Patent Publication Number: US-2015084858-A1

Title: Display device, content display method, and a non-transitory computer-readable storage medium

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a display device, a content display method, and a non-transitory computer-readable storage medium. 
     2. Related Art 
     Recently, a digital signage has been known as a tool for advertisements for general public viewers in a public place such as a store or a station. The digital signage is configured to readily change the contents of advertisements. Therefore, latest information or the like is quickly provided for the viewers, and an excellent effect of advertisement is provided, compared with a conventional sign (e.g. JP 2011-150221 A, JP 2012-128210 A). 
     SUMMARY 
     However, advertisement display on a conventional digital signage unfortunately provides one-way advertisements in which predetermined advertisements are displayed in a cycle, and the advertisements are unlikely to have an effect for viewers who are not interested in the advertisements. 
     A purpose of the present invention is to provide an increased advertising effect by reflecting the interest of the viewers. 
     To solve the above-mentioned problem, according to a first aspect of the present invention, a display device includes a display unit, a display control unit, and a content evaluation unit. The display unit displays an image. The display control unit switches among a plurality of kinds of content and displays the switched content on the display unit. The content evaluation unit evaluates an affirmation level with respect to the content displayed on the display unit. The display control unit determines the content displayed on the display unit based on the affirmation level by the content evaluation unit. 
     According to an embodiment of the present invention, an advertising effect is further increased reflecting the interest of the viewers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating a schematic configuration of a display system according to a first embodiment; 
         FIG. 2  is a block diagram illustrating a functional configuration of a digital signage; 
         FIG. 3  is a front view illustrating a schematic configuration of a screen unit of the digital signage; 
         FIG. 4  is a block diagram illustrating a functional configuration of a control unit of the digital signage; 
         FIG. 5  is a flowchart describing display control processing according to the first embodiment; 
         FIG. 6  is a flowchart describing affirmation-level calculation processing; 
         FIG. 7A  is a view illustrating an exemplary advertisement displayed on a display unit; 
         FIG. 7B  is a view illustrating an exemplary advertisement displayed on the display unit; 
         FIG. 7C  is a view illustrating an exemplary advertisement displayed on the display unit; 
         FIG. 7D  is a view illustrating an exemplary advertisement displayed on the display unit; 
         FIG. 8  is a flowchart describing display control processing according to a second embodiment; 
         FIG. 9  is a flowchart describing an order of displaying advertisements; 
         FIG. 10  is a flowchart describing an order of displaying advertisements; 
         FIG. 11A  is a view illustrating an exemplary advertisement displayed on the display unit; 
         FIG. 11B  is a view illustrating an exemplary advertisement displayed on the display unit; 
         FIG. 11C  is a view illustrating an exemplary advertisement displayed on the display unit; 
         FIG. 11D  is a view illustrating an exemplary advertisement displayed on the display unit; 
         FIG. 12  is a flowchart describing display control processing according to a third embodiment; 
         FIG. 13  is a flowchart describing an order of displaying advertisements; 
         FIG. 14  is a flowchart describing display control processing according to a fourth embodiment; and 
         FIG. 15  is a view illustrating an exemplary advertisement displayed on the display unit. 
     
    
    
     DETAILED DESCRIPTION 
     The best mode for carrying out the present invention will be described below using the drawings. It is noted that various limitations technically preferable are assigned to the following embodiments to carry out the present invention, but the scope of the present invention is not limited to the following embodiments and exemplary illustrations. 
     First Embodiment 
       FIG. 1  is a block diagram illustrating a schematic configuration of a display system according to a first embodiment. The display system  1  includes a digital signage  2  as a display device according to an embodiment of the present invention, and a server  5  capable of communicating with the digital signage  2  through a network N. The server  5  stores data or the like of an advertisement displayed on the digital signage  2 , and the stored data or the like is configured to be downloaded to the digital signage  2 . 
     [Digital Signage] 
       FIG. 2  is a block diagram illustrating a main control configuration of the digital signage  2 . The digital signage  2  includes a projection unit  21  and a screen unit  22 . The projection unit  21  radiates image projecting light of an image of an advertisement or the like. The screen unit  22  receives the image projecting light radiated from the projection unit  21  on a back side thereof and projects the received light toward a front side thereof. The projection unit  21  and the screen unit  22  will be described below. 
     The projection unit  21  includes a control unit  23 , a projector  24 , a storage unit  25 , and a communication unit  26 . The control unit  23  controls each unit based on a processing program and various data. The projector  24  is connected to the control unit  23 , converts image data (data of images including moving and still images) output from the control unit  23  to the image projecting light, and radiates the light toward the screen unit  22 . The storage unit  25  stores the processing program and the various data. The communication unit  26  communicates with the server  5  through the network N. 
     The screen unit  22  will be described next. 
       FIG. 3  is a front view illustrating a schematic configuration of the screen unit  22 . As illustrated in  FIG. 3 , the screen unit  22  includes a square display panel  27  and a base  28  configured to support the display panel  27 . 
     The display panel  27  includes one translucent panel  29 , for example an acrylic sheet, substantially orthogonal to a direction in which the image projecting light is radiated. The translucent panel  29  has a back side on which a back projection film screen is laminated. The film screen has a back surface on which a film-shaped Fresnel lens is laminated. The display panel  27  and the above-described projector  24  constitute a display unit  240  (see  FIG. 4 ). 
     At an upper part of the display panel  27 , an imaging unit  30 , such as a camera, is provided. The imaging unit  30  picks up an image of a space facing the display panel  27  in real time to generate image data. The imaging unit  30  includes a camera including an optical system and an image sensor, and an imaging control unit configured to control the camera. The camera and the imaging control unit are not illustrated in the figure. Any of a visible light camera or an infrared camera may be used as the camera. 
     The camera has an optical system constituted by a plurality of lenses, and having a focal length fixed to a predetermined distance to increase a depth of field. The optical system has an optical axis oriented in a direction in which an image of a person&#39;s face facing the display panel  27  can be picked up. 
     The image sensor includes an image sensor such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS). The image sensor converts an optical image obtained through the optical system to a two-dimensional image signal. 
     The imaging control unit controls picking up an image of a specific object by the image sensor. That is, the imaging control unit includes a timing generator, a driver, and the like which are not illustrated. In the imaging control unit, the timing generator and the driver drive the image sensor to perform scanning, the optical image having been received is periodically converted to a two-dimensional image signal, a frame image is read for each screen from an imaging area of the image sensor, and the image data is generated. 
     The base  28  includes an operation unit  32  operated through a button, a sound output unit  33  such as a speaker, and a sound input unit  34  such as a microphone. 
     The operation unit  32 , the sound output unit  33 , the sound input unit  34 , and the imaging unit  30  are connected to the control unit  23 , as illustrated in  FIG. 2 . 
     The control unit  23  includes a CPU configured to execute various programs for predetermined calculation or control of each unit, and a memory serving as a work area upon execution of the program (neither is illustrated). 
     The control unit  23  performs various processing based on an operation signal from an operation unit  32 , reads image data or sound data from the storage unit  25  as required, and performs display control of the projector  24  and sound output control of the sound output unit  33 . 
     Further, the control unit  23  stores image data obtained from the imaging unit  30  and sound data obtained from the sound input unit  34  in the storage unit  25 . 
     The control unit  23  controls the communication unit  26  for communication with the server  5 , depending on an operation signal from the operation unit  32 . Information obtained through the communication is stored in the storage unit  25 . 
     [Display Control Processing in Digital Signage] 
     In the present embodiment, display control processing is performed in the digital signage  2 . 
     Therefore, as illustrated in  FIG. 2 , the storage unit  25  of the digital signage  2  stores a processing program  251  for display control processing. Various data such as setting data, image data, and sound data required for the display control processing are stored in a data storage unit  252  in the storage unit  25 . 
     The control unit  23  of the digital signage  2  is a so-called computer. The control unit  23  executes a processing program  251  for the display control processing, and functions as a face image extraction unit  231 , a content evaluation unit  232 , and a display control unit  233  as shown in  FIG. 4 . 
     It is noted that, in the following description, any of a picked-up image, a face image, an image to be displayed, and other images are made into data for processing. 
     The face image extraction unit  231  extracts the face image of a viewer from images picked up by the imaging unit  30 . 
     Based on the extracted face image, the content evaluation unit  232  evaluates an advertisement having content of a kind displayed on the display unit  240 . 
     The display control unit  233  switches among a plurality of kinds of advertisements to display any of them on the display unit  240 , and determine content to be displayed on the display unit  240  based on an evaluation result of the content evaluation unit  232 . Therefore, based on the expression of the viewer viewing an advertisement, an evaluation of the advertisement is made. Based on the evaluation result, for example, the advertisement is displayed for a longer period of time or the advertisement is switched to another one, whereby an advertisement to be displayed is allowed to be determined. 
     Further, supplementary description will be given of the units  231  to  233 . 
     [Face Image Extraction Unit] 
     The face image extraction unit  231  extracts the face image from the images picked up by the imaging unit  30  based on a predetermined algorithm. 
     The face image extraction unit  231  extracts the face image from the images picked up by the imaging unit  30  using, for example, the adaboost algorithm. 
     The adaboost algorithm uses a plurality of classifiers having a low accuracy in recognition of face image (e.g., recognition accuracy slightly higher than 0.5). The classifiers are previously weighted, respectively, based on learning using a sample face image and a non-face image. 
     The face image extraction unit  231  searches the whole picked-up images with the classifiers. As a result, the face image extraction unit  231  recognizes that a face is in an area in which the total of scores (weighted scores) obtained from the classifiers is equal to or larger than a predetermined threshold. 
     The classifier uses, for example, a plurality of pattern images called Haar-Like feature which expresses a partial face feature with black and white rectangular areas and arrangement thereof. The pattern images are also weighted, respectively, based on the learning using a sample face image and a non-face image. The scores of the classifier is calculated based on a determination result of coincidence between the pattern image and a searched area of the picked-up image. 
     The searched area is used for extracting the face image, and has a plurality of sizes. The classifiers are also prepared corresponding to the plurality of sizes. The face image is detected based on various sizes. As a result, not only the position of the face image within the range of picking up the image but also the size of the face image can be obtained. 
     It is noted that the present invention provides an exemplary process of extracting the face image using the face image extraction unit  231 , but any other well-known technique for extracting the face image can be employed without being restricted to the above-mentioned process. 
     [Content Evaluation Unit] 
     First, the content evaluation unit  232  determines that the face image extracted from the face image extraction unit  231  is similar to any of a plurality of kinds of expressions to recognize the expression of the face image. In the present embodiment, based on a result of recognition thereof, evaluation of the advertisement display on the display unit  240  is made. 
     The kind of expression includes, for example, an expression showing a positive emotion such as a delighted face, joyful face, happy face, calm face, or relaxed face, or an expression showing a negative emotion such as a sad face, angry face, or disgusted face. It is noted that the type of expression is not limited to them, increased expressions or reduced expressions can be also determined, and an expression other than the above-mentioned expressions can be determined. 
     For determination of the expression, for example, the adaboost algorithm can be used. 
     In the determination thereof, during learning, a plurality of classifiers is generated using an image representing any one of the various expressions and an image representing another expression. Further, the classifier preferably has a pattern image of Haar-Like feature. Therefore, the plurality of classifiers each configured to identify one kind of expression, is obtained. 
     Further, a similar process is applied to generate a plurality of classifiers for various expressions, respectively, for identification of the other kinds of expressions. 
     In such a configuration, evaluation values are set to the above-mentioned expressions. A positive value or a positive evaluation value is set to the positive emotion. A negative value or a negative evaluation value is set to the negative emotion. It is noted that the evaluation value may differ for each expression, and a plurality of expressions may have the same evaluation value. The process of obtaining an evaluation value is an example, and another well-known expression evaluating method can be employed without being limited to the above-mentioned process. 
     The content evaluation unit  232  derives, as described above, evaluation values for the face images picked up at predetermined intervals and extracted by the face image extraction unit  231 , averages the evaluation values to derive an affirmation level Pe based on expression recognition, and evaluates, based on the affirmation level Pe, the advertisement of a kind displayed on the display unit  240 . The affirmation level Pe is derived from the following formula (1), where “E” represents the evaluation values obtained at predetermined intervals, and “N” represents the number of times of obtaining the evaluation values or an expression recognition frequency. 
       Affirmation level  Pe=ΣE/N   (1)
 
     The content evaluation unit  232  recognizes a line of sight to the display panel  27  based on a face image extracted from the face image extraction unit  231 , and evaluates an expression of the face image on condition that the line of sight is recognized. When the content evaluation unit  232  does not recognize the line of sight, the evaluation of the expression of the face image is not carried out. 
     The recognition of line of sight to the display panel  27  can be carried out based on the face image by, for example, setting an inner corner of a viewer&#39;s eye as a reference point, setting an iris thereof as a moving point, and determining a positional relationship between the inner corner and the iris of the viewer&#39;s eye. It is noted that the process for recognition of line of sight is not limited to this embodiment, and various methods which have been publicly known can be employed. 
     The content evaluation unit  232  recognizes (detects) the line of sight to the display panel  27  based on the face image extracted from the face image extraction unit  231 , and evaluates, based on a result of the recognition of line of sight, the advertisement of a kind displayed on the display unit  240 . In the present embodiment, the content evaluation unit  232  derives time for recognition of line of sight to the display panel  27 , and a frequency of shift of the line of sight from the display panel  27 . An affirmation level P1 based on recognition of line of sight is derived from the time and frequency. Based on the affirmation level P1, the content evaluation unit  232  evaluates the advertisement of a kind displayed on the display unit  240 . The affirmation level P1 is derived from the following formula (2), where, “Ton” represents time for recognition of line of sight to the display panel  27 , and “Nout” represents a frequency of shift of the line of sight from the display panel  27 . 
       Affirmation level  P 1= T on* k 1− N out* k 2  (2)
 
     It is noted that in formula (2), k1 and k2 represent a count for time for recognition of line of sight to the display panel  27 , and a coefficient for the frequency of shift of the line of sight from the display panel  27 , respectively. 
     In the present embodiment, based on the time for recognition of line of sight to the display panel  27 , evaluation is carried out for the advertisement of a kind displayed on the display unit  240 , but evaluation may be carried out for the advertisement of a kind displayed on the display unit  240  not based on the time for recognition but based on a frequency of recognition of line of sight. 
     The content evaluation unit  232  derives an affirmation level P being the evaluation for the advertisement display on the display unit  240  based on the affirmation level Pe and the affirmation level P1 which are derived as described above. Specifically, the affirmation level P is derived by the following formula (3). 
       Affirmation level  P =affirmation level  Pe +affirmation level  P 1  (3)
 
     It is noted that the affirmation level Pe and the affirmation level P1 may be weighted, respectively. 
     In the present embodiment, the affirmation level P is derived as described above, but for example, as described in JP 2013-051688 A, the affirmation level P may be derived based on a direction of the viewer&#39;s face. 
     [Display Control Unit] 
     The display control unit  233  controls the display unit  240  to switch and display a plurality of kinds of advertisements. 
     The display control unit  233  determines an advertisement to be displayed on the display unit  240  based on an evaluation result of the content evaluation unit  232 . It will be described below which advertisement is displayed. 
     The display control processing performed at the control unit  23  of the digital signage  2  configured as described above, will be described with reference to  FIG. 5 . 
     First, the control unit  23  starts display of the advertisement as the content (step S 101 ). Specifically, for example, four kinds of advertisements illustrated in  FIG. 7A  to  FIG. 7D  are switched to be displayed every predetermined time (e.g. 10 seconds) on the display unit  240 . More specifically, the display is switched every predetermined time in an order of an “advertisement A-main” image illustrated in FIG.  7 A, an “advertisement B-main” image illustrated in  FIG. 7B , an “advertisement C-main” image illustrated in  FIG. 7C , an “advertisement D-main” image illustrated in  FIG. 7D , and an “advertisement A main” image illustrated in  FIG. 7A . The display control is performed in parallel with the following processing. 
     Next, the control unit  23  causes the imaging unit  30  to pick up an image of a space in front of the display panel  27  of the digital signage  2  (step S 102 ). 
     The control unit  23  performs face detection processing for detecting the face image from the picked-up image (step S 103 ). The control unit  23  determines whether the face image has been detected or not (step S 104 ). When it is determined that the face image has been detected (step S 104 :Y), the control unit  23  causes the face image extraction unit  231  to function to extract the face image from the picked-up images (step S 105 ). 
     The control unit  23  performs affirmation-level calculation processing based on the extracted face image (step S 106 ). 
     The affirmation-level calculation processing will be described with reference to  FIG. 6 . 
     The control unit  23  recognizes the line of sight to the display panel  27 , as described above (step S 201 ). Further, the control unit  23  calculates the affirmation level P1 based on recognition of line of sight from a result of the recognition of line of sight, as described above, and a result of the calculation is newly stored for example in a memory as a latest affirmation level P1 (step S 202 ). 
     After the recognition of line of sight, the control unit  23  determines whether the line of sight to the display panel  27  has been recognized (step S 203 ). When it is determined that the line of sight has been recognized (step S 203 :Y), the control unit  23  increments the expression recognition frequency N (step S 204 ), and performs expression recognition processing for recognizing an expression of the face image as described above (step S 205 ). 
     The control unit  23  acquires an evaluation value based on a result of recognition of the expression, calculates the affirmation level Pe based on the expression recognition as described above, and newly stores the result for example in the memory as the latest affirmation level Pe (step S 206 ). 
     When it is determined in step S 203  that the line of sight has not been recognized (step S 203 :N), the control unit  23  performs the processing of step S 207  without performing processing of steps S 204  to S 206 . 
     In step S 207 , the control unit  23  calculates the affirmation level P from the latest affirmation level Pe and the affirmation level P1 which have been derived as described above (step S 207 ), and the processing is finished. 
     Returning to  FIG. 5 , in step S 107 , the control unit  23  determines whether the affirmation level P calculated in the affirmation-level calculation processing exceeds a predetermined threshold th (step S 107 ). When it is determined that the affirmation level P exceeds the threshold th (step S 107 :Y), the control unit  23  determines that the viewer has an interest in the advertisement of a kind being displayed on the display unit  240  at present, and performs display time extension processing for extending time for displaying the advertisement (step S 108 ). The extension time of the display is set to, for example, ten seconds, but the present invention is not limited to this embodiment. When it is determined that the affirmation level P does not exceed the threshold th (step S 107 :N), the control unit  23  determines that the viewer does not have an interest in the advertisement of a kind being displayed on the display unit  240  at present, and performs display change processing for changing the advertisement of the kind being displayed on the display unit  240  at present to an advertisement of another kind (step S 109 ). For example, the “advertisement A-main” image which is displayed on the display unit  240 , as illustrated in  FIG. 7A , is changed to another “advertisement B-main” image illustrated in  FIG. 7B . It is noted that the advertisement after being changed may be selected at random. 
     The control unit  23  performs display time accumulation processing of accumulating display time of advertisements of a kind being displayed on the display unit  240  at present, and newly storing the time in the memory, for example (step S 110 ), and proceeds to the processing of step S 102 . Therefore, for each kind of advertisement, the display time on the display unit  240  can be calculated, and for example, the calculated time can be used for marketing. 
     When it is determined in step S 104  that the face image has not been detected (step S 104 :N), the control unit  23  determines whether to terminate display of the advertisement (step S 111 ). More specifically, for example, it is determined whether to terminate the display of the advertisement, based on whether predetermined termination operation has been performed. When it is determined that the display of the advertisement is not terminated (step S 111 :N), the control unit  23  advances the processing to step S 102 . Meanwhile, when it is determined to terminate the display of the advertisement, (step S 111 :Y), the control unit  23  finishes this processing. 
     As described above, in the first embodiment, the advertisement is displayed on the display unit  240  for a longer period of time or the content of the advertisement is changed according to the expression of the viewer viewing the advertisement. Therefore, the interest of the viewer is reflected, and an advertising effect is increased. Since the display system does not require the viewer, for example, to select one from the displayed contents of the advertisement to change the advertisement, the display system provides a high advertising effect, even if the viewer does not have a strong interest in the advertisement. 
     Second Embodiment 
     Next, a second embodiment of the present invention will be described below. It is noted that description of a functional configuration of a digital signage  2  according to the second embodiment will be omitted, since the functional configuration is similar to that of the digital signage described above according to the first embodiment. 
     Display control processing according to the second embodiment will be described with reference to  FIG. 8 . 
     First, a control unit  23  causes an imaging unit  30  to pick up an image of a space in front of a display panel  27  of the digital signage  2  (step S 301 ). 
     The control unit  23  performs face detection processing for detecting a face image from the picked-up image (step S 302 ). The control unit  23  determines whether the face image has been detected (step S 303 ). When it is determined that the face image has been detected (step S 303 :Y), the control unit  23  starts display of an advertisement as content (step S 304 ). In such a configuration, for example, four kinds of advertisements illustrated in  FIGS. 7A to 7D  are displayed on a display unit  240  in a digested manner, while being switched every predetermined time. That is, as illustrated in  FIG. 9 , the control unit  23  displays an “advertisement A-main” image for a predetermined time (e.g. three seconds) (step S 401 ), an “advertisement B-main” image for a predetermined time (step S 402 ), an “advertisement C-main” image for a predetermined time (step S 403 ), and an “advertisement D-main” image for a predetermined time (step S 404 ) in the digested manner, and finishes the digest display. 
     Then, the control unit  23  causes the face image extraction unit  231  to function to extract the face image from the picked-up image (step S 305 ), and performs the affirmation-level calculation processing (step S 306 ). 
     The control unit  23  determines whether the digest display of the advertisements is finished (step S 307 ). When it is determined that the digest display is not finished (step S 307 :N), the control unit  23  causes the imaging unit  30  to pick up an image (step S 308 ) followed by processing of step S 305 . The control unit  23  repeats the processing of steps S 305  to S 308  until the finish of the digest display, and calculates the affirmation level for each kind of advertisement. 
     Meanwhile, when it is determined that the digest display is finished (step S 307 :Y), the control unit  23  performs display order determination processing for determining an order of displaying detailed advertisements, based on affirmation levels of advertisements according to kinds (step S 309 ). More specifically, the control unit  23  determines the display order to display the detailed advertisements in descending order of affirmation levels. The control unit  23  starts the display of the detailed advertisements in the display order determined in step S 309  (step S 310 ). For example, when calculation of affirmation level for each kind of advertisement results in descending order of affirmation levels in the order of an advertisement A, an advertisement D, an advertisement B, and an advertisement C, at first, an “advertisement A-sub” image is displayed as detailed display of the advertisement A, next, an “advertisement D-sub” image is displayed as detailed display of the advertisement D, and then an “advertisement B-sub” image is displayed as detailed display of the advertisement B, and finally, an “advertisement C-sub” image is displayed as detailed display of the advertisement C. In such a configuration, when the “advertisement A-sub” image includes four images, the “advertisement B-sub” image includes three images, the “advertisement C-sub” image includes five images, and the “advertisement D-sub” image includes two images, the control unit  23  first displays, as illustrated in  FIG. 10 , an “advertisement A-sub 1” image to an “advertisement A-sub 4” image for a predetermined time (e.g. five seconds), respectively (step S 501 ), an “advertisement D-sub 1” image to an “advertisement D-sub 2” image for a predetermined time, respectively (step S 502 ), an “advertisement B-sub 1” image to an “advertisement B-sub 3” image for a predetermined time, respectively (step S 503 ), and an “advertisement C-sub 1” image to an “advertisement C-sub 5” image for a predetermined time, respectively (step S 504 ), and the procedure is repetitively performed. In such a configuration, the “advertisement A-sub 1” image includes, for example, an image as illustrated in  FIG. 11A , the “advertisement A-sub 2” image includes, for example, an image as illustrated in  FIG. 11B , the “advertisement A-sub 3” image includes, for example, an image as illustrated in  FIG. 11C , and the “advertisement A-sub 4” image includes, for example, an image as illustrated in  FIG. 11D . The “advertisement A-sub” images are detailed images displayed relating to the advertisement A-main” image illustrated in  FIG. 7A . The “advertisement B-sub” images, “advertisement C-sub” images, and “advertisement D-sub” images also have a plurality of detailed images displayed relating to the “advertisement B-main” image, the “advertisement C-main” image, and the “advertisement D-main” image, respectively, in a similar manner. 
     In such a manner, in the second embodiment, the order of detailed display of the advertisement displayed on the display unit  240  is determined according to viewer&#39;s expression viewing the advertisement. Therefore, the viewer can see the advertisement in the order of interest, and the advertising effect is increased reflecting the interest of the viewer. 
     Third Embodiment 
     Next, a third embodiment of the present invention will be described below. It is noted that description of a functional configuration of a digital signage  2  according to the third embodiment will be omitted, since the functional configuration is similar to that of the digital signage described above according to the first embodiment. 
     Display control processing according to the third embodiment will be described with reference to  FIG. 12 . 
     First, a control unit  23  starts display of an advertisement having a main scenario as content (step S 601 ). More specifically, for example, four kinds of advertisements illustrated in  FIGS. 7A to 7D  are switched to be displayed every predetermined time (e.g. 10 seconds) on the display unit  240 . That is, the control unit  23  switches the display every predetermined time, in an order of the “advertisement A-main” image illustrated in  FIG. 7A , the “advertisement B-main” image illustrated in  FIG. 7B , the “advertisement C-main” image illustrated in  FIG. 7C , the “advertisement D-main” image illustrated in  FIG. 7D , and the “advertisement A-main” image illustrated in  FIG. 7A . The display control is performed simultaneously with the following processing. 
     Next, the control unit  23  causes the imaging unit  30  to pick up an image of a space in front of the display panel  27  of the digital signage  2  (step S 602 ). 
     The control unit  23  performs face detection processing for detecting a face image from the picked-up image (step S 603 ). The control unit  23  determines whether a face image has been detected (step S 604 ). When it is determined that the face image has been detected (step S 604 :Y), the control unit  23  causes the face image extraction unit  231  to function to extract the face image from the picked-up images (step S 605 ), and performs the affirmation-level calculation processing based on the extracted face image (step S 606 ). 
     The control unit  23  determines whether an affirmation level P calculated in the affirmation-level calculation processing exceeds a threshold th (step S 107 ). When it is determined that the affirmation level P exceeds the threshold th (step S 607 :Y), the control unit  23  determines that the viewer has an interest in the advertisement of a kind being displayed on the display unit  240  at present, and an advertisement having a sub scenario relating to the advertisement having the main scenario is displayed (step S 608 ). For example, while the “advertisement A-main” image is displayed, as the advertisement having the main scenario, on the display unit  240 , the control unit  23  switches and displays the “advertisement A-sub 1” image to the “advertisement A-sub 4” image relating to the “advertisement A-main” image for a predetermined time (e.g. five seconds), respectively, when it is determined that the calculated affirmation level P exceeds the threshold th. 
     Subsequently, the control unit  23  advances the processing to step S 605 , after picking up the image by the imaging unit  30  (step S 609 ). For example, when the “advertisement A-sub” image is displayed, the control unit  23  repetitively displays the “advertisement A-sub” image, as long as it is determined that the affirmation level P exceeds the threshold th in step S 607 . Display of the advertisement having the sub scenario may be finished to be switched to the display of the advertisement having the main scenario. 
     When it is determined in step S 607  that the affirmation level P does not exceed the threshold th (step S 607 :N), the control unit  23  determines that the viewer does not have an interest in the advertisement of a kind being displayed on the display unit  240  at present, and advances the processing to step S 601  for displaying the advertisement having the main scenario. It is noted that the present embodiment may be configured such that on condition that the advertisement having the sub scenario has completed, the advertisement may be shifted to the one having the main scenario, when it is determined that the affirmation level P does not exceed the threshold th. Alternatively, the present embodiment may be configured such that the advertisement having the sub scenario may be shifted to the one having the main scenario during display of the advertisement having the sub scenario, when it is determined that the affirmation level P does not exceed the threshold th. 
     When it is determined that the face image has not been detected in step S 604  (step S 604 :N), the control unit  23  determines whether to terminate display of the advertisement (step S 610 ). When it is determined that the display of the advertisement is not finished (step S 610 :N), the control unit  23  advances the processing to step S 602 . Meanwhile, when it is determined to terminate the display of the advertisement, (step S 610 :Y), the control unit  23  finishes this processing. 
     The present embodiment is configured as described above, and for example, the advertisements are switchably displayed as described below. 
     As illustrated in  FIG. 13 , the control unit  23  first displays the “advertisement A-main” image for a predetermined time (step S 701 ). At that time, when it is determined that the affirmation level P exceeds the threshold th (step S 702 :Y), the control unit  23  displays the “advertisement A-sub 1” image to “advertisement A-sub 4” image for a predetermined time, respectively (step S 703 ), and as long as the affirmation level P exceeds the threshold th (step S 704 :Y), the “advertisement A-sub” images are repetitively displayed. 
     In step S 702  or step S 704 , when it is determined that the affirmation level P does not exceed the threshold th (step S 702 :N, step S 704 :N), the control unit  23  displays an “advertisement B-main” image for a predetermined time (step S 705 ). At that time, when it is determined that the affirmation level P exceeds the threshold th (step S 706 :Y), the control unit  23  displays the “advertisement B-sub 1” image to “advertisement B-sub 3” image for a predetermined time, respectively (step S 707 ), and as long as the affirmation level P exceeds the threshold th (step S 708 :Y), the “advertisement B-sub” images are repetitively displayed. 
     In step S 706  or step S 708 , when it is determined that the affirmation level P does not exceed the threshold th (step S 706 :N, step S 708 :N), the control unit  23  displays the “advertisement C-main” image for a predetermined time (step S 709 ). At that time, when it is determined that the affirmation level P exceeds the threshold th (step S 710 :Y), the control unit  23  displays the “advertisement C-sub 1” image to “advertisement C-sub 5” image for a predetermined time, respectively (step S 711 ), and as long as the affirmation level P exceeds the threshold th (step S 712 :Y), the “advertisement C-sub” images are repetitively displayed. 
     In step S 710  or step S 712 , when it is determined that the affirmation level P does not exceed the threshold th (step S 710 :N, step S 712 :N), the control unit  23  displays an “advertisement D-main” image for a predetermined time (step S 713 ). At that time, when it is determined that the affirmation level P exceeds the threshold th (step S 714 :Y), the control unit  23  displays the “advertisement D-sub 1” image to “advertisement D-sub 2” image for a predetermined time, respectively (step S 715 ), and as long as the affirmation level P exceeds the threshold th (step S 716 :Y), the “advertisement D-sub” images are repetitively displayed. 
     In step S 714  or step S 716 , when it is determined that the affirmation level P does not exceed the threshold th (step S 714 :N, step S 716 :N), the control unit  23  advances the processing to step S 701 . Subsequently, these processing is repetitively performed. 
     As described above, the third embodiment is configured such that the advertisement in which the viewer has an interest is determined based on the viewer&#39;s expression viewing the advertisement, and the advertisement in which the viewer has an interest can be displayed in detail. Therefore, the viewer&#39;s interest is reflected to increase the advertising effect. Further, in the third embodiment, the display system does not require the viewer to select a required advertisement, so that the viewer does not have any trouble, and the advertising effect is increased. 
     Fourth Embodiment 
     Next, a fourth embodiment of the present invention will be described below. It is noted that description of a functional configuration of the digital signage  2  according to the fourth embodiment will be omitted, since the functional configuration is similar to that of the digital signage described above according to the first embodiment. 
     Display control processing according to the fourth embodiment will be described with reference to  FIG. 14 . The fourth embodiment is different from the first embodiment in that an affirmation level P has a threshold th1 and a threshold th2 set to be smaller than the threshold th1, and it is determined whether the affirmation level P exceeds any of the thresholds to determine an advertisement to be displayed on the display unit  240 . It is noted that in the display control processing illustrated in  FIG. 14 , a similar procedure is applied to step S 801  to step S 806  as that in step S 101  to step S 106  of the display control processing according to the first embodiment illustrated in  FIG. 5 , and thus the description will not be repeated. 
     In step S 807 , a control unit  23  determines whether the affirmation level P calculated in the affirmation-level calculation processing exceeds the threshold th1 (step S 807 ). The control unit  23  determines whether the affirmation level P has a first affirmative evaluation. When it is determined that the affirmation level P exceeds the threshold th1 (step S 807 :Y), the control unit  23  determines that the viewer has a great interest in the advertisement of a kind being displayed on the display unit  240  at present, and buying information display processing is performed for displaying buying information relating to the advertisement (step S 808 ). For example, the buying information includes an advertisement as illustrated in  FIG. 15 , and displays, for example, a method for buying a product displayed in the advertisement, a product display place, or the like. 
     Meanwhile, when it is determined that the affirmation level P does not exceed the threshold th1 (step S 807 :N), the control unit  23  determines whether the affirmation level P exceeds the threshold th2 (step S 809 ). That is, the control unit  23  determines whether the affirmation level P has a second affirmative evaluation. When it is determined that the affirmation level P exceeds the threshold th2 (step S 809 :Y), the control unit  23  determines that the viewer has some interest in an advertisement of a kind being displayed on the display unit  240  at present, and performs the display time extension processing (step S 810 ). When it is determined that the affirmation level P does not exceed the threshold th2 (step S 809 :N), the control unit  23  determines that the viewer does not have an interest in the advertisement of a kind being displayed on the display unit  240  at present, and the display change processing is performed (step S 811 ). 
     Subsequently, the control unit  23  advances the processing to step S 802 , after the display time accumulation processing has been performed (step S 812 ). 
     When it is determined in step S 804  that the face image has not been detected (step S 804 :N), the control unit  23  determines whether to terminate display of the advertisement (step S 813 ). When it is determined that the display of the advertisement is not finished (step S 813 :N), the control unit  23  advances the processing to step S 802 . When it is determined that the display of the advertisement is finished (step S 813 :Y), on the other hand, the control unit  23  finishes this processing. 
     As described above, in the fourth embodiment, detailed information relating to the advertisement displayed on the display unit  240  is displayed, the advertisement is displayed longer, or the content of the advertisement is changed according to the expression of the viewer viewing the advertisement, so that display is performed according to an interest degree of the viewer to increase the advertising effect. 
     As described above, according to the first to fourth embodiments, the display unit  240  displays an image thereon. The control unit  23  switchably displays a plurality of kinds of advertisements on the display unit  240 . The control unit  23  evaluates the affirmation level of the advertisement displayed on the display unit  240 . The control unit  23  determines the advertisement displayed on the display unit  240  based on the affirmation level. Accordingly, the interest of the viewer is reflected to increase the advertising effect. 
     According to the first to fourth embodiments, the imaging unit  30  picks up an image. The control unit  23  extracts an image of a person&#39;s face from the image picked up by the imaging unit  30 . The control unit  23  evaluates an affirmation level of an advertisement displayed on the display unit  240  based on the face image. Accordingly, the interest degree of the viewer with respect to content displayed on the display unit is evaluated based on the face image of the viewer. 
     According to the first to fourth embodiments, the control unit  23  evaluates an expression based on an extracted face image, and evaluates an advertisement of a kind displayed on the display unit  240  based on the affirmation level of the expression of the face image. Accordingly, the interest of the viewer in content can be evaluated based on an expression of the viewer&#39;s face, and the advertising effect is increased. 
     According to the first to fourth embodiments, the control unit  23  determines which of a plurality of kinds of preset expressions an extracted face image resembles. Accordingly, an expression of a viewer&#39;s face is readily determined. 
     According to the first to fourth embodiments, the control unit  23  derives evaluation values representing an affirmation level of an expression of a face image at predetermined intervals, averages the evaluation values, and evaluates an advertisement of a kind displayed on the display unit  240  based on the averaged evaluation value. Accordingly, an expression of a viewer&#39;s face is accurately evaluated. 
     According to the first to fourth embodiments, the control unit  23  detects a line of sight to the display unit  240  from an extracted face image, and an expression of the face image is evaluated on condition that the line of sight has been detected. Accordingly, an expression of a viewer&#39;s face can be accurately evaluated. 
     According to the first to fourth embodiments, the control unit  23  detects a line of sight to the display unit  240  from an extracted face image, and evaluates an affirmation level of an advertisement of a kind displayed on the display unit  240  based on a result of detecting the line of sight. Accordingly, an interest of a viewer in content is more accurately grasped. 
     According to the first to fourth embodiments, the control unit  23  evaluates an affirmation level of an advertisement of a kind displayed on the display unit  240  based on time during which a line of sight to the display unit  240  has been detected. Accordingly, an interest of a viewer in content is more accurately grasped. 
     According to the first embodiment, when an advertisement displayed on the display unit  240  has an affirmation level evaluated to have a predetermined affirmative evaluation, the control unit  23  displays the advertisement being currently displayed on the display unit  240  for a longer time. Accordingly, content displayed on the display unit is displayed for a longer time based on a face image of a viewer viewing the content, so that an interest of the viewer is reflected to increase the advertising effect. 
     According to the second embodiment, the control unit  23  determines an order of displaying advertisements on the display unit  240  based on an affirmation level of an advertisement displayed on the display unit  240 . Accordingly, for example, a viewer can view the advertisements in an order according to his/her interest. The interest of the viewer is reflected to increase the advertising effect. 
     According to the third embodiment, when an advertisement displayed on the display unit  240  has an affirmation level evaluated to have a predetermined affirmative evaluation, the control unit  23  switches an advertisement being displayed on the display unit  240  to predetermined detailed advertisements relating to the advertisement. Accordingly, an interest of a viewer is reflected to increase the advertising effect. Further, the display system does not require the viewer to select required content, so that the viewer does not have any trouble, and the advertising effect is increased. 
     According to the fourth embodiment, when an advertisement displayed on the display unit  240  has an affirmation level evaluated to have a predetermined first affirmative evaluation, the control unit  23  switches an advertisement being currently displayed on the display unit  240  to buying information relating to the advertisement. When the advertisement displayed on the display unit  240  has an affirmation level evaluated to have a second affirmative evaluation lower than the first affirmative evaluation, the control unit  23  displays the advertisement being currently displayed on the display unit  240  for a longer time. Accordingly, detailed information relating to content displayed on the display unit  240  is displayed, or the content being displayed is displayed longer, according to a face image of the viewer viewing the content, so that display is performed according to an interest degree of the viewer to increase the advertising effect. 
     It is noted that the embodiments mentioned above are preferable examples of the display device according to the present invention, but the present invention is not limited to the examples. 
     In the embodiments mentioned above, the affirmation level is calculated at each time of imaging, and the display time extension processing or the display change processing is performed according to the calculated affirmation level. However, for example, in order to increase the accuracy of the affirmation level, only the affirmation level may be calculated for a few seconds (e.g. three seconds) after switching of the kind of an advertisement displayed on the display unit  240  without performing the display time extension processing or the display change processing. 
     Further, in the embodiments mentioned above, the expression recognition processing is performed on condition that the line of sight has been recognized. However, the expression recognition processing may be performed regardless of the recognition of the line of sight. 
     Further, in the embodiments mentioned above, the affirmation level is derived from both of the affirmation level based on expression recognition and the affirmation level based on recognition of the line of sight. However, the affirmation level may be derived only from the affirmation level based on the expression recognition. Alternatively, the affirmation level may be derived only from the affirmation level based on recognition of line of sight. 
     Further, in the embodiments mentioned above, for determining the affirmation level, a determination method or a determination reference may be changed according to content of an advertisement. 
     Further, in the embodiments mentioned above, the content of the advertisement displayed on the display unit  240  is changed. However, voice guidance to be output from the sound output unit  33  may be changed, or both of the display and the voice may be changed. 
     Further, in the embodiments mentioned above, content of an advertisement to be displayed may be adaptively changed, according to a result of determining the affirmation level. The main scenario may be adaptively changed in such a manner that, when the “advertisement A-main” image has an affirmation level larger than the threshold th in the main scenario, an advertisement (e.g. “advertisement E-main” image) of a product similar to a product relating to the “advertisement A-main” image is preferentially displayed, after display relating to the “advertisement A-main” image. 
     In the embodiments described above, the expression recognition processing and the recognition of line of sight may be performed together with processing for identifying sex or age to obtain information of a person viewing the advertisement. In addition to these pieces of information, marketing information indicating, for example, what kind of person has an interest in what kind of advertisement may be obtained based on the affirmation level or the display time of advertisement calculated in the display time accumulation processing. 
     Further, in the embodiments mentioned above, the expression recognition or the like is performed based on the picked-up image picked up by the imaging unit  30  to calculate the affirmation level. However, sound recognition may be performed using the sound input unit  34  to calculate the affirmation level, and a method for calculating the affirmation level is not limited to the above-mentioned embodiments. 
     A computer-readable medium storing a program for performing the above-mentioned processing can employ a non-volatile memory such as a flash memory, and a portable recording medium such as a CD-ROM, in addition to a ROM, a hard disk, and the like. A medium providing program data through a predetermined communication line can also employ a carrier wave. 
     Furthermore, a detailed configuration and a detailed operation of each unit constituting the display device can be suitably changed within a range not departing from the spirit of the present invention. 
     The embodiments and modifications of the present invention have been described above, but the spirit and scope of the present invention are not limited to the above-described embodiments and modifications, and the spirit and scope of the invention include the scope of the invention described in the claims and the scope of the equivalents thereof. 
     The invention described in the scope of the claims originally attached to the application will be attached below. The claim numbers are applied as in the scope of the claims originally attached to the application.