JP4029762B2 - Image display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an image display device using subfields such as a plasma display panel (hereinafter abbreviated as PDP).
[0002]
[Prior art]
  In general, in an image display apparatus that performs gradation display using subfields such as a PDP, noise-like image quality deterioration called a so-called moving image pseudo contour may be observed in a moving image portion. The moving image pseudo contour is caused by the lighting pattern of the subfield changing discontinuously with respect to the continuous change of the gradation value. This moving image pseudo contour is known to be improved, for example, when the number of subfields is increased. However, when the number of subfields is increased, there is a problem that the required luminance cannot be obtained because the lighting time is reduced. there were.
[0003]
  For this reason, there is an attempt to suppress the moving image pseudo contour by restricting the combination of subfields in a moving region without increasing the number of subfields (see, for example, Patent Document 1). This conventional image display device displays an image with a combination of gradations in which moving image pseudo contours are less likely to be generated by limiting the gradations used for display in a portion where the image moves, and accompanying a decrease in the number of gradations In order to compensate for image quality degradation, pseudo gradation using dither processing is added to ensure a certain gradation.
[0004]
[Patent Document 1]
    JP 2000-276100 A
[0005]
[Problems to be solved by the invention]
  However, in the conventional image display device, if the gradation is further limited in order to increase the effect of suppressing the moving image pseudo contour, the pattern used for dither processing to compensate for this becomes more conspicuous, and the number of gradations that can be substantially expressed There has been a problem of lowering.
[0006]
  The present invention has been made in order to solve such problems, and provides an image display device that achieves both suppression of moving image pseudo contour and good gradation display.
[0007]
[Means for Solving the Problems]
  In order to solve the above-described problems, the image display device of the present invention detects an area having gradation and a motion from an image signal, and detects the magnitude and direction of the movement of the area and the inclination of the gradation. Depending on the size and direction of the image, the specified gradation of the image signal is corrected to another gradation, and the intermediate non-lighting subfield that causes the moving image pseudo contour is dispersed, thereby suppressing the moving image pseudo contour. It is characterized by performing.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
  That is, the invention according to claim 1 is an image display device that displays multiple gradations by configuring one field with a plurality of subfields and controlling each subfield to be turned on or off.Inclination detecting means for detecting a region having a gradient in the gradation value from the image signal and detecting the magnitude and direction of the inclination of the inclined region, and detecting a region having movement from the image signal A gradation detecting unit that detects the magnitude and direction of movement of the region with movement, and a gradation that corrects a predetermined gradation to another gradation based on the output of the inclination detecting unit and the output of the movement detecting unit. A correction means, and the gradation correction means includes a non-lighting subfield having a luminance weight smaller than a lighting subfield having a maximum luminance weight when the inclined region moves in a lower gradation direction. If the gradation correction is performed to distribute the maximum intermediate non-lighting subfield with the largest luminance weight among the surrounding subfields, and the sloped area moves in the direction of higher gradation, the luminance weight Perform gradation correction to disperse the maximum intermediate non-lighting subfield or the maximum lighting subfield for the gray level where the maximum intermediate non-lighting subfield exists or the gray level where the lighting subfield with the largest luminance weight is switched. Configured asAn image display device characterized by the above.
[0009]
  The invention according to claim 2 is the invention according to claim 1,Of the gradation after correctionAt least one includes a gradation for lighting a subfield having the largest luminance weight among non-lighting subfields having a smaller luminance weight than a lighting subfield having the largest luminance weight for the gradation before correction. The image display device is characterized.
[0010]
  The invention according to claim 3 is the invention according to claim 2,Tone after correctionThe image display device is characterized in that the average value of is equal to the gradation before correction.
[0011]
  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0012]
  FIG.IsIn the present inventionIt is a circuit block diagram of an image display device. The inclination detecting means 21 detects an area having a gradient in gradation (hereinafter abbreviated as an inclined gradation area) from the image based on the image signal 10. The motion detecting means 31 detects a region having motion from the image based on the image signal 10. The correction area detection unit 41 detects a gradient gradation area having movement as a correction area by obtaining a logical product of the output of the inclination detection unit 21 and the output of the movement detection unit 31. The gradation correction means 61 corrects a predetermined gradation of the image signal 10 to another gradation by adding a correction value to the image signal 10.
[0013]
  In addition, the image signal selection unit 71 selects the output of the gradation correction unit 61 in an inclined gradation region with movement, and selects the image signal 10 in other regions. The subfield encoding unit 80 converts the output of the image signal selection unit 71 into a subfield signal and supplies it to the plasma display 90.
[0014]
  Figure 2In the present inventionIt is a circuit block diagram of the gradation correction means 61 of an image display apparatus. The correction value generating means 612 generates two correction values -m and + m for each gradation of the image signal. The correction value switching means 613 switches the two correction values alternately or randomly in pixel units and line units. The adding unit 614 adds the output of the correction value switching unit 613 and the image signal to convert a predetermined signal of the image signal into a correction gradation and outputs it as a corrected image signal. Since the correction values have values of -m and + m, the average value of the correction gradations obtained by adding them is equal to the gradation before the correction, and these correction values are converted into pixel units and lines by the correction value switching means 613. Since the unit is switched alternately or randomly, the average value of the corrected image signal does not change by the correction.
[0015]
  The subtracting unit 615 calculates a difference between the image signal before correction and the corrected image signal, delays the difference signal by a predetermined delay unit 616, and adds the difference signal to the input signal using the adding unit 617. When such a feedback type circuit configuration is used as the gradation correction means, the average gradation value including the surrounding pixels can be brought close to the gradation value before the correction, and the gradation of the gradation associated with the gradation correction can be reduced. The error can be corrected in a pseudo manner.
[0016]
  next,This image display deviceWill be described. In the present embodiment, one field is divided into 12 subfields (SF1, SF2,..., SF12), and each subfield is (1, 2, 4, 8, 12, 20, 24, 28). , 32, 36, 40, 48).
[0017]
  FIG. 3 is a diagram showing combinations of display gradations and subfields that are turned on to express the gradations. Here, the subfield indicated by “●” is a subfield to be lit. In order to make the figure easier to see, subfields (SF1, SF2) having luminance weights of lower 2 bits are omitted. 3A shows the range of gradation values from “0” to “127”, and FIG. 3B shows the range of gradation values from “128” to “255”.
[0018]
  Normally, gradation display is performed on the input image signal according to the combination of the subfields. However, if this combination is used as it is with respect to a moving gradient gradation region, a strong moving image pseudo contour may occur.
[0019]
  As a result of studying the moving image pseudo contour, the present inventors, among subfields constituting one field, a non-lighting subfield having a luminance weight smaller than a lighting subfield having the maximum luminance weight (hereinafter referred to as an intermediate lighting field). It has been found that the abbreviated non-lighting subfield) causes a moving image pseudo contour generated by a combination of gradation gradient and movement. In particular, the intermediate non-lighting subfield having the largest luminance weight (hereinafter abbreviated as the maximum intermediate non-lighting subfield) is the main cause of the moving image pseudo contour. Hereinafter, the reason why the moving image pseudo contour is generated in the inclined gradation region having movement will be described.
[0020]
  FIG. 4 is a diagram for explaining the reason why a moving image pseudo contour is generated in an inclined gradation region with movement. Here, as shown in FIG. 4 (a), for example, in the range of about “164” to “184”, the gradient gradation region in which the left side is dark and becomes brighter as it goes to the right moves to the left. Think about images. FIG. 4B is a diagram in which the above-described gradient gradation region is developed into subfields, where the horizontal axis corresponds to the screen position in the horizontal direction and the vertical axis corresponds to the passage of time. Here, only six subfields (SF6, SF7,..., SF11) are shown for easy understanding of the figure. The hatching in FIG. 4 indicates a non-lighting subfield. If the gradient gradation area is stationary, as shown by the arrow C, since the human line of sight is also stationary on the screen, the original gradation can be recognized. However, when the gradient gradation area moves to the left, the line of sight also moves to the left. As a result, the line of sight follows the maximum intermediate non-lighting subfield as indicated by arrow A, and You will recognize a very dark dark line inside. Note that the arrow A in FIG. 3 represents the same line of sight movement as the arrow A in FIG.
[0021]
  Thus, it can be seen that a strong moving image pseudo contour is generated when the line of sight moves at a speed following the intermediate non-lighting subfield in the inclined gradation region. In the above example, when the line of sight moves at a speed such that SF6 to SF11 elapse while the gradation value increases from “164” to “184”, the maximum intermediate non-lighting subfield is continuously recognized, It can be seen that a dark line appears as a moving image pseudo contour.
[0022]
  On the contrary, if the position of the inclined gradation area in the screen, the degree of inclination, and the amount of movement thereof are known, the area where the moving image pseudo contour is generated can be predicted in advance.
[0023]
  FIG.In the present inventionFIG. 5A is a diagram showing a correction pattern of the gradation correcting means 61, FIG. 5A is a relationship between a gradation value before correction and a lighting subfield, and FIG. 5B is a relationship between a gradation value after correction and a lighting subfield. Is shown. For simplicity of explanation, FIG. 5 shows only the gradation between “168” and “207”. The gradation correction means 61 corrects the gradation so as to light the maximum intermediate non-lighting subfield before correction, and instead, the subfields before and after that are made nonlighting subfields with a probability of 1/2. That is, the maximum intermediate non-lighting subfield of the gradation before correction as the correction gradation (the subfield having the largest luminance weight among the non-lighting subfields having a smaller luminance weight than the lighting subfield having the largest luminance weight) By selecting the gradation to light up, the maximum intermediate non-lighting subfield that causes the moving image pseudo contour is dispersed to the preceding and following subfields. For example, for a signal of gradation “168”, correction values of −m = −4 and + m = 4 are added and converted into two correction gradations of gradation “164” and gradation “172”. The output is alternately switched in units of pixels and lines. At this time, the original gradation “168” is corrected to one of the correction gradations “164” and “172”, but since the respective correction probabilities are ½, the average value is the original gradation “168” is maintained.
[0024]
  FIG. 5 (c)Image display deviceIt is a figure which shows the average lighting probability of each subfield with respect to each gradation. The numerical value in each column is the lighting probability after correction, where “1” and “1/2” represent the lighting probability 1 and 1/2, respectively, and the blank represents the lighting probability 0. For example, for the signal of gradation “168”, the maximum intermediate non-lighting subfield before correction is SF10 and the lighting probability is 0, but the intermediate non-lighting subfield after correction is distributed to SF9 and SF11. In addition, since the lighting probability thereof is also halved, the moving image pseudo contour in the correction area is also dispersed to improve the image display quality.
[0025]
  As described above, in the moving image pseudo contour, there may be many intermediate non-lighting subfields in a specific region determined by the gradient of the gradation value and its movement, or there may be a maximum intermediate non-lighting subfield with a large luminance weight. Caused by a cause. Therefore,This embodimentIn this example, a correction area is extracted based on the gradient of the gradation value and its movement, and in this area, the intermediate non-lighting subfield that causes the generation of the moving image pseudo contour, in particular, the maximum intermediate non-lighting subfield is distributed to surrounding subfields. Since the tone correction is performed, the moving image pseudo contour can be effectively suppressed.
[0026]
  Next, an example will be described in which the gradation correction means disperses the maximum intermediate non-lighting subfields over a wider range than in the above embodiment and increases the lighting probability of these subfields.
[0027]
  FIG. 6 shows the present invention.Other embodimentsFIG. 6 is a circuit block diagram of gradation correction means 62 of the image display apparatus in FIG.Example aboveThe correction value generating means 622 generates four correction values, -m2, -m1, + m1, and + m2, for each gradation, and the correction value switching means 623 converts these four correction values into pixel units. This is to switch alternately or randomly in line units.
[0028]
  In addition,This embodimentThe circuit block diagram of the image display apparatus in FIG. 1 is obtained by replacing the gradation correction means 61 of FIG. 1 with the gradation correction means 62 shown in FIG.
[0029]
  FIG.This embodimentFIG. 7A is a diagram showing a correction pattern of the gradation correction means 62 in FIG. 7A, FIG. 7A is a relationship between the gradation value before correction and the lighting subfield, and FIG. 7B is a relationship between the gradation value after correction and the lighting subfield. Is shown. FIG. 7 shows only combinations of lighting subfields for gradations between “168” and “207”.
[0030]
  For example, for a signal having a gradation value “168”, correction values of −m2 = −12, −m1 = −4, + m1 = 4, + m2 = 12 are added, and gradations “156” and “164” are added. , “172”, and “180” are converted into four correction gradations, and are output alternately or randomly in units of pixels and lines. In this case, the original gradation is maintained as the average value of the correction gradation.
[0031]
  FIG. 7 (c)This embodimentIt is a figure which shows the average lighting probability of each subfield with respect to each gradation of the image display apparatus. The numerical value in each column is the lighting probability after correction, where “1”, “3/4”, “1/2”, and “1/4” are the lighting probabilities 1, 3/4, 1/2, respectively. , 1/4, and the blank represents the lighting probability 0. For example, the intermediate non-lighting subfield before correction for the signal of gradation “168” is SF10 and its lighting probability is 0, but the intermediate non-lighting subfield after correction is distributed to SF4, SF7, SF9, and SF11. And their lighting probabilities are also 3/4, 3/4, 3/4, and 1/2, respectively, and moving image pseudo contours in a moving gradient gradation area are also distributed over a wide range to improve image display quality. To do.
[0032]
  In this way, the present embodiment has a wider range of dispersion of the intermediate non-lighting subfields that cause the moving image pseudo contour, and the lighting probability of those sub fields is increased, so that the effect of suppressing the moving image pseudo contour is increased.Embodiment aboveCan be larger than
[0033]
  Next, gradation correction is performed by limiting a predetermined gradation to be corrected to a gradation in which an intermediate non-lighting subfield having a large luminance weight exists or a gradation in which a lighting subfield having the largest luminance weight is switched. An example of performing is described.
[0034]
  FIG.This embodimentFIG. 8A is a diagram showing a correction pattern of the gradation correction means in FIG. 8, FIG. 8A shows the relationship between the gradation value before correction and the lighting subfield, and FIG. 8B shows the relationship between the gradation value after correction and the lighting subfield. Show. FIG. 8 shows only combinations of lighting subfields for gradations between “156” and “219”.
[0035]
  As shown in FIG. 8A, for example, the maximum intermediate non-lighting subfield SF10 having a large luminance weight exists in the gradation “168”, and at the same time, the lighting subfield having the maximum luminance weight is included in gradations higher than this gradation. It is switched from SF10 to SF11. The gradation “208” includes a maximum intermediate non-lighting subfield SF11 having a large luminance weight, and at the same time, the lighting subfield having the maximum luminance weight is switched from SF11 to SF12.This embodimentIn FIG. 5, gradation correction is performed only in the gradations of four columns including these gradations in the vicinity of these gradations. That is, as shown in FIG. 8B, gradation correction is performed for gradations “160” to “175” and “200” to “215”, but gradations are applied to gradations “176” to “199”. Do not make corrections.
[0036]
  FIG. 8 (c)This embodimentIt is a figure which shows the average lighting probability of each subfield with respect to each gradation of the image display apparatus. In the vicinity of the gradations “168” to “171” and “208” to “211” where the strong pseudo false contour is likely to occur because the luminance weight of the maximum intermediate non-lighting subfield is large, the maximum intermediate non-lighting subfield is dispersed, In addition, although the lighting probability increases, correction value addition is not performed for gradations “176” to “199” in which the luminance weight of the maximum intermediate non-lighting subfield is relatively small, so that excessive gradation correction is avoided. it can.
[0037]
  in this wayThis embodimentIn this image display apparatus, since gradation correction is performed only in the vicinity of the gradation having the maximum intermediate non-lighting subfield with a large luminance weight, when relatively gentle correction is desired or excessive correction is avoided. This is an effective method if you want to.
[0038]
  In addition,This embodimentThe gradation correction means of the image display apparatus in FIG. 5 may be realized by using a dedicated circuit configuration, but is the same as the configuration of the circuit block diagram shown in FIG. , −m = 0, + m = 0 may be realized.
[0039]
  Next, the embodiment shown in FIG. 8 is performed in that the gradation correction is performed only in the vicinity of the gradation in which the intermediate non-lighting subfield having a large luminance weight exists or the gradation in which the lighting subfield having the largest luminance weight is switched. The gradation correction means distributes the maximum intermediate non-lighting subfields in a wider range than the embodiment shown in FIG. 8 and increases the lighting rate of these subfields, and the effect of suppressing the moving image pseudo contour is the same as the embodiment. An example in which is increased will be described.
[0040]
  Figure 9This embodimentFIG. 9A is a diagram showing a correction pattern of the gradation correction means in FIG. 9A, FIG. 9A is a relationship between the gradation value before correction and the lighting subfield, and FIG. 9B is a relationship between the gradation value after correction and the lighting subfield. Is shown.
[0041]
  In this case, correction is performed with the gradations of three columns including gradations “168” and “208”, but here, four values of −m2, −m1, + m1, and + m2 are used as correction values. One gradation is dispersed into four correction gradations. FIG. 9C is a diagram showing an average lighting probability of each subfield for each gradation at this time. Compared with FIG. 8C, it can be seen that the intermediate non-lighting subfield and the maximum luminance weight lighting subfield are more widely dispersed. Further, gradation correction is not performed for gradations “176” to “199”.
[0042]
  In addition,This embodimentThe gradation correction means of the image display apparatus in FIG. 5 may be realized by using a dedicated circuit configuration, but is the same as the configuration of the circuit block diagram shown in FIG. , −m2 = 0, −m1 = 0, + m1 = 0, + m2 = 0.
[0043]
  FIG. 10 shows an embodiment of the present invention.2 is a circuit block diagram of the image display device in FIG.This embodimentThe inclination detection means 25 detects not only the presence / absence of inclination but also the degree and direction of inclination, and the movement detection means 35 detects not only the presence / absence of movement but also the magnitude and direction thereof. The correction area detecting means 45 detects a correction area, that is, a correction area, based on the magnitude and direction of the inclination and the magnitude and direction of the movement. The correction pattern determining means 55 determines a correction pattern based on the magnitude and direction of the inclination and the magnitude and direction of the movement. The gradation correction means 65 has a plurality of correction patterns and switches them. The image signal selection means 75 selects the corrected image signal in the correction area, and selects the image signal 10 in the other areas.This embodimentInEmbodiment aboveThe four correction patterns used in the above, that is, the correction patterns shown in FIGS. 5, 7, 8, and 9, are switched based on the magnitude and direction of the inclination and the magnitude and direction of the movement.
[0044]
  The characteristics of each of the four correction patterns used here will be described again. The correction pattern shown in FIG. 5 (hereinafter abbreviated as “pattern 1”) is a gradation correction that distributes the maximum intermediate non-lighting subfield to surrounding subfields for the grayscale having the intermediate non-lighting subfield. Do. The correction pattern shown in FIG. 7 (hereinafter abbreviated as pattern 2) corrects the same gradation as pattern 1, but has a wider range of dispersion, so the effect of suppressing moving image pseudo contour is greater than pattern 1. . The correction pattern shown in FIG. 8 (hereinafter abbreviated as “pattern 3”) is a maximum intermediate non-lighting subfield having a large luminance weight, or a maximum intermediate non-lighting subfield near the gradation at which the maximum lighting subfield is switched, or the maximum. Tone correction is performed to disperse the lighting subfields. The correction pattern shown in FIG. 9 (hereinafter abbreviated as pattern 4) corrects the same gradation as pattern 3, but has a wider range of dispersion, so the effect of suppressing moving image pseudo contour is greater than pattern 3. .
[0045]
  FIG.Embodiment of the present inventionFIG. 5 is a diagram showing the relationship between the correction pattern determined by the correction pattern determining means 55, the magnitude of the inclination, and the direction of movement. If the gradient of the gradation value is small and moving in the low gradation direction, pattern 1 is used. If the gradient of the gradation value is large and moving in the low gradation direction, pattern 2 is selected. Pattern 3 is determined when the inclination is small and moving in the high gradation direction, and pattern 4 is determined when the inclination of the gradation value is large and moving in the high gradation direction. It should be noted that when the gradient of the gradation value is very small, almost no moving image pseudo contour is generated, and when the gradient of the gradation value is very large, even if the moving image pseudo contour is generated, the image is uncomfortable. Will not be recognized as. In addition, the moving image pseudo contour is not easily recognized even when the motion is very small. Therefore, FIG. 11 does not describe these cases.
[0046]
  Next, the relationship between the moving image pseudo contour, the direction of inclination, and the direction of motion will be described, and a method for determining a correction pattern will be described.
[0047]
  As shown in FIG. 4, for example, in the case where the slope area where the gradation value is about “164” to “184” and the left side is dark and becomes brighter toward the right moves to the left, Stated that a very dark dark line appears. This is because, as indicated by an arrow A in FIG. 3, when the line of sight moves to the left along the inclined area, the maximum intermediate non-lighting subfield is followed. Therefore, when the gradient gradation region moves in the low gradation direction, correction for dispersing the maximum intermediate non-lighting subfield, that is, correction of pattern 1 or pattern 2 is necessary. If the gradient of the gradation value is large, the pattern 2 having a large effect of suppressing the moving image pseudo contour is determined.
[0048]
  On the other hand, considering the case where the inclined region shown in FIG. 4A moves to the right, the dark line is not recognized because the line of sight also moves to the right following the inclined region. However, as indicated by the arrow B in FIG. 3, a bright line with high luminance is recognized in a gradation where an intermediate non-lighting subfield having a large luminance weight exists or a gradation portion where a lighting subfield having the largest luminance weight is switched. I understand that Therefore, in this case, gradation correction is performed only in the vicinity of this gradation.DoneIt is desirable to disperse the bright lines. Therefore, when the gradient gradation region moves in the high gradation direction in this way, the vicinity of the gradation in which the maximum intermediate non-lighting subfield having a large luminance weight exists or the lighting subfield having the largest luminance weight is switched. In other words, the correction limited to, that is, the pattern 3 or the pattern 4 is sufficient. When the gradient of the gradation value is large, the pattern 4 having a large effect of suppressing the moving image pseudo contour is determined.
[0049]
  As aboveIn the present inventionFocusing on the fact that the appearance of the moving image pseudo contour differs depending on the gradient of the gradation and the direction of movement, identify the region where the moving image pseudo contour is likely to occur, and determine the size or characteristics of the moving image pseudo contour. According to the best correction.Therefore, the number of gradations that should be corrected when the sloped area moves in the direction of higher gradation, and the number of gradations that should be corrected when the sloped area moves in the direction of lower gradation. Is configured to be less than. Therefore, the moving image pseudo contour is effectively suppressed without performing excessive correction on the moving image portion, and the gradation is not limited in a region where the moving image pseudo contour does not occur. Therefore, both the moving image portion and the still image portion can be favorably displayed.
[0050]
  In addition,In the present inventionAs the image display device, the circuit configurations shown in FIGS. 1, 2, 6, and 10 have been described. However, the present invention is not limited to this as long as the circuit configuration can realize a correction pattern for dispersing the intermediate non-lighting subfield. . FIG.In the present inventionIt is an example of the other circuit block diagram of an image display apparatus.
[0051]
  The gradation correction means 100 is composed of a plurality of gradation conversion tables, and converts the gradation of the image signal 10 into a corrected gradation using any one of the gradation conversion tables. The inclination detection means 20 detects an inclination gradation area from the image signal 10 and detects the magnitude and direction of the inclination. The motion detection means 30 detects a region having motion from the image signal 10 and detects its size and direction. The conversion table determination unit 40 determines a gradation conversion table to be used by the gradation correction unit 100 based on the output of the inclination detection unit 20 and the output of the motion detection unit 30.
[0052]
  As described above, in the present invention, attention is paid to the fact that the appearance of the moving image pseudo contour differs depending on the gradient of the gradation and the direction of movement, and the region where the moving image pseudo contour is likely to be generated is specified. The optimal correction is performed according to the size or characteristics ofWhen the sloped area moves in the direction of lower gradation, the largest intermediate non-lighting sub with the largest luminance weight among the non-lighting subfields with smaller luminance weight than the lighting subfield with the largest luminance weight. If gradation correction is performed to distribute the field to surrounding subfields and the inclined area moves in the direction of higher gradation, the gradation in which the maximum intermediate non-lighting subfield with a large luminance weight exists, or It is configured to perform gradation correction that distributes the maximum intermediate non-lighting subfield or the maximum lighting subfield for the gradation in which the lighting subfield with the largest luminance weight is switched.Is. Therefore, the moving image pseudo contour is effectively suppressed without performing excessive correction on the moving image portion, and the gradation is not limited in a region where the moving image pseudo contour does not occur. Therefore, both the moving image portion and the still image portion can be favorably displayed.
[0053]
  Also,When implementing the example shown in FIG.This can be realized by switching and using a total of 13 types of gradation conversion tables including 12 types of tables associated with the four correction patterns and a table not corrected.
[0054]
  In addition,In the above description,The subfield configuration shown in FIG. 3 has been described. However, even when another subfield configuration such as the number of subfields and the luminance weight thereof is used, gradation correction is performed to distribute intermediate non-lighting subfields. Thus, the same effect of suppressing the moving image pseudo contour can be obtained.
[0055]
  In addition, the motion detection unit does not necessarily need to obtain a motion vector, and may be replaced by a simple method based on the difference between the times of the image signal and the gradient of the gradation value.
[0056]
【The invention's effect】
  According to the image display device of the present invention, a region where a moving image pseudo contour is likely to be generated is specified, and an optimal correction is performed in the region, so that the moving image pseudo contour is suppressed without lowering the substantial gradation. It is possible to provide an image display device that achieves both good gradation display.
[Brief description of the drawings]
FIG. 1 of the present inventionEmbodimentBlock diagram of image display device
FIG. 2 of the present inventionEmbodimentBlock diagram of gradation correction means of image display apparatus
FIG. 3 of the present inventionEmbodimentThe figure which showed the combination of the display gradation of the image display apparatus in and the subfield to light up in order to express the gradation
FIG. 4 is a diagram for explaining the reason why a moving image pseudo contour is generated in a moving gradient gradation region;
FIG. 5 shows the present invention.EmbodimentThe figure which shows the correction pattern of the gradation correction means in
FIG. 6 of the present inventionEmbodimentBlock diagram of gradation correction means of image display apparatus
[Fig. 7] of the present invention.EmbodimentThe figure which shows the correction pattern of the gradation correction means in
[Fig. 8] of the present inventionEmbodimentThe figure which shows the correction pattern of the gradation correction means in
FIG. 9 shows the present invention.EmbodimentThe figure which shows the correction pattern of the gradation correction means in
FIG. 10 shows the present invention.EmbodimentBlock diagram of image display device
FIG. 11 shows the present invention.EmbodimentThe figure which showed the relationship between the correction pattern which the correction pattern determination means determines, and the magnitude | size of inclination and the direction of movement in
FIG. 12 shows the present invention.EmbodimentOther circuit block diagram of the image display device in
[Explanation of symbols]
  10 Image signal
  20, 21, 25 Tilt detection means
  30, 31, 35 Motion detection means
  40 Conversion table determination means
  41, 45 Correction area detection means
  55 Correction pattern determination means
  61, 62, 65, 100 gradation correction means
  71, 75 Image signal selection means
  80 Subfield encoding means
  90 Plasma display
  612, 622 Correction value generating means
  613, 623 Correction value switching means
  614, 617 addition means
  615 Subtraction means
  616 Delay means

Claims (3)

In an image display device that displays a multi-tone by configuring one field with a plurality of sub-fields and controlling each sub-field to be turned on or off , an area having a gradient in gradation value is detected from an image signal and Inclination detecting means for detecting the magnitude and direction of the inclination of the inclined area, and motion detecting means for detecting the area with movement from the image signal and detecting the magnitude and direction of the movement of the area with movement And a gradation correcting means for correcting a predetermined gradation to another gradation based on the output of the inclination detecting means and the output of the motion detecting means, and the gradation correcting means includes a region having an inclination. When moving in the lower gradation direction, the maximum intermediate astigmatism with the largest luminance weight among the non-lighting subfields with smaller luminance weights than the lit subfield with the largest luminance weight. When gradation correction is performed to disperse subfields to surrounding subfields and an inclined region moves in a higher gradation direction, a gradation in which a maximum intermediate non-lighting subfield with a large luminance weight exists, Alternatively , an image display device configured to perform gradation correction that disperses the maximum intermediate non-lighting subfield or the maximum lighting subfield with respect to the gradation at which the lighting subfield having the largest luminance weight is switched .   At least one of the gradations after correction is a subfield having a maximum luminance weight among non-lighting subfields having a luminance weight smaller than a lighting subfield having the maximum luminance weight with respect to the gradation before correction. The image display apparatus according to claim 1, comprising a gradation to be lit.   The image display device according to claim 2, wherein the average value of the gradation after correction is equal to the gradation before correction.

Images