers that produce total internal reflection (TIR). 
     SUMMARY OF THE INVENTION 
     An objective of the present invention is to at least alleviate each of the problems arising from the limitations and disadvantages of the related art. The objective is achieved by various embodiments of a light distribution element, according to what is defined in the independent claim  1 . 
     In embodiment, a light distribution element is provided, comprising:
         a lightguide medium configured for light propagation,   a first functional layer configured as an optical filter layer and disposed on an at least one surface of the lightguide medium, and   a second functional layer comprising an at least one optically functional feature pattern,   wherein the first functional layer and the second functional layer are rendered with an at least one optical function related to incident light and, in particular, to light incident at an angle equal and/or below the critical angle, and   wherein the first functional layer is further configured as an internal layer with a light uniformity control function, and wherein said layer comprises a number of optical contact areas configured to transmit light rays therethrough, optionally, to the second functional layer and from said second functional layer.       

     The light distribution element ( 100 ) of claim  1 , wherein the first functional layer ( 1 ) is integrated between the second functional layer ( 10 ) and the lightguide medium ( 101 ). 
     In said light distribution element, the first functional layer can be configured as a cladding, a coating, or a film. 
     In said light distribution element, the first functional layer may be rendered with at least a light transmission function. 
     In embodiment, the first functional layer is at least partly formed of the substrate material having a refractive index substantially equal to or higher than the refractive index of the material constituting the lightguide medium and, optionally, the refractive index of material constituting the second functional layer. 
     In alternative embodiment, the first functional layer is at least partly formed of a substrate material having the refractive index lower than the refractive index of material constituting the second functional layer and, optionally, lower than the refractive index of material constituting the lightguide medium. 
     In embodiment, the first functional layer is configured as a total internal reflection (TIR) layer structure. 
     In embodiment, the optical contact areas are established in said first functional layer by a number of apertures formed in a substrate material. In embodiments, the apertures formed in the substrate material are through-apertures. 
     In embodiment, said apertures form enclosed voids upon being integrated within the light distribution element. In embodiments, said enclosed voids are filled with gaseous medium, such as air, or with vacuum 
     In embodiment, the first functional element is configured as a substrate material with a number of apertures integrated into a layer of essentially optically transparent material. In embodiments, said essentially optically transparent material is an adhesive material. 
     In some embodiment, the optical contact areas are established in said first functional layer by a discrete pattern or patterns formed by the substrate material between the apertures. 
     In embodiment, the optical contact area is provided as any one of: a line, a dot, a geometric shape, a cross, a grid, or as a pattern comprising any combination thereof. 
     In embodiment, the optical contact areas are arranged into an at least one array within an at least one predetermined location at said first functional layer or into an at least one array extending along and/or across an entire surface of said first functional layer. 
     In embodiment, the first functional layer comprises at least two sublayers. In embodiments, each said sublayer comprises a number of optical contacts, configured to transmit light rays therethrough, wherein the optical contacts are formed by a plurality of apertures and/or by a discrete pattern or patterns formed by the substrate material between said apertures. 
     In an aspect, a light distribution element is further provided according to what is defined in the independent claim  19 . 
     In embodiment, the light distribution element comprises:
         a lightguide medium configured for light propagation,   a first functional layer configured as an optical filter layer and disposed on an at least one surface of the lightguide medium, and   a second functional layer comprising an at least one optically functional feature pattern,   wherein the first functional layer and the second functional layer are rendered with an at least one optical function related to incident light and, in particular, to light incident at an angle equal and/or below the critical angle, and   wherein the first functional layer is further configured as an internal layer with a light uniformity control function, said layer optionally comprising a number of enclosed voids formed upon integration of the first functional layer within the light distribution element, wherein said voids are filled with a gaseous medium or vacuum.       

     In embodiment, mentioned voids are filled with air. 
     In embodiment, the first functional layer is integrated between the second functional layer and the lightguide medium. 
     In embodiment, the enclosed voids are established by a number of apertures provided in a substrate, upon integration of said substrate with the apertures into the light distribution element. 
     In embodiment, said first functional layer comprises a plurality of optical contacts, configured to transmit light rays therethrough, optionally, to the second function layer and from the second functional layer. In embodiment, the optical contacts are formed in said first functional layer by a discrete pattern or patterns formed by the substrate material between the apertures. 
     In an aspect, a light distribution element is provided according to what is defined in the independent claim  32 . 
     In embodiment the light distribution element comprises:
         a lightguide medium configured for light propagation,   a first functional layer configured as an optical filter layer and disposed on an at least one surface of the lightguide medium, and   a second functional layer comprising an at least one optically functional feature pattern,   wherein the first functional layer and the second functional layer are rendered with an at least one optical function related to incident light and, in particular, to light incident at an angle equal and/or below the critical angle, and   wherein the first functional layer is further configured as an internal layer with a light uniformity control function.       

     In embodiment, the first functional layer is provided as a continuous, uniform layer. 
     In embodiment, the first functional layer is formed, at least partly, by a substrate material. 
     In embodiment, the first functional layer consists of or comprises an adhesive material, preferably, an optically clear adhesive material. 
     In embodiment, the first functional layer is formed without the adhesive material. 
     In embodiment, the first functional layer comprises at least two sublayers, wherein the first sublayer is formed of the substrate material and wherein said second sublayer is formed of the adhesive material. 
     In embodiment, the lightguide medium further comprises a number of prominent, optically functional relief profiles, optionally integrated with the adhesive material. 
     In embodiment, the second functional layer is configured as an optically functional layer rendered with at least a light extraction function and a light outcoupling function. 
     In embodiment, the at least one optically functional feature pattern of the second functional layer is formed in a light-transmitting carrier medium by a plurality of features provided as optically functional cavities. In embodiment, in said at least one optically functional feature pattern, the optically functional cavities are open-top features. 
     In embodiment, the at least one optically functional feature pattern of the second functional layer is fully integrated and/or embedded within the light-transmitting carrier medium, whereby an embedded feature pattern is established in the light-transmitting carrier medium by a laminate structure formed by an entirely flat, planar layer of the carrier medium arranged against a patterned layer of the carrier medium and a plurality of optically functional internal cavities is formed at an interface between the layers. 
     In embodiment, the optical function or functions of the second functional layer is/are established by an at least one of the: dimensions, shape, periodicity and disposition of the cavities within the at least one optically functional feature pattern. 
     In embodiment, the cavities are filled with gaseous medium, such as air. 
     In embodiment, the at least one optically functional feature pattern comprises a plurality of discrete feature profiles. 
     In embodiment, the at least one optically functional feature pattern comprises a plurality of at least partly continuous feature profiles provided as a symmetric pattern structure or as an asymmetric pattern structure. 
     In embodiment, the at least one optically functional feature pattern is a hybrid pattern comprising a plurality of discrete feature profiles or a plurality of at least partly continuous feature profiles. 
     In embodiment, the optical cavity features are selected from the group consisting of: a groove, a recess, a dot, and a pixel, wherein said cavity features have crosswise profiles selected from: binary-, blazed-, slanted-, prism-, trapezoid-, hemispherical profiles, and the like, and wherein said cavity features have a lengthwise shape selected from: linear, curved, waved, sinusoid, and the like. 
     In embodiment, the lightguide medium and the second functional layer ( 10 ) are an optical polymer and/or glass. 
     In embodiment, the second functional layer is provided in the form of a laminated multi-layer structure comprising an at least one layer with integrated cavity features and/or a third functional layer, optionally configured as an open profile layer. 
     In embodiment, the light distribution element further comprises at least one light source, selected from: a Light Emitting Diode (LED), an Organic Light Emitting Diode (OLED), a laser diode, a LED bar, an OLED strip, a microchip LED strip, and a cold cathode tube. 
     In embodiment, the light distribution element is configured as a light guide, a light pipe, a light-guide film or a light-guide plate. 
     In another aspect, a process for manufacturing a light distribution element according to any previous embodiment is provided, in accordance to what is defined in the independent claim 58. 
     In embodiment, the process for manufacturing the light distribution element is provided, wherein the element comprises a lightguide medium configured for light propagation, a first functional layer configured as an optical filter layer with a plurality of discrete apertures formed in a substrate material, said first functional layer being disposed on an at least one surface of the lightguide medium, and a second functional layer, in which method the apertures are produced by an at least one method selected from the group consisting of: laser patterning, direct laser imaging, laser drilling, mask- and maskless laser or electron beam exposure, printing, machining, moulding, imprinting, embossing, micro- and nano-dispensing, dosing, direct writing, discrete laser sintering, and micro-electrical discharge machining (micro EDM). 
     In embodiment, the first functional layer and/or the second functional layer is/are produced by a roll-to-roll method or a roll-to-sheet method. 
     In embodiment, the first functional layer is produced on the lightguide medium prior to application of the second functional layer. 
     In another aspect, an optical device is provided, in accordance to what is defined in the independent claim 61. In embodiment, said optical device is configured as a frontlight illumination device or a backlight illumination device. 
     In further aspect, use the optical device, according to the previous aspect, is provided, in accordance to what is defined in the independent claim 63. 
     In still further aspect, a roll of a light distribution element is provided, according to what is defined in the independent claim 64. 
     In embodiment, the roll of the light distribution element comprises: 
     a first functional layer configured as an optical filter layer, and 
     a second functional layer comprising an at least one optically functional pattern, 
     wherein the first functional layer is rendered with a light uniformity control function. 
     In a number of embodiments, the roll the light distribution element is configured to any one of aspects according to the independent claims  1 ,  19  and  32  and according to embodiments associated therewith. 
     The utility of the present invention arises from a variety of reasons depending on each particular embodiment thereof. At first, the light distribution element provided hereby has all light management components, such as uniformity control and light extraction with controlled light distribution, integrated in a single element. Two-stage optical management is thus attained, wherein the first function is illumination uniformity control by light filtering. The second function is light extraction and outcoupling at preferred angles. 
     The inventive concept is based on an optical filter structure for the light distribution element, such as a lightguide, in which optical filter, light incident thereto at an angle exceeding the critical angle, is reflected by total internal reflection (TIR), wherein the phenomenon of TIR primarily produced at a gaseous interface (instead of that produced by the low R i  cladding). 
     The structure comprises no separate layer components, all “layers” described in the present disclosure are integrated in one element. 
     In preferred embodiment, in the light distribution element provided hereby the first and the second functions utilize light incident at an angle equal and/or below the critical angle. 
     This has a major impact for optical pattern design, which differs from that the normal brightness enhancement films. 
     Novel lightguide element can further utilize a direct outcoupling stack with a light extracting layer on the illumination side, or a function of indirect outcoupling with the light extracting layer on the bottom with a backsheet reflector. 
     In its broadest sense, the term “light filter” or “optical filter” refers to a device or a material used to change the spectral intensity distribution or the state of polarization of electromagnetic radiation incident thereupon. The filter may be involved in performing a variety of optical functions, selected from: transmission, reflection, absorption, refraction, interference, diffraction, scattering and polarization. 
     The terms “optical” and “light” are largely utilized as synonyms unless explicitly stated otherwise and refer to electromagnetic radiation within a certain portion of the electromagnetic spectrum, preferably, but not limited to, visible light. 
     In its broadest sense, the term “optical filter” or a “light filter” refers, in the present disclosure, to a device or a material used to change the spectral intensity distribution or the state of polarization of electromagnetic radiation incident thereupon. The filter may be involved in performing a variety of optical functions, selected from: transmission, reflection, absorption, refraction, interference, diffraction, scattering and polarization. 
     In its broadest sense, the terms “lightguide” or “waveguide” refer, in the present disclosure, to a device or a structure configured to transmit light therealong (such as from a light source to a light extraction surface). The definition involves any type of the lightguide, including, but not limited to a light pipe type component, a lightguide plate, a lightguide panel, and the like. 
     The term “carrier” or “carrier medium” generally refers to a flat, planar member composed of a substrate material configured for light propagation and optionally constituting a layered structure. 
     The term “element” is used in the present disclosure to indicate a part of an entity. 
     The expression “a number of” refers herein to any positive integer starting from one (1), e.g. to one, two, or three; whereas the expression “a plurality of” refers herein to any positive integer starting from two (2), e.g. to two, three, or four. 
     The terms “first” and “second” are not intended to denote any order, quantity, or importance, but rather are used to merely distinguish one element from another. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Different embodiments of the present invention will become apparent by consideration of the detailed description and accompanying drawings, wherein: 
         FIGS.  1 A and  1 B  are cross-sectional views to show a light distribution element  100  according to some embodiments of the present invention. 
         FIGS.  2 A- 2 H  schematically illustrate a manufacturing process of the light distribution element and a related film stack, according to various embodiments of the present invention. 
         FIG.  3    illustrates an exemplary embodiment of a light distribution element comprising a light extraction film with an air-cavity pattern and the same with an open top pattern. 
         FIG.  4    schematically illustrates the light distribution element  100  integrated into an advertisement illumination concept for windows, for example. 
         FIG.  5    is a perspective view of the element  100 , according to an exemplary embodiment. 
         FIG.  6    shows a number of exemplary optical contact patterns for a first functional layer of the light distribution element. 
         FIGS.  7 A and  7 B  schematically illustrate the effect of structural variations within the light distribution element  100  on light propagation and the size of local illumination area. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Detailed embodiments of the present invention are disclosed herein with the reference to accompanying drawings. The same reference characters are used throughout the drawings to refer to same members. Following citations are used for the members:
       100 —a light distribution element;     101 —an optically transparent substrate (lightguide medium configured for light propagation);     1 —a first functional layer (an optical filter);     1 - 1 ,  1 - 2 —sublayers (the optical filter);     2 —apertures in the first functional layer;     2 A—enclosed voids;     3 —a substrate;     4 —an optically transparent material (an adhesive);     5 —a protective cover;     10 —a second functional layer;     11 —an optical feature pattern;     12 —an optical (pattern) feature;     13 —a light passage;     20 —a third functional layer;     21 ,  31 —optical contacts;     51 —a reflector sheet;     7 —a light source;     71 —incident light;     72 —extracted (outcoupled) light;     111 ,  111 A,  111 B—a light-transmitting carrier medium;     121 —a pattern on the lightguide medium  101 ;     200 —an optical device.   

       FIGS.  1 A and  1 B  illustrate, at  100 , a concept underlying a novel light distribution element or a lightguide with a light distribution filter (LDF). In some instances, the light distribution element  100  is referred to as a “lightguide” 
     The light distribution element  100  comprises a light-transmitting carrier medium  101  configured for light propagation, such as propagation of incoupled light  71  emitted by a light source  7 . 
     The lightguide medium  101  is preferably optically transparent polymer or glass. In some instances, the lightguide medium is made of polymethylmethacrylate (PMMA) or polycarbonate (PC) materials. The light guide medium can be provided as a substantially planar medium, such as a sheet, a plate, or a film, for example, optionally provided with a number of prominent relief profiles on at least one surface thereof. 
     The element  100  further comprises at least a first optically functional layer  1  and a second optically functional layer  10 , referred to, hereafter, as first functional layer and a second functional layer, or as first- and second layers. Said layers  1  and  10  are each rendered with at least one optical function related to incident light. 
     The first functional layer  1  is configured as an optical filter layer (a light distribution filter) rendered with a light uniformity control function. In this regard, the first functional layer is further referred to, in some instances, as a “light filter” or an “optical filter”. 
     The first functional layer  1  is disposed on an at least one surface of the lightguide medium  101 . It is preferred that the optical filter layer  1  is an internal layer integrated within the element  100 . In some configurations, the optical filter layer  1  is integrated between the second functional layer  10  and the lightguide medium  101  ( FIGS.  1 A,  1 B ). 
     Thickness of the optical filter layer  1  is provided within a range of 1-10 micrometers (μm). 
     In some alternative configurations, provision of an additional layer or layers between the optical filter  1  and the second functional layer  10  and/or between the optical filter  1  and the lightguide medium  101  is not excluded. 
     The second functional layer  10  is preferably rendered with a light extraction function and/or a light outcoupling function. 
     In some configurations, the second functional layer  10  comprises at least one optically functional feature pattern  11 , as described in more detail further below. By provision of said pattern within the layer  10  and/or by virtue of material said layer  10  is made of, the second functional layer  10  is rendered with the optical function or functions mentioned above, namely, extraction and/or outcoupling of light propagated in and/or through the lightguide element  100 . 
     In a number of configurations, the both functional layers  1 ,  10  are rendered with a predetermined optical function or functions related to light incident thereto at an angle equal and/or below the critical angle relative to the surface normal. 
     Critical angle is an incident angle of light relative to the surface normal, at which a phenomenon of the total internal reflection (TIR) occurs. The angle of incidence becomes a critical angle (i.e. equal to the critical angle), when the angle of refraction constitutes 90 degrees relative to the surface normal. Typically, TIR occurs, when light passes from a medium with higher) refractive index (R i ) to a medium with low(er) R j , for example, from plastic (R i  1.4-1.6) or glass (R i  1.5) to air (R i  1) or to any other media with essentially low refractive indices. For a light ray travelling from the high R i  medium to the low R i  medium, if the angle of incidence (at a glass-air interface, for example) is greater than the critical angle, then the medium boundary acts as a very good mirror and light will be reflected (back to the high R i  medium, such as glass). When TIR occurs, there is no transmission of energy through the boundary. From the other hand, light incident at angle(s) less than the critical angle, will be partly refracted out of the high R i  medium and partly reflected. The reflected vs refracted light ratio largely depends on the angles of incidence and the refraction indices of the media. 
     Critical angle is calculated in accordance with equation (1): 
     
       
         
           
             
               
                 
                   
                     θ 
                     c 
                   
                   = 
                   
                     
                       θ 
                       i 
                     
                     = 
                     
                       arcsin 
                       ⁡ 
                       ( 
                       
                         
                           n 
                           2 
                         
                         
                           n 
                           1 
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   1 
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     It should be noted that critical angle varies with a substrate-air interface (e.g. plastic-air, glass-air, etc.). For example, for most plastics and glass critical angle constitutes about 42 degree. Thus, in an exemplary waveguide, light incident at a boundary between a light-transmitting medium, such as a PMMA sheet, and air at an angle of 45 degree (relative to the surface normal), will be probably reflected back to the lightguide medium, thereby, no light outcoupling will occur. 
     In embodiments, the first functional layer  1  is thus configured as a total internal reflection (TIR) layer structure, in which the phenomenon of TIR is established by means various techniques and structures, as further described herein below. 
     The first functional layer  1  comprises or consists or a substrate material  3  (see  FIGS.  2 A,  2 G,  2 H ). The first layer  1  is advantageously configured as a substantially planar substrate, formed by a cladding, a coating, a film or a sheet. Said substrate  3  is preferably provided in solid or solidified from, as being applicable by printing, patterning, embossing, and the like, as described further below. Dependent on configuration, the substrate  3  is rendered with light transmissive or light reflective function. 
     Additionally or alternatively, the first functional layer  1  can comprise an adhesive material  4  (see  FIGS.  2 B- 2 F ). The adhesive  4  is preferably an optically clear adhesive (OCA) or a liquid optically clear adhesive (LOCA). The adhesive can be a low-viscosity, essentially liquid adhesive or a high-viscosity adhesive, such as essentially gel-type or harder. 
     Hence, a number of embodiments can be established, wherein the substrate material  3  is at least partly integrated into the adhesive material  4  (see  FIGS.  2 B- 2 D ); wherein the substrate material  3  and the adhesive  4  form a layered structure or a stack (see  FIGS.  2 D,  2 F ); and wherein the light filter layer  1  is established, at least partly, by the (adhesive) material  4  (see  FIG.  2 E ). In a latter event, one may consider the adhesive material  4  replacing the substrate material  3 . 
     By virtue of materials it is made of, the substrate  3 , can be rendered with refractive index value substantially equal to or higher than the refractive indices of the surrounding layers or, alternatively, lower, than the refractive indices of said surround layers (viz. refractive indices of the lightguide medium  101  and/or the second functional layer  10 ). 
     Hence, in some configurations, the first functional layer  1  is at least partly formed of the substrate material  3  having the refractive index substantially equal to or higher than the refractive index of the material constituting the lightguide medium  101  and, optionally, the refractive index of material constituting the second functional layer  10 . 
     In some alternative configurations, the first functional layer  1  is at least partly formed of the substrate material  3  having the refractive index lower than the refractive index of material constituting the second functional layer  10  and, optionally, lower than the refractive index of material constituting the lightguide medium  101  (see description to  FIG.  2 F ). 
     What is typically referred to as “low refractive index” is the refractive index value provided within a range of 1-1.4. 
     In a number of configurations, the first functional layer  1  is provided as a substantially planar, continuous, uniform layer (see  FIG.  2 H , for example). In some additional or alternative configurations, it is preferred that said first functional layer  1  comprises a plurality of discrete apertures  2 , formed in the substrate material  3 . 
     In terms of general implementation, the light distribution element  100  employs provision of a number of so called optical channels established in the element  100  to enable controlled light propagation through the light transmitting medium. As a general remark, in the context of the optical channel related concept, by the expression “light transmitting medium” we refer to any media capable of propagating light therethrough (i.e. not preventing light from propagating therethrough). As shown on  FIGS.  1 A and  1 B , the optical channel, or a pathway for effective and controlled propagation of light rays emitted by the light source  7  (rays  71 ) to a display surface, for example (rays  72 ), is established, in the element  100 , by the light transmitting media and/or the light transmitting optical structures comprising the light transmitting media provided within the components forming the element  100 , namely, the within the functional layers  1  and  10 , and within the basic lightguide medium  101   
     To implement the optical channel concept discussed above, the first functional layer  1  thus comprises a number of optical contact areas  31 ,  41  ( FIGS.  2 A- 2 H ), referred to, hereafter, as “optical contacts” and configured to transmit light rays therethrough. 
     In some configurations, the optical contact area can be established across the entire surface laid with the first functional layer  1  and represented by the substrate  3  (see  FIGS.  2 F,  2 H ) and/or by the adhesive  4  (see  FIGS.  2 E,  2 F ). In some configurations, the optical contacts are provided as substantially discrete regions established, as described with reference to  FIGS.  2 A- 2 D and  2 G . 
     Implementation of the optical contacts  21 ,  31  can be such, as to enable controlled propagation of light rays to the second functional layer  10  and from said second functional layer  10 . 
     The optical filter layer  1  disposed between the patterned ( 11 ) second functional layer  10  and the lightguide substrate  101  accounts for enhanced uniformity of light passing therethrough. Enhanced uniformity is achieved by a thorough selection of materials said optical filter layer is made of and, optionally, provision of apertures  2  and/or filling materials for these apertures. 
     By virtue of materials the optical filter layer  1  is fabricated of and/or by provision of the apertures  2  therein, said optical filter layer  1  is configured control light incident thereto at angles of incidence equal and/or below the critical angle relative to the surface normal (at an interface between the media). For the second functional layer  10 , referred to, in some instances, as an “air-cavity light extraction layer”, this function is enabled by provision of the optically functional pattern structures, as described further below. 
     A number of configurations for the light distribution element  100  and methods for assembling a layered structure shall be described next with the reference to  FIGS.  2 A- 2 H . Direction of light propagation is indicated by dashed lines. As a disclaimer, we note hereby, that these indications are intended to merely illustrate the manner of light propagation through the element  100  within the concept of optical contacts and optical channels disclosed hereby, and, therefore, should not be interpreted in a sense of strict compliance with the laws of physics. 
     Reference is further made to  FIGS.  2 A and  2 B  describing, within the inventive concept, two basic configurations for formation of optical contacts in the first functional layer  1 . 
     As mentioned above, the substrate  3  that forms said first functional layer  1  can be provided with apertures  2 . In some configurations, the apertures  2  are through-apertures that extend through an entire width thereof, as from an overlaying layer (hereby, the second functional layer  10 ) to an underlying layer (hereby, the lightguide medium  101 ). 
     By virtue of mentioned apertures  2 , a number of enclosed voids  2 A is formed upon integration of said first functional 1 layer  1  within the light distribution element  100  ( FIG.  1 A ). In some configurations, said enclosed voids  2 A are filled with gaseous medium, such as air, nitrogen, oxygen, argon, etc., or vacuum. 
     Enclosed voids  2 A configured as air-voids (“air-traps”) formed hereby prevent light from passing therethrough due to the phenomenon of TIR. Optical contacts  31  are hereby established by the substrate  3  (embodied at  3 A) fabricated from material enabling light propagation therethrough. In the exemplary configuration shown on  FIG.  2 A  the substrate  3  is represented by a plurality of bonding dots  3 A, such as printed bonding dots, for example, that dots act as optical contacts  31  for enabling light transmission to the light extraction layer  10  and for providing optical bonding strength with the mentioned layer  10 . In this regard, the light distribution element  100  shown on  FIG.  2 A  is a fully laminated and integrated, in terms of light propagation, element comprising: 1) the lightguide medium  101 , configured, for example, as a basic PMMA lightguide or other light transparent material without any light extraction pattern; 2) the first functional layer  1 , embodied at  1 A, with enclosed voids  2 A, such as air-voids, alternating with optical contacts  31  formed by the light-transmissive substrate  3 A (provided as printed dots, for example); and 3) the second functional layer  2  configured as the light extracting layer  10  with an air-cavity pattern for efficient and controlled light distribution. 
     It should be mentioned that the refractive index of air filling the enclosed voids  2 A, is generally lower than the refractive index of the material constituting the lightguide medium  101 , and optionally, the refractive indices constituting the media of the layer components  1  and  10 . 
       FIG.  2 A  thus describes a basic configuration, in which the optical contacts  31  are formed by substrate material  3  (hereby,  3 A). 
     In the lightguide element  100  disclosed hereby, light uniformity control is implemented utilizing internal and integrated optical filter  1  based on a concept of optical channels or optical contacts described hereinabove, in particular, with regard to light having particular angles of incidence. Mentioned optical contacts are realized by a plurality of ways, including, but not limited to apertures and light filtering, provision of air-voids, provision of a low R i  layer, and/or provision of a reflector layer (configured to attain diffusing, Lambertian, or specular reflection) of a desired color. 
     Printed dots, such as shown on  FIG.  2 A  and also on  FIG.  2 G , represent a simplest approach for controlling uniformity and transmitting a desired range (in terms of angle of incidence, for example) of light into the light extraction layer  10 . Printed dots do not bear any optical functionality, as light passing therethrough does not undergo extraction (via refraction, reflection, collimation, and the like); instead, said printed dots form optical passages (optical contacts) for light rays to propagate from the first functional layer  1  and/or the underlying lightguide medium  101  to the section function layer (light extraction layer)  10 . 
     In terms of size, the printed dots can be provided within a range of e.g. 5 micrometers up to hundreds of micrometers, depending on a particular application and design of the element  100 . Height of the dot is defined by the thickness of the optical filter layer  1  and it is preferably not too high (within 1-10 micrometers, for example) in order to avoid any optical extraction. Typically, dots can be printed by inkjet, flexo-, gravure, imprinting, mask or stencil printing, silk printing, and the like. 
     As shown on  FIG.  2 A , an area, within the light filter layer  1 , without optical dots and channels has a thin airgap (air-voids  2 A), which acts as a reflector and prevents undesired light from propagation therethrough. This is an easy and cost-effective alternative, as compared to applying special coating materials, such as low R i  coatings, for example. 
     Typical application area for the solution described above is display backlight- and/or illumination panels. Due to provision of airgaps, the solution of  FIG.  2 A  is the most appropriate for applications that do not require full transparency. 
       FIG.  2 B  describes another basic embodiment, in which the optical contacts  21  can be viewed as being established in the first functional layer  1  by a number of apertures  2  formed in a substrate material  3 . The substrate  3  (embodied at  3 B) shown on  FIG.  3 B  is a reflective film with apertures  2 . The reflective film can be rendered to provide specular or diffusive reflection; naturally, the substrate  3 B reflects light arriving thereat. Apertures for such a reflective film can be produced by fast laser drilling process, for example. 
     In order to create optical contacts  21 , the reflective film  3 B has been integrated into an optically transparent adhesive  4  (OCA, LOCA, etc.). The adhesive  4  can be liquid, low-viscosity adhesive or a gel-type adhesive material. The first functional layer  1  (embodied at  1 B) thus comprises the reflective substrate  3 ,  3 B integrated into the optically transparent adhesive  4 . Upon integration into adhesive  4 , the apertures  2  in the substrate  3 B become “filled” with the optically clear material, thus forming optical contacts  21 . In configuration shown on  FIG.  2 B  the voids  2 A are not formed; instead, the optical filter layer  1  is laminated by means of an adhesive  4 . 
       FIG.  2 B  shows that, upon formation of the first functional layer  1 , the reflective film  3 B is enclosed into the adhesive  4  such, that an interface is formed between the adhesive  4  and the structures  101  and  10 . In alternative configurations, the adhesive  4  can be applied such as to fill up the voids (apertures  2 ) within the substrate  3 ,  3 B such that the reflective surfaces  3 B shall be deposited at the interface between the structures  101  and  10 . 
     In any event, the first functional layer  1  (embodied at  1 B), is fully laminated between the two main layers  101 ,  10  such, as to provide controlled uniform light. Optical adhesive has preferably refractive index equal or higher than that of the lightguide material  101  and, optionally, than that of the light extraction layer  10 . 
     The light distribution element  100  shown on  FIG.  2 B  is a fully laminated and integrated element comprising: 1) the lightguide medium  101 , configured, for example, as the basic PMMA lightguide or other light transparent material without any light extraction pattern; 2) the first functional layer  1 , embodied at  1 B, comprising the reflective substrate  3 B with apertures  2  integrated or filled by a low-viscosity- or gel-type optical adhesive material  4  to form optical contacts  21 ; and 3) the second functional layer  2  configured as the light extracting layer  10  with an air-cavity pattern for efficient and controlled light distribution. 
     In embodiments, the optical contact  21 ,  31  can be provided as any one of: a line, a dot, a geometric shape, a cross, a grid, or as a pattern comprising any combination thereof. 
     The optical contacts  21 ,  31  can be arranged into an at least one array within an at least one predetermined location at said first functional layer  1  or into an at least one array extending along and/or across an entire surface of said first functional layer  1 . 
       FIG.  6    illustrates exemplary configurations for the optical contacts  21 ,  31 . The optical contacts can be implemented according to any basic embodiment described for  FIGS.  2 A and  2 B , with the optical contacts established by a substrate material  2  (optical contacts  31 ) or by an optically clear adhesive material within the apertures  2  (optical contacts  21 ). 
     Whether the optical contacts are embodied, at  31 , as light transmitting printed patterns  3 A (according to  FIG.  2 A ) or as optically clear adhesive patterns  21  provided between the reflective structure  3 B (according to  FIG.  2 B ), density, size and coverage for each said optical contact pattern  21 ,  31  can vary in order to achieve desired mode for light propagation and to attain enhanced control over said light propagation. 
       FIG.  2 C  illustrates a configuration, in which the first functional element  1  comprises a number of enclosed voids  2 A, such as air-voids, for example, formed in the adhesive material  4 . The configuration is assembled as follows. A substrate film  3 , embodied at  3 C, configured as an essentially (optically) transparent film is obtained and integrated into the adhesive  4  in a manner discussed previously with reference to  FIG.  2 B . The substrate  3 C preferably has the refractive index same or similar to that of the underlying lightguide medium  101  and the adhesive material  4 . Apart from the implementation shown on  FIG.  3 B  and utilizing a liquid, low-viscosity adhesive or a gel-type adhesive, the adhesive  4  for  FIG.  2 C  is preferably a high-viscosity adhesive. The adhesive  4  penetrates through the apertures  2 , e.g. the laser drilled apertures, and forms an optical bonding with the light extraction layer  10  (and the underlaying lightguide medium  101 ). High-viscosity adhesive  4  can be further patterned by any appropriate method to form the air traps  2 A. The optical contacts  21  are formed by provision of the apertures  2  integrated into the high-viscosity adhesive  4 . 
     The light distribution element  100  shown on  FIG.  2 C  is a fully laminated and integrated element comprising: 1) the lightguide medium  101 ; 2) the first functional layer  1 , embodied at  1 C, and comprising the first functional element  1  configured as an optically transparent film with aperture design laminated with high-viscosity- or gel-type optical adhesive material between the lightguide medium  101  and the extracting film  10  forming air traps  2 A for optical uniformity control, and 3) the light extracting layer  10  with an air-cavity pattern for efficient and controlled light distribution. 
     We further specify that the apertures  2  generally formed in the substrate layer  3  can act, in some embodiments, as optical contacts  21  (e.g.  FIG.  2 B ) and, in some alternative embodiments, as TIR-functional parts. Configurations, in which the apertures form TIR-functional parts, are illustrated by  FIG.  2 A  and  FIG.  2 C . 
     In embodiments, the first functional layer  1  can be configured to comprise at least two sublayers  1 - 1 ,  1 - 2 . Provision of such essentially multilayer structure is illustrated by configurations shown on  FIGS.  2 D and  2 F . 
       FIG.  2 D  illustrates configuration, in which the optical filter layer provided as a multilayer structure (a stack) with apertures  2 . Mentioned stack comprises at least two sublayers  1 - 1 ,  1 - 2  with the apertures  2  that pierce through all said sublayers. In configuration shown on  FIG.  2 D , the stack structure is formed by a plastic sheet, such as a PMMA sheet ( 3 E, sublayer  1 - 2 ) laminated, at least on one side, with a low R i  film ( 3 D, sublayer  1 - 1 ). Similarly to the configuration of  FIG.  2 B , the layered structure with apertures shown on  FIG.  2 D  is integrated into the adhesive  4  provided as liquid, low-viscosity- or gel-type adhesive to form the first functional layer  1  (embodied at  1 D). 
     Hence, the first functional layer  1  may comprise a sublayer  3 D ( FIG.  2 D ) formed by a material having the refractive index lower than the refractive index of the material constituting the lightguide medium  101  and, optionally, than the refractive index of material forming the second functional layer  10 . 
     In some instances, provision of the sublayer  3 E can be omitted and the first functional layer structure  1 D can be formed from a single (sub)layer  3 D provided as a low R i  film with apertures (not shown). 
     Overall, the solution of  FIG.  2 D  is similar to that shown on  FIG.  2 B , but the optical filter film  1  is a made, at least partly, of a transparent, low R i  material. 
     The light distribution element  100  shown on  FIG.  2 D  is a fully laminated and integrated element comprising: 1) the lightguide medium  101 ; 2) the first functional layer  1 , embodied at  1 D, and comprising the low R i  film  3 D optionally provided on a sublayer  3 E (PMMA film) with aperture design laminated with the low-viscosity- or gel-type optical adhesive  4  between the lightguide medium and the light extracting film, and 3) the light extracting layer  10  with an air-cavity pattern for efficient and controlled light distribution.  FIG.  2 E  shows a configuration, in which the first functional layer  1  (embodied at  1 E) is represented by a layer of adhesive  4 , preferably, having the refractive index R i  lower than that of the lightguide medium  101 . Additionally, the lightguide medium  101  can be provided with a number of prominent, optically functional relief profiles  121  that can be further integrated with said adhesive material  4 . The pattern or patterns  121  are preferably rendered with light refraction functionality; however, without light outcoupling (extraction). In configuration shown on  FIG.  2 E  the optical filter layer  1  is thus established by a substantially low R i  adhesive material  4 , optionally combined with a number of relief pattern profiles  121 . 
     The pattern(s)  121  provided in the lightguide medium  101  is a simple formation, which does not extract light out of the light distribution element  100 , when laminated. This pattern just refracts- and controls the uniformity of incident light for the next extraction layer  10 . The configuration shown on  FIG.  2 E  may utilize a conventional patterned lightguide, which is fully laminated together with light extraction layer  19 . This concept also utilizes incident light, which is equal or below the critical angle. 
     The light distribution element  100  shown on  FIG.  2 E  is a fully laminated and integrated element comprising: 1) the lightguide medium  101  provided as the basic PC lightguide or other light transparent material with some light refracting pattern (no light outcoupling), 2) the optical filter with a lamination adhesive (laminating the lightguide medium and the extracting film), having slightly lower R i  value than the lightguide medium material, and 3) the light extracting layer with an air-cavity pattern for efficient and controlled light distribution. 
       FIG.  2 F  illustrates the light distribution element  100  similar to that shown on  FIG.  2 E . In comparison to the optical filter structure shown on  FIG.  2 E , the optical filter structure (the first functional layer  1 ) of  FIG.  2 F  additionally comprises the substrate  3  made of the material with low refractive index. Said substrate  3  can be provided in the form of a low R i  coating, for example, arranged next to the light extraction layer  10 . The low R i  value can be optimized for the pattern solution of said light extraction layer  10 , in order to control, which light is extracted out. 
     Similarly to the optical filter structure  1  shown on  FIG.  2 D , the optical filter structure of  FIG.  2 F  can be considered as a stack solution, wherein the first sublayer  1 - 1  is the low R i  coating, whereas the adhesive and, optionally, the lightguide pattern  121 , constitute the second sublayer  1 - 2 . The substrate  3  of  FIG.  2 F  can be made of same or similar low R i  material as the sublayer  3 D ( FIG.  2 D ), for example. 
       FIG.  2 G  illustrates the configuration similar to that shown on  FIG.  2 A , but implemented with the second functional layer  10  comprising open-top pattern features. The first functional layer  1 , implemented at  1 G, comprises the substrate  3 , implemented as a plurality of printed dots. The optical contacts  31  between the lightguide medium  101  and the light extraction layer  10  are established by said printed dots  3 . The substrate (printed dots)  3  preferably has refractive index equal to that of the light guide medium  101 . In addition to forming the optical channels, the printed dots  3  serve for laminating the first functional layer  1  to the second functional layer  10  with the open-top light extraction pattern. Additionally, via the substrate  3 , forming the optical channels, light is further directed to the (upper) layer  10  for final light extraction. Additionally, a number of apertures is formed between the printed dots established by the substrate  3  (in the first functional layer  1 G). 
     The light distribution element  100  shown on  FIG.  2 G  is a fully laminated and integrated element comprising: 1) the lightguide medium  101  provided as the basic PMMA lightguide or other light transparent material without any light extraction pattern, 2) a plurality of printed dots between the lightguide medium and the light extraction film  10 , which dots form a physical bonding and, additionally, an optical channel for light uniformity control; and 3) the light extracting layer  10  with an open optical pattern for efficient and controlled light distribution. 
     Optical dots formed from the substrate  3  ( FIG.  2 G ) do not penetrate inside the open extraction pattern of the second functional layer  10 . Optical dots merely form an optical contact and provide bonding strength between the lightguide  101  and the light extraction layer  10 . 
     It should be noted, that on the contrary to the configuration shown on  FIG.  2 A , for example, the configuration of  FIG.  2 G  does not involve formation of enclosed voids (air-traps). Hence, the apertures formed in the substrate layer  3  (of the first functional layer  1 G) connect with a number of optically functional cavities  12  (e.g. air-cavities) defined in the second functional layer  10  with the open optical pattern. The printed dots  3  that form the optical contacts for the first functional layer  1 G connect, in turn, with a substantially light transmissive material the second functional layer  10  is made of and establish “optical channels” throughout an entire height and, optionally, width of the light distribution element  100 . In the embodiment of  FIG.  2 G , the apertures formed in the first functional layer  1 G can be referred to as “non-enclosed voids” (as being connectable to the air-cavities  12 ), when said apertures become integrated between the layers  10  and  101 . 
       FIG.  2 H  shows further configuration for the light distribution element  100 , in which the first functional layer  1  is embodied in similar manner as shown on  FIG.  2 G , but in an absence of apertures  2 . Provision of the substrate  3  is such, as cover an entire area across the lightguide medium  101  and to form an optical bonding between said lightguide  101  and the light extraction layer  10 . The substrate  3  shown on  FIG.  2 H  can be considered as an optical contact arranged across an entire surface of the lightguide medium  101 . 
     The optical filter layer  1  can be configured as a transparent, low refractive index filter layer or as reflective TIR layer (e.g. diffusive or specular TIR layer) formed on the at least one side of the optically transparent (lightguide) substrate  101 . Said optical filter can be: a) applied directly on a flat surface, b) laminated by an adhesive layer, or c) bonded by chemical surface treatment such as VUV (vacuum UV), atmospheric plasma treatment or microwave assisted bonding. 
     In some instances, the light filter layer  1  has gradually variable low R i  values to provide preferred light distribution even in an absence of apertures. 
     The apertures within the light filter layer  1  can be optically modulated, whereby a variety of light distribution patterns produced by the light filter layer can be attained, including, but not limited to: uniform, symmetric, discrete, or asymmetric light distribution patterns. 
     Light distribution by the optical apertures forming a predetermined figure (an image) or a signal, for example, such as on a display, a signage or a poster (see  FIG.  4   ), can be uniform, non-uniform or discrete. Thereby, uniform, non-uniform or discrete figure (image) or signal can be formed. Apertures can be provided on both sides of the optical filter layer forming uniform/continuous or discrete areas. The apertures can be provided throughout the entire surface of the optical filter layer or at predetermined areas thereof. 
     The principal function of apertures is to control the amount of incident light propagating from the first medium to the second medium without light outcoupling, meaning all incident light angle is larger or the same as the critical angle in the medium. Especially, light uniformity control can thus be achieved without optical pattern. 
     The apertures can be provided as optical apertures (optical contacts) with a number of primary functions, such as transmitting light therethrough from the first medium to the second medium, which determines desired light distribution and/or uniformity. Light distribution in the first and second medium typically has an incident light angle below the critical angle (an angle of incidence above which TIR occurs) with regard to the medium interface, when air or low R i  filter/-cladding are forming the interface. As a result, light is not outcoupled from the medium. 
     In addition of being provided as optical apertures (optical contacts), mentioned apertures can establish, in some embodiments, TIR functional parts (as shown on  FIGS.  2 A,  2 C ). The apertures can be manufactured by means of laser ablation, short pulse system, plasma etching, mask assisted excimer exposure, micro-printing and/or any other suitable method. For example, laser ablation can be performed utilizing roll-to-roll equipment and methods, wherein the production process may speed up to 40 meters per minute. 
     Optical apertures can be fabricated by a variety of methods, including, but not limited to: laser patterning, direct laser imaging, laser drilling, mask and/or maskless laser or electron beam exposure, modifying optical material/R i  value by applying discrete proper-ties by printing, inkjet printing, screen printing, micro-/nano dispensing, dosing, direct “writing”, discrete laser sintering, micro electrical discharge machining (micro EDM), micro machining, micro moulding, -imprinting, -embossing, and the like. Formation of optical apertures can be completed upon a direct contact with the low R i  cladding or a reflective TIR cladding. 
     In the light distribution element  100  the optical filter layer  1  (the first functional element) and the light extraction layer  10  (the second functional element) can be produced by roll-to-roll- or roll-to-sheet methods. 
     It is preferred, that the first functional element  1  is produced on the lightguide medium  101  prior to the second functional element  10 . 
     Additionally, aperture formation can be completed upon an indirect contact, such as operating through the carrier substrate or a lightguide element (medium), e.g. by means of laser ablation, thereby the cladding is removed by ablation, thus forming a desired aperture feature in terms of size and shape in the same manner as by means of the direct contact method. Laser beam spot profile is preferably shaped as a flat top-hat, which does not produce excessive heat and does not damage the carrier substrate or the lightguide medium element, accordingly. Laser wavelength can be selected in terms of cladding absorption curve, hole edge quality, beam shaper optics, thickness/height, operation costs, and the like. 
     The light distribution element  100  further comprises the second functional layer  10 , preferably rendered with a light extraction function and a light outcoupling function. 
     The second functional layer  10  comprises at least one optically functional feature pattern  11  formed in a light-transmitting carrier medium  111  by a plurality of features provided as optically functional cavities  12 . Mentioned 
     In some configurations ( FIGS.  2 G,  2 H ), said at least one optically functional feature pattern  11  comprises the optically functional cavities  12  configured as open-top features. 
     In some configurations ( FIGS.  2 A- 2 F ), the at least one optically functional feature pattern  11  is fully integrated and/or embedded within the light-transmitting carrier medium  111 , whereby an embedded feature pattern is established in the light-transmitting carrier medium by a laminate structure formed by an entirely flat, planar layer  111 A of the carrier medium  111  arranged against a patterned layer  111 B of the carrier medium  111  and a plurality of optically functional internal cavities  12  is formed at an interface between the layers  111 A,  111 B. 
     The optical cavity features  12  can be selected from the group consisting of: a groove, a recess, a dot, and a pixel, wherein said cavity features  12  have crosswise profiles selected from: binary-, blazed-, slanted-, prism-, trapezoid-, hemispherical profiles, and the like, and wherein said cavity features have a lengthwise shape selected from: linear, curved, waved, sinusoid, and the like. 
     In preferred embodiments, the cavities  12  are filled with air. In some other embodiments, the cavities can be filled with another gas, fluid, liquid, gel, or solid media. 
     The optically functional pattern  11  can comprise a plurality of discrete profiles or a plurality of at least partly continuous profiles provided as a symmetric pattern structure or as an asymmetric pattern structure. 
     In some instances, the optically functional pattern can be provided as a hybrid pattern comprising a plurality of discrete profiles or a plurality of at least partly continuous profiles. 
     Said at least one optically functional pattern can be established by the relief forms selected from the group consisting of: a groove, a recess, a dot, and a pixel, wherein said relief forms have crosswise concave or convex profiles selected from: binary, blazed, slanted, prism, trapezoid, hemispherical, and the like, and wherein said relief forms have lengthwise shape selected from: linear, curved, waved, sinusoid, and the like. 
     In preferred embodiments, the at least one optically functional pattern is fully integrated and/or embedded within said light distribution element. 
     With reference to  FIG.  3   , the light distribution element  100  can further comprise a third functional layer  20 . In such an event, functionality attained by the second functional layer  10  provided as the extraction and light outcoupling layer can be combined with the functionality attained by said third functional layer. The third functional layer  20  can be provided as a conventional prismatic layer structure, as a hard protective coating, as an antireflective and anti-glare coating, a self-cleaning coating and the like. 
     A dual-type structure can thus be established with the air-cavity pattern (layer  10 ) and an open top pattern (layer  20 ). This opens a possibility to control light outcoupling distribution and other performances. For example, when the third functional layer  20  is configured as a prism type layer or a lenticular layer with the open pattern is utilized as a top layer, such solution can provide a bidirectional light distribution. 
     The light distribution element  100  can be thus configured as a multi-layer film that exploit both an air-cavity pattern (within the light extraction/second functional layer  10 ), and an open top pattern (e.g. prismatic pattern within the third functional layer  20 ). Additionally, a diffuser can be optionally integrated between mentioned optical pattern layers. 
     The light distribution element further comprises a light source  7 , selected from: a Light Emitting Diode (LED), an Organic Light Emitting Diode (OLED), a laser diode, a LED bar, an OLED strip, a microchip LED strip, and a cold cathode tube. 
     In another aspect, an optical device  200  is provided, comprising the light distribution element according to any of the embodiments described herein above. 
     The optical device can be configured as a frontlight illumination device or a backlight illumination device. 
       FIG.  4    thus demonstrates the light distribution element, according to some aspect, integrated into a signage and/or -advertisement illumination concept for a night-time luminaire. The advertisement film shown in  FIG.  4    can provided, by cutting for example, to adopt any shape, and it can be adhered onto a window or a screen. The solution comprises the light source  7  (the LED), arranged at the edge of the optical device  200 . The solution shown on  FIG.  4    can further comprise a reflector sheet  51  of a predetermined color. 
     The optical device  200  can be configured as a window, a façade illumination and/or indication element, a roof illumination and/or indication element, a signage, a signboard, a poster, a marketing board, an advertisement board illumination and/or indication element, and an illumination element configured for solar applications. 
     Hence, in an aspect, use of the optical device  200 , according to one of the previous aspects is further provided in illumination and indication, selected from the group consisting: of decorative illumination, light shields and masks, public and general illumination, including window, façade and roof illumination, signage-, signboard-, poster- and/or an advertisement board illumination and indication, and in solar applications. 
       FIG.  5    is further illustrative of a general concept for assembling a layered structure for the light distribution element  100 . The element  100  shown on  FIG.  5    thus comprises an upper medium  101 - 1  (e.g. consisting of or comprising the layer  10  with an optical extraction pattern, such as cavity optics, for example), and a bottom medium  101 - 2  overlaid with the optical filter  1  (with optical adhesive patterns, continuous lines with density variation). The upper and the bottom media are laminated together. Thus, a laminated lightguide with embedded light filtering/controlled light passing from the bottom to upper medium can be established. 
       FIGS.  7 A and  7 B  are further illustrative of how the thickness of second medium (a) controls light propagation and maximum size of local illumination area (c) together with size and format of optical adhesion contact (b). Light control, such as uniformity can be defined by ratio of multiple adhesion contacts (b) and height of second medium (a).  FIGS.  7 A and  7 B  thus show the impact of medium thickness (b) for illumination area (c), which is increasing with larger medium thickness. 
       FIGS.  7 A and  7 B  illustrate a fundamental functional of the optical contact  31  with regard to the illumination area. The relationship between the lateral size (b) of the optical contact and the lateral illumination projection (c) is directly related to the thickness of second medium (the layer  10 ). Final size of the optical contact can be defined for a preferred illumination target, in accordance with equation (2): 
     
       
         
           
             
               
                 
                   
                     c 
                     b 
                   
                   ∝ 
                   a 
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
     This is simplified solution that does not take into account any R i  values and Snell&#39;s law, and it can be utilized quickly to design a desired illumination area, total uniformity, discrete illumination, such as images, marking, etc. 
     As mentioned hereinabove, the optical contact, implemented as both  21 ,  31  does not form a real optical structure configured to manage light, to control light direction, etc. The optical contact(s)  21 ,  31  is/are merely contact areas that enable light propagation form the first medium (e.g. lightguide medium  101 ) to the second medium (e.g. the light extraction layer  10 ). 
     A ratio between vertical and lateral values has to be controlled in order to achieve a minimum ratio of 1/4 (vertical/lateral). Lateral value for the mentioned ratio is unlimited (in theory, said value can reach infinity), therefore, the ratios of 1/8, 1/20, 1/100, etc., are possible. Typical vertical dimensions (thicknesses) are provided within a range of 0.5-100 μm. 
     In an aspect, a roll of a light distribution element is further provided, comprising: a first functional layer  1  configured as an optical filter layer, and a second functional layer  10  comprising an at least one optically functional pattern  11 , wherein the first functional layer  1  is rendered with a light uniformity control function. 
     In said roll of the light distribution element, the first functional layer  1  can be established by a structure implemented according to any configuration described hereinabove. 
     It is clear to a person skilled in the art that with the advancement of technology the basic ideas of the present invention are intended to cover various modifications thereof. The invention and its embodiments are thus not limited to the examples described above; instead they may generally vary within the scope of the appended claims.