Patent Publication Number: US-2023157892-A1

Title: Method, equation, design, and construct to provide uniform heating for shaped heaters with improved busbar designs

Description:
STATEMENT OF RELATED APPLICATIONS 
     This patent application claims the benefit of and priority on U.S. patent application Ser. No. 17/078,287 having a filing date of 23 Oct. 2020, U.S. Provisional Patent Application No. 63/074,138 having a filing date of 3 Sep. 2020, and U.S. Provisional Patent Application No. 63/005,745 having a filing date of 6 Apr. 2020, all of which are incorporated herein by this reference. 
    
    
     BACKGROUND 
     Technical Field 
     The present disclosure generally is in the field of providing uniform heating for various electric heater shapes. The present disclosure more specifically is in the field of electrically heating transparent conductive materials with a uniform sheet resistivity for defogging and de-icing various surfaces. 
     Prior Art 
     Transparent conductive materials have been used to provide transparent heated shield and goggle lenses using ITO (Indium Tin Oxide) as a coating on clear substrates such as polymers. Conductive films using silver nano particles and carbon are available from sources such as Chasm Corporation as alternatives to the ITO. These materials when connected electrically by means of printed silver conductive busbars to a power source can be heated to some design temperature, so that snow, ice, or vapor condensation or fogging can evaporate or melt, thus providing a clear visual window in inclement or high humidity weather. U.S. Pat. Nos. 5,500,953 and 5,351,339 to Reuber and U.S. Pat. No. 3,024,341 and others describe this concept. In addition, U.S. Pat. Nos. 4,485,927, 4,656,339, and 4,814,586 disclose a busbar using continuous stripes of printed silver and an overlay of a continuous copper strip to connect with uniformly printed stripes of printed carbon conductors for use with printed underfloor heaters. 
     US Patent Publication No. 2018/0239131 to Cornelius and US Patent Publication No. 2015/0121610 to Cornelius disclose an intermittent connection to an ITO uniform conductive sheet using a complex method comprising two spring-loaded mechanical busbars that must be carefully assembled to provide a conductive alignment with “painted silver” contacts or with the conductive ITO. These mechanical spring-loaded busbars must be compressed and held in place by some mechanical clamp that is less favored when one considers the shock and vibration involved in skiing and other winter sports and activities. Additionally, such a contact on ITO can be problematic as ITO is a fragile thin ceramic coating that can easily crack and shatter when point loaded, thus rendering the ITO non conducting. Additionally, the Cornelius references make the goggles very thick and massive, and also more expensive. Further, the Cornelius references do not disclose any specific method for determining the parameters of such an intermittent connection, disclosing that one must use experimentation to determine these variables. In fact, the Cornelius references show non-contacting zones, or less resulting current, in the part of the lens with the widest spacing, which would require the greatest contact and resulting current because watt=V 2 /(L 2 p). 
     US Patent Publication No. 2009/0321407 to Dixon discloses a general concept for a vehicle glazing comprising a pane of glazing material, e.g. glass, and a heatable coating layer provided on a surface of the glazing, in electrical contact with first and second electrically conductive busbars, each busbar having a length, a width and first and second ends, the width of at least one of the busbars being gradually reduced towards at least one of its ends. The glazing may be a laminate, having a further pane of glazing material joined to the pane of glazing material by a ply of interlayer material. 
     US Patent Publication No. 2018/0168001 to Hartzler discloses a heating element includes a first carbon nanotube (CNT) layer and a second CNT layer. At least a portion of the first CNT layer overlaps at least a portion of the second CNT layer, and the first CNT layer includes a first perforated region having a plurality of perforations. The Hartzler reference discusses the ability to tailor the resistivity of CNT to application-specific heating or ice protection needs by utilizing perforated CNT sheets or stacked CNT sheets or layers where at least one of the CNT layers is perforated. Using perforated CNT sheets or combining perforated and non-perforated CNT sheet layers in one heating element will allow the resistivity of the heating element to be varied to suit individual application heating, anti-icing and/or de-icing needs. 
     US Patent Publication No. 2008/0264930 to Mennechez describes the concept of altering sheet resistivity by providing voids in the uniform conductor. However, Mennechez fails to describe how to alter the sheet resistivity to provide a uniform watt density in heating of irregular heaters (non-parallel) busbars. In fact, the examples provided in Mennechez appear to only relates to scenarios with uniform watt density. 
     A problem with the prior art mentioned above is that the distance between the printed busbars varies depending on the visual design or design shape. This can lead to non-uniform heating and hotspots in the coating, or overheated areas that can cause burning and distortion in the heated lens coating and/or substrate. This prior art, in addition to causing hotspots and possible distortion, severely limits the use of goggles or visors of this type at extremely low temperatures due to limitations and the glass point of the plastic substrate. The non-uniform heating when charged by a battery source would require larger batteries and would reduce functional operation, such as heating time. 
     Inclement weather and changes in humidity as well as deep cold provide challenges to users of goggles, visors, spectacles, and other lenses. For example, such weather and humidity changes can cause lenses to fog, allow snow to adhere to, or allow frost or ice to form on such lenses. Coatings which prevent fogging have their limitations and existing systems using a dual paned lens configuration with an ITO sputtered lens with silver busbars for supplying electrical power to the ITO fail to provide consistent manageable performance. Goggle lenses using ITO and other transparent conductive materials with a uniform sheet resistivity are electrically heated for defogging and de-icing in a cold environment. The design of nonparallel busbars used to connect the conductive material can at room temperature cause excessive and dangerous hot zones on the conductive materials. 
     What is needed in the art is a method, design, and construct for providing uniform heating to surfaces, such as goggles, using electrically heated conductive films. It is to such methods, designs, and constructs, and others, that preferred embodiments of the present disclosure are directed. 
     BRIEF SUMMARY 
     The present disclosure relates to avoiding hot spots when generating heating using heaters with a non-uniform width. The solutions of the present disclosure more particularly relate to transparent heated surfaces for providing a see-through barrier, such as lenses for goggles, shields for helmets, etc., certain windows, etc. 
     The heated-surface is composed of a substrate of a non-uniform width that forms the shape of the surface on which is applied a conductive medium, such as indium tin oxide. For instance, in the case of a lens for goggles, the width at the nose area is lesser than the width of the lens at the eye region (the regions of the lens that will face an eye of the user). In order to avoid hot spots at regions of the surface where the width is smaller, the present disclosure offers solutions to reduce or even eliminate these hot spots. 
     In one embodiment, the present disclosure describes the use of solid state continuous thin printed busbars that use printed transparent dielectric materials to provide intermittent connection with the conductive medium (ITO) or other uniform sheet resistive conductors. This provides a very thin, reliable, and inexpensive assembly not subject to shock and vibration damage or moisture ingress. The current disclosure provides an equation for the design that calculates and provides for contact zones for an intermittent connection between the busbars and the conductive medium so as to approximate a uniform watt density to prevent hot spots. The length of the non-contact points between the conductive material and the busbars is increased as the linear distance between the two opposing busbars decreases, and decreases when the linear distance between the two opposing busbars increases. Moreover, the contact-points and non-contact points between the two opposite busbars mirror each other, therefore being symmetrical. 
     In another embodiment, hot spots are avoided by altering the sheet resistivity of the conductive material by at least one of holes, voids and dots applied to the thin conductive material to alter resistivity across a surface defined by the thin conductive material, wherein the quantity and density of the at least one of holes and voids may increase when the busbars are closer together than when the busbars are farther apart. The number and density of dots may increase when the busbars are farther apart than when the busbars are closer together. 
     Briefly, a broad aspect of the present disclosure is and relies on a method for uniform heating of surfaces, comprising using continuous conductive busbars and dielectric coatings so as to have an intermittent electrical contact with a conductive film to provide uniform heating. Clear substrates are coated with a uniform transparent conductive film, and a novel busbar arrangement is applied to generally opposite sides of the conductive film so as to provide a more uniform heating of the conductive film over the entirety of the lens. 
     Another broad aspect of the present disclosure includes a mathematical analysis with developed equations and a means of precisely providing an intermittent electrical connection so that the Watt density to, and heating of, the conductive materials is uniform, allowing much higher temperature for de-icing and defogging and more efficient use of energy. This same concept can be used for three-dimensional formed heaters to compensate for non uniform sheet resistivity. 
     A further broad aspect of the present disclosure includes a means of yielding improved busbar designs, including an equation and a means of altering sheet resistivity to produce electric heaters with non-parallel busbars of various shapes for uniform heating and Watt density. 
     Other broad aspects of the present disclosure include methods for uniform heating of surfaces, comprising using conductive busbars and dielectric coatings so as to have an intermittent electrical contact with a conductive film to provide uniform heating. 
     These representative methods also can include busbars that are continuous. 
     These representative methods also can include busbars that are not parallel to each other. 
     These representative methods also can include dielectric coatings that are transparent. 
     These representative methods also can include conductive films that are transparent. 
     The above representative methods also can include embodiments in which the non-contact spacing used to provide uniform heating M between busbars is determined by the equation 
     
       
         
           
             
               M 
               = 
               
                 
                   
                     ( 
                     
                       
                         L 
                         1 
                       
                       
                         L 
                         2 
                       
                     
                     ) 
                   
                   2 
                 
                 ⁢ 
                     
                 w 
                 - 
                 w 
               
             
             , 
           
         
       
     
     where L 1  is the longer path between busbars, L 2  is any path between busbars, and W is an electrical contact distance. 
     The concept in the equations disclosed herein of a uniform watt density (watt/area) greatly simplifies the design of the lens as one merely multiplies the watt density by the lens area to calculate the wattage. As the voltage required to heat the longest separation between the busbars is known to achieve a given ΔT, one can easily determine the current and the battery size (amp/hour) and voltage, greatly improving battery efficiency and longer heating time. 
     All of these representative methods also can include dielectric coatings that are continuous, preventing a continuous busbar over the dielectric coatings from contacting the conductive film except where the busbar protrudes past the dielectric coating making contact. 
     All of these representative methods also can include electrical busbars that are continuous except where a dielectric coating underneath the busbar prevents electrical contact. 
     All of these representative methods also can include busbars that are bonded with a conductive adhesive to a thin copper foil and then laminated together. 
     All of these representative methods also can include the use of a copper foil that is soldered to a power supply. 
     All of these representative methods also can include using a tapered or decreasing width busbar for uniform resistance heaters. 
     All of these representative methods also can include constructing intermittent contact busbars for three-dimensional transparent conductive heaters. 
     Additional broad aspects of the present disclosure, including in connection with all of the previously mentioned representative methods, include methods of using varying sheet resistivity to provide uniform heating for heaters without parallel busbars. 
     All of these representative methods also can include determining the sheet resistivity using the equation 
     
       
         
           
             
               ρ 
               2 
             
             = 
             
               
                 
                   ρ 
                   1 
                 
                 ( 
                 
                   
                     L 
                     1 
                   
                   
                     L 
                     2 
                   
                 
                 ) 
               
               2 
             
           
         
       
     
     for uniform heating. 
     All of these representative methods also can include using voids or holes in the conductive heater material to increase sheet resistivity. 
     All of these representative methods also can include using conductive dots on the conductive heater material to decrease sheet resistivity. 
     All of these representative methods also can include using a combination of conductive dots and voids to give a wide variation of sheet resistivity. 
     All of these representative methods also can include providing non-uniform heating with parallel busbar heaters. 
     All of these representative methods also can include cracking or scoring the dielectric coating to disrupt current flow with minimal visual changes in the dielectric coating. 
     All of these representative methods also can include using a knife die for the cracking or scoring the dielectric coating. 
     All of these representative methods also can include using various shapes of the knife die to create electrically isolated areas on the dielectric coating. 
     All of these representative methods also can include cracking or scoring of the dielectric coating to disrupt current flow resulting in unheated areas in critical parts of the surface to prevent over-heating. 
     All of these representative methods also can include using the unheated areas to provide more current and heating into a portion of the surface, wherein the portion of the surface is a large viewing area portion of the surface. 
     All of these representative methods also can include using laser cuts or knife dies to disrupt conductivity and create unheated zones in a clear dielectric material located between busbars on a surface. 
     All of these representative methods also can include using laser cuts or knife dies to punch holes in a polyester film and then vapor coating the polyester film with a dielectric coating, thereby resulting in holes in the dielectric corresponding to the holes in the polyester film. 
     All of these representative methods also can include using the holes on the vapor coated dielectric coating on polyester film to change sheet resistivity. 
     All of these representative methods also can include using the equation ρ 2 =ρ(L 1 /L) 2  to determine the holes area to decrease the sheet resistivity on the surface so as to result in more uniform heating. 
     All of these representative methods also can include using embedded wires within a dielectric coating and polycarbonate substrate sandwich and a thin silver connection to obtain conductive busbars. 
     All of these representative methods also can include locating the embedded wire busbars so as to maximize a viewing area through the surface. 
     All of these representative methods also can include using the embedded wire busbars so as to minimize conductive energy loss. 
     All of these representative methods also can include using the embedded wire busbars to provide a temperature stable electrical connection. 
     All of these representative methods also can include connecting the embedded wire busbars to a power supply without rivets or hot spots. 
     All of these representative methods also can include using a PEDOT conductive transparent coatings on the embedded wire busbars. 
     All of these representative methods also can include coating the embedded wire busbars and using the coated embedded wire busbars as a transparent electric heater. 
     Further broad aspects of the present disclosure include devices and machines for manufacturing the three-dimensional busbars taught in this disclosure. Representative embodiments of such a device for manufacturing three-dimensional busbars include a device for manufacturing three-dimensional busbars on a three-dimensional substrate for use as a three dimensional heater, the device including means for constructing intermittent contact busbars on the three-dimensional substrate, wherein the three-dimensional heater comprises the busbars, which are electrically conductive, and dielectric coatings so as to have an intermittent electrical contact with a conductive film on the surface of the three-dimensional substrate, thereby providing uniform heating of the three-dimensional substrate suing the three dimensional heater. 
     Similarly, further broad aspects of the present disclosure include using the methods and/or devices and machines disclosed herein to produce apparatuses such as goggles and visors, as well as the goggles and visors produced thereby. Such methods of use can be accomplished using any of the representative methods, devices, and/or machines disclosed herein, or combinations of any of the representative methods, devices, and/or machines disclosed herein. Likewise, such apparatuses can be produced or otherwise made or manufactured using any of the representative methods, devices, and/or machines disclosed herein, or combinations of any of the representative methods, devices, and/or machines disclosed herein. As used in this disclosure, the terms “goggles” and “visors” are used as representative terms for all appropriate eyewear and eye coverings, including, but not limited to, goggles, visors, eyeglasses, face screens, face masks, eye masks, lenses, and the like. 
     Similarly, further broad aspects of the present disclosure include using the methods and/or devices and machines disclosed herein to produce apparatuses such as transparent shields, as well as the shields produced thereby. Such methods of use can be accomplished using any of the representative methods, devices, and/or machines disclosed herein, or combinations of any of the representative methods, devices, and/or machines disclosed herein. Likewise, such apparatuses can be produced or otherwise made or manufactured using any of the representative methods, devices, and/or machines disclosed herein, or combinations of any of the representative methods, devices, and/or machines disclosed herein. As used in this disclosure, the term “shield” is used as a representative term for all appropriate transparent and heated barriers, including, but not limited to, windshields, car windows, windows for buildings, windows for refrigerated storage rooms, etcetera. 
     Similarly, further broad aspects of the present disclosure include using the methods and/or devices and machines disclosed herein to produce apparatuses such as mirrors (where a reflective layer may be added to the substrate providing shape to the mirror), as well as the mirrors produced thereby. Such methods of use can be accomplished using any of the representative methods, devices, and/or machines disclosed herein, or combinations of any of the representative methods, devices, and/or machines disclosed herein. Likewise, such apparatuses can be produced or otherwise made or manufactured using any of the representative methods, devices, and/or machines disclosed herein, or combinations of any of the representative methods, devices, and/or machines disclosed herein. 
     Another broad aspect is a system for providing uniform heating across a transparent or mirrored surface of non-uniform width. The system includes a base substrate defining a shape of the surface, a thin conductive material applied to the base substrate, busbars applied to the thin conductive material, wherein a first busbar of the busbars is applied to or next to a first edge of the surface and a second busbar of the busbars is applied to or next to a second edge of the surface opposite the first edge, and wherein uniform heating is achieved through one of: a dielectric material positioned between the busbars and thin conductive material to enable intermittent contact between the busbars and the thin conductive material; and at least one of holes, voids and dots applied to the thin conductive material to alter resistivity across a surface defined by the thin conductive material, wherein more of the at least one of holes, voids and dots are present when the busbars are closer together than when the busbars are farther apart. The system may be included in a heated lens. The system may be included in a heated shield. 
     In the present disclosure, the viewing area of the goggles or visor preferably has a ΔT of 25° C. relative to the ambient temperature so as to melt any snow or frost on the goggle or visor, but in prior art, the smaller area of the goggles above the user&#39;s nose may have a ΔT of 100° C. or more, which could damage the goggles or visor coating and/or substrate. Such a large ΔT also means that if the energy is supplied from a battery source, then the goggles or visor will require larger batteries and/or provide less uninterrupted heating time. In addition, prior art conductive silver busbars must be large enough to prevent energy loss and therefore will limit the size of the viewing area. Even with M” wide silver busbars at the top and bottom of the visor, such as used in prior art helmet shields, to 40% of the energy is lost in the heating of the busbars depending on sheet resistance or conductivity of the transparent conductor. In addition, a mechanical electric connection of the wires from the power source to the busbars using a rivet causes hot spots at the connection and is not as secure as soldered copper or other fastener options, which would be a more robust connection for skiing, snowmobiling, or other activities which involve significant vibration. In addition, the rivet connection Is expensive and time consuming. These and other design flaws will be solved by the following designs. 
     A broad aspect is a method for heating a surface, comprising using conductive continuous busbars and transparent dielectric coatings so as to have an intermittent electrical contact with a conductive film to provide heating, wherein the intermittent electrical contact is determined by non-contact spacing M, wherein non-contact spacing M used to provide heating between busbars is determined by the equation 
     
       
         
           
             
               M 
               = 
               
                 
                   
                     ( 
                     
                       
                         L 
                         ⁢ 
                         1 
                       
                       
                         L 
                         ⁢ 
                         2 
                       
                     
                     ) 
                   
                   2 
                 
                 ⁢ 
                     
                 w 
                 - 
                 w 
               
             
             , 
           
         
       
     
     where L1 is a first linear path across the surfaces between busbars, L1 being the longest vertical path between the busbars when the busbars are located along a top edge and a bottom edge of the surface, L2 is any second linear path across the surface between busbars, L2 being shorter than and parallel to L1, and w is the width of a busbar contact region, and wherein contact between the conductive film and each of the busbars is continuous except where a dielectric coating underneath the busbar prevents electrical contact between the busbar and the conductive film. 
     In some embodiments, the busbars may be parallel to each other. 
     In some embodiments, the busbars may not be parallel to each other. 
     In some embodiments, the conductive film may be transparent. 
     In some embodiments, the dielectric coating may be continuous, preventing a continuous busbar over the dielectric coatings from contacting the conductive film except where the busbar protrudes past the dielectric coating making contact with the conductive film. 
     In some embodiments, each of the busbars may be bonded with a conductive adhesive to a copper foil, wherein the respective one of the busbars and the copper foil may be laminated together. 
     In some embodiments, the copper foil may be soldered to a power supply. 
     In some embodiments, where the method may include using a tapered or decreasing width busbar for uniform resistance heaters. 
     In some embodiments, wherein the method may be for use in constructing intermittent contact busbars for three-dimensional transparent conductive heaters. 
     A broad aspect is a method for heating a surface of a heater with busbars contacting a conductive heating material by varying sheet resistivity to generate uniform heating across the surface, wherein the sheet resistivity ρ2 of the conductive heater material as a function of width of the surface is determined using the equation 
     
       
         
           
             ρ2 
             = 
             
               ρ 
               ⁢ 
               1 
               ⁢ 
               
                 
                   ( 
                   
                     
                       L 
                       ⁢ 
                       1 
                     
                     
                       L 
                       ⁢ 
                       2 
                     
                   
                   ) 
                 
                 2 
               
             
           
         
       
     
     for the heating, wherein L1 is a first linear path across the surfaces between busbars, L1 being the longest vertical path between busbars where a first busbar of the busbars is located along a top edge and a second busbar of the busbars is located along a bottom edge of the surface, L2 is any second linear path across the surface between busbars, L2 being shorter than and parallel to L1, and ρ1 is the initial sheet resistivity of the conductive heater material on the heater surface. 
     In some embodiments, the busbars may be parallel to each other. 
     In some embodiments, the method may include using voids or holes in the conductive heater material to increase sheet resistivity. 
     In some embodiments, the method may include using conductive dots on the conductive heater material to decrease sheet resistivity. 
     In some embodiments, the method may include using a combination of conductive dots and voids or holes to give a variation of sheet resistivity. 
     A broad aspect, a device for manufacturing three-dimensional busbars, wherein the device includes means for constructing intermittent contact busbars on a three-dimensional transparent conductive heater, wherein the three-dimensional transparent conductive heater comprises the busbars, which are electrically conductive, and dielectric coatings so as to have an intermittent electrical contact with a conductive film, thereby providing heating of the three-dimensional transparent conductive heater, wherein the intermittent electrical contact is determined by non-contact spacing M, wherein the non-contact spacing M used to provide heating between busbars is determined by the equation 
     
       
         
           
             
               M 
               = 
               
                 
                   
                     ( 
                     
                       
                         L 
                         ⁢ 
                         1 
                       
                       
                         L 
                         ⁢ 
                         2 
                       
                     
                     ) 
                   
                   2 
                 
                 ⁢ 
                     
                 w 
                 - 
                 w 
               
             
             , 
           
         
       
     
     where L1 is a first linear path across the surfaces between the busbars, L1 being the longest vertical path between the busbars when the busbars are located along a top edge and a bottom edge of the surface, L2 is any second linear path across the surface between the busbars, L2 being shorter than and parallel to L1, and w is the width of a busbar contact region, and wherein contact between the conductive film and each of the busbars is continuous except where a dielectric coating underneath the busbars prevents electrical contact between the busbars and the conductive film. 
     Another broad aspect is goggles comprising a lens heated using a method for heating of a lens, the method including using electrically conductive busbars and dielectric coatings so as to have an intermittent electrical contact with a conductive film coated on a surface of the lens so as to provide heating of the lens, wherein the intermittent electrical contact is determined by non-contact spacing M, wherein the non-contact spacing M used to provide heating between busbars is determined by the equation 
     
       
         
           
             
               M 
               = 
               
                 
                   
                     ( 
                     
                       
                         L 
                         ⁢ 
                         1 
                       
                       
                         L 
                         ⁢ 
                         2 
                       
                     
                     ) 
                   
                   2 
                 
                 ⁢ 
                     
                 w 
                 - 
                 w 
               
             
             , 
           
         
       
     
     where L1 is a first linear path across the surfaces between busbars, L1 being the longest vertical path between the busbars when the busbars are located along a top edge and a bottom edge of the surface, L2 is any second linear path across the surface between the busbars, L2 being shorter than and parallel to L1, and W is the width of a busbar contact region, and wherein contact between the conductive film and each of the busbars is continuous except where a dielectric coating underneath the busbars prevents electrical contact between the busbars and the conductive film. 
     Another broad aspect is a system for providing heating across a transparent or mirrored surface of non-uniform width, including a base substrate defining a shape of the surface; a thin conductive material applied to the base substrate; and busbars applied to the thin conductive material, wherein a first busbar of the busbars is applied to or next to a first edge of the surface and a second busbar of the busbars is applied to or next to a second edge of the surface opposite the first edge, wherein the heating is achieved through one of a dielectric material positioned between the busbars and the thin conductive material to enable intermittent contact between the busbars and the thin conductive material wherein the intermittent electrical contact is determined by non-contact spacing M, wherein the non-contact spacing M used to provide the heating between busbars is determined by the equation 
     
       
         
           
             
               M 
               = 
               
                 
                   
                     ( 
                     
                       
                         L 
                         ⁢ 
                         1 
                       
                       
                         L 
                         ⁢ 
                         2 
                       
                     
                     ) 
                   
                   2 
                 
                 ⁢ 
                     
                 w 
                 - 
                 w 
               
             
             , 
           
         
       
     
     where L1 is a first linear path across the surfaces between busbars, L1 being the longest vertical path between busbars when busbars are located along a top edge and a bottom edge of the surface, L2 is any second linear path across the surface between busbars, L2 being shorter than and parallel to L1, and W is the width of a busbar contact region, and wherein contact between the conductive film and the busbars is continuous except where a dielectric coating underneath the busbars prevents electrical contact between the busbars and the conductive film, and at least one of holes, voids, and dots applied to the thin conductive material to alter sheet resistivity across a surface defined by the thin conductive material, wherein at least one of: at least one of holes and voids are added to increase sheet resistivity, and at least one of dots are added to decrease sheet resistivity, and wherein the sheet resistivity ρ2 of the conductive heater material as a function of width of the surface is determined using the equation 
     
       
         
           
             ρ2 
             = 
             
               ρ 
               ⁢ 
               1 
               ⁢ 
               
                 
                   ( 
                   
                     
                       L 
                       ⁢ 
                       1 
                     
                     
                       L 
                       ⁢ 
                       2 
                     
                   
                   ) 
                 
                 2 
               
             
           
         
       
     
     for the heating, wherein L1 is a first linear path across the surfaces between busbars, L1 being the longest vertical path between busbars where a first busbar of the busbars is located along a top edge and a second busbar of the busbars is located along a bottom edge of the surface, L2 is any second linear path across the surface between busbars, L2 being shorter than and parallel to L1, and ρ1 is the initial sheet resistivity of the conductive heater material on the heater surface. 
     In some embodiments, the system may be applied to a heated lens. 
     In some embodiments, the system may be applied to a heat shield. 
     In some embodiments, the system may include cracking or scoring the dielectric coating to disrupt current flow with minimal visual changes in the dielectric coating. 
     In some embodiments, a knife die may be used for the cracking or scoring the dielectric coating. 
     In some embodiments, various shapes of the knife die may be used to create electrically isolated areas on the dielectric coating. 
     In some embodiments, the cracking or scoring of the dielectric coating to disrupt current flow may result in unheated areas in critical parts of the surface to prevent over-heating. 
     In some embodiments, the method may include using the unheated areas to provide more current and heating into a portion of the surface, wherein the portion of the surface may be a large viewing area portion of the surface. 
     Another broad aspect is a method of using laser cuts or knife dies to disrupt conductivity and create unheated zones in a clear dielectric material located between busbars on a surface. 
     Another broad aspect is a method of using laser cuts or knife dies to punch holes in a polyester film and then vapor coating the polyester film with a dielectric coating, thereby resulting in holes in the dielectric corresponding to the holes in the polyester film. 
     In some embodiments, the holes on the vapor coated dielectric coating on polyester film may be used to change sheet resistivity. 
     In some embodiments, the equation 
     
       
         
           
             ρ 
             = 
             
               
                 ρ 
                 ⁡ 
                 ( 
                 
                   
                     L 
                     ⁢ 
                     1 
                   
                   
                     L 
                     ⁢ 
                     2 
                   
                 
                 ) 
               
               ⁢ 
               2 
             
           
         
       
     
     may be used to determine the holes area to decrease the sheet resistivity on the surface so as to result in more uniform heating. 
     Another broad aspect is a method of heating a surface comprising using embedded wires within a dielectric coating and polycarbonate substrate sandwich and a thin silver connection to obtain conductive busbars. 
     In some embodiments, the method may include locating the embedded wire busbars so as to maximize a viewing area through the surface. 
     In some embodiments, the method may include using the embedded wire busbars so as to minimize conductive energy loss. 
     In some embodiments, the method may include using the embedded wire busbars to provide a temperature stable electrical connection. 
     In some embodiments, the embedded wire busbars may be connected to a power supply without rivets or hot spots. 
     In some embodiments, the method may include using a Poly(3,4-ethylenedioxythiophene) conductive transparent coating on the embedded wire busbars. 
     In some embodiments, the method may include coating the embedded wire busbars and using the coated embedded wire busbars as a transparent electric heater. 
     Another broad aspect is a transparent or mirrored heated material of non-uniform width that minimizes the presence of hot spots across a surface of the material, the material including a substrate layer defining the shape of the surface; a conductive film layered over the substrate layer; two busbars, where a first busbar is positioned at a top outer edge of the surface and the second busbar is positioned at a bottom outer edge of the surface, wherein a contact between the two busbars and the conductive film is intermittent through the use of a dielectric coating positioned between the busbars and the conductive film, wherein a width of non-contact portions between the conductive film and the busbars as a result of the dielectric coating increases as a function of a decrease in a distance defined by a linear path between the two busbars, and wherein a width of contact portions between the busbars and the conductive film, is constant. 
     In some embodiments, the conductive film may be indium tin oxide. 
     In some embodiments, the dielectric coating may include a plurality of dielectric spacers that are positioned intermittently between the busbars and the conductive film, and wherein the width of the plurality of dielectric spacers, defining the width of the non-contact portions, may increase as a function of a decrease in the distance defined by a linear path between the two busbars. 
     In some embodiments, the dielectric coating may prevent a continuous busbar from contacting the conductive film except where the busbar protrudes past the dielectric coating making contact with the conductive film. 
     In some embodiments, the busbars may be imbedded in the substrate. 
     In some embodiments, the embedded busbars may be coated with a conductive material for improving a contact between the embedded busbars and the conductive film. 
     Another broad aspect are heated goggles comprising a lens composed of the material as defined herein. 
     Another broad aspect is a helmet comprising a visor composed of the material as defined herein. 
     Another broad aspect is a transparent or mirrored heated material of non-uniform width that minimizes the presence of hot spots across a surface of the material comprising a substrate layer defining the shape of the surface; a conductive film layered over the substrate layer; two busbars, where a first busbar is positioned at a top outer edge of the surface and the second busbar is positioned at a bottom outer edge of the surface, wherein sheet resistivity of the conductive film varies as a function of a distance defined by a linear path between the two busbars, wherein the sheet resistivity increases as the distance defined by a linear path between the two busbars decreases in order to improve uniform heating across the surface. 
     In some embodiments, the sheet resistivity may be increased by providing voids or holes in the conductive film, and wherein at least one of the number and density of the voids and holes may increase as the distance defined by a linear path between the two busbars decreases. 
     In some embodiments, the sheet resistivity may be decreased by providing conductive dots in the conductive film, and wherein at least one of the number and density of the dots may increase as the distance defined by a linear path between the two busbars increases. 
     Another broad aspect are heated goggles comprising a lens composed of the material as defined herein. 
     Another broad aspect is a helmet comprising a visor composed of the material as defined herein. 
     Another broad aspect is a lens configured for uniform heating comprising a substrate layer defining a shape of the lens; a conductive film applied to the substrate layer; busbars imbedded in the substrate layer at given intervals across the substrate layer, wherein the imbedded busbars contact the conductive film; and a coating of a conductive material applied to the busbars to improve contact between the busbars and the conductive film. 
     In some embodiments, the busbars may be transparent. 
     In some embodiments, the substrate layer may include a top half and a bottom half, and wherein the busbars are embedded in the substrate layer by being sandwiched between the top half and the bottom half. 
     In some embodiments, the busbars may be embedded in the substrate layer by passing current through the busbars, causing the busbars to heat and melt the substrate layer, resulting in busbars embedding in the substrate layer. 
     In some embodiments, the substrate layer may be polycarbonate. 
     In some embodiments, the substrate layer may have a non-uniform width, and wherein the busbars may follow the shape of the lens. 
     Another broad aspect are goggles including the lens as defined herein. 
     Another broad aspect is a helmet comprising the lens as defined herein. 
     Another broad aspect is an all-terrain vehicle comprising the lens as defined herein. 
     In some embodiments, the all-terrain vehicle may be a side-by-side vehicle. 
     Another broad aspect is a uniformly-heated shield for at least one of defogging and de-icing including a substrate layer defining a shape of the shield; a plurality of wire heaters spaced at given intervals across a width or a length of the substrate layer, the plurality of wire heaters embedded in the wire heaters; and two busbars positioned at opposite ends of the substrate layer and normal to each of the plurality of wire heaters, connected to each of the plurality of wire heaters, wherein each of the two busbars are connected to or connectable to a power source that provides for current to pass through the two busbars and the plurality of wire heaters, where the plurality of wire heaters produce heat for at least one of defogging and de-icing when current passes therethrough. 
     In some embodiments, each of the wire heaters of the plurality of wire heaters may be made from copper and is tinned. 
     In some embodiments, the substrate layer may be composed of polycarbonate. 
     Another broad aspect is a land vehicle comprising the shield as defined herein. 
     This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. 
     These features, and other features and advantages of the present disclosure will become more apparent to those of ordinary skill in the relevant art when the following detailed description of the preferred embodiments is read in conjunction with the appended drawings in which like reference numerals represent like components throughout the several views. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features and advantages of the present teachings will become apparent from the following description taken in connection with the accompanying drawings. 
         FIG.  1    is a schematic of a prior art ITO lens and connections used for defogging goggles and visors. 
         FIG.  2    is a schematic of and derivations of Watt density for parallel busbars separated by distance L. 
         FIG.  3 A  is a front view of an exemplary portion of a lens configured implementing a first method of providing intermittent electrical connection with transparent conductive film using clear dielectric printed elements and continuous printed (silk-screened) silver busbars incorporating the present teachings. 
         FIG.  3 B  is a side view of the exemplary portion of the lens of  FIG.  3 A  implementing the first method of providing intermittent electrical connection with transparent conductive film using clear dielectric printed elements and continuous printed (silk-screened) silver busbars incorporating the present teachings. 
         FIG.  3 C  is a front view of an exemplary portion of a lens configured implementing a second method of providing intermittent electrical connection with transparent conductive film using clear dielectric printed elements and continuous printed (silk-screened) silver busbars incorporating the present teachings. 
         FIG.  3 D  is a side view of the exemplary portion of the lens of  FIG.  3 C  implementing the second method of providing intermittent electrical connection with transparent conductive film using clear dielectric printed elements and continuous printed (silk-screened) silver busbars incorporating the present teachings. 
         FIG.  4 A  is a front view schematic of an exemplary derivation of dielectric spacing and electric contact spacing to have uniform heating of the present teachings. 
         FIG.  4 B  is a side view schematic of the exemplary derivation of  FIG.  4 A  of dielectric spacing and electric contact spacing to have uniform heating of the present teachings. 
         FIG.  5    is a schematic of and computation of an exemplary dielectric and silver busbar spacing and contact for defogging of a goggle, visor, or other device incorporating the present teachings. 
         FIG.  6    is a schematic illustrating exemplary resistance distribution when using tapered busbars for more efficient use of silver and a better viewing area provided by the present teachings. 
         FIG.  7 A  is a schematic of top view of carbon underfloor heaters and busbars. 
         FIG.  7 B  is a side view schematic of the prior art carbon underfloor heaters and busbars shown in  FIG.  7 A . 
         FIG.  8 A  is a schematic of a front view of an exemplary first type of vacuum formed conductive transparent three-dimensional shapes and busbars for defogging using the present teachings. 
         FIG.  8 B  is a cross-section of the exemplary first type of vacuum formed conductive transparent three-dimensional shapes and busbars of  FIG.  8 A  for defogging using the present teachings. 
         FIG.  8 C  is a schematic of a top cross-sectional view of an exemplary second type of vacuum formed conductive transparent three-dimensional shapes and busbars for defogging using the present method for printing busbars. 
         FIG.  9 A  is a schematic of an exemplary first device and method for providing uniform heating with odd-shaped heaters using an intermittently spaced carbon conductor and uniform busbars using the present teachings. 
         FIG.  9 B  is a schematic of an exemplary second device and method for providing uniform heating with odd shaped heaters using a dielectric and uniform busbars using the present teachings. 
         FIG.  9 C  is a schematic of an exemplary third device and method for providing uniform heating with odd shaped heaters using a variable sheet resistance and uniform busbars using the present teachings. 
         FIG.  10    is a schematic of a prior art ITO lens with busbars and connections used for defogging goggles and visors. 
         FIG.  11    is a schematic view of an exemplary ITO lens with a scored electrically discontinuous ITO portion using the present teachings. 
         FIG.  12    is a schematic view of an exemplary ITO lens using scored ITO in combination with printed clear dielectric to provide electrically isolated cold zone using the present teachings. 
         FIG.  13    is a schematic view of an exemplary ITO lens using laser cut or die cut holes in the ITO in combination with printed clear dielectric to provide electrically isolated cold zone using the present teachings. 
         FIG.  14    is a perspective schematic view of an exemplary ITO/polycarbonate sandwich using the present teachings. 
         FIG.  15    is a perspective schematic view of an exemplary ITO/polycarbonate lens showing a silver/copper wire and silver connecting trace using the present teachings. 
         FIG.  16    is a sectional side schematic of an exemplary ITO/polycarbonate lens showing embedded silver/copper wire busbars and a coating of transparent PEDOT conductive polymer on a transparent polycarbonate substrate using the present teachings. 
         FIG.  17    is a thermograph of a prior art printed lens such shown in  FIG.  10    illustrating an electrically isolated cold zone created using a 10-volt input at an ambient temperature of 22° C. 
         FIG.  18    is a thermograph of a continuously scored lens such shown in  FIG.  12    illustrating an electrically isolated cold zone created using a 10-volt input at an ambient temperature of 22° C.; and 
         FIG.  19    is a drawing of a top-down view of an exemplary shield with imbedded wire heaters in accordance with the present teachings. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to those embodiments. On the contrary, the invention is intended to cover alternatives, modifications, and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. Those of ordinary skill in the art would understand that “busbars”, “coatings”, and “sheet resistivity” are terms known in the industry such that these terms would not be limited to the means explicitly disclosed in this specification. 
       FIG.  1    shows an existing design of a lens for heated goggles. A uniform coating of conductive material on a polymer film is shown on the lens. Typically, Indium Tin Oxide (ITO) is used as the coating  5 . However, other transparent conductive materials can be used as the coating, such as, but not limited to, other transparent conducting oxides (TCO), graphene, carbon nanotubes, and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), to name a few. The lens substrate may be a clear material, such as, but not limited to, polymer, glass, or ceramic, to name a few. 
     The coating  5  may have a range of sheet resistivity of 10-60 Ohm/□, and preferably 10-45 Ohm/□, preferably using a 10-12-volt power source. The more conductive the conductive material, the lower the power voltage source needed. For the exemplary embodiments disclosed herein, the coating  5  is applied to the lens substrate using a suitable technique, such as, but not limited to, sputtering, chemical vapor deposition, and sol-gel, to name a few. 
     Conductive silver busbars  4  are applied along the top of the lens and along the bottom of the lens for providing electrical power to the coating  5 . The busbars  4  are printed using an ink with a typical resistivity of 0.15 Ohms/□. Note that in this innovative design the lower busbar  4  is discontinuous, therefore requiring multiple electrical connections between the busbar(s)  4  and the power source  6 . For example, three electrical connections  1 ,  2 ,  3  are shown in the example embodiment of  FIG.  1   , one to the single top busbar  4 , and one each to the two lower busbars  4 . Some type of wiring is required from the power source  6  to the busbars  4 , using rivets to attach wires. Some designs use a continuous uniform width of busbars  4 , that attach to some power source  6  or battery. The busbars  4  can be applied to the lens substrate using a suitable technique, such as, but not limited to, printing, silk-screening, and using an inkjet type of printer, to name a few. 
     In the exemplary lens of  FIG.  1   , power, typically from a battery or other similar power source  6 , is applied to the busbars  4 . This power is conducted across the uniform coating  5  of conductive material and therefore across the lens, causing the coating  5  to heat up, therefore defogging or de-icing the lens. The power source  6  can be any suitable power source, such as, but not limited to, batteries, solar cells, and from an engine or battery of a snowmobile or other machine, to name a few. 
     In a typical prior art goggle or lens, the distance Lx (also referred to as the width herein) between the upper busbar  4  and the lower busbar  4  bar varies depending on the design. For example, as shown in  FIG.  1    for a common lens design, the distance L2 is about one-half the distance L1. This can lead to an extremely high temperature in the L2 zone—hot enough at room temperature to be extremely uncomfortable to the touch and produce distortion and wasted energy. This high non-uniform temperature would require a bulky expensive battery adding cost to the product. 
       FIG.  2    is a generalized schematic showing the theory behind the heating of a coating  5  using busbars  8 ,  9 , the coating  5  being a uniform conductive material  10  on a lens. In this schematic, the busbars  8 ,  9  are formed on a lens or other surface having a width W and are separated by some distance L. The resistance R to the applied voltage (V) is 
     
       
         
           
             R 
             = 
             
               ρ 
               ⁢ 
               
                 L 
                 W 
               
             
           
         
       
     
     where L is the length between busbars  8  and  9 , and ρ is the sheet resistance of the coating  5  in Ohms/□. The power in Watts is I 2 R where I is the current amps. As 
     
       
         
           
             
               I 
               = 
               
                 V 
                 R 
               
             
             , 
           
         
       
     
     the power 
     
       
         
           
             P 
             = 
             
               
                 
                   
                     ( 
                     
                       v 
                       R 
                     
                     ) 
                   
                   2 
                 
                 ⁢ 
                 ρ 
               
               = 
               
                 
                   
                     
                       V 
                       2 
                     
                     ⁢ 
                     W 
                   
                   
                     ρ 
                     ⁢ 
                     L 
                   
                 
                 . 
               
             
           
         
       
     
     The power density is 
     
       
         
           
             
               P 
               ⁢ 
               ρ 
             
             = 
             
               
                 
                   V 
                   2 
                 
                 ⁢ 
                 W 
               
               
                 ρ 
                 ⁢ 
                 
                   L 
                   ⁡ 
                   ( 
                   WL 
                   ) 
                 
               
             
           
         
       
     
     where (WL) is the area so the power density is 
     
       
         
           
             
               P 
               ⁢ 
               ρ 
             
             = 
             
               
                 V 
                 2 
               
               
                 ρ 
                 ⁢ 
                 
                   L 
                   2 
                 
               
             
           
         
       
     
     or Watts/□. Depending on the free convection constant K, it can be said that the ΔT the temperature rise equation is equation (1) 
     
       
         
           
             
               Δ 
               ⁢ 
               T 
             
             = 
             
               K 
               ⁢ 
               
                 
                   
                     V 
                     2 
                   
                   
                     ρ 
                     ⁢ 
                     
                       L 
                       2 
                     
                   
                 
                 . 
               
             
           
         
       
     
     Based on the above, it can be seen that in  FIG.  1    where L 2  is approximately one-half of L 1 , the temperature rise ΔT of the uniform conductive material  10  when power is applied between the busbars  8 ,  9  and across the uniform conductive material  10  will be four times greater than when L 2  is equal to L 1 . This can severely limit the function of the goggles if, for example, it is snowing at −20° C. or lower. The viewing area L 1  preferably has a ΔT=25° C. so as to melt the snow, but if L 2  is approximately one-half of L 1 , L 2  would have a ΔT=100° C., which at room temperature could distort or destroy the goggles. A range for ΔT can be from about 10° C. to about 40° C. such that the temperature of the goggles is brought up to an actual temperature sufficient to defog/deice the goggles. More specifically, the ΔT should be sufficient to bring the temperature of the goggles to an actual temperature sufficient to defog/deice the goggles. 
     To avoid these problems, the present teachings contemplate providing an intermittent electrical contact with a transparent dielectric material  13  while still providing a continuous busbar  4  as shown in  FIGS.  3 A and  3 B . 
       FIG.  3 A  is a front view and  FIG.  3 B  is a side view of a portion of an exemplary lens implementing a first method of providing intermittent electrical connection with a transparent conductive film  11  using clear dielectric material  13  as printed elements and printed (silk-screened) silver busbars  14  incorporating the present teachings. More specifically,  FIGS.  3 A and  3 B  show a continuous clear dielectric material  13  printed on the conductive material  11 , which is ITO deposited on some optically clear polymer film  12 . A continuous layer of silver conductive busbar  4  is printed with a small segment of busbar  14  extending over the dielectric material  13  and making electrical contact with the ITO. In the example shown in  FIGS.  3 A and  3 B , the base is polymer  12 . Completely coating the polymer  12  base is the conductive material  11 . Next, the dielectric material  13  is coated over the conductive material  11 . As shown, the dielectric material  13  is a continuous strip on the conductive material  11  over the entire width from left to right in  FIG.  3 A . Next is the silver busbar  14  on top of the dielectric material  13 , silver busbar  4  being entirely on top of the dielectric material  13  and not touching the conductive material  11  except for the small segments of busbar  14  touching the conductive material  11  as shown in  FIGS.  3 A and  3 B . The layers of construction of this first method are shown in the side view of  FIG.  3 B . 
       FIG.  3 C  is a front view and  FIG.  3 D  is a side view of a portion of an exemplary lens implementing a second method of providing intermittent electrical connection with a transparent conductive film  11  using clear dielectric material  13  as printed elements and printed (silk-screened) silver busbars  4  incorporating the present teachings. More specifically,  FIGS.  3 C and  3 D  show an alternate and preferred way of making intermittent contact, as this structure uses less dielectric material  13  and less silver busbar  4 ,  14  material than, for example, the lens shown in  FIGS.  3 A and  3 B . Here, a transparent dielectric material  13  is printed in busbar segment  14  as so to prevent electrical contact of the continuous printed busbars  4  from making electrical contact with the ITO conductive film  11 . The dielectric material  13  is preferably transparent so as to not interfere with the user&#39;s vision through the goggles. The dielectric material  13  is shown as discontinuous portions (e.g. squares) on the conductive material  11  so as to not allow contact between the silver busbar  14  and the conductive material  11 . Next is the silver busbar  14  on top of the dielectric material  13  squares and also partially on top of the conductive material  11 . The small segments  14  shown in  FIGS.  3 A and  3 B  touching the conductive material  11  are generally the equivalent of the areas  14  shown in  FIG.  3 C  that is not on top of the dielectric squares  13  and that is touching the conductive material  11 . The layers of construction of this lens implementing the second method are shown in the side view of  FIG.  3 D . 
       FIG.  4 A  is a front view and  FIG.  4 B  is a side view schematic of and derivation of the spacing of the dielectric material  24  and the spacing of the electric contact so as to have uniform heating of the present teachings. The example structure shown in  FIGS.  4 A and  4 B  has the same general structure as the structure shown in  FIGS.  3 C and  3 D .  FIGS.  4 A and  4 B  show the continuous busbars  25  printed over clear dielectric material  24 , connected to a voltage power supply  21 , with the busbars having intermittent contact with the conductive material  23  due to the presence of the (squares of the) dielectric material  24 . The heating or Watt density 
     
       
         
           
             
               
                 
                   V 
                   2 
                 
                 
                   ρ 
                   ⁢ 
                   
                     L 
                     2 
                     2 
                   
                 
               
               ⁢ 
               
                 ( 
                 
                   W 
                   
                     W 
                     + 
                     M 
                   
                 
                 ) 
               
             
             = 
             
               P 
               . 
             
           
         
       
     
     The term 
     
       
         
           
             ( 
             
               W 
               
                 W 
                 + 
                 M 
               
             
             ) 
           
         
       
     
     is the percent Watt density from the heated zone W spread over the unheated zone M. It can be said that this average Watt density is equal to the Watt density of the longest and coolest spacing or distance between busbars  25  L 1   2  or 
     
       
         
           
             
               V 
               2 
             
             
               ρ 
               ⁢ 
               
                 L 
                 1 
                 2 
               
             
           
         
       
     
     giving us the equation 
     
       
         
           
             
               
                 
                   
                     V 
                     2 
                   
                   
                     ρ 
                     ⁢ 
                     
                       L 
                       1 
                       2 
                     
                   
                 
                 ⁢ 
                 
                   ( 
                   
                     W 
                     
                       W 
                       + 
                       M 
                     
                   
                   ) 
                 
               
               = 
               
                 
                   V 
                   2 
                 
                 
                   ρ 
                   ⁢ 
                   
                     L 
                     2 
                     2 
                   
                 
               
             
             , 
           
         
       
     
     which results in equation (2) 
     
       
         
           
             M 
             = 
             
               
                 
                   ( 
                   
                     
                       L 
                       ⁢ 
                       1 
                     
                     
                       L 
                       ⁢ 
                       2 
                     
                   
                   ) 
                 
                 2 
               
               ⁢ 
               W 
               - 
               W 
             
           
         
       
     
     where M is the non-contacting distance (unheated zone) between contacting zones W (heated zone). For the purposes of equation (2), and as shown in the embodiments of  FIG.  1    for a common lens and of  FIG.  2    for a generalized lens, busbars  4  extend across at least a portion of the top and bottom edges of the lens in an overall horizontal orientation relative to each other (parallel busbars), and distances Lx in general and L 1  and L 2  in specific extend across the lens between busbars  4  in an overall vertical orientation, with each of distances Lx being parallel to each other in this overall vertical orientation. For busbars  4  not positioned in an overall horizontal position relative to each other (non-parallel busbars), one of ordinary skill in the art would be able to determine the orientation of distances Lx relative to the busbars  4 , such as being perpendicular to a center line extending equidistantly between the busbars  4 . 
     Arbitrary selection of some contacting distance of W and for some given distance of L between busbars  4 ,  25  can determine the non contacting or dielectric insulated distance. For an example of the contact zone W on the lens shown in  FIG.  1   , a contact zone W of 0.125″ can be selected. Note the smaller the contact zone the more uniform the Watt density. 
       FIG.  5    is a schematic of and computation of exemplary dielectric and silver busbar  4  spacing and contact for defogging of a goggle, visor, or other device or apparatus incorporating the present teachings. In  FIG.  5   , because the left and right parts of the lens are symmetrical, the spacing of non-contact zone M of the dielectric material is placed in the center with the 0.125″ contacts. The minimum contact length L is 1.5″ and the maximum contact length L 1  is 3″. Hence 
     
       
         
           
             
               
                 [ 
                 
                   
                     
                       ( 
                       
                         
                           L 
                           1 
                         
                         L 
                       
                       ) 
                     
                     2 
                   
                   ⁢ 
                   
                     ( 
                     
                       0.125 
                       ″ 
                     
                     ) 
                   
                 
                 ] 
               
               - 
               
                 0.125 
                 ″ 
               
             
             = 
             
               
                 0.375 
                 ″ 
               
               = 
               M 
             
           
         
       
     
     (for dielectric space  26 ). Using the same equation, the spacing for dielectric space  28  can be determined. M=0.156″ for dielectric space  29 ; M=0.100 for dielectric space  30 ; M=0.055″ for dielectric space  31 ; M=0.025″ for dielectric space  32 ; M=0.025″ for dielectric space  33 ; M=0.055″ for dielectric space  34 ; and M=0.100 for dielectric space  35 . 
     The non-contact spacing of each busbar  4  (upper and lower busbar  4 ), and therefore the contact spacing of each busbar  4 , mirrors one another. 
     The contact zone W is 0.125″ and is constant. Also shown in  FIG.  5    is where the applied voltage of power source  39  is in contact at connection point  40  and connection point  41 , respectively. 
     The calculation for the dielectric spacing M was performed in the areas of the lens that would have the hottest zones. A prototype was constructed using the dimensions provided above for M and W, was tested, and the lens was essentially uniformly heated. More specifically, the computing of dielectric spacing M, contact spacing W, and silver busbar  4  spacing for defogging of a goggle, visor, or other device as shown in  FIG.  5    is provided below. This is constant for the temperature rise ΔT as a function of Watt density. The average temperature across L is relatively uniform, but can vary. The actual temperature across the surface of the lens is not critical as long as the T over the lens is greater than a T that will defog or deice the optical area of the device. 
     Converting Watt density to ΔT, the conversion is measured as K=0.023 W/0° C./in 2 . If a 25° C. rise or ΔT for the longest distance L 1 =2″ for 45 Ohm/□ ITO is sought, it can be said that 
                 V   2         (     2   2     )     ×   45       =         (     2   ⁢   5     )     .   0     ⁢   2   ⁢     3   .               V =√{square root over ((4)(45)(25).023)}= 10 . 17 Volts
 
     The 
     
       
         
           
             
               Watt 
               ⁢ 
                   
               density 
             
             = 
             
               
                 
                   V 
                   2 
                 
                 
                   
                     
                       ( 
                       2 
                       ) 
                     
                     2 
                   
                   ⁢ 
                   45 
                 
               
               = 
               
                 
                   10.17 
                   
                     
                       ( 
                       4 
                       ) 
                     
                     ⁢ 
                     45 
                   
                 
                 = 
                 
                   0.57 
                   
                     Watt 
                     / 
                     
                       IN 
                       2 
                     
                   
                 
               
             
           
         
       
     
     Through use of intermittent contacts, which can be referred to as the spaces between the dielectric squares where the silver busbar touches the conductive film, and a uniform Watt density and temperature, the heated area (A) can be multiplied to determine the total Watts of 0.57  Watts /In (A). If this is divided by the voltage, 10.17V, the current can be determined to design the power supply. 
       FIG.  6    illustrates the resistance distribution and tapered busbars  4  for more efficient use of silver and a better viewing area provided by the present teachings. More specifically,  FIG.  6    represents the placement of busbars  4  and the various resistances R between the busbars  4  across the lens distance L. Once the intermittent connection and equation (2) is found, uniform resistance R across the busbars  4  is present, as shown in  FIG.  6   . Although R may vary somewhat across the lens, the average R will be the same across the entire width of the lens, with the Watt density being uniform across the lens. From inspection, it can be seen that the maximum current density is at connection points  42  and  44 . The current density is at a minimum at endpoints  41  and  45 . So, tapered busbars  4  can be used. This minimizes the amount of printed silver, which saves cost, but more importantly allows for a larger viewing area. 
       FIG.  7 A  is a schematic front view of prior art carbon underfloor heater elements  48  and busbars  49 , and  FIG.  7 B  is a side view of the prior art device of  FIG.  7 A . In  FIGS.  7 A and  7 B , drawings of an underfloor heater are shown. Carbon resistive heating elements  48  are printed on a 0.005″ polyester film  51 . A silver busbar  49  is printed to provide an uninterrupted electrical connection with the heating elements  48 . A continuous metal strip about 0.005″ thick and 0.5″ wide  50  is in contact with the printed silver strip  49  and then adhesively laminated to the coated polyester film  51 . In some applications, such as a visor in helmets, large areas are heated using silver busbars  49  as mentioned earlier, and 30% of the energy is lost and a significant part of the viewing area is lost because the busbars  49  are 0.5″ wide. A comparison of the sheet resistivity that was computed from the bulk resistance of various metal and printed silvers is: 
     For 0.001″ thick copper, ρ=0.8×10 −3  Ohms/□
 
For 0.001″ aluminum, ρ=1.8×10 −3  Ohms/□
 
For 0.001″ steel, ρ=5.5×10 −3  Ohms/□
 
For printed silver, ρ=0.15 Ohms/□
 
     Clear thin copper is orders of magnitude more conductive than silver. A printed silver busbar only 0.5 mm wide and a copper foil 0.0254 mm thick and 0.5 mm wide bonded together with a conductive adhesive and then laminated with a clear pressure sensitive thin film will be a much more conductive busbar and will also allow for a greater viewing area without Joule heating loss. It will also replace the mechanical contact with a robust secure soldered connection to the voltage source. The difference between the busbar construction in underfloor heaters is the use of much thinner silver/copper busbars, because floor heaters must carry current over meters not centimeters. 
     Another significant difference in the floor heater, is that the busbars  49  make uninterrupted contact with conductive carbon heating elements  48  as opposed to the teachings of the present disclosure that describe the use of dielectric insulators to provide intermittent contact. 3M™ sells 0.0014-inch thick copper foil with a conductive adhesive that can be used for the present teachings. Another significant difference is while the floor heater uses continuous strips of metal conductors, due to the design shape the copper foil must be die cut to conform to the lens geometry. 
       FIGS.  8 A,  8 B, and  8 C  illustrate embodiments of the present disclosure as applied to three-dimensional shapes, such as rounded goggles  53 .  FIG.  8 A  is a schematic of a front view and  FIG.  8 B  is a cross-section of a first type of vacuum formed conductive transparent three-dimensional shape  53  and busbars  52  for defogging using the present teachings.  FIG.  8 C  is a schematic of a top cross-sectional view of a second type of vacuum formed conductive transparent three-dimensional shape  53  and busbars  52  for defogging using the present teachings. 
     In  FIGS.  8 A and  8 B , a three-dimensional transparent heat formable goggle lens  53  is shown. Transparent films using ITO are impossible to heat form because the ITO is a brittle ceramic. However, Chasm Corporation has developed heat formable transparent conductive films with sheet resistance varying from 10 Ohms/□ to 40 Ohms/□. However, in forming the film, the resistance will vary with the stretched film increasing in resistance. In addition, because of the shape of the surface  53 , the distance between busbars  52  will vary giving rise to non uniform heating. To overcome the variable, an intermittent busbar  52  is printed on the flat extended parts of the lens surface  53 . The eye of the viewer  55  is shown in  FIG.  8 B . For example, on the 3D lens shown in  FIGS.  8 A and  8 B , a dielectric may not be necessary towards the middle of the 3D structure, or the spacing of the dielectric may be closer towards the middle and wider towards the sides so that the Watt density across the middle of the 3D lens is the same as across the sides of the lens, as the distance across the 3D shape towards the middle of the lens is greater than the distance across the 3D shape towards the edges of the lens. In  FIG.  8 C , a fixture  54  (with holes) for holding many lenses is shown to facilitate silk screening silver busbars simultaneously for many lenses and reduced. 
     The method disclosed for varying the sheet resistance p to obtain uniform heating with nonparallel busbars can be used to provide non uniform heating. A method for obtaining uniform heating is shown in  FIGS.  9 A,  9 B, and  9 C  is a circular heater.  FIG.  9 A  is a schematic of a first device and method for providing uniform heating with odd shaped heaters and non uniform busbars using the present teachings.  FIG.  9 B  is a schematic of a second device and method for providing uniform heating with odd shaped heaters and non uniform busbars using the present teachings.  FIG.  9 C  is a schematic of a third device and method for providing uniform heating with odd shaped heaters and non uniform busbars using the present teachings. 
     In  FIG.  9 A , areas of a constant sheet resistance are printed on a substrate using uniform conductive material  61 . A space  57  is not printed. The spacing between printed segments  61  is determined by equation (2) 
     
       
         
           
             M 
             = 
             
               
                 
                   ( 
                   
                     
                       L 
                       ⁢ 
                       1 
                     
                     
                       L 
                       ⁢ 
                       2 
                     
                   
                   ) 
                 
                 2 
               
               ⁢ 
               W 
               - 
               
                 W 
                 . 
               
             
           
         
       
     
     Here again conductive segment  61  is 0.125″ wide. The busbar  60  is 0.125″ wide, which will give an approximate uniform heating. Again, if contact zone W is made smaller, the heating will get more uniform. 
     In  FIG.  9 B , the formula in equation (2) was again used to provide a dielectric coating to prevent current flow through dielectric coating  59 . A uniform constant sheet resistance p is provided for a uniform conductive material  61 . 
       FIG.  9 C  illustrates a preferred method of obtaining uniform heating by altering the sheet resistivity. Here the sheet resistivity is altered as shown in equation (3). If the Watt density of the longest path between busbars  60  and the various paths L 2  is set, equation (3) results: 
     
       
         
           
             
               
                 
                   
                     ρ 
                     2 
                   
                   = 
                   
                     
                       
                         ( 
                         
                           
                             L 
                             1 
                           
                           
                             L 
                             2 
                           
                         
                         ) 
                       
                       2 
                     
                     ⁢ 
                     
                       
                         ρ 
                         1 
                       
                       . 
                     
                   
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
           
         
       
     
     This means that for any given distance L 2 , the sheet resistivity ρ 2  can be increased so as to obtain uniform heating. 
     This can be accomplished by having voids  63  in a portion  62  of the conductive material. If one is printing a resistive uniform conductive material  62  so that as L decreases, there are progressively more voids  63  moving from the center of the shown odd shaped heater towards the outer edge of the shown odd shaped heater. In other words, there are fewer voids  63  and/or the voids  63  are spaced further apart (less dense) towards the center of the shown odd shaped heater (that is, closer to the uniform conductive material  61 ) and there are more voids  63  and/or the voids are spaced closer together (more dense) towards the edges of the odd shaped heater (that is, further from the uniform conductive material  61 ). This also is true if the conductive medium is a photo etched metal such as Manganin. If the voids  63  are 50% of the area, the sheet resistivity is 50% greater. 
     If the printed conductor has insufficient conductivity, a series of silver conductive dots can be printed over a carbon conductor, for example, to decrease the sheet resistivity in the longest distance L with decreasing silver dots as L 2  gets smaller. One can use a combination of voids  63  in or swiss cheese holes and silver to obtain a wide range of sheet resistivity. Although holes or similar voids  63  are suggested to increase the ρ, the sheet resistivity various geometries such as rectangular voids  63  can be used, but small holes or voids  63  are preferred so as to limit hot spots when the current flows around the voids  63 . The size of the voids  63  depends on the printing (e.g., silk screening, rotogravure) resolution. 
     As one of ordinary skill in the art would understand, as the sheet resistivity is altered to obtain uniform Watt density, it becomes a very simple matter to design a complex shape heater. The Watt density is multiplied by the area at the heater to obtain the total Watts. 
     A method of altering the temperature distribution on transparent ITO conductors is shown below in conjunction with  FIGS.  10 - 16   . As disclosed above, the present disclosure provides an equation for uniform sheet resistivity films with non-uniform, non-parallel busbars. The concept, inter alia, is used to prevent excessive heating in ski goggles, visors, etc. using ITO conductive film as shown generally in  FIG.  10   . 
       FIG.  10    shows a schematic of an existing ITO lens with busbars and connections used for defogging goggles and visors. In  FIG.  10   , L 2  is the shortest distance between printed silver busbars  103 , L 1  is the longest distance between busbars  103 , and an ITO coating  102  having conductive  30 - 45  Ω/□. A power source  107  provides electrical power to the system. The greatest heating occurs in the L 1  zone as the watt density (W) is equal to 
     
       
         
           
             
               
                 
                   V 
                   2 
                 
                 
                   ρ 
                   ⁢ 
                   
                     L 
                     2 
                     2 
                   
                 
               
               ⁢ 
               
                 ( 
                 
                   W 
                   
                     W 
                     + 
                     M 
                   
                 
                 ) 
               
             
             = 
             P 
           
         
       
     
     where “V” is the applied voltage, “L” distance between busbars and ρ is the sheet resistivity, typically 30-45 Ohms/□. It has been found even using the concepts disclosed herein using intermittent dielectric insulation that sufficient current will flow to still cause heating in the L 1  or nose area of the goggles. The equations developed assume little or no electrical flow from adjoining conductive areas. However, this is not always the case. To prevent side current flow, a method was devised to prevent current flow from adjoining heated areas. The ITO coating is a transparent brittle ceramic that is an extremely fragile material. By making almost invisible scratches or by using a sharp knife die, the ceramic conductor will be scored and will not have electrical continuity across the scored line. This leaves little or no visible optical change in the lens, and the lens look visibly transparent. 
       FIG.  11    shows a schematic view of an ITO lens with a scored electrically discontinuous portion of the ITO coating  102  using the present teachings. In  FIG.  11   , the lens has a scored electrically discontinuous ITO coating  102  has scored boundaries created by scored lines  105  in ITO coating  102  creating a cold zone  104 . The remainder of the lens comprises a printed ITO lens area  106  and the printed silver busbars  103 . A power source  107  provides electrical power to the system. 
       FIG.  12    shows a schematic view of an exemplary ITO lens also with a scored electrically discontinuous portion of the ITO coating  102  in combination with printed clear dielectric  108  to provide an electrically isolated cold zone  109  using the present teachings. In  FIG.  12   , the lens has a scored electrically discontinuous ITO coating  102  in combination with printed clear dielectric  108  to provide an electrically isolated cold zone  109 , with the printed clear dielectric  108  preventing electrical contact between the ITO coating  102  and the busbars  103 . In this embodiment, the cold electrical isolated zone  109 , which is on the otherwise heated ITO coating  102 / 110 , is created between the printed silver busbars  103  by way of score lines  127 , which create an electrical discontinuity. A power source  107  provides electrical power to the system. 
     The knife or die or scored lines  105  are shown in  FIG.  11   . The cool zone  104  created by the scored lines  105  is electrically isolated from the busbars  103  and is cold. A series of these cool zones  104  may be used to provide intermittent cold areas. By using the equations developed above, relatively even or uniform heating will occur. While a sharp knife edge can be used to score the ITO, a discontinuous or serrated edge also can be used to allow some current flow from “L”. As shown in  FIG.  12   , it also is possible to print a transparent dielectric  108  insulator between the top and bottom busbars  103  and then score or use a knife die to provide interrupted electrical path from the sides as shown by the score lines  127  in  FIG.  12   . 
     While the electric isolation may be accomplished by die cutting a section out of the ITO coating  102 , this is not a practical solution as the lens is mechanically weak and would provide visual discontinuity. By reducing or eliminating the heating in the nose area, as illustrated by the cold electrical isolated zone  109  in  FIG.  12   , as much as 40% of the energy can be applied to the large viewing area. This will reduce the size and cost of a battery supply, such as power source  107 . It also reduces energy loss due to heating the busbars  103  as the resistance is higher and less current is required. Also, for very cold (−° C.) ambient, more voltage and current is required, which would cause extreme heating in the nose area with ΔT temperature rise exceeding 100° C., which at room temperature could damage the lens. Thus, it is preferable to prevent heating in the nose area. Fortunately, the nose area is typically out of the visual area from the eyes. 
       FIG.  13    shows a schematic view of an ITO lens using laser cut or die cut holes  113  in the ITO coating  102  in combination with printed clear dielectric to provide an electrically isolated cold zone using the present teachings. In  FIG.  13   , the lens has an electrically discontinuous ITO coating  102  between the printed silver busbars  103  in the form of the laser cut or die cut holes  113 . A power source  107  provides electrical power to the system. As shown in  FIG.  13   , another method of obtaining relatively uniform heating is to provide such small laser cut or die cut holes  113  in the ITO coating  102  using the equation where the sheet resistivity is changed according to 
     
       
         
           
             ρ 
             = 
             
               
                 
                   ( 
                   
                     
                       L 
                       1 
                     
                     
                       L 
                       2 
                     
                   
                   ) 
                 
                 2 
               
               ⁢ 
               
                 
                   ρ 
                   1 
                 
                 . 
               
             
           
         
       
     
     This can be accomplished by using a laser or knife die to punch the small laser cut or die cut holes  113  in the polyester (or other substrate material) film  126 , and then sputtering on a vapor conductive layer such as ITO or other material as shown in  FIG.  13    after laminating the film to a polycarbonate substrate. This will create the laser cut or die cut holes  113  in the is ITO coating  102 . 
     A major concern is the use of these printed silver busbars. The sheet resistivity of printed silver varies between 0.04 f/o and 0.13 Ohm per square. So, the resistance of a silver trace 10″ long and 0.250″ wide would be 
     
       
         
           
             R 
             = 
             
               
                 ρ 
                 ⁢ 
                 
                   L 
                   W 
                 
               
               = 
               
                 
                   .1 
                   
                     
                       1 
                       ⁢ 
                       0 
                     
                     
                       2 
                       ⁢ 
                       5 
                     
                   
                 
                 = 
                 
                   4 
                   ⁢ 
                       
                   
                     Ohms 
                     . 
                   
                 
               
             
           
         
       
     
     A silver wire or copper wire 0.030″ in diameter was measured to be 0.4 Ohms or at least an or of magnitude less. In designs of transparent goggles or visors that are heated electrically, the printed silver traces will take up the visual space and electrical heating loss that would mean less heating and more required energy for battery heated goggles and visors. 
       FIG.  14    shows a perspective schematic view of an ITO/polycarbonate sandwich using the present teachings, which will help alleviate the concerns regarding the use of printed silver busbars mentioned above. In  FIG.  14   , silver or copper wire  115  is placed between a polycarbonate film  118  and the ITO coating  119 , so as to form a sandwich. Bakelite® or another equivalent material, blocks are placed on either side of the sandwich and force  116  is applied, thus melting the silver or copper wire conductor into the ITO coating  119 /polycarbonate film  118  sandwich. A power source  107  provides electrical power to the system. The wire  115 , preferably 0.030″ silver or copper wire, is sandwiched between two rigid thermal insulated plates  117  and in contact with the ITO coating  119 /polyester film  118  sandwich. A pressure force  116  is applied on the sandwich. This results in embedding the wire  115  in the polycarbonate film  118 . The polycarbonate film  118  will melt into the sandwich when 4 amps of current heats the wire  115  as shown in  FIG.  14   . 
       FIG.  15    shows a perspective schematic view of an ITO/polycarbonate lens showing a silver or copper wire  122  and silver connecting trace  123  using the present teachings. In  FIG.  15   , a melted wire busbar is used with a thin (0.040″) printed contacting ITO trace, where a transparent polymer substrate  120 , an ITO coating  121  on the polymer substrate  120 , the silver or copper wire  122 , and a printed (0.040″) silver connecting trace  123  is used. The wire  122  protrudes above the surface of the ITO coating  121 /polymer substrate  120 , which can result in the ITO becoming damaged so it will not conduct electricity. It was found that printing a silver trace  123  1 mm wide≈0.040″ over the wire  122  results in the wire  122  being in electrical contact with the ITO coating  121 . This concept of embedded wire busbars provides that the metal (silver or copper) wire  122  is encased and rigidity held by the polymer substrate  120 . The coefficient of expansion with temperature of the polymer substrate  120  is three times greater or more than the metal wire  122 , but thermal cycling from −5° C. to 70° C. showed the wire  122  was firmly in place. The advantages of using a wire busbar with a slight silver trace  123  are many, including:
         1) the wire can be easily connected or soldered to power supply wires without rivets or clamps when using printed silver busbars which often introduce hot spots at the connection further wasting energy;   2) less expensive silver is used;   3) less visual area is obscured;   4) less energy loss in the more conductive wire busbar; and   5) longer lengths can be used.       

       FIG.  16    shows a sectional side schematic of an ITO/polycarbonate lens showing embedded silver/copper wire busbars  124  and a coating of transparent PEDOT conductive polymer  125  on a transparent polycarbonate substrate  126  using the present teachings. While the method of heating the wire  124  electrically and melting it into the substrate  126  works well, other means such as using hot rollers and pressure or hot platens also may be used. The heated platens or rollers may cause distortion in the plastic substrate  126 . While a round wire  124  is shown, rectangular extruded wires with more conductive cross sections may also be used. In the embodiment shown in  FIG.  16   , experiments were performed using a coating  125  of Oracon® 1CP 1050 across two embedded wires  124  in the polycarbonate substrate  126 . The Oracon® 1CP 1050 is a conductive transparent polymer  125  Ohms/□/Mill or PEDOT from AGFA Corp. The material, when dried is conductive with a slight blue tint and allows 90% or more light transmittance. The material is in order of magnitude less costly when compared with ITO. When current or voltage is applied between the wires  124 , heating occurred. The ΔT versus light transmission and coating thickness can be optimized. 
       FIGS.  17 - 18    are thermographs of lenses illustrating the teachings of the present disclosure. Standard (unscored) lenses (prior art) are shown in the thermograph of  FIG.  17    and scored lenses are shown in the thermograph of  FIG.  18   . The thermographs were taken on lenses tested at both 10-volt input at an ambient temperature of 22° C. The dielectric coating, in this case ITO, was tested unscored, discontinuously scored, and continuously scored to show the impact of scoring on temperature distribution across the lenses. 
       FIG.  17    is a thermograph of a standard printed lens such shown in  FIG.  10    illustrating an electrically isolated cold zone created using a 10-volt input at an ambient temperature of 22° C. As can be seen, at a central nose portion of the lens, the temperature of the lens is 80.0° C. 
       FIG.  18    is a thermograph of a continuously scored lens such shown in  FIG.  12    illustrating an electrically isolated cold zone created using a 10-volt input at an ambient temperature of 22° C. As can be seen, at a central nose portion of the lens, the temperature of the lens is 53.4° C. 
     The testing of the unscored, discontinuously scored, and continuously scored lenses shows that at a 10-volt input, discontinuous scoring of the dielectric coating creates a drop in the temperature of the lens relative to the unscored lens, creating a cold zone, while continuous scoring of the dielectric coating maintains this drop in the temperature of the lens relative to the unscored lens, maintaining but not affecting to any great degree the temperature of the cold zone relative to the discontinuously scored lens. This leads one to understand that with a 10-volt input, either discontinuous scoring or continuous scoring of the dielectric coating would be necessary to create the cold zone proximal to the goggle-wearer&#39;s nose for better comfort. 
     The discontinuity or discontinuities formed in the dielectric coating also can be formed by laser ablation. The concept of laser ablation is to use a high-power laser such as a CO 2  laser or a pulse laser to heat the surface of the dielectric coating on the polyester substrate so that the polyester substrate surface will be very hot and cause ablation or a hot vapor that will cause an electrical disconnect or discontinuity in the dielectric coating. A photoetch thin 0.001″-0.002″ reflective copper mask can be fabricated with 0.001″, or 0.002″ wide traces in contact with the lens that will allow the laser energy to impinge on the dielectric coating/polyester substrate surface in the etched area causing sublimation or ablation. The thin lines can be etched on the reflective foil in a pattern that would electrically isolate selective zones (around the nose, for example) so no electrical heating will occur when a voltage is applied to the busbars. An advantage of the laser ablation concept is that very thin lines of material can be ablated leaving very little optical change. While a mask is suggested, a programmed laser beam 0.001″ wide may be programmed to impinge on the surface to form a continuous area of electrical discontinuity that will not be heated. A high-power water jet also may be used to score the dielectric coating. 
     In some examples, the conductive coating can be added only to portions of the busbar where heating is required. For instance, the conducting coating can be added to the portions of the busbars that are located on the portions of the lens vis-A-vis the eyes (and not the nose). 
     In some examples, when the lens has a non-uniform width (width defined as the distance from the top of the lens to the bottom of the lens, such as L2 or L1), the busbars may follow the shape of the lens (follow the curvature of the lens). 
     The lens can be used as a shield (such as a windshield) for certain vehicles as snowmobiles, all-terrain vehicles such as gators and side-by-side vehicles, four-by-fours, caterpillars, snowcats, motorcycles, scooters, etc. The lens may also be used for goggles, helmets (as the vizor), etc. 
     Heated Shield Using Embedded Heater Wires: 
     In some embodiments, as shown in  FIG.  19   , a shield  200 , such as a windshield found on a side-by-side vehicles), may include embedded heater wires  215  (e.g. copper or silver) positioned at given intervals through the shield  200  for, e.g., defogging and/or de-icing. The wire heaters  215  are connected to busbars  210  positioned at opposite ends of the lens (e.g. soldered thereto through the use of tin or led), the busbars  210  connected to a power source  220 . The busbars  210  are normal to the embedded wire heaters. The wire heaters  215  may be curved if the shield  200  is curved (i.e. an uneven width). 
     In these embodiments, as the heating is achieved through the heater wires  215 , the substrate layer (e.g. polycarbonate layer)  212  does not require a conductive layer (e.g. ITO layer). 
     In some examples, when adding the wire heaters  215  to the substrate layer  212  of the shield  200 , the wire heaters  215  may be embedded simultaneously in the substrate layer  212 , e.g., by passing a current through the wire heaters  215 , causing the wire heaters to heat up and melt the substrate layer  212 , resulting in the embedding. In some embodiments, the wire heaters  215  may be imbedded in the substrate layer  212  through injection-molding. 
     In some examples, when the shield  200  has a non-uniform width (width defined as the distance from the top of the lens to the bottom of the lens, such as L2 or L1), the wire heaters  215  may follow the shape of the shield (follow the curvature of the shield). 
     The wire heaters  215  are positioned at spaced intervals across the shield and can be positioned lengthwise. 
     However, if closer spacing is required, the diameter of the wire heaters may be smaller as explained herein. It is of note that simply bonding the wires to the substrate using a transparent adhesive film may result in air gaps or air bubbles that may interfere with transparency and optical clarity, and reduce bonding between busbar and the substrate. 
     In some embodiments, to facilitate the soldering of the busbars and to improve visibility due to the colour of tin, the copper wire may be tinned or coated with silver. 
     The shield can be used as a windshield for certain vehicles as snowmobiles, all-terrain vehicles such as gators and side-by-side vehicles, four-by-fours, motorcycles, caterpillars, snowcats, boats, aircrafts, etc. 
     The present disclosure provides a simple way to design and construct complex shaped heaters for any shape. Many existing heaters use complex long lines of continuous conductive material which results in bends in the shape. Each shape requires a new design and current path. These twists and turns result in nonuniform heating and hot spots. Obviously, this concept greatly improves the design and uniformity. 
     As one of ordinary skill in the art would understand, it can be said that as the Watt density is constant, the area of the heater can be multiplied by the Watt density to get the total wattage and hence the current so the power supply can be determined. 
     The various embodiments are provided by way of example and are not intended to limit the scope of the disclosure. The described embodiments comprise different features, not all of which are required in all embodiments of the disclosure. Some embodiments of the present disclosure utilize only some of the features or possible combinations of the features. 
     Variations of embodiments of the present disclosure that are described, and embodiments of the present disclosure comprising different combinations of features as noted in the described embodiments, will occur to persons with ordinary skill in the art. It will be appreciated by persons with ordinary skill in the art that the present disclosure is not limited by what has been particularly shown and described herein above. Rather the scope of the invention is defined by the appended claims. 
     In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, it is the express intention of the applicant not to invoke 35 USC § 112(f) for any limitations of any of the claims herein, except for those in which the claim expressly uses the words “means for” together with an associated function. 
     Therefore, although selected aspects have been illustrated and described in detail, it will be understood that various substitutions and alterations may be made therein without departing from the spirit and scope of the present invention, as defined by the following claims. 
     LIST OF REFERENCE NUMBERS 
     
         
           1  Electrical connection 
           2  Electrical connection 
           3  Electrical connection 
           4  Busbar 
           5  Coating 
           6  Power supply 
           7  Power supply 
           8  Busbar 
           9  Busbar 
           10  Uniform conductive material 
           11  Uniform conductive material 
           12  Polymer film 
           13  Dielectric material 
           14  Busbar segment 
           21  Power supply 
           23  Uniform conductive material 
           24  Dielectric material 
           25  Busbar 
           26  Dielectric space 
           27  Polymer film 
           28  Dielectric space 
           29  Dielectric space 
           30  Dielectric space 
           31  Dielectric space 
           32  Dielectric space 
           33  Dielectric space 
           34  Dielectric space 
           35  Dielectric space 
           39  Power supply 
           40  Connection Point 
           41  Connection Point 
           42  Connection Point 
           43  Connection Point 
           44  Connection Point 
           45  Connection Point 
           48  Heating elements 
           49  Busbar 
           50  Metal strip 
           51  Polyester film 
           52  Busbar 
           53  Surface/shape 
           54  Fixture 
           55  Viewer 
           56  Uniform conductive material 
           57  Space 
           58  Space 
           59  Dielectric coating 
           60  Busbar 
           61  Uniform conductive material 
           62  Uniform conductive material 
           63  Voids 
         Lx Length between busbars 
         M Unheated or non-contact zone 
         V Power supply 
         W Heated or contact zone 
           102  Coating 
           103  Busbar 
           104  Cold zone 
           105  Scored lines 
           106  Lens area 
           107  Power source 
           108  Dielectric 
           109  Cold zone 
           110  Coating 
           113  Holes 
           115  Wire 
           116  Force 
           117  Insulated plate 
           118  Film 
           119  Coating 
           120  Substrate 
           121  Coating 
           122  Wire 
           123  Trace 
           124  Wire 
           125  Polymer 
           126  Substrate 
           127  Scored lines