Patent Publication Number: US-10317714-B2

Title: Presentation control device, game machine and program

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of International Application No. PCT/JP2015/086326, filed on Dec. 25, 2015, which claims priority based on the Article 8 of Patent Cooperation Treaty from prior Japanese Patent Applications No. 2015-006234, filed on Jan. 15, 2015, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The disclosure relates to a presentation control device, a game machine and a program. 
     BACKGROUND 
     An image presentation device may be equipped with: a transparent liquid crystal panel that provides transmissive display in a transparent display region; and an LCD with the display screen located behind the transparent liquid crystal panel (refer to for example, Patent Document 1). 
     Patent Document 1 Japanese Unexamined Patent Application Publication No. 2014-61335 
     TECHNICAL PROBLEM 
     A transmissive display unit such as a liquid crystal panel may be provided on the front surface of a display device; in this case, the transmissive display unit can only present images using the light exiting from the display device. Therefore, in practical terms presenting a sufficiently bright image via both the transmissive display unit and the display device can be quite challenging. Additionally, there are times when the transmissive display unit cannot express certain colors depending on the color of the image being presented on the display device. For instance, the transmissive display unit is unable to show a blue image superimposed over a region where the display device is presenting a red image. Accordingly, the device cannot provide an image with superior visual effect. 
     SUMMARY 
     In a first embodiment, a presentation control device includes: a first display unit which is a transmissive display unit; a transparent backlight formed of transparent material, provided relative to the first display unit opposite the viewing surface of the first display unit, and configured to emit light toward the first display unit; a light source configured to output object light to the transparent backlight where light from an object provided opposite the light emission plane of the transparent backlight is output toward the transparent backlight and the first display unit; and a display device including a display controller configured to control the first display unit, the transparent backlight, and the light source so that light emitted from the transparent backlight shows an image on the first display unit, and so that the object light can pass through the transparent backlight and the first display unit and be output. The presentation control device may be provided with a presentation controller configured to control the display controller on the basis of a command received to cause the first display unit to show an image with light emitted from the transparent backlight, and to allow output of object light. 
     The presentation controller controls the display controller on the basis of the command received to cause the light emission state of the transparent backlight to switch while the object light is output. 
     The presentation controller may control the display controller on the basis of the command received to cause the first display unit to switch between a state of presenting an image thereon and a state of presenting an image from the object light by causing the transparent backlight to switch between a state where the transparent backlight emits light and a state where the transparent backlight does not emit light while the object light is output. 
     The transparent backlight may be configured to switch the intensity of light emitted by the transparent backlight between a first light intensity and a second light intensity greater than the first light intensity; and the presentation controller controls the display controller on the basis of the command received to cause the image shown on the first display unit and the image from the object light to be presented simultaneously by setting the light emission intensity of the transparent backlight to said first light intensity while the object light is output. 
     The presentation controller may control the display controller on the basis of the command received to cause the light emission state of the transparent backlight to switch while the object light is output. 
     The presentation controller may control the display controller on the basis of the command received to allow the image shown on the first display unit and the image from the object light to be observed substantially at the same time by causing the transparent backlight to switch between a state where the transparent backlight emits light and a state where the transparent backlight does not emit light at a rate greater than a predetermined rate while the object light is output. 
     The presentation controller may control the display controller on the basis of the command received to cause the combination of the light emission state of the transparent backlight and the content shown on the first display unit to vary while the object light is output. 
     The light source may emit light that illuminates the object; and the presentation controller controls the display controller on the basis of the command received to control the light source. 
     The display device may be provided in a game machine, and the object may include an accessory in the game machine. 
     The display device may further include a second display unit configured to output image light based on light from the light source as object light; where the object is the second display unit; and the presentation controller controls the display controller on the basis of the command received to cause an image to be shown on the second display unit. 
     The presentation controller controls the display controller on the basis of the command received to cause the image shown on the second display unit to vary while causing an image to be shown on the first display unit with light emitted from the transparent backlight. 
     The transparent backlight may include a light guide plate formed of transparent material and including a light input surface, a light output surface facing the first display unit, the light guide plate configured to cause light entering from the input surface to propagate therethrough and exit from the output surface; and a light source configured to emit light that enters through the input surface into the light guide plate; wherein the presentation controller controls the display controller on the basis of the command received to control the light emission state of the light source. 
     In a second embodiment, a game machine is provided with the above presentation control device, and the above display device. 
     In a third embodiment a program causes a computer to function as the above presentation control device. 
     Note that the above summary does not list all the features of the present invention. Sub combinations of these sets of features are also within the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic front view of a game machine  10  provided with a display device  100  according to one embodiment; 
         FIGS. 2A and 2B  are schematic views of the configuration of a display component  80  provided in the display device  100 ; 
         FIG. 3  is a block diagram of a controller  30  and display device  100  provided on a playfield  11 ; 
         FIGS. 4A, 4B, and 4C  illustrate an image presented on the display device  100 ; 
         FIGS. 5A and 5B  illustrate the transparent liquid crystal panel  210  and a liquid crystal display  220  both showing an image; 
         FIG. 6  illustrates another example of control when simultaneously presenting an image  410  and an image  420 ; 
         FIG. 7  illustrates an example of the controller  30  and display device  100  controlling presentation; 
         FIG. 8  is a schematic perspective view of a display component  880  and is an example of modifying a display component; 
         FIGS. 9A and 9B  illustrate an image presented by the display component  880 ; 
         FIGS. 10A and 10B  are lateral cross-sectional views illustrating generally a transparent backlight  230 ; 
         FIGS. 11A and 11B  illustrate examples of modifying a reflection surface  1020 ; 
         FIG. 12  is a table expressing a relationship between pattern density and haze, and how an image appears; 
         FIGS. 13A, 13B, and 13C  illustrate example patterns for distributing prisms; 
         FIG. 14  is the lateral cross-sectional view of another modification to the light guide plate  240 ; 
         FIG. 15  is the lateral cross-sectional view of another modification to the light guide plate  240 ; and 
         FIG. 16  is the lateral cross-sectional view of another modification to the light guide plate  240 . 
     
    
    
     DETAILED DESCRIPTION 
     The present invention is described by way of describing an embodiment; however, the below-mentioned embodiment is in no way a limitation on the present invention. All the combinations of features described in the embodiment are not necessarily required for solving the technical problem addressed by the invention. 
       FIG. 1  is a schematic front view of a game machine  10  provided with a display device  100  according to one embodiment. The game machine  10  is a pinball machine. The game machine  10  includes a playfield  11  that is the main game unit; a ball trough  12 ; an input unit  13 ; a display device  100 ; a stationary gadget  15 ; moving gadget  16 ; and at least one prize target  18 ; and rails  17 . 
     The playfield  11  takes up a majority of the game machine  10 , from the top portion to the center. The ball trough  12  and the input unit  13  are provided below the playfield  11 . The display device  100  is provided in substantially the center of the playfield  11 . The display device  100  is installed on the playfield  11  so that the front surface of the liquid crystal panel faces the player. Note that the front is toward where the user of the game machine  10  is located. In some cases the surface opposite the front is referred to as the rear surface. 
     The display device  100 , a stationary gadget  15 , a moving gadget  16 , a prize target  18 , and rails  17  are provided on the playfield  11 . The stationary gadget  15  and the moving gadget  16  are used for presenting the game. The stationary gadget  15  is provided, for example, on the front surface at the lower part of the playfield  11 . The moving gadget  16  is provided between the playfield  11  and the stationary gadget  15 . Additionally, a is also provided on the playfield  11 . Multiple obstacle pins and the like are also provided on the playfield  11  to guide the pinball. 
     The input unit  13  accepts rotary input from the player. The game machine  10  launches the pinball with a certain force in response to the amount of rotation of the input unit  13 . The launched pinball travels on the playfield  11  falling between the multiple obstacle pins. As is later described, the playfield  11  is provided with a controller  30 . The controller  30  pays out a predetermined number of pinballs into the ball trough  12  in accordance with the prize associated with the prize target  18  when it is detected that the pinball entered a prize target  18 . 
     The display device  100  presents the state of play in accordance with control signals from the presentation controller  300 . The display device  100  shows images of various patterns and video graphics and the like in accordance with the state of the game. 
       FIGS. 2A and 2B  are schematic views of the configuration of a display component  80  provided in the display device  100 .  FIG. 2A  is a simplified perspective view of a display component  80 ; and  FIG. 2B  is a simplified lateral view of the display component  80 . 
     The display device  100  is equipped with a transparent liquid crystal panel  210 , a transparent backlight  230 , and a liquid crystal display  220 . The liquid crystal display  220  includes a liquid crystal panel  260  and a backlight  270 . 
     The transparent liquid crystal panel  210  is one example of a transmissive display unit. The transparent liquid crystal panel  210  includes a front surface  211 , which is the surface viewed and a rear surface  212 . The rear surface  212  is opposite the front surface  211 . The transparent backlight  230  is provided opposite the front surface  211  of the transparent liquid crystal panel  210 . The transparent backlight  230  emits light toward the transparent liquid crystal panel  210 . The transparent backlight  230  is a transparent surface light source. 
     The transparent backlight  230  includes a light guide plate  240 , a light source  250   a , a light source  250   b , a light source  250   c , and a light source  250   d . The light guide plate  240  includes a light input surface  243 , a light output surface  241 , a diffusion surface  242 , and an end surface  244 . The diffusion surface  242  is opposite the output surface  241 . The input surface  243  and the end surface  244  are one of the side surfaces of the light guide plate  240 . The input surface  243  is orthogonal to the diffusion surface  242  and the output surface  241 . The end surface  244  is opposite the input surface  243 . The light guide plate  240  is produced from a transparent material. For instance, the light guide plate  240  may be molded from a resin that is transparent to visible light, such as poly methyl methacrylate (PMMA), a polycarbonate, or a cycloolefin polymer. The light guide plate  240  is provided so that the output surface  241  faces the transparent liquid crystal panel  210 . The output surface  241  is provided as the light emission surface of the transparent backlight  230 . Thus, the transparent backlight  230  is provided so that the output surface  241  of the light guide plate  240  faces the rear surface  212  of the transparent liquid crystal panel  210 . 
     The suffixes for the light source  250   a , light source  250   b , light source  250   c , and light source  250   d  will be omitted and the same collectively referred to as the light source  250 . The light source  250  emits visible light. For example, the light source  250  substantially emits white light. The light source  250  is provided facing the input surface  243  of the light guide plate  240 . As one example, the light source  250  may be a light emitting element such as an LED. The light source  250  is arranged so that the direction of maximum light emission therefrom is orthogonal to the input surface  243 . To improve the light use efficiency, the light source  250  is preferably a light emitting element that possesses directivity. A collimating lens may also be arranged between the input surface  243  and the light source  250  to improve the directivity of light emitted from the light source  250 . Projections may also be formed on the input surface  243  projecting toward the light source  250 ; the projections function as the collimating lens that improves the directivity of light emitted from the light source  250 . 
     Light from the light source  250  enters the light guide plate  240  from the input surface  243 . The light traveling through the light guide plate  240  is totally reflected by the diffusion surface  242  and thereafter exits from the output surface  241 ; the light then enters the transparent liquid crystal panel  210  from the rear surface  212  thereof. 
     Thus, when the light source  250  is lit, the light guide plate  240  transmits and scatters the light from the light source  250  therethrough; the light is then output toward the transparent liquid crystal panel  210  and consequently illuminates the transparent liquid crystal panel  210 . An image in accordance with the pattern of the amount of light transmitted in the transparent liquid crystal panel  210  is shown on the front surface  211  of the transparent liquid crystal panel  210  via the light from the light guide plate  240 . 
     The liquid crystal panel  260  in the liquid crystal display  220  does not require substantially transparent material; beyond that, the liquid crystal panel  260  has the same configuration as the transparent liquid crystal panel  210 . The liquid crystal panel  260  of the liquid crystal display  220  includes a front surface  261  corresponding to the front surface  211 , and a rear surface  262  corresponding to the rear surface  212 . The rear surface  262  is opposite the front surface  261 . Note that the liquid crystal panel  260  is one example of a component provided opposite the transparent backlight  230 , and more specifically, opposite to the light emission plane of the transparent backlight  230 . The backlight  270  is also one example of a light source; and specifically, the backlight  270  is a light source that outputs light from an object, i.e., image light which is one example of object light. 
     More specifically, the backlight  270  emits light that illuminates the liquid crystal panel  260  from the rear surface  262  of the liquid crystal panel  260 . That is, the backlight  270  allows image light that passes through the liquid crystal panel  260  and then toward the transparent backlight  230  and the transparent liquid crystal panel  210  to be output from the liquid crystal panel  260 . 
     More specifically, the backlight  270  of the liquid crystal display  220  includes a light output surface  271 , and a rear surface  272 . The rear surface  272  is opposite the output surface  271 . The backlight  270  may employ a light guide plate. The backlight  270  may be an edge-type backlight similar to the transparent backlight  230 . The transparent backlight  230  may also be configured so that a light source such as a cold cathode ray tube or LED are directly beneath the backlight. The backlight  270  may be provided so that the output surface  271  thereof faces the rear surface  262  of the liquid crystal panel  260 . 
     The liquid crystal panel  260  is illuminated by light emitted from the backlight  270  when the backlight  270  is illuminated. An image in accordance with the pattern of the amount of light transmitted in the liquid crystal panel  260  is shown on the front surface  261  of the liquid crystal panel  260  by way of the light from the backlight  270 . Thus, the liquid crystal panel  260  outputs image light on the basis of light from the backlight  270 . 
     Here, when the backlight  270  is lit, the light from the backlight  270  enters the light guide plate  240  from the diffusion surface  242  after passing through the liquid crystal panel  260 . The light guide plate  240  is produced from a resin material that is transparent to visible light as above described. Therefore, the light from the backlight  270  that enters the light guide plate  240  from the diffusion surface  242  passes through the light guide plate  240  as is, exits from the output surface  241  toward the transparent liquid crystal panel  210 , passes through the transparent liquid crystal panel  210  and exits from the front surface  211 . Consequently, a user able to see the front surface  211  of the transparent liquid crystal panel  210  is able to view an image presented on the liquid crystal panel  260  from the front surface  211  of the transparent liquid crystal panel  210 . 
       FIG. 3  is a block diagram of a controller  30  and display device  100  provided on a playfield  11 ; the controller  30  includes a main controller  310  and a presentation controller  300 . The display device  100  is provided with a display controller  330 ; the transparent liquid crystal panel  210 ; a light source controller  340 ; the transparent backlight  230  which includes the light source  250  and the light guide plate  240 ; and the liquid crystal display  220  which includes the liquid crystal panel  260  and the backlight  270 . 
     The presentation controller  300  controls the display device  100  in accordance with commands from the main controller  310 . For instance, the main controller  310  may output information representing the state of the game to the presentation controller  300 , directing the presentation controller  300  to provide a visual according to the state of the game. The presentation controller  300  controls presentation on the display device  100  by controlling the display controller  330  on the basis of information from the main controller  310 . Note that the state of the game may be, for instance, “Prize Winner” or “Grand Prize!”, or the like. The presentation controller  300  controls the display controller  330  in accordance with the state of the game. 
     The display controller  330  controls the transparent liquid crystal panel  210 , the transparent backlight  230 , and the light source so that an image is shown on the transparent liquid crystal panel  210  using light emitted from the transparent backlight  230 ; the display controller  330  also controls the transparent liquid crystal panel  210 , the transparent backlight  230 , and the light source so that image light from the liquid crystal display  220  may pass through the transparent backlight  230  and the transparent liquid crystal panel  210  and be output. Hereby, the display device  100  may provide an image shown by the transparent liquid crystal panel  210  and an image shown by the liquid crystal display  220  simultaneously. 
     The display controller  330  also changes how light is emitted from the transparent backlight  230  while causing the liquid crystal display  220  to output image light. For example, the display controller  330  switches the transparent backlight  230  between emitting and not emitting light while causing the liquid crystal display  220  to output image light. Hereby, the display controller  330  is able to switch between having the transparent liquid crystal panel  210  present an image and having the image displayed via image light from the liquid crystal display  220 . 
     The transparent backlight  230  may also switch between a first light intensity and a second light intensity greater than the first light intensity that can be emitted therefrom. As an example, the light source controller  340  may change the duty cycle of the current supplied to the light source  250  in accordance with control by the display controller  330  to change the intensity of the light emitted from the transparent backlight  230 . The light source controller  340  may switch among a four-stage duty cycle such as, 0%, 30%, 60% and 100%. The light source controller  340  may continuously and consecutively switch the duty cycle. At this point the display controller  330  causes the liquid crystal display  220  to output image light and selects a first light intensity for the transparent backlight  230 , whereby the image shown on the transparent liquid crystal panel  210  and the image created from image light from the liquid crystal display  220  may be presented simultaneously. The second light intensity may be the maximum intensity of the backlight. The second light intensity may be the intensity at a duty cycle of 100%. In contrast, for instance, the second light intensity may be greater than zero but less than the maximum intensity. For example, the second light intensity may correspond to a duty cycle of 30% or 60% or the like. 
     The display controller  330  also changes the intensity of light emitted from the transparent backlight  230  while causing the liquid crystal display  220  to output image light. Hereby the display controller  330  may control the transparent liquid crystal panel  210  so that the degree of emphasis on the image presented on the transparent liquid crystal panel  210  changes over time in relation to the image formed due to image light from the liquid crystal display  220 . 
     The display controller  330  may switch between causing the transparent backlight  230  to emit light and to not emit light at greater than a predetermined rate while allowing the liquid crystal display  220  to output image light. This allows an image shown on the transparent liquid crystal panel  210  and an image from image light from the liquid crystal display  220  to be shown substantially at the same time. The aforementioned predetermined rate for switching the transparent backlight  230  may be, for instance, a video frame rate or the refresh rate of the transparent liquid crystal panel  210  or the liquid crystal display  220 . 
     The display controller  330  may change a combination of the light emission state of the transparent backlight  230  and what is shown on the transparent liquid crystal panel  210  while causing the liquid crystal display  220  to output image light. For example, the display controller  330  may vary a combination of the light emission intensity of the transparent backlight  230  and the image shown on the transparent liquid crystal panel  210  over time. The display controller  330  may further vary the content of what is shown on the liquid crystal display  220 . For example, the display controller  330  may vary the image shown on the liquid crystal panel  260  while causing the transparent liquid crystal panel  210  to display an image using light emitted from the transparent backlight  230 . For example, the display controller  330  may also vary a combination of the light emission intensity of the transparent backlight  230 , the image shown on the transparent liquid crystal panel  210 , and the image shown on the liquid crystal display  220  over time. The display device  100  is thereby capable of providing a variety of highly interesting visuals. 
     Two transparent substrates are provided facing each other to create transparent electrodes and a liquid crystal is provided filling therebetween to produce the transparent liquid crystal panel  210  in the display device  100 . The display controller  330  controls the voltage applied to each portion of the liquid crystal layer by way of the transparent electrodes. The display controller  330  controls the voltage applied to each portion of the liquid crystal layer to vary the orientation of each portion of the liquid crystal layer; with this the transparent liquid crystal panel  210  is able to change the state of different stages of light passing through each portion of the liquid crystal layer. Turning on the transparent backlight  230  at this point allows the transparent liquid crystal panel  210  to show an image in accordance with the pattern that appears due to the difference in the amount of light passing through the transparent liquid crystal panel  210  and exiting from the front surface  211 . In contrast, the display controller  330  controls the voltage applied to each portion of the liquid crystal layer to ensure that there is substantially no variation in the state of light passing through each portion of the liquid crystal layer. The display controller  330  also ensures that light substantially passes through the transparent liquid crystal panel  210  and is, for the most part, uniformly output from the front surface  211 . That is, the display controller  330  essentially renders the transparent liquid crystal panel  210  transparent. Note that the transparent liquid crystal panel  210  is referred to as being in the ON state when it presents an image, and in the OFF state when it is substantially transparent. The transparent backlight  230  is referred to as being in the ON state when it is illuminated, and is in the OFF state when not illuminated. 
     The display controller  330  controls how an image is presented on the liquid crystal display  220 . That is, the display controller  330  controls the backlight  270  and the liquid crystal panel  260  similar to controlling the transparent liquid crystal panel  210  and the transparent backlight  230  to render the display unit  220  able to show an image. More specifically the display controller  330  turns on the backlight  270  and renders the liquid crystal panel  260  able to shown an image. Additionally, the display controller  330  may prevent the liquid crystal display  220  from showing an image by rendering the liquid crystal panel  260  substantially non-transparent to light. The display controller  330  may turn off the backlight  270  so that an image is not presented on the liquid crystal display  220 . The liquid crystal display  220  is referred to as in the ON state when it is showing an image, and is referred to as being in the off state when it is not showing an image. 
     Simple examples of display by the display device  100  are described with reference to  FIG. 4A  through  FIG. 6 .  FIGS. 4A, 4B, and 4C  are schematics of an image presented on the display device  100 .  FIG. 4A  depicts the transparent liquid crystal panel  210  showing an image while the liquid crystal display  220  does not show an image. More specifically, the transparent liquid crystal panel  210  is in the ON state, the transparent backlight  230  is in the ON state, and the liquid crystal display  220  is in the OFF state. In this state the display device  100  can present the user with the image  410  shown on the transparent liquid crystal panel  210 . 
       FIG. 4B  depicts the liquid crystal display  220  showing an image while the transparent liquid crystal panel  210  does not show an image. More specifically, the transparent liquid crystal panel  210  is in the OFF state, the transparent backlight  230  is in the OFF state, and the liquid crystal display  220  is in the ON state. In this state the display device  100  can present the user with the image  420  shown on the liquid crystal display  220 . 
       FIG. 4C  depicts the transparent liquid crystal panel  210  and the liquid crystal display  220  both showing an image. More specifically, the transparent liquid crystal panel  210  is in the ON state, the transparent backlight  230  is in the ON state, and the liquid crystal display  220  is in the ON state. Hereby, the display device  100  may present the user with the image  410  shown on the transparent liquid crystal panel  210  and the image  420  shown on the liquid crystal display  220  simultaneously. 
     The display controller  330  may switch the display device  100  among any of the states in  FIG. 4A ,  FIG. 4B , and  FIG. 4C  as is desired. For example, the display controller  330  may switch the display status of the display device  100  between presenting the state in  FIG. 4A  and presenting the state in  FIG. 4B . The display controller  330  may also switch the display status of the display device  100  between presenting the state in  FIG. 4A  and presenting the state in  FIG. 4C . The display controller  330  may also switch the display status of the display device  100  between presenting the state in  FIG. 4A  and presenting the state in  FIG. 4C . The display controller  330  may also switch the display status of the display device  100  from presenting the states in  FIG. 4A ,  FIG. 4B , and  FIG. 4C  in that order. Note that the order used to change the display state is not particularly limited to the order described here. 
       FIGS. 5A and 5B  illustrate the transparent liquid crystal panel  210  showing an image together with the liquid crystal display  220 : in  FIG. 5A  the transparent liquid crystal panel  210  shows a low-luminance image; in  FIG. 5B  the transparent liquid crystal panel  210  shows a high-luminance image. In  FIG. 5A  and  FIG. 5B , the transparent liquid crystal panel  210  is in the ON state, the transparent backlight  230  is in the ON state, and the liquid crystal display  220  is in the ON state. The light emission intensity of the transparent backlight  230  in  FIG. 5B  is greater than the light emission intensity of the transparent backlight  230  in  FIG. 5A . 
     In the case of  FIG. 5A , the display controller  330  controls the light source controller  340  to set the light emission intensity of the transparent backlight  230  to less than a predetermined intensity, so that the image  420  is a higher luminance than the image  410 . Hereby, the display device  100  may emphasize the image  420  shown on the liquid crystal display  220  over the image  410  shown by the transparent liquid crystal panel  210  when presenting the same to the user. Taking into account the luminance of the image displayed on the liquid crystal display  220 , the display controller  330  may control the light emission intensity of the transparent backlight  230  so that the luminance of the image  420  is greater than the luminance of the image  410 . 
     In the case of  FIG. 5B , the display controller  330  controls the light source controller  340  to set the light emission intensity of the transparent backlight  230  to greater than a predetermined intensity, so that the image  420  is a lower luminance than the image  410 . Hereby, the display device  100  may emphasize the image  410  shown on the transparent liquid crystal panel  210  over the image  420  shown on the liquid crystal display  220  when presenting the same to the user. Taking into account the luminance of the image displayed on the liquid crystal display  220 , the display controller  330  may control the light emission intensity of the transparent backlight  230  so that the luminance of the image  420  is less than the luminance of the image  410 . 
       FIG. 6  illustrates another example of control when simultaneously presenting the image  410  and the image  420 . The display controller  330  controls the light source controller  340  to switch the transparent backlight  230  very rapidly between being turned on or turned off. The rate for switching the backlight on and off may be greater than a video frame rate. The switching rate may be greater than the refresh rate of the transparent liquid crystal panel  210  or the liquid crystal display  220 . To a person, the image  410  and the image  420  may appear to be shown simultaneously by very rapidly switching the transparent backlight  230  on and off. 
       FIG. 7  illustrates an example of the controller  30  and display device  100  controlling presentation. The main controller  310  provides the presentation controller  300  with a state signal representing the state of the game in the game machine  10 . The presentation controller  300  determines what is to be presented depending on the state of the game. 
     Memory accessible by the presentation controller  300  stores correspondence information that maps the game state to a presentation code. The memory accessible by the presentation controller  300  also stores correspondence information that maps the presentation code to presentation content from the display device  100 . As illustrated in  FIG. 7 , presentation content includes: the transparent liquid crystal panel  210  in the ON or OFF state or the transparent liquid crystal panel  210  showing an image; the duty cycle of the transparent backlight  230 ; and the liquid crystal display  220  in the ON or OF state or the liquid crystal display  220  showing an image. 
     The presentation controller  300  specifies a presentation code that is stored in association with a game state represented by the state signal obtained from the main controller  310 . The presentation controller  300  controls the display controller  330  on the basis of the presentation content stored in association with the presentation code specified. 
     When the presentation code is “1”, the presentation controller  300  instructs the display controller  330  to place the transparent liquid crystal panel  210  in the OFF state, and place the transparent backlight  230  in the OFF state (i.e., to set the duty cycle to 0%) so that the graphic  721  of a person is shown on the liquid crystal display  220 . Hereby the display device  100  presents an image  701  of the graphic  721 . 
     When the presentation code is “2”, the presentation controller  300  instructs the display controller  330  to allow the transparent liquid crystal panel  210  to show the graphic  712 , and set the duty cycle of the transparent backlight  230  to 30% so that the graphic  722  of a person is shown on the liquid crystal display  220 . Hereby the display device  100  presents image  702 , which is a low-luminance version of the graphic  712  superimposed on the graphic  722 . 
     When the presentation code is “3”, the presentation controller  300  instructs the display controller  330  to allow the transparent liquid crystal panel  210  to show the graphic  713 , and set the duty cycle of the transparent backlight  230  to 60% so that the graphic  723  of a person is shown on the liquid crystal display  220 . Hereby the display device  100  presents image  703 , which is a mid-luminance version of the graphic  713  superimposed on the graphic  723 . 
     When the presentation code is “4”, the presentation controller  300  instructs the display controller  330  to allow the transparent liquid crystal panel  210  to show the graphic  714 , and set the duty cycle of the transparent backlight  230  to 30% so that the graphic  724  of a person is shown on the liquid crystal display  220 . Hereby the display device  100  presents image  704 , which is a low-luminance version of the graphic  714  superimposed on the graphic  724 . 
     When the presentation code is “5”, the presentation controller  300  instructs the display controller  330  to allow the transparent liquid crystal panel  210  to show the graphic  715 , and set the duty cycle of the transparent backlight  230  to 100% so that the graphic  725  of a person is shown on the liquid crystal display  220 . Hereby the display device  100  presents image  705 , which is a maximum-luminance version of the graphic  715  superimposed on the graphic  725 . 
     The display device  100  may thus optically superimpose and present the pattern shown on the transparent liquid crystal panel  210  onto the pattern shown by the liquid crystal display  220 ; the display device  100  is thus also capable of changing the degree of emphasis on the superimposing pattern displayed by the transparent liquid crystal panel  210  over time. The display device  100  is thereby able to provide highly interesting visuals. 
       FIG. 8  is a schematic perspective view of a display component  880  and is an example of modifying a display component included in the display device  100 . The display component  880  includes an illuminated gadget  800 , in addition to the transparent liquid crystal panel  210 , the transparent backlight  230 , and the liquid crystal display  220  that can be found in the display component  80 . 
     The illuminated gadget  800  is one example of an accessory. The illuminated gadget  800  is a moving gadget. The illuminated gadget  800  moves between appearing inserted between the transparent backlight  230  and the liquid crystal display  220  and appearing withdrawn from between the transparent backlight  230  and the liquid crystal display  220 . The illuminated gadget  800  includes a gadget unit  810  and one or more light emitting bodies  820 . The light emitting body  820  may be an LED or the like. The display controller  330  controls the illuminated gadget  800  to appear inserted or withdrawn, and controls the emission state of the light emitting bodies  820  on the basis of information received from the presentation controller  300 . 
       FIGS. 9A and 9B  illustrate an image presented by the display component  880 ;  FIG. 9A  depicts the liquid crystal display  220  showing an image while the transparent liquid crystal panel  210  does not show an image with the illuminated gadget  800  active. More specifically, the transparent liquid crystal panel  210  is in the OFF state, the transparent backlight  230  is in the OFF state, the liquid crystal display  220  is in the ON state, and the illuminated gadget  800  appears inserted while the light emitting bodies  820  output light. In this state the display device  100  can present the user with the image  420  shown on the liquid crystal display  220 , and the illuminated gadget  800 , which is emitting light, at the same time. 
       FIG. 9B  depicts the transparent liquid crystal panel  210  showing an image, the liquid crystal display  220  showing an image  900 , and the illuminated gadget  800  active. More specifically, the transparent liquid crystal panel  210  is in the ON state, the transparent backlight  230  is in the ON state, the liquid crystal display  220  is in the ON state, and the illuminated gadget  800  appears inserted while the light emitting bodies  820  output light. Hereby, the display device  100  may present the user with the image  900  shown on the transparent liquid crystal panel  210 , the image  420  shown on the liquid crystal display  220 , and the illuminated gadget  800  which is emitting light, at the same time. 
     The display controller  330  may switch the display device  100  between the states in  FIG. 9A  and  FIG. 9B  as is desired. Note that the example depicted in  FIG. 9A, 9B  are only combinations of the liquid crystal display  220  in the ON state and the illuminated gadget  800  being active. The display controller  330  may add a combination where the liquid crystal display  220  is in the OFF state, and switch to that combination. The display controller  330  may add a combination where the illuminated gadget  800  is in the OFF state, and switch to that combination. 
       FIGS. 10A and 10B  are lateral cross-sectional views illustrating generally a transparent backlight  230 . The lateral cross-sectional view is of the light guide plate  240  from the cross section vertical to the output surface  241  along the propagation direction of light entering the input surface  243  orthogonally from the light source  250 . 
     The diffusion surface  242  includes a plurality of prisms  1010 . These prisms  1010  reflect the light entering from the input surface  243  causing the light to be substantially uniformly output from the entire output surface  241 ; the prisms  1010  also ensure the light enters substantially orthogonal to the transparent liquid crystal panel  210 . 
     The plurality of prisms  1010  is formed so that the prisms are lined up at a predetermined pitch along the propagation direction of incident light entering from the input surface  243 . The prisms  1010  are roughly triangular grooves formed in the diffusion surface  242 ; more specifically the triangular grooves extend in a direction substantially orthogonal to the propagation direction of incident light from the input surface  243 . The prisms  1010  include a reflection surface  1020  that forms a predetermined angle with the diffusion surface  242 . This predetermined angle is set in accordance with the propagation direction of the incident light and the direction light is to exit the light guide plate  240 . 
     In the embodiment, incident light propagates roughly parallel to the diffusion surface  242 , and the light guide plate  240  causes light to exit, on the whole, vertically to the output surface  241 . Therefore, the reflection surfaces  1020  may be created to form an angle of 37° to 45° with the diffusion surface  242 . Preferably the angle α (unit: degrees) of the reflection surfaces  1020 , and in particular the angle α between a reflection surface  1020  and the diffusion surface  242  is established to satisfy the following criteria:
 
α&lt;90−tan −1 (sqrt( n   2 −1))  (1)
 
     Here n is the refractive index of the light guide plate  240 . Furthermore, a light emitting element in the light source  250  is preferably selected so that the half angle β (unit: degrees) of light emitted from the light source  250  satisfies the following criteria:
 
β&lt;109.74 n− 155.06  (2)
 
     For instance, when the light guide plate  240  is produced from a PMMA resin (where the refractive index n=1.49), α is less than 42.17° and β is less than 8.5°. In addition, when the light guide plate  240  is produced from a polycarbonate (where the refractive index n=1.59), α is less than 38.97° and β is less than 19.4°. 
     Because in this case the light is incident on the reflection surfaces  1020  at greater than the critical angle, the incident light is totally reflected by the reflection surfaces  1020  as illustrated by the arrow  1001 . Therefore, the light guide plate  240  is able to inhibit incident light from the light source  250  from exiting via the diffusion surface  242 , and is able to control the amount of light not used for illuminating the transparent liquid crystal panel  210 . 
     Preferably, greater than a certain viewing angle is guaranteed so that a user may see an image shown on the transparent liquid crystal panel  210  even when viewing the display device  100  from a diagonal. In order to guarantee a viewing angle of 15° or greater, the angle α between the reflection surface  1020  and the diffusion surface  242  and the half angle β of the light source  250  preferably satisfies the following conditions:
 
α&lt;1.4924 n+ 40.274  (3)
 
β&lt;−0.0327 n+ 7.5127  (4)
 
     For instance, when the light guide plate  240  is produced from a PMMA resin (where the refractive index n=1.49), α is less than 42.5° and β is less than 7.46°. In addition, when the light guide plate  240  is produced from a polycarbonate (where the refractive index n=1.59), α is less than 42.7° and β is less than 7.46°. 
     Adjacent prisms  1010  may also be formed to have a constant pitch therebetween, so that the intensity of light exiting the output surface  241  does not depend on location. 
     Another input surface may be created at the end surface  244  of the light guide plate  240  in addition to the input surface  243 . That is, the light guide plate  240  may include two opposing input surfaces with a plurality of prisms  1010  arranged therebetween. The light source  250  may also include a light emitting element that emits light that enters the light guide plate  240  from the input surface  243 ; and a light emitting element that emits light that enters the light guide plate  240  from the end surface  244 . In this case, reflection surfaces are formed on both surfaces of each of the prisms  1010 , i.e., on the prism surface toward the input surface  243  and on the prism surface toward the end surface  244 . These reflection surfaces are formed to satisfy Formula (1) or Formula (3) relative to the diffusion surface  242 , so that the incident light is totally reflected toward the output surface  241 . The light emitting element arranged facing the end surface  244  may, for example, possess a half angle that satisfies Formula (2) or Formula (4). 
     In the modification example, the light entering from the input surface  243  and exiting from the output surface  241 , and the light entering from the end surface  244  and exiting from the output surface  241  spread out relative to a normal to the output surface  241  in mutually reverse orientations. Therefore, the viewing angle is larger than the example depicted in  FIG. 3A . 
     In another modification example, the end surface  244  which faces the input surface  243  of the light guide plate  240  may be a mirrored surface to reflect the light propagating inside the light guide plate  240  toward the inside of the light guide plate  240 . This modification achieves an effect identical to those provided by the above-mentioned modification example. 
       FIG. 10B  is a schematic of another example of modifying the light guide plate  240 . In the modification example the input surface  243  is angled at, for instance, 45° relative to the diffusion surface  242 . The light entering the light guide plate  240  from the input surface  243  is incident on the diffusion surface  242  and the output surface  241  at roughly 45°, and is totally reflected whereby the light propagates through the light guide plate  240 . Here, the light traveling through the light guide plate  240  and reaching a prism  1010  strikes the reflection surface  1020  with an incident angle that is less than the critical angle. However, in this case, as illustrated by the arrow  1002 , light exiting from the reflection surface  1020  is refracted towards the diffusion surface  242 ; therefore, the light reenters the light guide plate  240  from a surface of the prism  1010  further away from the light source  250 . Consequently, this prevents a loss in light intensity due to light exiting from the diffusion surface  242  toward the rear surface. 
       FIGS. 11A and 11B  illustrate an example of modifying a reflection surface  1020 ;  FIG. 11A  illustrates schematically an example of modifying a reflection surface  1020 . In this modification example, the reflection surface  1020  is formed from a plurality of flat surfaces  1100   a  and flat surfaces  1100   b ; the angle of inclination of the reflection surface  1020  relative to the diffusion surface  242  increases closer to the output surface  241 . Alternatively, the reflection surface  1020  may be formed by a cylindrical surface that is recessed relative to the input surface  243  and where the center thereof is flat relative to the output surface  241 . This increases the directivity of the light output from the output surface  241 . 
       FIG. 11A  illustrates schematically another example of modifying a reflection surface  1020 . In this modification example, the reflection surface  1020  is formed from a plurality of flat surfaces  1100   c  and flat surfaces  1100   d ; the angle of inclination of the reflection surface  1020  relative to the diffusion surface  242  increases closer the output surface  241  so that the reflection surface  1020  becomes a bump in relation to the input surface  243 . Alternatively, the reflection surface  1020  may be formed by a cylindrical surface that protrudes relative to the input surface  243  and where the center thereof is flat relative to the output surface  241 . In this case, the viewing angle increases because the light entering the light guide plate  240  is reflected by the reflection surface  1020 . 
       FIG. 12  is a table  1200  created via visual inspection to express the relationship between pattern density and haze, and how an image appears. 
     Pattern density is the ratio of the area of the region on which the prisms  1010  are formed to the surface area taken up by the diffusion surface  242 . The pattern density is preferably less than an upper limit where a user may perceive an image due to light from the rear of the light guide plate  240  via a transparent component or, through the unobstructed air when the transparent liquid crystal panel  210  is in the transparent state. In contrast, the pattern density is preferably greater than a lower limit that allows a user to perceive an image shown on the transparent liquid crystal panel  210  with light from the light source  250  when the transparent liquid crystal panel  210  is in the ON the state. 
     Haze is the proportion of diffusion light to totally transmitted light. Alternatively, haze is preferably lower than an upper limit where the user can perceive an image on the liquid crystal display  220  behind the transparent liquid crystal panel  210  via a transparent component or the unobstructed air when the transparent liquid crystal panel  210  is in the transparent state. 
     The left column in the table  1200  represents the pattern density of the prisms  1010 , the middle column represents haze, and the right column represents the results of the visual inspection. In the experiment a single tube type white LED (LP-3020H196W) was used as a light source corresponding to the backlight  270 . Haze was measured using a haze meter HM-150 L2 (manufactured by the Murakami Color Research Laboratory). An object illuminated via the light guide plate  240  and the transparent liquid crystal panel  210  in the transparent state was visually inspected; the result was labeled “OK” when it was perceived that there was a transparent component in front of the object, and labeled “NG” when it was perceived that there was a non-transparent component in front of the object. 
     The visual inspection results were labeled “NG” when the pattern density exceeded 30% or haze exceeded 28% as illustrated in the table  1200 . Thus, preferably, the prisms  1010  are formed so that the pattern density is less than or equal to 30.0%. Alternatively, preferably the prisms  1010  are formed so that haze is less than or equal to 28%. 
       FIGS. 13A, 13B, and 13C  illustrate example patterns for distributing prisms;  FIG. 13A ,  FIG. 13B , and  FIG. 13C  each illustrate an example pattern for distributing prisms when the pattern density is less than or equal to 30.0% and the haze is less than or equal to 28%. In this example, the length W of each of the prisms  1010  along the propagation direction of the incident light is 27.5 μm; and the length L of each of the prisms  1010  in a direction orthogonal to the propagation direction of the incident light is 55 μm. For instance, each of the prisms  1010  is distributed with the pitch of 50 μm and staggered at 50 μm when the pattern density is roughly 30.0% and haze is roughly 28%, as illustrated by the distribution pattern  1301  depicted in  FIG. 13A . 
     The prisms  1010  may also be distributed in a lattice as illustrated by the distribution pattern  1302  depicted in  FIG. 13B . When distributed in a lattice, the prisms  1010  may be distributed so that the pitch is 100 μm. 
     The prisms  1010  may also be distributed so that the number of prisms  1010  is different in each column along a direction orthogonal to the input surface  243  as illustrated by the distribution pattern  1303  depicted in  FIG. 13C . 
       FIG. 14  is the lateral cross-sectional view of another modification to the light guide plate  240 . In this example modification of the light guide plate  240  a trapezoid pattern is formed in the diffusion surface  242 ; the pattern protrudes from the diffusion surface  242  toward the liquid crystal display  220 . The input surface  243  is orthogonal to the diffusion surface  242  and the output surface  241 . A plurality of trapezoid prisms  1410  is created on the diffusion surface  242 . These prisms  1410  reflect the light entering from the input surface  243  causing the light to be substantially uniformly output from the entire output surface  241 ; the prisms  1410  also ensure that the light enters substantially orthogonal to the transparent liquid crystal panel  210 . 
     The trapezoid prisms  1410  are lined up at a predetermined pitch along the propagation direction of incident light entering from the input surface  243 . The prisms  1410  are formed in the diffusion surface  242  as trapezoid protrusions along a direction substantially orthogonal to the propagation direction of incident light from the input surface  243 . Preferably the inclined surface  1400  on the side of the prism  1410  far from the light source  250  is created to totally reflect light propagating within the light guide plate  240  toward the output surface  241  when the light strikes the diffusion surface  242  at a small angle as depicted by the arrow  1401 . Moreover, preferably the inclined surface  1400  is also formed so that when the light propagating through the light guide plate  240  strikes the diffusion surface  242  at a given larger angle, even if the light is not totally reflected, the light output to the outside of the light guide plate  240  by the inclined surface  1400  is also refracted by the inclined surface  1400  toward the diffusion surface  242  as illustrated by the arrow  1402 . The inclined surface  1400  may, for example, form an angle of 45° with the diffusion surface  242 . The inclined surface on the side of the prism  1410  near the light source  250  is not particularly limited, and may be an angle that simplifies molding the light guide plate  240 . 
     The prisms  1410  are preferably formed so the pattern density is less than or equal to 30%, or haze is less than or equal to 28% in this modification example. For instance, the prisms  1410  may be formed so that the width of the prism  1410  along the propagation direction of incident light is 30 μm, and the gap between two adjacent prisms  1410  is 100 μm. 
       FIG. 15  is the lateral cross-sectional view of another modification to the light guide plate  240 . In this modification example, the diffusion surface  242  on the light guide plate  240  is a flat surface so that light propagating through the light guide plate  240  is totally reflected; the diffusion service  242  includes a plurality of trapezoid prisms formed on the output surface  241 . In this modification example, the input surface  243  may be formed at an angle of 45° with the diffusion surface  242 ; hereby, the majority of the light from the light source  250  propagates through the light guide plate  240  at an angle where the light is totally reflected at the diffusion surface  242 . The light source  250  is also arranged so that the direction of maximum light emission therefrom is orthogonal to the input surface  243 . In this situation, the light entering the light guide plate  240  from the input surface  243  is incident on the diffusion surface  242  and the output surface  241  at roughly 45°, and is totally reflected whereby the light propagates through the light guide plate  240 . A plurality of trapezoid prisms  1510  is formed on the output surface  241  to output incident light totally reflected by the diffusion surface  242  toward the transparent liquid crystal panel  210 . 
     The trapezoid prisms  1510  are lined up at a predetermined pitch along the propagation direction of incident light entering from the input surface  243 . The prisms  1510  are formed in the output surface  241  as trapezoid protrusions along a direction substantially orthogonal to the propagation direction of incident light from the input surface  243 . Preferably an inclined surface  1500  on the side of the prism  1510  far from the light source  250  is created so that light propagating through the light guide plate  240  is refracted at the inclined surface  1500  to thereby become light oriented in a direction substantially orthogonal to the output surface  241 , as depicted by the arrow  1501 . The inclined surface  1500  may, for example, form an angle of 70° to 80° with the output surface  241 . The inclined surface on the side of the prism  1510  near the light source  250  is not particularly limited, and may be an angle that simplifies molding the light guide plate  240 . 
     The prisms  1510  are preferably formed so the pattern density is less than or equal to 30%, or haze is less than or equal to 28% in this modification example. For instance, the prisms  1510  may be formed so that the width of the prism  1510  along the propagation direction of incident light is 30 μm, and the gap between two adjacent prisms  1510  is 100 μm. 
       FIG. 16  is the lateral cross-sectional view of another modification to the light guide plate  240 . In this modification example, a saw-like pattern is formed in the diffusion surface  242  of the light guide plate  240 . In this modification example the diffusion surface  242  includes a triangular pattern distributed periodically at a predetermined pitch along the propagation direction of incident light entering from the input surface  243 . The patterns  1610  are formed from a relatively wide first reflection surface  1620   a  that increases the thickness of the light guide plate  240  further away from the light source  250  and a second reflection surface  1620   b , thinner than the first reflection surface  1620   a , that decreases the thickness of the light guide plate  240  further from the light source  250 . The first reflection surface  1620   a  forms and angle of 10° to 20° with the output surface  241  so that light propagating through the light guide plate  240  is totally reflected. Whereas, the second reflection surface  1620   b  forms the larger angle with the output surface  241  than the first reflection surface  1620   a  (e.g., 70° to 80°). The second reflection surface  1620   b  is formed so that light reflected by the first reflection surface  1620   a  and then entering the second reflection surface  1620   b  is totally reflected and oriented in a direction roughly perpendicular to the output surface  241 . 
     A louver film may be placed between the light guide plate  240  and the liquid crystal display  220 ; the louver film blocks light entering diagonally. Note that the louver film may also be placed between the light guide plate  240  and the illuminated gadget  800  when configuring the display component  880  depicted in  FIG. 8 ; the louver film blocks light entering diagonally. 
     The louver film is one example of a direction-selective light shielding component. The louver film is created by arranging a plurality of non-transparent material at a predetermined pitch along the propagation direction of light from the light source  250  inside a sheet-like material produced from a transparent material such as a transparent resin. The plurality of non-transparent materials is orthogonal to a surface facing the light guide plate  240 , and extends along a direction intersecting with the propagation direction of light from the light source  250 . The plurality of non-transparent materials preferably extends along a direction roughly parallel to the direction that the prisms  1010  extend. The predetermined pitch may be the width from the end part of the non-transparent material in the louver film facing the light guide plate  240  to the end part facing the liquid crystal display  220  or the illuminated gadget  800 ; the predetermined pitch may also be less than the aforementioned width. Therefore, even when light from the light source  250  exits from the diffusion surface  242  of the light guide plate  240 , the light is blocked by the non-transparent material which prevents that light from illuminating the liquid crystal display  220  or the illuminated gadget  800 . In contrast, the non-transparent material in the louver film does not block light entering perpendicular to the surface of the liquid crystal display  220  or the illuminated gadget  800 . Therefore, light emitted from the backlight  270  or the illuminated gadget  800  that enters the louver film can pass through the light guide plate  240  and the transparent liquid crystal panel  210  to reach the user. As a result, the user is able to view an image on the liquid crystal display  220  or see light from the illuminated gadget  800  while the transparent liquid crystal panel  210  is in the transparent state and the liquid crystal display  220  shows an image, or while the light emitting element in the illuminated gadget  800  is turned on even when the louver film is provided on the front surface of the liquid crystal display  220  or the illuminated gadget  800 . 
     Light from the light source  250  may leak toward the rear surface of the light guide plate  240 . This light may form an angle with a normal line to the diffusion surface  242  of the light guide plate  240 . Preferably, the light guide plate  240  is configured so that the intensity of the light leaking in the aforementioned manner at an angle greater than the viewing angle of the louver film is twice or more the intensity of the light leaking at less than the viewing angle of the louver film. Light from the light source  250  may leak toward the rear surface of the light guide plate  240 . This light may form an angle with a normal line to the diffusion surface  242  of the light guide plate  240 . Alternatively, the light guide plate  240  may be configured so that the intensity of the light leaking in the aforementioned manner at an angle greater than 45° is twice or more the intensity of the leaking light which forms an angle of less than 45°. 
     The modification example prevents the light exiting from the rear of the light guide plate  240  from illuminating an object behind the light guide plate. The modification thus prevents the light from the transparent backlight  230  that strikes and reflects from an object behind the transparent backlight from being output toward the user, when, for example, the transparent backlight  230  is at the maximum luminance. 
     A polarizer that allows polarized light with a polarization plane oriented in a predetermined direction to pass therethrough may be placed between the liquid crystal display  220  or the illuminated gadget  800  and the light guide plate  240 . The polarizer may be provided in place of or in addition to the louver film. The polarizer is arranged so that preferably the transmission axis of the polarizer is the same direction as the transmission axis of the polarization plate on the rear surface of the transparent liquid crystal panel  210 . The polarizer attenuates the light exiting the transparent backlight  230  from the diffusion surface  242  and passing therethrough. Additionally, reflection or dispersion at the liquid crystal display  220  or the illuminated gadget  800  changes the polarization direction of this light, the polarizer further attenuates the light before the same re-enters the light guide plate  240 . It is thereby possible to prevent light exiting from the rear of the light guide plate  240  from illuminating an object behind the light guide plate. The modification thus prevents the light from the transparent backlight  230  that strikes and reflects from an object behind the transparent backlight from being output toward the user, when, for example, the transparent backlight  230  is at the maximum luminance. 
     The game machine  10  is one example of a game machine. In addition to the pinball machine, the game machine may be a slot machine. 
     The processes described as operations of the presentation controller  300  in the above description may be implemented by a processor controlling the other hardware provided to the game machine  10  or the display device  100  in accordance with a program. That is, a processor may operate in accordance with a program to control pieces of hardware, whereby the processes described in relation to the presentation controller  300  are implemented by operation of each piece of hardware including the processor and memory and the like in cooperation with a program. That is, the aforementioned processes may be implemented on a computer, so to speak. The computer may load a program for controlling execution of the above-described processes, operate according to the loaded program, and thereby execute the aforementioned processes. The computer may load the aforementioned program from a computer readable medium storing the program. 
     The present invention is described by way of the embodiments; however, the technical scope of the present invention is not limited to the above-described embodiments. It is obvious to a person skilled in the art that the above described embodiments can be modified or improved in various ways. The scope of the claims makes it clear whether such kinds of modifications or improvements to the embodiments are within the technical scope of the present invention. 
     It should be noted that unless explicitly stated with terms such as “before”, “prior to”, and the like, and unless the output of a prior process is used in a subsequent process, the sequence of execution of operations, procedures, steps, and stages within the devices, systems, programs, and methods expressed in the scope of the claims, the specification, and the drawings, may be executed any order as desired. The terms “first”, “next”, and the like are used for convenience when describing operational flows within the scope of the claims, the specification, and in the drawings, and does not mean that execution in this order is required.