JP4069103B2 - Image display device and driving method thereof - Google Patents

Description

  The present invention relates to an image display device and a driving method thereof, and in particular, a field such as a plasma display panel (PDP) is divided into a plurality of weighted subfields, and the plurality of subfields are combined and displayed. The present invention relates to an image display device that performs multi-gradation display on a panel and a driving method thereof.

  2. Description of the Related Art In recent years, with the increase in size of display devices, thin display devices are required, and various types of thin display devices are provided. For example, matrix panels for displaying digital signals as they are, that is, gas discharge panels such as PDP, matrix panels for DMD (Digital Micromirror Device), EL (Electro-Luminescence) display elements, fluorescent display tubes, liquid crystal display elements, etc. Is provided. Among such thin display devices, the gas discharge panel is easy to enlarge because of a simple process, is self-luminous, has good display quality, and has a high response speed. It has been put to practical use as a large-screen direct-view HDTV (high-definition television) display device.

  For example, the plasma display apparatus includes a plurality of weighted subfields (SF: light emission blocks) configured by a plurality of sustain discharge pulses (sustain pulses) in each field (frame), and each subfield is turned on or off. By turning on the light, the image display is performed with multi-gradation control. In such an image display device that performs multi-gradation display by controlling lighting / non-lighting of a plurality of subfields, false contour (pseudo contour) noise is generated in the contour portion of a moving image, and thus the configuration is simple. There has been a demand for providing an image display apparatus capable of reducing false contours and a driving method thereof.

  Conventionally, in a plasma display device, a liquid crystal display device, an EL display device, etc., one field is divided into a plurality of subfields having a predetermined luminance ratio (weight), and each image display cell is turned on in units of subfields having a predetermined weight. There is provided an image display device (multi-tone image display device) that encodes a state or a non-lighted state and performs image display by controlling multi-gradation. In an image display apparatus that divides one field into a plurality of weighted subfields and combines the plurality of subfields to perform multi-gradation display on the display panel, the screen size of the display panel, the number of pixels, or actually Although it is caused by the displayed video (image), a person (viewer) watching the image display device follows a target moving in the display panel exceeding a certain speed with a line of sight. Will recognize false contours.

  As a method for reducing the false contour, a dither method, a superposition method, or a path switching method has been proposed. However, it is not satisfactory, and conversely, the dither method and the superposition method are hatched. Side effects such as the appearance of noise and the appearance of granular noise due to sub-path error diffusion also occur in the path switching method.

  2. Description of the Related Art Conventionally, an image display apparatus that divides one field into a plurality of weighted subfields and combines the plurality of subfields to perform multi-gradation display on a display panel. In order to prevent the occurrence of the above, the sustain period of each subfield period is set to substantially the same length within one field period, and the image data is expressed in N + 1 gradations with luminance levels from 0 to N on the display panel. There has been proposed an image display apparatus configured to perform the above. (For example, refer to Patent Document 1).

  Further, conventionally, an image display apparatus that divides one field into a plurality of weighted subfields and combines the plurality of subfields to perform multi-gradation display on a display panel, and is capable of generating false contour noise. There has also been proposed an image display device that performs a diffusion process for reducing false contour noise on a region that is obtained as a noise amount and is predicted to generate a false contour based on the value of the noise amount. (For example, refer to Patent Document 2).

  Further, it is a conventional image display apparatus that divides one field into a plurality of weighted subfields and combines the plurality of subfields to perform multi-gradation display on a display panel, which reduces false contours and reduces pattern noise. In order to suppress the occurrence of video and improve the image quality of moving image display, the display image is a pixel of a gradation in which only one of a plurality of subframes having the same luminance weight according to the superposition method is lit, and between adjacent pixels There has also been proposed an image display device in which the superposition method is applied only to a region where the luminance gradient is a value within a set range. (For example, refer to Patent Document 3).

Japanese Patent Laid-Open No. 10-031455 Japanese Patent Laid-Open No. 11-231827 JP 2002-372948 A

  As described above, conventionally, an image display apparatus that divides one field into a plurality of weighted subfields and combines the plurality of subfields to perform multi-gradation display on the display panel has a problem of false contours. It was. As methods for reducing false contours, the dither method, the overlay method, or the path switching method is known. For example, in the overlay method, hatched noise is recognized in moving images as a side effect of the overlay. There is a problem of being done. This hatched noise is recognized when the image moves slowly, but has a characteristic that it is difficult to recognize when the image moves relatively quickly. This is considered to be because, when the image is moving fast, the line of sight moves across a plurality of pixels, so that hatched noise is canceled out.

  In Patent Document 1 described above, false contours can be prevented by switching between the main path and the sub path, but the moving image area is large in the moving image, and noise due to error diffusion of the sub path is noticed regardless of the speed of movement. Furthermore, since the switching shock between the sub path and the main path (granular noise of error diffusion of the sub path with respect to the smooth gradation expression of the main path) is large, the viewer is given an uncomfortable feeling as an image.

  Further, Patent Document 2 is for reducing false contour noise in a region where false contour noise may occur based on a prediction result by the false contour noise detection device, but based on the output of a motion detector. For each subfield, a logical operation of the pixel value between each pixel of the input image divided into a plurality of subfields by the false contour determiner is performed for each subfield, and a place where a spatial false contour is generated is detected. Modulation processing for false contour reduction is performed. However, since it is known that a false contour is generated when a moving image is displayed and a predetermined gradation is driven, a false contour noise detection device is not necessary, and it is sufficient that the amount of motion can be detected, and the configuration becomes redundant. ing.

  Further, in Patent Document 3, although the hatched noise by the moving image portion specific gradation superposition method can be reduced, even if the images move at the same speed, the false contours are easily noticeable. If the image is conspicuous and does not exceed the determination threshold for overlapping, the false contour is recognized without being superimposed. Further, even if the false contour is not conspicuous, if the determination threshold for superimposing is exceeded, the superposition may be performed and hatched noise may be recognized. The intensity of the hatched noise cannot be controlled and is determined depending on the lighting pattern.

  As described above, all of the conventional methods for reducing false contours detect a place where a false contour occurs and apply modulation to the place, so that the circuit scale increases and the cost increases. It was. Furthermore, the conventional method has a problem that new noise is generated as a side effect of reducing false contours.

  In view of the problems of the conventional technology for reducing the false contour described above, the present invention can improve the image quality of moving image display by reducing the false contour without generating new noise or increasing the circuit scale. An image display apparatus and a driving method thereof are provided.

  According to the first aspect of the present invention, there is provided an image display device that divides one field into a plurality of weighted subfields and combines the plurality of subfields to perform multi-gradation display on a display panel. A motion amount detection circuit that detects a motion amount from a current field and a field before the current field from an image signal, and false contour noise in the vicinity based on the gradation of the input image signal and the detected motion amount There is provided an image display device comprising: a diffusion amount calculation circuit that calculates a diffusion amount for diffusion; and a diffusion circuit that performs diffusion processing using the diffusion amount calculated by the diffusion amount calculation circuit.

  According to a second aspect of the present invention, there is provided an image display device that divides one field into a plurality of weighted subfields and combines the plurality of subfields to perform multi-gradation display on a display panel. One of a main path for generating a signal with a predetermined number of gradations from an image signal, a sub path for generating a signal with a smaller number of gradations than the main path, and a generation signal for the main path and a generation signal for the sub path. A path switch circuit for switching and outputting, a motion amount detection circuit for detecting a region moving between the current field and a field before the current field from the input image signal, and outputting a motion amount that is a moving amount; , A level detection circuit for detecting the level amount of false contour strength when moving image false contour occurs in the main path, the detected motion amount and the detected level And a sub-path determination circuit that determines a gradation having a strong false contour generation intensity in the moving image region, and the path switch circuit is determined from the output of the main path based on the determination result of the sub-path determination circuit. A sub path switch for switching to the output of the sub path, a diffusion coefficient generation circuit for generating a diffusion coefficient depending on the gradation of the input image signal for calculating a diffusion amount for diffusing false contour noise to the periphery, and the amount of motion A diffusion amount calculation circuit that calculates a diffusion amount based on the diffusion coefficient; and a diffusion circuit that performs a diffusion process using the diffusion amount calculated by the diffusion amount calculation circuit, and controls the subpath switch and the diffusion amount. An image display device characterized by reducing false contours is provided.

  According to a third aspect of the present invention, there is provided an image display device that divides one field into a plurality of weighted subfields and combines the plurality of subfields to perform multi-gradation display on a display panel. A main path for generating a signal having a predetermined number of gradations from an image signal, a sub path for generating a signal having a smaller number of gradations than the main path, and a diffusion for generating a signal obtained by performing diffusion processing on the input image signal A processing path; a path switch circuit that switches and outputs one of the main path generation signal, the sub path generation signal, and the diffusion processing path generation signal; and a current field and the current field from the input image signal A motion detection circuit that detects a moving area between earlier fields and outputs a moving amount that is a moving amount, and generates a false contour in the main path. A level detection circuit for detecting the level amount of the false contour strength in the case of comparing with a predetermined set value based on the detected motion amount and the detected level amount, A path switching determination circuit for determining a strong gradation, and a path switching circuit for switching the path switch circuit to any one of the output of the main path, the output of the sub path, or the diffusion processing path based on the determination result of the sub path determination circuit A diffusion coefficient generation circuit for generating a diffusion coefficient depending on the gradation of the input image signal for calculating a diffusion amount for diffusing false contour noise to the periphery, and a diffusion amount based on the motion amount and the diffusion coefficient And a diffusion circuit that performs diffusion processing with the diffusion amount calculated by the diffusion amount arithmetic circuit, and controls the path switching circuit and the diffusion amount. Reducing the false contour image display device comprising it is provided with.

  According to a fourth aspect of the present invention, there is provided a driving method for an image display device in which one field is divided into a plurality of weighted subfields, and the plurality of subfields are combined to perform multi-gradation display on the display panel. A motion amount detecting step for detecting a motion amount from the current field and a field before the current field from the input image signal, and a false contour noise based on the gradation of the input image signal and the detected motion amount There is provided a method for driving an image display device, comprising: a diffusion amount calculating step for calculating a diffusion amount for diffusing the light to the periphery; and a diffusion step for performing a diffusion process based on the calculated diffusion amount.

  According to the fifth aspect of the present invention, one field is divided into a plurality of weighted subfields, and the plurality of subfields are combined to perform multi-gradation display on the display panel. A path switching that outputs a main path that generates a signal of a logarithm, a sub path that generates a signal having a smaller number of gradations than the main path, and a switching signal that is generated from the main path or the sub path. A method of driving an image display apparatus comprising: a step of detecting a region moving between a current field and a field before the current field from the input image signal, and outputting a movement amount that is a movement amount. A motion amount detection step, a level detection step of detecting a level amount of false contour strength when a video false contour occurs in the main path, and the detected motion And a predetermined setting value based on the detected level amount, a sub-path determination step for determining a gradation with a strong false contour generation intensity in a moving image region, and the path switching step based on the determination result of the sub-path determination step. A sub-path switching stage for switching from the output of the main path to the output of the sub-path, and a diffusion coefficient generation for generating a diffusion coefficient depending on the gradation of the input image signal for calculating a diffusion amount for diffusing false contour noise to the periphery A diffusion amount calculation step of calculating a diffusion amount based on the motion amount and the diffusion coefficient, and a diffusion step of performing diffusion processing based on the diffusion amount, and controlling the subpath switch and the diffusion amount to false Provided is a method for driving an image display device characterized in that the contour is reduced.

  According to the sixth aspect of the present invention, one field is divided into a plurality of weighted subfields, and the plurality of subfields are combined to perform multi-gradation display on the display panel. A main path for generating a logarithmic signal, a sub path for generating a signal having a smaller number of gradations than the main path, a diffusion processing path for generating a signal obtained by performing diffusion processing on the input image signal, and the main path And a path switching stage for switching and outputting any one of a path generation signal, the sub path generation signal, and the diffusion processing path generation signal. A motion detection step of detecting a region moving between the field and a field before the current field, and outputting a motion amount that is a motion amount; A level detection step for detecting a level amount of false contour strength when a moving image false contour occurs in a pass, and a moving image region that is compared with a predetermined set value based on the detected motion amount and the detected level amount. And a path switching determination stage for determining a gray level having a strong false contour generation intensity, and the path switching stage is selected from the main path output, the sub path output, and the diffusion processing path according to the determination result of the sub path determination stage. A path switching step for switching to one, a diffusion coefficient generation step for generating a diffusion coefficient depending on the gradation of the input image signal for calculating a diffusion amount for diffusing false contour noise to the periphery,

  A diffusion amount calculation step of calculating a diffusion amount based on the motion amount and the diffusion coefficient; and a diffusion step of performing a diffusion process with the diffusion amount calculated in the diffusion amount calculation step, the path switching step and the diffusion There is provided a method of driving an image display device characterized by controlling the amount to reduce false contours.

  According to the present invention, it is possible to provide an image display apparatus and a driving method thereof that can improve the image quality of moving image display by reducing false contours without generating new noise or increasing the circuit scale.

Hereinafter, embodiments of an image display apparatus and a driving method thereof according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram schematically showing an example of an image display apparatus to which the present invention is applied. In FIG. 1, reference numeral 1 is a digital video (image) signal input terminal, 2 is a horizontal synchronization signal, vertical synchronization signal, a display period signal indicating a display period and a synchronization signal input terminal such as a clock signal, and 3 is a multi-gradation 4 is a field memory, 5 is a drive control circuit, 6 is a timing generation circuit, and 7 is a display panel.

  The field memory 4 can store image data for two fields, and after storing data for one field, sequentially stores data for each subfield (SF) of the stored one field in the next field period. Is read out. The timing generation circuit 6 is a circuit that generates various timing signals such as a synchronization signal. The clock signal CLK, the horizontal synchronization signal Hsync, the vertical synchronization signal Vsync, and the like are supplied to the multi-gradation signal processing circuit 3 via a terminal 6T. To supply. The display panel 7 is a display panel such as a plasma display panel (PDP), for example, and includes various drivers (for example, an X driver, a Y driver and an address driver in a three-electrode AC drive type PDP). .

FIG. 2 is a block diagram showing an example of the multi-gradation signal processing circuit 3 as the first embodiment of the image display apparatus according to the present invention.
The multi-gradation signal processing circuit 3 includes three primary color video signals (red: Ri, green: Gi, blue: Bi) supplied from the video signal input terminal 1 and the timing generation circuit 6 via the terminal 6T. The received clock signal CLK, horizontal synchronization signal Hsync, vertical synchronization signal Vsync, and the like are received and converted into multi-gradation processing for each primary color and converted into subfield lighting / non-lighting data (red: Ro, (Green: Go, Blue: Bo) is output to the field memory 4.

  That is, as shown in FIG. 2, the multi-gradation signal processing circuit 3 according to the first embodiment includes a path (main path) 20 and an SF encoding circuit provided for each primary color (for example, red: R). 40 and a motion amount detection circuit 50 are provided. The motion amount detection circuit 50 receives input video signals (input image signals) Ri, Gi, Bi of three primary colors and timing signals (synchronization signals) CLK, Hsync, Vsync, The motion amount MV is detected from the field before the current field. The path 20 receives the corresponding primary color input video signal (for example, Ri), the timing signal, and the motion amount MV detected by the motion amount detection circuit 50 and outputs the signal MP to the SF encoding circuit 40. The SF encoding means 40 receives the signal MP from the path 20 and outputs a signal (for example, Ro) converted into lighting / non-lighting data for each corresponding primary color subfield. Such a pass 20 and SF encoding circuit 40 are provided for each primary color, and SF-encoded signals Ro, Go, Bo for each primary color are obtained.

  FIG. 3 is a block diagram showing an example of a path (main path) 20 in the multi-gradation signal processing circuit shown in FIG. Here, in the following description, the case where the diffusion circuit is dither will be described as an example. The configuration of the path 20 is the same for each of the signals of the three primary colors, and in the following, description will be made mainly using red (R) as an example.

  As shown in FIG. 3, the path 20 includes a gain control circuit 200, an error diffusion circuit 201, a dither circuit 202, a dither switching circuit 203, and a dither switching determination circuit 204. The gain control circuit 200 receives the input video signal (Ri) of each primary color, performs gain control, and supplies the gain-controlled video signal to the error diffusion circuit 201. The error diffusion circuit 201 performs error diffusion processing on the gain-controlled video signal, and supplies the signal MPL on which the error diffusion processing has been performed to the dither circuit 202 and the dither switching circuit 203.

  The dither circuit 202 performs conventionally known dither processing, and a signal MPD that has been dithered by the dither amount DL by the dither circuit 202 is also supplied to the dither switching circuit 203. Based on the motion amount MV detected by the motion amount detection circuit 50, the dither switching determination circuit 204 outputs “1” when the motion amount MV is equal to or greater than a predetermined threshold TD, and the motion amount MV is a predetermined amount. If it is smaller than the threshold value TD, “0” is output. The dither switching circuit 203 selects the output signal MPL of the error diffusion circuit 201 when the output of the dither switching determination circuit 204 is “0” according to the output of the dither switching determination circuit 204, and the output of the dither switching determination circuit 204 When “1” is “1”, the output MPD of the dither circuit 202 is selected and supplied to the SF encoding circuit 40 as the output signal MP of the path 20.

FIG. 4 is a block diagram showing an example of the motion amount detection circuit 50 in the multi-gradation signal processing circuit shown in FIG.
As shown in FIG. 4, the motion amount detection circuit 50 includes an RGB matrix circuit 500, an edge detection circuit 501, a motion region detection circuit 502, and a motion amount determination circuit 503. The RGB matrix circuit 500 generates a luminance signal Y from the three primary color video signals Ri, Gi, Bi supplied from the video signal input terminal 1 and supplies the luminance signal Y to the edge detection circuit 501 and the motion region detection circuit 502. The motion amount determination circuit 503 outputs a motion amount MV based on the output of the edge detection circuit 501 and the output of the motion region detection circuit 502.

  Here, FIG. 4 shows a case where the amount of movement MV is determined and output from the luminance signal Y, and the RGB matrix circuit 500 is used, but the movement is performed for each primary color R, G, B signal. The amount may be determined and output. In this case, an edge detection circuit 501, a motion region detection circuit 502, and a motion amount determination circuit 503 are required for each primary color signal.

  FIG. 5 is a diagram showing an example of SF conversion data stored in the SF encoding circuit in the multi-gradation signal processing circuit shown in FIG. 2, and an encoding conversion data table stored in the SF encoding circuit 40. , And an example of a dither coefficient which is a level amount and a diffusion coefficient. In addition, the code | symbol (circle) in FIG. 5 shows lighting. Specifically, in FIG. 5, for example, the subfields SF1, SF3, and SF5 are turned on for the gradation 17, and the subfields SF1 to SF8 are turned on for the gradation 87. Further, FIG. 5 shows a state in which the level amount (LV) is set to 3 in the gradation 17 and the dither coefficient (DK) is set to 2 in the gradation 87, and the dither amount DL is the dither amount. Dither processing is performed by calculation of the coefficient DK and the predetermined value A (DL = DK × A). Then, the signal MP from the path 20 is converted into 147 gradations by the encoded conversion data table shown in FIG.

  Here, in FIG. 5, SF indicates the order of driving by the drive control circuit 5, SF1 is a subfield driven first, SF2 is a subfield driven second, and SF9 is ninth. And SF10 is the last driven subfield. Each subfield SF1 to SF10 is weighted, and SF1: SF2: SF3: SF4: SF5: SF6: SF7: SF8: SF9: SF10 = 1: 2: 4: 8: 12: 16: 20: The weight is set to 24:28:32. The weighting of each of the subfields SF1 to SF10 corresponds to the ratio of the light emission amount between the subfields. For example, the number of gradations of the input video signal (Ri) supplied to the gain control circuit 200 of the path 20 is 9 bits. In the case of the maximum gradation 511, the gain control circuit 200 performs gain control to increase 147/511 times.

FIG. 6 is a diagram showing an example of a drive sequence of the drive control circuit 5 in the image display apparatus according to the present invention.
As shown in FIG. 6, in the driving sequence, for example, one field is divided into ten subfields SF1 to SF10, and display is performed by combining subfields that emit light for each display cell. Each of the subfields SF1 to SF10 includes a reset period TS for initializing all display cells, an address period TA set to a state corresponding to an image for displaying all display cells, and each display cell according to the set state. And a sustain period (sustain discharge period) TS. Here, the sustain period (number of sustain pulses) of each of the subfields SF1 to SF10 corresponds to the ratio of the light emission amount (weighting) between the subfields. As described above, for example, SF1: SF2: SF3: SF4. : SF5: SF6: SF7: SF8: SF9: SF10 = 1: 2: 4: 8: 12: 16: 20: 24: 28: 32 It is determined according to the weight ratio. The reset period TR, the address period TA, and the sustain period TS in each of the subfields SF1 to SF10 are generated by the timing generation circuit 6.

FIG. 7 is a block diagram showing another example of the path (main path) 20 in the multi-gradation signal processing circuit as the second embodiment of the image display apparatus according to the present invention.
As is clear from the comparison between FIG. 7 and FIG. 3, the path 20 in the multi-gradation signal processing circuit 3 of the second embodiment is the dither circuit 202 in the first embodiment described above with reference to FIG. Instead of the dither switching circuit 203 and the dither switching determination circuit 204, a motion adaptive dither circuit 205 is provided. The gain control circuit 200 and the error diffusion circuit 201 are the same as those described above, and a description thereof is omitted.

The motion adaptive dither circuit 205 varies the dither amount according to the motion amount MV that is the output of the motion amount detection circuit 50 and outputs the signal MP to the field memory 40.
FIG. 8 is a block diagram showing an example of the motion adaptive dither circuit 205 in the path 20 of the multi-gradation signal processing circuit shown in FIG.

  As shown in FIG. 8, the motion adaptive dither circuit 205 includes a dither coefficient generation circuit 51, a dither amount calculation circuit 52, and a dither circuit 53. The dither circuit 53 includes a dither amount addition circuit 531, a dither amount subtraction circuit 532, a horizontal counter 533, a vertical counter 534, and an addition / subtraction selection circuit 535. The output signal (video signal) MPL of the error diffusion circuit 201 is supplied to the dither coefficient generation circuit 51, the dither amount addition circuit 531, the dither amount subtraction circuit 532, and the addition / subtraction selection circuit 535.

  The dither coefficient generation circuit 51 outputs a dither coefficient DK having a so-called modulation amount to the dither amount calculation circuit 52 at a ratio of the strength with which it is desired to apply the dither for spreading. Here, as shown in FIG. 5, a predetermined modulation amount may be output for the gradation. The dither amount calculation circuit 52 calculates a dither amount DL, which is a diffusion amount, based on the motion amount MV that is the output of the motion amount detection circuit 50 and the dither coefficient DK, and outputs the dither amount DL to the dither amount addition circuit 531 and the dither amount subtraction circuit 532. To do. Note that the calculation of the dither amount DL in the dither amount calculation circuit 52 is performed by DL = MV × DK, and the calculated dither amount DL is output to the dither circuit 53.

  The dither amount adding circuit 531 adds the dither amount DL calculated by the dither amount calculating circuit 52 to the signal MPL, and the dither amount subtracting circuit 532 is calculated by the dither amount calculating circuit 52 for the signal MPL. The dither amount DL is subtracted. The addition / subtraction selection circuit 535 selects either the output signal of the dither amount addition circuit 531, the output signal of the dither amount subtraction circuit, or the output signal MPL of the error diffusion circuit 201 according to the outputs of the horizontal counter 533 and the vertical counter 534. Then, the signal MP is output to the SF encoding circuit 40.

  FIG. 9 is a diagram for explaining the dither operation in one field performed by the dither amount calculation circuit 52 in the dither circuit 202 shown in FIG. 3 and the motion adaptive dither circuit 205 shown in FIG. The result is shown. Here, in FIG. 9A, + DL and -DL are repeated in the horizontal direction, and + DL and -DL are repeated in the vertical direction. In FIG. 9B, 2 × 2 4 pixels are defined as one block, and + DL and −DL are switched according to a predetermined rule in which one + DL and −DL are included in one block. Note that the size of one block is not limited to 2 × 2 four pixels, and may be larger, as long as the sum of + DL and −DL for adding and subtracting dither becomes zero.

FIG. 10 is a diagram for explaining the relationship between the gradation and the dither coefficient in the driving method of the image display apparatus according to the present invention. Here, FIG. 10A shows a case where the dither coefficient DK is fixed with respect to the gradation, FIG. 10B shows a case where the dither coefficient DK is proportional to the gradation, and FIG. (C) shows a case where the dither coefficient DK is logarithmically related to the gradation.
As shown in FIG. 10A, when the dither coefficient DK is fixed with respect to the gradation, the circuit scale can be reduced.

  By the way, since the human eye becomes more difficult to recognize the luminance difference as the luminance is larger, for example, even if the luminance difference between the gradation 3 and the gradation 4 can be recognized, the luminance difference between the gradation 140 and the gradation 141 cannot be recognized. Disappear. As shown in FIG. 10C, the logarithmic relationship of the dither coefficient DK with respect to the gradation takes into account that the sense of the luminance of the human eye is proportional to the logarithm of the luminance from Weber-Fechner's law. It is ideal for the sense of brightness of the human eye. In this case, the dither coefficient orientation circuit 51 is constituted by a ROM or the like, for example. Further, as shown in FIG. 10B, the proportional relationship of the dither coefficient DK with respect to the gradation corresponds to the case between the above-described FIG. 10A and FIG. 10C.

  FIG. 11 is a block diagram showing another example of the motion adaptive dither circuit 205 in the path 20 of the multi-gradation signal processing circuit 3 shown in FIG. Note that the motion adaptive dither circuit 205 shown in FIG. 11 is also a gradation adaptive dither circuit.

  As shown in FIG. 11, the motion adaptive dither circuit 205 includes a dither circuit 53, n dither gradation setting circuits 54-1 to 54-n, n dither coefficient setting circuits 55-1 to 55-n, n dither gradation comparison circuits 56-1 to 56-n, a dither coefficient selection circuit 57, and a dither amount calculation circuit 58 are provided. Here, the configuration of the dither circuit 53 is the same as that described with reference to FIG. 8, and the description thereof is omitted.

  The dither gradation setting circuit 54-1 sets the first gradation to which dither is applied, and the dither gradation setting circuit 54-2 sets the second gradation to which dither is applied, The dither gradation setting circuit 54-n sets the nth gradation for which dither is to be applied. The dither coefficient setting circuit 55-1 sets the dither coefficient for the first gradation, the dither coefficient setting circuit 55-2 sets the dither coefficient for the second gradation, and The dither coefficient setting circuit 54-n sets a dither coefficient for the nth gradation.

  Specifically, in the case of the SF conversion data shown in FIG. 5, the dither gradation setting circuit 54-1 sets the gradation 3, and the dither coefficient setting circuit 55-1 sets the dither coefficient “1”. The gradation setting circuit 54-6 sets the gradation 43, the dither coefficient setting circuit 55-6 sets the dither coefficient “2”, and the dither gradation setting circuit 54-15 sets the gradation 111. The dither coefficient setting circuit 55-15 sets the dither coefficient “3”. In the case of the SF conversion data shown in FIG. 5, the number of gradations to which dither is applied (gradation with “1”, “2” or “3” as the dither coefficient) is 19 (n is 19). Therefore, 19 dither gradation setting circuits 54-1 to 54-19, dither coefficient setting circuits 55-1 to 55-19 and dither gradation comparison circuits 56-1 to 56-19 are required.

  Here, the gradation to which dither is applied is a gradation in which a false contour is easily recognized. The dither coefficient indicates the ratio of the strength of applying dither to the gradation to which dither is to be applied. This dither coefficient is not limited to “1”, “2”, or “3”. Absent. Furthermore, the gradation to which dither is applied can be changed variously depending on the SF conversion data (driving sequence) to be applied.

  The dither gradation comparison circuits 56-1 to 56-n compare the corresponding dither gradation setting circuits 54-1 to 54-n with the output signal (input signal of the motion adaptive dither circuit 205) MPL of the error diffusion circuit 201. If both match, “1” is output, and if they do not match, “0” is output. The dither coefficient selection circuit 57 outputs signals corresponding to the dither gradation comparison circuits 56-1 to 56-n that output “1” to the dither amount calculation circuit 58, and the dither amount calculation circuit 58 outputs the signal “1”. The dither amount DL is calculated by using the dither coefficients set in the dither coefficient setting circuits 55-1 to 55-n corresponding to the dither gradation comparison circuits 56-1 to 56-n that output. Here, the calculation of the dither amount DL in the dither amount calculation circuit 58 can be performed, for example, by applying one of the methods shown in FIG. The calculation of the dither amount DL in the dither amount calculation circuit 58 is performed by DL = MVC × DK, and the calculated dither amount DL is output to the dither circuit 53. That is, when calculating the dither amount DL, the motion amount MV is once converted into a practical motion amount MVC suitable for practical use, and the dither amount DL is obtained using the calculated motion amount MVC.

FIG. 12 is a diagram showing the relationship between the motion amount MV of the input image signal and the calculated motion amount MVC in the image display apparatus according to the present invention.
FIG. 12A is a diagram illustrating a first calculation method of the calculated motion amount MVC with respect to the motion amount MV. When the motion amount MV is smaller than a predetermined threshold TD, the calculated motion amount MVC is set to zero, and the motion amount When MV is equal to or greater than a predetermined threshold TD, the calculated motion amount MVC is fixed to a predetermined value DFL. FIG. 12B is a diagram showing a second calculation method of the calculated motion amount MVC with respect to the motion amount MV, and the motion amount MV and the calculated motion amount MVC are in a proportional relationship.

  FIG. 12C is a diagram showing a third calculation method of the calculated motion amount MVC with respect to the motion amount MV. When the motion amount MV is smaller than a predetermined threshold TD, the calculated motion amount MVC is set to zero, and the motion amount When MV is equal to or greater than a predetermined threshold TD, the motion amount MV and the calculated motion amount MVC are in a proportional relationship. FIG. 12D is a diagram showing a fourth calculation method of the calculated motion amount MVC with respect to the motion amount MV. When the motion amount MV is smaller than a predetermined threshold TD, the calculated motion amount MVC is set to zero, and the motion amount When MV is equal to or greater than a predetermined threshold TD, the calculated motion amount MVC is proportional to MV-TD.

  FIG. 13 is a block diagram showing an example of the multi-gradation signal processing circuit 3 as a third embodiment of the image display apparatus according to the invention. In FIG. 13, reference numeral 10 is a sub path, 20 is a main path, 30 is a path switch circuit, 40 is an SF encoding circuit, and 50 is a motion amount detection circuit. That is, the third embodiment shown in FIG. 13 shows a case in which the present invention is applied to an image display apparatus using a path switching method.

  As is clear from a comparison between FIG. 13 and FIG. 2 described above, the multi-gradation signal processing circuit 3 of the third embodiment includes a sub path 10 and a main path 20 for each primary color. Any one of the outputs is selected by the path switch circuit 30 and supplied to the SF encoding circuit 40. Here, the sub path 10 is for displaying an input image signal at a predetermined gradation level (for example, a gradation level lower than the gradation level of the input image signal), and the main path 20 is an input. The image signal can be displayed at the actual display gradation level. Then, the path switch circuit 30 selects one output signal of the sub path 10 or the main path 20 according to the motion amount MV detected by the motion amount detection circuit 50 and outputs the selected output signal to the SF encoding circuit 40.

  FIG. 14 is a block diagram showing an example of the sub path 10 in the multi-gradation signal processing circuit shown in FIG. Here, the sub-pass circuit 10 is configured to express an image using a lighting pattern that does not generate a false contour. For example, in the case of the SF conversion data of FIG. , 15, 27, 43, 63, 87, 111, 147 are used, and between these gradations is expressed by error diffusion.

  As shown in FIG. 14, the subpath 10 includes a distortion correction circuit 100, a gain control circuit 101, an error diffusion circuit 102, and a data matching circuit 103. The distortion correction circuit 100 does not increase the number of gradations that can be expressed by the sub-path 10 equally with the luminance amount, and thus corrects the display characteristic after error diffusion and the inverse function to obtain a linear display characteristic as a whole. This is a circuit for performing correction. The gain control circuit 101 multiplies the input image signal by a predetermined gain coefficient so that the error diffusion circuit 102 in the subsequent stage can perform error diffusion processing over the entire area of the input image signal. The gain control circuit 101 can be configured by a general multiplier, ROM, RAM, or the like.

  The error diffusion circuit 102 performs error diffusion on the image signal obtained via the gain control circuit 101, thereby generating a pseudo halftone and increasing the number of gradations. The data matching circuit 103 is provided to match the luminance level in the sub path 10 with the luminance level in the main path 20.

  FIG. 15 is a block diagram showing an example of the path switch circuit 30 in the multi-gradation signal processing circuit shown in FIG.

  As shown in FIG. 15, the path switch circuit 30 includes a level detection circuit 300, a sub path determination circuit 301, and a sub path switch 302. The level detection circuit 300 detects a gradation at which a false contour is likely to appear for each pixel, and outputs a generated intensity (level amount) LV when the false contour is generated. The sub path determination circuit 301 outputs a path determination signal PSW based on the output LV of the level detection circuit 300 and the output (motion amount) MV of the motion amount detection circuit 50. In response to the subpath determination signal PSW input from the subpath determination circuit 301, for example, the subpath switch 302 selects the output SP of the subpath 10 when the subpath determination signal PSW is “1”, and the subpath determination signal PSW. Is “0”, the output MP of the main path 20 is selected and output to the SF encoding circuit 40.

  Here, the path determination signal PSW outputs “1” when the motion amount MV is greater than or equal to the predetermined value TMP and the level amount LV is greater than or equal to the predetermined value TLP, and the motion amount MV is greater than the value TMP. Or “0” is output when the level amount LV is smaller than the value TLP. The value TMP and the value TLP differ depending on the screen size of the display panel 7, the number of pixels, and the like, and values determined based on empirical rules are used. Specifically, for example, in the SF conversion data of FIG. 5 described above, the level amount LV is determined from “0” to “5” for each gradation. The value “0” to “5” of the level amount LV is a numerical value indicating the strength when the false contour is recognized, and “5” is set to the gradation when the recognized false contour is the strongest. .

  Next, the generation intensity of the false contour will be described. In a moving image, when a predetermined gradation is straddled between adjacent pixels of the video signal, a person (a person watching the image display device) recognizes a false contour. Here, the predetermined gradation is where there is a carry between the upper and lower gradations. For example, in the SF conversion data of FIG. 5, gradations 4, 8, 16, 28, 44, 64, 88 and 112 are used. is there. These gradations are first carry gradations, and false contours are easily recognized. Also, gradations 32, 48, 68, 92 and 120 are second carry gradations, and false contours are easily recognized, but false contours are not as strong as the first gradation.

  As described above, in FIG. 5, the level amount LV is shown in five levels as the strength when a false contour occurs, and the level amount LV of the gradations 44, 64, 88 and 112 is “5”. Furthermore, the level amount LV of the gradations 45, 65, 89, and 113 that is one level higher is also set to “5”. This is because, when there is a carry between adjacent pixels in the actual video signal, the gradation that the digit is raised is not necessarily the above-described gradation 44, 64, 88, or 112. The key level amount LV is also set to “5”.

  The level amount LV “1” or more is a gradation with a subfield carry in the lighting pattern in the upper and lower gradations, and the level amounts LV “4”, “3”, “2”, “1” are also included. The level is the same for continuous tone. A place where a carry occurs between adjacent pixels may be detected without detecting the level amount LV.

  FIG. 16 is a flowchart showing an example of the processing of the path (main path) 20 in the multi-gradation signal processing circuit as the first embodiment of the image display apparatus according to the present invention shown in FIG. This is for explaining the processing of the dither switching determination circuit 204.

  First, when the processing is started in step 110, the process proceeds to step 111 for initialization, and the dither switching determination circuit 204 outputs “0”. In step 112, the dither switching circuit 203 selects the output signal MPL from the error diffusion circuit 201. Next, the routine proceeds to step 113, where the motion amount MV is detected, and further, at step 114, addition / subtraction of the dither amount DL is performed. As the dither coefficient DK, any of the above-described FIG. 10A to FIG. 10C may be applied, or the dither coefficient of FIG.

  Further, the process proceeds to step 115, where the amount of motion MV is compared with a predetermined threshold (determination threshold) TD. If it is determined in step 115 that the motion amount MV is smaller than the determination threshold value TD, the process proceeds to step 116, where the dither switching determination circuit 203 outputs “0”, and further proceeds to step 117, where the dither switching circuit 203 selects the output signal MPL of the error diffusion circuit 201 and returns to step 113. On the other hand, if it is determined in step 115 that the motion amount MV is greater than or equal to the determination threshold TD, the process proceeds to step 118, where the dither switching determination circuit 203 outputs “1”, and further proceeds to step 119, where The switching circuit 203 selects the output signal MPD of the dither circuit 202 and returns to step 113. Here, the above processing is performed for each pixel, for each predetermined region, or for each primary color signal. The output signal MPL of the error diffusion circuit 201 selected by the dither switching circuit 203 or the output signal MPD of the dither circuit 202 is supplied to the SF encoding circuit 40 as the output signal MP of the path (main path) 20.

  FIG. 17 is a flowchart showing an example of a path (main path) process in the multi-gradation signal processing circuit as the second embodiment of the image display apparatus according to the present invention shown in FIG. This is for explaining the processing. Here, FIG. 12C is applied to the relationship between the motion amount MV and the calculated motion amount MVC. As the dither coefficient DK, any of the above-described FIG. 10A to FIG. 10C may be applied, or the dither coefficient of FIG.

  First, when the process starts in step 120, the process proceeds to step 121 for initialization, the dither amount DL = 0, and the dither amount 0 is added or subtracted. That is, in step 121, the dither amount is not added or subtracted. Next, the process proceeds to step 122, where the motion amount MV is detected, and further, the process proceeds to step 123, where the motion amount MV is compared with the determination threshold value TD.

  If it is determined in step 123 that the motion amount MV is smaller than the determination threshold value TD, the process proceeds to step 124 where the calculated motion amount MVC = 0 and the process proceeds to step 126. On the other hand, if it is determined in step 123 that the motion amount MV is greater than or equal to the determination threshold value TD, the process proceeds to step 125 where the calculated motion amount MVC = m × MV is calculated, and the process proceeds to step 126. Here, m is a proportional coefficient between the motion amount MV and the calculated motion amount MVC.

  In step 126, the dither amount DL = DK × MVC is calculated, and the dither amount DL is added or subtracted. The output signal MP of the motion adaptive dither circuit 205 is supplied to the SF encoding circuit 40 as the output signal MP of the path (main path) 20.

  In the flowchart of FIG. 17, when the relationship between the motion amount MV and the calculated motion amount MVC is FIG. 12D, the calculation of the calculated motion amount MVC in step 125 is obtained by MVC = m × (MV−TD). It will be.

  FIG. 18 is a flowchart showing an example of processing in the multi-gradation signal processing circuit as the third embodiment of the image display apparatus according to the present invention shown in FIG. is there. Here, as the dither coefficient DK, any of the dither coefficients shown in FIGS. 10A to 10C or FIG. 5 may be applied, and the relationship between the motion amount MV and the calculated motion amount MVC. Any one of FIG. 12A to FIG. 12D may be applied.

  First, when the process starts in step 130, the process proceeds to step 131, where initialization is performed, the dither amount calculation circuit 58 (see FIG. 11) sets the dither amount DL = 0, and the output signal (path determination) of the subpath determination circuit 301 is performed. Signal) PSW is set to “0”. Next, the routine proceeds to step 132, where the dither amount DL is added or subtracted, and the subpath switch 302 selects the output signal MP of the main path 20.

  In step 133, the motion amount detection circuit 50 detects the motion amount MV, and in step 134, the level detection circuit 300 detects the level amount LV, and proceeds to step 135 to determine whether or not the level amount LV is zero. To do.

  If it is determined in step 135 that the level amount LV is zero, or if it is determined in step 135 that the level amount LV is not zero, and it is determined in step 136 that pMV + qLV is smaller than SPsel, In step 139, the movement amount MV is compared with a predetermined threshold (determination threshold) TD. On the other hand, if it is determined in step 135 that the level amount LV is not zero, and it is determined in step 136 that pMV + qLV is equal to or greater than SPsel, the process proceeds to step 137.

  Whether or not the level amount LV in step 135 is zero is determined in the sub path determination circuit 301. Further, p and q in step 136 are coefficients for balancing the movement amount MV and the level amount LV, and SPsel is a determination threshold value. Here, a large pMV + qLV indicates a gradation in which the amount of movement MV is large and a false contour is likely to be generated. In this case, the subpath switch 302 selects the output SP of the subpath 10.

  In step 137, the dither amount DL is calculated, and the subpath determination circuit 301 outputs a path determination signal PSW of “1”, and further proceeds to step 138 to perform addition / subtraction of the dither amount DL and the subpath switch 302. Selects the output signal SP of the subpath 10 and returns to step 133. That is, in step 138, since the subpath is selected by the subpath switch 302, the dither switching circuit 203 has no effect regardless of which is selected. In addition, the determination of whether or not the level amount LV in step 135 is zero is meaningless even if it is switched to the sub-pass 10 in the case of a gradation in which a false contour does not appear no matter how large the motion amount MV is (in general, This is to prevent the output signal SP of the sub-path 10 from being selected when the level amount LV is zero (switching to the sub-path 10 having a small number of gradations causes an increase in granular noise and deteriorates the image quality).

  If it is determined in step 139 that the motion amount MV is greater than or equal to the determination threshold value TD, the process proceeds to step 13A where the dither amount DL is calculated and the sub-path determination circuit 301 outputs a path determination signal PSW of “0”. Further, the process proceeds to step 13B where addition / subtraction of the dither amount DL is performed, and the sub path switch 302 selects the output signal MP of the main path 20 and returns to step 133.

  On the other hand, if it is determined in step 139 that the motion amount MV is smaller than the determination threshold value TD, the process proceeds to step 13C where the dither amount DL = 0 and the sub-path determination circuit 301 sets the path determination signal PSW of “0”. Further, the process proceeds to step 13D to add / subtract the dither amount DL, and the subpath switch 302 selects the output signal MP of the main path 20 and returns to step 133.

  In this way, one of the output signal SP of the sub-pass 10 in units of pixels, the output signal MPD that has been subjected to dither addition / subtraction in the main path 20 and the output signal MPL that is not subjected to dither addition / subtraction in the main path 20 is By selecting and switching based on the motion amount MV, the level amount LV, and the dither coefficient DK, it is possible to reduce the false contour by diffusing and modulating the place where the false contour occurs and scattering it around. . Since diffusion and modulation are performed based on the amount of movement MV, the intensity of false contour generation recognized by a person is determined as the speed at which a person follows a moving target, that is, the speed of the moving object increases. It can be controlled so that it is strongly recognized, and it is possible to avoid over-modulation or under-modulation by increasing or decreasing the dither amount according to the speed or amount of movement.

FIG. 19 is a block diagram showing still another example of the path (main path) 20 in the multi-gradation signal processing circuit as the fourth embodiment of the image display apparatus according to the present invention.
As apparent from the comparison between FIG. 19 and FIG. 3 described above, the arrangement of the error diffusion circuit 201, the dither circuit 202, the dither switching circuit 203, and the dither switching determination circuit 204 can be switched. In other words, in the fourth embodiment, the error diffusion circuit 201 provided immediately after the gain control circuit 200 in FIG. 3 is provided after the dither switching circuit 203.

  FIG. 20 is a block diagram showing an example of the multi-gradation signal processing circuit 3 as the fifth embodiment of the image display apparatus according to the present invention. In FIG. 20, reference numeral 10 is a sub-path, 21 is a main path, 22 is a spreading path, 31 is a path switch circuit, 40 is an SF encoding circuit, and 50 is a motion amount detection circuit.

  As is clear from the comparison between FIG. 20 and FIG. 13 described above, the multi-gradation signal processing circuit 3 of the fifth embodiment includes the sub-path 10, the main path 21, and the diffusion path 22 for each primary color. The output of either the main path 21 or the spreading path 22 is selected by the path switch circuit 31 and supplied to the SF encoding circuit 40. Here, the sub path 10 is for displaying an input image signal at a predetermined gradation level (for example, a gradation level lower than the gradation level of the input image signal), and the main path 21 is an input. The image signal can be displayed at the actual display gradation level.

  The subpath 10 has the same configuration as the subpath 10 shown in FIG. 13, and outputs a signal SP. The main path 21 receives the input image signal, outputs the signal MPG to the diffusion path 22, and outputs the signal MPL to the path switch circuit 31. The motion detection circuit 50 is also configured similarly to the motion detection circuit 50 shown in FIG. 13, and outputs a motion amount MV.

  The diffusion path 22 receives the output signal MPG of the main path 21 and the output signal (motion amount) MV of the motion detection circuit 50, and outputs a signal MPD that has been subjected to diffusion processing according to the motion amount MV. The path switch circuit 31 selects any one of the output signal SP of the sub path 10, the output signal MPL of the main path 21, or the output signal MPD of the diffusion path 22 according to the motion amount MV detected by the motion amount detection circuit 50, and SF The signal PSO is output to the encoding circuit 40. Note that the SF encoding circuit 40 has the same configuration as the SF encoding circuit 40 shown in FIG.

FIG. 21 is a block diagram showing an example of the main path 21 in the multi-gradation signal processing circuit shown in FIG.
As is clear from FIG. 21, the main path 21 includes a gain control circuit 200 and an error diffusion circuit 201. The output signal MPG of the gain control circuit 200 is supplied to the diffusion path 22, and the output signal MPL of the error diffusion circuit 201 is This is supplied to the path switch circuit 31.

FIG. 22 is a block diagram showing an example of the path switch circuit 31 in the multi-gradation signal processing circuit shown in FIG.
As shown in FIG. 22, the path switch circuit 31 includes a level detection circuit 300, a path switching determination circuit 303, and a path switching circuit 304. Level detection circuit 300 has the same function as level detection circuit 300 shown in FIG. 13 and outputs level amount LV to path switching determination circuit 303 based on output signal MPL of error diffusion circuit 201. The path switching determination circuit 303 outputs a control signal PSW for switching the path by the path switching circuit 304 based on the level amount LV from the level detection circuit 300 and the motion amount MV from the motion amount detection circuit 50. Then, the path switching circuit 304 selects one of the input output signal SP of the sub path 10, the output signal MPL of the main path 21, or the output signal MPD of the diffusion path 22 in accordance with the output signal PSW of the path switching determination circuit 303. And output as a signal PSO to the SF encoding circuit 40.

  That is, the values of the output signal PSW of the path switching determination circuit 303 are “0”, “1”, and “2”, and the path switching circuit 304 outputs the output signal of the main path 21 when the value of PSW is “0”. When MPL is selected, the output signal MPD of the diffusion path 22 is selected when the value of PSW is “1”, and the output signal SP of the sub path 10 is selected when the value of PSW is “2”.

FIG. 23 is a block diagram showing an example of the diffusion path 22 in the multi-gradation signal processing circuit shown in FIG.
As shown in FIG. 23, the diffusion path 22 includes an error diffusion circuit 201 and a motion adaptive dither circuit 205. Here, the error diffusion circuit 201 has the same function as the error diffusion circuit 201 in the main path 21 described above. The motion adaptive dither circuit 205 calculates the dither amount DL based on the motion amount MV that is the output of the motion detection circuit 50, and performs addition / subtraction processing on the dither amount DL with respect to the output of the error diffusion circuit 201 to output a signal MPD. The motion adaptive dither circuit 205 can also be configured as the dither circuit 202 described above (see, for example, FIG. 3 or FIG. 19).

  FIG. 24 is a flowchart showing an example of processing in the multi-gradation signal processing circuit as the fifth embodiment of the image display apparatus according to the present invention shown in FIG. Here, as the dither coefficient DK, any of the dither coefficients shown in FIGS. 10A to 10C or FIG. 5 may be applied, and the relationship between the motion amount MV and the calculated motion amount MVC. Any one of FIG. 12A to FIG. 12D may be applied.

  First, when the process is started in step 240, the process proceeds to step 241 to perform initialization, the dither amount calculation circuit (58) sets the dither amount DL = 0, and the path switching determination circuit 303 determines that the determination signal PSW is “0”. “0” is output. Next, proceeding to step 242, the dither circuit 53 performs addition / subtraction of the dither amount DL, and the path switching circuit 304 selects the output signal MPL of the main path 21.

  In step 243, the motion amount detection circuit 50 detects the motion amount MV, and in step 244, the level detection circuit 300 detects the level amount LV, and proceeds to step 245 to determine whether or not the level amount LV is zero. To do.

  If it is determined in step 245 that the level amount LV is zero, the process proceeds to step 24C. In step 245, it is determined that the level amount LV is not zero. In step 246, it is determined that pMV + qLV is not SPsel or higher. Further, in step 249, it is determined that pMV + qLV is not SPsel2 or higher (pMV + qLV <SPsel2 < SPsel), proceed to step 24C. Here, p and q in step 246 are coefficients for balancing the movement amount MV and the level amount LV, and SPsel and SPsel2 are determination thresholds. Note that there is a relationship of SPsel> SPsel2 between the determination threshold values SPsel and SPsel2.

  Specifically, for example, when the motion amount MV is a value of 0 to 15 and the level amount is a value of 0 to 5 as in the conversion data shown in FIG. 5, p = 1 and q = 3. Then, the maximum values that can be taken by pMV and qLV are the same, and the path switching determination circuit 303 has the same balance between the calculation of the motion amount and the level amount. If p = 1 and q = 2, the value that can be taken by pMV is larger than the value that can be taken by qLV. Therefore, the path switching determination circuit 303 makes a determination with priority given to the amount of motion.

  In step 24C, the dither amount DL is set to 0, and the path switching determination circuit 303 outputs a determination signal PSW of “0”. Further, the process proceeds to step 24D, where the dither amount DL is added and subtracted. The switching circuit 304 selects the output signal MPL of the main path 21 and returns to step 243.

  If it is determined in step 245 that the level amount LV is not zero and it is determined in step 246 that pMV + qLV is equal to or greater than SPsel (SPsel ≦ pMV + qLV), the process proceeds to step 247. Here, the fact that pMV + qLV is equal to or greater than SPsel (SPsel ≦ pMV + qLV: pMV + qLV is large) indicates a gradation in which the amount of motion MV is large and a false contour is likely to appear. When the amount of movement MV is large and the gray level is likely to generate a false contour, the process proceeds to step 247 where the dither amount DL is calculated and the path switching determination circuit 303 outputs the determination signal PSW of “2”. In step 248, the dither amount DL is added or subtracted. At the same time, the path switching circuit 304 selects the output signal SP of the sub path 10, and the process returns to step 243. When the output signal SP of the subpath 10 is selected as in step 248, the dither amount DL is not affected even after all.

  Further, if it is determined in step 245 that the level amount LV is not zero and if it is determined in step 246 that pMV + qLV is not equal to or greater than SPsel, the process proceeds to step 249. In step 249, it is determined that pMV + qLV is equal to or greater than SPsel2. Then (SPsel2 ≦ pMV + qLV <SPsel), the process proceeds to step 24A. In step 24A, the dither amount DL is calculated, and the path switching determination circuit 303 outputs a determination signal PSW of “1”. Further, the process proceeds to step 24B, where the dither amount DL is added and subtracted, and the path switching circuit. 304 selects the output signal MPD of the diffusion path (dither processing path) 22 and returns to step 243.

  In the above description, the determination of the level amount 0 in step 245 is meaningless even when switching to a sub-pass or dither processing pass in the case of a gradation that does not produce a false contour no matter how large the amount of motion is (when there is little motion). (When switching to a sub-pass with a small number of gradations, grain noise increases, or switching to the dither processing pass causes a dither pattern to be noticeable or deteriorates image quality). The path is not selected. As described above, in the fifth embodiment, the dither amount DL is determined based on the motion amount MV, and the main path, sub path, or dither processing path (diffusion path) is switched based on the motion amount MV and the level amount LV. It is like that.

  As described with reference to FIGS. 20 to 24, the image display apparatus according to the fifth embodiment performs level detection based on the output signal MPL of the error diffusion circuit. The image display apparatus of the third embodiment shown in FIGS. 13 to 18 described above performs level detection based on the output signal MP that has been subjected to error diffusion processing and further dithered, and level detection is performed by the dither amount DL to be added or subtracted. Although different, both can improve the image quality of moving image display by scattering false contours to surrounding pixels.

FIG. 25 is a block diagram showing a modification of the diffusion path in the multi-gradation signal processing circuit shown in FIG.
As is clear from a comparison between FIG. 25 and FIG. 21, the diffusion path 22 of this modification includes a dither circuit 202 and an error diffusion circuit 201, and performs error diffusion after the dither processing. Here, it is needless to say that the dither circuit 202 may be configured as, for example, the motion adaptive dither circuit 205 shown in FIG.

  By the way, since the false contour is weaker in the periphery and is less noticeable than the false contour generated in one place, the sub-pass 10 is inserted every other pixel in the main path 20 (21). By doing so, the false contour is generated widely, but since it is weakly generated, it is not recognized as a false contour.

  Specifically, for example, in an image display device having a screen size of 42 inches with a horizontal pixel count of 1024 dots, a false contour starts to be recognized when moving about 4 dots per field in the horizontal direction from experience, As the moving speed increases, false contours are also strongly recognized. That is, in the case of an image moving slowly, false contours are rarely recognized, and even if recognized, they are weak. In this case, the insertion of the sub-path in the path switching method has a small number of gradations, so the granular noise of the sub-path is conspicuous, and even when the dither coefficient by the dither method is increased, hatched noise due to the dither is conspicuous. For this reason, in the case of an image moving slowly, it is preferable to control so as not to select a subpath by reducing the dither coefficient by the dither method.

  On the other hand, in the case of fast moving images, the granular noise will not be noticeable even if the ratio (frequency) of selecting the sub-path is increased by the path switching method, but the false contour is recognized more than the false contour reduction capability by the path switching method. As a result, the false contour reduction effect is weakened. Similarly, the effect of reducing the false contour by the dither method is limited even if the dither coefficient is increased. For fast moving images, combining the dither method and the path switching method improves the false contour reduction capability. Therefore, it is preferable. Therefore, it is preferable to gradually change the dither coefficient of the dither method and the ratio of inserting the sub-path of the path switching method according to the moving speed.

  Of course, the present invention can also be realized for the three primary colors of RGB if there is a circuit for each primary color signal. The application of the present invention is not limited to the plasma display device. Furthermore, the weight of the subfield in the present invention may be a data weight, but may be a luminance weight.

(Appendix 1)
An image display device that divides one field into a plurality of weighted subfields and combines the plurality of subfields to perform multi-gradation display on a display panel,
A motion amount detection circuit for detecting a motion amount from an input image signal from a current field and a field before the current field;
Based on the gradation of the input image signal and the detected amount of motion, a diffusion amount calculation circuit that calculates a diffusion amount for diffusing false contour noise to the periphery,
An image display apparatus comprising: a diffusion circuit that performs a diffusion process with a diffusion amount calculated by the diffusion amount calculation circuit.

(Appendix 2)
The image display device according to attachment 1, further comprising a motion amount fixing circuit that fixes the motion amount to a predetermined value when the detected motion amount is equal to or greater than a predetermined threshold, and the diffusion amount calculation circuit includes: An image display device, wherein the diffusion amount is calculated based on the fixed amount of motion and the gradation of the input image signal.

(Appendix 3)
The image display device according to appendix 2, wherein the predetermined value for fixing the amount of movement is larger than the predetermined threshold value.

(Appendix 4)
The image display device according to attachment 1, wherein the diffusion amount calculation circuit calculates the diffusion amount from a predetermined proportional coefficient of the motion amount and a diffusion coefficient based on a gradation of the input image signal. Image display device.

(Appendix 5)
In the image display device according to attachment 1, when the amount of motion is equal to or greater than a predetermined threshold, the diffusion amount calculation circuit uses a predetermined proportional coefficient of the motion amount and a diffusion coefficient based on the gradation of the input image signal. An image display device that calculates the diffusion amount and sets the diffusion amount to zero when the movement amount is smaller than the predetermined threshold.

(Appendix 6)
In the image display device according to attachment 1, when the amount of movement is equal to or greater than a predetermined threshold,
The motion amount is MV, the predetermined threshold is TD, the predetermined proportionality coefficient of the motion amount is m, {MV−TD} × m, and the diffusion coefficient based on the gradation of the input image signal An image display device that calculates a diffusion amount.

(Appendix 7)
The image display device according to any one of appendices 4 to 6, wherein the diffusion coefficient is constant for all gradations.

(Appendix 8)
The image display device according to any one of appendices 4 to 6, wherein the diffusion coefficient is proportional to the gradation of the input image signal.

(Appendix 9)
The image display device according to any one of appendices 4 to 6, wherein the diffusion coefficient has a logarithmic relationship with the gradation of the input image signal.

(Appendix 10)
The image display device according to any one of appendices 4 to 6, wherein the diffusion coefficient is before a carry.

(Appendix 11)
The image display apparatus according to appendix 1, wherein the diffusion circuit performs a diffusion process only on a specific gradation of the input image signal.

(Appendix 12)
The image display device according to appendix 1, wherein the diffusion circuit is a circuit that performs dither diffusion.

(Appendix 13)
An image display device that divides one field into a plurality of weighted subfields and combines the plurality of subfields to perform multi-gradation display on a display panel,
A main path for generating a signal having a predetermined number of gradations from the input image signal;
A sub-pass that generates a signal having a smaller number of gradations than the main pass;
A path switch circuit that switches and outputs either the main path generation signal or the sub path generation signal;
A motion amount detection circuit for detecting a region moving between a current field and a field before the current field from the input image signal, and outputting a motion amount that is a moving amount;
A level detection circuit for detecting a level amount of false contour strength when a moving image false contour occurs in the main path;
A sub-path determination circuit that compares the detected amount of motion and the detected level amount with a predetermined set value, and determines a gradation in a moving image region and a strong false contour generation intensity;
A sub path switch that switches the path switch circuit from the output of the main path to the output of the sub path according to a determination result of the sub path determination circuit;
A diffusion coefficient generation circuit that generates a diffusion coefficient depending on the gradation of the input image signal for calculating a diffusion amount for diffusing false contour noise to the periphery;
A diffusion amount calculation circuit for calculating a diffusion amount based on the movement amount and the diffusion coefficient;
An image display apparatus comprising: a diffusion circuit that performs a diffusion process with a diffusion amount calculated by the diffusion amount calculation circuit; and controlling the subpath switch and the diffusion amount to reduce false contours.

(Appendix 14)
The image display device according to attachment 13, further comprising: a motion amount fixing circuit that fixes the motion amount to a predetermined value when the detected motion amount is equal to or greater than a predetermined threshold; An image display device, wherein the diffusion amount is calculated based on the fixed motion amount and a diffusion coefficient depending on the gradation.

(Appendix 15)
The image display device according to appendix 14, wherein the predetermined value for fixing the amount of movement is larger than the predetermined threshold value.

(Appendix 16)
The image display device according to appendix 13, wherein the diffusion amount calculation circuit calculates the diffusion amount based on a predetermined proportional coefficient of the motion amount and a diffusion coefficient depending on a gradation of the input image signal. An image display device.

(Appendix 17)
In the image display device according to attachment 13, when the movement amount is equal to or greater than a predetermined threshold, the diffusion amount calculation circuit calculates a predetermined proportionality coefficient of the movement amount and a diffusion coefficient based on the gradation of the input image signal. An image display device that calculates the diffusion amount and sets the diffusion amount to zero when the movement amount is smaller than the predetermined threshold.

(Appendix 18)
In the image display device according to attachment 13, when the amount of movement is greater than or equal to a predetermined threshold,
The amount of motion is MV, the predetermined threshold is TD, the predetermined proportional coefficient of the amount of motion is m, and {MV-TD} × m and the diffusion from the diffusion coefficient based on the gradation of the input image signal An image display device characterized by calculating an amount.

(Appendix 19)
The image display device according to appendix 13, wherein the diffusion coefficient is constant for all gradations.

(Appendix 20)
The image display device according to appendix 13, wherein the diffusion coefficient is proportional to the gradation of the input image signal.

(Appendix 21)
The image display device according to appendix 13, wherein the diffusion coefficient has a logarithmic relationship with the gradation of the input image signal.

(Appendix 22)
The image display device according to appendix 13, wherein the diffusion coefficient is before a carry.

(Appendix 23)
The image display device according to appendix 13, wherein the diffusion circuit performs a diffusion process only on a specific gradation of the input image signal.

(Appendix 24)
The image display device according to appendix 13, wherein the diffusion circuit is a circuit that performs dither diffusion.

(Appendix 25)
The image display device according to appendix 13, wherein the level amount is set after a carry.

(Appendix 26)
The image display device according to attachment 13, wherein the sub-path determination circuit is configured such that the sum of the product of the motion amount and the first value and the product of the level amount and the second value is equal to or greater than a third value. An image display device that switches from a main path to the sub path.

(Appendix 27)
In the image display device according to attachment 13, the sub-path determination circuit has a sum of a product of the motion amount and the first value and a product of the level amount and the second value equal to or greater than a third value, and When the level amount is other than zero, switching from the main path to the sub path is performed.

(Appendix 28)
An image display device that divides one field into a plurality of weighted subfields and combines the plurality of subfields to perform multi-gradation display on a display panel,
A main path for generating a signal having a predetermined number of gradations from the input image signal;
A sub-pass that generates a signal having a smaller number of gradations than the main pass;
A diffusion processing path for generating a signal obtained by performing diffusion processing on the input image signal;
A path switch circuit that switches and outputs any one of the main path generation signal, the sub path generation signal, and the diffusion processing path generation signal;
A motion detection circuit that detects a moving area between the current field and a field before the current field from the input image signal, and outputs a movement amount that is a moving amount;
A level detection circuit for detecting a level amount of false contour strength when a moving image false contour occurs in the main path;
A path switching determination circuit that compares the detected amount of motion and the detected level amount with a predetermined set value, and determines a gradation with a strong false contour generation intensity in a moving image area;
A path switching circuit that switches the path switch circuit to any one of the output of the main path, the output of the sub path, or the diffusion processing path according to the determination result of the sub path determination circuit;
A diffusion coefficient generation circuit for generating a diffusion coefficient depending on the gradation of the input image signal for calculating a diffusion amount for diffusing false contour noise to the periphery;
A diffusion amount calculation circuit for calculating a diffusion amount based on the movement amount and the diffusion coefficient;
An image display apparatus comprising: a diffusion circuit that performs a diffusion process with a diffusion amount calculated by the diffusion amount calculation circuit; and controlling the path switching circuit and the diffusion amount to reduce false contours.

(Appendix 29)
The image display device according to attachment 28, wherein the path switching determination circuit includes a first setting value and a second setting value smaller than the first setting value, and the diffusion calculated by the diffusion amount calculation circuit If the amount is greater than or equal to the first set value, select the sub-path, if less than the first set value and greater than or equal to the second set value, select the diffusion processing path; and The image display device is characterized in that the main path is selected when it is smaller than the second set value.

(Appendix 30)
29. The image display device according to appendix 28, wherein the diffusion circuit is dither.

(Appendix 31)
A driving method of an image display device that divides one field into a plurality of weighted subfields and combines the plurality of subfields to perform multi-gradation display on a display panel,
A motion amount detection step of detecting a motion amount from a current field and a field before the current field from an input image signal;
A diffusion amount calculating step of calculating a diffusion amount for diffusing false contour noise to the periphery based on the gradation of the input image signal and the detected amount of motion;
A driving method for an image display device, comprising: a diffusion stage that performs a diffusion process according to the calculated diffusion amount.

(Appendix 32)
The driving method of the image display device according to attachment 31, further comprising: a movement amount fixing step of fixing the movement amount to a predetermined value when the detected movement amount is equal to or greater than a predetermined threshold value; The step of calculating the amount of diffusion based on the fixed amount of motion and the gradation of the input image signal.

(Appendix 33)
The image display device driving method according to attachment 32, wherein the predetermined value for fixing the amount of movement is larger than the predetermined threshold value.

(Appendix 34)
The driving method of the image display device according to attachment 31, wherein the diffusion amount calculating step calculates the diffusion amount from a predetermined proportional coefficient of the motion amount and a diffusion coefficient based on a gradation of the input image signal. A method for driving an image display device.

(Appendix 35)
The driving method of the image display device according to attachment 31, wherein the diffusion amount calculation step is based on a predetermined proportional coefficient of the motion amount and a gradation of the input image signal when the motion amount is equal to or greater than a predetermined threshold. A driving method of an image display device, wherein the diffusion amount is calculated from a diffusion coefficient, and the diffusion amount is set to zero when the motion amount is smaller than the predetermined threshold.

(Appendix 36)
In the driving method of the image display device according to attachment 31, when the amount of movement is greater than or equal to a predetermined threshold,
The amount of motion is MV, the predetermined threshold is TD, the predetermined proportional coefficient of the amount of motion is m, and {MV-TD} × m and the diffusion from the diffusion coefficient based on the gradation of the input image signal A method for driving an image display device, comprising calculating an amount.

(Appendix 37)
37. The driving method for an image display device according to any one of appendices 34 to 36, wherein the diffusion coefficient is constant for all gradations.

(Appendix 38)
37. A driving method of an image display device according to any one of appendices 34 to 36, wherein the diffusion coefficient is proportional to the gradation of the input image signal.

(Appendix 39)
37. The driving method for an image display device according to any one of appendices 34 to 36, wherein the diffusion coefficient has a logarithmic relationship with the gradation of the input image signal.

(Appendix 40)
37. A driving method of an image display device according to any one of appendices 34 to 36, wherein the diffusion coefficient is before carry.

(Appendix 41)
32. The driving method of an image display device according to claim 31, wherein the diffusion step performs diffusion processing only on a specific gradation of the input image signal.

(Appendix 42)
32. The driving method of an image display device according to appendix 31, wherein the diffusion step performs dither diffusion.

(Appendix 43)
A main path for dividing one field into a plurality of weighted subfields, combining the plurality of subfields to perform multi-grayscale display on a display panel, and generating a signal with a predetermined number of grayscales from an input image signal; A driving method for an image display device, comprising: a sub-path that generates a signal having a smaller number of gradations than the main path; and a path switching stage that switches and outputs either the main-path generation signal or the sub-path generation signal. There,
A motion amount detecting step of detecting a region moving between the current field and a field before the current field from the input image signal, and outputting a motion amount that is a moving amount;
A level detection step of detecting a level amount of false contour strength when a video false contour occurs in the main path;
A sub-pass determination step for comparing the detected amount of motion with the predetermined level based on the detected level amount, and determining a gradation with a strong false contour occurrence intensity in the moving image region;
A subpath switching stage that switches the path switching stage from the output of the main path to the output of the subpath according to the determination result of the subpath judgment stage;
A diffusion coefficient generation step for generating a diffusion coefficient depending on the gradation of the input image signal for calculating a diffusion amount for diffusing false contour noise to the periphery;
A diffusion amount calculation step of calculating a diffusion amount based on the movement amount and the diffusion coefficient;
And a diffusion step of performing diffusion processing according to the diffusion amount, and controlling the subpath switch and the diffusion amount to reduce false contours.

(Appendix 44)
The driving method of the image display device according to attachment 43, further comprising: a movement amount fixing step of fixing the movement amount to a predetermined value when the detected movement amount is equal to or greater than a predetermined threshold value; The step of calculating the amount of diffusion based on the fixed amount of motion and the diffusion coefficient depending on the gradation.

(Appendix 45)
45. The driving method of the image display device according to claim 44, wherein the predetermined value for fixing the amount of movement is larger than the predetermined threshold value.

(Appendix 46)
44. The driving method of the image display device according to attachment 43, wherein the diffusion amount calculation step calculates the diffusion amount based on a predetermined proportional coefficient of the motion amount and a diffusion coefficient depending on a gradation of the input image signal. An image display device driving method characterized by the above.

(Appendix 47)
The driving method of the image display device according to attachment 43, wherein the diffusion amount calculation step is based on a predetermined proportional coefficient of the movement amount and a gradation of the input image signal when the movement amount is equal to or greater than a predetermined threshold. A driving method of an image display device, wherein the diffusion amount is calculated from a diffusion coefficient, and the diffusion amount is set to zero when the motion amount is smaller than the predetermined threshold.

(Appendix 48)
In the driving method of the image display device according to attachment 43, when the amount of movement is equal to or greater than a predetermined threshold,
The amount of motion is MV, the predetermined threshold is TD, the predetermined proportional coefficient of the amount of motion is m, and {MV-TD} × m and the diffusion from the diffusion coefficient based on the gradation of the input image signal A method for driving an image display device, comprising calculating an amount.

(Appendix 49)
44. A driving method of an image display device according to appendix 43, wherein the diffusion coefficient is constant for all gradations.

(Appendix 50)
44. The driving method of an image display device according to claim 43, wherein the diffusion coefficient is proportional to the gradation of the input image signal.

(Appendix 51)
44. The driving method for an image display device according to claim 43, wherein the diffusion coefficient has a logarithmic relationship with the gradation of the input image signal.

(Appendix 52)
44. The driving method of an image display device according to claim 43, wherein the diffusion coefficient is before carry.

(Appendix 53)
44. The driving method for an image display device according to claim 43, wherein the diffusion step performs diffusion processing only on a specific gradation of the input image signal.

(Appendix 54)
44. The driving method of an image display device according to claim 43, wherein the diffusion step performs dither diffusion.

(Appendix 55)
44. The driving method for an image display device according to claim 43, wherein the level amount is set after a carry.

(Appendix 56)
In the driving method of the image display device according to attachment 43, in the sub-pass determination step, a sum of the product of the motion amount and the first value and the product of the level amount and the second value is equal to or greater than a third value. In this case, the image display device driving method is characterized in that the main path is switched to the sub path.

(Appendix 57)
In the driving method of the image display device according to attachment 43, in the sub-pass determination step, the sum of the product of the motion amount and the first value and the product of the level amount and the second value is equal to or greater than a third value. When the level amount is other than zero, the main path is switched to the sub path, and the driving method of the image display device is characterized in that:

(Appendix 58)
A main path for dividing one field into a plurality of weighted subfields, combining the plurality of subfields to perform multi-grayscale display on a display panel, and generating a signal with a predetermined number of grayscales from an input image signal; A sub path for generating a signal having a smaller number of gradations than the main path, a diffusion processing path for generating a signal obtained by performing a diffusion process on the input image signal, a generation signal for the main path, a generation signal for the sub path, or A method of driving an image display device comprising a path switching step of switching and outputting any one of the generation signals of the diffusion processing path,
Detecting a region moving between the current field and a field before the current field from the input image signal, and outputting a movement amount that is a movement amount; and
A level detection step of detecting a level amount of false contour strength when a video false contour occurs in the main path;
A path switching determination step that compares the detected amount of motion with a predetermined set value based on the detected level amount, and determines a gradation with a strong false contour generation intensity in the moving image region,
A path switching stage that switches the path switching stage to any one of the output of the main path, the output of the subpath, or the diffusion processing path according to the determination result of the subpath determination stage;
A diffusion coefficient generation step for generating a diffusion coefficient depending on the gradation of the input image signal for calculating a diffusion amount for diffusing false contour noise to the periphery;
A diffusion amount calculation step of calculating a diffusion amount based on the movement amount and the diffusion coefficient;
A method for driving an image display device, comprising: a diffusion step of performing diffusion processing with a diffusion amount calculated in the diffusion amount calculation step; and controlling the path switching step and the diffusion amount to reduce false contours .

(Appendix 59)
59. The driving method of an image display device according to attachment 58, wherein the path switching determination step includes a first setting value and a second setting value smaller than the first setting value, and is calculated by the diffusion amount calculation step. The sub-path is selected when the spread amount is greater than or equal to the first set value, and the spread processing path is selected when the spread amount is smaller than the first set value and greater than or equal to the second set value. And a method of driving the image display device, wherein the main path is selected when the value is smaller than the second set value.

(Appendix 60)
59. A driving method of an image display device according to claim 58, wherein the diffusion step is dithering.

  The present invention can be widely applied to an image display device such as a plasma display device. For example, a display device such as a personal computer or a workstation, a flat wall-mounted television, or an advertisement or information is displayed. The present invention can be applied to an image display device used as a device for this purpose.

It is a block diagram which shows roughly an example of the image display apparatus with which this invention is applied. 1 is a block diagram showing an example of a multi-gradation signal processing circuit as a first embodiment of an image display apparatus according to the present invention. FIG. 3 is a block diagram showing an example of a path (main path) in the multi-gradation signal processing circuit shown in FIG. 2. FIG. 3 is a block diagram showing an example of a motion amount detection circuit in the multi-gradation signal processing circuit shown in FIG. 2. It is a figure which shows an example of the SF conversion data memorize | stored in the SF encoding circuit in the multi-gradation signal processing circuit shown in FIG. It is a figure which shows an example of the drive sequence of the drive control circuit in the image display apparatus which concerns on this invention. It is a block diagram which shows the other example of the path | pass (main path) in the multi-gradation signal processing circuit as 2nd Example of the image display apparatus based on this invention. FIG. 8 is a block diagram illustrating an example of a motion adaptive dither circuit in the path of the multi-gradation signal processing circuit illustrated in FIG. 7. FIG. 9 is a diagram for describing dither calculation within one field performed by a dither amount calculation circuit in the motion adaptive dither circuit shown in FIG. 8. It is a figure for demonstrating the relationship between the gradation and the dither coefficient in the drive method of the image display apparatus which concerns on this invention. FIG. 8 is a block diagram showing another example of the motion adaptive dither circuit in the path of the multi-gradation signal processing circuit shown in FIG. 7. It is a figure which shows the relationship between the amount of motion of the input image signal in the image display apparatus which concerns on this invention, and the amount of calculation motion. It is a block diagram which shows an example of the multi-gradation signal processing circuit as 3rd Example of the image display apparatus which concerns on this invention. It is a block diagram which shows an example of the sub path | pass in the multi-gradation signal processing circuit shown in FIG. FIG. 14 is a block diagram illustrating an example of a path switch circuit in the multi-gradation signal processing circuit illustrated in FIG. 13. 4 is a flowchart showing an example of a path (main path) process in the multi-gradation signal processing circuit as the first embodiment of the image display apparatus according to the present invention shown in FIG. 3; It is a flowchart which shows an example of the process of the path | pass (main path) in the multi-gradation signal processing circuit as 2nd Example of the image display apparatus based on this invention shown in FIG. It is a flowchart which shows an example of the process in the multi-gradation signal processing circuit as 3rd Example of the image display apparatus based on this invention shown in FIG. It is a block diagram which shows the further another example of the path | pass (main path) in the multi-gradation signal processing circuit as 4th Example of the image display apparatus which concerns on this invention. It is a block diagram which shows an example of the multi-gradation signal processing circuit as 5th Example of the image display apparatus based on this invention. FIG. 21 is a block diagram illustrating an example of a main path in the multi-gradation signal processing circuit illustrated in FIG. 20. FIG. 21 is a block diagram illustrating an example of a path switch circuit in the multi-gradation signal processing circuit illustrated in FIG. 20. FIG. 21 is a block diagram illustrating an example of a diffusion path in the multi-gradation signal processing circuit illustrated in FIG. 20. FIG. 21 is a flowchart showing an example of processing in the multi-gradation signal processing circuit as the fifth embodiment of the image display apparatus according to the present invention shown in FIG. 20; FIG. FIG. 21 is a block diagram showing a modification of the diffusion path in the multi-gradation signal processing circuit shown in FIG. 20.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Video signal input terminal 2 Synchronization signal input terminal 3 Multi-gradation signal processing circuit 4 Field memory 5 Drive control circuit 6 Timing generation circuit 7 Display panel 10 Subpath (main path)
20, 21 pass (main pass)
22 diffusion path 30, 31 path switch circuit 40 SF encoding circuit 50 motion amount detection circuit 51 dither coefficient generation circuit 52, 58 dither amount calculation circuit 53, 202 dither circuit 54-1 to 54-n dither gradation setting circuit 55- 1 to 55-n dither coefficient setting circuit 56-1 to 56-n dither gradation comparison circuit 57 dither coefficient selection circuit 100 distortion correction circuit 101 gain control circuit 102 error diffusion circuit 103 data matching circuit 200 gain control circuit 201 error diffusion circuit 203 Dither switching circuit 204 Dither switching determination circuit 205 Motion adaptive dither circuit 300 Level detection circuit 301 Subpath determination circuit 302 Subpath switch 500 RGB matrix circuit 501 Edge detection circuit 502 Motion region detection circuit 503 Motion amount determination circuit 531 Addition of dither amount Arithmetic circuit 532 Dither amount subtraction circuit 533 Horizontal counter 534 Vertical counter 535 Addition / subtraction selection circuit

Claims (2)

An image display device that divides one field into a plurality of weighted subfields and combines the plurality of subfields to perform multi-gradation display on a display panel,
A main path for generating a signal having a predetermined number of gradations from the input image signal;
A sub-pass that generates a signal having a smaller number of gradations than the main pass;
A diffusion processing path for generating a signal obtained by performing diffusion processing on the input image signal;
A path switch circuit that switches and outputs any one of the main path generation signal, the sub path generation signal, and the diffusion processing path generation signal;
A motion detection circuit for detecting a region moving between a current field and a field before the current field from the input image signal, and outputting a motion amount MV that is a moving amount;
A level detection circuit that detects a level amount LV of the strength of the false contour when a moving image false contour occurs in the main path ,
The diffusion processing path is:
A diffusion coefficient generation circuit for generating a diffusion coefficient depending on the gradation of the input image signal for calculating a diffusion amount for diffusing false contour noise to the periphery;
A diffusion amount calculation circuit for calculating a diffusion amount based on the movement amount MV and the diffusion coefficient;
A diffusion circuit that performs diffusion processing with the diffusion amount calculated by the diffusion amount arithmetic circuit,
In the path switch circuit, when the level amount LV is 0 and a value N = pMV + qLV (where p and q are coefficients) depending on the level amount LV and the motion amount MV is equal to or less than a first predetermined value, When a main path is selected and the value N is greater than the first predetermined value and less than or equal to a second predetermined value, the diffusion processing path is selected, and when the value N is greater than the second predetermined value The image display device is characterized in that the sub-path is selected . A main path for dividing one field into a plurality of weighted subfields, combining the plurality of subfields to perform multi-grayscale display on a display panel, and generating a signal with a predetermined number of grayscales from an input image signal; A sub path for generating a signal having a smaller number of gradations than the main path, a diffusion processing path for generating a signal obtained by performing a diffusion process on the input image signal, a generation signal for the main path, a generation signal for the sub path, or A method of driving an image display device comprising a path switching step of switching and outputting any one of the generation signals of the diffusion processing path,
A motion detection step of detecting a region moving between the current field and a field before the current field from the input image signal, and outputting a motion amount MV that is a moving amount;
A level detection step of detecting a level amount LV of the strength of a false contour when a moving image false contour occurs in the main path ,
The diffusion processing path is:
A diffusion coefficient generation step for generating a diffusion coefficient depending on the gradation of the input image signal for calculating a diffusion amount for diffusing false contour noise to the periphery;
A diffusion amount calculation step of calculating a diffusion amount based on the movement amount MV and the diffusion coefficient;
A diffusion stage for performing diffusion processing with the diffusion amount calculated by the diffusion amount calculation stage,
In the path switching stage, the level amount LV is 0, and the value N = pMV + qLV (where p and q are coefficients) depending on the level amount LV and the motion amount MV is equal to or less than a first predetermined value. When a main path is selected and the value N is greater than the first predetermined value and less than or equal to a second predetermined value, the diffusion processing path is selected, and when the value N is greater than the second predetermined value A method for driving an image display device, wherein the sub-path is selected .

Images