Patent Publication Number: US-2012038829-A1

Title: Display apparatus

Description:
TECHNICAL FIELD 
     The present invention is related to display apparatuses for providing viewers with a video with little afterglow. 
     BACKGROUND OF THE INVENTION 
     Display apparatuses configured to provide viewers with a video, which is stereoscopically perceived (stereoscopic video), has been developed as a result of recent progresses in the video technologies. A display apparatus typically displays a video including a left frame image, which is viewed by the left eye, and a right frame image, which is viewed by the right eye. The display apparatus transmits a synchronization signal in synchronism with display of the video frame images. A user wears a dedicated eyeglass device to view the stereoscopic video. The eyeglass device executes stereoscopic vision assistance to assist in viewing the video, in response to the synchronization signal transmitted from the display apparatus. If the display apparatus displays the left frame image, the eyeglass device reduces a light amount reaching the right eye of the viewer whereas the eyeglass device increases a light amount reaching the left eye of the viewer. If the display apparatus displays the right frame image, the eyeglass device reduces the light amount reaching the left eye of the viewer whereas the eyeglass device increases the light amount reaching the right eye of the viewer. As a result, the viewer stereoscopically perceives the video displayed by the display apparatus. 
     Like a standard two-dimensional video, the left and right frame images are depicted by means of the three primary colors such as red, green and blue. Patent Documents 1 and 2 disclose a display apparatus configured to display frame images with yellow, which is the opposite color of blue, in addition to the three primary colors that are red, green and blue. The display apparatus described in Patent Documents 1 and 2 achieves improved color reproducibility by means of the four colors that are red, green, blue and yellow. 
     A plasma display apparatus, which causes plasma emission of pixels to display a frame image, in particular faces problems about afterglow (cross talk). If the plasma display apparatus alternately displays left and right frame images, in particular, the afterglow of the plasma display adversely affects the view of a stereoscopic video. For example, while the plasma display apparatus displays the right frame image, the viewer may perceive afterglow from the left frame image, which is displayed before the right frame image. Likewise, if the plasma display apparatus displays the left frame image, the viewer may perceive afterglow from the right frame image, which is displayed before the left frame image. As a result, it becomes less likely that the viewer comfortably views the stereoscopic video. 
     Technologies disclosed in Patent Documents 1 and 2 do not address the problem of the afterglow of a display apparatus employing self-emitting element such as the aforementioned plasma display apparatus. Therefore, there have not been technologies for solving the problem of the aforementioned afterglow. 
     Patent Document 1: JP 2001-209047 A 
     Patent Document 2: WO2007/148519 
     DISCLOSURE OF THE INVENTION 
     An object of the present invention is to provide a display apparatus which may provide a video with little afterglow. 
     A display apparatus according to one aspect of the present invention includes: an input port to which a video signal is input, the video signal representing a display color with a first luminosity value corresponding to a red hue, a second luminosity value corresponding to a green hue, and a third luminosity value corresponding to a blue hue; a display portion including a pixel having a red sub-pixel which causes plasma emission in the red hue, a green sub-pixel which causes plasma emission in the green hue, a blue sub-pixel which causes plasma emission in the blue hue, and a yellow sub-pixel which causes plasma emission in a yellow hue; and a converter configured to convert the video signal into a conversion signal so that the red, green, blue and yellow sub-pixels emit light on the display portion to display a display color which corresponds to the represented display color by the video signal, wherein the conversion signal output by the converter includes at least one of a red conversion signal to cause the plasma emission of the red sub-pixel at a first converted luminosity value that is lower than the first luminosity value and a green conversion signal to cause the plasma emission of the green sub-pixel at a second converted luminosity value that is lower than the second luminosity value, and a yellow conversion signal to cause the plasma emission of the yellow sub-pixel, the plasma emission by the yellow sub-pixel results in a shorter afterglow time than resultant afterglow times from the plasma emissions by the red and green sub-pixels, the red sub-pixel causes the plasma emission at the first converted luminosity value, and the green sub-pixel causes the plasma emission at the second converted luminosity value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic block diagram showing a hardware configuration of a display apparatus according to one embodiment. 
         FIG. 1B  is a schematic block diagram showing a functional configuration of a display apparatus according to one embodiment. 
         FIG. 2  is a schematic view showing a configuration of a video system which includes the display apparatus shown in  FIGS. 1A and 1B . 
         FIG. 3  is a schematic view showing a pixel configuration of a display portion of the display apparatus shown in  FIGS. 1A and 1B . 
         FIG. 4  is a schematic cross-sectional view showing the display portion of the display apparatus shown in  FIGS. 1A and 1B . 
         FIG. 5  is a schematic graph showing afterglow characteristics of fluorescent materials of the display portion shown in  FIG. 4 . 
         FIG. 6  is a schematic view showing effects of the afterglow of the fluorescent material on video view. 
         FIG. 7  is a schematic view showing generation of a conversion signal by a converter of the display apparatus shown in  FIGS. 1A and 1B . 
         FIG. 8  is a table showing results obtained according to the conversion method shown in  FIG. 7 . 
         FIG. 9  is a schematic chromaticity diagram showing results obtained according to the conversion method shown in  FIG. 7 . 
         FIG. 10  is a schematic view showing another method about the generation of the conversion signal by the converter of the display apparatus shown in  FIGS. 1A and 1B . 
         FIG. 11  is a schematic view showing yet another method about the generation of the conversion signal by the converter of the display apparatus shown in  FIGS. 1A and 1B . 
         FIG. 12  is a schematic view showing a method for determining luminosity value by means of the lookup tables shown in  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A display apparatus according to one embodiment is described hereinafter with reference to the accompanying drawings. It should be noted that configurations, arrangements, shapes and so on depicted in the drawings as well as descriptions relating to the drawings are provided merely for facilitating to understand principles of the display apparatus. Therefore the principles of the display apparatus are in no way limited to these. 
     (Configuration of Display Apparatus) 
       FIGS. 1A and 1B  are schematic block diagrams showing a configuration of the display apparatus.  FIG. 1A  is a schematic block diagram showing a hardware configuration of the display apparatus.  FIG. 1B  is a schematic block diagram showing a functional configuration of the display apparatus. The display apparatus is described with reference to  FIGS. 1A and 1B . 
     As shown in  FIG. 1A , the display apparatus  100  includes a decoding IC  110 , a video signal processing IC  120 , a transmission control IC  130 , a CPU  140 , a memory  150 , a clock  160 , a drive circuit  190 , a display panel  170  and a transmission device  180 . 
     An encoded video signal is input to the decoding IC  110  of the display apparatus  100 . The decoding IC  110  decodes the video signal to output video data in a predetermined format. Various methods such as MPEG (Motion Picture Experts Group)-2, MPEG-4 and H264 may be used to decode the video. 
     The decoded video data is used as a video signal which represents display colors of pixels of the display panel  170  by means of a first luminosity value corresponding to a red hue, a second luminosity value corresponding to a green hue and a third luminosity value corresponding to a blue hue. 
     The video signal processing IC  120  performs signal processes in relation to stereoscopic video display. The video signal processing IC  120  processes the video signal to display the video data from the decoding IC  110  as a stereoscopic video. The video signal processing IC  120  detects a left frame image viewed by the left eye and a right frame image viewed by the right eye from the video data decoded by the decoding IC  110 . The detected left and right frame images are alternately displayed on the display panel  170 , which is driven by the drive circuit  190 . Alternatively, the left and right frame images may be automatically generated from the video data output by the decoding IC  110 . The video signal processing IC  120  alternately outputs the generated left and right frame images to the display panel  170  via the drive circuit  190 . After the signal processes relating to the stereoscopic video display, the video signal processing IC  120  generates an output signal, which conforms to a signal input method of the display panel  170 . 
     The video signal processing IC  120  converts the decoded video signal into a conversion signal. The conversion signal is generated to display a display color, which the decoded video data defines for each pixel, by means of a red hue, a green hue, a blue hue and a yellow hue. The conversion signal is output to the drive circuit  190 . 
     It should be noted that the video signal processing IC  120  may execute other processes than the aforementioned processes. For example, the video signal processing IC  120  may interpolate images between video frames of the video data generated by the decoding IC  110  in accordance with characteristics of the display panel  170  to increase a frame rate of the video. 
     The transmission control IC  130  generates a synchronization signal in synchronous with the left and right frame images generated by the video signal processing IC  120 . The transmission control IC  130  then outputs the generated synchronization signal to the transmission device  180 . 
     The CPU  140  controls constitutional units such as the decoding IC  110  and the video signal processing IC  120 , which constitute the display apparatus  100 , for example, in accordance with programs recorded in the memory  150  and an external input (not shown). Thus, the CPU  140  may entirely control the display apparatus  100 . 
     The memory  150  is used as a region for recording the programs executed by the CPU  140  and temporary data generated during execution of the programs. A volatile RAM (Random Access Memory) or a non-volatile ROM (Read Only Memory) may be used as the memory  150 . 
     The clock  160  supplies a clock signal to the CPU  140  and other constitutional components. The clock signal serves as an operational reference of each IC. 
     The video signal processed by the video signal processing IC  120  is input to the drive circuit  190 . The drive circuit  190  drives the display panel  170  in response to the input video signal. In this embodiment, the aforementioned conversion signal is input as the video signal. As described hereinafter, each pixel of the display panel  170  includes sub-pixels, which cause plasma emissions in a red hue, a green hue, a blue hue and a yellow hue, respectively. Therefore, the drive circuit  190  drives the display panel  170  in response to the conversion signal to emit light from the sub-pixel of the red hue (to be referred hereinafter to as the red sub-pixel), the sub-pixel of the green hue (to be referred hereinafter to as the green sub-pixel), the sub-pixel of the blue hue (to be referred hereinafter to as the blue sub-pixel), and the sub-pixel of the yellow hue (to be referred hereinafter to as the yellow sub-pixel), respectively. 
     The video signal (the left and right frame images) output from the video signal processing IC  120  is displayed on the display panel  170  driven by the drive circuit  190 . As described hereinafter, a viewer wearing an eyeglass device stereoscopically perceives the frame images displayed on the display panel  170  by means of stereoscopic vision assistance performed by the eyeglass device. In this embodiment, a PDP (Plasma Display Panel) may be preferably used as the display panel  170 . 
     The transmission device  180  outputs the synchronization signal to the eyeglass device under control of the transmission control IC  130 . As described hereinafter, the eyeglass device worn by the viewer executes the stereoscopic vision assistance in response to the synchronization signal so that the video displayed on the display panel  170  is stereoscopically perceived. For example, an infrared light emitter, an RF transmitter or another device configured to transmit the synchronization signal may be preferably used as the transmission device  180 . 
     As shown in  FIG. 1B , the display apparatus  100  includes a decoder  210 , an L/R signal separator  221 , a stereoscopic signal processor  222 , a converter  224 , a driver  290 , a display portion  270 , a synchronization signal generator  223 , a transmission controller  230  and a transmitter  280 . 
     The decoder  210  corresponds to the decoding IC  110  described with reference to  FIG. 1A . The encoded video signal is input to the decoder  210 . 
     The L/R signal separator  221  generates or separates a left video signal and a right video signal (the left and right frame images) from the video signal decoded by the decoder  210 . 
     The stereoscopic signal processor  222  adjusts the left and right video signals separated by the L/R signal separator  221  in accordance with characteristics of the display portion  270  to display a video, which is viewed through the eyeglass device. For example, the stereoscopic signal processor  222  executes processes to adjust parallax between the left and right frame images in accordance with a size of a display surface of the display portion  270 . It should be noted that the display portion  270  corresponds to the display panel  170  depicted in  FIG. 1A . In this embodiment, the stereoscopic signal processor  222 , the L/R signal separator  221  and/or the decoder  210  are used as an input port to which the video signal is input. The input video signal represents the display color of each pixel of the display panel  170  by means of the first to third luminosity values, which correspond to the red, green and blue hues, respectively. 
     The synchronization signal generator  223  generates synchronization signals in synchronism or correspondence with the left and right frame images, which are generated by the L/R signal separator  221 . Meanwhile, types (for example, waveforms) and generation timings of the synchronization signals are adjusted in accordance with characteristics of the display portion  270 . 
     The converter  224  converts the video signal processed by the stereoscopic signal processor  222  into a conversion signal. As described above, the conversion signal is generated to display a display color, which corresponds to the display color that the decoded video data defines for each pixel, by means of the red, green, blue and yellow hues. The conversion signal is output to the driver  290 . The converter  224  may include a storage portion  250 . The converter  224  may generate the conversion signal by means of a lookup table (LUT) stored in the storage portion  250 . 
     The L/R signal separator  221 , stereoscopic signal processor  222 , synchronization signal generator  223  and converter  224  correspond to the video signal processing IC  120  of the hardware configuration described with reference to  FIG. 1A . The storage portion  250  corresponds to the memory  150  of  FIG. 1A . 
     The video signal, which is processed by the stereoscopic signal processor  222  and the converter  224 , is input to the driver  290 . The driver  290  drives the display portion  270  in response to the input video signal. As described above, the display portion  270  corresponds to the display panel  170  shown in  FIG. 1A . Each pixel of the display portion  270  includes the red, green, blue and yellow sub-pixels. The driver  290  drives the display portion  270  in response to the conversion signal converted by the converter  224  to emit light from the red, green, blue and yellow sub-pixels, respectively. Thus, each pixel emits light in the display color, which is defined by the video signal output from the stereoscopic signal processor  222 . The driver  290  corresponds to the drive circuit  190  shown in  FIG. 1A . 
     The transmitter  280  transmits the synchronization signal generated by the synchronization signal generator  223  to the eyeglass device under control of the transmission controller  230 . The transmitter  280  corresponds to the transmission device  180  shown in  FIG. 1A . 
     The transmission controller  230  controls a data volume and a transmission interval of the synchronization signal in transmission. The transmission controller  230  corresponds to the transmission control IC  130  shown in  FIG. 1A . 
     (Video System with Display Apparatus) 
       FIG. 2  schematically shows a video system into which the display apparatus  100  is incorporated. The video system with the display apparatus  100  is described with reference to  FIGS. 1A to 2 . 
     The video system  300  includes the display apparatus  100 , which displays a video, and the eyeglass device  400 , which performs the stereoscopic vision assistance that allows a viewer to stereoscopically perceive the video. As described above, the left and right frame images viewed by the left and right eyes are displayed on the display panel  170 . In this embodiment, the left and right frame images are alternately displayed on the display panel  170 . 
     The eyeglass device  400  executes the stereoscopic vision assistance so that the viewer views the left and right frame images with the left and right eyes, respectively. As a result, the viewer three-dimensionally (stereoscopically) perceives the video displayed on the display panel  170 . If the video is stereoscopically perceived, objects in the left and right frame images (images of objects depicted in the left and right frame images) are perceived so that the objects come out of or into the flat surface of the display panel  170 . 
     The transmission device  180  is situated on an upper edge of a housing  101 , which surrounds the periphery of the display panel  170 . As described above, the transmission device  180  transmits the synchronization signal in synchronism with the display of the left and right frame images on the display panel  170 . 
     The synchronization signal from the transmission device  180  is received by the eyeglass device  400 . The eyeglass device  400  executes the aforementioned stereoscopic vision assistance in response to the received synchronization signal. As a result, the viewer may view the left and right frame images displayed by the display panel  170  with the left and right eyes, respectively. 
     The eyeglass device  400  in general looks like vision correction eyeglasses. The eyeglass device  400  comprises an optical filter portion  410 , which includes a left filter  411  situated in front of the left eye of the viewer wearing the eyeglass device  400  and a right filter  412  situated in front of the right eye. The left and right filters  411 ,  412  are optical elements configured to adjust transmitted light amounts to the left and right eyes of the viewer, respectively. Accordingly, shutter elements (for example, liquid crystal shutters), which open and close light paths to the left and right eyes of the viewer, respectively, deflection elements (for example, liquid crystal filters), which deflect the transmitted light to the left and right eyes of the viewer, or other optical elements configured to adjust the light amounts may be suitably used as the left and right filters  411 ,  412 . 
     While the display panel  170  displays the left frame image, the left filter  411  permits light transmission to the left eye of the viewer whereas the right filter  412  suppresses light transmission to the right eye of the viewer. As a result, the viewer may view the left frame image with the left eye. While the display panel  170  displays the right frame image, the right filter  412  allows the light transmission to the right eye of the viewer whereas the left filter  411  suppresses the light transmission to the left eye of the viewer. As a result, the viewer may view the right frame image with the right eye. Under the stereoscopic vision assistance, the viewer may stereoscopically perceive the video displayed by the display panel  170 . 
     The eyeglass device  400  includes a reception device  420  situated between the left and right filters  411 ,  412 . The reception device  420  is used as a receiver configured to receive the synchronization signal, which is transmitted in synchronism with the display of the frame images of the video. The synchronization between the display of the frame images of the video and the stereoscopic vision assistance of the optical filter portion  410  is achieved if the reception device  420  receives the synchronization signal from the transmission device  180 . If an infrared light emitter is used as the transmission device  180 , an infrared light receiver is suitably used as the reception device  420 . If an RF transmitter is used as the transmission device  180 , an RF receiver is suitably used as the reception device  420 . Alternatively, another element configured to receive the synchronization signal transmitted by the transmission device  180  may be used as the reception device  420 . 
     (Configuration of Display Panel) 
       FIG. 3  schematically shows a pixel array in a region R shown in  FIG. 2 . It should be note that the region R is a given region in the display panel  170 . The pixel array in the region R is described with reference to  FIGS. 2 and 3 . 
     Pixels  171  are arranged in matrix form on the display panel  170 .  FIG. 3  shows twelve pixels  171  arranged from the (M−1) to (M+2) columns and from the (N−1) to (N+1) rows. Each pixel  171  includes a red sub-pixel  172 , a green sub-pixel  173 , a yellow sub-pixel  174  and a blue sub-pixel  175 . In this embodiment, the red, yellow, blue and green sub-pixels  172 ,  174 ,  175  and  173 , which are aligned in the row direction, are vertically elongated rectangular shape, respectively, of which surface areas are substantially equivalent to each other. The yellow sub-pixel  174  is situated between the red sub-pixel  172  at one end of the pixel  171  and the blue sub-pixel  175 . The blue sub-pixel  175  is situated between the yellow sub-pixel  174  and the green sub-pixel  173  at the other end of the pixel  171 . If the red or blue sub-pixel  172 ,  175 , which has a low spectral luminous efficiency, is situated between the yellow and green sub-pixels  174 ,  173 , which have a higher spectral luminous efficiency, the pixel  171  may preferably emit light. 
       FIG. 4  is a schematic sectional view of the pixel  171 . The pixel  171  of the display panel  171  is described with reference to  FIGS. 1A ,  1 B,  3  and  4 . 
     The display panel  170  includes a front substrate  176  made of glass, and a back substrate  177 , which is made of glass and opposite to the front substrate  176 . A discharge space  178  is defined between the front and back substrates  176 ,  177 . The discharge space  178  is filled with gas such as neon or xenon. With discharge in the discharge space  178 , the gas emits ultraviolet rays. 
     A dielectric layer  179  and a protective layer  181  are formed on a surface of the front substrate  176 , which faces the back substrate  177 . Scanning electrodes  182  and sustain electrodes  183  are situated between the dielectric layer  179  and the front substrate  176 . A pair of the scanning electrodes  182  and a pair of the sustain electrodes  183  are alternately arranged. A light absorption layer  184  formed from a black material is situated between the pairs of scanning electrodes  182  and between the pairs of sustain electrodes  183 , respectively. 
     A data electrode  185  is situated on the back substrate  177  facing the front substrate  176 . The data electrode  185  extends in a substantially orthogonal direction to the extension direction of the scanning electrodes  182  and the sustain electrodes  183 . A dielectric layer  196  is formed on the data electrode  185 . 
     Partition walls  186  defining the red, yellow, blue and green sub-pixels  172 ,  174 ,  175  and  173 , respectively, shown in  FIG. 3  are situated on the back substrate  177 . A fluorescent material layer  188  is formed in a space  187  defined by the partition walls  186 . The fluorescent material layer  188  in the space  187  corresponding to the red sub-pixel  172 , which is described with reference to  FIG. 3 , is formed of a red fluorescent material  189 . The fluorescent material layer  188  in the space  187  corresponding to the green sub-pixel  173  is formed of a green fluorescent material  191 . The fluorescent material layer  188  in the space  187  corresponding to the yellow sub-pixel  174  is formed of a yellow fluorescent material  192 . The fluorescent material layer  188  in the space  187  corresponding to the blue sub-pixel  175  is formed of a blue fluorescent material  193 . A YVP fluorescent material ((Y, Eu) (PVO 4 )) may be exemplified as the red fluorescent material  189 . A ZSM fluorescent material ((Zn, Mn) 2  MgSiO 4 ) may be exemplified as the green fluorescent material  191 . A YAG fluorescent material ((Y 3 Al 5 O 12 : Ce3+) may be exemplified as the yellow fluorescent material  192 . A BAM fluorescent material ((Ba, Eu) MgAl 10 O 17 ) may be exemplified as the blue fluorescent material  193 . 
     A gap  194  is defined between the spaces  187 . A priming electrode  195  is situated on the dielectric layer  196 , which faces the scanning electrodes  182 . The priming electrode  195  extends in a substantially orthogonal direction to the data electrode  185 . The priming electrode  195  performs priming discharge in the gap  194  defined between the priming electrode  195  and the scanning electrodes  182 . 
     As described with reference to  FIGS. 1A and 1B , the drive circuit  190  drives the display panel  170  to cause the discharge in the space  187  in response to the conversion signal. As a result, the gas in the space  187  is excited to emit excited ultraviolet rays. The red, green, yellow and blue fluorescent materials  189 ,  191 ,  192  and  193  are subjected to plasma emission by the excited ultraviolet rays. 
     (Afterglow Characteristics) 
       FIG. 5  is a graph showing afterglow characteristics of the red, green, yellow and blue fluorescent materials  189 ,  191 ,  192  and  193 . The abscissa of the graph shows an elapsed time after halt of the excited ultraviolet rays. The ordinate of the graph shows a time response of emission intensity from the fluorescent material after the halt of the excited ultraviolet rays. The afterglow characteristics of the red, green, yellow and blue fluorescent materials  189 ,  191 ,  192  and  193  are described with reference to  FIGS. 3 and 5 . 
     As shown in  FIG. 5 , the emission intensities of the blue fluorescent material (BAM fluorescent material)  193  and the yellow fluorescent material (YAG fluorescent material)  192  fall to or below 1/10 within one millisecond after the halt of the excited ultraviolet rays. On the other hand, it takes substantially four milliseconds for the emission intensity of the red fluorescent material (YVP fluorescent material)  189  to fall to or below 1/10 after the halt of the excited ultraviolet rays. It takes substantially five seconds for the emission intensity of the green fluorescent material (ZSM fluorescent material)  191  to fall to or below 1/10 after the halt of the excited ultraviolet rays. 
     In this embodiment, the term “a long afterglow time” or similar terms means that a long time is required for the emission intensity to fall to a predetermined value after the halt of the excited ultraviolet rays. The term “a short afterglow time” or similar terms means that a short time is required for the emission intensity to fall to the predetermined value after the halt of the excited ultraviolet rays. It is figured out from  FIG. 5  that the blue and yellow fluorescent materials  193 ,  192  have a shorter afterglow time than the red and green fluorescent materials  189 ,  191 . 
       FIG. 6  is a schematic timing chart showing effects of the afterglow time on the video viewed by the viewer. A left diagram in  FIG. 6  is a timing chart under a short afterglow time. A right diagram in  FIG. 6  is a timing chart under a long afterglow time. Section (a) in  FIG. 6  shows the frame image displayed by the display portion  270 . Section (b) in  FIG. 6  shows operation of the optical filter portion  410  of the eyeglass device  400 . Section (c) in  FIG. 6  shows the video viewed by the viewer. The effects of the afterglow time on the video perceived by the viewer are described with reference to  FIGS. 1A to 2  as well as  FIGS. 5 and 6 . 
     As shown in Section (a) of  FIG. 6 , left and right frame images  510 ,  520  are alternately displayed by the display portion  270 . As shown in Section (b) of  FIG. 6 , the left filter  411  of the optical filter portion  410  increases the light amount reaching the left eye of the viewer in synchronization with the display of the left frame image  510  whereas the left filter  411  reduces the light amount reaching the left eye of the viewer during the display of the right frame image  520 . The right filter  412  of the optical filter portion  410  increases the light amount reaching the right eye of the viewer in synchronization with the display of the right frame image  520  whereas the right filter  412  reduces the light amount reaching the right eye of the viewer during the display of the left frame image  510 . 
     As shown in Section (a) of  FIG. 6 , if the afterglow time is short, there is no temporal overlap between the displays of the left and right frame images  510 ,  520 . If the afterglow time is long, on the other hand, there is the temporal overlap between the displays of the left and right frame images  510 ,  520 . Accordingly, if the afterglow time is long, the afterglow from the right frame image  520  is perceived by the left eye and the afterglow from the left frame image  510  is perceived by the right eye. As a result, the viewer may not comfortably enjoy viewing the stereoscopic video. If the afterglow time is short, on the other hand, the left frame image  510  may be viewed without perception of the afterglow from the right frame image by the left eye. The right frame image  520  may be viewed without perception of the afterglow from the left frame image  510  by the right eye. Thus, if the afterglow time is short, the viewer may comfortably enjoy viewing the stereoscopic video. 
     (Generation of Conversion Signal) 
       FIG. 7  schematically shows generation of the conversion signal by the converter  224 . The generation of the conversion signal by the converter  224  is described with reference to  FIGS. 1A ,  1 B,  3 ,  4  and  7 . 
     As described with reference to  FIGS. 1A and 1B , the video signal is output from the stereoscopic signal processor  222  to the converter  224 . The video signal from the stereoscopic signal processor  222  represents the display color of each pixel  171  by the first to third luminosity values corresponding to the red, green and blue hues, respectively. 
     In  FIG. 7 , the first luminosity value corresponding to the red hue is represented by the symbol “x”. The second luminosity value corresponding to the green hue is represented by the symbol “y”. As shown in  FIG. 7 , the converter  224  determines smaller one (represented in  FIG. 7  by the symbol “z”) of the first luminosity value “x”, which corresponds to the red hue and the second luminosity value “y”, which corresponds to the green hue, as a third converted luminosity value corresponding to the yellow sub-pixel  174 . The converter  224  then outputs a yellow conversion signal to cause plasma emission of the yellow fluorescent material  192  of the yellow sub-pixel  174  at the determined third converted luminosity value. 
     The converter  224  also determines a difference value between the first luminosity value “x” and the smaller one “z” of the first luminosity value “x”, which corresponds to the red hue, and the second luminosity value “y”, which corresponds to the green hue, as a first converted luminosity value corresponding to the red sub-pixel  172 . The converter  224  then outputs a red conversion signal to cause plasma emission of the red fluorescent material  189  of the red sub-pixel  172  at the determined first converted luminosity value. 
     Likewise, the converter  224  determines a difference value between the second luminosity value “y” and the smaller one “z” of the first luminosity value “x”, which corresponds to the red hue, and the second luminosity value “y”, which corresponds to the green hue, as a second converted luminosity value corresponding to the green sub-pixel  173 . The converter  224  then outputs a green conversion signal to cause plasma emission of the green fluorescent material  191  of the green sub-pixel  173  at the determined second converted luminosity value. 
     In this embodiment, the third luminosity value corresponding to the blue hue in the video signal from the stereoscopic signal processor  222  is used as the fourth converted luminosity value corresponding to the blue sub-pixel  175  without being subjected to the conversion process. Therefore, the converter  224  outputs a blue conversion signal to cause plasma emission of the blue fluorescent material  193  of the blue sub-pixel  175  at the fourth converted luminosity value, which is equal to the third luminosity value. 
       FIG. 8  shows results of the conversion process shown in  FIG. 7 . The numerical values shown in  FIG. 8  represent the luminosity value of each hue on a  256  gray scale, respectively. It should be noted that  FIG. 8  shows conversion results from the specific hues, but the conversion processes shown in  FIG. 7  may be suitably applied to other hues. The conversion signal generation by the converter  224  is described with reference to  FIGS. 1A ,  1 B,  3 ,  5 ,  7  and  8 . 
     For example, if the video signal from the stereoscopic signal processor  222  represents the display color of the pixel  171  in a gray hue, the video signal allocates a luminosity value “127” to the first luminosity value corresponding to the red hue, the second luminosity value corresponding to the green hue, and the third luminosity value corresponding to the blue hue, respectively. As described with reference to  FIG. 7 , the converter  224  compares the value allocated to the first luminosity value “x” with the value allocated to the second luminosity value “y”. In the case of the gray hue, the first and second luminosity values are equal, so that the converter  224  allocates a value of “127” to the third converted luminosity value corresponding to the yellow sub-pixel  174 . The converter  224  then outputs the yellow conversion signal. As a result, the yellow sub-pixel  174  performs plasma emission at the luminosity value of “127”. 
     Meanwhile, by means of the difference calculation described with reference to  FIG. 7 , the converter  224  allocates a value of “0” to both the first and second converted luminosity values, which correspond to the red and green sub-pixel  172 ,  173 , respectively, so that the converter  224  outputs the red and green conversion signals. The converter  224  allocates a value of “127”, which is the value allocated to the blue hue by the video signal from the stereoscopic signal processor  222 , to the fourth converted luminosity value corresponding to the blue sub-pixel  175 . The converter  224  then outputs the blue conversion signal. 
     Accordingly, in the conversion process described with reference to  FIG. 7 , the first converted luminosity value corresponding to the red sub-pixel  172 , of which the afterglow time is relatively long, is set to be lower than the first luminosity value corresponding to the red hue in the video signal. The second converted luminosity value of the green sub-pixel  173 , of which the afterglow time is relatively long, is also set to be lower than the second luminosity value corresponding to the green hue in the video signal. As a result, the afterglow time of the pixel  171  becomes shorter than an afterglow time under no conversion process. 
     If the video signal from the stereoscopic signal processor  222  represents black, red, magenta, blue, cyan and green hues out of the “pixel colors” shown in  FIG. 8  as the display color, a value of “0” is allocated to at least one of the first and second luminosity values, which correspond to the red and green hues, respectively. In this case, the value of the third converted luminosity value corresponding to the yellow sub-pixel  174  becomes “0”. Therefore, according to the conversion process described with reference to  FIG. 7 , the yellow conversion signal is output if a value of “0” is allocated neither the first luminosity value corresponding to the red hue nor the second luminosity value corresponding to the green hue. 
       FIG. 9  is a chromaticity diagram showing effects of the conversion process described with reference to  FIG. 7 . A curve in  FIG. 9  is a curve of pure spectral colors. A triangular region in  FIG. 9  shows display colors which can be displayed by the display portion  270 . Vertices of the triangular region correspond to color coordinates of the red fluorescent material (YVP fluorescent material)  189 , the green fluorescent material (ZSM fluorescent material)  191  and the blue fluorescent material (BAM fluorescent material)  193 , respectively. The color coordinate point of the yellow fluorescent material (YAG fluorescent material)  192  is set on a straight line, which connects the color coordinate point of the red fluorescent material  189  to the color coordinate point of the green fluorescent material  191 . 
     A triangular region C shown in  FIG. 9  is schematically divided into three triangular regions C 1 , C 2 , C 3 . A hue in the triangular region C 1 , of which vertices are defined by a substantially intermediate coordinate point P 1  positioned between the color coordinate points of the yellow and green fluorescent materials  192 ,  191  and the color coordinate points of the blue and green fluorescent materials  193 ,  191 , is displayed by light emissions from the green, blue and yellow fluorescent materials  191 ,  193  and  192 . A hue in the triangular region C 3 , of which vertices are defined by a substantially intermediate coordinate point P 2  positioned between the coordinate point P 1  and the color coordinate point of the red fluorescent material  189 , the color coordinate points of the red and blue fluorescent materials  189 ,  193 , is displayed by light emissions from the red, blue and yellow fluorescent materials  189 ,  193  and  192 . A hue in the triangular region C 2 , of which vertices are defined by the coordinate points P 1 , P 2  and the color coordinate point of the blue fluorescent material  193  is displayed by light emissions from the blue and yellow fluorescent materials  193 ,  192 . 
     Therefore, according to the conversion process described with reference to  FIG. 7 , a large number of hues are displayed by the light emissions from the blue and yellow fluorescent materials  193 ,  192 . If the hue of the triangular region C 1  is displayed, the first converted luminosity value corresponding to the red sub-pixel  172  is preferably reduced. If the hue of the triangular region C 3  is displayed, the second converted luminosity value corresponding to the green sub-pixel  173  is also preferably reduced. 
       FIG. 10  schematically shows another method for generating the conversion signal by the converter  224 . The conversion signal generation by the converter  224  is described with reference to  FIGS. 1A ,  1 B,  3 ,  4 ,  8  and  10 . 
     As described above with reference to  FIGS. 1A and 1B , the video signal is output from the stereoscopic signal processor  222  to the converter  224 . The video signal from the stereoscopic signal processor  222  represents the display color of each pixel  171  by the first to third luminosity values, which correspond to the red, green and blue hues, respectively. 
     In this embodiment, light emission of the red sub-pixel  172  at a predetermined first emission luminosity value (represented by the symbol “α” in  FIG. 10 ) and light emission of the green sub-pixel  173  at a predetermined second emission luminosity value (represented by the symbol “β” in  FIG. 10 ) results in a substantially equivalent hue and luminosity value to light emission at a third emission luminosity value “α+β”, which is obtained as a sum of the first and second emission luminosity values “α” and “β”. 
     The converter  224  divides the first luminosity value corresponding to the red hue, which is defined by the video signal from the stereoscopic signal processor  222 , by the first emission luminosity value “α” to calculate a value “x” shown in  FIG. 10 . The converter  224  also divides the second luminosity value corresponding to the green hue, which is defined by the video signal from the stereoscopic signal processor  222 , by the second emission luminosity value “β” to calculate a value “y” shown in  FIG. 10 . The converter  224  then determines smaller one of the values “x” and “y” as a value “z”. The converter  224  multiplies the third emission luminosity value “α+β” by the determined value “z”, so that the converter  224  then sets the resultant value from the multiplication as the third converted luminosity value corresponding to the yellow sub-pixel  174 . The converter  224  then outputs the yellow conversion signal to cause plasma emission of the yellow fluorescent material  192  of the yellow sub-pixel  174  at the determined third converted luminosity value. 
     The converter  224  multiplies the first emission luminosity value “α” by the value “z”, and then determines a difference value between the first luminosity value corresponding to the red hue, which is defined by the video signal from the stereoscopic signal processor  222 , and the resultant luminosity value from the multiplication of the values “α” by “z” as the first converted luminosity value, which corresponds to the red sub-pixel  172 . The converter  224  then outputs the red conversion signal to cause plasma emission of the red fluorescent material  189  of the red sub-pixel  172  at the determined first converted luminosity value. 
     Likewise, the converter  224  multiplies the second emission luminosity value “β” by the value “z” and then determines a difference value between the second luminosity value corresponding to the green hue, which is defined by the video signal from the stereoscopic signal processor  222 , and the resultant luminosity value from the multiplication of the values of “β” by “z” as the second converted luminosity value, which corresponds to the green sub-pixel  173 . The converter  224  then outputs the green conversion signal to cause plasma emission of the green fluorescent material  191  of the green sub-pixel  173  at the determined second converted luminosity value. 
     In this embodiment, the third luminosity value corresponding to the blue hue in the video signal, which is output by the stereoscopic signal processor  222 , is used as the fourth converted luminosity value corresponding to the blue sub-pixel  175  without being subjected to conversion process. Accordingly, the converter  224  outputs the blue conversion signal to cause plasma emission of the blue fluorescent material  193  of the blue sub-pixel  175  at the fourth converted luminosity value, which is equivalent to the third luminosity value. 
     Like the described methodologies with reference to  FIGS. 8 and 9 , in the conversion process described with reference to  FIG. 10 , the luminosity values of the red and green sub-pixels  172 ,  173 , which have relatively long afterglow times, respectively, are reduced as well to preferably shorten the afterglow time of the pixel  171 . 
       FIG. 11  schematically shows yet another method for generating the conversion signal by the converter  224 . The conversion signal generation by the converter  224  is described with reference to  FIGS. 1A ,  1 B,  3 ,  4 ,  8 ,  9  and  11 . 
     As described above with reference to  FIGS. 1A and 1B , the video signal is output from the stereoscopic signal processor  222  to the converter  224 . The video signal from the stereoscopic signal processor  222  represents the display color of each pixel  171  by means of the first to third luminosity values, which correspond to the red, green and blue hues, respectively. 
     In this embodiment, the storage portion  250  stores in advance a red lookup table  610  for outputting the red conversion signal, a green lookup table  620  for outputting the green conversion signal, a yellow lookup table  630  for outputting the yellow conversion signal and a blue lookup table  640  for outputting the blue conversion signal. 
     The converter  224  refers to the red lookup table (red LUT)  610 , the green lookup table (green LUT)  620 , the yellow lookup table (yellow LUT)  630  and the blue lookup table (blue LUT)  640  to determine the first to fourth converted luminosity values, which correspond to the red, green, yellow and blue sub-pixels  172 ,  173 ,  174  and  175 , on the basis of the first to third luminosity values which the video signal from the stereoscopic signal processor  222  defines for the red, green and blue hues, respectively. 
       FIG. 12  schematically shows a method for determining the first to fourth converted luminosity values by means of the red, green, yellow and blue lookup tables  610 ,  620 ,  630  and  640 . The method for determining the first to fourth converted luminosity values is described with reference to  FIGS. 11 and 12 . 
     Axes on the graphs shown in  FIG. 12  show the first to third luminosity values which the video signal from the stereoscopic signal processor  222  defines for the red, green and blue hues, respectively. In this embodiment, values at each point in the coordinate systems of the red, green, yellow and blue lookup table  610 ,  620 ,  630  and  640  are determined in advance. 
     Values of the first to third luminosity values, which the video signal from the stereoscopic signal processor  222  defines for the red, green and blue hues, respectively, are represented by symbols “p”, “q” and “r”, respectively. The converter  224  looks up coordinate point values determined on each of the coordinate systems of the red, green, yellow and blue lookup tables  610 ,  620 ,  630  and  640 . In  FIG. 12 , a value of the coordinate point (p, q, r) on the coordinate system of the red lookup table  610  is indicated by the symbol “V 1 ”. A value of the coordinate point (p, q, r) on the coordinate system of the green lookup table  620  is indicated by the symbol “V 2 ”. A value of the coordinate point (p, q, r) on the coordinate system of the yellow lookup table  630  is indicated by the symbol “V 3 ”. A value of the coordinate point (p, q, r) on the coordinate system of the blue lookup table  640  is indicated by the symbol “V 4 ”. 
     The converter  224  determines the value “V 1 ” as the first converted luminosity value corresponding to the red sub-pixel  172  and outputs the red conversion signal to emit light from the red sub-pixel  172 . Likewise, the converter  224  determines the value “V 2 ” as the second converted luminosity value corresponding to the green sub-pixel  173  and outputs the green conversion signal to emit light from the green sub-pixel  173 . The converter  224  also determines the value “V 3 ” as the third converted luminosity value corresponding to the yellow sub-pixel  174  and outputs the yellow conversion signal to emit light from the yellow sub-pixel  174 . Likewise, the converter  224  determines the value “V 4 ” as the fourth converted luminosity value corresponding to the blue sub-pixel  175  and outputs the blue conversion signal to emit light from the blue sub-pixel  175 . If the red, green, yellow and blue sub-pixels  172 ,  173 ,  174  and  175  emit the light at the first to fourth converted luminosity value “V 1 ”, “V 2 ”, “V 3 ” and “V 4 ”, respectively, an emitted display color corresponds to the display color of the pixel  171  which the video signal from the stereoscopic signal processor defines by means of the first to third luminosity values that correspond to the red, green and blue hues, respectively. 
     The point values on the coordinate system of the red lookup table  610  may be determined so that if neither the value “p” of the first luminosity value nor the value “q” of the second luminosity value is zero, the value “V 1 ” becomes smaller than the value “p”. Likewise, the point values on the coordinate system of the green lookup table  620  may be determined so that if neither the value “p” of the first luminosity value nor the value “q” of the second luminosity value is zero, the value “V 2 ” is smaller than the value “q”. The point values on the coordinate system of the yellow lookup table  630  may be determined so that if neither the value “p” of the first luminosity value nor the value “q” of the second luminosity value is zero, the value “V 3 ” is larger than zero. 
     As described in the aforementioned embodiment, the afterglow time of the pixel  171  is preferably shortened if there are a decrease in luminosity values of the red and green sub-pixels  172 ,  173 , which have a relatively long afterglow time, and an increase in luminosity value of the yellow sub-pixel  174 , which has a relatively short afterglow time. 
     With the configuration described in the aforementioned embodiment, the yellow sub-pixel emits light so that a display color corresponding to the display color represented by the video signal is displayed under the decreased luminosity values of the red and green sub-pixels. For example, if white is displayed on a conventional plasma display, three sub-pixels such as the red, green and blue sub-pixels have to emit light. In the plasma display according to this embodiment, on the other hand, white may be displayed by emitting light from two sub-pixels such as the yellow and blue sub-pixels. A total plasma discharge amount required for a self-emitting display apparatus such as a plasma display to emit light is typically related to power consumption. According to the principles of this embodiment, less sub-pixels are required to simultaneously emit light to display a specific color, which results in less power consumption. 
     It should be noted that the video system  300 , which includes the display apparatus  100  for displaying stereoscopic video and the eyeglass device  400  for performing the stereoscopic vision assistance, is exemplified in the aforementioned embodiment. Alternatively, the display apparatus may be a video display apparatus without displaying a stereoscopic video like conventional display devices. According to the principles of this embodiment, afterglow may be reduced between frames displayed by the video display apparatus without displaying a stereoscopic video. Alternatively, the principles of this embodiment may be advantageously applied to reduce power consumption of the video display apparatus without displaying stereoscopic video. 
     The aforementioned embodiment mainly includes the following configurations. A display apparatus with the following configurations may provide a video with little afterglow. 
     A display apparatus according to one aspect of the aforementioned embodiment includes: an input port to which a video signal is input, the video signal representing a display color with a first luminosity value corresponding to a red hue, a second luminosity value corresponding to a green hue, and a third luminosity value corresponding to a blue hue; a display portion including a pixel having a red sub-pixel which causes plasma emission in the red hue, a green sub-pixel which causes plasma emission in the green hue, a blue sub-pixel which causes plasma emission in the blue hue, and a yellow sub-pixel which causes plasma emission in a yellow hue; and a converter configured to convert the video signal into a conversion signal so that the red, green, blue and yellow sub-pixels emit light on the display portion to display a display color which corresponds to the represented display color by the video signal, wherein the conversion signal output by the converter includes at least one of a red conversion signal to cause the plasma emission of the red sub-pixel at a first converted luminosity value that is lower than the first luminosity value and a green conversion signal to cause the plasma emission of the green sub-pixel at a second converted luminosity value that is lower than the second luminosity value, and a yellow conversion signal to cause the plasma emission of the yellow sub-pixel, the plasma emission by the yellow sub-pixel results in a shorter afterglow time than resultant afterglow times from the plasma emissions by the red and green sub-pixels, the red sub-pixel causes the plasma emission at the first converted luminosity value, and the green sub-pixel causes the plasma emission at the second converted luminosity value. 
     According to the aforementioned configuration, the video signal represents the display color by the first to third luminosity values corresponding to the red, green and blue hues, respectively. The pixel of the display portion includes the red, green, blue and yellow sub-pixels which cause plasma emissions in the red, green, blue and yellow hues, respectively. The converter of the display apparatus converts the video signal into the conversion signal so that the red, green, blue and yellow sub-pixels emit light on the display portion to display a display color which corresponds to the represented display color by the video signal. The conversion signal output by the converter includes at least one of the red conversion signal to cause the plasma emission of the red sub-pixel at the first converted luminosity value that is lower than the first luminosity value and the green conversion signal to cause the plasma emission of the green sub-pixel at the second converted luminosity value that is lower than the second luminosity value, and the yellow conversion signal to cause the plasma emission of the yellow sub-pixel. Thus, the luminosity values of the red and green sub-pixels are decreased while the yellow sub-pixel causes the plasma emission with a shorter afterglow time than the red and green sub-pixels so as to display a display color which corresponds to the represented display color by the video signal. Therefore, the display portion may display the display color with the short afterglow time. Consequently, the display apparatus may display a video with little afterglow. 
     In the aforementioned configuration, the converter preferably includes a storage portion configured to store a lookup table to determine the first converted luminosity value, the second converted luminosity value, a third converted luminosity value at which the yellow sub-pixel causes the plasma emission, and a fourth converted luminosity value at which the blue sub-pixel causes the plasma emission, based on the first, second and third luminosity values. 
     According to the aforementioned configuration, the converter includes the storage portion which stores the lookup table to determine the first to fourth converted luminosity value of the red, green, yellow and blue sub-pixels, respectively, on the basis of the first to third luminosity values. Accordingly, the first to fourth converted luminosity values of the red, green, yellow and blue sub-pixels are appropriately determined by means of the lookup table, respectively. 
     In the aforementioned configuration, the converter preferably determines smaller one of the first and second luminosity values as a third converted luminosity value at which the yellow sub-pixel causes the plasma emission, and outputs the yellow conversion signal to emit light from the yellow sub-pixel at the third converted luminosity value. 
     According to the aforementioned configuration, the converter determines the smaller one of the first and second luminosity values as the third converted luminosity value of the yellow sub-pixel. The converter then outputs the yellow conversion signal. The converter reduces the luminosity values of the red and green sub-pixels, respectively. Accordingly, the yellow sub-pixel emits light with a short afterglow time at the third converted luminosity value while the red and/or green sub-pixels, of which afterglow is longer than the yellow sub-pixel, emit light at decreased luminosity values. Therefore, the display portion may display the display color with a short afterglow time. As a result, the display apparatus may display a video with little afterglow. 
     In the aforementioned configuration, the converter preferably determines a difference value between the first luminosity value and the smaller one of the first and second luminosity values as the first converted luminosity value. 
     According to the aforementioned configuration, the converter determines the one of the first and second luminosity values as the third converted luminosity value of the yellow sub-pixel. The converter then outputs the yellow conversion signal. The converter determines the difference value between the first luminosity value and the one of the first and second luminosity values as the first converted luminosity value. The converter then outputs the red conversion signal for causing the red sub-pixel to emit light. Thus, the display portion may display the display color with a short afterglow time. As a result, the display apparatus may display a video with little afterglow. 
     In the aforementioned configuration, the converter preferably determines a difference value between the second luminosity value and the smaller one of the first and second luminosity values as the second converted luminosity value. 
     According to the aforementioned configuration, the converter determines the smaller one of the first and second luminosity values as the third converted luminosity value of the yellow sub-pixel. The converter then outputs the yellow conversion signal. The converter determines the difference value between the second luminosity value and the smaller one of the first and second luminosity values as the second converted luminosity value. The converter then outputs the green conversion signal for causing the green sub-pixel to emit light. Therefore, the display portion may display the display color with a short afterglow time. As a result, the display apparatus may display a video with little afterglow. 
     In the aforementioned configuration, the converter preferably multiplies a third emission luminosity value by smaller one of a resultant value from division of the first luminosity value by a predetermined first emission luminosity value and a resultant value from division of the second luminosity value by a predetermined second emission luminosity value to determine a third converted luminosity value, at which the yellow sub-pixel causes the plasma emission, the third emission luminosity value obtained as a sum of the first and second emission luminosity values, the converter outputs the yellow conversion signal to emit light from the yellow sub-pixel at the third converted luminosity value. 
     According to the aforementioned configuration, the converter multiplies the third emission luminosity value by the smaller one of the resultant value from division of the first luminosity value by the predetermined first emission luminosity value and the resultant value from division of the second luminosity value by the predetermined second emission luminosity value, so that the converter determine the third converted luminosity value of the plasma emission of the yellow sub-pixel. It should be noted that the third emission luminosity value is obtained as a sum of the first and second emission luminosity values. The converter then outputs the yellow conversion signal. The converter reduces the luminosity values of the red and green sub-pixels, respectively. Therefore, the yellow sub-pixel emits light with a short afterglow time at the third converted luminosity value while the red and/or green sub-pixels, of which afterglow time is longer than the yellow sub-pixel, emit light at decreased luminosity values. Accordingly the display portion may display the display color with a short afterglow time. As a result, the display apparatus may display a video with little afterglow. 
     In the aforementioned configuration, the converter preferably determines a difference value between the first luminosity value and a luminosity value, which is a resultant value from multiplication of the first emission luminosity value by smaller one of a resultant value from division of the first luminosity value by the first emission luminosity value and a resultant value from division of the second luminosity value by the second emission luminosity value, as the first converted luminosity value. 
     According to the aforementioned configuration, the converter outputting the yellow conversion signal determines the difference value between the first luminosity value and the luminosity value, which is the resultant value from multiplication of the first emission luminosity value by the smaller one of a resultant value from division of the first luminosity value by the first emission luminosity value and the resultant value from division of the second luminosity value by the second emission luminosity value, as the first converted luminosity value. The converter then outputs the red conversion signal for causing the red sub-pixel to emit light. Accordingly, the display portion may display the display color with a short afterglow time. As a result, the display apparatus may display a video with little afterglow. 
     In the aforementioned configuration, the converter preferably determines a difference value between the second luminosity value and a luminosity value, which is a resultant value from multiplication of the second emission luminosity value by the smaller one of the resultant value from division of the first luminosity value by the first emission luminosity value and the resultant value from division of the second luminosity value by the second emission luminosity value, as the second converted luminosity value. 
     According to the aforementioned configuration, the converter outputting the yellow conversion signal determines the difference value between the second luminosity value and the luminosity value, which is a resultant value from multiplication of the second emission luminosity value by the smaller one of the resultant value from division of the first luminosity value by the first emission luminosity value and the resultant value from division of the second luminosity value by the second emission luminosity value, as the second converted luminosity value. The converter then outputs the green conversion signal for causing the green sub-pixel to emit light. Therefore, the display portion may display the display color with a short afterglow time. As a result, the display apparatus may display a video with little afterglow. 
     In the aforementioned configuration, the blue or red sub-pixel is preferably situated between the yellow and green sub-pixels. 
     According to the aforementioned configuration, the blue or red sub-pixel with a low spectral luminous efficiency is situated between the yellow and green sub-pixels with a high spectral luminous efficiency. Therefore the display color defined by the video signal may be appropriately displayed. 
     The principles according to the present embodiment may be preferably applied to self-emitting display apparatuses such as plasma displays.