Patent Publication Number: US-2016240147-A1

Title: Display control apparatus and control method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation, and claims the benefit, of U.S. patent application Ser. No. 13/323,689, presently pending and filed on Dec. 12, 2011, and claims the benefit of, and priority to, Japanese Patent Application No. 2010-282225 filed Dec. 17, 2010, which applications are hereby incorporated by reference herein in their entireties. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a display control apparatus having a light emission control unit capable of controlling light emission of a plurality of light emitting units independently from each other and a control method thereof. 
     2. Description of the Related Art 
     Conventionally, a liquid crystal display apparatus has a plurality of light emitting units (back light source units) each containing a plurality of light emitting elements arranged in a matrix state on the back side of a display area of a liquid crystal display panel. As the light emitting element for use in the light emitting unit, for example, fluorescent, light emitting diode (LED) and the like are available. The luminance of each light emitting element is controlled by an electric current value to be applied. 
     As discussed in Japanese Patent Application Laid-Open No. 2007-183608, the liquid crystal display apparatus can control independently light emission of each of the plurality of division light emitting units corresponding to a plurality of division areas prepared by dividing the display unit. Such a control is called local dimming control. If the local dimming control is performed when a locally low gradation area and a locally high gradation area are mixed in an image to be displayed, the luminance of each division light emitting unit corresponding to each area can be controlled independently, thereby intensifying a feeling of contrast among displayed colors. 
     As a technology for displaying an image sufficiently and uniformly in the image display area, a technology discussed in Japanese Patent Application Laid-Open No. 2008-83592 is available, the technology proposing turning on the division light emitting units corresponding to an area wider than a specified display area. 
     However, in the local dimming control on the light emitting units, when a user changes the display condition (display position, size of the display area, etc.) of an object image (of the graphical user interface (GUI)) on the display screen by his or her input operation or the like, the processing of the local dimming control cannot follow the change when the change is fast. For example, when the display position or the display area of the object image is changed faster than a predetermined velocity, the processing of the local dimming control cannot follow the change, thereby sometimes causing deterioration of the image such as color unevenness in the changed object image or periphery of the object image. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention provides a display control apparatus having a light emission control unit capable of independently controlling light emission of a plurality of division light emitting units, where the display control apparatus is able to suppress deterioration of image quality, such as color unevenness, even if at least anyone of the display position and the display area of an object image is changed. 
     According to an aspect of the present invention, there is provided display control apparatus that includes a display control unit configured to control to display object image on a display unit, and a light emission control unit configured to independently control light emission of a plurality of division light emitting units corresponding to a plurality of division areas prepared by dividing a display area of the display unit, wherein, when a display area of the object image on the display unit is changed, the light emission control unit controls a plurality of division light emitting units other than the plurality of division light emitting units corresponding to the display area of the object image to emit light at a similar luminance to the luminance of the plurality of division light emitting units corresponding to the display area of the object image before the display area is changed. 
     Further features and aspects of the present invention will become apparent from the following detailed description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments, features, and aspects of the invention and, together with the description, serve to explain the principles of the invention. 
         FIGS. 1A and 1B  are block diagrams illustrating a display control system and a display control apparatus according to a first exemplary embodiment of the present invention. 
         FIGS. 2A and 2B  are schematic diagrams illustrating an image displayed on a display unit and the plurality of division light emitting units in a light emitting unit. 
         FIG. 3  is a flow chart illustrating a processing of the display control apparatus according to the first exemplary embodiment. 
         FIGS. 4A, 4B and 4C  are schematic diagrams illustrating a display image illustrating the display unit and a light emission state of the light emitting unit when the display position of the object image is changed in the first exemplary embodiment. 
         FIGS. 5A, 5B and 5C  are schematic diagrams illustrating a display image on the display unit and a light emission state of the light emitting unit when the display area of the object image is changed in the first exemplary embodiment. 
         FIG. 6  is a block diagram illustrating a display control system according to a second exemplary embodiment. 
         FIG. 7  is a flow chart illustrating a processing of the display control apparatus according to the second exemplary embodiment. 
         FIGS. 8A, 8B and 8C  are schematic diagrams illustrating a display image on the display unit and a light emission state of the light emitting unit when the display position of the object image is changed in the second exemplary embodiment. 
         FIGS. 9A, 9B and 9C  are schematic diagrams illustrating a display image on the display unit and a light emission state of the light emitting unit when the display area of the object image is changed in the second exemplary embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Various exemplary embodiments, features, and aspects of the invention will be described in detail below with reference to the drawings. 
     A first exemplary embodiment will be described below.  FIGS. 1A and 1B  illustrate a display control system and a display control apparatus according to the first exemplary embodiment. The display control system illustrated in  FIG. 1A  includes an image generation apparatus  100  and a display control apparatus  200 . The image generation apparatus  100  includes an image output unit  101  and a coordinate information transmission unit  102 . The image output unit  101  outputs an image stored in a storage unit (not illustrated) contained in the image generation apparatus  100  or an image from an external input apparatus (not illustrated) to the display control apparatus  200 . The coordinate information transmission unit  102  outputs, to the display control apparatus  200 , coordinate information regarding a display area of an object image contained in an image output by the image output unit  101  (hereinafter referred to as coordinate information of the object image). 
     The object image mentioned in this exemplary embodiment refers to a partial image contained in an image constituted of one frame (another image exists in an area other than the partial image). However, the object image mentioned in this exemplary embodiment is not limited to this example, but may be any partial image displayed just in part of the display unit (no video signal exists in an area other than the partial image). Specifically, the object image mentioned in this exemplary embodiment includes a GUI such as a menu screen, a reproduced image of a still image or a moving image, individual image display areas in multi-screen display, windows of personal computer (PC) applications and the like. 
     The display control apparatus  200  includes an image input unit  201 , a display control unit  202 , a display unit  203 , a coordinate information acquisition unit  204 , a change determination unit  205 , a light emission control unit  206 , and a light emitting unit  207 . The image input unit  201  receives an image output by the image output unit  101  of the image generation apparatus  100  and transmits the received image to the display control unit  202 . The display control unit  202  controls to display the image transmitted from the image input unit  201  on the display unit  203 . 
     The coordinate information acquisition unit  204  acquires the coordinate information of the object image output by the coordinate information transmission unit  102  and transmits the coordinate information to the change determination unit  205 . Based on the coordinate information of the object image, the change determination unit  205  determines whether at least anyone of the display position and the display area of the object image has been changed. In other words, the change determination unit  205  determines at least one of whether the display position of the object image has been moved and whether the display area of the object image has been enlarged or reduced. 
     The coordinate information of the object image mentioned here is constituted of a top left coordinate and a bottom right coordinate of the object image in the display image. As illustrated in  FIG. 2A , the coordinate information of the object image is constituted of a top left coordinate (900, 0) and a bottom right coordinate (1500, 600) in a display image of 1920×1080 pixels. The coordinate information of the object image is not limited to this example, but may be a coordinate of the center of the object image and size information (600 in height×600 in width pixels) of the object image. Alternatively, the coordinate information of the object image is at least any one of a coordinate of the center of the object image and size information of the object image. 
     Based on determination by the change determination unit  205 , the light emission control unit  206  controls light emission of the light emitting unit  207 . As illustrated in  FIG. 2B , the light emitting unit  207  is constituted of a plurality of division light emitting units corresponding to a plurality of division areas prepared by dividing the display unit  203  configured to display an image.  FIG. 2B  illustrates a case where the light emitting unit  207  is constituted of 48 (8×6) division light emitting units. The light emission control unit  206  is capable of controlling the luminance of the plurality of division light emitting units independently. 
     The display control apparatus of the present invention may be configured, like a display control apparatus  300  illustrated in  FIG. 1B , to include an image generation unit  301  in place of the image input unit  201  and a coordinate information acquisition unit  302  configured to acquire coordinate information of the object image from an image formed by the image generation unit  301 . Furthermore, the display unit  203 , the light emission control unit  206  and the light emitting unit  207  maybe configured to be a display unit separated from the display control apparatus  200  or  300 . 
       FIG. 3  illustrates a flow chart illustrating a processing of the display control apparatus  200 . In step S 31 , the coordinate information acquisition unit  204  acquires coordinate information of an object image. In step S 32 , the change determination unit  205  determines whether at least any one of the display position and the display area of the object image has been changed, based on the coordinate information of the object image. 
     When in step S 32 , it is determined that the display position of the object image has been changed or the display area of the object image has been changed (YES in step S 32 ), the processing proceeds to step S 33 . In step S 33 , the light emission control unit  206  controls all the plurality of division light emitting units of the light emitting unit  207  to emit light at a similar luminance. If the luminance of the plurality of division light emitting units is within a predetermined range, the luminance is regarded as similar. 
     If, in step S 32 , it is determined that the display position of the object image has not been changed and that the display area of the object image has not been changed (NO in step S 32 ), the processing proceeds to step S 34 . In step S 34 , the light emission control unit  206  independently controls the luminance of the plurality of division light emitting units of the light emitting unit  207  according to the display image. 
     The display image on the display unit and the light emission state of the light emitting unit when the display position of the object image is changed will be described with reference to  FIGS. 4A, 4B and 4C . A control of the light emission control unit  206  will be described below when the display position of the object image is moved (as illustrated on the left of  FIG. 4B ) from a display position of the object image indicated on the left of  FIG. 4A  to a display position of the object image indicated on the left of  FIG. 4C . 
     If, as illustrated in the left figures of  FIGS. 4A and 4C , the display position of the object image is not being changed, the light emission control unit  206  controls light emission of the plurality of division light emitting units of the light emitting unit  207  independently in response to the display image, as illustrated in the right figures of  FIG. 4A and 4C . In the right figures of  FIGS. 4A and 4C , the luminance of the division light emitting units (white area) corresponding to the display area of the object image is controlled to be higher than the division light emitting units (gray area) other than those corresponding to the display area of the object image. By controlling the luminance of the light emitting units independently (by local dimming control), the contrast of the display image can be intensified. 
     In a period when the display position of the object image is being changed as illustrated in the left figure of  FIG. 4B , as illustrated in the right figure of  FIG. 4B , the light emission control unit  206  controls all the division light emitting units contained in the light emitting unit  207  to emit light at an identical luminance. In other words, the light emission control unit  206  refrains from performing the local dimming control on the light emitting unit  207 . In this case, assume that the luminance of each of the division light emitting units is equal to an average luminance of the light emitting unit  207  before the display position of the object image is changed, in other words, the average luminance of the light emitting unit  207  in  FIG. 4A . 
     In the meantime, the luminance of the division light emitting unit in this case is not limited to the aforementioned value, but may be a luminance set preliminarily or an average luminance of the division light emitting units corresponding to the display area of the object image in  FIG. 4A  before the display position is changed. Further, the luminance of the division light emitting unit may be an average luminance of the division light emitting units corresponding to the display area other than the display area of the object image in  FIG. 4A  before the display position is changed. If the size of the display area of the object image is smaller than a predetermined value, setting the entire display area at an average luminance of the division light emitting units corresponding to the display area other than the display area of the object image minimizes a sense of discomfort when a user watches the screen. 
     By controlling the light emitting unit at an identical luminance as described above, deterioration of the image quality such as color unevenness at an end of the object image can be suppressed when the display position of the object image is being changed. 
     Next, a case where the display area of the object image was changed will be described with reference to  FIGS. 5A, 5B and 5C . Control of the light emission control unit  206  will be described in a case where the display area of the object image is enlarged (as illustrated in the left figure of  FIG. 5B ) from the display area of the object image as illustrated in the left figure of  FIG. 5A , up to the display area of the object image as illustrated in the left figure of  FIG. 5C . 
     If, as illustrated in the left figures of  FIG. 5A and 5C , the display area of the object image is not being changed, the light emission control unit  206  controls light emission of the plurality of division light emitting units in the light emitting unit  207  independently, as illustrated in the right figures of  FIG. 5A and 5C . In the right figures of  FIGS. 5A and 5C , the luminance of the division light emitting units corresponding to the display area of the object image is controlled to be higher than that of the division light emitting units other than those corresponding to the display area of the object image. 
     In the case when the display position of the object image is being changed, as illustrated in the left figure of  FIG. 5B , as illustrated in the right figure of  FIG. 5B , the light emission control unit  206  controls all the division light emitting units of the light emitting unit  207  to emit light at an identical luminance. In this case, assume that the luminance of each of the division light emitting units is equal to an average luminance of the light emitting unit  207  before the display area of the object image is changed, in other words, the average luminance of the light emitting unit  207  in  FIG. 5A . However, the luminance of the division light emitting unit in this case is not limited to the aforementioned value, but may be a luminance set preliminarily or an average luminance of the division light emitting units corresponding to the display area of the object image in  FIG. 5A  before the display position is changed. 
     The control of the light emission control unit  206  when the display area of the object image is enlarged has been described above with reference to  FIGS. 5A to 5C . When the display area of the object image is reduced, the light emission control unit  206  controls all the division light emitting units of the light emitting unit  207  to emit light at an identical luminance, as illustrated in  FIG. 5B . 
     In above-discussed step S 32  of  FIG. 3 , the change determination unit  205  may determine whether the display position of the object image has been changed equal to or more than a predetermined value in a unit time or whether the display area of the object image has been changed equal to or more than a predetermined value in a unit time. If a threshold is set for the change in the display position and the display area of the object image and the display position or the display area of the object image is changed equal to or more than the predetermined threshold, the light emission control unit  206  controls all the division light emitting units of the light emitting unit  207  at an identical luminance like in step S 33 . In step S 32 , whether the object image has been changed may be determined based on any one of the change in the display position and the change in the display area of the object image. 
     Although this exemplary embodiment has stated a case where one object image exists in a display image, the same processing as described above is carried out on each object image when a plurality of object images exist in the display image. 
     By controlling the plurality of division light emitting units to emit light at an identical luminance when at least one of the display position and the display area of the object image is changed, the deterioration of the image quality such as color unevenness at an end of the object image can be suppressed. 
     A second exemplary embodiment will be described below.  FIG. 6  illustrates a display control system according to this exemplary embodiment. The display control system illustrated in  FIG. 6  includes an image generation apparatus  100  and a display control apparatus  600 . Description about blocks in which the same operation is executed as in the first exemplary embodiment is omitted while the same reference numerals are assigned to those blocks. Similarly to the display control apparatus of the first exemplary embodiment illustrated in  FIG. 1B , the display control apparatus of the second exemplary embodiment may include the image generation unit  301  in place of the image input unit  201  and the coordinate information acquisition unit  302  configured to acquire coordinate information of the object image from an image generated by the image generation unit  301 . The display unit  203 , the light emission control unit  602  and the light emitting unit  207  may be provided in a display apparatus separated from the display control apparatus  600 . 
     The second exemplary embodiment is different from the first exemplary embodiment in that the display control apparatus  600  has a change direction detection unit  601 . When the change determination unit  205  determines that any one of the display position and the display area of the object image has been changed, the change direction determination unit  601  detects a direction of the change of the object image based on coordinate information of the object image. In other words, when the display position of the object image has been changed, the change direction determination unit  601  detects a direction of the change in the display position of the object image, and, when the display area of the object image has been changed, the change direction determination unit  601  detects a direction of the change in the display area of the object image. The change direction detection unit  601  sends a direction of the change in the display position of a detected object image or a direction of the change in the display area of the object image to the light emission control unit  602 . 
       FIG. 7  illustrates a flow chart of a processing of the display control apparatus  600  according to the second exemplary embodiment. Description of the steps in which the same processing as the flow chart of  FIG. 3  is executed is omitted while the same reference numerals are assigned to those steps. If, in step S 32 , the change determination unit  205  determines that any one of the display position and the display area of the object image has been changed, in step S 71 , the change direction determination unit  601  detects a direction of the change of the object image. If, in step S 32 , the change determination unit  205  determines that the display position of the object image has been changed (YES in step S 32 ), in step S 71 , the change direction detection unit  601  detects the direction of the change in the display position of the object image. If, in step S 32 , the change determination unit  205  determines that the display area of the object image has been changed, in step S 71 , the change direction detection unit  601  detects the direction of the change in the display area of the object image. 
     In step S 72 , the light emission control unit  602  makes division light emitting units in a change direction detected by the change direction detection unit  601  with respect to the division light emitting units corresponding to the display area of the object image before the display position has been changed to emit light at a luminance of the division light emitting units corresponding to the display area of the object image before the display position has been changed. A control of the light emission control unit  602  in this case will be described with reference to  FIGS. 8A, 8B and 8C  and  FIGS. 9A, 9B and 9C .  FIGS. 8A to 8C  illustrate display images and light emission states of the light emitting unit when the display position of the object image is changed in the second exemplary embodiment.  FIGS. 9A to 9C  illustrate the display images and light emission states of the light emitting unit when the display area of the object image is changed in the second exemplary embodiment. 
     If the display position of the object image is not being changed as illustrated in the left figure of  FIG. 8A  and the left figure of  FIG. 8C , the light emission control unit  602  controls light emission of the plurality of division light emitting units of the light emitting unit  207  independently in response to the display image. 
     When the display position of the object image is being changed as illustrated in the left figure of  FIG. 8B , the light emission control unit  602  controls division light emitting units located in a change direction of the object image to emit light at a luminance identical to the division light emitting units corresponding to the display area of the object image before the display position has been changed. In the right figure of  FIG. 8B , the light emission control unit  602  causes 6×4 division light emitting units to emit light at an identical luminance. The 6×4 division light emitting units constituted of 4×4 division light emitting units corresponding to the display area of the object image before the display position has been changed, and 2×4 division light emitting units on the left side (in the change direction) of the display area of the object image before the display position has been changed. In this case, it is permissible to cause 7×4 division light emitting units to emit light at an identical luminance to cause all the division light emitting units in the change direction of the object image to emit light. The 7×4 division light emitting units include 3×4 division light emitting units located on the left side with respect to the display area of the object image before the display position has been changed. 
     When the display area of the object image is not being changed as illustrated in the left figure of  FIG. 9A  and the left figure of  FIG. 9C , the light emission control unit  602  controls light emission of the plurality of division light emitting units of the light emitting unit  207  independently in response to the display image in the same way as the right figure of  FIG. 5A  and the right figure of  FIG. 5C  of the first exemplary embodiment. 
     In the right figure of  FIG. 9B , the light emission control unit  602  causes 5×4 division light emitting units to emit light at an identical luminance. The 5×4 division light emitting units are constituted of 4×4 division light emitting units corresponding to the display area of the object image before the display area has been changed, and 1×4 division light emitting units on the left side (in the change direction) with respect to the display area of the object image before the display area has been changed. In addition to the division light emitting units corresponding to the display area of the object image before the display area has been changed, the quantity and positions of the division light emitting units located in the change direction which the light emission control unit  602  causes to emit light may be determined in response to an amount of the change of the object image in a unit time or may be set preliminarily. When the object image is changed in the change direction detected by the change direction detection unit  601 , it is advantageous that the division light emitting units which the light emission control unit  602  causes to emit light at a luminance identical to the division light emitting units corresponding to the display area of the object image before the display area has been changed are determined so that the luminance of the display area of the object image is identical to the luminance before the display area has been changed. 
     When the object image is changed, by causing the division light emitting units in the change direction with respect to the display area of the object image before the display area has been changed to emit light at a luminance identical to the division light emitting units corresponding to the display area of the object image, deterioration of the image quality such as color unevenness of the object image can be suppressed. Even when the local dimming control cannot be performed because of a large change in size of the object image, the division light emitting units in the change direction can be caused to emit light at a luminance identical to the division light emitting units corresponding to the display area of the object image by detecting the direction of the change. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It will of course be understood that this invention has been described above byway of example only, and that modifications of detail can be made within the scope of this invention.