Patent Publication Number: US-2023152609-A1

Title: Thermal activated switching polarizer

Description:
TECHNICAL FIELD 
     This disclosure relates generally to optics, and in particular to dimming and polarization. 
     BACKGROUND INFORMATION 
     A smart device is an electronic device that typically communicates with other devices or networks. In some situations the smart device may be configured to operate interactively with a user. A smart device may be designed to support a variety of form factors, such as a head mounted device, a head mounted display (HMD), or a smart display, just to name a few. 
     Smart devices may include one or more components for use in a variety of applications, such as gaming, aviation, engineering, medicine, entertainment, video/audio chat, activity tracking, and so on. In some examples, a smart device may include one or more optical elements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Non-limiting and non-exhaustive embodiments of the invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. 
         FIG.  1    illustrates an example head mounted device that includes thermally activated switchable polarizer optical elements, in accordance with aspects of the disclosure. 
         FIG.  2    illustrates an example optical element and an exploded view of a portion of the optical element that includes horizontal strips of a switching material, in accordance with aspects of the disclosure. 
         FIG.  3 A  illustrates a system including a heating module and a side view of a switchable polarizer optical element, in accordance with aspects of the disclosure. 
         FIG.  3 B  illustrates a system including a heating module and a side view of a switchable polarizer optical element including a transparent conductor, in accordance with aspects of the disclosure. 
         FIG.  3 C  illustrates a system including a dual-orientation switchable polarization optical element, in accordance with aspects of the disclosure. 
         FIGS.  4 A- 4 B  illustrates an example head mounted device that includes an illumination module for selectively heating strips included in a switchable polarizer optical element to selectively polarize incident light, in accordance with aspects of the disclosure. 
         FIG.  5    illustrates a flow chart illustrating an example process of operating a switchable polarizer, in accordance with aspects of the disclosure. 
         FIG.  6    illustrates an optical system having a switchable polarizer layer and a second polarizer layer, in accordance with aspects of the disclosure. 
         FIG.  7    illustrates an optical system that includes switchable polarizers, in accordance with aspects of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of a thermal activated switchable polarizer are described herein. In the following description, numerous specific details are set forth to provide a thorough understanding of the embodiments. One skilled in the relevant art will recognize, however, that the techniques described herein can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring certain aspects. 
     Reference throughout this specification to “one implementation” or “an implementation” means that a particular feature, structure, or characteristic described in connection with the implementation is included in at least one implementation of the present invention. Thus, the appearances of the phrases “in one implementation” or “in an implementation” in various places throughout this specification are not necessarily all referring to the same implementation. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more implementations. 
     In some implementations of the disclosure, the term “near-eye” may be defined as including an element that is configured to be placed within 50 mm of an eye of a user while a near-eye device is being utilized. Therefore, a “near-eye optical element” or a “near-eye system” would include one or more elements configured to be placed within 50 mm of the eye of the user. 
     In aspects of this disclosure, visible light may be defined as having a wavelength range of approximately 380 nm - 700 nm. Non-visible light may be defined as light having wavelengths that are outside the visible light range, such as ultraviolet light and infrared light. Infrared light having a wavelength range of approximately 700 nm - 1 mm includes near-infrared light. In aspects of this disclosure, near-infrared light may be defined as having a wavelength range of approximately 700 nm - 1.6 µm. 
     The optical elements, systems, devices, and techniques described in this disclosure may be used in prescription glasses, non-prescription sunglasses, head mounted devices, and/or other optical systems, for example. Implementations of this disclosure include a thermally activated switchable polarizer. 
     In an example implementation, the switchable polarizer is driven between a polarizing state and a transparent state by selectively heating strips of switchable material that are arranged similarly to a wire-grid polarizer. When the strips of the switchable material are below a threshold switching temperature (e.g. approximately 60 degree C) the switching material (e.g. vanadium dioxide) is substantially transparent to visible light and incident light retains its polarization orientation as it propagates through the strips of the switching material. And when the strips of the switchable material are heated to a threshold switching temperature (e.g. approximately 60 degree C) the switching material (e.g. vanadium dioxide) becomes opaque and an electrical conductor so that the strips function as polarizers that polarize incident light. 
     The strips of the switchable material may be thermally regulated by a thermal module to facilitate switching the switchable polarizer between a polarizing state and a transparent state. In an implementation, an electrical current is driven through the strips of the switchable material to control the temperature of the strips. The switchable material may be electrically resistive (or have semiconductor properties) and therefore driving current through the strips of the switchable material heats the strips to the threshold switching temperature. At or above the threshold switching temperature, the switching material may be a metal and therefore electrically conductive and facilitate polarizing incident light. In another implementation, a transparent conductor layer (e.g. indium tin oxide) is disposed to impart heat to the strips of the switchable material. In another implementation, an illumination module is configured to selectively illuminate the strips of the switching material with infrared light to heat the strips. These and other implementations are described in more detail in connection with  FIGS.  1 - 7   . 
       FIG.  1    illustrates an example head mounted device  100  that includes thermally activated switchable polarizer optical elements  172 A and  172 B, in accordance with aspects of the disclosure. Head mounted device  100  include arms  161 A and  161 B coupled to a frame  164 . Switchable polarizer optical elements  172 A and  172 B (collectively referred to as optical elements  172 ) are included in frame  164 . When a switchable polarizer optical element  172  is driven to a transparent state, incident light  199  propagates through the optical element  172  and retains its polarization orientation as transmitted light  198 . However, when switchable polarizer optical element  172  is driven to a polarizing state, incident light  199  propagating through the optical element  172  will become polarized transmitted light  198  since the strips of the switchable material will polarize incident light  199  (by absorbing and/or reflecting a particular polarization orientation of incident light  199 ) when the strips are heated to the threshold switching temperature. For example, a horizontal polarization orientation of incident light  199  may propagate through optical element  172  while the vertical polarization orientation of incident light  199  may be absorbed/reflected by the strips of the switching material when optical element  172  is driven to the polarizing state. 
       FIG.  2    illustrates an example optical element  272  and an exploded view of a portion of optical element  272  that includes horizontal strips  233  of a switching material, in accordance with aspects of the disclosure. Optical element  272  is shaped as a lens that may be included in head mounted device, such as head mounted device  100 . However, the optical element  272  may be shaped and sized to whatever optical system or device it will be included in. 
     The exploded portion of  FIG.  2    illustrates two horizontal strips  233 A and  233 B of a switching material that is disposed over a transparent layer  210 . Transparent layer  210  may be glass or plastic, for example.  FIG.  2    illustrates that strips  233 A and  233 B (collectively referred to as strips  233 ) may be arranged periodically to facilitate polarizing light when the strips are heated to the threshold switching temperature. The width of the strips  233  is dimension  291  and the period of the strips is dimension  292 . The period includes the width of a strip  233  and the spacing between the strips. In implementations of the disclosure, the period  292  of the strips  233  may be less than 450 nm to avoid diffraction of visible light wavelengths. A width  291  of the strips of the switchable material may be less than or equal to half of the period  292 . The threshold switching temperature may be between 50 and 70° C., in some implementations. In some implementations of the disclosure, a switching material may be defined by any material that can switch between a metal and non-metal in response to heat. In some implementations of the disclosure, the switching material is an electrochromic material. 
     While the strips  233  in optical element  272  are oriented horizontally, the strips may be arranged vertically, or at other angles, depending on the context. Arranging the strips with the horizontal orientation may block sunlight glare, for example. In another context, the strips may be aligned vertically to block polarized light emitted by a polarized display for example. 
       FIG.  3 A  illustrates a system  300  including a heating module  370  and a side view of a switchable polarizer optical element  301 , in accordance with aspects of the disclosure. Heating module  370  is configured to drive an electrical current signal  373  in response to an input signal  371 . Input signal  371  may control whether switchable polarizer optical element  301  is driven to a polarizing state or a transparent state. 
     In  FIG.  3 A , the electrical current signal  373  is driven onto strips  333 A,  333 B,  333 C,  333 D,  333 E,  333 F, and  333 G (collectively referred to as strips  333 ) when input signal  371  indicates a polarizing state for switchable polarizer optical element  301 . A first end of the strips  333  may have a different voltage potential than a second (opposite) end of the strips  333  when the current is driven onto the strips. The switchable material may be a resistive electrical element or a semiconductor when the switchable material is below the threshold switching temperature. Therefore, driving a current through the switchable material of the strips  333  can heat the strips. When the strips  333  reach a threshold switching material (e.g. 60° C.), the strips  333  change to a conductive state (rather than being a resistor or semiconductor state) and also function as a polarizing grid because of the conductive state. When the switching material is in a resistive state or semiconductor state, the strips of the switching material do not function as a polarizing grid. 
     In an implementation, the switchable material is substantially transparent when the switchable material is below the threshold switching temperature and the switchable material is substantially opaque when the switchable material is at or above the threshold switching temperature. When vanadium dioxide is used as the switching material, the strips may have a slightly yellow tint (substantially transparent) in the transparent state of optical element  301  and turn to dark blue (substantially opaque) in the polarizing state. 
     In aspects of this disclosure, the term “transparent” may be defined as having greater than 90% transmission of light. In some aspects, the term “transparent” may be defined as a material having greater than 90% transmission of visible light. The term “substantially transparent” may be defined as greater than 75% transmission of visible light and the term “substantially opaque” may be defined as less than 25% of visible light. 
       FIG.  3 A  illustrates that a height  293  of strips  333  of the switchable material may be approximately the same as a width  291  of the strips  233 , in some implementations. The strips  333  are disposed on a transparent substrate  310 . Strips  333  may directly contact substrate  310  or be bonded to substrate  310  with an adhesive. Incident light  399  encounters substrate  310  normal to a plane of substrate  310 , in  FIG.  3 A . Strips  333  of the switchable material are arranged to polarize incident light  399  propagating through the transparent substrate layer  310  when the switchable material is heated to a threshold switching temperature. Hence, transmitted light  398  is polarized when the strips  333  are heated to the threshold switching temperature. Incident light  399  propagating through transparent substrate layer  310  is unpolarized by the strips  333  of the switchable material when the switchable material is below the threshold switching temperature. Hence, transmitted light  398  is unpolarized when the strips  333  are below the threshold switching temperature. 
       FIG.  3 B  illustrates a system  302  including a heating module  374  and a side view of an example switchable polarizer optical element  303 , in accordance with aspects of the disclosure. Heating module  374  is configured to drive an electrical current signal  376  in response to an input signal  375 . Input signal  375  may control whether switchable polarizer optical element  303  is driven to a polarizing state or a transparent state. 
     Instead of driving current onto strips  333  to heat strips  333  as in system  300  of  FIG.  3 A , system  302  includes a transparent conductor layer  320  that is heated by an electrical current to impart heat to strips  333 . Transparent conductor layer  320  is disposed between substrate  310  and strips  333 . Transparent conductor layer  320  may be indium tin oxide (ITO), in some implementations. Heating module  374  selectively drives electrical current signal  376  onto the transparent conductor layer  320  to change the strips  333  between the transparent state and the polarizing state. In some implementations, transparent conductor layer  320  is patterned to be selectively heated to facilitate pixelated switchable polarization of incident light  399 . In other words, optical element  303  may have zones that are thermally controlled to above or below the threshold switching temperature so that some or a portion of the zones polarize incident light  399  and some zones do not polarize incident light  399 . 
       FIG.  3 C  illustrates a system  304  including a dual-orientation switchable polarization optical element  305 , in accordance with implementations of the disclosure. In addition to the optical element  303  of  FIG.  3 B , dual-orientation switchable polarization optical element  305  includes a second transparent conductor layer  321  and second strips  335  in a second switchable material layer. In  FIG.  3 C , the second strips  335  of the switchable material are disposed orthogonal to strips  333  so only the first strip  335 A is visible in the side view of  FIG.  3 C . The remaining strips  335  are periodically arranged behind strip  335 A and are thus not visible in  FIG.  3 C . First strips  333  are configured to polarize incident light  399  to a first polarization orientation and second strips  335  are configured to polarize incident light  399  to a second polarization orientation that is orthogonal to the first polarization. Therefore, second strips  335  of the switchable material are arranged to polarize the incident light  399  propagating through the transparent layer  310  to the second polarization orientation when the second strips  335  are heated to the threshold switching temperature. Second strips  335  may have a height  393  that is similar to, or different from, the height  293  of strips  333 . The width and period of the second strips may be the same or different than the width  291  and period  292  of strips  333 . 
     In  FIG.  3 C , transparent substrate layer  310  may be sized to have a thickness to allow layer  310  to serve as a thermal insulator between transparent conductor layer  320  and transparent conductor layer  321 . Transparent conductor layer  321  may be patterned to facilitate pixelated switchable polarization of transparent conductor layer  321 . Transparent conductor layer  321  may also include the additional features described with respect to transparent conductor layer  320 . 
     Heating module  383  is configured to drive an electrical current signal  385  in response to an input signal  384 . Input signal  384  may control whether second strips  335  are heating to the threshold switching temperature that causes second strips  335  to polarize incident light  399  to the second polarization orientation. The polarization orientation of transmitted light  398  may be selected to be a first polarization orientation (by heating strips  333  to the threshold switching temperature with heating module  374 ) or to be selected to be the second polarization orientation (by heating strips  335  to the threshold switching temperature with heating module  383 ). The first polarization orientation may be a linear horizontal polarization and the second polarization orientation may be a linear vertical polarization that is orthogonal to the first polarization orientation. In some implementations, the first polarization orientation is different from the second polarization orientation, but the first polarization orientation is not necessarily orthogonal to the second polarization orientation. 
     Dual-orientation switchable polarization optical element  305  can be selectively driven to polarize light  399  into a first polarization orientation of transmitted light  398  by selectively heating strips  333  or dual-orientation switchable polarization optical element  305  can be selectively driven to polarize light  399  into a second polarization orientation of transmitted light  398  by selectively heating strips  335 . In some implementations, strips  333  and  335  are heated to the threshold switching temperature simultaneously. When strips  333  and  335  are arranged orthogonal to each other, the intensity of transmitted light  398  may approach zero as both polarization orientations (e.g. vertical polarized light and horizontal polarized light) are not transmitted when both strips  333  and  335  are heated above the threshold switching temperature. Thus, dual-orientation switchable polarization optical element  305  may be used as a global dimmer and/or a zoned dimmer when the transparent conductor layers  320  and  321  are patterned to include zones that can be selectively heated. 
     In some implementations of the disclosure, strips  333  and/or  335  are configured to block a wavelength band of visible light within incident light  399  when the strips are heated to the threshold switching temperature. To block a particular wavelength band of visible light, the strip dimensions (e.g. height  293  and width  291 ) and/or the period (e.g.  292 ) of the strips are tuned to block the particular wavelength. In an example implementation, the strips may be configured to block green visible light. Since human eyes are particularly sensitive to green light, this may be advantageous in the context of near-eye optical elements. In another example implementation, the strips are configured to block a set of wavelengths to give the optical element a particular vanity tint when the optical elements are used in glasses. 
     In an implementation, the period of the strips  333  and/or  335  are configured to reflect a plurality of wavelength bands of visible light when the switchable material is heated to the threshold switching temperature. 
       FIG.  4 A  illustrates an example head mounted device  400  that includes an illumination module  440  for selectively heating strips  433  included in a switchable polarizer optical element  472 B to selectively polarize incident light  499 , in accordance with aspects of the disclosure. Strips  433  in  FIG.  4 A  may have the same characteristics as described with respect to strips  333 . 
     Head mounted device  400  include arms  461 A and  461 B coupled to a frame  464 . Optical elements  472 A and  472 B (collectively referred to as optical elements  472 ) are included in frame  464 . When a switchable polarizer optical element  472  is driven to a transparent state, incident light  499  propagates through the optical element  472  and retains its polarization orientation as transmitted light  498 . However, when switchable polarizer optical element  472  is driven to a polarizing state, incident light  499  propagating through the optical element  472  will become polarized transmitted light  498  since the strips  433  of the switchable material will polarize incident light  499  (by absorbing and/or reflecting a particular polarization orientation of incident light  499 ) when the strips are heated to the threshold switching temperature. For example, a horizontal polarization orientation of incident light  499  may propagate through optical element  472  while the vertical polarization orientation of incident light  499  may be absorbed/reflected by the strips of the switching material when optical element  472  is driven to the polarizing state. 
     In  FIG.  4 A , strips  433  of the switching material are selectively heated by illuminating the strips  433  with patterned infrared illumination light  441 . Processing logic  470  may drive illumination module  440  to selectively illuminate strips  433  with patterned infrared illumination light  441 . Illumination module  440  may include a projector that directs patterned infrared illumination light  441  to strips  433  to selectively modulate the temperature of the strips  433  to below or above the threshold switching temperature. Hence, illumination module  440  is the heating module for strips  433 , in  FIG.  4 A . A display may be included in illumination module  440  to dynamically direct the patterned infrared illumination light  441  to strips  433 . Illumination module  440  may include a two-dimensional mirrored scanner that scans infrared illumination light  441  to strips  433 . In some implementations, the infrared illumination light  441  is directed to zones of optical element  472 B so that portions of optical element  472 B are polarizing (since the infrared illumination light  441  raises the temperature above the threshold switching temperature of the strip or portion of the strip). While  FIG.  4 A  illustrates a single illumination module  440  for illuminating the strips  433  in optical element  472 B, of course a second illumination module may be included in head mounted device  400  to illuminate strips  433  of optical element  472 A with infrared illumination light. 
       FIG.  4 B  illustrates a top view of a portion of head mounted device  400 , in accordance with aspects of the disclosure.  FIG.  4 B  shows an example optical element  472 B includes transparent substrate  310  and strips  433 . Switchable polarizer optical element  472 B selectively polarizes incident light  499  propagating to an eye  403  of a user that occupies an eyebox region  401 . 
       FIG.  5    illustrates a flow chart illustrating an example process  500  of operating a switchable polarizer, in accordance with aspects of the disclosure. The order in which some or all of the process blocks appear in process  500  should not be deemed limiting. Rather, one of ordinary skill in the art having the benefit of the present disclosure will understand that some of the process blocks may be executed in a variety of orders not illustrated, or even in parallel. All or a portion of process  500  may be executed by processing logic included in a head mounted device. 
     In process block  505 , the switchable polarizer is driven to a polarizing state. Driving the switchable polarizer to the polarizing state includes imparting heat to strips of a switchable material that are arranged to polarize incident light when the switchable material is heated to a threshold switching temperature. 
     In process block  510 , the switchable polarizer is driven to a transparent state. Driving the switchable polarizer to the transparent state includes allowing the strips to cool below the threshold switching temperature. Process  500  may return to process block  505  subsequent to executing process block  510 . 
     In implementations of the disclosure, imparting the heat to the strips of the switchable material includes illuminating the strips of the switchable material with infrared light. In implementations of the disclosure, imparting the heat to the strips of the switchable material includes driving electrical current through a transparent substrate. 
       FIG.  6    illustrates an optical system  670  having a switchable polarizer layer  671  and a second polarizer layer  673 , in accordance with aspects of the disclosure. Switchable polarizer layer  671  may include the switchable polarizer optical elements  301  or  303  of  FIGS.  3 A and  3 B . Second polarizer layer  673  includes lines (e.g. wire-grid polarizing lines) that are disposed perpendicular (or nearly perpendicular) to the strips  333  of switchable polarizer layer  671 . Disposing the lines of second polarizer layer  673  perpendicular to strips  333  of switchable polarizer layer  671  may increase the percentage of incident light  699  that is blocked by optical system  670 . 
     Second polarizer layer  673  may be a switchable polarizer, in some implementations, and include the switchable polarizer optical elements  301  or  303  of  FIGS.  3 A and  3 B . When second polarizer layer  673  is a switchable polarizer, switchable polarizer layer  671  and second polarizer layer  673  may be both driven to a polarization state at a same time to increase the percentage of incident light  699  that is blocked by the orthogonal strips  333  included in layers  671  and  673 . In another context, switchable polarizer layer  671  and second polarizer layer  673  may be both driven to a transmissive state at a same time to increase the percentage of incident light  699  that propagates through optical system  670  to eye  602 . 
       FIG.  7    illustrates an optical system  770  that includes switchable polarizers, in accordance with implementations of the disclosure. Optical system  770  includes a first switchable polarizer  771 , a pixelated switchable polarization-rotating layer  772 , and a second switchable polarizer  773 . Switchable polarization-rotating layer  772  may be a switchable quarter-waveplate or a switchable half-waveplate, for example. Liquid crystal technology may be utilized in switchable polarization-rotating layer  772 . Switchable polarizer optical elements  301  or  303  of  FIGS.  3 A and  3 B  may function as first switchable polarizer  771  and/or second switchable polarizer  773 . Optical system  770  may be incorporated into a near-eye optical element (such as in near-eye optical element(s)  172 ) to modulate the polarization of incident scene light  799  that propagates to eye  702 . Using switchable polarizers instead of static polarizers increases the maximum transmission of scene light  799  to eye  702  as well as allowing optical system  770  to be selectively mostly transmissive (by way of selectively cooling the strips of switching material of switchable polarizers  771  and  773 ). Consequently, when system  770  is included in a near-eye optical element (e.g. optical element  172 ), the near-eye optical elements don’t necessarily appear dark in indoor environments where it would be desirable for the near-eye optical elements to appear in a transmissive (clear) state, for example. 
     In operation, the pixelated switchable polarization rotating layer  772  is driven to control the polarization state of the output light propagating towards switchable polarizer  773 . For the pixels that are to appear dark, the pixels in pixelated switchable polarization-rotating layer  772  are driven so that the polarization orientation of the output light for a particular pixel are absorbed by the switchable polarizer  773 . For the pixel that are to transmit the light, the pixels in pixelated switchable polarization-rotating layer  772  are driven so that the polarization orientation of the output light for a particular pixel propagates through the switchable polarizer  773 . 
     Embodiments of the invention may include or be implemented in conjunction with an artificial reality system. Artificial reality is a form of reality that has been adjusted in some manner before presentation to a user, which may include, e.g., a virtual reality (VR), an augmented reality (AR), a mixed reality (MR), a hybrid reality, or some combination and/or derivatives thereof. Artificial reality content may include completely generated content or generated content combined with captured (e.g., real-world) content. The artificial reality content may include video, audio, haptic feedback, or some combination thereof, and any of which may be presented in a single channel or in multiple channels (such as stereo video that produces a three-dimensional effect to the viewer). Additionally, in some embodiments, artificial reality may also be associated with applications, products, accessories, services, or some combination thereof, that are used to, e.g., create content in an artificial reality and/or are otherwise used in (e.g., perform activities in) an artificial reality. The artificial reality system that provides the artificial reality content may be implemented on various platforms, including a head-mounted display (HMD) connected to a host computer system, a standalone HMD, a mobile device or computing system, or any other hardware platform capable of providing artificial reality content to one or more viewers. 
     The term “processing logic” (e.g. processing logic  470 ) in this disclosure may include one or more processors, microprocessors, multi-core processors, Application-specific integrated circuits (ASIC), and/or Field Programmable Gate Arrays (FPGAs) to execute operations disclosed herein. In some embodiments, memories (not illustrated) are integrated into the processing logic to store instructions to execute operations and/or store data. Processing logic may also include analog or digital circuitry to perform the operations in accordance with embodiments of the disclosure. 
     A “memory” or “memories” described in this disclosure may include one or more volatile or non-volatile memory architectures. The “memory” or “memories” may be removable and non-removable media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules, or other data. Example memory technologies may include RAM, ROM, EEPROM, flash memory, CD-ROM, digital versatile disks (DVD), high-definition multimedia/data storage disks, or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information for access by a computing device. 
     Networks may include any network or network system such as, but not limited to, the following: a peer-to-peer network; a Local Area Network (LAN); a Wide Area Network (WAN); a public network, such as the Internet; a private network; a cellular network; a wireless network; a wired network; a wireless and wired combination network; and a satellite network. 
     Communication channels may include or be routed through one or more wired or wireless communication utilizing IEEE 802.11 protocols, BlueTooth, SPI (Serial Peripheral Interface), I 2 C (Inter-Integrated Circuit), USB (Universal Serial Port), CAN (Controller Area Network), cellular data protocols (e.g. 3G, 4G, LTE, 5G), optical communication networks, Internet Service Providers (ISPs), a peer-to-peer network, a Local Area Network (LAN), a Wide Area Network (WAN), a public network (e.g. “the Internet”), a private network, a satellite network, or otherwise. 
     A computing device may include a desktop computer, a laptop computer, a tablet, a phablet, a smartphone, a feature phone, a server computer, or otherwise. A server computer may be located remotely in a data center or be stored locally. 
     The processes explained above are described in terms of computer software and hardware. The techniques described may constitute machine-executable instructions embodied within a tangible or non-transitory machine (e.g., computer) readable storage medium, that when executed by a machine will cause the machine to perform the operations described. Additionally, the processes may be embodied within hardware, such as an application specific integrated circuit (“ASIC”) or otherwise. 
     A tangible non-transitory machine-readable storage medium includes any mechanism that provides (i.e., stores) information in a form accessible by a machine (e.g., a computer, network device, personal digital assistant, manufacturing tool, any device with a set of one or more processors, etc.). For example, a machine-readable storage medium includes recordable/non-recordable media (e.g., read only memory (ROM), random access memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, etc.). 
     The above description of illustrated embodiments of the invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. 
     These modifications can be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.