Abstract:
A display apparatus includes a transparent electronic display such as a non-backlit LCD screen, a display area disposed behind the transparent electronic display, and a light source for illuminating the display area. When the light source is activated, the pixels of the LCD screen, and objects behind the screen, become visible. Various examples of the display apparatus include additional enhancements to the visual image and/or functionality. These enhancements include additional monitors for coordinated displays, user-controlled turntables with coordinated informational displays, parallax compensation, RFID sensors for identifying objects to be displayed, and switchable liquid crystal films and/or polarized mirror coatings to further control revealing and concealing of objects behind the screen. Some examples of the display apparatus may include an animal habitat. The animal habitat may be selectively revealed or concealed. The display apparatus may incorporate screen displays with animal movements for unique visual effects.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/722,155, which was filed on Nov. 3, 2012, and entitled “Display Apparatus Including a Transparent Electronic Monitor.” 
    
    
     TECHNICAL FIELD 
     The present invention relates to devices and methods for combining a transparent electronic monitor with a physical object to provide a unique visual display. 
     BACKGROUND INFORMATION 
     Advertisers and merchants have always sought to display their products in a manner that calls the attention of consumers to the desirable features of the products. Towards this end, various combinations of informational displays and visual displays of the product have been proposed. 
     One example of a display device is disclosed by US 2012/0038868. The display device includes a liquid crystal display (LCD) module having a light source disposed behind the module, and a polarizing plate disposed between the light source and LCD module. The display further includes a transparent reflector that is spaced from the LCD display. The transparent reflector polarizes the image from the LCD module, with the polarization being controlled by the distance between the LCD module and reflector, as well as the angle of the reflector with respect to the LCD module. Potential uses are generally described as combining an image and a real object with an image during an exhibition, magic show, or launching show. Environments for which the screen may be useful include stages, stores, offices, vehicles, public transportation, cellular phones, and personal digital assistants, although specific uses are not discussed beyond this list. Controlling the extent to which an object behind the screen is visible by controlling the transparency of the transparent reflector is also disclosed. The transparency is controlled by controlling the luminance of the light source. 
     US 2008/0192027 discloses an interactive window display. Acoustic sensors located in close proximity to the four corners of the window are utilized to detect the presence of a shopper in front of a storefront window. A transparent display is located within the store so that it is visible through the storefront window. The interior of the store is visible through the transparent display. Audio information may be provided to the exterior of the store. The system is programmed to respond to taps on the window with various incentives to enter the store, based on the locations of the taps. The display screen is preferably a transparent refractive panel upon which an image can be projected from the rear at an oblique angle, and displayed clearly toward the front. 
     US 2011/0163986 discloses a mobile device that displays content on a dual touch screen based on a transparent display. The touch screen includes touch sensors on both sides of the display. Transparency of the display is controlled by the brightness of the displayed colors. 
     US 2010/0002175 discloses a method of manufacturing a transparent display screen. The method attempts to balance the capability of displaying all colors on the screen while also transmitting light through the screen. A color conversion layer may be placed in a non-chroma state in order to transmit light through the panel, or in an opaque state in which the layer appears black, and blocks transmission of light. A color display layer may display various colors when the color conversion layer is in an opaque state. The device may also transmit a color while in a transparent state. 
     US 2012/0120007 discloses a transparent display apparatus. The display apparatus may include a touchscreen or proximity sensor for detecting the presence of an object in proximity to the display apparatus. A timing controller, scan driver, data driver, pixel unit, subject recognition unit, and data processor are provided. 
     US 2011/0128386 discloses an interactive device. The device includes a pair of infrared cameras, as well as a peripheral visible light camera, for detecting objects and movements on the opposite side of a screen. The user may interact with the display that is presented by the display screen by utilizing the movements of the user&#39;s hands, fingers, or a handheld object in close proximity to the screen. 
     Transparent electronic monitors presently exist in the form of non-backlit liquid crystal displays (LCD) made by Samsung and LG. Unlike a backlit LCD display, non-backlit LCD displays appear black in the absence of a separate lighting source to the rear of the LCD display. When a light source is provided, the content on the screen becomes visible, and the screen becomes transparent, so that objects behind the screen become visible. Although the basic idea of incorporating a transparent LCD screen into a retail or advertising product display is known, numerous possibilities exist for enhancing such product displays. Furthermore, such non-backlit LCD screens present opportunities to create many other unique visual displays, which are not limited to advertising or retail uses. 
     SUMMARY 
     Various examples of display devices providing different combinations of features and advantages are provided. The display devices include a display case having a floor, a pair of sides, a back, and usually a ceiling. The front of the display case is formed by a nonbacklit video display, for example, a presently available nonbacklit LCD display. The absence of backlighting makes such LCD displays transparent when a light source is positioned behind the LCD display. The light source is also necessary for viewing text or other indicia displayed on the nonbacklit LCD display. 
     One example of the display device includes a standard, backlit video display screen forming the back panel of the display case, and potentially serving as an illumination source for the non-backlit display, illuminating desired portions of the non-backlit display, and leaving the remaining portions of the non-backlit display opaque. 
     Another example of the display device includes a turntable disposed within the display case, as well as by user input device, and a central processing unit operatively connected to both the turntable, the user input device, and the nonbacklit display. A viewer may control the rotation of the turntable through the input device, with indicia on the nonbacklit display being adjusted accordingly. 
     Another example of the display device includes a camera or sensor&#39;s structured to detect a position of a viewer, as well as a central processing unit structured to move indicia displayed on the video display in response to the position of a viewer. Some examples may correct for parallax between the viewer, indicia displayed on the display screen, and the object within the display device. 
     Yet another example of the display device includes one or more sensors that are structured to read indicia that is disposed on an object that is placed within the display device. The display device may thereby determine the type of object placed within the display device. Furthermore, the specific location of the object within the display device may optionally be determined. 
     Another example of the display device utilizes a switchable LCD film disposed on the back of the non-backlit LCD display. The switchable LCD film permits the non-backlit LCD display to selectively appear black, to appear opaque while displaying indicia, and to appear transparent while displaying indicia. 
     A further example of the display device includes a polarized mirror disposed in front of the nonbacklit video display. 
     Another example of the display device utilizes the display case as an animal habitat. Some examples of the animal habitat utilize a switchable LCD film disposed on the back of the non-backlit LCD display, permitting viewers to selectively view indicia displayed on the non-backlit LCD display, or to view animals within the animal habitat. Other examples may include sensors for tracking the position and movement of animals within the animal habitat. This information permits the central processing unit to generate interesting or entertaining indicia that can be displayed on the non-backlit LCD display, and which move across the non-backlit LCD display in a manner that tracks animal movements. Still other examples of animal habitats may include further cameras or sensors for tracking viewers, so that the position of indicia on the non-backlit display screen can be adjusted to correct for parallax between the viewer, display screen indicia, and animal. 
     Various methods of utilizing the different examples of display devices are provided. One example includes providing a standard, backlit video display screen behind the nonbacklit video display screen. Preselected portions of the backlit video display are illuminated, thereby illuminating corresponding portions of the nonbacklit video display. Objects disposed between the two video displays are thereby visible only through the illuminated portion of the nonbacklit video display. 
     Another method includes providing a camera or sensor structured to detect a position of a viewer, and a central processing unit operatively connected to the camera or sensor and to the video display screen. Indicia displayed on the video display screen is moved in response to movements of the viewer. In some examples, movements of the displayed indicia may be done in a manner that reduces parallax between the viewer, the displayed indicia, and any object within the display case. 
     Yet another method includes providing a sensor within the display case that is structured to read and indicia disposed on an object to be placed within the display case. The type of objects displayed within the display case may thereby be identified automatically, with the indicia displayed on the video display screen selected accordingly. 
     A further method includes providing a switchable LCD film disposed on the back surface of the nonbacklit video display, as well as a power supply for the switchable LCD film and a light disposed behind the nonbacklit video display. With the switchable LCD film being present, but not powered, light passing through the nonbacklit video displays will enable viewing indicia displayed on the display screen, but the display screen will be opaque. When power is applied to the switchable LCD film, then the nonbacklit video display screen becomes transparent, permitting both the indicia displayed on the screen and objects behind the screen to be viewed. 
     A method of displaying animals within an animal habitat is also provided. The animal habitat is formed by the display case. Some examples of the animal habitat include a switchable LCD film disposed on the back surface of the nonbacklit display screen. By selectively applying power to the switchable LCD film, indicia on the display screen or the animals within the animal habitat may be selectively displayed. Some examples may include sensors for tracking the movements of animals within the animal habitat. Indicia on the nonbacklit display screen may track the movements of these animals. 
     These and other aspects of the display device and method will become more apparent through the following description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a front and side isometric view of a display case. 
         FIG. 1B  is a front and side isometric view of another display case. 
         FIG. 2  is an isometric exploded view of the display case of  FIG. 1 . 
         FIG. 3  is a schematic diagram showing the various components of the display case of  FIG. 1 . 
         FIG. 4  is an isometric front and side view of the display case of  FIG. 1 . 
         FIG. 5  is an isometric front and side view of an alternative example of a display case. 
         FIG. 6  is an isometric front and side view of the display case of  FIG. 5 . 
         FIG. 7  is an isometric front and side view of another alternative example of a display case. 
         FIG. 8  is an isometric front and side view of the display case of  FIG. 7 . 
         FIG. 9  is an isometric front and side view of a further alternative example of a display case. 
         FIG. 10  is an isometric front and side view of the display case of  FIG. 9 . 
         FIG. 11  is an isometric front and side view of yet another alternative example of a display case. 
         FIG. 12  is an isometric front and side view of the display case of  FIG. 11 . 
         FIG. 13  is an isometric front and side view of an alternative example of a display case. 
         FIG. 14  is an isometric front and side view of the display case of  FIG. 13 . 
         FIG. 15  is an isometric front and side view of a further example of a display case. 
         FIG. 16  is an isometric front and side view of another example of a display case. 
         FIG. 17  is an isometric front and side view of the display case of  FIG. 16 . 
         FIG. 18  is an isometric front and side view of the display case of  FIG. 16 . 
         FIG. 19  is a flowchart showing a triangulation algorithm for use with the display case of  FIG. 12 . 
         FIG. 20  is a flowchart showing another triangulation algorithm for use with the display case of  FIG. 12 . 
         FIG. 21  is a flowchart showing the use of the results of a triangulation algorithm to display information corresponding to objects in the display case of  FIG. 12  in an appropriate location with respect to each object. 
         FIG. 22  is a flowchart showing one parallax correction algorithm. 
         FIG. 23  is a flowchart showing another parallax correction algorithm. 
         FIG. 24  is a flowchart showing yet another parallax correction algorithm. 
         FIG. 25  is a flowchart showing the display of animated graphics on a display used in conjunction with an animal habitat. 
     
    
    
     Like reference characters denote like elements throughout the drawings. 
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1A-2 , and example of a display case  10  is illustrated. The display case  10  includes a housing  12  that includes a bottom  14 , a back  16  (which may be flat as shown in  FIG. 1A , or a curved diffusion panel as shown in  FIG. 1B , depending on the desired interior appearance), a left side  18 , a right side  20 , and a top  22 . In some examples, as described in greater detail below, the back  16  may be formed from a standard opaque monitor. A transparent display  24 , which in the illustrated example is a transparent (nonbacklit) liquid crystal display (LCD), forms the front of the display case  10 . Transparent LCD displays are presently available from both Samsung and LG. The interior of the display case  10  may be configured in a wide variety of manners, depending on the products which will be displayed, with numerous alternative configurations described below. In the example illustrated in  FIG. 2 , the interior of the display case  10  includes a floor  26 , a left side  28 , a right side  30 , and a ceiling  32 . In the illustrated example, the ceiling  32  is a light diffusion panel. In the illustrated example, the floor  26  includes an optional turntable  34 , which is described in greater detail below. The interior left side  28  and right side  30  may include various shelf mounting structures, which in the illustrated example includes the apertures  36  defined within the left side  28  and right side  30  interior walls. 
     Various electronic components may be disposed in various locations between the interior housing and the exterior housing, with one illustrative example configuration being provided in  FIG. 2 . A plurality of LED lighting modules  38  are disposed between the ceiling  32  and top  22 . One or more optional cameras or sensors  40 , which may have one of a plurality of functions discussed below, may also be disposed in this location. A central processing unit (CPU)  42 , which in some examples may be a solid state media player, and in other examples may be a programmable microcontroller, is disposed between the bottom  14  and floor  26 . A plurality of lighting control modules  44  are also disposed between the bottom  14  and floor  26 . Any of these components could optionally be placed in a different location within the housing. 
     Referring to  FIG. 3 , a control system  46  for the display case  10  is illustrated. The entire system is controlled by the CPU  42 , which is in communication with the other system components through the bus system  48 . A removable media storage device, such as the illustrated removable media card  50 , or a USB drive, CD, DVD, or any other magnetic or optical storage medium, may be placed in communication with the CPU  42 . The CPU  42  may also include an ethernet/wireless network  52  for receiving information or instructions from a remote location, a video processor  54  for transmitting data to the transparent display screen  24  and an optional rear display screen  56  (described below), and/or an audio processor  58  for transmitting data to one or more optional speakers  60 , and/or receiving data from the optional microphone  62 . 
     The CPU  42  may receive data and/or instructions from a variety of other sources. A standard computer input device  62 , which may be a standard keyboard or mouse, may be utilized to program the CPU, or by a viewer of the display case  10  to select information to be viewed, or control other functions of the display case  10 . As described in greater detail below, the transparent display  24  may optionally be a touchscreen, permitting the user of the display to enter information and/or make selections by touching predetermined locations on the transparent display  24 . In this instance, a touchscreen controller  64  is provided to interpret the input received from the display  24 , and transmit the data to the CPU  42 . The control system  46  may further be provided with a gesture sensor  66 , so that selections may be input through the use of hand gestures performed in front of the gesture sensor  66 . A camera  68  and/or motion sensor  70  may be utilized to detect the presence and/or movements of a viewer, providing this information to the CPU  42  for purposes that will be described below. One example of a suitable cameras and gesture sensor system is the Kinect for Windows sensor available from Microsoft. Another example is disclosed in US 2011/0128386, the entire disclosure of which is hereby incorporated by reference. 
     Radiofrequency identification (RFID) sensors  72  may be provided to provide automatic identification of items placed within the display case  10 . Some examples of the display  10  may utilize multiple RFID sensors  72 , as explained below. In the case of multiple RFID sensors  72 , the signal from each sensor will be read separately to facilitate determining the location of one or more items within the display  10  through triangulation, as explained in greater detail below. 
     The CPU  42  provides a variety of control systems for the various components of the display case  10 . A lighting controller  74  is utilized to control the lighting modules  38 , and in some examples will utilize DMX signals to control the lighting modules  38 . A turntable controller  76  is utilized to start, stop, and select to the direction of rotation of the turntable  34 . A switchable film controller  78  is utilized to control an optional switchable LCD film  80  in a manner that is described in greater detail below. Lastly, if the interior of the display  10  is utilized as an aquarium or other animal habitat as described in greater detail below, an aquarium controller  82  may receive information from a thermometer  84  as well as other optional aquarium sensors, and will provide control signals to an optional heater  86 , a feeder  88 , and a filtration system  90 . 
     A basic implementation of the display case  10  is illustrated in  FIG. 4 . A plurality of children&#39;s toys  92 ,  94 ,  96  have been placed in the display case  10 . Information  98  about the toys  92 ,  94 ,  96  is displayed on the display screen  24 . When the lighting modules  38  are lit, the toys  92 ,  94 ,  96  are visible through the display screen  24 . A consumer viewing the display  10  will therefore be able to view the products  92 ,  94 ,  96  as well as the information  98  by viewing the screen  24 . 
     One alternative example of a display case  100  is illustrated in  FIGS. 5-6 . The display case  100  includes two LCD displays, one of which being the front transparent LCD display  102 , and the second being a standard opaque monitor  104  forming the back panel of the display. Advertising and/or informational displays may be coordinated between the transparent display  102  and the opaque display  104 . Animated type, motion graphics, slideshows, and video clips may be choreographed to interplay with the product and the display screens  102 ,  104 . As one example, text callouts and animated elements could appear to jump back and forth between the screens  102 ,  104 . Alternatively, the opaque monitor  104  can be utilized to provide localized lighting for the transparent display  102 . In the absence of backlighting, the transparent display  102  will appear to be black. As shown in  FIG. 6 , a highlight elements on the display  104  can be utilized in conjunction with the lighting modules  38  to provide a localized viewing aperture  106  by effectively backlighting only the portion of the display  102  corresponding to the aperture  106 . The remaining, unbacklit sections of the transparent display  102  will appear black. 
     Further examples of a display case  108 ,  109  are illustrated in  FIGS. 7-8 . The display cases  108 ,  109  include a turntable  110  for rotating an item within the display case  108 ,  109 . The display cases  108 ,  109  include a transparent display  112 ,  113 . The back panel  114  of the display cases  108 ,  109  may optionally be a standard opaque monitor as described above. Information displayed on the transparent display  112 ,  113  and optional back panel monitor  114  may be coordinated with the rotation of the turntable  110 . For example, information about features of the items that are currently visible to a viewer may be displayed on a transparent display  112 , with the information changing as the turntable  110  rotates to show different features of the displayed item. As another alternative, features that are located in rearward portions of the displayed item may be displayed on an opaque monitor as described above forming the back panel  114 , switching to the transparent display  112 ,  113  as the turntable  110  rotates to bring these features of the item towards the front of the display cases  108 ,  109 . 
     In some examples of the display case  108 , rotation of the turntable  110  may be controlled by the viewer utilizing a variety of control mechanisms such as a keyboard mouse, touch pad, etc. One example of such a control mechanism is included within the display case  108 . The transparent display  112  is a touchscreen display that is illustrated with indicia  116  displayed thereon. A viewer may cause the turntable  110  to rotate in a desired direction by touching the arrow corresponding to that direction. In the example of display case  109 , an integrated camera and gesture sensor  118  are utilized to track the hand motions of a viewer. Suitable gesture sensing devices include the Kinect for Windows sensor as well as the device disclosed in US 2011/0128386. The viewer may cause the turntable  110  to rotate in a desired direction, or to pause, by moving their hand in the desired direction of rotation. The camera and gesture sensor  118  could be utilized for other purposes as well. For example, vertical hand movements could be utilized to brighten or dim the lighting modules  38 , to scroll information displayed on the transparent display  113 , to select options displayed on the transparent display  113 , and/or to navigate various content layers shown on the transparent display  113 . 
     Referring to  FIGS. 9-11 , another example of a display case  120  is illustrated. The display case  120  includes a transparent LCD screen  122 , as well as a depth sensing camera  124  By determining the distance between the camera and objects seen by the camera, the camera can determine the position of a viewer&#39;s face, which would obviously be relatively close relative to other objects in the environment.  FIG. 9  illustrates an example of a video camera  126  within the display case  120 , with a feature of the video camera shown on the transparent display screen  122 . When a customer is directly in front of the display case  120 , the relative appearance of the camera  126  and indicia  128  displayed on the screen  122  is shown in  FIG. 9 .  FIGS. 10 and 11  illustrate the parallax resulting if the customer  130  is located closer to the right side ( FIG. 10 ) or left side ( FIG. 11 ) of the display case  120 . In the absence of any adjustments to the indicia  128  displayed on the transparent screen  122 , this parallax will cause the presentation of the indicia  128  with respect to the camera  126  to be skewed. By utilizing the depth sensing camera  124  to detect the position of the customer  130 , the indicia  128  may be moved to a different location on the display screen  122  as appropriate so that regardless of the position of the customer  130 , the image viewed by the customer  130  will appear as it does in  FIG. 9 . 
     The CPU of the display case  120  may be programmed with a threshold proximity value so that, if a single viewer is viewing the display case  120  while others travel past the display case  120 , those travelling in the background are ignored unless they come within a predetermined distance of the display screen  122 , and also slow their walking to a predetermined speed and/or remain within the threshold distance for a predetermined period of time, as would occur if they began to view the display screen  122 . This allows the parallax correction algorithm to focus only on a viewer or viewers who are actually engaged in viewing the display screen  122 . 
     If multiple viewers are present, then the system may take this into account in a few different ways. As one option, the system could focus on correcting parallax for a primary viewer, ignoring the other viewers. Referring to  FIG. 22 , the system receives information from a camera  124  at step  206 . Next, it is determined whether a viewer is within the threshold distance, and whether the viewer has slowed or stopped to view the display, at step  208 . If no viewer is within the threshold, the system continues to monitor the threshold area at step  206  until a viewer enters the threshold area. When a viewer is present, the first viewer to enter the threshold area is designated as the primary viewer at step  210 . If another viewer enters the threshold distance as determined at step  212 , and if that viewer slows their rate of travel sufficiently to indicate that they may be viewing the display as determined at step  214 , then that viewer is placed in a queue at step  216  to become the next primary viewer if the current primary viewer leaves. 
     Once the primary viewer has been identified, the viewer&#39;s position is determined with respect to objects within the display at step  218 . For this purpose, it may be assumed in some cases that the object is in a predetermined location within the display case. Alternatively, if RFID sensors or other sensors (described below) are utilized, the location of the object within the display case as determined by these sensors is utilized. With the location of the primary viewer and the objects in the display case known, appropriate geometric calculations can be made to move information on the display screen  122  to a different location on the display screen  122  to correct for parallax at step  220 . Information from the camera  124  is again received at step  222 . If the primary viewer is still present as determined at step  224 , the system returns to step  218  and continues to track the movements of the primary viewer. Otherwise, if the primary viewer has left, the system next checks at step  226  to determine whether there is another viewer within the queue. If so, then the first viewer in the queue is designated as the primary viewer at step  228 , and the system determines the new primary viewer position at step  218 . Otherwise, the system returns to step  206  to begin scanning for other viewers to enter the threshold criteria. 
     As another option, the system could recognize that reducing parallax for one viewer will create worse parallax for another viewer, and thereby avoid adjusting for parallax unless the number of viewers inside the threshold distance is limited to one. Referring to  FIG. 23 , the system first receives information from camera  124  at step  230 . If exactly one viewer meets the threshold criteria for proximity and speed of travel at step  232 , then the viewer&#39;s position is determined relative to objects within the display at step  234 . The appropriate geometric calculations are performed, and information on the display screen  122  is moved to the appropriate location to minimize parallax at step  236 . The system then continues to receive information from the camera  124  at step  230 . If there are no viewers present, or if there is more than one viewer present, information will be displayed without parallax correction at step  238 . 
     Alternatively, if all, or a majority, of the viewers are located on one side of the screen, the system could make adjustments based on an average viewer location. Referring to  FIG. 24 , information is received from the camera  124  at step  240 . If any viewers meet the threshold distance and speed of travel criteria at step  242 , then the position of all viewers within the threshold criteria is determined at step  244 . Next, the average viewer positional deviation from directly in front of the object within the display case is determined at step  246 . The appropriate geometric calculations are performed based on this information, and the image on the display screen moved appropriately, at step  248 . The system then continues to receive information from the camera  124  at step  240 , repeating the cycle whenever viewers are present, and returning to step  240  to continue checking for the presence of viewers any time no viewers meet the threshold criteria. 
     Referring to  FIG. 12 , the display case  132  is illustrated. The display case  132  includes one or more RFID sensors, with sensors  135 ,  137 ,  139 , and  141  being shown in each corner of the display case  132 . When a product equipped with an RFID tag is placed within the display case  132 , the RFID sensor can read the RFID tag to determine the products which has been placed in the display case  132 . If multiple RFID sensors are utilized, then the location of multiple products within the display case  132  can be determined by comparing the relative signal strength of each RFID tag with respect to each RFID sensor (triangulation). Information about each of the products  134 ,  136 ,  138  can therefore be displayed in the appropriate location on the display screen  140 . 
     Referring to  FIG. 19 , one alternative triangulation algorithm is illustrated. The process begins by receiving a signal from RFID sensors  135 ,  137 ,  139 ,  141  at steps  158 ,  160 ,  162 , and  164 , respectively. Next, the strength of the signals received by the RFID sensors  135 ,  137  is compared at step  166 . Similarly, the signal strength of the signals received by the RFID sensors  139 ,  141  is compared at step  168 . The relative signal strengths between the values read at each sensor is utilized to determine the left to right placement of the object at step  170 . Similarly, the signal strength received by sensors  135 ,  139  is compared at step  172 , and the signal strength received by the RFID sensors  137 ,  141  is compared at step  174 . These values are used to determine the front to back placement of the object at step  176 . With one object within the display case  132  having been located, the process may be repeated as often as necessary for other objects within the display case  132  at step  178 . 
     Referring to  FIG. 20 , an alternative triangulation method is illustrated. The method of  FIG. 20  may be utilized when only two RFID sensors are present, with the RFID sensors typically being located at opposite ends of the display case  132 . If we assume that sensors  139 ,  141  are the only two sensors present, then the signal from sensor  139  is received at step  180 . The signal from sensor  141  is received at step  182 . The strength of the signal received by the sensor  139  is measured, and utilized to determine the distance between the object and the RFID sensor  139  at step  184 . Similarly, the strength of the signal received at the RFID sensor  141  is measured, and utilized to determine the distance between the object and the sensor  141  at step  186 . Obviously, a known distance from either sensor will place the objects somewhere within a circle of that radius around the sensor. This radius is calculated for sensor  139  at step  188 , and for sensor  141  at step  190 . Since it is known that the object is within the display case  132 , the location within the display case  132  where the two circles intersect is determined at step  192 , at which point the location of the object is known. The process can be repeated for additional objects within the display case  132  at step  194 . 
     Once the location of all objects within the display case  132  is known, this information can be utilized to display information corresponding to each object on the display screen  140 . Referring to  FIG. 21 , information about the location of each object within the display case  132  is received at step  196 . The corresponding location on the display screen is determined at step  198 . If parallax adjustment as described above is being utilized (determined at step  200 ), then the parallax adjustment algorithm can be run at step  202 . Regardless of whether parallax adjustment is used, information is displayed at the appropriate position on the display screen  140  at step  204 . 
     Referring to  FIGS. 13-14 , a display case  142  is illustrated. The display case  142  includes a transparent display screen  144  having a switchable LCD film disposed behind the display screen  144 . The LCD film may be applied to the back surface of the display screen  144 , with a glass plate disposed over the LCD film. Alternatively, the switchable LCD film may be disposed between a pair of glass plates which are disposed behind the display screen  144 . Suitable switchable LCD films are available from Glass Apps, LLC. Because the transparent display screen  144  is not backlit, in the absence of the switchable LCD film, it would appear black when there is no light emitted inside the display case  142 . The CPU of the display case  142  is structured to selectively apply power to the switchable LCD film as shown in  FIG. 3 . Referring back to  FIGS. 13-14 , the switchable LCD film appears frosted when there is no power applied to the LCD film. In this state, the LCD film acts as a diffusion element for the LCD lights, permitting information to be displayed on the display screen  144  without revealing the contents of the display case  142 , as shown in  FIG. 13 . When power is applied to the switchable LCD film, the switchable LCD film becomes transparent, revealing the contents of the display case  142  as shown in  FIG. 14 . The power applied to the switchable LCD film can be coordinated with the content displayed on the transparent display screen  144 , correlating the media content with timed revealing and concealing of the contents of the display case  142 . 
     Referring to  FIG. 15 , a display case  146  includes a transparent display screen  148  over which a polarized mirror glass has been applied. The mirror coating in some examples is vapor deposited onto glass, which is then placed in front of the display screen  148 . The mirror glass is carefully polarized to allow a bright image to transfer through the mirror. When the interior of the display case  146  is not lit, the display screen  148  appears as a mirror. When the display case  146  is fully illuminated, the interior of the display case  146  is visible. If the display screen  148  is utilized to display a black and white image, the black portions of the image are opaque, and the white portions appear transparent (assuming that the interior of the display case  146  is illuminated). With the inclusion of the polarized mirror glass, the black portions  150  of the image appear to be mirrored, and are shown in  FIG. 15  reflecting the image of the rose  152 . The white portions  154  of the image appear transparent, displaying a product  156  within the display case  146 . 
     Referring to  FIGS. 16-18 , an animal habitat  158 , for example, the illustrated fish tank, incorporating a transparent display screen  160  is illustrated. As used herein, “animal” may refer to any mammal, fish, bird, insect, etc. that could be kept in an enclosure. Similarly, “animal habitat” may refer to a cage, glass enclosure, etc., that may contain an animal, including an aquarium for containing fish. In the example of a fish tank, the transparent display screen  160  is adjacent to one of the glass panels of the fish tank  158 , allowing viewing of the fish through the transparent display screen  160 , while isolating the transparent display screen  160  from the water in the fish tank  158 . If a different animal habitat is used, for example, a hamster or gerbil enclosure, a glass barrier between the animals and display screen  160  may still be desirable. Some examples of the display screen  160  include a switchable LCD film, as described above, permitting either viewing of the fish within the fish tank  158  through a transparent screen  160 , or the use of the screen  160  as an information display, computer monitor, television, etc. with a view of the fish being totally obscured. Some examples of the display screen  160  may include sensors for monitoring conditions such as temperature within the fish tank  158  or other animal enclosure, and displaying these conditions on the screen as shown by indicia  163 . A heater, feeder, and/or filtration system may be controlled by the CPU of the screen  160 , displaying information about these devices within the indicia  163 . 
     Some examples of the animal habitat  158  include motion sensing cameras or sensors to track the movement of fish or other creatures within the animal habitat  158 . Suitable fish/animal tracking devices include the Kinect for Windows sensor as well as the device disclosed in US 2011/0128386. Graphics on the display screen  160  may be integrated with the motion of the fish or other creatures. For example, headlights  161  may be displayed on the screen  160  in front of fish swimming in a fish tank  158  at night, providing for interesting visual effects. Furthermore, the parallax correction algorithm can be used to correct for parallax, so that a viewer seeing the fish from a different angle will still view the headlight graphics in appropriate locations with respect to the fish. 
     Referring to  FIG. 25 , the initial position of each animal or fish is detected at step  250 . A subsequent position of each animal or fish is next detected at step  252 , and this information is utilized to determine the speed and direction of movement for each animal or fish at step  254 . A screen display corresponding to one or more animals or fish is created at step  256 . Parallax correction as described above may optionally be applied at step  258 . The graphics are then displayed on the display screen  160  at step  260 . The system continues to calculate subsequent positions for each animal at step  252 , repeatedly using the changes in position of each fish or animals determine speed and direction of movement so that the graphics may be displayed on the appropriate location on the display screen  160 . 
     The CPU of the transparent display screen  160  may be used to control any heaters, filtration systems, feeding systems, or other devices that may be utilized in the care of the fish or other animals within the animal habitat  158 . Information such as the temperature, amount of food available, feeding times, condition of a filter, etc. can be displayed on the screen  160  as shown by display  163 . If the screen  160  is a touch screen as described above, then changes to these functions can be made by touching the appropriate indicia on the screen. 
     A variety of modifications to the above-described embodiments will be apparent to those skilled in the art from this disclosure. For example, many of the features of the above-described examples of the display case can be combined with other features of other examples. Thus, the invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The particular embodiments disclosed are meant to be illustrative only and not limiting as to the scope of the invention. The appended claims, rather than to the foregoing specification, should be referenced to indicate the scope of the invention.