Abstract:
The objective of the present invention is to enhance a specific color without changing the hue of an original image. 
     At least two different gray-level correction functions are provided for luminance signals input for three colors, R, G and B, and these functions are used to calculate correction coefficients for the individual colors. Then, the luminance signals input for the three colors are synthesized so that the weighting of the colors is changed in accordance with the input luminance signals, and a correction coefficient is calculated that is used in common. The input signals are then multiplied by the thus obtained correction coefficient.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an image signal correction method and an image signal correction apparatus, for suppressing changes in the hues of color images and for correcting gray levels during color image signal processing. 
   2. Related Background Art 
   Recently, for color images on television, an image signal correction process, such as gray-level correction or color correction, has frequently been employed to enhance or to correct ergonomic contrasts and ergonomic brightnesses or hues. 
   As a first conventional gray-level correction technique, processing is well known wherein gray-level correction having the concave input/output characteristics shown in  FIG. 6  is performed for the color input luminance signal of an image to improve the ergonomic contrast of the image. For example, assume that luminance signals for three separate colors, red (R), green (G) and blue (B), are input. When the luminance signals input for the three colors RGB are (R in1 , G in1 , B in1 )=(0.3, 0.4, 0.5) and (R in2 , G in2 , B in2 )=(0.7, 0.8, 0.9), the gray-level transform shown in  FIG. 6  is performed to obtain (R out1 , G out1 , B out1 )=(0.09, 0.16, 0.25) and (R out2 , G out2 , B out2 )=(0.49, 0.64, 0.81). When calculations are performed while the luminance level L of the image is defined as L=0.2125R+0.7154G+0.0721B (ITU-R BT709), L in1 =0.386, L out1 =0.152, L in2 =0.786 and L out2 =0.620 are obtained. The ratios of these levels are L in2 /L in1 =0.786/0.386=2.04, L out2 /L out1 =0.620/0.152=4.09, L out1 /L in1 =0.393 and L out2 /L in2 =0.789. In this case, the luminance is reduced but the contrast is increased. 
   As a second conventional gray-level correction technique, processing is well known whereby gray-level correction having the convex input/output characteristics shown in  FIG. 7  is performed to improve the ergonomic brightness of an image. When luminance signals input for the three RGB colors are (R in1 , G in1 , B in1 )=(0.3, 0.4, 0.5) and (R in2 , G in2 , B in2 )=(0.7, 0.8, 0.9), the gray-level transform shown in  FIG. 7  is performed to obtain (R out1 , G out1 , B out1 )=(0.548, 0.632, 0.707) and (R out2 , G out2 , B out2 )=(0.837, 0.894, 0.949). And through calculation, the luminance level L of the image is obtained as L in1 =0.386, L out1 =0.620, L in2 =0.786 and L out2 =0.886. The ratios of these levels are L in2 /L in1 =0.786/0.386=2.04, L out2 /L out1 =0.886/0.620=1.43, L out1 /L in1 =1.61 and L out2 /L in2 =1.13. In this case, the contrast is reduced but the luminance is increased. 
   However, a problem has arisen that these conventional examples have in common: the RGB ratio is also changed before and after the gray-level correction, and accordingly the hues are altered. 
   A technique to resolve this problem is disclosed in Japanese Patent Application Laid-Open No. H06-311354 (third conventional gray-level correction technique). 
   Employed for the technique disclosed in Japanese Patent Application Laid-Open No. H06-311354 is a configuration, shown in  FIG. 8 , comprising: a preliminary signal processing unit  21 ; a non-linear transforming unit  22 ; a color correction unit  23 ; a signal processing unit  24 ; a color image signal input terminal  25 , for sequentially receiving color image signals; and a color image signal output terminal  26  for outputting color image signals. The preliminary signal processing unit  21  performs the preliminary image signal processing, such as the removal of noise, and the non-linear transforming unit  22  performs the gray-level correction. The color correction unit  23  performs the color correction for the signal output by the non-linear transforming unit  22 , and the signal processing unit  24  performs the post-processing for the signal. 
   The non-linear transforming unit  22 , which is the primary unit, calculates
 
 M =max( R   in   , G   in   , B   in )
 
 R   out   =f ( M )· R   in   /M  
 
 G   out   =f ( M )· G   in   /M  
 
 B   out   =f ( M )· B   in   /M   (Expression 1)
 
and outputs the results. In Expression 1, max( ) denotes a function for selecting the maximum value; R in , G in  and B in  denote input RGB color signals; R out , G out  and B out  denote output RGB color signals; and f( ) denotes a gray-level correction function.
 
   When Expression 1 is transformed, Expression 2 below is obtained,
 
 C=f ( M )/ M  
 
 R   out   =R   in   ·C  
 
 G   out   =G   in   ·C  
 
 B   out   =B   in   ·C   (Expression 2)
 
   while the RGB ratio is not changed before and after the gray-level correction, and the hue is unchanged. 
   In Japanese Patent Application Laid-Open No. H06-311354, a configuration is also described wherein RGB signals are transformed into L*a*b*, or Luv, according to the CIE (Commission Internationale d&#39;Eclairage), the gray-level correction is performed only for the luminance component (L* or L), and thereafter, the resultant signal is inversely transformed. Again, in this case, since only the luminance component is transformed and the color components are not changed, the hue is unchanged. 
   There is another conventional example wherein the gray-level correction is performed only for the Y component of a YUV signal, which is one type of television broadcasting signal. 
   As an additional conventional color correction example, there is one that employs well known processing whereby, as is shown in  FIG. 9 , the hue of an image is corrected by employing different gray-level correction functions for the color input luminance signals R, G and B, i.e., functions f r (x), for R, f g (x), for G, and f b (x), for B (wherein x is an arbitrary value). For example, when the input RGB luminance signals are (R in1 , G in1 , B in1 )=(0.3, 0.4, 0.5) and (R in2 , G in2 , B in2 )=(0.7, 0.8, 0.9), the gray-level correction shown in  FIG. 9  is performed, and (R out1 , G out1 , B out1 )=(0.36, 0.4, 0.5) and (R out2 , G out2 , B out2 )=(0.84, 0.8, 0.9) are obtained. As a result, the ratio R obtained by the gray-level correction is greater than it was before the correction was made, and the reddish hue is enhanced in color. 
   Furthermore, Japanese Patent Application Laid-Open No. H08-315132 discloses, as a method for performing selective-corrections for an original image, a color correction method whereby, to change a selected, individual color, two or more selective color corrections are jointly employed in correspondence with the performance of a weighted, average correction process, during which a weighted value is reduced in consonance with selected changes in an original color. 
   There is also a case wherein, for an image, it is desired that, within a specific range, a color be enhanced without a hue being changed. And if the above described conventional color correction techniques, which use different gray-level correction functions for the RGB colors, were employed, the hue would be changed. 
   As a method for enhancing a color within a specific range without changing the hue, a third gray-level correction method described in related background art can be employed for the color enhancement. According to this method, different gray-level correction functions are provided for the RGB colors, gray-level correction is performed for the R, G or B color signal having the maximum value, and the other color signals are multiplied by the resultant signal, which uses as a coefficient the ratio of the RGB colors before and after the gray-level correction is performed (see  FIG. 10 ). 
   The configuration in  FIG. 10  comprises: a selector  31 , for selecting the maximum value of the RGB signal values that are input; a comparator  32 , for outputting information consonant with the R, G or B signal having the maximum value; a switch  33 , for selecting, in accordance with the output of the comparator  32 , either the R or the G or the B gray-level correction data, which will be described later; an R-gray-level correction data table  34  from which R-gray-level correction data are obtained in accordance with an instruction transmitted by the switch  33 , a G-gray-level correction data table  35  from which G-gray-level correction data are obtained in accordance with an instruction transmitted by the switch  33  or a B-gray-level correction data table  36  from which B-gray-level correction data are obtained in accordance with an instruction transmitted by the switch  33 , and a gray-level correction unit  37 , for applying, for the output value of the selector  331 , the gray-level correction data obtained from the gray-level correction data table  34 ,  35  or  36 ; a divider  38 ; and multipliers  39 ,  40  and  41 . 
   When the RGB gray-level correction functions are as shown in  FIG. 11  (the contents of the R-gray-level correction data table  34  are f r (x), indicated by a solid line, the contents of the G-gray-level correction data table  35  are f g (x), indicated by a broken line, and the contents of the B-gray-level correction data table  36  are f b (x), indicated by a chained line), and when (R in , G in , B in )=(0.7, 0.3, 0.5), for example, is input, the comparator  32  determines that R has the highest value and transmits a corresponding signal to the switch  33 , which selects the R-gray-level correction data table  34 . From among the RGB values, the selector  31  selects a maximum value of 0.7 that it transmits to the gray-level correction unit  37  and the divider  38 . The gray-level correction unit  37  corrects R in  by referring to the R-gray-level correction data table  34 , and outputs a value 0.9 to the divider  38 . The divider  38  divides the value 0.9, obtained following the correction, by the value 0.7, input before the correction, and outputs the value 1.286 as a correction coefficient. The multipliers  39 ,  40  and  41  multiply the original RGB values by the correction coefficient received from the divider  38 , and output (R out , G out , B out )=(0.9, 0.39, 0.64). At this time, R out :G out :B out =0.9:0.39:0.64=0.7:0.3:0.5=R in :G in :B in , and the hue is maintained unchanged. 
   When (R in , G in , B in )=(0.5, 0.7, 0.3) is input, the same processing is performed and the G-gray-level correction data table  35  is selected because G has the highest value, and (R out , G out , B out )=(0.32, 0.45, 0.19) is output. At this time, R out :G out :B out =0.32:0.45:0.19=0.5:0.7:0.3=R in :G in :B in , and the hue is maintained unchanged. 
   Similarly, when (R in , G in , B in )=(0.3, 0.5, 0.7) is input, (R out , G out , B out )=(0.3, 0.5, 0.7) is output, and the color and the luminance are unchanged. 
   That is, in this case, the luminance is increased for the hue (a reddish hue) when R has the highest value, the luminance is reduced for the hue (a greenish hue) when G has the highest value, and the luminance is unchanged for the hue (a bluish hue) when B has the highest value. 
   Generally, when the convex characteristics are provided for the gray-level correction function that corresponds to the R, G or B hue to be enhanced, the luminance of the pertinent hue is increased. While when the concave characteristics are provided for the gray-level correction function that corresponds to the hue that is not to be enhanced, the luminance of this hue is reduced. By employing this method, a color within a specific range can be enhanced. 
   However, with this configuration the following problem is encountered.  FIG. 12  is a graph showing R and G signals along a specific horizontal line on a display device, and a correction coefficient output by the divider  38  and a luminance value on a display screen. When a signal B has a value of 0 across the entire area, as is shown in  FIG. 12 , the maximum value of the R component is to the left, and is reduced toward the right. At the position where R is at its maximum, a G signal has a value of 0. The value of this G component is increased toward the right and is at its maximum at a location whereat the R component has a value of 0. Thus, the R and G values are equal at the center, while to the left thereof, an area is represented wherein a hue becomes increasingly reddish, while to the right thereof, an area is represented wherein the hue becomes increasingly greenish. 
   Since the maximum value of the R component is in the left half in the graph, the correction coefficient is calculated by using the R-gray-level correction function f r (x) in  FIG. 11 . In this example, the correction coefficient is always one or greater, and in the graph, is increased to the right and upward. Further, since the maximum value of the G component is in the right half, the correction coefficient is calculated by using the G-gray-level correction function f g (x) The obtained correction coefficient is always one or smaller, and is reduced to the left and downward. The changes in the luminance at this time are as shown in  FIG. 12 , and the difference in the luminance levels appears as a border in the center of the graph. 
   SUMMARY OF THE INVENTION 
   To resolve these problems, it is one objective of the present invention to provide an image signal correction method and an image signal correction apparatus for enhancing a specific color without changing the hue of the original image. 
   To achieve this objective, according to the present invention, an image signal correction method, for correcting luminance signals input for three colors in accordance with at least two different gray-level correction functions, comprises the steps of: 
   employing the gray-level correction functions for the individual three colors to obtain transform values for the luminance signals input for the three colors; 
   calculating a correction coefficient used in common for individual colors that are synthesized so as to change the weighting for the colors in accordance with the luminance signals that are input for the three colors; and 
   multiplying the luminance signals that are input by the correction coefficient. 
   Furthermore, according to the present invention, an image signal correction apparatus, for correcting luminance signals input for three colors in accordance with at least two different gray-level correction functions, comprises: 
   a correction unit for employing the gray-level correction functions for the individual three colors to obtain transform values for the luminance signals input for the three colors; 
   a correction coefficient calculation unit for calculating a correction coefficient used in common for individual colors that are synthesized so as to change the weighting for the colors in accordance with the luminance signals that are input for the three colors; and 
   a multiplication unit for multiplying the luminance signals that are input by the correction coefficient. 
   According to the present invention, a color within a specific range can be enhanced without changing the hue. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram showing an image signal correction apparatus according to a first embodiment of the present invention; 
       FIG. 2  is a graph showing example gray-level correction functions according to the first embodiment; 
       FIG. 3  is a graph showing signals for a cross section of an image, a correction coefficient and an output luminance level; 
       FIG. 4  is a block diagram showing an image signal correction apparatus according to a second embodiment of the present invention; 
       FIG. 5  is a block diagram showing an image signal correction apparatus according to a third embodiment of the present invention; 
       FIG. 6  is a graph showing an example gray-level correction function used to perform a conventional gray-level correction process; 
       FIG. 7  is a graph showing another example gray-level correction function used to perform a conventional gray-level correction process; 
       FIG. 8  is a block diagram for explaining the conventional gray-level correction process; 
       FIG. 9  is a graph showing an example correction function employed to perform color enhancement using a conventional technique; 
       FIG. 10  is a block diagram showing an image signal correction apparatus that performs color enhancement by using a conventional technique; 
       FIG. 11  is a graph showing an example gray-level correction function for explaining the operation wherein color enhancement is performed using a conventional technique; 
       FIG. 12  is a graph showing a specific example wherein color enhancement has been performed by using a conventional technique; and 
       FIG. 13  is a block diagram showing a television set according to the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   First Embodiment 
   (Overview) Assume that RGB values obtained by color decomposition of an input image luminance signal are R in , G in  and B in , and that the gray level correction function for R is denoted by f r (x), the gray level correction function for G is denoted by f g (x), and the gray level correction function for B is denoted by f b (x). Further, assume that K r  denotes the ratio of the input R value to the output value (a transform value) obtained by the gray-level correction function, K g  denotes the ratio of the input G value to the output value (a transform value) obtained by the gray-level correction function, and K b  denotes the ratio of the input G value to the output value (a transform value) obtained by the gray-level correction function. Then, K r , K g  and K b  are represented as in Expression 3.
 
 K   r   =f   r ( R   in )/ R   in  
 
 K   g   =f   g ( G   in )/ G   in  
 
 K   b   =f   b ( B   in )/ B   in   (Expression 3)
 
   Correction coefficient C for a pixel is obtained by using a weighted average, i.e., by adding weights consonant with the input RGB values to these ratios. That is, Expression 4 below is established. 
   
     
       
         
           
             
               
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   The input RGB values are multiplied by the correction coefficient C that is used in common, and the gray-level correction is performed. 
   (Configuration) 
     FIG. 1  is a block diagram for this embodiment. In  FIG. 1 , an R-gray-level correction unit  1  employs gray level correction function f r (R in ) for an input value R in , and outputs the results. A G-gray-level correction unit  2  employs gray level correction function f g (G in ) for an input value G in , and outputs the results. A B-gray-level correction unit  3  employs gray level correction function f b (B in ) for an input value B in , and outputs the results. 
   A multiplier  4  multiplies the input value R in  by the output of the R-gray-level correction unit  1 . A multiplier  5  multiplies the input value G in  by the output of the G-gray-level correction unit  2 . And a multiplier  6  multiplies the input value Bin by the output of the B-gray-level correction unit  3 . An adder  7  then adds the outputs of the multipliers  4 ,  5  and  6 . 
   A square sum calculator  8  squares each of the individual input RGB values, and adds the squares together. A divider  9  divides the output of the adder  7  by the output of the square sum calculator  8 . A multiplier  10  multiplies the input value R in  by the output of the divider  9 . A multiplier  11  multiplies the input value G in  by the output of the divider  9 . And a multiplier  12  multiplies the input value B in  by the output of the divider  9 . 
   In this embodiment, the R-gray-level correction unit  1 , the G-gray-level correction unit  2  and the B-gray-level correction unit  3  constitute correction means. In addition to the R-gray-level correction unit  1 , the G-gray-level correction unit  2  and the B-gray-level correction unit  3 , the multipliers  4 ,  5  and  6 , the adder  7 , the square sum calculator  8  and the divider  9  constitute the correction coefficient calculation means. The value that is finally output by the divider  9  is the correction coefficient C. The multipliers  10 ,  11  and  12  constitute multiplication means. 
     FIG. 2  is a graph showing example input/output characteristics of the R-gray-level correction unit  1  (solid line), the G-gray-level correction unit  2  (broken line) and the B-gray-level correction unit  3  (chained line). In  FIG. 2 , the input/output characteristics of the R-gray-level correction unit  1  are represented as convex, the input/output characteristics of the G-gray-level correction unit  2  are represented as concave, and the input/output characteristics of the B-gray-level correction unit  3  are represented as linear. 
   When the gray-level correction functions shown in  FIG. 2  are employed, and when RGB value (R in , G in , B in )=(0.7, 0.3, 0.5) is input to a specific pixel, R in  is input to the R-gray-level correction unit  1  and f r (R in )=0.9 is output. Similarly, f g (G in )=0.14 and f b (B in )=0.5 are obtained. 
   The multipliers  4 ,  5  and  6  multiplies these obtained values by the input values R in , G in  and B in , and the adder  7  adds the outputs of the multipliers  4 ,  5  and  6 . Then, the adder  7  outputs R in ×f r (R in )+G in ×f g (G in )+B in ×f b (B in )=0.7×0.9+0.3×0.14+0.5×0.5=0.92. 
   The square sum calculator  8  adds 0.49, 0.09 and 0.25, which are the squares of input values 0.7, 0.3 and 0.5, and outputs a square sum S=0.83. 
   The output value 0.92 of the adder  7  and the output value 0.83 of the square sum calculator  8  are transmitted to the divider  9 , and the correction coefficient C=0.92/0.83=1.11 is obtained that is to be used in common for the individual colors. 
   The original input values are multiplied by the correction coefficient C, and the final output values R out =C×R in =0.776, G out =C×G in =0.333 and B out =C×B in =0.554 are output. The ratio of R out , G out  and B out  is R out :G out :B out =0.776:0.333:0.554=0.7:0.3:0.5=R in :G in :B in  and is substantially equal to the RGB ratio before the gray-level correction, and there is no hue change. 
   Similarly, when RGB value (R in , G in , B in )=(0.3, 0.7, 0.5) is input, (f r (R out ), f g (G out ), f b (B out ))=(0.5, 0.45, 0.5) is obtained, and the output of the divider  9 , i.e., the correction coefficient C, is C=(0.3×0.5+0.7×0.45+0.5×0.5)/(0.3 2 +0.7 2 +0.5 2 )=0.715/0.83=0.86. 
   The final output value is (R out , G out , B out )=(0.258, 0.603, 0.431), and R out :G out :B out =0.258:0.603:0.431≅0.3:0.7:0.5=R in :G in :B in , which is substantially equal to the RGB ratio before the gray-level correction, and there is no hue change. 
   With the configuration of this embodiment, when color correction is performed for an image, like a pattern wherein a defect described as the above problem occurs, the characteristics are as shown in  FIG. 3 , and the luminance is smoothly changed without the luminance difference shown in  FIG. 12 . As is described above, according to the embodiment, a color within a specific range can be enhanced and the luminance smoothly changed, while the occurrence of a difference in the luminance is avoided and the hue is unchanged. 
   Second Embodiment 
   A second embodiment of the present invention is shown in  FIG. 4 . In  FIG. 4 , a limiter  13  limits the output of the multiplier  10  so that the output does not exceed the maximum value available for R. A limiter  14  limits the output of the multiplier  11  so that the output does not exceed the maximum value available for G. And a limiter  15  limits the output of the multiplier  12  so that the output does not exceed the maximum value available for B. Since the other configuration is the same as that for the first embodiment, the same reference numerals are also employed for these corresponding components, and no further explanation for them will be given. In the second embodiment, the limiters  13 ,  14  and  15  constitute limiting means. 
   In this embodiment, the same processing as in the first embodiment is performed until values are output by the multipliers  10 ,  11  and  12 . Output C×R in  for the multiplier  10  is transmitted to the limiter  13 . The limiter  13  determines whether the value obtained by the multiplier  10  is greater than the maximum value (255 when eight bits are employed) available for R. When the value obtained by the multiplier  10  is not greater than the maximum value, the value is output unchanged. But when the maximum value is exceeded, the maximum value (255 when eight bits are employed) is output. Likewise, the limiters  14  and  15  compare the values for C×G in  and C×B in , output by the multipliers  11  and  12 , with the maximum values respectively available for G and B. When the values obtained by the multipliers  11  and  12  are not greater than their respective maximum values, the values are output unchanged. And when the maximum values are exceeded, the maximum values are output. 
   Through this processing, it is possible to prevent the occurrence of the problem that arises when the correction coefficient C becomes so large that the output value exceeds the available maximum value. 
   Third Embodiment 
   A third embodiment of the present invention is shown in  FIG. 5 . In  FIG. 5 , a maximum detector  16  detects and outputs the maximum RGB values that are input. A coefficient calculator  17  outputs a value obtained by dividing the maximum values available for RGB by the output of the maximum detector  16 . A comparator  18  compares the output of a divider  9  with the output of the coefficient calculator  17 , and outputs the smaller value. Since the remainder of the configuration is the same as that for the first embodiment, the same reference numerals are employed to denote the corresponding components, and no further explanation for them will be given. In this embodiment, the maximum detector  16  and the coefficient calculator  17  constitute the maximum value calculation means, and the comparator  18  and multipliers  10 ,  11  and  12  constitute the comparison and multiplication means. 
   In this embodiment, the same processing as in the first embodiment is performed until a value is output by the divider  9 . The input RGB values R in , G in  and B in  are transmitted to the maximum detector  16 , and the maximum value is output. The maximum RGB value output by the maximum detector  16  is then transmitted to the coefficient calculator  17 . The coefficient calculator  17  divides, by the input value, a maximum value V max  (255 when eight bits are employed) available for the RGB, and outputs the result to the comparator  18 . The comparator  18  compares the output of the divider  9  with the output of the coefficient calculator  17 , and outputs the smaller value. Thereafter, the value output by the comparator  18  is transmitted to the multipliers  10 ,  11  and  12 , and this value is used to multiply the input signals R in , G in  and B in  and obtain the final output values R out , G out  and B out . 
   In the first embodiment, when the correction coefficient C is greater than V max /max(R in , G in , B in ), one of the output values R out , G out  and B out  would exceed the value V max . In this embodiment, however, since the calculation V max /max(R in , G in , B in ) is performed in advance by the coefficient calculator  17 , when the comparison is performed, a smaller value, either V max /max(R in , G in , B in ) or the correction coefficient C, is output. Therefore, color correction can be performed without the maximum available value being exceeded. 
   In the first to the third embodiments, the correction coefficient C has been calculated by using (Expression 4); however, another expression may be employed, just so long as a correction coefficient that satisfies the conditions of the invention can be obtained. 
   Furthermore, the configurations for the first to the third embodiment have been explained while referring to the block diagrams; however, the configurations that provide the present invention are not limited to those in the embodiments. 
     FIG. 13  is a block diagram showing a television set according to the present invention. A receiving circuit  20 , which is a tuner or a decoder, for example, receives data broadcast across a network, and outputs decoded image data to an image processing unit  21 . The image processing unit  21  includes a γ correction circuit, a resolution conversion circuit, an I/F circuit, and an image signal correction apparatus such as is described in the above embodiments. The image processing unit  21  converts image data it receives to prepare suitable image data for a display format, and outputs the resultant data to an image display device  25 . The image display device  25  includes a display panel  24 , a drive circuit  23  and a control circuit  22 . When image data are received, the control circuit  22  performs signal processing, such as a correction process, that is appropriate for the display panel  24 , and outputs the image data and various control signals to the drive circuit  23 . Based on the thus received image data, the drive circuit  23  outputs a drive signal to the display panel  24  and a TV image is displayed thereon. 
   The receiving circuit  20  and the image processing unit  21  may be installed, separate from the image display device  25 , in a set top box (STB)  26 , or may be installed with the image display device  25  in a single cabinet. 
   This application claims priority from Japanese Patent Application No. 2004-042487 filed on Feb. 19, 2004, which is hereby incorporated by reference herein.