Abstract:
An electrically-adjustable light transmitter changes its light transmissivity responsive to an electric signal. By applying the electrically-adjustable light transmitter to a window and thereafter changing the electric signal to it, a window can be tinted and un-tinted. Jurisdictions that prohibit tinted vehicle windows are listed in a data base. A current location determined by a GPS is compared to data base entries. If the location is within an area where tinted windows are prohibited, a controller automatically un-tints the windows, or reduces the window tint to comply with applicable local laws.

Description:
BACKGROUND 
     Tinted vehicle windows are well known to reduce solar heating of a vehicle. Since they reduce the amount of ultraviolet and infrared that enters a vehicle&#39;s interior they also tend to protect the materials from which dashboards and interior surfaces are made. Unfortunately, window tinting can obscure or reduce a driver&#39;s ability to see and they are known by law enforcement to conceal the interior of a vehicle. Some states, counties, and municipalities prohibit tinted windows of any kind while other jurisdictions specify or define the maximum tinting or opacity that vehicle window glass can have. If a vehicle owner applies window tinting to a vehicle that is permitted by local ordinances but prohibited by the ordinances of surrounding jurisdictions, the vehicle owner risks being cited by law enforcement agencies in jurisdictions where vehicle window tinting is prohibited. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a motor vehicle with tinted windows leaving a jurisdiction where such windows are legal and entering a second jurisdiction where they are prohibited; 
         FIGS. 2A and 2B  depict an electrically-adjustable light transmitter, which can be applied to window glass; 
         FIG. 3  depicts a block diagram of a geographic location-responsive window tinting system; 
         FIG. 4  is a flowchart of a method of adjusting a window tint responsive to a geographic location; and 
         FIG. 5  depicts the use of an electrically-controllable window tinting mechanism in an all-electric vehicle. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a graphical depiction of a motor vehicle  100  having tinted windows  102  in a first jurisdiction  104 , and which is about to cross a boundary line  106  into a second jurisdiction  108 . Tinted windows are lawful in the first jurisdiction  104 ; they are prohibited in the second jurisdiction  108 . Prior art window tinting methods make it impractical or even impossible to tint and un-tint windows to provide the beneficial effects of tinted windows  102  where they are not prohibited yet avoid running afoul of state or local laws that prohibit them. 
       FIGS. 2A and 2B  are cross-sections of an electrically-adjustable light transmitter commonly known as an electrochromic device  200 . It is comprised of layers, which can be conformably attached to either side of a sheet of glass, or sandwiched between two layers as depicted in  FIGS. 2A and 2B . 
     The structure in  FIGS. 2A and 2B  is comprised of two glass panels. The layers sandwiched between them provide an electrically-adjustable transmissivity or “tint.” A control voltage applied to an elecrochromic layer determines the amount of light that can pass through it. 
     An outside glass panel  204  has first and second opposing surfaces  208  and  210 . An optically transparent conductor layer  206  is applied to the inside surface  208  of the outside panel  204 . 
     An electrochromic layer  212  is applied over the transparent conductor layer  206 . The electrochromic layer  212  is characterized by its ability to pass or block visible light responsive to the application or absence of a voltage. Stated another way, the electrochromic layer will block light when an electric potential is applied across the layer 
     An electrolyte/ionic conductor layer  214  is applied over the electrochromic layer  212 . An ion storage layer  216  is applied over the electrolyte/ionic conductor layer  214 . A second transparent conductor layer  218  is then applied over the ion storage layer  216 . The interior layers  206 - 218  are then sandwiched by a second glass panel  220  which faces the interior of the vehicle. It is important to note that the location of the electrochomic layer  212  relative to the electrolyte/ionic conductor layer  214  can be reversed and the device  200  kept operable. A depiction of such an alternate embodiment, i.e., wherein the location of layers  214  and  216  are interchanged with each other, is omitted for brevity. 
     An electric energy source  222  can be selectively applied to and removed from the two conductors  206  and  218  by a conventional switch mechanism  222 . In another embodiment, the strength of the field and/or the amount of current passing through the layer  212  can be controlled by a conventional voltage source or current source respectively. 
     In  FIG. 2A , the electrochromic device is not energized. Light rays  226  are thus free to pass through the electrochromic layer. 
       FIG. 2B  depicts the electrochromic device in an energized state. A voltage is applied to the electrochromic layer by the closure of a conventional switch  224 . While light  226  passes through the outside panel  204  and the first conductor layer  206 , light is blocked by the biased electrochromic layer  212 . The opacity and the tint of the device  200  can thus be electrically adjusted by an electric signal or voltage applied to the electrochromic layer. 
       FIG. 3  is a block diagram of a photo-electrochromic window tinter, also referred to herein as an electrically-operable window tinting system  300 . The system  300  is comprised of an electrochromic device  200 , such as the one depicted in  FIG. 2 . A stored program controller  302  provides a control voltage  304  to the electrochromic device  200  responsive to program instructions stored in an associated memory device  306  and various events and conditions detected by various sensors attached to the controller  302 . The controller  302  is coupled to the various sensors via a conventional input/output (I/O) bus  310 . The controller  302  and the memory device  306  are coupled to each other via a conventional memory bus. 
     The controller is depicted as being coupled to a separate memory device  314  that holds a window tinting rules database  314 . The database  314  is a list of geographic areas, each of which is defined by latitude and longitudinal coordinates, inside of which, there is at least one statute or law, rule, ordinance governing vehicle window tinting. 
     The controller is also coupled to an ambient light sensor  316 , an exterior ambient temperature sensor  318  and a vehicle interior temperature sensor  320 , which are useful in other applications of the photo-electrochromic window tinter. 
     In a first embodiment, of the photo-electrochromic window tinter  300 , the controller  302  queries the GPS receiver  312  for geographic coordinates, i.e., a location of where the vehicle is located. The location of the tinter or a vehicle it is attached to is provided to the controller in latitude and longitude coordinates. The controller  302  thereafter queries the window tinting rules database  314  to determine whether the current location of the vehicle is inside of a jurisdiction where tinted windows are prohibited, or if there is a tinted window opacity specification, i.e., a rule or law that dictates the darkness or degree to which a window tint passes light, which needs to be complied with. 
     In a second embodiment, which is useful for all vehicles but especially useful to electrically-powered vehicles, the controller  302  queries the ambient light sensor, ambient temperature sensor, and/or the interior temperature sensor  320  to adjust the tinting on the electrochromic device  200  to optimize interior temperatures responsive to interior and exterior conditions. 
       FIG. 4  depicts a method  400  of adjusting a window tint responsive to a geographic location. A method is performed by a controller or computer such as the controller  302  depicted in  FIG. 3  and described above. 
     At step  402 , the controller obtains its current location from a navigation system such as the GPS system  312  depicted in  FIG. 3 . Once the location is obtained from the GPS, a database is consulted at step  404  to determine or locate window tinting rules that apply to where the vehicle is located. As used herein, a window tinting rule is a statute or ordinance or other law or regulation that defines the tint that can be applied to a vehicle window including whether tinting is prohibited. 
     At step  406  the method first checks to determine whether a manual tinting input command has been received by the controller  302  from a manual user interface  303 . If a manual tinting adjustment command has been received, the method proceeds to step  410  where the window tint is manually adjusted by the controller providing an appropriate voltage to an electrically-adjustable light transmitting device, such as the electrochromic device depicted in  FIG. 2 . The method stays in a manual tinting mode at step  412  until the user inputs a command to the user interface to allow the system to resume an auto tint function whereupon the method returns to step  402 . 
     If no manual tinting adjustment command has been received at step  406 , the method proceeds to step  408  where the controller issues appropriate electrical signals to the electrically-adjustable light transmitter to comply with the tinting rule obtained from the database at step  408 . After the tinting is adjusted to conform to any applicable rule, the method returns to step  402 . The method  400  of adjusting window tint thus continuously checks where the vehicle is located and whether there are any applicable tinting rules and adjusts the window tint accordingly. The system  300  depicted in  FIG. 3  has sensors that can be monitored to determine how and when to adjust the opacity or transmissivity of a window responsive to other external events or conditions. The method depicted in  FIG. 4  can thus include a step of reading an ambient light sensor, an exterior ambient temperature sensor or an interior temperature sensor and adjusting the window tint electrically in order to provide a desired interior temperature, or to reduce heating and cooling load on an electric power source of an all-electric vehicle. 
       FIG. 5  is a block diagram of an electrically-powered vehicle  500 . The vehicle is considered to be “electrically-powered.” The vehicle  500  is comprised of an electric motor  502  powered by an inverter  504 . The inverter  504  provides power to the motor that it receives from a battery, fuel cell or other source of electric energy  506 . Motive power from the electric motor  504  is delivered through a drive shaft  508  to a differential  510 , front-located or rear-located, which is coupled to drive wheels  512 . 
     Since the vehicle  500  is all-electric, cabin environment conditions are also controlled using electric energy from the energy storage system  506 . Those of ordinary skill in the art will recognize that large amounts of energy are required to provide heat and to cool the interior of a vehicle. In an all-electric vehicle, reducing the power required to provide heat or to drive a refrigeration system is important. 
     In  FIG. 5 , a cabin environment controller  514  receives signals  516  from the inverter  504  and the energy storage system  506  in order to determine the energy capacity remaining in the energy storage system  506 . The cabin environment controller  514  is also coupled to an electrically-operated cabin air conditioner (A/C)  518  and to an electrically operated cabin heater  520  via a conventional control bus  522 . When the cabin interior temperature gets too high, the cabin environment controller  514  sends a signal to the electrically-driven air conditioner  518  to turn it on causing the A/C  518  to draw electric energy from the energy storage system  506  in the process. Conversely, when the cabin interior temperature is too low the environment controller  514  energizes electrically resistive heating elements in the cabin heater  520 , which also draws power from the energy storage system  506 . 
     An advantageous feature of the all-electric vehicle depicted in  FIG. 5  is the provision of the electrochromic window tinter  200  and the photo-electrochromic system  300  depicted in  FIG. 3 . When interior cabin temperatures require the air conditioning system  518  to be energized, the cabin environment controller  514  issues commands to either an electrochromic window tinter  200  itself, or to a separate photo-electrochromic system  300 , either of which maximizes the window tinting opacity in order to minimize the amount of infrared energy entering the vehicle from the Sun  112 . Similarly, when the cabin temperatures require heat to be added, i.e., cabin heating is required, the cabin environment controller  514  issues commands to either an electrochromic window tinter  200  itself, or to a separate photo-electrochromic system  300 , either of which minimizes the window tinting opacity in order to maximize the amount of infrared energy entering the vehicle from the Sun  112 . The electrochromic window tinter  200  can thus significantly reduce the energy required from a battery or other limited power source in an all electric vehicle. 
     In the embodiments described above the electrically-adjustable light transmitter is an electrochromic device as depicted in  FIG. 2 . Alternate embodiments can use other electrically-actuated light transmissive materials such as PLZT, which are able to turn opaque in less than  150  microseconds. Other technologies that can be used with the apparatus and method described above, and which are considered herein to be at least functionally equivalent to an electrochromic device, include suspended particle devices, liquid crystal, and reflective hydride devices. The term, “electrically-adjustable light transmitter” should therefore be construed to include an electrochromic device, suspended particle devices, liquid crystal devices, reflective hydride and PLZT. 
     The navigation system used in the preferred embodiment is a global positioning system or GPS. Alternate embodiments can use other navigation systems such as the GLONASS (Global Navigation Satellite System) system or by the triangulation of received radio frequency signals such as those broadcast from local cellular towers. 
     The foregoing description is for purposes of illustration only. The true scope of the invention is set forth in the appurtenant claims.