JP4069940B2 - Image display device, image display method, and image display program - Google Patents

Description

  The present invention relates to a resolution conversion method for image data.

  In recent years, display devices mounted on mobile terminal devices such as mobile phones and PDAs (Personal Digital Assistants) have become larger in screen size and higher resolution, and higher resolution image data with a larger number of pixels than in the past has become larger. It can be displayed on the screen.

  However, high-resolution image data corresponding to such a large screen display or high-resolution display (hereinafter simply referred to as “high-resolution display”) has a large amount of data. For this reason, if high-resolution image data is constantly transmitted and received, there is a disadvantage that the communication cost becomes higher than necessary. In addition to the image data corresponding to the existing screen size, the service provider side that provides various contents to the mobile terminal device also prepares high resolution image data for users who have high resolution display devices. Need to provide high resolution image data. For this reason, the service provider also has to prepare and store a number of image data, which has the disadvantage of increasing development costs and equipment costs.

  From such a point, a method of using image data corresponding to the screen size of an existing portable terminal device and high-resolution image data properly has been considered. That is, in the case of a content providing service that is sufficient for use of image data having a normal screen size, image data corresponding to an existing screen size (hereinafter referred to as “low resolution screen data” for convenience) is transmitted and received. In the case of a content providing service that is required to display a high resolution image, high resolution image data is transmitted and received.

  When the high-resolution mobile terminal device receives high-resolution image data, it displays it as it is. On the other hand, when low-resolution image data is received, resolution conversion processing is performed inside the mobile terminal device to create and display high-resolution image data without a sense of discomfort.

  As the display device of the mobile terminal device as described above, a liquid crystal display device is widely used because of its small size and light weight. However, the liquid crystal display device inherently has a viewing angle problem, and color characteristics change or contrast decreases depending on the viewing direction with respect to the liquid crystal panel. In addition, in the case of a TN (Twisted-Nematic) mode liquid crystal, the viewing angle in the vertical direction is particularly narrow.

  The present invention provides a resolution conversion method for image data, which can create high-resolution image data without a sense of incongruity by improving the viewing angle when displaying resolution-converted low-resolution image data. Is an issue.

  In one aspect of the present invention, a display unit, resolution conversion means for generating image data of a plurality of pixels from original image data, and generating resolution-converted image data including the generated image data of the plurality of pixels, Viewing angle adjusting means for setting the gradation value of each pixel in the resolution-converted image data so that the gradation value of pixels adjacent in the vertical or horizontal direction in the resolution-converted image data is different; and the resolution-converted image Display means for displaying data on the display section, and the viewing angle adjusting means is one pixel of the adjacent pixels when the observation direction perpendicular to the surface of the display section is 0 degree. Is set to a gradation value corresponding to a display characteristic corresponding to an observation direction of −30 degrees with respect to the surface of the display unit, and the other corresponds to an observation direction of +30 degrees with respect to the surface of the display unit. Set the gradation value according to the display characteristics. .

  The image display device can be mounted on, for example, a mobile phone or a PDA, and processes and displays image data transmitted from the outside. Specifically, resolution-converted image data with increased resolution is generated by creating a plurality of pixels from each pixel constituting the acquired original image data and increasing the number of pixels. This is performed by, for example, doubling each pixel in the original image data vertically to 4 pixels. The viewing angle is adjusted for the resolution-converted image data thus obtained. Specifically, for each pixel adjacent in the vertical direction in the resolution-converted image data, each gradation value is set so that the two gradation values are different. Thereby, in the resolution-converted image data, bright pixels and dark pixels are arranged adjacent to each other in the vertical direction, and the viewing angle in the vertical direction is expanded. Then, the resolution-converted image data is displayed on the display unit. As described above, when the resolution conversion process is performed on the original image data, the converted image data can have a wide viewing angle.

  In one aspect of the above image display device, the viewing angle adjusting means may make the gradation values of pixels adjacent in the up-down direction or the left-right direction different by a predetermined gradation value or more. As described above, by providing a difference equal to or greater than a predetermined gradation value, the viewing angle can be reliably improved.

  In another aspect of the image display device, the viewing angle adjusting unit can set the gradation value of each pixel based on the display characteristics of the display unit. According to this, since the gradation value of each pixel is set based on the characteristics of the display unit that actually displays the image data, the image data that has been subjected to resolution conversion and the viewing angle has been improved with the correct brightness and color. It is possible to display.

  In another aspect of the image display device, the viewing angle adjustment unit determines a gradation value of each pixel with reference to a lookup table storing display characteristics of the display unit and the lookup table. Means. Thereby, the gradation value of each pixel can be determined according to the display characteristic by a simple process of acquiring the pixel value from a lookup table in which the display unit characteristic is stored in advance.

In another aspect of the image display device, the display unit and resolution conversion that generates image data of a plurality of pixels from the original image data and generates resolution-converted image data including the generated image data of the plurality of pixels Viewing angle adjusting means for setting the gradation value of each pixel in the resolution-converted image data so that the gradation value of pixels adjacent in the vertical or horizontal direction in the resolution-converted image data is different. Display means for displaying the resolution-converted image data on the display section, wherein the pixel is composed of a plurality of sub-pixels, and the viewing angle adjusting means is a resolution conversion of one color among the plurality of colors. Viewing angle adjustment is performed for each of the plurality of colors by making the assignment of gradation values of the subsequent sub-pixels different from the assignment of other colors. According to this, since the gradation value is different in the vertical direction in units of sub-pixels, the viewing angle is improved and the difference in gradation value between the sub-pixels adjacent in the vertical direction is made inconspicuous in human vision. it can.

  In another aspect of the above image display device, the viewing angle adjusting means refers to a lookup table that stores display characteristics of the display unit for each color of R, G, and B, and the lookup table. And means for determining a gradation value of the sub-pixel for each color.

  Strictly speaking, it is known that viewing angle characteristics differ for each color of R, G, and B. Therefore, by determining gradation values of sub-pixels of each color according to display characteristics for each color of R, G, and B It becomes possible to improve the viewing angle more appropriately.

  Another aspect of the above image display device further includes an input unit that receives a selection instruction for a wide viewing angle mode and a narrow viewing angle mode, and the display unit is configured so that the wide viewing angle mode is selected. The resolution-converted image data that has been adjusted by the viewing-angle adjusting means is displayed, and the resolution-converted image data that has not been adjusted by the viewing-angle adjusting means when the narrow viewing angle mode is selected Is preferably displayed.

  According to this aspect, the user of the image display apparatus can select either the wide viewing angle mode or the narrow viewing angle mode according to his / her preference. When the wide viewing angle mode is selected, the viewing angle is improved by giving a gradation difference in the vertical direction to the pixels constituting the resolution-converted image data. On the other hand, when the narrow viewing angle mode is selected, image data is displayed without enlarging the viewing angle, without giving such a gradation difference.

  In another aspect of the present invention, there is provided an image display method executed in an image display device including a display unit, wherein image data of a plurality of pixels is created from original image data, and the created image data of the plurality of pixels is stored. A resolution conversion step of generating resolution-converted image data, and a gradation of each pixel in the resolution-converted image data so that a gradation value of a pixel adjacent in the vertical or horizontal direction in the resolution-converted image data is different. A viewing angle adjustment step of setting a value, and a display step of displaying the resolution-converted image data on the display unit, wherein the pixel is configured by a plurality of subpixels, and in the viewing angle adjustment step The viewing angle adjustment is performed for each of the plurality of colors by making the assignment of gradation values of subpixels after resolution conversion of one color out of the plurality of colors different from the assignment of other colors.

  According to this image display method, similarly to the above-described image display device, when the resolution conversion process is performed on the original image data, the converted image data can have a wide viewing angle.

  In another aspect of the present invention, there is provided an image display program executed in an image display apparatus including a display unit and a computer, the computer generating image data of a plurality of pixels from original image data. Resolution conversion means for generating resolution-converted image data including image data of a plurality of pixels, and the resolution-converted image data so that gradation values of pixels adjacent in the vertical or horizontal direction in the resolution-converted image data are different. Functioning as viewing angle adjusting means for setting a gradation value of each pixel therein, display means for displaying the resolution-converted image data on the display unit, and the pixels are configured by a plurality of color sub-pixels, The viewing angle adjustment means may make the assignment of gradation values of subpixels after resolution conversion of one color out of the plurality of colors different from the assignment of other colors. Accordingly, performing the viewing angle adjustment for each of the plurality of colors.

  When this image display program is executed by a computer in the image display apparatus having a display unit, the converted image data can have a wide viewing angle when resolution conversion processing is performed on the original image data. .

  Preferred embodiments of the present invention will be described below with reference to the drawings.

[Configuration of mobile terminal device]
FIG. 1 shows a schematic configuration of a mobile terminal device to which a resolution conversion method according to an embodiment of the present invention is applied. In FIG. 1, a mobile terminal device 210 is a terminal device such as a mobile phone or a PDA. The portable terminal device 210 includes a display device 212, a transmission / reception unit 214, a CPU 216, an input unit 218, a program ROM 220, and a RAM 224.

  The display device 212 can be a light and thin display device such as an LCD (Liquid Crystal Display), and displays image data in the display area. The display device 212 is capable of high-resolution display with, for example, 240 × 320 dots such as the number of pixels in the horizontal and vertical directions.

  The transmission / reception unit 214 receives image data from the outside. The image data is received, for example, when the user operates the portable terminal device 210 to connect to a server device that provides a content providing service and inputs an instruction to download desired image data. Also, when receiving face image data or the like from another user's mobile terminal device, the transmission / reception unit 214 receives the image data. Image data received by the transmission / reception unit 214 can be stored in the RAM 224.

  The input unit 218 can be composed of various operation buttons for a mobile phone, a tablet that detects contact with a touch pen for a PDA, and the like, and is used when a user performs various instructions and selections. . An instruction, selection, or the like input to the input unit 218 is converted into an electrical signal and sent to the CPU 216.

  The program ROM 220 stores various programs for executing various functions of the mobile terminal device 210. In particular, in the present embodiment, the program ROM 220 is an image display program for displaying image data on the display device 212, and low resolution image data is a high resolution image. A resolution conversion program for converting the data into data and displaying the data on the display device 212 is stored.

  The RAM 224 is used as a working memory when converting low-resolution image data to high-resolution image data according to a resolution conversion program. Further, as described above, external image data received by the transmission / reception unit 214 can be stored as necessary.

  The CPU 216 executes various functions of the mobile terminal device 210 by executing various programs stored in the program ROM 220. In particular, in the present embodiment, the resolution conversion program stored in the program ROM 220 is read and executed to convert the low resolution image data into the high resolution image data. Similarly, the image data (including low resolution image data and high resolution image data) is displayed on the display device 212 by reading and executing the image display program stored in the program ROM 220. In addition, the CPU 216 implements various functions of the mobile terminal device 210 by executing various programs other than these, but since these are not directly related to the present invention, description thereof will be omitted.

  In the following description, for convenience of description, for example, image data corresponding to an existing screen size of about 120 × 160 pixels in the horizontal and vertical directions is referred to as low-resolution image data, and the horizontal and vertical directions are 240 ×. Image data corresponding to a screen size of about 320 pixels is called high resolution image data. Further, image data corresponding to a screen size of about 240 × 320 pixels obtained by converting low resolution data by the resolution conversion method of the present invention is referred to as resolution converted image data.

[Resolution conversion processing]
Next, the resolution conversion process according to the present embodiment and the accompanying viewing angle adjustment process will be described.

(Simple resolution conversion)
First, FIG. 2A schematically shows a simple resolution conversion process that does not involve viewing angle adjustment. The example of FIG. 2A is an example of resolution conversion in which one pixel is doubled in the vertical and horizontal directions to be four pixels. In this case, image data of four pixels is created by simply adjoining one pixel before processing. In a simple resolution conversion process, the gradation values of pixels before and after the process do not change. For example, in the example of FIG. 2A, if the gradation value of one pixel before conversion is “16”, the gradation values of four pixels after resolution conversion processing are all “16”. . Therefore, the viewing angle cannot be improved.

(Basic viewing angle adjustment)
Next, FIG. 2B schematically shows a resolution conversion processing method to which basic viewing angle adjustment is applied. As described above, the TN mode liquid crystal has a property that the viewing angle in the vertical direction is narrow. Therefore, as a technique for widening the viewing angle in the vertical direction, a direction that gives a gradation difference to pixels arranged in the vertical direction is known. In one typical example, as shown in FIG. 2B, when one pixel is enlarged in the resolution conversion process, a difference is given to the gradation values of the pixels arranged in the vertical direction. In the example of FIG. 2B, it is assumed that the gradation value of a pixel to be subjected to resolution conversion is “16”, and when one pixel is doubled in the vertical direction and the horizontal direction to obtain four pixels, The gradation value of one pixel is not kept at “16”, but a difference is provided, for example, “24” and “8”. Then, a pair of pixels having different gradation values are arranged in the vertical direction. In the example of FIG. 2B, the pixels having the gradation value “8” and the pixels having the gradation value “24” are arranged in the vertical direction.

  Thus, the viewing angle in the vertical direction can be improved by performing resolution conversion by enlarging one pixel so that the gradation values of the pixels arranged in the vertical direction are different. Basically, the greater the difference between the gradation values of pixels arranged adjacent in the vertical direction, the greater the degree of increase in viewing angle. Therefore, when the resolution conversion process is performed, the viewing angle improvement degree can be adjusted by adjusting the gradation value difference between the pixels adjacently arranged in the vertical direction. In addition, by providing at least a predetermined gradation value difference between pixels adjacent in the vertical direction, it is possible to reliably obtain the resolution improvement effect.

(View angle adjustment for each RGB)
As described above, when one pixel is enlarged to 4 pixels of 2 × 2, for example, by resolution conversion processing, the vertical viewing angle is set by arranging the pixels so that the gradation values of the pixels positioned in the vertical direction are different. Can be improved.

  However, in an actual TN mode liquid crystal, it has been found by measurement that viewing angle dependency differs for each color of R (red), G (green), and B (blue). Since one pixel is composed of R, G, and B color sub-pixels, the gradation values of the sub-pixels arranged in the vertical direction by resolution conversion processing are individually set for each of R, G, and B colors. By doing so, an appropriate viewing angle adjustment can be performed for each color.

  FIG. 3 shows an example of resolution conversion processing for adjusting the gradation value for each RGB sub-pixel. Assume that the gradation value of one pixel before resolution conversion is “127” for both RGB. In the four pixels after resolution conversion shown in FIG. 3, the leftmost R subpixel has a gradation value “66” on the upper side and a gradation value “188” on the lower side, whereas the G subpixel on the right side thereof Is the gradation value “68” on the upper side and the gradation value “186” on the lower side. Further, the B subpixel on the right side has a gradation value “70” on the upper side and a gradation value “184” on the lower side. In this way, by assigning different gradation values to the subpixels after resolution conversion for each RGB color, appropriate viewing angle adjustment can be performed for each color. As a result, it is possible to remove unwanted color moire that appears depending on the viewing angle.

(Viewing angle adjustment considering display characteristics)
Next, a method for adjusting the viewing angle in consideration of display characteristics of the display device, specifically, gamma (γ) characteristics and tone characteristics will be described. In the above-described viewing angle adjustment method, the viewing angle is widened by giving a gradation value difference, that is, a light / dark difference, to the gradation values of pixels arranged in the vertical direction. However, the actual gradation value difference to be given is determined experimentally or statistically.

  On the other hand, if the actual display characteristics of the display device, specifically the gamma and tone characteristics, are determined in consideration of the actual gradation value difference, it is suitable for the display device used. The viewing angle can be adjusted. This method will be described below.

  FIG. 4A shows an example of transmittance characteristics (tone characteristics) of a certain TN mode liquid crystal panel. The tone characteristic is a characteristic indicating what level (gradation value) output is actually obtained when an input of a certain level (gradation value) is given to the target liquid crystal panel. Yes, as shown in FIG. 4A, the horizontal axis represents the input gradation value, and the vertical axis represents the output gradation value.

  In FIG. 4A, a characteristic C1 is a tone characteristic when a human observes from a direction perpendicular to the liquid crystal panel surface (0 degree direction), and a characteristic C2 is a -30 degree direction with respect to the liquid crystal panel surface. Therefore, the characteristic C3 is a tone characteristic when a human observes from the direction of +30 degrees with respect to the liquid crystal panel surface.

  The relationship between the liquid crystal panel surface and the observation direction corresponding to the characteristics C1 to C3 is schematically shown in FIG. In FIG. 4D, the characteristics observed at -30 degrees and +30 degrees perpendicular to the liquid crystal panel surface P are characteristics C1 to C3, respectively.

  As shown in FIG. 4A, the characteristic C1 corresponding to the observation direction of 0 degrees has a substantially proportional relationship between the input gradation degree and the output gradation degree, whereas the characteristic C2 corresponding to the observation direction of -30 degrees. Is curved to the bright side of the output pixel value, and conversely, the characteristic C3 corresponding to the observation direction of +30 degrees is curved to the dark side of the output pixel value. In other words, when viewing the liquid crystal panel surface P from the 0 degree observation direction, it is possible to observe pixels having brightness substantially proportional to the input pixel value, but when a person observes from the -30 degree observation direction, the same pixels are observed. Looks pretty bright. Further, when a human observes from an observation direction of +30 degrees, the same pixel looks quite dark.

  When a person actually observes a liquid crystal panel, the observation direction often changes by ± 30 degrees, so even if there is a change in the observation direction that much, a certain pixel can be seen as brightly as possible. Or at least do not look extremely bright or dark.

  Therefore, in this example, as shown in FIGS. 5A and 5B, when one pixel is enlarged to four pixels by resolution conversion, one of two pixels adjacent in the vertical direction corresponds to the characteristic C2. And the other is the gradation value corresponding to the characteristic C3. By doing so, a person observing the liquid crystal panel observes the pixel with an average gradation value (that is, average brightness) of the gradation value by the characteristic C2 and the gradation value by the characteristic C3. .

  For example, in the tone characteristic of FIG. 4A, when the resolution conversion is performed on one pixel whose gradation value is “a” and four pixels are configured, as shown in FIG. 5C, it corresponds to the characteristic C2. The gradation value of the pixel is “La2”, and the gradation value of the pixel corresponding to the characteristic C3 is “La3”. Therefore, when the human sees these four pixels together, he / she recognizes the pixel by the gradation value “La” which is the average value of the two (corresponding to the point Pa in FIG. 4A). A pixel is recognized with a gradation value that is intermediate between the characteristics C2 and C3.

  In the above example, the input gradation value “a” is an intermediate luminance level. For example, FIG. 4B shows a case where the input gradation value is a dark luminance level “b”. In this case, as shown in FIG. 5D, the gradation value of the pixel corresponding to the characteristic C2 is “Lb2”, and the gradation value of the pixel corresponding to the characteristic C3 is “Lb3”. Therefore, when the human views these four pixels together, the pixel is recognized by the gradation value “Lb” that is the average value of the two (corresponding to the point Pb in FIG. 4B). A pixel is recognized with a gradation value that is intermediate between the characteristics C2 and C3. In the case of this example, the output gradation value Lb3 due to the characteristic C3 is considerably dark, but the output gradation value Lb2 due to the characteristic C2 is bright, so that the pixel is displayed in a state that is too dark as in the case of only the characteristic C3. Disappear.

  Conversely, for example, FIG. 4C shows a case where the input gradation value is a bright luminance level “c”. In this case, as shown in FIG. 5E, the gradation value of the pixel corresponding to the characteristic C2 is “Lc2”, and the gradation value of the pixel corresponding to the characteristic C3 is “Lc3”. Therefore, when the human views these four pixels together, the pixel is recognized by the gradation value “Lc” that is the average value of the two (corresponding to the point Pc in FIG. 4C). A pixel is recognized with a gradation value that is intermediate between the characteristics C2 and C3. In this example, the output gradation value Lc2 due to the characteristic C2 is considerably bright by itself, but the output gradation value Lc3 due to the characteristic C3 is darker than that, so that the pixel is too bright as in the case of only the characteristic C2. The problem of being displayed disappears.

  As described above, when one pixel is enlarged to four pixels by resolution conversion, one of the pixels adjacent to the upper and lower sides is set to the gradation value corresponding to the tone characteristic C2 corresponding to the observation direction of −30 degrees, and the other is +30 degrees. By setting the tone value corresponding to the tone characteristic C3 corresponding to the viewing direction, a person who observes the four enlarged pixels recognizes the pixel with the average luminance level (brightness) of the characteristics C2 and C3. Therefore, there is no problem that the pixel looks dark or too bright. Actually, the direction of the liquid crystal panel and the direction of the human line of sight change slightly during observation, but even if they change slightly during observation (strictly within a range of ± 30 degrees), Since the brightness of the observed pixel is maintained between the characteristics C2 and C3, there is no problem that the pixel appears dark or too bright. Therefore, this method is a method that enables appropriate viewing angle adjustment for the liquid crystal panel based on the physical characteristics of the liquid crystal panel to be processed.

  As an actual gradation value determination process, first, characteristics C2 and C3 shown in FIG. 4A are stored in advance in a lookup table (LUT) or the like. When one pixel to be enlarged is determined by resolution conversion, the LUT is referred to, an output gradation value corresponding to the gradation value is obtained in the characteristics C2 and C3, and the gradation of the four pixels after enlargement is obtained. What is necessary is just to assign to a value (refer FIG. 5).

  In the above description, the tone characteristics shown in FIG. 4A are common to the three RGB colors. Actually, as described above, since it is known that the viewing angle characteristics are different for each color of RGB, the tone characteristics described above are also prepared for each RGB and stored in the LUT. It is more preferable to set the gradation value. In this case, the tone value is determined with reference to the tone characteristics in the LUT corresponding to each of the RGB sub-pixels constituting one pixel.

  In the above example, the characteristics corresponding to the observation method of ± 30 degrees with respect to the liquid crystal panel surface P are used. However, the present invention is not limited to this angle, and the structure and use of the mobile terminal device to which the present invention is applied. Accordingly, it is desirable to determine the gradation value in consideration of characteristics at a specific angle that is highly likely to be observed by the user.

(Viewing angle improvement pattern)
Next, a pattern for improving the viewing angle will be described. As already described, basically, if a pixel obtained by resolution conversion has gradation values that are sufficiently separated in the vertical direction, an effect of improving the viewing angle can be obtained. For example, as described above, when one pixel is enlarged to four pixels by resolution conversion, several patterns as shown in FIG. 6 are conceivable.

  The pattern 40 in FIG. 6 is a pattern in which there is no or little difference in gradation values of pixels adjacent in the vertical direction, and the effect of improving the viewing angle cannot be obtained.

  The patterns 41 and 42 are obtained by giving a difference to the gradation values of pixels adjacent in the vertical direction in units of pixels. Specifically, in the pattern 41, the gradation values of the upper left pixel 41a and the lower right pixel 41d are low, and the gradation values of the lower left pixel 41b and the upper right pixel 41c are high. In the pattern 42, the gradation values of the upper two pixels 42a and 42c are low, and the gradation values of the lower two pixels 42b and 42d are high. On the contrary, a pattern in which the upper two pixels 42a and 42c have high gradation values and the lower two pixels 42b and 42d have low gradation values is also conceivable. In this way, the method of giving the gradation difference in the vertical direction in units of pixels can provide an effect of improving the resolution. Basically, the greater the gradation difference between the vertical pixels, the greater the resolution improvement effect.

  The patterns 43 and 44 are provided with a gradation difference in the vertical direction not in pixel units but in sub-pixel units. A sub-pixel is a unit that constitutes one pixel, and is usually constituted by a display region of any one of R, G, and B colors. R, G, and B sub-pixels are assembled to form one pixel.

In the pattern 43 shown in FIG. 6, the gradation values of the R and B subpixels of the upper left pixel 43a are low, and the gradation value of the G subpixel is high. On the other hand, the gradation value of the R and B subpixels of the lower left pixel 43b is high, and the gradation value of the G subpixel is low. Thus, the viewing angle in the vertical direction is also improved by giving a gradation difference in the vertical direction in units of subpixels. In the pattern 44, the gradation values of the R and B subpixels of the upper two pixels 44a and 44c are low, and the gradation value of the G subpixel is high. Meanwhile, the gradation value of the sub-pixels of R and B of the lower two pixels 44b and 44d is rather high, the gradation value of the sub-pixels of G is not low. This may also be a pattern in which the vertical direction is reversed.

  As described above, the method of giving the gradation difference in the vertical direction in units of sub-pixels makes the pattern provided with the gradation difference less conspicuous to the human eye than the method of giving the gradation difference in the vertical direction in units of pixels. There is an advantage that you can. That is, if the resolution of a pattern can be set at a spatial frequency that exceeds the resolution of the human eye, the gradation difference in the pattern, that is, the brightness of the subpixels, is difficult to recognize by the human eye. Therefore, if a pattern having a gradation difference in the vertical direction in units of sub-pixels is used, it becomes possible to make the change in brightness and darkness in the pattern inconspicuous and improve the viewing angle.

  Note that when performing double enlargement in the vertical and horizontal directions by resolution conversion, if pixels with the same gradation value are arranged in the horizontal direction as in the pattern 42 or 44, they are adjacent depending on the driving method of the liquid crystal display panel. The two pixels can share the same data and drive the pixels to perform display. In this case, the use of the pattern 42 or 44 can reduce power consumption.

[Display control processing]
Next, a display control process using the resolution conversion process will be described. Note that the display control process described below is performed by the CPU 216 of the mobile terminal device 210 illustrated in FIG. 1 executing a display control program and a resolution conversion program prepared in advance in the program ROM 220.

  FIG. 7 shows a flowchart of display control processing performed by the mobile terminal device 210. First, the mobile terminal device 210 receives image data to be displayed from an external server or the like (step S1). In this case, it is assumed that the received image data is low-resolution image data having a lower number of pixels than the resolution of the display device 212 in the mobile terminal device 210.

  The CPU 1 performs resolution conversion on the received low resolution image data (step S2). Specifically, for example, one of the methods illustrated in FIG. 2 to FIG. 6 is used to perform a process of enlarging one pixel to four pixels, and at the same time, giving a gradation difference in units of pixels or sub-pixels in the vertical direction. Image data (referred to as “resolution-converted image data”) as a result of improving the viewing angle is created (step S2). Then, the CPU 1 supplies the resolution-converted image data thus created to the display device 212 for display (step S3). In this way, the mobile terminal device 210 can receive low-resolution image data, convert it to high-resolution image data, and display it without a sense of incongruity. At that time, since the viewing angle is improved by any of the methods described above, the image data displayed after resolution conversion can be widened.

  Next, display control processing when the same portable terminal device 210 enables mode selection between the wide viewing angle mode and the narrow viewing angle mode will be described. In a portable terminal device using a liquid crystal panel, it is usually preferable that the viewing angle is wide because it is easy for the user to see. However, in the case of a mobile phone, for example, the display content is often viewed in an environment where there are many people around the train, so that the display content is not seen by people who are next or opposite. There is also a demand to narrow the viewing angle. Therefore, in the following display control processing, the user can select the wide viewing angle mode and the narrow viewing angle mode.

  FIG. 8 is a flowchart of display control processing that adopts such viewing angle mode selection. First, the CPU 1 receives image data to be displayed from an external server or the like (step S11). Then, it is determined whether the received image data is high resolution image data or low resolution image data (step S12). Note that the high-resolution image data is image data having the number of pixels suitable for the number of display pixels included in the display device 212 in the mobile terminal device 210.

  When the high-resolution image data is received (step S12; Yes), the image data may be displayed as it is, and it is not necessary to perform resolution conversion. Therefore, the process proceeds to step S16 described later. On the other hand, when low-resolution image data is received (step S12; No), the CPU 1 determines whether or not the user has selected the wide viewing angle mode at that time (step S13). Note that the user can select the wide viewing angle mode and the low viewing angle mode by operating the input unit 218 of the mobile terminal device 210.

  When the wide viewing angle mode is selected (step S13; Yes), the CPU 1 performs resolution conversion and gives a gradation difference to the pixels in the vertical direction as in the case of the display control process of FIG. A resolution improvement process is performed (step S14).

  On the other hand, when the narrow viewing angle mode is selected (step S13; No), the CPU 1 performs resolution conversion without a viewing angle improvement process (step SS15). Note that the resolution conversion processing when the viewing angle improvement processing is not performed is, for example, as shown in FIG. 2A, the enlarged pixel does not have a gradation difference in the vertical direction or has a small gradation difference. The pixel is enlarged so that it does not occur.

  Finally, the CPU 1 supplies the obtained high resolution image data to the display device 212 for display. With the above processing, when the user selects the wide viewing angle mode, the image data after resolution conversion becomes a wide viewing angle, and when the user selects the low viewing angle mode, the resolution The returned image data has a low viewing angle as a result of the viewing angle not being improved.

[Modification]
The above description is an example of improving the vertical viewing angle in consideration of the property that the vertical viewing angle of the TN mode liquid crystal is basically narrow. However, it is possible to improve the viewing angle in the left-right direction by the same method. In that case, a sufficient gradation difference may be similarly given to the gradation values of pixels adjacent in the left-right direction among pixels obtained after resolution conversion.

  In the above-described embodiment, the electro-optic element using liquid crystal (LC) as the electro-optic material has been described as an example. As the liquid crystal, for example, in addition to a TN (Twisted Nematic) type, a STN (Super Twisted Nematic) type having a twist orientation of 180 or more, a BTN (Bi-stable Twisted Nematic) type, a dual type having a memory property such as a ferroelectric type. Well-known materials can be widely used, including a stable type, a polymer dispersion type, a guest host type, and the like. The present invention is also applicable to an active matrix panel using a two-terminal switching element such as a TFD (Thin Film Diode) in addition to a TFT (Thin Film Transistor) which is a three-terminal switching element. In addition, the present invention can also be applied to a passive matrix panel that does not use a switching element. Furthermore, it can be applied to electro-optic materials other than liquid crystal, for example, electroluminescence (EL), digital micromirror device (DMD), or various electro-optic elements using plasma emission or fluorescence by electron emission. is there.

The schematic structure of the portable terminal device to which the resolution conversion process of this invention is applied is shown. A simple resolution conversion process and a resolution conversion method with viewing angle adjustment are schematically shown. A resolution conversion method with viewing angle adjustment for each RGB is schematically shown. It is a figure for demonstrating the concept of the viewing angle adjustment method which considered the display characteristic of the display apparatus. A viewing angle adjustment method in consideration of display characteristics of a display device is schematically shown. The example of a pattern which can improve a viewing angle is shown. It is a flowchart of the display control process by a portable terminal device. It is a flowchart of the display control process which can select the mode of a viewing angle.

Explanation of symbols

210 portable terminal device, 212 display device, 214 processing font memory, 216 CPU, 218 input unit, 220 program ROM, 224 RAM

Claims (5)

A display unit;
Resolution conversion means for generating resolution conversion image data including image data of a plurality of pixels by multiplying a pixel including a plurality of color sub-pixels by an integer multiple in the vertical direction and the horizontal direction, respectively ;
The gradation value of each sub-pixel in the resolution-converted image data is set so that the gradation value of at least one color sub-pixel included in pixels adjacent in the vertical or horizontal direction in the resolution-converted image data is different. Viewing angle adjusting means;
Display means for displaying the resolution-converted image data on the display unit,
The viewing angle adjusting means, the allocation of the gradation values of the sub-pixels after the resolution conversion in one color of the plurality of colors, before the resolution conversion of the one of the same gradation value and the gradation value of the color An image display apparatus, wherein viewing angle adjustment is performed for each of the plurality of colors by differently assigning gradation values of sub-pixels after resolution conversion in other colors. 2. The image display according to claim 1, wherein the viewing angle adjusting unit changes a gradation value of a sub-pixel included in a pixel adjacent in the vertical direction or the horizontal direction by a predetermined gradation value or more. apparatus. The pixels are composed of R, G, and B subpixels.
The viewing angle adjusting means includes a lookup table storing display characteristics of the display unit for each of the colors R, G, and B.
The image display apparatus according to claim 1, further comprising: a unit that determines a gradation value of the sub-pixel for each color with reference to the lookup table. An image display method executed in an image display device including a display unit,
A resolution conversion step of generating resolution-converted image data including image data of a plurality of pixels by multiplying a pixel including a plurality of color sub-pixels by an integer multiple in each of the vertical direction and the horizontal direction ;
The gradation value of each sub-pixel in the resolution-converted image data is set so that the gradation value of at least one color sub-pixel included in pixels adjacent in the vertical or horizontal direction in the resolution-converted image data is different. Viewing angle adjustment process;
Displaying the resolution-converted image data on the display unit,
The viewing angle adjustment step, the allocation of the gradation values of the sub-pixels after the resolution conversion in one color of the plurality of colors, before the resolution conversion of the one of the same gradation value and the gradation value of the color An image display method characterized in that viewing angle adjustment is performed for each of the plurality of colors by differentiating it from assignment of gradation values of sub-pixels after resolution conversion in other colors. An image display program to be executed in an image display device including a display unit and a computer, wherein the computer is
Resolution conversion means for generating resolution-converted image data including image data of a plurality of pixels by multiplying pixels including sub-pixels of a plurality of colors by an integer multiple in the vertical direction and the horizontal direction, respectively .
The gradation value of each sub-pixel in the resolution-converted image data is set so that the gradation value of at least one color sub-pixel included in pixels adjacent in the vertical or horizontal direction in the resolution-converted image data is different. Viewing angle adjustment means,
Function as display means for displaying the resolution-converted image data on the display unit;
The viewing angle adjusting means, the allocation of the gradation values of the sub-pixels after the resolution conversion in one color of the plurality of colors, before the resolution conversion of the one of the same gradation value and the gradation value of the color An image display program for performing viewing angle adjustment for each of the plurality of colors by differentiating it from assignment of gradation values of sub-pixels after resolution conversion in other colors.

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