Abstract:
The present invention provides an array display apparatus in which multiple light-emitting tubes each having a fluorescent substance layer inside are aligned and a discharge is generated within these multiple light-emitting tubes, whereby the fluorescent substance layers within the light-emitting tubes are caused to emit light thereby to display an image. The array display apparatus displays an image of uniform luminance irrespective of the planar shape of a display surface when image data representing a uniform image is inputted.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an array display apparatus in which multiple light-emitting tubes each having a fluorescent substance layer inside are aligned and a discharge is generated within these multiple light-emitting tubes, whereby the fluorescent substance layers within the light-emitting tubes are caused to emit light thereby to display an image. 
   2. Description of the Related Art 
   As a large-sized image display device which performs spontaneous light emission there has been proposed a technique in which a large number of light-emitting lines formed from glass tube, each of which has a fluorescent substance layer and the like inside, are arrayed, whereby the light emission for each part of each of the light-emitting lines is controlled thereby to display an image (refer to the Japanese Patent Laid-Open No. 61-103187). 
   In each of the light-emitting lines, a protective film, such as an MgO film, and a fluorescent substance layer are formed in the interior of a glass tube and a discharge gas consisting of Ne and Xe, for example, is filled in the glass tube. The fluorescent substance layer is formed on a supporting member called a boat, which is a mounted part having a sectional shape close to a semicircle, and this supporting member (boat) is inserted into the glass tube. After that, the glass tube is evacuated within a vacuum chamber while being heated and both ends of the glass tube are sealed after a discharge gas is filled. A large number of light-emitting lines thus fabricated are arrayed in parallel and fixed and electrodes are provided for these light-emitting lines. By applying a voltage to these electrodes, a discharge is generated in the interior of the light-emitting lines, whereby the fluorescent substance layer is caused to emit light. 
     FIG. 1  is a perspective view which shows the basic structure of a plasma tube array, which is an example of an array display apparatus. 
   In the plasma tube array (PTA)  100  shown here, light-emitting lines  10 R,  10 G,  10 B,  10 R,  10 G,  10 B, . . . , in which fluorescent substance layers generating respectively fluorescent light of the colors red (R), green (G) and blue (B) are disposed and a discharge gas is sealed, are arrayed parallel to each other and in a planar manner as a whole, and a transparent front surface supporting board  20  and a back surface supporting board  30  are disposed respectively on a display surface, which is a front surface, and a back surface of these many arrayed light-emitting lines  10 R,  10 G,  10 B,  10 R,  10 G,  10 B, . . . , with these many arrayed light-emitting lines  10 R,  10 G,  10 B,  10 R,  10 G,  10 B, . . . sandwiched between the front surface supporting board  20  and the back surface supporting board  30 . 
   On the front surface supporting board  20  is formed a display electrode pair  21 , which is constituted by two display electrodes  211 ,  212  extending parallel to each other in the array direction of the many light-emitting lines  10 R,  10 G,  10 B,  10 R,  10 G,  10 B, . . . , i.e., in a direction in which the display electrode pair  21  spans these many light-emitting lines  10 R,  10 G,  10 B,  10 R,  10 G,  10 B, . . . . This display electrode pair  21  is arrayed in multiple numbers in the longitudinal direction of the light-emitting lines  10 R,  10 G,  10 B,  10 R,  10 G,  10 B, . . . . The two display electrodes  211 ,  212  which constitute one display electrode pair  21  are constituted by bus electrodes  211   a ,  212   a  made of metal (for example, Cr/Cu/Cr), each formed on a side away from each other, and transparent electrodes  211   b ,  212   b  made from ITO thin films, each formed on a side close to each other. The bus electrodes  211   a ,  212   a  serve to lower the electric resistance of the display electrodes  211 ,  212 , and the transparent electrodes  211   b ,  212   b  serve to ensure bright display by causing the luminous light in the light-emitting lines  10 R,  10 G,  10 B,  10 R,  10 G,  10 B, . . . to be transmitted to the front surface supporting board  20  side without intercepting the luminous light. The display electrode pair  21  is not limited to a transparent electrode and may be also constituted by an electrode of a structure having high aperture ratio, such as a mesh electrode. 
   On the back surface supporting board  30  are formed a large number of signal electrodes  31  made of metal which extend parallel to each other along each of the many arrayed light-emitting lines  10 R,  10 G,  10 B,  10 R,  10 G,  10 B, . . . in a manner corresponding to each of the light-emitting lines. 
   When the PTA  100  thus constructed is viewed in a planar manner, the part of intersection of the signal electrode  31  and the display electrode pair  21  becomes a unit light emission region (a unit discharge region). Display is performed by using one of the two display electrodes  211 ,  212  as a scanning electrode, selecting a light emission region by generating a selective discharge in the part of intersection of this scanning electrode and the signal electrode  31 , and generating a display discharge between the display electrodes  211 ,  212  by use of a wall charge formed on the inner surface of the light-emitting line in the region due to the discharge. The selective discharge is an opposite discharge generated within a light-emitting line between the scanning electrode and the signal electrode  31 , which are vertically opposite to each other, and the display electrode is a planar discharge generated within a light-emitting line between the display electrodes  211 ,  212  disposed parallel on a plane. Owing to this electrode arrangement, multiple light emission regions are formed within a light-emitting line in the longitudinal direction thereof. 
     FIG. 1  shows a structure in which three electrodes are disposed in one light emission region, and a display discharge is generated by the display electrodes  211 ,  212 . However, the structure is not limited to this one and can be a display discharge generated between the display electrodes  211 ,  212  and the signal electrode  31 . That is, it is possible to adopt an electrode structure of such a type that the display electrodes  211 ,  212  are formed as one electrode and by using this one display electrode as a scanning electrode, a selective discharge and a display discharge (an opposite discharge) are generated between this display electrode and a data electrode  3 . 
     FIG. 2  is a schematic diagram which shows the structure of light-emitting lines constituting the PTA  100  shown in  FIG. 1 . 
   Three light-emitting lines  10 R,  10 G,  10 B are shown here. In each of the light-emitting lines  10 R,  10 G,  10 B, a protective film  12 , such as an MgO, is formed on the inner surface of a glass tube  11 , and within the glass tube  11  is inserted a boat  13 , which is a supporting member in which fluorescent substance layers  14 R,  14 G,  14 B generating fluorescent light of the colors R, G, B are formed (refer to the Japanese Patent Laid-Open No. 2003-86141). 
     FIG. 3  is a diagram which shows a boat on which a fluorescent substance layer is formed. 
   The boat  13  has a shape with a semicircular or U-shaped section or with a section similar to these sections, and also has a shape elongated long as with the glass tube  11  (refer to  FIG. 2 ). On the inner side of the boat  13  are formed three kinds of fluorescent substance layers  14 R,  14 G,  14 B (refer to  FIG. 2 ; represented here by a fluorescent substance layer  14 ) corresponding to the three kinds of light-emitting lines  10 R,  10 G,  10 B shown in  FIGS. 1 and 2 . 
   Again with reference to  FIG. 2 , the description will be continued. 
   Each of the light-emitting lines  10 R,  10 G,  10 B shown in  FIG. 2  is constructed by inserting the boat  13  having the shape shown in  FIG. 3  into the glass tube  11 . In  FIG. 2 , it is shown that a display electrode pair  21  constituted by two display electrodes  211 ,  212  is disposed on these light-emitting lines  10 R,  10 G,  10 B. These two display electrodes  211 ,  212  are respectively constituted by bus electrodes  211   a ,  212   a  made of metal and transparent electrodes  211   b ,  212   b.    
   In the case of the structure shown in  FIG. 2 , the three light-emitting lines  10 R,  10 G,  10 B which are respectively provided with the three kinds of fluorescent substance layers  14 R,  14 G,  14 B constitute one set, and the region D 1  defined by one set of display electrode pair  21  constituted by the two display electrodes  211 ,  212  becomes one pixel, which is the unit of color image display. The diameter of each of the light-emitting lines  10 R,  10 G,  10 B is typically 1 mm or so, and hence in the case of the structure shown in  FIG. 2 , the size of the region D 1  of one pixel becomes approximately 3 mm×3 mm. 
     FIG. 4  is a diagram which shows examples of display driving method in one frame period. 
   A subframe (SF) in which the periods of “initialization,” “address” and “display” constitute one set is aligned in multiple numbers. In the period of “initialization”, initialization is performed to make preparations for next light emission for each display pixel, in the next period of “address”, a display pixel which is to emit light is selected from display pixels which are two-dimensionally aligned in many numbers, and in the next period of “display”, the display pixel selected in the period of “address” immediately before this “display” period emits light. 
   The time length of the period of “display” differs from one SF to another, and depending on combinations of SFs in which light emission is to be performed from among these multiple SFs within one frame, the light emission luminance related to the “one frame” of the display pixel is determined. That is, on the basis of each pixel value of each display pixel within one frame, a light emission pattern is found for each display pixel as to which SF light is used for light emission and which SF light is not used for light emission, among the SFs which are aligned in multiple numbers within the one frame. Each display pixel emits light according to a light emission pattern for each display pixel. As a result of this, an image for one frame is displayed on the display screen. 
   Part (A) of  FIG. 4  shows an example of one-mountain type arrayed SF structure. In this example, the time length of “display” is longest at the head within one frame and the more backward the position of an SF within one frame, the shorter the time. The time length of the “display” has such a shape that, so to speak, one mountain having a peak is formed at the head within the “one frame.” 
   Part (B) of  FIG. 4  shows an example of two-mountain type arrayed SF structure. In this example, one frame is divided into a first half portion and a second half portion (the first half portion and the second half portion when one frame is divided like this are each called here a halfframe). For example, one frame having the same SF as arrayed within one frame of part (A) of  FIG. 4  is divided into two halfframes (the first half portion and the second half portion). At this time, in each interior of each halfframe, the period of “display” of the SF at the head has the longest time and the more backward, the shorter the time. Therefore, the time length of the “display” has a peak at the head of each of the first half portion and the second half portion, so to speak, two mountains are formed within one frame. 
   Although there are various ideas about a display driving method other than these two examples, details of them are omitted here. 
     FIG. 5  is a block diagram of a plasma tube array and  FIG. 6  is a function block diagram of a display circuit portion of the plasma tube array shown in  FIG. 5 . 
     FIG. 5  shows, as the component elements of the plasma tube array  100 , a display circuit section  100 B, which is constituted by a memory of conversion table of pixel value-light emission patterns  50   a , a data control circuit  51 , a driver control circuit  52 , a signal electrode driver  53 , a scanning electrode driver  54  and a common electrode driver  55 , in addition to an image display section  100 A in which light-emitting lines are arrayed and which has been described with reference to  FIG. 1  to  FIG. 3 . 
   In this display circuit section  100 B, processing for pixel value-light emission pattern conversion  61  and driving processing  62  are executed as shown in  FIG. 6 . 
   In processing for pixel value-light emission pattern conversion  61 , for each pixel value, input image data is converted to a light emission pattern as to in which subframe (SF) light is emitted and in which subframe light is not emitted. In driving processing  62 , the light emission of each pixel is controlled according to a light emission pattern obtained in the processing for pixel value-light emission pattern conversion  61 . 
   In the circuit block shown in  FIG. 5 , the processing for pixel value-light emission pattern conversion  61  is performed by the memory of conversion table of pixel value-light emission patterns  50   a  and the data control circuit  51 . That is, in the memory of conversion table of pixel value-light emission patterns  50   a  are stored pixel value-light emission conversion tables in which pixel values and light emission patterns are associated with each other, image data is inputted to the data control circuit  51  sequentially for each frame, and in the data control circuit  51 , conversion tables of pixel value-light emission patterns are referred to, whereby the pixel value of each pixel in the image data for each frame is converted to a light emission pattern. 
   Data which represents light emission patterns thus obtained, along with the address information of pixels, is inputted to the driver control circuit  52 . 
   The driving processing  62  shown in  FIG. 6  is performed by the driver control circuit  52 , the signal electrode driver  53 , the scanning electrode driver  54  and the common electrode driver  55 , which are shown in  FIG. 5 . The driver control circuit  52  receives the address information of each pixel and the light emission pattern data of each pixel, and in accordance with the received address information and data, the driver control circuit  52  controls the signal electrode driver  53  which drives the signal electrode  31 , the scanning electrode driver  54  which drives each of the two display electrodes  211 ,  212  which constitute the display electrode pair  21 , and the common electrode driver  55 , thereby causing the image display section  100 A in which light-emitting lines are aligned to display an image corresponding to the image data. 
   Incidentally, the driving processing  62  shown by a block in  FIG. 6 , i.e., the processing for displaying an image on the image display section  100 A which is performed by the driver control circuit  52  shown in  FIG. 5  by driving the three drivers (the signal electrode driver  53 , the scanning electrode driver  54  and the common electrode driver  55 ) is a hitherto known technique, and because this driving processing is not a main subject here, a further description thereof is omitted. 
   In a PTA having a basic structure as described above, it is conceivable that a display surface on which images are displayed is formed as a curved surface by aligning light-emitting lines along the curved surface, and not in a planer manner. 
   For example, Japanese Patent Laid-Open No. 2003-92085 describes an example in which the whole area of the wall of a cylindrical room is a display surface. 
   By forming the display surface of a curved surface in this manner, it is possible to greatly increase the range of uses of a PTA. 
   Even in a case where a display surface is formed as a curved surface by arraying light-emitting lines so as to extend along the curved surface, there is no problem for a portion where the geometric environment of light-emitting lines is common to all light-emitting lines as in the case of the cylindrical arraying, which is shown in Japanese Patent Laid-Open No. 2003-92085. However, a problem occurs for a portion where the geometric environment differs from one light-emitting line to another. 
     FIG. 7  is a schematic diagram which shows multiple arrayed light-emitting lines.  FIG. 8  is a schematic diagram which shows the array of the light-emitting lines  10  taken along the arrow A-A of  FIG. 7 .  FIG. 9  is a schematic diagram which shows the array of the light-emitting lines  10  taken along the arrow B-B of  FIG. 7 . 
   The multiple light-emitting lines shown in  FIG. 7  are arrayed in such a manner that part of the display region of a display surface forms a plane surface as shown in  FIG. 8  and another part of the display region forms a curved surface as shown in  FIG. 9  (in the example shown here, a convex surface having a positive curvature). 
   Two display electrodes  121 ,  122 , which extend in the direction laterally intersecting these multiple light-emitting lines  10  are shown in  FIG. 7 . By applying a driving voltage to these two display electrodes  121 ,  122 , a discharge is generated in the regions corresponding to the discharge slit between these two display electrodes  121 ,  122  within the light-emitting lines  10 , with the result that light emission occurs. The surface of the front surface supporting board  20  in which these two display electrodes  121 ,  122  are formed is formed partially as a plane surface and partially as a curved surface according to the array of the light-emitting lines  10 . 
   When multiple regions in different geometric environments are present on one display surface as in this example, display luminance differs from one region to another, posing the problem that nonuniformity in luminance occurs in terms of the whole area of the display surface. 
   That is, compared to the plane surface (zero curvature) shown in  FIG. 8 , in the case of a convex surface (positive curvature) as shown in  FIG. 9 , the width of a pixel for which one light-emitting line takes charge of light emission widens and light emission luminance per unit area decreases accordingly. 
     FIG. 10  is an explanatory diagram of a decrease rate of luminance. 
   Part (A) of  FIG. 10  shows a display surface which is bent at a right angle by one light-emitting line. In this case, one light-emitting line at the corner has an angle of π/2 and when the radius of the light-emitting line is expressed by r, the area of the region in which only this light-emitting line takes partial charge of light emission widens by πr/2 in terms of length. In this case, the luminance of the portion at this corner decreases, for example, by about 44% compared to other plane surface portion. 
   Part (B) of  FIG. 10  shows a display surface which is bent at a right angle through two light-emitting lines. In this case, the two light-emitting lines at the corner each have an angle of π/4 and the area of the region in which the two light-emitting lines take partial charge of light emission widens by πr/4 for each in terms of length. In this case, the luminance of the portion at this corner decreases, for example, by about 29% compared to other plane surface portion. 
   Part (C) of  FIG. 10  shows a display surface which is bent at a right angle through three light-emitting lines. In this case, the three light-emitting lines at the corner each have an angle of π/6 and the area of the region in which the three light-emitting lines take partial charge of light emission widens by πr/6 for each in terms of length. In this case, the luminance of the portion at this corner decreases, for example, by about 17% compared to other plane surface portion. 
   Thus, the larger the curvature (Part (A) of  FIG. 10  shows a large curvature and Part (C) of  FIG. 10  shows a small curvature), the more the luminance decreases. 
   Although the description has been given here of a display surface which is a convex surface having a positive curvature, the same thing applies also to the case of a display surface which is a concave surface having a negative curvature. In the case of a display surface which is a concave surface, the larger the absolute value of the curvature, the more the luminance increases. 
   SUMMARY OF THE INVENTION 
   The present invention has been made in view of the above circumstances and provides an array display apparatus which can display an image of uniform luminance irrespective of the planar shape of a display surface when image data representing a uniform image is inputted. 
   An array display apparatus of the present invention includes: multiple light-emitting tubes, which each have a fluorescent substance layer inside and are arrayed parallel to each other and along a display surface having a partially different curvature; a front surface supporting member and a back surface supporting member, which support these multiple light-emitting tubes by sandwiching the light-emitting tubes and extend over on the side of the display surface and on the side of a back surface, respectively; multiple display electrodes, which are formed on a surface opposite to the light-emitting tubes of the front surface supporting member and extend in a direction in which the display electrodes span the light-emitting tubes; multiple signal electrodes, which are formed on a surface opposite to the light-emitting tubes of the back surface supporting member in a manner corresponding to each of the light-emitting tubes and extend in a direction along the light-emitting tubes; and a luminance adjusting section which adjusts luminance by each of the light-emitting tubes according to a partial curvature of the display surface. 
   Because an array display apparatus of the present invention has the luminance adjusting section and adjusts luminance according to a partial curvature of the display surface, the occurrence of streaky regions with decreased luminance or increased luminance is prevented. 
   In the array display apparatus of the present invention, it is preferred that the luminance adjusting section is such that the larger an absolute value of curvature of a region of the display surface formed by a light-emitting tube, which surface is a convex surface, the higher the luminance of the display surface. Also, it is preferred that the luminance adjusting section is such that the larger an absolute value of curvature of a region of the display surface formed by a light-emitting tube, which surface is a concave surface, the lower the luminance of the display surface. 
   In the array display apparatus of the present invention, it is preferred that the luminance adjusting section includes a feature that the display electrodes have such an electrode structure that transmittance differs depending on a partial curvature of the display surface. Also, it is preferred that the luminance adjusting section includes a feature that the display electrodes have such an electrode structure that discharge efficiency differs depending on a partial curvature of the display surface when the same voltage is applied. 
   In the array display apparatus of the present invention, it is preferred that the luminance adjusting section includes a feature that the thickness of the fluorescent substance layer within the light-emitting tubes which form regions of the display surface differs depending on the curvature of each of the regions, or it is also preferred that the luminance adjusting section includes a feature that the position of the fluorescent substance layer disposed within the light-emitting tubes which form regions of the display surface differs depending on the curvature of each of the regions. 
   Furthermore, in the array display apparatus of the present invention, it is also preferred that the array display apparatus further includes a driving circuit, to which image data is input and which drives the display electrodes and the signal electrodes according to the image data, thereby causing an image by luminance distribution to be displayed on the display surface, and wherein the luminance adjusting section includes a data conversion circuit, to which image data is input and which gives weight, which differs depending on the curvature of each of regions constituting the display surface, to a pixel value of a pixel which is taken partial charge of by the light-emitting tube corresponding to each of the regions, generates new image data thereby and inputs the new image data to the driving circuit. 
   According to the present invention described above, it is possible to obtain an image of uniform luminance when image data showing a uniform image is inputted. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view which shows the basic structure of a plasma tube array, which is an example of an array display apparatus; 
       FIG. 2  is a schematic diagram which shows the structure of light-emitting lines constituting the plasma tube array shown in  FIG. 1 ; 
       FIG. 3  is a diagram which shows a boat on which a fluorescent substance layer is formed; 
       FIG. 4  is a diagram which shows examples of display driving method in one frame period; 
       FIG. 5  is a block diagram of a plasma tube array; 
       FIG. 6  is a function block diagram of a display circuit portion of the plasma tube array shown in  FIG. 5 ; 
       FIG. 7  is a schematic diagram which shows multiple arrayed light-emitting lines; 
       FIG. 8  is a schematic diagram which shows the array of the light-emitting lines taken along the arrow A-A of  FIG. 7 ; 
       FIG. 9  is a schematic diagram which shows the array of the light-emitting lines taken along the arrow B-B of  FIG. 7 ; 
       FIG. 10  is an explanatory diagram of a decrease rate of luminance; 
       FIG. 11  is a diagram which shows a display electrode pair which is constituted by two display electrodes; 
       FIG. 12  is a diagram which shows other means to adjust luminance; 
       FIG. 13  is a diagram which shows other means to adjust luminance; 
       FIG. 14  is a diagram which shows the inner structure of light-emitting lines; 
       FIG. 15  is a diagram which shows the inner structure of light-emitting lines; 
       FIG. 16  is a block diagram of a plasma tube array; and 
       FIG. 17  is a function block diagram of a display circuit portion of the plasma tube array shown in  FIG. 16 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Embodiments of the present invention will be described below. 
   In various embodiments described below, the basic structure is the same as the PTA described by referring to  FIG. 1  to  FIG. 6  above. Therefore, overlapping descriptions are omitted here and various embodiments will be described with respect points in which they differ from the PTA. 
     FIG. 11  is a diagram which shows a display electrode pair which is constituted by two display electrodes. 
   In both parts (A) and (B) of  FIG. 11  are shown two display electrodes  121 ,  122  which are disposed with a discharge gap  120  having a width d sandwiched between the two. In the case of the display electrode pair shown in part (A) of  FIG. 11 , the portions opposed to each other with the discharge gap  120  of the display electrodes  121 ,  122  sandwiched therebetween (the portions which act substantially as discharge electrodes) have an electrode structure in which relatively thick fine metal wires  127  are installed in mesh form. In the case of the display electrode pair of part (B) of  FIG. 11 , these portions have an electrode structure in which fine metal wires  127  of relatively fine diameter are installed in mesh form. Therefore, in the case of part (A) of  FIG. 11 , apertures  128  which are enclosed by the fine metal wires  127  and through which the light from light-emitting lines is transmitted are relatively narrow and, for this reason, the transmittance of light is relatively low. On the other hand, in the case of part (B) of  FIG. 11 , apertures  128  are relatively wide and the transmittance of light is relatively high. 
   The transmittance of light may be adjusted so that uniform luminance is obtained by forming display electrodes from metal meshes having different aperture ratios depending on the curvature of each region of the display surface in this manner. 
   In  FIG. 11 , by way of example, the width d is 400 μm, the wire width of the display electrodes  121 ,  122  is 20 μm (in the case of part (A) of  FIG. 11 ) and 16 μm (in the case of part (B) of  FIG. 11 ), and the size e, f of the aperture  128  is (100 μm—wire width) in both cases. 
     FIG. 12  is a diagram which shows other means to adjust luminance. 
   In all parts (A) to (D) of  FIG. 12  are shown two display electrodes  121 ,  122  which are opposed to each other, with a discharge gap  120  having a width d sandwiched between the two. As compared to the display electrodes of part (A) of  FIG. 12  which are wired in grid form, in the display electrodes of part (B) of  FIG. 12 , the fine metal wires which extend in the grooves in the middle are eliminated. Therefore, the aperture ratio is high and the transmittance of light is high. In the case of part (C) of  FIG. 12 , compared to part (A) of  FIG. 12 , the fine metal wires which are adjacent to the discharge slit and extend laterally are eliminated. In this case, the intensity of a discharge in the discharge gap  120  changes. Therefore, the intensity of luminous light differs and luminance changes. 
   In the case of part (D) of  FIG. 12 , the fine metal wires which extend laterally are eliminated and the display electrodes are in the form of the teeth of a comb. Accordingly, as with the case of part (C) of  FIG. 12 , the discharge intensity of the discharge slit  120  changes, the intensity of luminous light differs and luminance changes. 
   In  FIG. 12 , by way of example, the width d is 400 μm, the wire width of the display electrodes  121 ,  122  is 20 μm, and the size e of the aperture is (425 μm—wire width). 
   As shown in  FIG. 11  and  FIG. 12 , luminance can be adjusted by adjusting the aperture ratio which depends on electrode structures or by adopting electrode structures having different discharge intensities. 
     FIG. 13  is a diagram which shows other means to adjust luminance. 
   In both of parts (A) and (B) of  FIG. 13  are shown two display electrodes  121 ,  122  which are opposed to each other, with a discharge gap  120  having a width d sandwiched between the two. These two display electrodes  121 ,  122  are formed from fine metal wires  127  which are installed in ladder form. 
   Also here, a description will be given by comparing to the electrode structure of part (A) of  FIG. 13 . 
   In part (B) of  FIG. 13 , because the width d of the discharge gap is narrow, a strong electric field is obtained accordingly and light emission can be maintained by a low discharge maintaining voltage. For this reason, when the same voltage is applied, strong luminous light can be obtained by generating a strong discharge and luminance increases. 
   In  FIG. 13 , by way of example, the width d is 400 μm (in the case of part (A) of  FIG. 13  and 320 μm (in the case of part (B) of  FIG. 13 ), the wire width of the display electrodes  121 ,  122  is 20 μm, and the size e of the aperture is (425 μm—wire width). 
   As shown in  FIG. 13 , luminance can also be adjusted by adjusting the discharge maintaining voltage which depends on electrode structures (by adjusting the discharge efficiency when the same voltage is applied) and an image of uniform luminance can be obtained also by performing this adjustment according to curvature. 
     FIG. 14  is a diagram which shows the inner structure of light-emitting lines. 
   As described with reference to  FIG. 2 , the light-emitting line  10  has such a structure that a protective film  12  is formed on the inner surface of a glass tube  11 , and within the glass tube  11  is inserted a boat  13  in which a fluorescent substance layer  14  is formed. 
   In the case of part (A) of  FIG. 14 , a fluorescent substance layer  14  which has a relatively small layer thickness is formed on a boat  13 . In the case of part (B) of  FIG. 14 , a fluorescent substance layer  14  which has a relatively large layer thickness is formed on a boat. 
   Even when other conditions such as electrode structures are all common, relatively weak luminous light L is obtained in the case of part (A) of  FIG. 14  and relatively strong luminous light L is obtained in the case of part (B) of  FIG. 14 . 
   In  FIG. 14 , by way of example, the film thickness of the fluorescent substance layer  14  is 20 μm (in the case of part (A) of  FIG. 14 ) and 30 μm (in the case of part (B) of FIG.  14 ) and the spacing between the boat surface and the tube wall is 700 μm. 
   Luminance which is uniform irrespective of curvature may be obtained by adopting light-emitting lines in which the thickness of the fluorescent substance layer is adjusted according to curvature like this. 
   As with  FIG. 14 ,  FIG. 15  is also a diagram which shows the inner structure of light-emitting lines. 
   Part (A) of  FIG. 15  is the same as part (A) of  FIG. 14 . 
   Compared to part (A) of  FIG. 15 , in part (B) of  FIG. 15 , the boat  13  is formed thick and the fluorescent substance layer  14  is raised upward accordingly, although the layer thickness of the fluorescent substance layer  14  is the same. 
   In  FIG. 15 , by way of example, the film thickness of the fluorescent substance layer  14  is 20 μm and the spacing between the boat surface and the tube wall is 700 μm (in the case of part (A) of  FIG. 15 ) and 560 μm (in the case of part (B) of  FIG. 15 ). 
   Also in the case of part (B) of  FIG. 15 , compared to the case of part (A) of  FIG. 15 , strong luminous light L can be obtained when other conditions are the same, and luminance can be adjusted. 
     FIG. 16  is a block diagram of a plasma tube array and  FIG. 17  is a function block diagram of a display circuit portion of the plasma tube array shown in  FIG. 16 . These  FIGS. 16 and 17  correspond to  FIGS. 5 and 6 , respectively, in the conventional example. 
   Points at which the present invention differs from the conventional technique described with reference to  FIGS. 5 and 6  are described here. 
   Compared to  FIG. 5 , a weighting factor memory  50   b  is added to a display circuit section  100 B of a plasma tube array  100  shown in  FIG. 16 . 
   Tables of correspondences between an address of a display pixel and a weighting factor of a pixel value of the address are stored in this weighting factor memory  50   b.    
   When image data is inputted to the data control circuit  51 , pixel value weighting processing  60 , which is shown in  FIG. 17 , is first executed in this data control circuit  51 . 
   In this pixel value weighting processing  60 , for each of the pixel values constituting an inputted image data, the weighting factor memory  50   b  is referred to by using an address of each pixel value as an index, thereby to find a weighting factor for each pixel value, and each pixel value is weighted by this weighting factor, whereby image data constituted by new pixel values is generated. 
   Weighting factors which correspond to the curvature of the display surface are stored in this weighting factor memory  50   b . Therefore, image data obtained after the pixel value weighting processing  60  is executed becomes image data for which a decrease or increase in luminance by curvature has been corrected. 
   In the data control circuit  51 , processing for image value-light emission pattern conversion  61  is executed for the image data after the pixel value weighting processing  60 , and driving processing  62  is executed by the driver driving circuit  52  and the like. For the processing for pixel value-light emission pattern conversion  61  and the driving processing  62 , have already described with reference to  FIGS. 5 and 6 , their overlapping descriptions are omitted here. 
   As described with reference to  FIGS. 16 and 17 , a display screen of uniform luminance can be obtained also by weighting a pixel value according to the geometric shape of arrayed light-emitting lines.