Patent Publication Number: US-2023162695-A1

Title: Global and local contrast control with brightness and shading adjustment of smart glass display

Description:
INTRODUCTION 
     The information provided in this section is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
     The present disclosure relates to display devices and more particularly to transparent display devices with automatic brightness and shading adjustment. 
     A display device may include a light emitting diode (LED) array that is arranged on a transparent layer such as glass. Transparent spaces are located between pixels of the LED array. As the spacing between the LEDs in the LED array increases, the level of transparency of the display device increases. Smaller scale display technologies such as micro LEDs can be used and provide an opportunity to make increasingly transparent display devices. 
     The display device may be used with variable levels of ambient light. For example, higher levels of ambient light on a front side or a back side of the display device tend to reduce the contrast of the display device. The lower contrast of the display device in these light conditions makes content such as images or graphics being displayed more difficult to see. 
     SUMMARY 
     A smart glass display is disclosed and includes a first glass layer, a second glass layer, a display layer, an auto-shading layer and a control module. The display layer is disposed between the first glass layer and the second glass layer and includes an array of light emitting diodes and at least one ambient light sensor. The at least one ambient light sensor is configured to detect a level of ambient light at the display layer. The auto-shading layer includes suspended particle devices each of which configured to selectively provide different levels of transparency. The control module is configured to, based on an output of the at least one ambient light sensor, adjust a transparency level of at least a portion of the auto-shading layer. 
     In other features, the at least one ambient light sensor includes ambient light sensors. 
     In other features, the at least one ambient light sensor is integrated in the display layer and is disposed within an outer periphery of the display layer. 
     In other features, the at least one ambient light sensor is disposed between light emitting diodes of the display layer. 
     In other features, the at least one ambient light sensor is in a same layer of the smart glass display as the display layer and is disposed outside of a periphery of the display layer. 
     In other features, the at least one ambient light sensor includes exterior ambient light sensors and one or more interior ambient light sensors. 
     In other features, the display layer is an outward facing display layer such that an image displayed on the display layer is visible on an exterior side of the smart glass display. 
     In other features, the display layer is an inward facing display layer such that an image displayed on the display layer is visible on an interior side of the smart glass display. 
     In other features, the control module includes: a comparator configured to obtain, based on the output of the at least one ambient light sensor, a brightness level; a vehicle message transceiver configured to obtain an image to display on the display layer; and an address driver configured to adjust brightness of at least a portion of the display layer based on the brightness level and drive the display layer to display the image. 
     In other features, the control module includes: a comparator configured to obtain a dimming level based on the output of the at least one ambient light sensor; a vehicle message transceiver configured to obtain an image to display on the display layer; an address driver configured to drive the display layer to display the image; and a shading driver configured to drive the auto-shading layer to adjust the transparency level of at least the portion of the auto-shading layer based on the dimming level. 
     In other features, the at least one ambient light sensor includes an interior ambient light sensor; and the control module is configured to adjust the dimming level based on an auto-shading level and an output of the interior ambient light sensor to compensate for an amount of auto-shading and determine an actual interior ambient light level. 
     In other features, a smart glass display is provided and includes: a first glass layer, a second glass layer, a display layer and a control module. The display layer is disposed between the first glass layer and the second glass layer and includes an array of light emitting diodes, suspended particle devices, and at least one ambient light sensor. At least one ambient light sensor is configured to detect a level of ambient light at the display layer. The suspended particle devices are each configured to selectively provide different levels of transparency. The control module is configured to, based on an output of the at least one ambient light sensor, adjust a transparency level of at least a portion of the display layer. 
     In other features, the at least one ambient light sensor includes only a single ambient light sensor. 
     In other features, the at least one ambient light sensor includes ambient light sensors. 
     In other features, the at least one ambient light sensor is integrated in the display layer and is disposed within an outer periphery of the display layer. 
     In other features, each of the at least one ambient light sensor is disposed between two of the light emitting diodes of the array of light emitting diodes. 
     In other features, the at least one ambient light sensor is in a same layer of the smart glass display as the display layer and is disposed outside of a periphery of the display layer. 
     In other features, the at least one ambient light sensor includes exterior ambient light sensors and one or more interior ambient light sensors. 
     In other features, the control module includes: a comparator configured to obtain, based on the output of the at least one ambient light sensor, a brightness level; a vehicle message transceiver configured to obtain an image to display on the display layer; and an address driver configured to adjust brightness of at least a portion of the display layer based on the brightness level and drive the display layer to display the image. 
     In other features, the control module includes: a comparator configured to obtain a dimming level based on the output of the at least one ambient light sensor; a vehicle message transceiver configured to obtain an image to display on the display layer; an address driver configured to drive the display layer to display the image; and a shading driver configured to drive the suspended particle devices to adjust the transparency level of at least the portion of the smart glass display based on the dimming level. 
     Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG.  1 A  is a cross-sectional side view of an example window with integrated smart glass display including a single exterior ambient light sensor according to the present disclosure; 
         FIG.  1 B  is a front view of the window of  FIG.  1 A ; 
         FIG.  2 A  is a side cross-sectional side view of an example window with integrated smart glass display including multiple exterior ambient light sensors disposed within a perimeter of a display layer according to the present disclosure; 
         FIG.  2 B  is a front view of the window of  FIG.  2 A ; 
         FIG.  3 A  is a side cross-sectional side view of an example window with integrated smart glass display including multiple exterior ambient light sensors disposed outside of a perimeter of a display layer according to the present disclosure; 
         FIG.  3 B  is a front view of the window of  FIG.  3 A ; 
         FIG.  4 A  is a side cross-sectional side view of an example window with integrated smart glass display including multiple exterior ambient light sensors and an interior ambient light sensor according to the present disclosure; 
         FIG.  4 B  is a front view of the window of  FIG.  4 A ; 
         FIG.  5    is a functional block diagram of an example of a contrast control system for a smart glass display according to the present disclosure; 
         FIG.  6    is a functional block diagram of an example auto-shading look-up table 
       (LUT) calibration system according to the present disclosure; 
         FIG.  7    illustrates a contrast control method according to the present disclosure; 
         FIG.  8    illustrates an auto-shading calibration method according to the present disclosure; 
         FIG.  9    is an example of a display including exterior and interior ambient light sensors according to the present disclosure; 
         FIG.  10    is a side cross-sectional view of an auto-shading layer in a transparent mode according to the present disclosure; 
         FIG.  11    is a side cross-sectional view of the auto-shading layer of  FIG.  10    in a dimming mode according to the present disclosure; 
         FIG.  12    is an example of a display including an array of light emitting diodes (LEDs), rows of suspended particle devices (SPDs), and exterior and interior ambient light sensors according to the present disclosure; 
         FIG.  13    is an example of a display including an array of light emitting diodes (LEDs), rows and columns of suspended particle devices (SPDs), and exterior and interior ambient light sensors according to the present disclosure; 
         FIG.  14    is a side cross-sectional view of combined display and auto-shading layer in a transparent mode including LEDs and/or ambient light sensors according to the present disclosure; 
         FIG.  15    is a side cross-sectional view of the combined display and auto-shading layer of  FIG.  14    in a dimming mode according to the present disclosure; and 
         FIG.  16    is a front view of a window including an integrated smart glass display including another pattern of ambient light sensors according to the present disclosure. 
     
    
    
     In the drawings, reference numbers may be reused to identify similar and/or identical elements. 
     DETAILED DESCRIPTION 
     The present disclosure relates to a display devices able to operate in transparent and non-transparent modes with high contrast ratios. While the foregoing description relates to display devices and systems for vehicles, the display devices and systems described herein are applicable in other applications such as residential homes, commercial buildings, computer games, etc. The examples disclosed herein are applicable to automotive glass and non-automotive glass including architectural glass. The examples may be applied to any window of a vehicle including front, side and back windows, sunroofs and moon roofs. 
     A display device can be made transparent by arranging selectively transparent spaces between pixels of the display device and controlling the transparency or opacity thereof. Smaller scale display technologies such as micro light emitting diodes (LEDs) have more opportunity to make higher transparency display devices. However, the higher transparency of the display device reduces the contrast ratio due to undesired lighting from surroundings. For example, when the display is exposed to high ambient light conditions such as sunlight, readability worsens. 
     Auto-shading devices can be used to change light transmittance from transparent to opaque by applying voltage to embedded electrodes or not applying voltage to the embedded electrodes. This allows the background of an image to be darkened to adjust the contrast ratio of the image. Examples of auto-shading technologies include suspended particle devices and/or electrochromic devices. Outer transparent layers of glass or film are separated by spacers. Transparent conductive coatings or layers are arranged on inwardly facing surfaces of the outer transparent layers. Suspended particles are located between the conductive coatings or layers. When the voltage is applied to the electrodes, the particles align with the applied field and the corresponding portions are transparent. When the voltage is not applied to the electrodes, the particles return to their original orientation and the corresponding portions are opaque. Various levels of transparency may be provided by varying the voltages. 
     The smart glass display devices (or simply “smart glass displays”) according to the present disclosure provide high selective contrast ratios relative to other transparent display devices. Locally disposed ambient light sensors are integrated in the smart glass displays and are used for selective global and local control over contrast ratios. This includes adjusting contrast ratios of specific cells and/or zones of the smart glass displays. Each cell may include one or more LEDs (or LED transistor circuits) and each zone may include one or more cells. 
     Methods are disclosed herein for automatically adjusting smart glass display brightness (or intensity) and auto-shading levels based on signals from laminated ambient light sensors. Control algorithms are implemented to change display brightness levels and auto-shading levels of the corresponding smart glass display based on exterior and interior lighting conditions. By being integrated in the smart glass displays, the laminated ambient light sensors measure light levels directly in front of and/or behind the smart glass display. Smart glass display control systems provide localized and global brightness and auto-shading level control of the smart glass displays. In some examples, multiple exterior ambient light sensors and one or more interior ambient light sensors are integrated into the smart glass displays. Auto-shading layers are included in the smart glass displays to locally control auto-shading levels. In some examples and depending on the layer stack-up and arrangement of the smart glass display, a dimming level calibration method is implemented to calibrate interior ambient light sensor(s) including determining the true interior ambient light levels and compensating for set auto-dimming levels. 
     By incorporating the ambient light sensors in the smart glass displays, the smart glass displays are not over or under driven based on ambient lighting conditions which is a concern for readability of a transparent display. The ambient light sensors provide an accurate measurement of ambient light levels on the smart glass displays. This is unlike a system that includes ambient light sensors in front of or above an interior cabin of a vehicle or located within an interior cabin of a vehicle, such as on a dashboard. Ambient light sensors in these locations do not provide accurate ambient light measurements for use in controlling brightness levels and/or auto-shading levels of transparent displays. 
       FIGS.  1 A- 1 B  show a window  100  with integrated smart glass display  102  including a single exterior ambient light sensor  104 . The window  100  includes a front (or exterior) glass layer  106  and a back (or interior) glass layer  108 . The smart glass display  102  includes a display layer  110  and an auto-shading layer  112 , which are disposed between the glass layers  106 ,  108 . A first resin layer  114  may be disposed between the front glass layer  106  and the display layer  110 . The ambient light sensor  104  and the display layer  110  may be disposed on and connected to a substrate  116 . The auto-shading layer  112  includes a transparency control layer  120  disposed between two resin layers  122 ,  124 . The auto-shading layer  112  is disposed between the substrate  116  and the back glass layer  108 . As an example, the resin layers  114 ,  122 ,  124  may be formed of polyvinyl butyral (PVB). 
     Exterior ambient light, represented by arrow  126 , is detected by the ambient light sensor  104 . A control module  130  receives an ambient light signal from the ambient light sensor  104  and adjusts a brightness level of the display layer  110  and/or a dimming level of the auto-shading layer  112  via the transparency control layer  120 . This may be accomplished by adjusting voltages supplied to the display layer  110  and the auto-shading layer  112 . This is described in further detail below. The ambient light sensor  104  may be disposed anywhere around the periphery of the display  102  or may be integrated in the display layer  110 , as further described below. 
     In this example, the single embedded ambient light sensor  104  is used for global control of the brightness of the display layer  110  and the dimming of the auto-shading layer  112 . In some embodiments, the example of  FIGS.  1 A- 1 B  are applied to side windows of a vehicle. This control may be used to save power consumed in displaying images by decreasing brightness levels in darker ambient lighting conditions. Brightness may be increased when conditions call for increased brightness levels, such as when the window  100  is facing the sun. 
     The display layer  110  may be an exterior facing or an interior facing display layer  110 . In an embodiment, the display layer  110  displays an image to a person external to a vehicle, which includes the window  100 . In an embodiment, the display layer  110  displays an image to a person internal to a vehicle, which includes the window  100 . 
       FIGS.  2 A- 2 B  show a window  200  with integrated smart glass display  202  including multiple exterior ambient light sensors  204  disposed within a perimeter of a display layer  205 . The window  200  includes a front (or exterior) glass layer  206  and a back (or interior) glass layer  208 . The smart glass display  202  includes the display layer  205  and an auto-shading layer  212 , which are disposed between the glass layers  206 ,  208 . A first resin layer  214  may be disposed between the front glass layer  206  and the display layer  205 . The ambient light sensors  204  and display layer  205  are disposed on and connected to a substrate  216 . The auto-shading layer  212  includes a transparency control layer  220  disposed between two resin layers  222 ,  224 . The auto-shading layer  212  is disposed between the substrate  216  and the back glass layer  208 . As an example, the resin layers  214 ,  222 ,  224  may be formed of PVB. 
     Exterior ambient light, represented by arrows  226 , is detected by the ambient light sensors  204 . A control module  230  receives ambient light signals from the ambient light sensors  204  and adjusts one or more brightness levels of the display layer  205  and/or one or more dimming levels of the auto-shading layer  212  via the transparency control layer  220 . This is described in further detail below. The ambient light sensors  204  may be disposed anywhere within the periphery of the display layer  205 . 
     Although a particular number of ambient light sensors  204  are shown, any number of ambient light sensors may be included. In one embodiment, a matrix (or array) of ambient light sensors are included. Each of the ambient light sensors  204  may have corresponding areas  240 , within which, for example, brightness levels of LEDs and/or a dimming level of a portion of the auto-shading layer  212  are set based on the output of that ambient light sensors  204 . For example, brightness levels of LEDs of the display layer  205  within one of the areas  240  may be the same and set directly based on the output of the ambient light sensor associated with that area. A dimming level of the portion of the auto-shading layer  212  directly adjacent to and opposing the area of the ambient light sensor associated with that area may be directly set based on the output of that ambient light sensor. Brightness levels of other areas (i.e. areas of the display layer  205  that are between the areas  240 ) and dimming levels of other areas of the auto-shading layer  212  (i.e. areas not adjacent and opposite the areas  240 ) may be set based on outputs of the ambient light sensors  204  using interpolation, triangulation, weighting, etc. Ambient light levels in areas outside the areas  240  may be estimated and brightness levels and dimming levels are then set based on the estimated ambient light levels. 
     The display layer  205  may be an exterior facing or an interior facing display layer  205 . In an embodiment, the display layer  205  displays an image to a person external to a vehicle, which includes the window  200 . In an embodiment, the display layer  205  displays an image to a person internal to a vehicle, which includes the window  200 . 
     The example of  FIGS.  2 A- 2 B  include a multi (or matrix) embedded ambient light sensor display device that allows for estimating ambient light levels experienced across the display layer  205 . The control module  230  may perform triangulation to determine locations of selected points on the display layer  205  that are between the ambient light sensors  204 . The locations of the ambient light sensors  204  are known and may be used to determine locations of the selected points. Ambient light levels at these points may be estimated using interpolation, distances between the points and the ambient light sensors, and based on the ambient light levels measured by the ambient light sensors  204 . This information may be used to provide more accurate data for global dimming control or to perform localized diming control based on detailed exterior ambient light conditions across the display layer  205 . The smart glass display  202  is thus able to be locally or segmentally brightened and/or dimmed to account for non-uniform lighting conditions. 
     The inclusion of multiple ambient light sensors provides more accurate data for improved global and/or localized brightness and/or dimming control. The multiple ambient sensors may be used for: localized ambient light measurements; verifying accuracy of each of the ambient light sensors; and/or backing up data collected from each of the ambient light sensors. For example, if a first ambient light sensor is detecting a high level of light and a second ambient light sensor is detecting a low level of light, opposite brightness and dimming actions may be performed in a first area around the first ambient light sensor than brightness and dimming actions performed in an area around the second ambient light sensor. As another example, if the four ambient light sensors near the periphery (or corners) of the display layer  205  detect a high level of ambient light and the center located ambient light sensor detects a low level of light, then it is likely that the center ambient light sensor is operating inappropriately. Localized brightness and dimming control may be performed to compensate for detected light “hot spots” and glare. For example, brightness in one or more zones of the display layer  205  may be increased to overcome light from nearby street lamps, which are causing one or more bright spots on the front glass layer  206  and display layer  205 . 
       FIGS.  3 A- 3 B  show a window  300  with integrated smart glass display  302  including multiple exterior ambient light sensors  304  disposed outside of a perimeter of a display layer  305 . The window  300  includes a front (or exterior) glass layer  306  and a back (or interior) glass layer  308 . The smart glass display  302  includes the display layer  305  and an auto-shading layer  312 , which are disposed between the glass layers  306 ,  308 . A first resin layer  314  may be disposed between the front glass layer  306  and the display layer  305 . The ambient light sensors  304  and the display layer  305  may be disposed on and connected to a substrate  316 . The auto-shading layer  312  includes a transparency control layer  320  disposed between two resin layers  322 ,  324 . The auto-shading layer  312  is disposed between the substrate  316  and the back glass layer  308 . As an example, the resin layers  314 ,  322 ,  324  may be formed of PVB. 
     Exterior ambient light, represented by arrows  326 , is detected by the ambient light sensors  304 . A control module  330  receives ambient light signals from the ambient light sensors  304  and adjusts one or more brightness levels of the display layer  305  and/or one or more dimming levels of the auto-shading layer  312  via the transparency control layer  320 . This is described in further detail below. The ambient light sensors  304  may be disposed external to and around a periphery of the display layer  305 . 
     Each of the ambient light sensors  304  may be used to estimate ambient light levels at points across the display layer  305 . Brightness levels of areas of the display layer  305  and dimming levels of areas of the auto-shading layer  312  may be set based on outputs of the ambient light sensors  304  using interpolation, triangulation, weighting, etc. Ambient light levels in areas of the display layer  305  that are away from the ambient light sensors  304  may be estimated and brightness levels and dimming levels are then set based on the estimated ambient light levels. 
     The display layer  305  may be an exterior facing or an interior facing display layer  305 . In an embodiment, the display layer  305  displays an image to a person external to a vehicle, which includes the window  300 . In an embodiment, the display layer  305  displays an image to a person internal to a vehicle, which includes the window  300 . 
       FIGS.  4 A- 4 B  show a window  400  with integrated smart glass display  402  including multiple exterior ambient light sensors  404  and an interior ambient light sensor  407 . The window  400  includes a front (or exterior) glass layer  406  and a back (or interior) glass layer  408 . The smart glass display  402  includes a display layer  410  and an auto-shading layer  412 , which are disposed between the glass layers  406 ,  408 . A first resin layer  414  may be disposed between the front glass layer  406  and the display layer  410 . The ambient light sensors  404  and  407  and the display layer  410  may be disposed on and connected to a substrate  416 . The auto-shading layer  412  includes a transparency control layer  420  disposed between two resin layers  422 ,  424 . The auto-shading layer  412  is disposed between the substrate  416  and the back glass layer  408 . As an example, the resin layers  414 ,  422 ,  424  may be formed of PVB. 
     Exterior ambient light, represented by arrows  426 , is detected by the ambient light sensors  404 . Interior ambient light, represented by arrows  428 , is detected by the ambient light sensors  407 . A control module  430  receives ambient light signals from the ambient light sensors  404 ,  407  and adjusts one or more brightness levels of the display layer  410  and/or one or more dimming levels of the auto-shading layer  412  via the transparency control layer  420 . This is described in further detail below. The exterior ambient light sensors  404  may be disposed within a periphery of the display layer  410 , as shown, or disposed external to and around a periphery of the display layer  410 . The interior ambient light sensor  407  may be disposed external to and along the periphery of the display layer  410  or may be disposed within a periphery of the display layer  410 . 
     Although a particular number of exterior ambient light sensors and a particular number of interior ambient light sensors are shown, any number of each may be included. Since the variance in exterior ambient light across the display layer  410  can be high and the variance in interior ambient light across the display layer  410  is typically minimal, fewer interior ambient light sensors (e.g.,  1 - 2 ) than exterior light sensors (e.g.,  1 - 10 ) may be included. The interior ambient light sensors allow the control module  430  to detect when, for example, an interior room or cabin is brightly lit up by the sun or other sources of light and compensate for that by adjusting the contrast ratio(s) of the smart glass display. 
     Each of the ambient light sensors  404 ,  407  may be used to estimate ambient light levels at points across the display layer  410 . Brightness levels of areas of the display layer  410  and dimming levels of areas of the auto-shading layer  412  may be set based on outputs of the ambient light sensors  404  using interpolation, triangulation, weighting, etc. Ambient light levels in areas of the display layer  410  that are away from the ambient light sensors  404  may be estimated based on the outputs of the ambient light sensors  404  and brightness levels and dimming levels are then set based on the estimated ambient light levels. By gathering information on interior and exterior ambient lighting directly at the smart glass display  402  allows for adjusting brightness and auto-shading to provide high contrast ratios across the smart glass display  402 . If the display layer  410  is outward facing and the interior of the vehicle is bright, brightness levels of the display layer  410  may be increased and dimming levels of the auto-shading layer  412  may be increased to increase the contrast ratio(s) of the smart glass display  402  for improved viewing of an image displayed on the display layer  410 . 
     The display layer  410  may be an exterior facing or an interior facing display layer  410 . In an embodiment, the display layer  410  displays an image to a person external to a vehicle, which includes the window  400 . In an embodiment, the display layer  410  displays an image to a person internal to a vehicle, which includes the window  400 . 
     The interior ambient light sensor and/or additional interior ambient light sensors may be incorporated in the examples of  FIGS.  1 A- 3 B . 
       FIG.  5    shows a contrast control system  500  for a smart glass display  502 . The smart glass display  502  may be implemented as any of the smart glass displays disclosed herein (e.g., any of the smart glass displays of  FIGS.  1 A- 4 B,  9 ,  12 - 13  and  16    and/or variations thereof). The contrast control system  500  includes a control module  504 , which may replace and/or operate similarly as any of the other control modules disclosed herein, a memory  506  and a power source  507 . The control module  504  may include a general purpose input/output (GPIO) interface  510 , a first comparator  512 , a vehicle message transceiver  514 , a LED address driver  516  and a shading driver  518 . The smart glass display  502  may include laminated glass (not shown), a LED display layer  520 , an auto-shading layer  522 , one or more exterior ambient light sensors  524 , and one or more interior ambient light sensors  526 . The memory  506  may store one or more brightness and/or dimming look-up tables (LUTs)  530  (or database). The brightness and dimming LUTs relate ambient light levels to brightness and dimming levels. A vehicle bus and/or communication interface  532  may be included and communicate with the vehicle message transceiver  514 . Operation of the contrast control system  500  is further described below with respect to the method of  FIG.  7   . The power source  507  may include a battery pack and be a stand-alone power source or may receive power from an external power source. The power source  507  may receive utility power. 
       FIG.  6    shows an auto-shading LUT calibration system  600 . The auto-shading LUT calibration system  600  may include the shading driver  518 , the one or more interior ambient light sensors  526 , a second comparator  602 , a memory  604  and the memory  506 . The second comparator  602  may be implemented in the control module  504  of  FIG.  5   . The memory  604  and the memory  506  may be implemented together as a single memory. The memory  604  may store a calibration table, such as that shown below as Table 1, where N is an integer. The calibration table may relate auto-shading levels to multipliers. This may include global and/or local multipliers. The memory  506  may store a dimming LUT  608 , which may be a portion of or separate from a brightness and dimming LUT. Operation of auto-shading LUT calibration system  600  is further described below with respect to the method of  FIG.  7   . 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Auto-shading Level to Multiplier Conversion 
               
            
           
           
               
               
               
            
               
                   
                 Auto-shading Level 
                 Multiplier M i   
               
               
                   
                   
               
               
                   
                 ASL 1   
                 M 1   
               
               
                   
                 ASL 2   
                 M 2   
               
               
                   
                 ASL 3   
                 M 3   
               
               
                   
                 . . . 
                 . . . 
               
               
                   
                 ASL N   
                 M N   
               
               
                   
                   
               
            
           
         
       
     
       FIG.  7    shows a contrast control method. Although the following operations are primarily described with respect to the contrast control system  500  of  FIG.  5   , the operations are applicable to the other embodiments disclosed herein. The following operations may be iteratively performed. The method may begin at  700 . 
     At  702 , exterior and/or interior ambient light levels are detected via the sensors  524 ,  526 . The GPIO interface  510  may receive signals from the one or more exterior ambient light sensors  524  and/or the one or more interior ambient light sensors  526 . This may include receiving signals from any of the ambient light sensors shown in  FIGS.  1 A- 4 B,  9 ,  12 - 13    and/or referred to herein. 
     At  704 , the control module  504  may determine whether auto-shading is ON. If yes, operation  706  may be performed, otherwise operation  708  may be performed. At  706 , the control module  504  may perform an auto-shading LUT calibration method, as described below with respect to  FIG.  8   . 
     At  708 , the first comparator may compare the exterior and interior ambient light levels to one or more brightness and dimming LUT(s) to provide one or more brightness levels and/or one or more dimming levels. The brightness levels are provided to the vehicle message transceiver  514  and/or the LED address driver  516 . The dimming levels are provided to the shading driver  518 . The control module  504  and/or the comparator  512  may determine a brightness profile across the smart glass display and set the brightness levels and/or the dimming levels accordingly to provide high contrast ratios across the smart glass display. 
     At  710 , the vehicle message transceiver  514  receives an image to be displayed on the LED display layer  520 , which may be any of the display layers shown and/or described with respect to  FIGS.  1 A- 4 B,  9  and  12 - 13   . As a few examples, images to be displayed may be obtained by the control module  504 , received from the vehicle bus and/or communication interface  532 , and/or obtained from a memory (e.g., the memory  506 ). The images may be for advertising, ride-hailing, and/or communication purposes. The images may be for individuals outside or inside of a vehicle. 
     At  712 , the LED address driver  516  drives the LED display layer  520  to display the images obtained by the vehicle message transceiver  514  and based on the brightness levels received from the first comparator  512  and/or the vehicle message transceiver  514 . 
     At  714 , the shading driver  518  generates auto-shading signals to control SPDs of the auto-shading layer  522  based on the dimming levels received from the shading driver. The dimming levels received from the first comparator  512  at the shading driver  518  are converted to auto-shading levels and/or output voltages that are provided to the SPDs of the auto-shading layer  522 . The auto-shading levels are used to set a levels of transparency or tint levels of cells and/or zones of the auto-shading layer. Each cell may include one or more SPDs and each zone may include one or more cells. Operation  714  may be performed while operation  712  is performed. Operation  702  may be performed subsequent to operations  712 ,  714 . 
       FIG.  8    shows an auto-shading calibration method. Although the following operations are primarily described with respect to the auto-shading LUT calibration system  600  of  FIGS.  5 - 6   , the operations are applicable to the other embodiments disclosed herein. The following operations may be iteratively performed. Although the following operations are described with respect to a single un-calibrated interior ambient light level UL, a single auto-shading level and a single calibrated interior ambient light level CL, the operations may be performed for multiple un-calibrated interior ambient light levels from multiple ambient light sensors and/or multiple auto-shading levels for multiple zones to provide multiple calibrated interior ambient light levels. 
     The method may begin at  800 . At  802 , an un-calibrated interior ambient light level UL are detected respectively via one of the interior ambient light sensors  526 . 
     At  804 , the shading driver  518  may obtain one or more initial, previous, and/or default auto-shading levels i. At  806 , the second comparator  602  determines a multiplier M based on the auto-shading level i, where i is an integer. The second comparator  602  may compare the auto-shading level i to other auto-shading levels in Table 1 to determine the multiplier M. 
     At  808 , the second comparator  602  generates a calibrated interior ambient light level CL. The calibrated interior ambient light level CL may be generated using equation 1. 
       CL=UL×Mi, where M≥1   (1)
 
     At  810 , the second comparator  602  updates the dimming LUT  608  in the memory  506 , which may then be used by the shading driver  518  when adjusting a dimming level of the auto-shading layer  522 . The method may end at  812  subsequent to operation  810 . 
     The method of  FIG.  8    compensates for when an auto-shading layer is disposed between (i) a display layer, which includes an interior ambient light sensor, and (ii) a background of the smart glass display and/or a rear glass layer of the smart glass display. The background may refer to an interior of a vehicle for an outward facing display or an exterior of the vehicle for an inward facing display. When in this arrangement and when auto-shading is active, the interior ambient light sensor may not detect the actual interior ambient light level due to the dimming of the auto-shading layer. The method of  FIG.  8    increases the un-calibrated interior ambient light level to the calibrated interior ambient light level based on the level of dimming to provide an estimate of the actual interior ambient light level. When the display layer and the auto-shading layer are integrated into a single layer as shown in  FIGS.  12 - 13   , the method of  FIG.  8    may not be performed. 
       FIG.  9    shows a display  900  including exterior ambient light sensors  902  and an interior ambient light sensor  904 . The display  900  includes a data line  908 , a scan line  910 , and an array of light emitting diodes (LED) transistor circuits  912 - 11 , . . . , and  912 -NM, where N and M are integers (collectively LED transistor circuits  912 ) where N and M are integers. A display controller (or control module)  950  communicates with the data line  908  and the scan line  910 . Electrodes  930  and  932  connect the data line  908  and scan line  910  to the LED transistor circuits  912 . The display controller  950  executes a display application that selectively provides power to the LED transistor circuits  912 . The LED transistor circuits may each include a LED, a transistor and/or other passive circuit elements. 
     The color of each of the LEDs of the LED transistor circuits  912  can be displayed in an on/off mode or at varying intensities between fully on and fully off. In the example shown, the LEDs of the LED transistor circuits  912  in each row vary in color (e.g. red, green and blue and then repeat) to form pixels. In some examples, the display  900  forms part of a windshield, rear glass, side windows, instrument panel, infotainment display, rearview mirror or other window or display. 
     While an N×M rectangular array is shown, non-uniform layouts can be used with other shapes. Selectively transparent spaces corresponding to SPDs in another layer (not shown), such as one of the auto-shading layers in  FIGS.  1 A- 4 B . The selectively transparent spaces can be configured to be transparent to opaque depending upon applied voltage to SPD electrodes as will be described further below. 
     The display controller  950  is configured to run the display application  952  that controls the LED transistor circuits  912  and SPD electrodes of the display  900  based on outputs of the sensors  902 ,  904 . The display application  952  also controls power supplied to the SPD electrodes. In some examples, the display application  952  selectively controls switches to apply voltage to the SPD electrodes that determine whether or not the selectively transparent spaces are transparent or opaque based on sensed data such as ambient light conditions or other information. 
       FIGS.  10 - 11    show an auto-shading layer  1000  of a transparent display device respectively in a transparent mode (auto-shading off) and a dimming mode (auto-shading on). The dimming mode provides different levels of transparency and may be referred to as a non-transparent or opaque mode when the dimming level is high and no light is passing through the auto-shading layer  1000 . The auto-shading layer  1000  may replace one of the auto-shading layers of  FIGS.  1 A- 4 B . 
     The auto-shading layer  1000  includes suspended particles. In some examples, the auto-shading layer  1000  includes a display side  1006  adjacent a display layer (not shown) and an opposite side  1008 . The auto-shading layer  1000  may include one or more zones  1010  (three zones  1010   a - c  are shown) with the same or different levels of transparency (or dimming). Any number of zones may be included. 
     The auto-shading layer  1000  includes transparent layers  1014  and  1016  that are spaced apart by a predetermined distance in a direction transverse to a viewing direction of the auto-shading layer  1000 . In some examples, the transparent layers  1014  and  1016  are made of glass, transparent resin film or other transparent material. In some examples, the zones  1010  are spaced apart by spacers  1022 . 
     In the zones  1010 , transparent conductive coatings or layers  1020  and  1024  are arranged in a pattern on inner, facing surfaces of the transparent layers  1014  and  1016 . Suspended particles  1028  are located between the conductive coatings or layers  1020  and  1024 . A display controller (or control module) selectively applies a voltage across the conductive coatings or layers  1020  and  1024  to change a level of transparency of the selectively zones  1010 . 
     When a voltage potential is applied across the transparent conductive coatings or layers  1020  and  1024 , the suspended particles align with the applied field and the selectively transparent region  1010  will be transparent as shown in  FIG.  10   . When the voltage potential is removed, the suspended particles  1028  return to a disordered state and the selectively transparent region  1010  will be obscured by the suspended particles  1028  as shown in  FIG.  11   . 
     In some examples, the suspended particles include crystals that are about 0.3 to 0.5 microns (μm) in length, although other types of particles can be used. The crystals act as induced dipoles when an electric field is applied to the conductive coatings or layers in the film. When the electric field is applied, the crystals line up and allow light to pass through. When the electric field is removed, the natural tendency of the crystals is to be misaligned due to Brownian movement. The misaligned crystals cause the glass to tint. 
     Auto-shading activation can be controlled based upon the occurrence of one or more events. For example, auto-shading can be transparent when measured ambient light sensed by ambient light sensors is less than a predetermined threshold and opaque when the ambient light is greater than the predetermined threshold. In other examples, auto-shading can be activated or deactivated in response to the presence or absence of an occupant inside the vehicle. Auto-shading can be activated or deactivated when the vehicle is started or in motion. For example, the auto-shading is deactivated when ambient light or interior light is too dim or nobody is in the car for interior facing display applications. 
       FIG.  12    shows a display  1200  including an array of LED transistor circuits  1212 , rows of suspended particle devices (SPDs)  1216 , exterior ambient sensors  1202 , and an interior ambient light sensor  1204 . The display  1200  includes a data line  1208 , a scan line  1210 , and an array of LED transistor circuits  1212 - 11 , . . . , and  1212 -NM, where N and M are integers (collectively LED transistor circuits  1212 ) where N and M are integers. A display controller  1250  communicates with the data line  1208  and the scan line  1210 . Electrodes  1230  and  1232  connect the data line  1208  and scan line  1210  to the LED transistor circuits  1212  and SPDs  1216 - 1 ,  1216 - 2 , . . .  1216 -N (collectively SPDs  1216 ) between first rows of the LED transistor circuits  1212 . The LED transistor circuits  1212  are arranged in rows. The SPDs are arranged in second rows and are each disposed between adjacent pairs of the first rows. A display controller  1250  executes a display application  1252  that selectively provides power to the LED transistor circuits  1212  and/or to the SPDs  1216 . 
     The color of each of the LEDs of the LED transistor circuits  1212  can be displayed in an on/off mode or at varying intensities between fully on and fully off. In the example shown, the LEDs of the transistor circuits  1212  in each row vary in color (e.g. red, green and blue and then repeat) to form pixels. In some examples, the display  1200  forms part of a windshield, rear glass, side windows, instrument panel, infotainment display, rearview mirror or other window or display. 
     While an N x M rectangular array is shown, non-uniform layouts can be used with other shapes. Selectively transparent spaces corresponding to the SPDs  1216  are arranged between the LED transistor circuits  1212 . The selectively transparent spaces can be configured to be transparent to opaque depending upon applied voltage to the SPDs as will be described further below. As will be described further below, the selectively transparent spaces and the LED transistor circuits  1212  are arranged in the same plane located between transparent layers as will be described further below in  FIGS.  14 - 15   . 
       FIG.  13    shows a display  1300  including an array of LED transistor circuits  1362 , rows and columns of suspended particle devices (SPDs)  1366 , exterior ambient light sensors  1302 , and an interior ambient light sensor  1304 . The LED transistor circuits  1362  and SPDs  1366  alternate in both row and/or column directions. The display  1300  include a data line  1308 , a scan line  1310 , an array of LED transistor circuits  1362 - 11 ,  1362 - 12 , . . . , and  1362 -NM (collectively LED transistor circuits  1362 ) and an array of SPDs  1366 - 11 ,  1366 - 12 , . . . , and  1366 -NM (collectively SPDs  1366 ). Electrodes  1330  and  1332  connect the data line  1308  and scan line  1310  to the LED transistor circuits  1362  and SPDs  1366 . In each row and/or column, the LED transistor circuits  1362  alternate with the SPDs  1366 . In some examples, adjacent rows are aligned with each other or offset from each other to create an alternating pattern in each row and column. A display controller  1350  executes a display application  1352  that selectively provides power to the LED transistor circuits  1362  and/or to the SPDs  1366 . 
       FIGS.  14 - 15    shows a combined display and auto-shading layer  1400  including LED transistor circuits  1402  (one LED transistor circuit  1402  is shown) and/or ambient light sensors  1404  (one ambient light sensor is shown), which may include exterior and/or interior ambient light sensors.  FIG.  14    shows the display and auto-shading layer in a transparent mode (auto-shading off).  FIG.  15    shows the display and auto-shading layer in a dimming mode (auto-shading on). The display and auto-shading layer  1400  includes suspended particles arranged in spaces located between LED transistor circuits, ambient light sensors and/or pixels (including multiple LED transistor circuits). In some examples, the display and auto-shading layer  1400  includes a display side  1406  and an opposite side  1408 . The display and auto-shading layer  1400  includes selectively transparent regions  1410  and LED/pixel regions  1412 . In some examples, the LED/pixel regions  1412  are arranged in an array and are spaced apart at regular intervals by the transparent regions, although non-uniform spacing or other arrangements of pixels can be used. 
     The display and auto-shading layer  1400  includes transparent layers  1414  and  1416  that are spaced apart by a predetermined distance in a direction transverse to a viewing direction of the display and auto-shading layer  1400 . In some examples, the transparent layers  1414  and  1416  are made of glass, transparent film or other transparent material. In some examples, the transparent regions  1410  are spaced apart by spacers  1422  that are located between the selectively transparent regions  1410  and the LED/pixel regions  1412 . 
     In the selectively transparent regions  1410 , transparent conductive coatings or layers  1420  and  1424  are arranged in a pattern on inner, facing surfaces of the transparent layers  1414  and  1416 . Suspended particles  1428  are located between the conductive coatings or layers  1420  and  1424 . A display controller selectively applies a voltage across the conductive coatings or layers  1420  and  1424  to change a level of transparency of the selectively transparent regions  1410 . 
     When a voltage potential is applied across the transparent conductive coatings or layers  1420  and  1424 , the suspended particles align with the applied field and the selectively transparent region  1410  will be transparent as shown in  FIG.  14   . When the voltage potential is removed, the suspended particles  1428  return to a disordered state and the selectively transparent region  1410  will be obscured by the suspended particles  1428  as shown in  FIG.  15   . 
     The LED/pixel regions  1412  are located between the selectively transparent regions  1410 . Each of the LED/pixel regions  1412  includes one or more electrodes  1472  on which is disposed the LED transistor circuits  1402  and the ambient light sensors  1404 . For example only, each of the LED/pixel regions  1412  may have LED transistor circuits including respectively red, green and blue LEDs. 
       FIG.  16    shows a window  1600  including an integrated smart glass display  1602  including another example pattern of exterior ambient light sensors  1604 , which may be arranged in an array across a surface of the smart glass display  1602  and have respective zones  1608 . The smart glass display  1602  may be configured similarly as other smart glass displays disclosed herein and include a display layer and an auto-shading layer. The display layer and the auto-shading layer may be integrated into a single layer or may be separate layers. The display layer may include the exterior ambient light sensors  1604  and an interior ambient light sensor  1610 . 
     The displays referred to herein may include mini LEDs, micro LEDs, organic light emitting diodes (OLEDs), and/or other light sources. The ambient light sensors referred to herein may be implemented as phototransistors and laminated in glass. The exterior ambient light sensors referred to herein are outward facing sensors. The interior ambient light sensors referred to herein are inward facing sensors. The glass layers referred to herein may include laminated glass. By incorporating the ambient light sensors in a same layer as a display layer, the examples disclosed herein minimize the number of layers stacked to form a smart glass display and ease manufacturing. It is easier to incorporate the sensors in a layer that includes circuit elements as opposed to another layer that is passive and does not include circuit elements. 
     The examples disclosed herein allow for global and local adjustment of brightness levels and auto-shading levels to control transparency and contrast ratios of displays for improved visualization of displayed images. Global adjustment refers to adjusting a brightness level of an entire display layer and/or adjusting an auto-shading level of an entire auto-shading layer. Local adjustment refers to adjusting brightness levels of cells and/or zones differently of a display layer and/or adjusting auto-shading levels of cells and/or zones differently of an auto-shading layer. This holds true when the display layer and the auto-shading layer are integrated together as a single layer. 
     The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. Further, although each of the embodiments is described above as having certain features, any one or more of those features described with respect to any embodiment of the disclosure can be implemented in and/or combined with features of any of the other embodiments, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with one another remain within the scope of this disclosure. 
     Spatial and functional relationships between elements (for example, between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including “connected,” “engaged,” “coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and “disposed.” Unless explicitly described as being “direct,” when a relationship between first and second elements is described in the above disclosure, that relationship can be a direct relationship where no other intervening elements are present between the first and second elements, but can also be an indirect relationship where one or more intervening elements are present (either spatially or functionally) between the first and second elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.” 
     In the figures, the direction of an arrow, as indicated by the arrowhead, generally demonstrates the flow of information (such as data or instructions) that is of interest to the illustration. For example, when element A and element B exchange a variety of information but information transmitted from element A to element B is relevant to the illustration, the arrow may point from element A to element B. This unidirectional arrow does not imply that no other information is transmitted from element B to element A. Further, for information sent from element A to element B, element B may send requests for, or receipt acknowledgements of, the information to element A. 
     In this application, including the definitions below, the term “module” or the term “controller” may be replaced with the term “circuit.” The term “module” may refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog/digital discrete circuit; a digital, analog, or mixed analog/digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip. 
     The module may include one or more interface circuits. In some examples, the interface circuits may include wired or wireless interfaces that are connected to a local area network (LAN), the Internet, a wide area network (WAN), or combinations thereof. The functionality of any given module of the present disclosure may be distributed among multiple modules that are connected via interface circuits. For example, multiple modules may allow load balancing. In a further example, a server (also known as remote, or cloud) module may accomplish some functionality on behalf of a client module. 
     The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, data structures, and/or objects. The term shared processor circuit encompasses a single processor circuit that executes some or all code from multiple modules. The term group processor circuit encompasses a processor circuit that, in combination with additional processor circuits, executes some or all code from one or more modules. References to multiple processor circuits encompass multiple processor circuits on discrete dies, multiple processor circuits on a single die, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or a combination of the above. The term shared memory circuit encompasses a single memory circuit that stores some or all code from multiple modules. The term group memory circuit encompasses a memory circuit that, in combination with additional memories, stores some or all code from one or more modules. 
     The term memory circuit is a subset of the term computer-readable medium. The term computer-readable medium, as used herein, does not encompass transitory electrical or electromagnetic signals propagating through a medium (such as on a carrier wave); the term computer-readable medium may therefore be considered tangible and non-transitory. Non-limiting examples of a non-transitory, tangible computer-readable medium are nonvolatile memory circuits (such as a flash memory circuit, an erasable programmable read-only memory circuit, or a mask read-only memory circuit), volatile memory circuits (such as a static random access memory circuit or a dynamic random access memory circuit), magnetic storage media (such as an analog or digital magnetic tape or a hard disk drive), and optical storage media (such as a CD, a DVD, or a Blu-ray Disc). 
     The apparatuses and methods described in this application may be partially or fully implemented by a special purpose computer created by configuring a general purpose computer to execute one or more particular functions embodied in computer programs. The functional blocks, flowchart components, and other elements described above serve as software specifications, which can be translated into the computer programs by the routine work of a skilled technician or programmer. 
     The computer programs include processor-executable instructions that are stored on at least one non-transitory, tangible computer-readable medium. The computer programs may also include or rely on stored data. The computer programs may encompass a basic input/output system (BIOS) that interacts with hardware of the special purpose computer, device drivers that interact with particular devices of the special purpose computer, one or more operating systems, user applications, background services, background applications, etc. 
     The computer programs may include: (i) descriptive text to be parsed, such as HTML (hypertext markup language), XML (extensible markup language), or JSON (JavaScript Object Notation) (ii) assembly code, (iii) object code generated from source code by a compiler, (iv) source code for execution by an interpreter, (v) source code for compilation and execution by a just-in-time compiler, etc. As examples only, source code may be written using syntax from languages including C, C++, C#, Objective-C, Swift, Haskell, Go, SQL, R, Lisp, Java®, Fortran, Perl, Pascal, Curl, OCaml, Javascript®, HTML5 (Hypertext Markup Language 5th revision), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash®, Visual Basic®, Lua, MATLAB, SIMULINK, and Python®.