Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of application Ser. No. 09/614,910 filed on Jul. 12, 2000, now U.S. Pat. No. 6,310,602, which is a continuation of application Ser. No. 08/315,714 filed on Sep. 30, 1994, now U.S. Pat. No. 6,118,429. The contents of application Ser. Nos. 09/614,910 and 08/315,714 are hereby incorporated herein by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a display system for use when display data output by a computer differs in resolution from a liquid crystal display screen, which is to display the display data, used as a display for a personal computer, etc. 
     2. Description of the Related Art 
     A conventional liquid crystal display receives an interface signal containing display data and a timing signal output by a computer, converts the interface signal into a drive signal for the liquid crystal display, and feeds the drive signal into a liquid crystal drive means. The liquid crystal drive means converts the display data contained in the drive signal into a liquid crystal drive voltage corresponding to the display data and outputs the voltage to a liquid crystal panel. When receiving the liquid crystal drive voltage, the liquid crystal panel displays an image. If the input interface signal differs from the liquid crystal panel in resolution, for example, if the resolution of the input interface signal is larger than that of the liquid crystal panel, a part of the display data contained in the input interface signal is deleted to match the resolution of the interface signal with that of the liquid crystal panel, as described in Japanese Patent Laid-Open No. 57-115593. In the conventional example, the display object is limited to characters and space dots around a character are deleted for each kind of character. The part to be deleted needs to be specified for each kind of character. 
     The conventional example applies to characters and is not intended for displaying data other than characters. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide a liquid crystal display system which can accept an interface signal having a resolution different from that of the liquid crystal display for displaying the display data contained in the interface signal regardless of the type of display data. 
     To this end, according to one aspect of the invention, there is provided a method of converting first display data in a raster scan format having a first resolution received from an external system into second display data for a liquid crystal display having a second resolution different from the first resolution, the method comprising the steps of: 
     a) generating data for n vertical or horizontal lines based on specific m vertical or horizontal lines contiguous to each other of the first display data, where m is an integer of two or greater and n is an integer less than m; 
     b) repeating at least one of the following steps c) and d) as many times as required in sequence at different positions on a screen of the liquid crystal display; 
     c) replacing k (n&lt;k≦m) lines of the m vertical or horizontal lines with the n vertical or horizontal lines; and 
     d) adding the n vertical or horizontal lines to the m vertical or horizontal lines. 
     The data conversion means converts display data received from a personal computer or the like into display data using gray scale data so that it matches the resolution of the liquid crystal display. Thus, even display data output by the personal computer or the like assuming an output device having resolution different from that of the liquid crystal display can be displayed on the liquid crystal display. 
     According to another aspect of the invention, there is provided a method of converting first display data in a raster scan format having a first horizontal resolution received from an external system into second display data for a liquid crystal display having a second horizontal resolution smaller than the first horizontal resolution, the method comprising the steps of: 
     a) virtually dividing a set of M contiguous dots on a horizontal line into N equal partitions, where M is an integer of three or greater and N is an integer of two or more, less than M; 
     b) repeating, N times with respect to the N equal partitions, a weighted addition of data values of dots contained in one partition, depending upon what percentage of the partition is occupied by each dot in the partition; 
     c) replacing the M dots with n dots which have the data values of the N partitions resulting from the weighted additions in step b); 
     d) repeating steps a) to c) for different sets of M contiguous dots in sequence at least in a part of one horizontal line; and 
     e) repeating step d) for different horizontal lines in sequence. 
     According to still another aspect of the invention, there is provided a method of converting first display data in a raster scan format having first horizontal resolution received from an external system into second display data for a liquid crystal display having second horizontal resolution larger than the first horizontal resolution, the method comprising the steps of: 
     a) virtually dividing a set of M contiguous dots on a horizontal line into N equal partitions, where M is an integer of two or greater and N is an integer of three or more which is greater than M; 
     b) repeating, N times with respect to the N equal partitions, a weighted addition of one or more data values of dots contained in one partition, depending upon what percentage of each dot contributes in the partition; 
     c) replacing the M dots with N dots which have the data values of the N partitions resulting from the weighted additions in step b); 
     d) repeating steps a) to c) for different sets of M contiguous dots in sequence at least in a part of one horizontal line; and 
     e) repeating step d) for different horizontal lines in sequence. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
     FIG. 1 is a block diagram of a system to which the invention is applied; 
     FIG. 2 is an illustration showing resolutions to which the invention may be applied; 
     FIG. 3 is an illustration of reduction and enlargement by gray scale line replacement and insertion according to the invention; 
     FIG. 4 is an illustration of a method for detecting an area with less display data; 
     FIGS. 5A and 5B are illustrations of gray scale pixel calculation methods; 
     FIG. 6 is an illustration of replacement with a gray scale line using three extraction lines; 
     FIG. 7 is a block diagram showing the configuration of the data conversion section shown in FIG. 1; 
     FIG. 8 is a block diagram showing the configuration of a reduction process section shown in FIG. 11; 
     FIG. 9 is a block diagram of a DAD conversion system; 
     FIG. 10 is an illustration of DAD conversion operation of the system shown in FIG. 9; 
     FIG. 11 is a block diagram showing the configuration of the R data converter shown in FIG. 7; 
     FIG. 12 is a block diagram showing the configuration of the enlargement process section shown in FIG. 11; 
     FIG. 13 is an input/output timing chart for a lateral reduction process; 
     FIG. 14 is an input/output timing chart for a longitudinal reduction process; 
     FIG. 15 is an input/output timing chart for a lateral enlargement process; 
     FIG. 16 is an input/output timing chart for a longitudinal enlargement process; 
     FIG. 17 is a drawing representing the concept of lateral reduction in another embodiment of the invention; 
     FIG. 18 is an illustration of reduction by gray scale replacement related to FIG. 17; 
     FIG. 19 is a drawing representing the concept of lateral enlargement in another embodiment of the invention; 
     FIG. 20 is an illustration of enlargement by gray scale insertion related to FIG. 19; 
     FIG. 21 is an illustration of a method for detecting a line with less display data; 
     FIG. 22 is a block diagram showing the configuration of a data conversion section in another embodiment of the invention; 
     FIG. 23 is a block diagram showing the configuration of the R data converter shown in FIG. 22; 
     FIG. 24 is a block diagram showing the configuration of the reduction process section shown in FIG. 23; 
     FIG. 25 is a block diagram showing the configuration of the enlargement process section shown in FIG. 23; 
     FIG. 26 is an input/output timing chart for the lateral enlargement process; 
     FIG. 27 is an input/output timing chart for the lateral reduction process; 
     FIG. 28 is an input/output timing chart for the longitudinal reduction process; 
     FIG. 29 is an input/output timing chart for the longitudinal enlargement process; 
     FIG. 30 is a conceptual diagram of the reduction process executed in dot units; 
     FIG. 31 is a conceptual illustration of a system to which the invention is applied; and 
     FIG. 32 is a block diagram showing a liquid crystal display unit to which the invention is applied. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the invention will now be described with reference to the accompanying drawings. 
     A first embodiment of a personal computer system to which a liquid crystal display system of the invention is connected will be discussed with reference to FIGS. 1 to  4 ,  5 A- 5 B, and  6  to  16 . 
     FIG. 1 is a block diagram of a personal computer system to which the invention is applied. In the figure, numeral  1  indicates a personal computer or workstation (PC) which contains a central processing unit (CPU)  101 , etc., numeral  2  indicates display data, numeral  3  indicates a timing signal, numeral  4  indicates a data conversion section for converting display data of the PC  1  into a liquid crystal drive signal, numeral  5  indicates liquid crystal display data, numeral  6  indicates a liquid crystal display timing signal, and numeral  7  indicates a liquid crystal panel. The data conversion section  4  and the liquid crystal panel  7  make up a liquid crystal display unit. The data conversion section  4  converts the display data  2  input from the PC  1  into the liquid crystal b display data  5  enlarged or reduced in accordance with the resolution of the liquid crystal panel  7  and generates the liquid crystal display timing signal  6 . The liquid crystal display data  5  and the liquid crystal display timing signal  6  are collectively called a liquid crystal drive signal. The display data is converted into a liquid crystal drive voltage at the liquid crystal panel  7 . In the description to follow, assume that the display data  2  has 4-bit gradation data for each of the primary colors red (R), green (G), and blue (B) and is transferred in series in synchronization with the timing signal  3 . For simplicity, assume that the liquid crystal panel  7  consists of pixels of 1024×768 dots and that the PC  1  outputs a timing signal and display data of 1120×780 dots, which will be hereinafter referred to as display mode  1  throughout the specification, or 640×480 dots, which will be hereinafter referred to as display mode  2  throughout the specification, in response to the display mode. 
     FIG. 2 shows the display modes of the invention. The data conversion section  4  discriminates between the display modes  1  and  2  and executes reduction processes in display mode  1  and enlargement processes in display mode  2  in response to the display mode. 
     Also, assume that the number of colors that can be displayed on the liquid crystal panel  7  is 4096 and that the PC  1  performs so-called raster scanning in which with each pixel represented by 4-bit attribute data (gradation data) for each of R (red), G (green), and B (blue), the data is output for one pixel at a time in sequence from left to right in the horizontal line direction and the operation is repeated in sequence as many times as the number of the horizontal lines from top to bottom. 
     Some operation examples of the data conversion section  4  will be discussed in the first embodiment. 
     As the first operation example, a gray scale line replacement/insertion system will be described with reference to FIG.  3 . 
     FIG. 3 shows gray scale line replacement in display mode  1  and insertion in display mode  2 , wherein numerals  8  and indicate first and second horizontal extraction lines representing horizontal replacement or insertion positions, numerals  10  and  11  indicate first and second vertical extraction lines representing vertical replacement or insertion positions, numeral  12  indicates a horizontal gray scale line resulting from calculating the gray scale for the first and second horizontal extraction lines  8  and  9 , and numeral  13  indicates a vertical gray scale line resulting from calculating the gray scale for the first and second vertical extraction lines  10  and  11 . In display mode  1 , horizontal and vertical gray scale lines are prepared from first and second horizontal and vertical extraction lines and the first and second horizontal extraction lines  8  and  9  are replaced with the horizontal gray scale line  12  and the first and second vertical extraction lines  10  and  11  are replaced with the vertical gray scale line  13 , thereby performing reduction processing. In display mode  2 , a horizontal gray scale line is inserted between the horizontal extraction lines  8  and  9  and a vertical gray scale line is inserted between the vertical extraction lines  10  and  11 , thereby performing enlargement processing. 
     The extraction line positions may be equally spaced as desired, or lines with less display data may be found and selected to be extraction lines. 
     FIG. 4 shows a method of determining the position of a horizontal or vertical extraction line where replacement or insertion is to be made from the display data amount. In the figure, numeral  14  indicates the summation result of the number of pixels displayed in a color different from the background color for each vertical line, numeral  15  indicates the summation result of the number of pixels displayed in a color different from the background color for each horizontal line, and numeral  16  indicates a hatched area containing the positions of horizontal or vertical lines where insertion or deletion can be made, determined from the summation results  14  and  15 . In the example, positions having the smallest amount of display data possible are found for replacement or insertion positions. 
     Further, for a screen with windows displayed, an area outside the window regions may be detected for replacement or insertion positions. 
     FIGS. 5A and 5B show a gray scale pixel calculation method. 
     For example, to prepare a gray scale pixel from two pixels shown in FIG. 5A, the average values of the attributes for R, G, and B may be calculated: 
     
       
           R ′=( R 0+ R 1)/2  
       
     
     
       
           G ′=( G 0+ G 1)/2  Expression 1  
       
     
     
       
           B ′=( B 0+ B 1)/2  
       
     
     This calculation can be repeated as many times as the number of pixels making up one line for calculating a gray scale line. Further, to calculate the gray scale from a number of pixels as shown in FIG. 5B, such as at the intersection of horizontal and vertical lines, the average of the attributes for the four pixels 
       R ′=( R 0+ R 1+ R 2+ R 3)/4 
     
       
           G ′=( G 0+ G 1+ G 2+ G 3)/4  Expression 2  
       
     
     
       
           B ′=( B 0+ B 1+ B 2+ B 3)/4  
       
     
     may be used as gray scale pixel data. 
     When the average values are calculated, fractional digits may occur. It is desirable to handle the fractional digits so that a color different from the background color is output in response to the attribute of the background color. For example, if the background is black (R=0000, G=0000, B=0000), when the average values of R, G, and B are calculated, fractions are rounded up or rounded off, and if the background is white (R=1111, G=1111, B=1111), fractions are rounded down, whereby a color different from the background color can be displayed. If the background color has different attributes for R, G, and B, such as blue (R=0000, G=0000, B=1111), fractions are rounded up when gradation of R or G is calculated, or fractions are rounded down when gradation of B is calculated. 
     Further, another system in which the number of extraction lines in the reduction process is three will be discussed with reference to FIG.  6 . Here, the processing is described by taking only horizontal lines as an example and similar processing is also performed for the vertical lines. 
     In FIG. 6, numerals  17 ,  18 , and  19  indicate first, second, and third extraction lines and numeral  20  indicates a gray scale line found from the average of the display data for the three lines. The second extraction line  18  is replaced with the gray scale data line  20  and the third extraction line  19  is deleted, thereby performing the reduction process. Since similar processing is also performed in the vertical direction, the average of 9-pixel display data may be calculated for the intersection of the extraction lines. The way to find the gray scale data is similar to that in the first operation example. 
     Next, an example of the hardware configuration of the data conversion section  4  for carrying out the first operation example will be discussed with reference to FIGS. 7 and 8. 
     FIG. 7 is an example of the configuration of the data conversion section  4 , wherein numerals  21 ,  22 , and  23  indicate R display data, G display data, and B display data of the display data  2  respectively, numeral  24  indicates an R data converter, numeral  25  indicates a G data converter, numeral  26  indicates a B data converter, numeral  27  indicates B liquid crystal display data, numeral  28  indicates G liquid crystal display data, numeral  29  indicates R liquid crystal display data, numeral  51  indicates a display mode determination section, numeral  52  indicates a display mode signal, numeral  30  indicates a liquid crystal display timing signal generator, and numeral  6  indicates a liquid crystal display timing signal. The display mode determination section  51  determines the display mode from the timing signal  3  and outputs the display mode signal  52 . The data converters  24 ,  25 , and  26  process the R, G, and B display data  21 ,  22 , and  23  respectively in accordance with the resolution represented by the display mode signal  52 . The liquid crystal display timing signal generator  30  generates the liquid crystal display timing signal  6  matched with the output resolution represented by the display mode signal  52  from the timing signal  3 . 
     FIG. 11 is an example of the configuration of the R data converter  24 . The G and B data converters  25  and  26  also each have the same configuration as the R data converter  24 . In FIG. 11, numeral  53  indicates a reduction process section, numeral  54  indicates an enlargement process section, numeral  55  indicates reduced display data, numeral  56  indicates enlarged display data, and numeral  57  indicates resolution switch means. When the display mode signal  52  represents the display mode  1 , the reduction process section  53  converts the R display data  21  into the reduced display data  55 ; at that time, the enlargement process section  54  does not operate. When the display mode signal  52  represents the display mode  2 , the enlargement process section  54  converts the R display data  21  into the enlarged display data  56 ; at that time, the reduction process section  53  does not operate. The resolution switch means  57  is responsive to the display mode signal  52  for outputting the reduced display data  55  when the display mode signal  52  represents the display mode  1  or the enlarged display data  56  when the display mode signal  52  represents the display mode  2  as the R liquid crystal display data  29 . Although the reduction process section  53  and the enlargement process section  54  are provided to support two display modes in the embodiment, additional reduction or enlargement process sections can also be provided for supporting other resolutions. 
     FIG. 8 is one example of the configuration of the reduction process section  53 . Hereinafter, a horizontal row of dots of display data will be referred to as a line. This means that the liquid crystal panel  7  used in the invention consists of 1024 dots×768 lines. 
     In FIG. 8, numeral  32  indicates a latch, numeral  33  indicates preceding dot data, numeral  34  indicates a horizontal operation section, numeral  35  indicates horizontal gray scale data, numeral  36  indicates a horizontal selector, numeral  37  indicates horizontal data, numeral  38  indicates a line memory, numeral  39  indicates a vertical selector, numeral  40  indicates preceding line data, numeral  41  indicates operational horizontal data, numeral  42  indicates a vertical operation section, numeral  43  indicates vertical gray scale data, numeral  44  indicates output horizontal data, and numeral  45  indicates an output selector. The latch  32 , which latches the R display data  21  in synchronization with a dot clock (not shown) provided by the timing signal  3 , outputs the preceding dot data  33  which is display data one dot before the R display data  21 . The horizontal operation section  34  performs an operation on the preceding dot data  33  and the R display data  21  (averaging them) and outputs the horizontal gray scale data  35 . The horizontal selector  36  selects either the horizontal gray scale data  35  or the R display data  21  depending on which position of the liquid crystal panel  7  the R display data  21  is at, and outputs the data  35  or  21  as the horizontal data  37 , as described below in detail. The line memory  38  stores one line of the horizontal data  37  and outputs it as the preceding line data  40  which is data one line before when the display data of the next line is input. The vertical selector  39  outputs the horizontal data  37  to either the vertical operation section  42  as the operational horizontal data  41  or the output selector  45  as the output horizontal data  44  depending on which position of the liquid crystal panel  7  the horizontal data  37  is at, as described below in detail. The vertical operation section  42  performs an operation on the preceding line data  40  and the operational horizontal data  41  and outputs the result as the vertical gray scale data  43 . The output selector  45  outputs either the vertical gray scale data  43  or the output horizontal data  44  depending on which position of the liquid crystal panel  7  the R display data  21  is at, as with the R liquid crystal display data  29 , as described below in detail. 
     FIG. 12 is an example of the configuration of the enlargement process section  54 , wherein numeral  58  indicates a gray scale data frame memory, numeral  59  indicates a display data frame memory, numeral  60  indicates gray scale read data, and numeral  61  indicates display read data. Other components identical with those of the reduction process section  53  previously described with reference to FIG. 8 are denoted by the same reference numerals in FIG.  12 . In FIG. 12, a latch  32  and a horizontal operation section  34  operate like those of the reduction process section  53 . If R display data  21  is data on a first vertical extraction line, a horizontal selector  36  outputs the R display data  21 , then outputs gray scale horizontal data  35  for inserting a vertical line before R display data  21  for the next dot comes. A line memory  38 , a vertical selector  39 , and a vertical operation section  42  operate like those of the reduction process section  53 . Vertical gray scale data  43  for one screen (frame) is stored in the gray scale data frame memory  58  and output horizontal data  44  for one screen (frame) is stored in the display data frame memory  59 . When display data of the next screen (frame) is input, the vertical gray scale read data  60  is read and inserted into any position between the display read data  61  for inserting a horizontal line. 
     Next, the operation related to the reduction process by gray scale replacement will be discussed in detail with reference to FIGS. 1,  7 ,  8 , and  11 . 
     In FIG. 1, the data conversion section  4  converts the display data  2  and the timing signal  3  into the liquid display data  5  and the liquid crystal display timing signal  6  matched with the liquid crystal panel  7  for output. In FIG. 7, the display mode determination section  51  determines the display mode from the timing signal  3  and the display mode signal  52  matched with the resolution of the liquid crystal panel  7  for display. The display mode can be determined by counting the number of clocks of the timing signal  3  or by feeding the display mode signal  52  from an external system without providing the display mode determination section  51 . R, G, and B of the display data  2  are input to the R, C, and B data converters  24 ,  25 , and  26  respectively, which then convert the data into the liquid crystal display data  5  matched with the display mode represented by the display mode signal  52 . The liquid crystal display timing signal generator  30  generates the liquid crystal display timing signal  6  matched with the display mode represented by the display mode signal  52  from the timing signal  3 . 
     The operation of the R data converter  24  for display data conversion will be discussed in detail with reference to FIG.  11 . Each of the G and B data converters  25  and  26  (Q performs an operation similar to that of the R data converter  24 . 
     In FIG. 11, when the display mode signal  52  represents the display mode  1 , the reduction process section  53  operates and generates the reduced display data  55 . When the display mode signal  52  represents the display mode  2 , the enlargement process section  54  operates and generates the enlarged display data  56 . The resolution switch means  57  is responsive to the display mode signal  52  for selecting and outputting the reduced display data  55  in the display mode  1  or the enlarged display data  56  in the display mode  2 . As described above, additional reduction and enlargement process sections can be provided to make up a data conversion section which supports other resolutions. 
     The operation of the reduction process section  53  will be discussed in detail with reference to FIGS. 8,  13 , and  14 . In FIG. 8, since the latch  32  latches input R display data  21  according to a dot clock, the data output by the latch  32  becomes the preceding dot display data  33  which is the data one dot before the R display data  21 . The horizontal operation section  34  performs an operation on the preceding dot display data  33  and the R display data  21  to generate gray scale data, and outputs it as the horizontal gray scale data  35 . If the R display data  21  is data on a first vertical extraction line, the horizontal selector  36  outputs neither the horizontal gray scale data  35  nor the R display data  21 ; if it is data on a second vertical extraction line, the horizontal selector  36  outputs the horizontal gray scale data  35 ; if it is not data on the first or second vertical extraction line, the horizontal selector  36  outputs the R display data  21  as the horizontal data  37 . 
     The horizontal data  37  for one line is stored in the line memory  38 , and is read out when horizontal data  37  for the next line is input. Therefore, the data output by the line memory  38  becomes the preceding line display data  40  which is one line before the horizontal data  37 . If the horizontal data  37  is data on a first horizontal extraction line, the vertical selector  39  does not output the data to the vertical operation section  42  or the output selector  45 ; if it is data on a second horizontal extraction line, the vertical selector  39  outputs the data to the vertical operation section  42  as the operational horizontal data  41 ; if it is not data on the first or second vertical extraction line, the vertical selector  39  outputs the data to the output selector  45  as the output horizontal data  44 . The vertical operation section  42  performs an operation on the preceding line display data  40  and the operational horizontal data  41  to generate gray scale data, and outputs it as the vertical gray scale data  43 . If the horizontal data  37  is data on the first horizontal extraction line, the output selector  45  outputs neither the vertical gray scale data  43  nor the output horizontal data  44 ; if it is data on the second horizontal extraction line, the output selector  45  outputs the vertical gray scale data  43 ; if it is not data on the first or second horizontal extraction line, the output selector  45  outputs the output horizontal data  44 . The reduction process by gray scale replacement shown in FIG. 3 is now complete. 
     FIG. 13 is an input/output timing chart for the lateral reduction process in the reduction process section  53 . 
     In the figure, numeral  101  indicates the input timing of the R display data  21 , numeral  102  indicates the output timing for the preceding dot data  33 , and numeral  103  indicates the output timing for the horizontal gray scale data  35 , showing that the result of dividing the sum of the R display data  21  and the preceding dot data  33  by two is output as the horizontal gray scale data  35 . Numeral  104  indicates the select signal timing of the horizontal selector  36  and numeral  105  indicates the output timing of horizontal data  37 , showing that the select signal  104  is set to 1 at the position next to the first vertical extraction line  10  shown in FIG. 3, outputting the horizontal gray scale data  35 . 
     Numeral  106  indicates the timing of a synchronous clock contained in the liquid crystal timing signal  6  and numeral  107  indicates the timing of data displayed on the liquid crystal panel  7 . X 2  data is deleted by synchronizing the horizontal data timing  105  with the synchronous clock timing 106 for stopping the clock finally corresponding to the position of the first vertical extraction line  10 . 
     FIG. 14 is an input/output timing chart for the longitudinal reduction process of the reduction process section  53 . 
     In the figure, numeral  108  indicates the line output timing for the horizontal data  37 , numeral  109  indicates the output timing for the preceding line signal  40  output by the line memory  38 , numeral  110  indicates the output timing for the vertical gray scale data  43  generated by performing an operation on the output of the line memory  38  and the horizontal data  37 , and numeral  112  indicates the output timing of the reduced display signal  55  output from the output selector  45 . L 0  and L 1  denote data for the first line and data for the second line respectively; L 0  and L 1  are averaged to generate the vertical gray scale data  43 . This also applies to the second line, third line, and later. Numeral  111  indicates a select signal for the output selector  45 , which allows the vertical gray scale data  43  to be output on the line next to the first horizontal extraction line  8  shown in FIG.  3 . Numeral  112  indicates the output timing of the reduced display signal  55 , numeral  113  indicates the output timing of a horizontal synchronizing signal contained in the liquid crystal display timing signal  6 , and numeral  114  indicates the timing of display data actually displayed. Although the output timing  112  of the output selector  45  follows the select signal timing  111 , L 1  is not displayed as shown in  114  because the actual horizontal synchronizing signal is as shown in  113  . 
     Next, the enlargement process by gray scale insertion will be discussed in detail with reference to FIGS. 12,  15 , and  16 . 
     In FIG. 12, the latch  32  and the horizontal operation section  34  operate like those of the reduction process section  53 . If R display data  21  is data on a first vertical extraction line, the horizontal selector  36  outputs the R display data  21 , then outputs gray scale horizontal data  35  for inserting a vertical line before R display data  21  for the next dot comes. The line memory  38 , the vertical selector  39 , and the vertical operation section  42  operate like those of the reduction process section  53 . Vertical gray scale data  43  for one screen (frame) is stored in the gray scale data frame memory  58  and output horizontal data  44  for one screen (frame) is stored in the display data frame memory  59 . When display data for the next screen (frame) is input, the vertical gray scale read data  60  is read and inserted into any position between the display read data  61  for inserting a horizontal line. 
     FIG. 15 is an input/output timing chart of the lateral enlargement process for the enlargement process section  54 . 
     In the figure, numeral  115  indicates the input timing for the R display data  21 , numeral  116  indicates the output timing for the preceding dot data  33 , and numeral  117  indicates the output timing for the horizontal gray scale data  35 , showing that the result of dividing the sum of the R display data  21  and the preceding dot data  33  by two is output as the horizontal gray scale data  35 . Numeral  118  indicates the select signal timing for the horizontal selector  36 , numeral  119  indicates the output timing for the horizontal data  37 , and numeral  120  indicates the timing of a synchronous clock contained in the liquid crystal display timing signal 6, showing that the select signal  104  is set to 1 at the position next to the first vertical extraction line  10  shown in FIG. 3, outputting the horizontal gray scale data  35 . The period of only the synchronous clock at the time is doubled and while 1-dot data is input, 2-dot data of the horizontal gray scale data  35  and the R display data  21  is output. 
     FIG. 16 is an input/output timing chart of the longitudinal enlargement process for the enlargement process section  54 . 
     In the figure, numeral  1119  indicates the output timing for the horizontal data  37  for each line, numeral  1120  indicates the output timing for the preceding line data  40  for each line output from the line memory  38 , and numeral  121  indicates the output timing of vertical gray scale data  43  for each line, showing that the vertical gray scale data  43  is the result of dividing by two the sum of the horizontal data  37  and the preceding line data  40  which is the data one line before the horizontal data  37 . Numeral  122  indicates a timing signal representing the position into which the vertical gray scale data  43  is inserted, numeral  123  indicates a horizontal synchronizing signal contained in the liquid crystal display timing signal  6 , and numeral  124  indicates the timing for each line actually displayed. When the vertical gray scale data is inserted, the vertical gray scale data insertion timing  122  is set to “1” on the line next to the first horizontal extraction line  8 . At this time, the period of the synchronous clock is doubled and while 1-line data is input, 2-line data is output. For the first one of these two lines, the vertical gray scale data is selectively output from the gray scale data frame memory  58  and for the second line, the horizontal data is selectively output from the display data frame memory  59 . 
     When a number of insertion lines are equally spaced, for example, when a gray scale data line is to be inserted every n lines, (n+1) line memories are provided for storing gray scale data to be inserted and line data. When the next data is input, the (n+1)-line data containing the gray scale line data is read out while n line data is stored, whereby a horizontal line can be inserted without providing the frame memories. 
     The data conversion section  4  which performs the processing may be software which uses the CPU  101 , hardware, may exist in the PC  1 , or may be contained in the liquid crystal pane  7 . 
     As the second operation example of the data conversion section  4 , a system of converting horizontal resolution with low-pass filters will be described with reference to FIG.  9 . 
     FIG. 9 shows the configuration of an R data converter  24  with a low-pass filter, wherein numeral  46  is a D/A converter, numeral  47  indicates analog R display data, numeral  48  indicates a low-pass filter, numeral  49  indicates smoothed R display data, numeral  50  indicates an A/D converter, and numeral  51  indicates a display mode determination section which performs the same operation as that described above. The D/A converter  46  immediately converts digital output R display data  21  into analog R display data  47  and outputs the analog R display data  47  to the low-pass filter  48  which then smoothes the data  47  to generate the smoothed R display data  49 . Lastly, the smoothed R display data is restored to a digital signal by the A/D converter  50  using the liquid crystal display timing signal  6  matched with the resolution of the liquid crystal display. If the liquid crystal display timing signal  6  has a higher frequency than the input timing signal  3 , the enlargement process is executed; if the former has lower frequency than the latter, the reduction process is executed. 
     FIG. 10 shows a signal conversion example of display data in the enlargement process. 
     Since the liquid crystal display timing signal  6  having higher frequency than the input timing signal  3  is used, enlarged R liquid crystal display data  29  is generated. 
     We have discussed the enlargement/reduction techniques as execution of the enlargement or reduction process so that the display data output from the PC  1  is made the same as the liquid crystal panel in resolution directly, but a technique which employs step-by-step execution of the enlargement or reduction process may be used. For example, to convert display data represented by 640×480 dots into 1120×780 dots, first the display data is first enlarged to 1280×960 dots, which is twice 640×480 dots, then the enlarged displayed data is reduced to 1120×780 dots. If an attempt is made to enlarge the display data directly to 1120×780 dots, it takes time because of a large number of insertion lines. 
     However, it does not take much time to enlarge the display data to 1280×960 equivalent to a double of 640×480 dots because of simple processing, and then only a few lines need to be removed. Therefore, the entire processing can be performed at high speed. 
     In contrast, if the resolution of the liquid crystal panel  7  in FIG. 1 is 640×480 dots and display data of 1120×780 dots is output from the PC  1 , the enlargement process can be simply the reverse of the reduction process, which makes the processing fast. 
     In the invention, how the resolution should be adjusted can be determined automatically by providing means for determining what resolution the display data supplied to the liquid crystal display has, such as means for determining resolution from the timing signal input from the computer. 
     Another embodiment of a personal computer system to which a liquid crystal display system of the invention is connected will be discussed with reference to FIGS. 17 to  30 . 
     The system configuration of another embodiment is the same as that shown in FIG. 1 except for the data conversion section  4 . 
     Some operation examples of the data conversion section  4  will be discussed in another embodiment. 
     As the first operation example, a gradation integration/reduction system will be described with reference to FIG.  17 . 
     FIG. 17 shows the concept of the lateral reduction method in display mode  1  (1120×780 dots). Here, the reduction of five pixels to four pixels is discussed, and FIG. 17 represents R, G, or B color data. 
     In FIG. 17, numeral  8  indicates 5-pixel display data and numeral  9  indicates 4-pixel display data after reduction. The vertical axis is entered with 1 as the highest intensity and 0 as the lowest intensity and the horizontal axis is entered as pixel positions. To reduce the 5-pixel data  8  to the 4-pixel data  9 , the 5-pixel width is virtually quartered, namely, the 1-pixel width is widened one-quarter and display data of five-quarter pixel width is converted into display data of 1-pixel width. Therefore, the calculation expression for the 1-pixel display data is 
     
       
           X (0,0)′=( X (0,0)×4 +X (0,1)×1)/5  
       
     
     
       
           X (0,1)′=( X (0,1)×3 +X (0,2)×2)/5  
       
     
     
       
           X (0,2)′=( X (0,2)×2 +X (0,3)×3)/5  
       
     
     
       
           X (0,3)′=( X (0,3)×1 +X (0,4)×4)/5  Expression 3  
       
     
     where X (0, 0) to X (0, 4) are gray scale data for the first to fifth pixels before reduction and X (0, 0)′ to X (0, 3)′ are gray scale data for the first to fourth pixels after reduction, wherein the first digit represents the line number and the second digit represents the pixel number. That is, X (0, 0) is gray scale data for the first pixel of the first line and X (0, 1) is gray scale data for the second pixel of the first line. Since the description assumes that 1120 pixels are reduced to 1024 pixels, 35 pixels are reduced to 32 pixels from 1024/1120=32/35. The calculation expression is: 
     
       
           X (0,0)′=( X (0,0)×32 +X (0,1)×3)/35  
       
     
     
       
           X (0,1)′=( X (0,1)×29+ X (0,2)×6)/35  
       
     
     
       
           X (0,2)′=( X (0,2)×26+ X (0,3)×9)/35  
       
     
     
       
           X (0,3)′=( X (0,3)×23+ X (0,4)×12)/35  
       
     
     
       
           X (0,4)′=( X (0,4)×20+ X (0,5)×15)/35  
       
     
     
       
           X (0,5)′=( X (0,5)×17+ X (0,6)×18)/35  
       
     
     
       
           X (0,6)′=( X (0,6)×14+ X (0,7)×21)/35  
       
     
     
       
           X (0,7)′=( X (0,7)×11+ X (0,8)×24)/35  
       
     
     
       
           X (0,8)′=( X (0,8)×8 X (0,9)×27)/35  
       
     
     
       
           X (0,9)′=( X (0,9)×5+ X (0,10)×30)/35  
       
     
     
       
           X (0,10)′=( X (0,10)×2+ X (0,11)×32+ X (0,12)×1)/35  
       
     
     
       
           X (0,11)′=( X (0,12)×31+ X (0,13)×4)/35  
       
     
     
       
           X (0,12)′=( X (0,13)×28+ X (0,14)×7)/35  
       
     
     
       
           X (0,13)′=( X (0,14)×25+ X (0,15)×10)/35  
       
     
     
       
           X (0,14)′=( X (0,15)×22+ X (0,16)×13)/35  
       
     
     
       
           X (0,15)′=( X (0,16)×19+ X (0,17)×16)/35  
       
     
     
       
           X (0,16)′=( X (0,17)×16+ X (0,18)×19)135 X (0,17)′=( X (0,18)×13+ X (0,19)×22)/35  
       
     
     
       
           X (0,18)′=( X (0,19)×10+ X (0,20)×25)/35  
       
     
     
       
           X (0,19)′=( X (0,20)×7+ X (0,21)×28)/35  
       
     
     
       
           X (0,20)′=( X (0,21)×4+ X (0,22)×31)/35  
       
     
     
       
           X (0,21)′=( X (0,22)×1+ X (0,23)×32+ X (0,24)×2)/35  
       
     
     
       
           X (0,22)′=( X (0,24)×30+ X (0,25)×5)/35  
       
     
     
       
           X (0,23)′=( X (0,25)×27+ X (0,26)×8)/35  
       
     
     
       
           X (0,24)′=( X (0,26)×24+ X (0,27)×11)/35  
       
     
     
       
           X (0,25)′=( X (0,27)×21+ X (0,28)×14)/35  
       
     
     
       
           X (0,26)′=( X (0,28)×18+ X (0,29)×17)/35  
       
     
     
       
           X (0,27)′=( X (0,29)×15+ X (0,30)×20)/35  
       
     
     
       
           X (0,28)′=( X (0,30)×12+ X (0,31)×23)/35  
       
     
     
       
           X (0,29)′=( X (0,31)×9+ X (0,32)×26)/35  
       
     
     
       
           X (0,30)′=( X (0,32)×6+ X (0,33)×29)/35  
       
     
     
       
           X (0,31)′=( X (0,33)×3+ X (0,34)×32)/35  Expression 4  
       
     
     where X (0, 0) to X (0, 34) are gray scale data for the first to 35th pixels before reduction and X (0, 0)′ to X (0, 31)′ are gray scale data of the first to 32nd pixels after reduction. Similar operations can also be performed in the longitudinal direction. However, to use a similar method for longitudinal processing, a memory for a plurality of lines would be required, which would increase the size of the circuit. Thus, the following processing can also be carried out so as not to increase the circuit scale. 
     FIG. 18 shows reduction by gray scale replacement wherein a longitudinal reduction method is also shown. 
     To reduce 780 lines to 768 lines in the longitudinal direction, the deletion of 12 lines is required. In FIG. 18, numeral  210  indicates an extraction line to be deleted and numeral  211  indicates a replacement line after reduction. Longitudinal reduction is executed by replacing the extraction line  210  and the following line with the replacement line  211  which is the gray scale of the extraction line  210  and the following line. Therefore, pixels, other than the replacement line  211 , to which “′” is attached are pixels reduced using Expression 4 in the lateral direction, and to process the extraction line  210  and the following line using Expression 4 and average these two lines, the replacement line  211  is 
     
       
           X (2,0)′=( X (2,0)×32+ X (3,0)×32+ X (2,1)×3+ X (3,1)×3)/70  
       
     
     
       
           X (2,1)′=( X (2,1)×29+ X (3,1)×29+ X (2,2)×6+ X (3,2)×6)/70  
       
     
     
       
           X (2,2)′=( X (2,2)×26+ X (3,2)×26+ X (2,3)×9+ X (3,3)×9)/70  
       
     
     
       
           X (2,3)′=( X (2,3)×23+ X (3,3)×23+ X (2,4)×12+ X (3,4)×12)/70  
       
     
     
       
           X (2,4)′=( X (2,4)×20+ X (3,4)×20+ X (2,5)×15+ X (3,5)×15)/70  
       
     
     
       
           X (2,5)′=( X (2,5)×17+ X (3,5)×17+ X (2,6)×18+ X (3,6)×18)/70  
       
     
     
       
           X (2,26)′=( X (2,28)×18+ X (3,28)×18+ X (2,29)×17 +X (3,29)×17)/70  
       
     
     
       
           X (2,27)′=( X (2,29)×15+ X (3,29)×15+ X (2,30)×20 +X (3,30)×20)/70  
       
     
       X (2,28)′=( X (2,30)×12+ X (3,30)×12+ X (2,31)×23 +X (3,31)×23)/70 
     
       
           X (2,29)′=( X (2,31)×9+ X (3,31)×9+ X (2,32)×26+ X (3,32)×26)/70  
       
     
     
       
           X (2,30)′=( X (2,32)×6+ X (3,32)×6+ X (2,33)×29+ X (3,33)×29)/70  
       
     
     
       
           X (2,31)′=( X (2,33)×3+ X (3,33)×3+ X (2,34)×32+ X (3,34)×32)/70  Expression 5  
       
     
     Data for the two lines (third and fourth lines) of the extraction lines is calculated. This method would require a 1-line memory, as described below in detail. 
     FIG. 19 shows the concept for the lateral enlargement method in display mode  2  (640×480 dots). Here, enlargement of four pixels to five pixels is discussed. 
     In FIG. 19, numeral  212  indicates 4-pixel display data and numeral  213  indicates 5-pixel display data after enlargement. The vertical axis is entered with 1 as the highest intensity and 0 as the lowest intensity and the horizontal axis is entered as pixel positions. To enlarge the 4-pixel data  212  to the 5-pixel data  213 , the 4-pixel width is divided into five equal parts, namely, the 1-pixel width is narrowed by one-fifth and display data of four-fifth pixel width is converted into display data of 1-pixel width. Therefore, the 1-pixel display data is expressed by 
     
       
           X (0,0)′=( X (0,0)×4)/4  
       
     
     
       
           X (0,1)′=( X (0,0)×1+ X (0,1)×3)/4  
       
     
     
       
           X (0,2)′=( X (0,1)×2+ X (0,2)×2)/4  
       
     
     
       
           X (0,3)′=( X (0,2)×3+ X (0,3)×1)/4  
       
     
     
       
           X (0,4)′=( X (0,3)×4)/4  Expression 6  
       
     
     where data to which″′″ is attached is gray scale data after processing. In fact, to enlarge 640 pixels to 1024 pixels, five pixels are enlarged to eight pixels from 1024/640=8/5. This is expressed by 
     
       
           X (0,0)′=( X (0,0)×5)/5  
       
     
     
       
           X (0,1)′=( X (0,0)×3+ X (0,1)×2)/5  
       
     
     
       
           X (0,2)′=( X (0,1)×5)/5  
       
     
     
       
           X (0,3)′=( X (0,1)×1+ X (0,2)×4)/5  
       
     
     
       
           X (0,4)′=( X (0,2)×4+ X (0,3)×1)/5  
       
     
     
       
           X (0,5)′=( X (0,3)×5)/5  
       
     
     
       
           X (0,6)′=( X (0,3)×2+ X (0,4)×3)/5  
       
     
     
       
           X (0,7)′=( X (0,4)×5)/5  Expression 7  
       
     
     Like the reduction process, to use a similar method for longitudinal processing, a memory for a plurality of lines would be required, which would increase the size of the circuit. Thus, the following processing can also be performed so as not to increase the circuit scale. 
     FIG. 20 shows enlargement by gray scale insertion wherein a longitudinal enlargement method is also shown. To enlarge 480 lines to 768 lines in the longitudinal direction, the insertion of 288 lines is required. In FIG. 20, numerals  214  and  215  indicate extraction lines to represent the insertion position and numeral  216  indicates an insertion line after enlargement. Longitudinal enlargement is executed by inserting the insertion line  216  which is a gray scale for the extraction lines  214  and  215  between the extraction lines  214  and  215 . Therefore, the pixels, other than the insertion line  216 , to which″′″ is attached are pixels enlarged using Expression 4 in the lateral direction, and to process the extraction lines  214  and  215  using Expression 4 and average these two lines, the insertion line  216  is 
     
       
           X (3,0)′=( X (2,0)×5+ X (3,0)×5)/10  
       
     
     
       
           X (3,1)′=( X (2,0)×3+ X (3,0)×3+ X (2,1)×2+ X (3,1)×2)/10  
       
     
     
       
           X (3,2)′=( X (2,1)×5+ X (3,1)×5)/10  
       
     
     
       
           X (3,3)′=( X (2,1)×1+ X (3,1)×1+ X (2,2)×4+ X (3,2)×4)/10  
       
     
     
       
           X (3,4)′=( X (2,2)×4+ X (3,2)×4+ X (2,3)×1+ X (3,3)×1)/10  
       
     
     
       
           X (3,5)′=( X (2,3)×5+ X (3,3)×5)/10  
       
     
     
       
           X (3,6)′=( X (2,3)×2+ X (3,3)×2+ X (2,4)×3 + X (3,4)×3)/10  
       
     
     
       
           X (3,7)′=( X (2,4)×5+ X (3,4)×5)/10  Expression 8  
       
     
     Data for two lines is calculated. The calculation is executed for each color, thereby converting the display data. 
     As described above, the calculation is executed separately for each of R, G, and B. At that time, fractional digits may occur. To clarify the difference between the background color and text and graphics colors, it is desirable to handle the fractional digits so that a color different from the background color is output in response to the attributes of the background color. For example, if the background is black (R=0000,G=0000,B=0000), when the average values of R, G, and B are calculated, fractions are rounded up or rounded off, and if the background is white (R=1111, G=1111, B=1111), fractions are rounded down, whereby a color different from the background color can be displayed. If the background color has different R, G, and B attributes such as blue (R=0000, G=0000,B=1111), fractions are rounded up when gradation of R or G is calculated, or fractions are rounded down when gradation of B is calculated. 
     The extraction line positions in longitudinal reduction or enlargement may be equally spaced as desired, or lines with less display data may be found and set to extraction lines. 
     Like FIG. 4, FIG. 21 shows a method of determining the position of a horizontal or vertical extraction line where replacement or insertion is to be made from the display data amount, wherein only a horizontally extending area is detected. In FIG. 21, numeral  217  indicates the summation result of the number of pixels displayed in a color different from the background color for each horizontal line and numeral  218  indicates positions of horizontal lines where insertion or deletion can be made, determined from the summation result  217 . In the example, positions having as little display data as possible are found for replacement or insertion positions. For a screen with windows displayed, an area outside the window regions may be detected for replacement or insertion positions. 
     Next, an example of the hardware configuration of the data conversion section  4  for carrying out the first operation example shown in FIG. 17 will be discussed. 
     FIG. 22 is a configuration example of the data conversion section  4 , wherein numerals  219 ,  220 , and  221  indicate R display data, G display data, and B display data of display data  2  respectively, numeral  222  indicates an R data converter, numeral  223  indicates a G data converter, numeral  224  indicates a B data converter, numeral  225  indicates R liquid crystal display data, numeral  226  indicates G liquid crystal display data, numeral  227  indicates B liquid crystal display data, numeral  81  is a display position determination section, numeral  82  is a lateral display position signal, numeral  83  is a longitudinal display position signal, numeral  228  indicates a display mode determination section, numeral  229  indicates a display mode signal, and numeral  230  indicates a liquid crystal display timing signal generator. The display position determination section  81  determines the display position of each pixel of the display data  2  from a timing signal  3  and outputs the lateral position as the lateral display position signal  82  and the longitudinal position as the longitudinal display position signal  83 . The display mode determination section  228  determines the display mode from the timing signal  3  and outputs the display mode signal  229 . The data converters  222 ,  223 , and  224  process the R, G, and B display data  219 ,  220 , and  221  respectively in accordance with the resolution represented by the display mode signal  229  and the display position indicated by the lateral and longitudinal display position signals  82  and  83 . The liquid crystal display timing signal generator  230  generates a liquid crystal display timing signal  6  matched with the output resolution represented by the display mode signal  229  from the timing signal  3 . 
     FIG. 23 is an example of the configuration of the R data converter  222 . The G and B data converters  223  and  224  also each have the same configuration as the R data converter  24 . 
     In FIG. 23, numeral  231  indicates a reduction process section, numeral  232  indicates an enlargement process section, numeral  233  indicates reduced display data, numeral  234  indicates enlarged display data, and numeral  235  indicates a resolution switch means. When the display mode signal  229  represents the display mode  1 , the reduction process section  231  converts the R display data  219  into the reduced display data  233  in response to the lateral display position signal  82  and longitudinal display position signal  83 ; at that time, the enlargement process section  232  does not operate. When the display mode signal  229  represents the display mode  2 , the enlargement process section  232  converts the R display data  219  into the enlarged display data  234  in response to the lateral display position signal  82  and longitudinal display position signal  83 , at that time, the reduction process section  231  does not operate. The resolution switch means  235  is responsive to the display mode signal  229  for outputting the reduced display signal  233  when the signal  229  represents the display mode  1  or the enlarged display signal  234  when the signal  229  represents the display mode  2  as the R liquid crystal display signal  225 . Although the reduction process section  231  and the enlargement process section  232  are provided to support two display modes in the embodiment, additional reduction or enlargement process sections can also be provided for supporting other resolutions. 
     FIG. 24 is one example of the configuration of the reduction process section  231 . As described above, a horizontal row of pixels of display data is referred to as a line. This means that the liquid crystal panel  7  used in the invention consists of 1024 pixels×768 lines and that the display mode  1  provides 1120 pixels×780 lines. 
     In FIG. 24, numeral  236  indicates a pre-preceding dot data latch, numeral  237  indicates a preceding dot data latch, numeral  238  indicates pre-preceding dot data, numeral  239  indicates preceding dot data, numeral  240  indicates a lateral operation section, numeral  241  indicates laterally reduced data, numeral  242  indicates a line memory, numeral  243  indicates preceding line data, numeral  244  indicates a longitudinal operation section, numeral  245  indicates longitudinal gray scale data and numeral  246  indicates an output selector. The preceding dot data latch  237 , which latches the R display data  219  in response to a dot clock, outputs the preceding dot data  239  which is display data one pixel before the R display data  219 . The pre-preceding dot data latch  236 , which latches the preceding dot data  239  in response to a dot clock, outputs the pre-preceding dot data  238  which is display data two pixels before the R display data  219 . The lateral operation section  240  performs an operation on the R display data  219  and the preceding dot data  239 , the pre-preceding dot data  238  according to Expression 4 in response to the lateral display position signal  82  depending on which pixel position of the liquid crystal panel  7  the R display data  219  is at, and outputs the result as the laterally reduced data  241 , as described below in detail. The line memory  242  stores one line of the laterally reduced data  241  and outputs as the preceding line data  243  which is data one line before when the R display data  219  of the next line is input. The longitudinal operation section  244  performs an operation on the laterally reduced data  241  and the preceding line data  243  in response to the longitudinal display position signal  83  depending on which line position of the liquid crystal panel  7  the R display data  219  is at, and outputs the result as the longitudinal gray scale data  245 , as described below in detail. The output data selector  246  selects the laterally reduced data  241  or the longitudinal gray scale data  245  and outputs or does not output them in response to the longitudinal display position signal  83 , as described in detail below. 
     FIG. 25 is an example of the configuration of the enlargement process section  232 , wherein numeral  247  indicates laterally enlarged data, numeral  248  indicates a gray scale data frame memory, numeral  249  indicates a display data frame memory, numeral  250  indicates read insertion data, and numeral  251  indicates read display data. Other components identical with those of the reduction process section  231  previously described with reference to FIG. 24 are denoted by the same reference numerals in FIG.  25 . 
     In FIG. 25, a preceding dot data latch  237  operates like that of the reduction process section  231 . The lateral operation section  240  performs an operation according to Expression 7 in response to the lateral display position signal  82  and outputs the result as the laterally enlarged data  247 . A line memory  242  and a longitudinal operation section  244  operate like those of the reduction process section  231 . The gray scale data frame memory  248  stores longitudinal gray scale data  245  for one frame and the display data frame memory  249  stores laterally enlarged data  247  for one frame. When display data of the next frame is input, the read insertion data  250  is read and inserted into any position between the read display data  251  in response to the longitudinal display position signal  83  for performing enlargement processes. 
     Next, the operation related to the reduction process according to the invention will be discussed in detail. 
     In FIG. 1, the data conversion section  4  converts the display data  2  and the timing signal  3  into the liquid display data  5  and the liquid crystal display timing signal  6  matched with the liquid crystal panel  7  for output. In FIG. 22, the display position determination section  81  determines the position at which display data is to be displayed from the timing signal  3  and generates the lateral display position signal  82  and the longitudinal display position signal  83 . The lateral display position can be determined by counting liquid crystal display clock pulses (dot clock pulses) of the timing signal  3  and the longitudinal display position can be determined by counting liquid crystal horizontal clock pulses (line clock pulses) of the timing signal  3 . The display mode determination section  228  determines the display mode from the timing signal  3  and the display mode signal  229  matched with the resolution of the liquid crystal panel  7  for display. To determine the display mode, the number of lateral (horizontal) dots can be determined by counting the number of liquid crystal display clocks in one period of the liquid crystal horizontal clock of the timing signal  3  and the number of longitudinal (vertical) lines can be determined by counting the number of liquid crystal horizontal synchronizing signal periods in one period of liquid crystal vertical synchronizing signal. The display mode signal  229  can also be fed from an external system without providing the display mode determination section  228 . 
     The R, G, and B for the display data  2  are input to the R, G, and B data converters  222 ,  223 , and  224  respectively, which then convert the data into the liquid crystal display data  5  matched with the display mode represented by the display mode signal  229 . The liquid crystal display timing signal generator  230  generates the liquid crystal display timing signal  6  matched with the display mode represented by the display mode signal  229  from the timing signal  3 . 
     The operation of the R data converter  222  for display data conversion will be discussed in detail with reference to FIG.  23 . Each of the G and B data converters  223  and  224  performs similar operations to that of the R data converter  222 . 
     In FIG. 23, when the display mode signal  229  represents the display mode  1 , the reduction process section  231  operates and generates the reduced display data  233  in response to the lateral display position signal  82  and the longitudinal display position signal  83 . When the display mode signal  229  represents the display mode  2 , the enlargement process section  232  operates and generates the enlarged display data  234  in response to the lateral display position signal  82  and the longitudinal display position signal  83 . The resolution switch means  235  is responsive to the display mode signal  229  for selecting and outputting the reduced display data  233  in the display mode  1  or the enlarged display data  234  in the display mode  2 . As described above, additional reduction and enlargement process sections can be provided to make up a data conversion section which supports every resolution. 
     The operation of the reduction process section  231  will be discussed in detail with reference to FIGS. 24,  27 , and  28 . In FIG. 24, the preceding dot data latch  237 , which latches R display data  219  according to a dot clock, outputs the preceding dot display data  239  which is the data one dot before the R data  219 . The pre-preceding dot data latch  236 , which latches the preceding dot data  239  according to a dot clock, outputs the pre-preceding dot data  238  which is the data two dots before the R data  219 . The lateral operation section  240  comprises an adder, multiplier, and divider. When the R display data  219  indicated by the lateral display position signal  82  is at the positions X ( 0 ,  1 ) to X ( 0 ,  10 ), X ( 0 ,  13 ) to X ( 0 ,  22 ), and X ( 0 ,  25 ) to X ( 0 ,  34 ) shown in Expression 4, the lateral operation section  240  performs an operation on the R display data  219  and the preceding dot data  239 ; when the R display data  219  is at the positions X ( 0 ,  12 ) and X ( 0 ,  24 ), the lateral operation section  240  performs an operation on the R display data  219 , the preceding dot data  239 , and the pre-preceding dot data  238 ; and when the R display data  219  is at the positions X ( 0 ,  0 ), X ( 0 ,  11 ), and X ( 0 ,  23 ), the lateral operation section  240  does not output any data, thereby executing the operation shown in Expression  4 . Lateral reduction can be accomplished by repeating similar calculations in 35-dot units. When the position of the R display data  219  indicated by the longitudinal display position signal  83  is the line next to the extraction line  210  shown in FIG. 18, the longitudinal operation section  244  performs an operation on the laterally reduced data  241  and the preceding line data  243 ; otherwise, the longitudinal operation section  244  does not operate. When the position of the R display data  219  indicated by the longitudinal display position signal  83  is the extraction line  210  shown in FIG. 18, the output data selector  246  does not output display data; when the position is the line next to the extraction line  210  shown in FIG. 18, the output data selector  246  outputs the longitudinal reduced data  245 ; otherwise, it outputs the laterally reduced data  241 . 
     FIG. 27 is an input/output timing chart for the lateral reduction process for the reduction process section  231 . 
     In the figure, numeral  2102  indicates the input timing for the R display data  219 , numeral  2103  indicates the output timing of preceding dot data  239 , numeral  2104  indicates the output timing for the pre-preceding dot data  238 , numeral  2105  indicates the output timing for the synchronous clock contained in the liquid crystal display timing signal  6 , numeral  2106  indicates the output timing of laterally reduced data  241 , and numeral  2107  indicates hatched data on which a lateral operation is to be performed. Each number following X represents the lateral display position (dot position) 0 to 34. Each number to which “′” is suffixed, shown in the output timing  2104  of the laterally reduced data  241  represents the display position after lateral reduction. For example, the first dot X 0 ′ of the laterally reduced data  241  is the result of performing an operation on X 0  and X 1  shown as hatched data  2107 , and X 10   is the result of performing an operation on X 10 , X 11 , and X 12 . The operation is performed according to Expression 4 in response to the lateral display position signal  82 . The clock at the positions of X 0 , X 11 , and X 23  of the R display data  219  is stopped and laterally reduced data  241  is output in synchronization with it, thereby deleting 3-dot data. 
     FIG. 28 is an input/output timing chart for the longitudinal reduction process for the reduction process section  231 . 
     In the figure, numeral  2108  indicates the line output timing for the laterally reduced data, numeral  2109  indicates the output timing of the preceding line signal  243  output by the line memory  242 , numeral  2110  indicates the output timing of longitudinal gray scale data  245  generated by performing an operation on the output of the line memory and the laterally reduced data, and numeral  2112  indicates the output timing of the reduced display data  233  output from the output data selector  246 . L 0  and L 1  denote data for the first line and data for the second line respectively; L 0  and L 1  are averaged to generate the longitudinal reduced data. This also applies to the second line, third line, and later. Numeral  2111  indicates a longitudinal position signal, which becomes a selection signal for the output data selector  246  to allow the longitudinal reduced data  245  to be output on the line next to the extraction line  210  shown in FIG.  18 . Numeral  2112  indicates the output timing for the reduced display data  233 , numeral  2113  indicates the output timing for a horizontal synchronizing signal contained in the liquid crystal display timing signal  6 , and numeral  2114  indicates the timing of display data actually displayed. Although the output timing  2112  for the output data selector  246  follows the longitudinal position signal timing  2111 , L 1  is not displayed as shown in  2114  because the actual horizontal synchronizing signal is as shown in  2113 . 
     The enlargement process according to the invention will be discussed in detail with reference to FIGS. 25,  12 , and  29 . 
     In FIG. 25, the preceding dot data latch  237  operates like that for the reduction process section  53 . When R display data  219  indicated by the lateral display position signal  82  is data at the dot position X (0, 0) shown in Expression 6, the lateral operation section  240  performs an operation only on the R display data  219 ; when the R display data  219  is data at the dot position X (0, 1), X (0, 3), or X (0, 4), the lateral operation section  240  outputs 2-dot data for the operation result on the R display data  219  and the preceding dot data  239  and the operation result on only the R display data  219  while 1-dot R display data  219  is input; when the R display data  219  is data at the dot position X (0, 2), the lateral operation section  240  performs an operation on the R display data  219  and the preceding dot data  239 . 
     In FIG. 25, the line memory  242  and the longitudinal operation section  244  operate like those of the reduction process section  231 . Longitudinal gray scale data  245  for one screen (frame) is stored in the gray scale data frame memory a  248  and laterally enlarged data  247  for one screen (frame) is stored in the display data frame memory  249 . When display data for the next screen (frame) is input, the read insertion data  250  is read and inserted into any position between the read display data  251  in response to the longitudinal display position signal for inserting a horizontal line. When a number of insertion lines are equally spaced, for example, when a gray scale line is inserted every n lines, (n+1) line memories are provided for storing inserted gray scale data and line data. When the next data is input, the (n+1)-line data containing the gray scale line data is read out while n-line data is stored, whereby a horizontal line can be inserted without Providing the frame memories. 
     FIG. 26 is an input/output timing chart for the lateral enlargement process of the enlargement process section  232 . 
     In the figure, numeral  2115  indicates the input timing of R display data  219 , numeral  2116  indicates the output timing of Preceding dot data  239 , and numeral  2117  indicates the output timing of a synchronous clock contained in the liquid crystal display timing signal  6 , and numeral  2118  indicates the output timing of laterally enlarged data  247 . Each digit following X represents the lateral display Position (dot Position) 0 to 4. X 0 ′ to X 7 ′ of the laterally enlarged data  247  are the operation results according to Expression 7; while 5-dot data is input, 8-dot data is output according to the synchronous clock timing  2117 . 
     FIG. 29 is an input/output timing chart for the longitudinal enlargement process of the enlargement process section  232 . 
     In the figure, numeral  2119  indicates the output timing of laterally enlarged data  247  for each line, numeral  2120  indicates the output timing of the preceding line data  243  for each line, output from the line memory  242 , and numeral  2121  indicates the output timing of longitudinal gray scale data  245  for each line, showing that the longitudinal gray scale data  245  is the result of dividing by two the sum of the laterally enlarged data  247  and the preceding line data  243  which is the data one line before the laterally enlarged data  247 . Numeral  2122  indicates the input timing of the longitudinal display position signal  83 , numeral  2123  indicates a horizontal synchronizing signal contained in the liquid crystal display timing signal  6 , and numeral  2124  indicates the timing for each line displayed on the liquid crystal panel  7 . The longitudinal display position signal input timing  2122  is set to “1” on the line next to the extraction line  214  shown in FIG.  20 . At this time, the period of the synchronous clock is doubled and while 1-line data is input, 2-line data is output. For the first one of these two lines, the longitudinal gray scale data is selectively output from the gray scale data frame memory  248  and for the second line, the laterally enlarged data is selectively output from the display data frame memory  249  by the output selector  246 . 
     Next, a system which simplifies the operation section will be discussed as another example of the data conversion section  4  according to another embodiment of the invention. 
     To simplify the operation expressions given in the first example of the data conversion section  4 , the dividers may be omitted by assigning 8 or 16 to each divisor. Therefore, the operation section can be simplified by reducing 16 pixels to 15 pixels according to Expression 9 or eight pixels to seven pixels according to Expression 10: 
     
       
           X (0,0)′=( X (0,0)×15+ X (0,1)×1)/16  
       
     
     
       
           X (0,1)′=( X (0,1)×14+ X (0,2)×2)/16  
       
     
     
       
           X (0,2)′=( X (0,2)×13+ X (0,3)×3)/16  
       
     
     
       
           X (0,3)′=( X (0,3)×12+ X (0,4)×4)/16  
       
     
     
       
           X (0,4)′=( X (0,4)×11+ X (0,5)×5)/16  
       
     
     
       
           X (0,5)′=( X (0,5)×10+ X (0,6)×6)/16  
       
     
     
       
           X (0,6)′=( X (0,6)×9+ X (0,7)×7)/16  
       
     
     
       
           X (0,7)′=( X (0,7)×8+ X (0,8)×8)/16  
       
     
     
       
           X (0,8)′=( X (0,8)×7+ X (0,9)×9)/16  
       
     
     
       
           X (0,9)′=( X (0,9)×6+ X (0,10)×10)/16  
       
     
     
       
           X (0,10)′=( X (0,10)×5+ X (0,11)×11)/16  
       
     
     
       
           X (0,11)′=( X (0,11)×4+ X (0,12)×12)/16  
       
     
     
       
           X (0,12)′=( X (0,12)×3+ X (0,13)×13)/16  
       
     
     
       
           X (0,13)′=( X (0,13)×2+ X (0,14)×14)/16  
       
     
     
       
           X (0,14)′=( X (0,14)×1+ X (0,15)×15)/16  Expression 9  
       
     
       X (0,0)′=( X (0,0)×7+ X (0,1)×1)/8 
     
       
           X (0,1)′=( X (0,1)×6+ X (0,2)×2)/8  
       
     
     
       
           X (0,2)′=( X (0,2)×5+ X (0,3)×3)/8  
       
     
     
       
           X (0,3)′=( X (0,3)×4+ X (0,5)×5)/8  
       
     
     
       
           X (0,4)′=( X (0,4)×3+ X (0,1)×1)/8  
       
     
     
       
           X (0,5)′=( X (0,5)×2+ X (0,6)×6)/8  
       
     
     
       
           X (0,6)′=( X (0,6)×1+ X (0,7)×7)/8  Expression 10  
       
     
     These expressions can be used to reduce 1120 lateral pixels to 1024 pixels by reducing from 16 pixels to 15 pixels for 704 pixels of the 1120 pixels and from eight pixels to seven pixels for 416 pixels. Thus, reduction process compatible with every resolution can be carried out by combining reduction methods by which dividers can be omitted. 
     As still another example of the data conversion section  4 , a system which executes reduction process in dot units will be discussed with reference to FIG.  30 . Here, assume that a dot refers to a display element of each of R, G, and B making up one pixel of a color liquid crystal panel and that one pixel consists of three dots. The pixels of R, G, and B are arranged in order on a horizontal line on the liquid crystal panel. 
     FIG. 30 shows a concept of reduction process executed in dot units. Here, assume that 12 pixels are to be reduced to 11 pixels, namely, 36 dots to 33 dots. 
     In FIG. 30, numerals  254 ,  255 , and  256  indicate first, second, and third extraction pixels respectively. Gray scale (average) of the display data in the B dot of the first extraction pixel  254  and the display data in the B dot of its preceding pixel is calculated and the result is displayed in the B dot of the pixel preceding the first extraction pixel  254 . Gray scale (average) of the display data in the G dot of the second extraction pixel  255  and the display data in the G dot of its preceding pixel is calculated and the result is displayed in the G dot of the pixel preceding the second extraction pixel  255 . Gray scale (average) of the display data in the R dot of the third extraction pixel  256  and the display data in the R dot of its preceding pixel is calculated and the result is displayed in the R dot of the pixel preceding the third extraction pixel  256 . Since the system performs reduction process in units of dots smaller than pixels, characters and graphics are less deformed. Alternatively, six pixels can also be reduced to five pixels, namely, 18 dots to 15 dots. 
     The data conversion section  4  which performs the processing may be software using the CPU  101 , may be made of hardware, may exist in the PC  1 , or may be contained in the liquid crystal panel  7 . 
     An example of a system to which the invention is applied will be discussed with reference to FIGS. 31 and 32. 
     FIG. 31 is a conceptual illustration of the system to which the invention is applied. 
     In FIG. 31, numeral  257  indicates a workstation or personal computer which contains a central processing unit and a numeral  258  indicates a liquid crystal display unit. The workstation or personal computer  257  outputs display data having different resolutions and the liquid crystal display unit  258  has means for converting the input display data in accordance with the resolution of its own liquid crystal panel. Here, assume that the workstation or personal computer  257  outputs display data having three resolutions of 1120×780 dots, 1024×768 dots, and 640×480 dots and that the liquid crystal display unit  257  has a liquid crystal panel of a resolution of 1024×768 dots. 
     FIG. 32 shows the configuration of the liquid crystal display unit  258 , wherein numeral  259  indicates PC display data, numeral  260  indicates a PC vertical synchronizing signal, numeral  261  indicates a PC horizontal synchronizing signal, and numeral  262  indicates an input circuit. The input circuit  262  converts an input signal into a TTL level. For example, if the input signal is at ECL level, the input circuit  262  converts the ECL level into TTL level; if the input signal is an analog signal, the input circuit  262  converts the analog signal into digital form; if the input signal is at TTL level, the input circuit  262  serves as a buffer. Numeral  263  indicates a clock generator which generates a liquid crystal display clock, one of liquid crystal timing signals synchronized with the PC display data  259  from the PC horizontal synchronizing signal  261 . Numeral  4  indicates a data conversion section which operates as the data conversion section  4  described above, and here determines the resolution of the PC display data  259  from the liquid crystal timing signal  3  and executes reduction process when the resolution is 1120×780 dots, outputs the PC display data as it is when the resolution is 1024×768 dots, or executes enlargement process when 640×480 dots. 
     We have discussed the enlargement/reduction techniques as execution of the enlargement or reduction process so that the display data output from the PC  1  is made the same as the liquid crystal panel in resolution directly, but a technique of step-by-step execution of enlargement or reduction process may be used as described above. 
     Thus, display data can be displayed on a panel having a different resolution by enlarging or reducing the display data using algorithms of generating 32-pixel data from 35-pixel data, 15-pixel data from 16-pixel data, 7-pixel data from 8-pixel data, 8-pixel data from 5-pixel data, etc. 
     As described above, operations are performed on gradation information on a plurality of pixels or dots and display data is enlarged or reduced according to the result, whereby even display data output by the personal computer system assuming an output device having resolution different from that of the liquid crystal display can be displayed without erasing thin lines or deforming characters and without impairing display information of the resolution before enlargement or reduction. That is, a liquid crystal display system which enables multi-scanning display can be provided. 
     Considering the current state in which a large number of software products are already distributed, the system can eliminate the need for correcting a large number of software products so as to output signals matched with the resolution of a liquid crystal display from a computer to enable multi-scanning; an inexpensive system can be provided.

Technology Category: 3