JP2003069922A - Picture display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-gradation picture display device that can display improved gradation disturbance for medium tone display caused when a moving picture is displayed and display a picture where a switching shock is not remarkable. SOLUTION: A signal shown in Figure 17 (d) is used for a coding switching signal. Since the border of the signal has a random shape according to the signal and an area intermingled with different coding methods of a still picture coding method and a moving picture coding method is formed at the switching border part, changes in temporal features of light emission in a PDP (Plasma display panel) are not arranged attended with the selection of a different coding so as to make the selection of the different coding unremarkable thereby smoothly switching the still picture coded part and the moving picture coding part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device using a plasma display panel or the like, in which one TV field of an image is divided into images of a plurality of sub-fields and displayed to perform multi-gradation display. The present invention relates to an image display device capable of displaying an image with a wide dynamic range by enlarging the ratio of the maximum value and the minimum value of the brightness values that can be displayed.

Further, according to the present invention, in a display device for displaying one TV field of an image by dividing the image into a plurality of sub-field images and displaying them, a gray scale display which occurs when a moving image is displayed. The present invention relates to a multi-gradation image display device capable of improving disorder display.

[0003]

When a multi-gradation image is displayed using a display panel which is basically a binary display, as in the case where a plasma display panel or the like is used, one TV field of the image is divided into a plurality of images. A method is known in which an image is displayed by dividing it into subfields, giving each subfield a predetermined luminance weight, and controlling the presence or absence of light emission for each subfield.

For example, in order to display 256 gradations,
One TV field of the input image signal is divided into eight subfields, and the luminance weights of the respective subfields are “1”, “2”, “4”, “8”, “16”, “3”.
2 ”,“ 64 ”, and“ 128 ”. If the input image signal is an 8-bit digital signal, it is displayed by allocating it to eight sub-field images in order from the least significant bit. Note that each subfield image is a binary image.

On the other hand, in image display using a CRT, CR
T itself has a so-called inverse gamma characteristic, and even if the maximum luminance value is a value proportional to “255”,
The minimum luminance value is a value that is proportional to a decimal value of "1" or less, and the so-called dynamic range is a sufficient value of 255 or more. However, in the plasma display panel, the light emission characteristic is linear, and the gradation value is displayed by the sum of the light emission brightness almost proportional to the weight of the subfield. Therefore, the minimum brightness value is equal to "1", and the maximum brightness value is the maximum. The luminance value is a value corresponding to a total of "255" of the weights of the subfields, and the minimum luminance value is larger than that of the CRT, so that the image display has a so-called narrow dynamic range.

On the other hand, it is not easy to increase the displayable gradation value by increasing the number of subfields due to restrictions such as the discharge rate of the plasma display, and the maximum value of the number of subfields that can be normally set is limited. To be done. Further, it is known that the above-described method of displaying 256 gradations using eight subfields in the related art causes significant gradation irregularity in a so-called pseudo contour in moving image display.

Therefore, as one method of eliminating this gradation disturbance, an attempt has been made to detect the movement of the image and change the encoding for each pixel or each region. This is because, for example, the encoding method is changed for each area of the image, and 256 different gradation values are emitted for the input 256 gradations in the still image portion, and the gradation value is limited in the moving image portion. Is to emit light. By doing so, the encoding is performed so that the continuity of the change of the light emission pattern is secured to some extent with respect to the monotonous change of the gradation value of the input image signal in the moving image portion, and therefore, the significant moving image pseudo-motion in the moving image portion is achieved. It can be expected to reduce the contour. Moreover, the original sufficient gradation is secured in the still image portion.

However, with such a conventional method alone, since the coding is switched at the boundary between the moving image part and the still image part, a switching shock may be observed at this part depending on the image. In particular, this switching shock was sometimes seen near the boundary of an image in which an object moved with a flat portion as the background. The present invention is
This is made in view of the above-mentioned problems,
In a display device using a plasma display panel or the like that performs multi-gradation display by dividing a field portion into a plurality of sub-field images for display, the maximum and minimum luminance values that can be displayed in the same screen are displayed. A first object is to provide an image display device capable of displaying an image with a wide dynamic range by expanding the ratio.

It is another object of the present invention to provide a multi-gradation image display device capable of improving gradation display of halftone display which occurs at the time of displaying a moving image and displaying the image without noticeable switching shock. The purpose of.

[0010]

In order to achieve the first object, according to the present invention, one TV field is formed by arranging a plurality of subfields each having a luminance weight in time order, Turn on the subfield for 1T
An image display device for displaying an image of a V field in multiple gradations, characterized by including a subfield whose luminance weight is less than 1/2 of the luminance weight of a subfield having the next largest luminance weight. .

Further, one TV field is formed by arranging a plurality of subfields each having a luminance weight in time order, and a desired subfield is turned on to perform 1TV.
An image display device for displaying an image of a field in multi-gradation, wherein the subfields are arranged in ascending order of brightness weight, and when the brightness weight of the subfield having the i-th smallest brightness weight is W _i , W ₁ + W It is characterized in that the luminance weights are assigned so that there exists n in which ₁ + W ₂ + ... + W _n <W _{n + 1} .

With these, when all the selectable luminance value (gradation value) combinations are rearranged in the order of luminance value (gradation value), a portion in which the luminance (gradation) jumps can be generated, which causes The ratio between the minimum luminance value and the maximum luminance value that can be expressed can be made larger than in the conventional case, so that image display with a wide dynamic range can be realized.

Further, one TV field is formed by arranging a plurality of sub-fields each having a luminance weight in time order, and a desired sub-field is turned on to perform one TV.
An image display device for displaying an image of a field in multiple gradations, wherein the subfields are arranged in ascending order of brightness weight, and the brightness weight of the subfield having the jth smallest brightness weight is W _j , where W _i + W ₁ + W ₂ + ... + W _n <W _{n + 1} , and the brightness weights are assigned so that there exist n and i of 2 or more.

As a result, when all selectable luminance value (gradation value) combinations are rearranged in the order of luminance value (gradation value), a portion where the luminance (gradation) jumps can be generated. The ratio between the minimum luminance value and the maximum luminance value that can be expressed can be made larger than in the conventional case, so that image display with a wide dynamic range can be realized. Further, by this, the jump width of the brightness value can be controlled according to the gradation value of the input image signal. For example, the jump width of the brightness value is allowed as the brightness value is higher, and the maximum brightness value that can be displayed is further increased. It can be set large.

Further, according to the present invention, one TV field is formed by arranging a plurality of subfields each having a luminance weight in time order, and a desired subfield is turned on to display an image of one TV field in multiple gradations. In addition, in the image display device configured to control the maximum display brightness according to the characteristics of the input image signal, a TV field including a plurality of subfields configured by a combination of predetermined brightness weights is a reference TV field. And the luminance weights of all subfields in the coding pattern used to display the display TV field to be displayed at present with respect to the sum of the luminance weights of all subfields in the coding pattern used to display the reference TV field. When the ratio of the sum of the
The coding pattern used to display the fields is a subfield having a luminance weight calculated by multiplying the luminance weight of a predetermined subfield in the reference TV field by a coefficient of K or less, and a predetermined subfield in the reference TV field. Sub-field having a luminance weight calculated by multiplying the luminance weight of 1 by a coefficient exceeding K.

Thus, when the maximum displayable luminance value is controlled according to the maximum gradation value of the image or the distribution degree of the high gradation area, the minimum displayable luminance value is always kept small and displayable. The maximum brightness value can be controlled as needed. In general, in an image including a relatively bright portion, if the maximum luminance value that can be displayed is increased more than necessary, the power consumption as a whole will decrease in a display device such as a plasma display panel that has a high correlation between the emission luminance and the power consumption. Since it may increase, it is desirable to control the maximum displayable brightness value according to the content of the image. When such control is performed, even if the maximum displayable luminance value is increased, for example, a subfield having a small luminance weight is always kept a relatively small value, while a subfield having a relatively large luminance weight is kept. Since the brightness weight is changed according to the desired maximum displayable brightness value, the ratio between the minimum brightness value and the maximum brightness value can be made large, and even if the maximum brightness value is displayed large, the image The part close to the black level does not rise, and the sense of contrast is not impaired.

Here, the coefficient equal to or less than K and the coefficient exceeding K can be a coefficient set based on a rule defined by the order of the magnitude of the luminance weight of each subfield in the reference TV field. . Here, the coefficient set based on the rule defined by the order of the magnitude of the luminance weight can be a coefficient that monotonically increases according to the order of the magnitude of the luminance weight.

Here, the coefficient set based on the rule defined by the order of the magnitude of the luminance weight can be an equal coefficient according to the order of the magnitude of the luminance weight. Here, the coefficient set based on the rule defined by the order of the magnitude of the luminance weight may be a proportional coefficient according to the order of the magnitude of the luminance weight. Here, a subfield belonging to a subfield group calculated by multiplying by a coefficient equal to or less than K is a subfield fixed to a luminance weight obtained by multiplying a minimum value that can be set among a plurality of possible values among the values of K. Can be included.

Here, the approximate values of the ratios of the luminance weights of the three subfields selected in ascending order of the luminance weights of the subfields are "1: 2: 3", "1: 2: 4", and "1:".
"2: 5", "1: 2: 6", "1: 3: 7", "1:"
At least out of the coding patterns including any two or more of “4: 9”, “2: 6: 12”, and “2: 6: 16” and determined according to the characteristics of the desired input image signal. Two
The brightness weights of the sub-fields in one can be configured.

Here, when the sum of the luminance weights of all subfields is S, when gradation display corresponding to a value "R" of "0" or more and "S" or less is selected from each subfield, The gradations can be displayed by selecting a combination of subfields in which the sum of the brightness weights of the selected subfields is the sum of the brightness weights closest to the value “R”.

As a result, since the gradation value which cannot be expressed only by the combination of the single sub-fields can be corrected by the known gradation correction technique such as the error diffusion or the dither method, the minimum brightness value can be suppressed and expressed. An image with a wide dynamic range can be displayed well with smoothly corrected gradations while maintaining a large maximum brightness value.

Here, the combination of the brightness weights to be selected can be controlled by the amount of movement of the image or the approximate value of the movement of the image. As a result, the minimum luminance value can be kept small and the maximum luminance value can be kept large, so that an image with a wide dynamic range can be satisfactorily displayed with smoothly corrected gradations, and at the same time, in areas where the image moves. It is also possible to suppress the occurrence of the moving image pseudo contour.

The generation of the moving image pseudo contour is caused by the movement of the line of sight relative to the screen displayed by the observer, but the amount of movement of the image or an approximate value of the movement of the image may be used. A practically sufficient effect of suppressing the pseudo contour can be obtained.
Here, in a portion where the amount of motion of the image or the approximate value of the amount of motion of the image is large, the encoding is limited to the encoding in which the gradation level increase of the input image signal and the temporal distribution of the luminance weight arrangement pattern have a monotonically increasing correlation. Can be one.

Thus, the control of the subfield from the ON state to the OFF state is eliminated when the gradation value of the input image signal is increased, or the ON field is changed from the ON state when the gradation value of the input image signal is increased. Since the luminance weight of the subfield controlled to the off state can be made relatively small, it is possible to display an image in which the occurrence of the moving image pseudo contour is further effectively suppressed.

Further, in order to achieve the second object, according to the present invention, one TV field is configured by arranging a plurality of subfields each having a luminance weight in time order, and is expressed by combining the subfields. An image in which a desired image of one TV field is displayed in multiple gradations by using a combination of different brightness weights according to the amount of motion of the input image signal from among possible gradation values and performing different encoding according to the amount of motion. In the display device, at the time of the encoding, in a portion where an image signal at a switching boundary portion of the encoding method has a predetermined characteristic, the image signal is encoded so as to include an area in which a plurality of encoding methods are mixed. Is characterized by.

In order to achieve the second object, according to the present invention, one TV field is formed by arranging a plurality of subfields each having a luminance weight in time order, and the subfields are combined and expressed. By using a combination of different brightness weights according to the amount of motion of the input image signal from among possible gradation values, different encoding is performed according to the amount of motion to display a desired 1 TV field image in multiple gradations. In the image display device, at the time of the encoding, in a portion where an image signal at a switching boundary portion of the encoding method has a predetermined characteristic, the signal for switching the encoding method is irregularly shifted in the pixel direction. It is characterized by

Further, in order to achieve the second object, according to the present invention, one TV field is formed by arranging a plurality of subfields each having a luminance weight in time order, and the subfields are combined and expressed. By using a combination of different brightness weights according to the amount of motion of the input image signal from among possible gradation values, different encoding is performed according to the amount of motion to display a desired 1 TV field image in multiple gradations. In the image display device, at the time of the encoding, in the portion where the image signal at the switching boundary portion of the encoding method has a predetermined characteristic, the signal for switching the encoding method is regularly shifted in the pixel direction. It is characterized by having done.

In order to achieve the second object, according to the present invention, one TV field is configured by arranging a plurality of subfields each having a luminance weight in time order, and expressing the subfields in combination. By using a combination of different brightness weights according to the amount of motion of the input image signal from among possible gradation values, different encoding is performed according to the amount of motion to display a desired 1 TV field image in multiple gradations. In the image display device, at the time of the encoding, in a portion where the image signal at the switching boundary portion of the encoding method has a predetermined feature, the shape at the switching boundary portion of the signal for switching the encoding method is It is characterized in that it has a shape including a polygonal line having a pixel interval as a minimum unit as a main element.

As a result, even if a switching shock occurs in the image portion for which the encoding method has been switched, the positions where these are generated can be dispersed, so that the switching shock can be reduced while suppressing the pseudo contour of the moving image. it can.
This means that, for example, when different processings are performed on the still image portion and the moving image portion in the image encoding process, the transition to the encoding method switching can be smoothly performed.

Here, the shape including a polygonal line whose minimum unit is the pixel interval as a main element can be a checkered shape. Here, the shape including a polygonal line having a pixel interval as a minimum unit as a main element can be a shape in which polygonal lines having a pixel interval as a minimum unit are randomly combined.

Here, the predetermined image portion of the portion where the image signal has a predetermined characteristic can be a non-edge portion of the image signal. As a result, in particular, it is possible to quickly switch the encoding method in the edge portion of the image after suppressing the encoding switching shock in the non-edge portion of the image where the encoding switching shock is likely to stand out. Encoding suitable for each region can be performed without degrading the average signal-to-noise ratio of the entire image.

Further, in order to achieve the second object, according to the present invention, one TV field is configured by arranging a plurality of subfields each having a luminance weight in time order and can be expressed by combining the subfields. An image in which a desired image of one TV field is displayed in multiple gradations by performing a different encoding according to the amount of motion by using a combination of different brightness weights according to the amount of motion of the input image signal from among various gradation values. A display device, in the case of the encoding, to the image signal in the switching boundary portion of the encoding method,
It is characterized in that a modulation signal having a cycle of at least a pixel interval is applied.

Further, in order to achieve the second object, according to the present invention, one TV field is formed by arranging a plurality of subfields each having a luminance weight in time order,
By using different combinations of luminance weights according to the amount of motion of the input image signal from among the grayscale values that can be expressed by combining the subfields, different encoding is performed according to the amount of motion, and the desired 1TV field An image display device for displaying an image in multi-gradation, characterized in that, at the time of the encoding, the image signal at the switching boundary of the encoding method is subjected to modulation for shifting the display position.

As a result, even if a switching shock occurs in an image portion for which the coding method has been switched, this position can be dispersed, so that the switching shock can be reduced while suppressing the moving image pseudo contour. it can.
This means that, for example, when different processings are performed on the still image portion and the moving image portion in the image encoding process, the transition to the encoding method switching can be smoothly performed.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Image display devices according to embodiments will be specifically described below with reference to the drawings. <Embodiment 1> [Overall Configuration] An image display device according to the present embodiment is an AC type plasma display panel (hereinafter, referred to as "PD
Image display device that performs halftone display by expressing a gradation by a total of a predetermined number (for example, 10) of light emission of subfields having a predetermined number of light emission as a luminance weight. Is.

FIG. 1 is a block diagram showing the configuration of an image display device according to the present embodiment of the present invention. The image display device has an inverse gamma correction circuit 2 as shown in FIG.
An adder circuit 3, a still image encoding circuit 4, a moving image encoding circuit 5, a motion detection circuit 6, a selection circuit 7, a subfield control circuit 8, a display control circuit 9, and an AC type plasma display. The panel 10 (hereinafter referred to as "PDP 10"), a differential circuit 11, a coefficient circuit group 12, and a delay circuit group 13 are included.

The inverse gamma correction circuit 2 is a circuit for performing exponential correction processing so as to further suppress the light emission luminance in the portion where the gradation value of the input image signal 1 is small. That is, it is configured to output a 12-bit image signal to which the decimal 4 bits of the 8-bit input image signal is added. Since this is because the input image signal 1 is usually based on the inverse gamma characteristic of a CRT, if the light emission brightness is digitally controlled by the number of light emission pulses like a PDP, the level of the input image signal is Since the gradation value and the emission brightness have a linear relationship, the gradation cannot be expressed correctly, and therefore, the gradation value is provided to avoid this.

The signal passed through the adder circuit 3 is supplied to the still picture coding circuit 4 and the moving picture coding circuit 5. The still image encoding circuit 4 includes a look-up table in which a value to be converted is associated with each gradation value of each input image signal, and desired encoding is performed based on this table. FIG. 2 shows a part of the lookup table. The vertical column on the left end of FIG. 2 shows the value of the input image signal, and the horizontal column shows the value of the signal to which the input image signal should be converted.

As shown in this figure, basically, encoding is performed by converting into a signal having the same value as the input image signal, but in "4", "9", "14", ... (In the figure, a column with a thick line frame 41, etc.) encodes a signal having a value different from that of the input image signal and having a neighboring value (in the case of “4”, “5”, in the case of “9”) In the case of "10" and "14", "15"). This is to represent all the input image signals by some value corresponding to the encoding in the subfield control circuit (encoding to divide into subfields having a predetermined luminance weight), and to continuously express the luminance value. This is because the jump is caused in the changed portion of the brightness value without changing to.

The moving picture coding circuit 5 also has a look-up table in which a value to be converted is associated with each gradation value of each input image signal, and desired coding is performed based on this table. FIG. 3 shows a part of the lookup table.
The column on the left end of FIG. 3 indicates the value of the input image signal, and the column on the side thereof indicates the value of the signal to which the input image signal should be converted.

As shown in this figure, basically, encoding is performed by converting into a signal having the same value as the input image signal, but "4", "9", "14", ... In the same manner as above (columns with thick line frame 51, etc.), all input image signals are expressed by some value and luminance values are continuously expressed in correspondence with encoding in the subfield control circuit. In order to cause a jump in the changing portion of the brightness value without changing the value of the input image signal, a signal in the vicinity of the gradation value is encoded with a value different from the input image signal (in the case of "4", "5", "9"). "
In the case of "10", in the case of "14" it is "15"). Further, the moving picture coding circuit 5 performs unique coding which is not carried out by the still picture coding circuit 4. That is, the shaded area 51 in FIG.
As shown in the columns marked with, "40", "50", "7"
In the case of a predetermined input image signal having a value such as "0", "80", ..., It is possible to display on the panel by the sum of the luminance weights of the respective subfields. A value close to it to ensure the correlation (for example, "30" for an input image signal having a value of "40",
The input image signal having the value of "50" is converted into "60" or the like).

FIG. 4 is a block diagram showing a detailed structure of the motion detection circuit 6. As shown in this figure, the motion detection circuit 6 is provided with each one of the image signals supplied from the inverse gamma correction circuit.
Two frame memories 61 for storing frames
A, 61B, difference circuit 62, and motion detection signal generation circuit 6
3 and 3. As a result, the difference circuit 62 reads out the image signal from the frame memories 61A and 61B and compares the image signal for the frame to be displayed with the image signals for the immediately preceding frame and two frames for each pixel to calculate a difference value. This difference value is supplied to the motion detection signal generation circuit 63. In the motion detection signal generation circuit 63, if the difference value exceeds the reference value, it is determined to be a moving image, and if it is less than the reference value, it is determined to be a still image. Is generated and output to the selection circuit 7.

Next, the selection circuit 7 selects from the still picture coding circuit 4 and the moving picture coding circuit 5 a motion detection signal supplied from the motion detection circuit, which is a still picture or a moving picture, as a selection signal. Either one of the supplied image signals is selected and supplied to the subfield control circuit 8 and the difference circuit 11. FIG. 5 is a block diagram showing the configuration of the subfield control circuit 8.

As shown in this figure, the subfield control circuit 8 comprises a subfield conversion circuit 81, a write address control circuit 82, and frame memories 83A and 83B. The write address control circuit 82 generates an address designating signal designating a write address to the frame memory based on the horizontal synchronizing signal (Hsyc) and the vertical synchronizing signal (Vsyc) separated from the image signal.

The subfield converter 81 includes a selection circuit 7
It is a circuit which receives an image signal supplied from the device and which converts the image signal corresponding to each pixel into here 10-bit field information having a predetermined weighting. Specifically, a look-up table in which information to be converted is determined according to the gradation level of the input image signal (the signal before passing through the still image encoding circuit and the moving image encoding circuit) is determined by a predetermined lookup table. The image signal is divided into a number of subfields. Note that the division processing for each pixel is performed by a PL not shown.
It is performed in synchronization with the pixel clock generated by the L circuit.

The field information is a set of 1-bit subfield information indicating which time zone in one TV field, that is, which subfield is to be turned on or off. Here, the field information corresponding to each pixel generated in this way has a physical address designated by an address designation signal from the write address control circuit 82, and is stored in the frame memories 83A and 83B line by line, pixel by pixel, field by field. It is written for each screen.

FIG. 6 shows the correspondence between the subfield converter 81 and the information to be converted according to the gradation level of the input image signal. In FIG. 6, the input signals are “1”, “2”, “5”, “10”, “20”, “3” in order of time.
3 ”,“ 48 ”,“ 66 ”,“ 87 ”,“ 111 ”, and the input image signal for converting into ON / OFF information of the 10-bit subfields SF1 to SF10 having the brightness weights changing, The table shows the correspondence with the combination of subfields after conversion. The vertical column of this table shows the value of the input image signal, and the horizontal column shows the 10-bit field to which the input image signal is to be converted. Shows information. It should be noted that the subfield marked "1" in this figure is "on (lit)" and the other subfields are "off (non-lit)" during the field period (the same applies hereinafter). .

For example, in the sub-field conversion circuit 81, if the image signal is "40" (column indicated by a thick frame 84), the image signal is given a luminance weight of "2", "5", "3".
"0000100" that combines the subfields of "3"
It is converted into 10-bit data "110" and output.
Note that the bit representation here is represented by associating the subfield number with the digit in the bit representation.

Next, each of the frame memories 83A and 83B has an internal structure as shown in FIG. That is,
The frame memory 83A has a front half (1 to L) of one screen.
The first memory area 83A1 for storing field information corresponding to (240 lines) and the front half (1
To L (240) lines) and a second memory area 83A2 for storing field information.

The frame memory 83B has a first memory area 83B1 for storing field information corresponding to the rear half of one screen (L + 1 to 2L (480) lines) and the rear half of another screen (L + 1 to L + 1). Second memory area 83 for storing field information corresponding to 2L (480 lines)
With B2. Then, the first memory area 83A1 (first
Memory area 83B1) and the second memory area 83A2 (second memory area 83B2) each have 10 memory areas.
The subfield memories SFM1 to SFM10 are provided. With this configuration, field information related to a combination of 10-bit subfields corresponding to two screens divided into the first half and the second half for one screen is used as information about lighting / non-lighting of each subfield, and the subfield memories SFM1 to SFM1 to Written to SFM10. In the present embodiment, the subfield memories SFM1 to SF
The M10 uses a semiconductor memory having a 1-bit input and a 1-bit output. In addition, this frame memory 83A, 83B
Is a 2-port frame memory capable of simultaneously writing field information and reading it to the display control circuit 9.

To write field information in the frame memories 83A and 83B, the first half of the field information for one screen is stored in the first memory 83A1, and the second half of the field information for one screen is stored in the first memory. 83B1 and the field information of the first half of the next one screen to the second memory area 83A2 and the field information of the second half of the other one screen to the second memory area 83B2. Four memory areas 83A1 and 8 of the frame memories 83A and 83B
Alternately for 3B1, 83A2 or 83B2. And one memory area 83A1, 83B1, 83A2 and 83B2
The writing of the field information into the sub-field conversion circuit 81 is performed by using the 10-bit data output from the sub-field conversion circuit 81 in synchronization with the pixel clock as the 10 sub-field memories SFM1 to SFM.
It is executed by a method of writing by distributing to the FM 10 bit by bit. Which bit of the 10-bit data is stored in which subfield memory SFM1 to SFM10 is predetermined.

The display control circuit 9 has a display line control circuit 91, an address driver 92A, and an address driver 92A, as shown in FIG.
92B and a line driver 93.
The display line control unit 91 includes frame memories 83A and 83B.
Memory areas 83A1 and 83B to be read to the PDP 10
It designates 1, 83A2 or 83B2, a line and a subfield, and gives an instruction as to which line of the PDP 10 is to be scanned.

The operation of the display line control unit 91 is performed by the frame memories 83A, 8A in the subfield control circuit 8.
The writing operation to 3B and the order of each screen are synchronized. That is, the display line control unit 91 causes the memory areas 83A2, 83B2 (83A1, 83) in which 10-bit data is being written.
Reading is not performed from B1), but reading is performed from the memory areas 83A1 and 83B1 (83A2 and 83B2) that have already been written.

The address driver 92A outputs the subfield information corresponding to one line serially input bit by bit based on the memory area designation, the read line designation and the subfield designation of the display line control section 91. Bits (640 bits) corresponding to the number of pixels are converted into address pulses in parallel and output to the front half line of the screen. Similarly to the line driver 92A, the address driver 92B converts the subfield information into address pulses and outputs the address pulses to the lines of the latter half of the screen.

The line driver 93 is used to specify to which line of the PDP 10 the subfield information is to be written by a scanning voltage pulse. With such a configuration of the display control circuit 9, the frame memory 83 is as follows.
The field information is read from A, 83B to the PDP 10. The reading of the field information for one screen divided and written in the frame memories 83A and 83B is performed by simultaneously reading the data corresponding to the front half and the rear half. That is, the subfield information is sequentially read from the memory areas 83A1 and 83B1 for each pixel simultaneously from the subfield memories SFM1, SFM2, ..., SF10. More specifically, first,
Subfield information corresponding to each pixel on the first line is sequentially read out bit by bit from the subfield memories SFM1 in both the memory areas 83A1 and 83B1. Then, after waiting for the line designation by the line driver 93, a latent image is formed (addressing) on each of the first and second half screens, and then the same subfield memory SFM1 is used.
From the sub-field information corresponding to each pixel on the second line of the first half / second half screen and serially input to the address drivers 92A and 92B in the same manner, and the bits corresponding to the number of pixels on one line, here 640 bits Subfield information is output to the PDP 10 in parallel and addressing is performed. Such read (write)
When all the lines are completed up to the last line in the divided area divided into screens, the number of discharge pulses corresponding to the luminance weight of the subfield SF1 is applied by the address driver to cause all the pixels to emit light all at once.

After the subfield information regarding lighting / non-lighting of the next subfield SF2 is read line by line in the same manner as above and the addressing is performed, when this operation is sequentially repeated until the subfield SF10, 1
The reading (writing) of the field information for the screen is completed. FIG. 9 illustrates an operation method of such a PDP. In FIG. 9, the horizontal axis represents time and the vertical axis represents PD.
The number of the electrode extending in the lateral direction of P, that is, the number of the scanning / discharging sustaining electrode is shown, the address of the pixel to be made to emit light is designated by the thick shaded portion, and the pixel is made to emit light at the shaded portion. That is, for all the horizontal pixels on the scan / discharge sustaining electrodes of the first line of each divided screen, the subfield SF
Addressing is performed by applying address pulses to the address electrodes running in the vertical direction at the timing when 1 starts. After the addressing of the first line of the scan / discharge sustaining electrodes is completed, the same operation is repeated for the subsequent lines. After the addressing of the last scan / discharge sustaining electrode on the split screen is completed, time t1
The t2 discharge maintaining period starts. During this period, the number of discharge sustaining pulses proportional to the weighting is applied to the discharge sustaining electrodes, but only the pixels that have been instructed to emit light by the above address designation emit light. Then, as will be repeatedly described, the gradation display for one TV field is completed by repeating the operations of addressing in the subfield and simultaneous lighting of all pixels as described above.

Then, in parallel with the above-mentioned reading, the field information corresponding to the front half and the rear half of the next screen written in another memory area is read out in the same manner as described above, so that image display is performed one after another. Next, the adder circuit 3, the difference circuit 11, the coefficient circuit group 12, and the delay circuit group 13 will be described.

The difference circuit 11 is a circuit for calculating the difference between the image signal output from the selection circuit and the image signal passed through the adder circuit 3, and supplies the difference signal to each circuit of the coefficient circuit group 12. The coefficient circuit group 12 is 7/16, 1/1
It has coefficients of 6, 5/16, 3/16.

The delay circuit group 13 delays the signal that has passed through the coefficient circuit group 12. Specifically, one pixel (1
D) 1 line (1H) +1 pixel (1D), 1 line (1H), 1 line (1H) -1 pixel (1D) delay. The adder circuit 3 performs addition processing of the image signal that has passed through the inverse gamma correction circuit 2 and the signal that has passed through the delay circuit group 13 and supplies it to the still image coding circuit 4, the moving image coding circuit 5, and the difference circuit 11. To do.

By the addition circuit 3, the difference circuit 11, the coefficient circuit group 12, and the delay circuit group 13 as described above, the difference between the gradation value that should be originally displayed and the gradation value that is actually displayed is determined by A loop known as error diffusion, which distributes to the pixels, is constructed. [Advantages] First, by setting the luminance weighting in each subfield as described above, while maintaining the resolution in the low gradation value portion equivalent to that of the image display device using the conventional PDP, A wide dynamic range that cannot be obtained with things is realized.

FIG. 10 is a characteristic diagram and a chart showing the correlation between the value of the input image signal and the emission luminance. This FIG.
As shown in (a) and (b), in the low gradation value portion, the change of the light emission luminance changes smoothly and gently with respect to the change of the input in both the still image and the moving image. For example,
Input value is "0", "1", "2", "3", "4", "5", "6"
, "0", "1", "1", "2", "2", "3",
Make it “3”.

On the other hand, as shown in FIG. 10C, when light is emitted in the high gradation value portion, for example, in all subfields, the maximum luminance value is "1 + 2 + 5 + 10 + 33 +".
48 + 66 + 87 + 111 ”=“ 383 ”, which means that a maximum luminance value that is 1.5 times the maximum luminance value of the conventional“ 255 ”can be obtained, which enables image expression with a wide dynamic range.

The dynamic range can be widened in this way when all combinations of luminance values (grayscale values) selectable in the subfield control circuit are rearranged in the order of luminance values (grayscale value order). It is possible to generate a portion where the brightness value (gradation value) jumps (the gradation value of the input image signal is "4", "9", "14", etc.), and by this, the minimum brightness value and the maximum expressible. This is because it is possible to make the ratio with the brightness value larger than in the conventional case.

Here, in order to make the luminance value jump,
Setting conditions are important. That is, the predetermined brightness weight is
For example, the brightness weight “2” of the subfield SF2,
The luminance weight of the subfield with the next highest luminance weight
(In the above example, the luminance weight of the subfield SF3
It is set to be less than 1/2 of "5"). Also, another
In other words, the subfields are arranged in the ascending order of the luminance weights.
, The subfield with the i-th smallest intensity weight
Brightness weight of W_iAnd then W₁+ W ₁+ W₂+ ... + W_n
<W_{n + 1}Intensity weights are assigned such that there are n
It can be said that it is being done. In the above example, n
= 2.

In order to make the dynamic range wider, it is necessary to make the jump value of the luminance value larger. Therefore, in this case, when the sub-fields are arranged in the ascending order of the brightness weights and the brightness weight of the sub-field having the jth smallest brightness weight is W _j , W _i + W ₁ + W ₂ +
The brightness weights are assigned so that there are n where i is + W _n <W _{n + 1} and two or more i. This makes it possible to further widen the dynamic range.

Next, in the case of a moving image, as described above, only an image signal having a value limited to a part of the gradation value used for displaying a still image is used. For example, the shaded area 51 in FIG.
As shown in the column marked with, the image signals converted into "30" and "60" are used for the input image signals having the values of "40" and "50", respectively. What if we didn't do this conversion? That is, normally, an image signal having a value of "40" is given a luminance weight of "2", "5", "3".
The light emission is performed in the three subfields of "3", and the subfield of the luminance weight "20" emitted when displaying the image signal having the value of "30" is turned off.

For this reason, the correlation between the gradation value of the input image signal and the light emission pattern is broken, and the occurrence of a moving image pseudo contour is observed in the moving image portion. Here, in the moving image portion, "3" is applied to the gradation value of the input image signal of "40".
As shown in an example in which an image signal having a value of “0” is substituted for display, in the image display device according to the present embodiment, when the gradation value of the input image signal increases, the subfield from the ON state to the OFF state is changed. The luminance weight of the subfield controlled from the ON state to the OFF state can be relatively reduced without the control or when the gradation value of the input image signal is increased, so that the occurrence of the moving image pseudo contour is prevented. The suppressed image display becomes possible.

Further, as described above, the still picture coding circuit 4
Since the moving picture coding circuit 5 performs coding for converting a predetermined input image signal into a value different from the original gradation value, the difference from the gradation value actually displayed on the PDP is left as it is. However, it cannot be said that the image can be displayed correctly. Therefore, the adder circuit 3, the difference circuit 11, the coefficient circuit group 12, and the delay circuit group 1 as described above are provided.
The error diffusion loop configured by 3 distributes the difference between the gradation value that should be originally displayed and the gradation value that is actually displayed to the surrounding pixels.

As a result, the gradation jump is compensated, and good gradation display is performed. In the present embodiment, the number of subfields and the luminance weight in each subfield are merely examples, and the present invention is not limited to this. In particular, if it is possible to increase the number of subfields, add subfields with smaller luminance weights to improve the gradation resolution at low luminance, or add subfields with larger luminance weights. It goes without saying that the maximum brightness value can be improved.

<Second Embodiment> FIG. 11 is a block diagram showing a configuration of an image display device according to a second embodiment of the present invention. As shown in FIG. 11, the image display device has a configuration in which a display gradation magnification setting circuit 14 is added to the configuration of the image display device according to the first embodiment, and it corresponds to the maximum gradation value of the input image signal. This is different from the first embodiment in that the still picture coding circuit 4, the moving picture coding circuit 5, and the subfield control circuit 8 are configured so that the coding can be switched. The differences will be described below. In addition,
Here, in order to simplify the explanation, for the sake of convenience, it is assumed that the input image signal is a signal in the range of 22 to 110 gradations.

The display gradation ratio setting circuit 14 is a ratio of the maximum gradation value of the image of one frame (1 TV field) to be displayed to the reference gradation value (22 gradations) (hereinafter, referred to as "maximum gradation value"). This value will be referred to as a “K value.” The K value will be displayed at present with respect to the sum of the luminance weights of all the subfields used when displaying the reference TV field described in the claims. Display tv
"The ratio of the sum of the luminance weights of all subfields used when displaying a field". ) Is calculated, and the calculated K value is calculated as the still image encoding circuit 4 and the moving image encoding circuit 5,
And the subfield control circuit 8.

The still picture coding circuit 4, the moving picture coding circuit 5, and the subfield control circuit 8 carry out predetermined coding based on the K value. First, the still image encoding circuit 4
Performs a predetermined encoding for each of K values of 1, 2, 3, 4, and 5, but for a code other than K = 1, a gradation value (luminance value) jumps. Execute Such encoding is performed by a plurality of lookup tables in which the input image signal and the gradation value to be converted (encoded) are associated with each other for each K value (similar to the one shown in FIG. 2). ). In encoding with K = 2, 3, 4, and 5, the values shown in FIGS.
(D) As shown in the leftmost column of each drawing, the gradation value (luminance value) does not continuously change, and the specific gradation value (luminance value) jumps.

Also, in the moving picture coding circuit 5, the predetermined coding is performed for each of the K values of 1, 2, 3, 4, 5; Encoding is performed so that (luminance value) jumps. Further, the encoding limited to the image signal having the specific gradation value is executed (the image signal having a star mark on the left side of each drawing in FIG. 14 is limited to the signal having the specific gradation value so as not to be used. Similarly, in FIG. 26, which will be described later, the image signal marked with * is limited to a signal of a specific gradation value so as not to be used). Such encoding is performed by a plurality of look-up tables in which an input image signal and a gradation value to be converted (encoded) are associated with each other for each K value (similar to the one shown in FIG. 3). ).

Next, when the K value is 1, 2, 3, 4, or 5, the subfield control circuit 8 uses the determined encoding table (look-up table) to generate an image signal corresponding to each pixel. Is converted into 5-bit field information having a predetermined weighting here. Normally, when switching the encoding in the subfield control circuit based on the value of the K value, FIG.
From (e) to (e), in the reference coding pattern (here, the luminance weights of the subfields are “1, 2, 3, 6, 10” in the time order shown in FIG. 12A)). Each pixel in the frame having the corresponding K value is displayed using the coding pattern in which the brightness weight is set to the brightness weight obtained by multiplying each brightness weight by the K value. However, this makes it possible to increase the brightness value to be displayed, but it is not possible to expand the dynamic range of the gradation value to be displayed. That is, as shown in FIGS. 13A to 13E, in the correlation between the input image signal and the emission brightness,
In the low gradation part, the luminance becomes large with respect to the input (the part indicated by the circled frame 201 in the figure), so the resolution in the low gradation value part also decreases and the dynamic range cannot be expanded. Note that the right diagram in FIG. 13 is an enlarged view of the left diagram and shows the same contents (the same applies to FIG. 15).

On the other hand, in the image display device according to the present embodiment, as shown in FIGS. 14A to 14E, the reference coding pattern (here, the time sequence shown in FIG. The subfield luminance weights are "1, 2, 3,
6, 10 ”), a value obtained by multiplying the low-luminance brightness weight by a value equal to or less than the K value is set as the brightness weight, and the high-luminance brightness weight value exceeds the K value. Each pixel in the frame having the corresponding K value is displayed using the coding pattern in which the value obtained by multiplying by is set as the luminance weight.

Such a coefficient for multiplying the brightness weight can be a coefficient that increases monotonically according to the order of the size of the brightness weight. Further, such a coefficient by which the brightness weight is multiplied can be a coefficient that is isosterically changed according to the order of the brightness weight. In addition, such a coefficient by which the brightness weight is multiplied can be a coefficient that changes proportionally according to the order of the brightness weight.

Particularly, in order to further widen the dynamic range, it is effective to use a coefficient that changes proportionally. Specifically, for each K value, the coefficient by which the brightness weight “1, 2, 3, 6, 10” is multiplied is K = 2; 1, 1.5, 2, 1.83, 2. 3, when K = 3;
1, 2, 2.67, 1.83, 2.83, 3.6, when K = 4; 1, 2.5, 4, 3.83, 4.7, when K = 5; 2, It will be 3.5, 4.67, 4.83 and 5.8.

Here, for example, in the case of K = 2 and K = 3, the subfields belonging to the subfield group calculated by multiplying by the coefficient equal to or less than the K value have a plurality of possible K values. By including a fixed subfield in the luminance weight obtained by multiplying the minimum value (coefficient; 1) that can be set among the values, an increase in luminance with respect to the input in the low gradation portion is suppressed. Also, the larger the K value,
The value of the coefficient by which the brightness weight of the reference coding pattern is multiplied is generally increased in order to increase the maximum brightness value.

That is, image display is performed using a coding pattern composed of a subfield group having a luminance weight that is multiplied by a coefficient equal to or less than a K value and a subfield group having a luminance weight that is multiplied by a coefficient that is greater than a K value. . By setting the brightness weighting in this way, it is possible to increase the brightness value to be displayed and also to expand the dynamic range of the gradation value to be displayed. That is, as shown in FIGS. 15A to 15E, in the correlation between the input image signal and the light emission luminance, the luminance is kept small with respect to the input in the low gradation portion (circle frame 202 in the figure). (Portion indicated by) and the resolution in the low gradation value portion can be maintained and the dynamic range can be widened.

Further, as the K value becomes larger, it is necessary to increase the value at which the brightness value jumps in order to widen the dynamic range. Therefore, the ratio of the value multiplied by the luminance weight of high luminance and the value multiplied by the luminance weight of low luminance is set to be larger in a TV field having a larger K value. Consequently, arranging the subfields in ascending order of the luminance weight, when the luminance weight of the subfield having a small luminance weight j th was _{W j, W i + W 1} + W 2 + ···
Luminance weights can be assigned in TV fields with large K values such that there are n with + W _n <W _{n + 1} and i of 2 or more.

Explaining in the above example, W ₁ = 1, W ₂ = 5,
When W ₃ = 12, W ₄ = 23, W ₅ = 47, W ₂ + W ₁ +
There are n = 4 and i = 2 such that W ₂ + ... + W ₄ (46) <W _{4 + 1} (47). Thus, in a TV field having a large K value, the dynamic range can be effectively expanded by further increasing the degree of jumping of the luminance value.

The combination of the brightness weights is not limited to the above, and the approximate values of the brightness weight ratios are "1: 2: 3" and "1:".
"2: 4", "1: 2: 5", "1: 2: 6", "1:"
"3: 7", "1: 4: 9", "2: 6: 12", "2:
If a combination including any two or more of "6:16" is used, a jump in the luminance value can be generated, so that the dynamic range can be expanded.

Further, using the error diffusion loop as in the first embodiment, a process of distributing the difference between the gradation value that should be originally displayed and the gradation value that is actually displayed to the peripheral pixels is performed. By carrying out the step, it is possible to compensate for the jump of the gradation and to display an excellent gradation. <Third Embodiment> FIG. 16 is a block diagram showing a configuration of an image display device according to the present embodiment.

As shown in FIG. 16, the image display device further includes the spatial modulation circuit 15 for spatially modulating the motion detection signal from the motion detection circuit 6, and the spatial display circuit according to the first embodiment. A random number generation circuit 16 for supplying a random number value is added to the modulation circuit 15. Hereinafter, differences from the first embodiment will be described. FIG. 17 shows an example of the input image and the motion detection result in this embodiment.

A triangular object 203 shown in FIG.
17B moves to the right as shown in FIG. 17B, the moving part detected from the TV field before and after the input image signal becomes like a black-painted part 204 in FIG. 17C. On the other hand, the random number generation circuit 16 generates a random number from, for example, “−3” to “3”, and the value is supplied to the spatial modulation circuit 15, and the spatial modulation circuit 15 shows only the pixels corresponding to the generated random number. The pixel position of the motion detection signal of the signal of c) is displaced in the horizontal direction or the vertical direction, and the motion signal represented by the black-painted portion 205 of FIG. 17D is obtained as the switching signal of the selection circuit.

Conventionally, the still image portion and the moving image portion are switched and encoded by using the motion detection signal shown in FIG. 17C. However, if the shape of the region of the switching signal is linear, the switching is accompanied. The light emission pattern also tended to be linear, resulting in switching shock. On the other hand, when the one shown in FIG. 17 (d) is used as the coding switching signal, the boundary portion thereof has a random shape, and therefore, when the coding is switched using such a signal, Since a region in which the still picture coding method and the moving picture coding method differ from each other is formed in the switching boundary portion, the PD is changed due to the switching of the coding.
Changes in the temporal characteristics of light emission in P10 are not uniform, and it becomes difficult to notice the switching of the encoding, and the switching between the still image encoding portion and the moving image encoding portion can be smoothly performed.

The above effect can be recognized if the shape of the boundary portion of the switching signal is not a straight line, and the pixel positions are irregularly shifted in the above description, but they may be regularly displaced. . Further, the above effect can be obtained even if the switching signal has a shape including a polygonal line whose minimum unit is the pixel interval as a main element. Fourth Embodiment FIG. 18 is a block diagram showing the configuration of the image display device according to the present embodiment.

As shown in FIG. 18, the image display device further includes a signal modulation circuit 17 for amplitude-modulating the motion detection signal from the motion detection circuit 6 in addition to the image display device according to the first embodiment. A boundary detection circuit 18 for supplying a signal indicating a boundary between a moving image and a still image is added to the modulation circuit 17. Hereinafter, differences from the first embodiment will be described.

FIG. 19 shows an example of the input image and the motion detection result in this embodiment. Assuming that the triangular object 206 shown in FIG. 19A moves to the right as shown in FIG. 19B, the moving part detected from the TV field before and after the input image signal is the black-painted part in FIG. 19C. It looks like 207. On the other hand, the boundary detection circuit 18 detects a boundary portion where the value of the detected motion detection signal changes, and based on this signal, the signal modulation circuit 17 modulates the signal in the amplitude direction only on the boundary portion of the motion detection signal. Then, the signal represented by the peripheral portion 208A of the black-painted portion 208 in FIG. 19D is obtained as the selection circuit switching signal. In FIG. 19D, the modulation signal is drawn in a checkered pattern.

When the switching signal thus modulated at the boundary between the moving image and the still image is used, the same as above,
Since the boundary portion has a random shape, a region in which the still image coding method and the moving image coding method that are different from each other are mixed is formed in the switching boundary portion. When the encoding is switched, the changes in the temporal characteristics of light emission in the PDP 10 are not aligned due to the switching of the encoding, and the switching of the encoding becomes unnoticeable, and the still image encoding portion and the moving image are not displayed. This makes it possible to smoothly switch to the coded part.

In addition, since the encoding method is modulated at the boundary between the moving image and the still image, it is ensured that the image is a still image portion and a moving image portion while suppressing the encoding switching shock. In the region, the coding method can be fixed, and unnecessary switching of the coding method can be suppressed to perform image display without deterioration of the signal-to-noise ratio.

Although the signal for modulating the boundary of the motion detection signal has a regular pattern in FIG. 19, the same effect can be obtained even if the modulation method at the detected boundary portion uses a random number. To be <Fifth Embodiment> FIG. 20 is a block diagram showing a configuration of an image display device according to the present embodiment.

As shown in FIG. 20, this image display device differs from that of the fourth embodiment in that an addition circuit 19 and a random number generation circuit 20 (here, "1", as a signal modulation circuit, Random values of "0" and "-1" are generated, and three image coding circuits 21, 22, 23 are used instead of the still image coding circuit 4 and the moving picture coding circuit 5. Is that a selection circuit 24 having three signal inputs is provided instead of the selection circuit 7, and the motion detection circuit 6 detects the amount of image motion in three stages.

Each of the image coding circuits 21, 22 and 23 performs stepwise coding as shown in FIGS. That is, in the still image portion, as shown in FIG. 21A, the gradation characteristics are emphasized in the encoding, and in the moving image portion, the encoding is performed.
Encoding is limited to the gradations in which the pseudo contour of the moving image is unlikely to occur as shown in (b) and (c). FIG. 21A shows the coding performed in the intermediate motion part, and FIG. 21C shows the coding performed in the relatively large motion part.

On the other hand, the motion detection / detection circuit 6 similarly detects the motion of the image stepwise in three steps, and further obtains a boundary part where the motion detection signal changes by the boundary detection circuit 18, and a random number is generated in this part. A signal generated by the circuit 20 and having a value obtained by adding a random number to the value of the motion detection signal is generated in the addition circuit 19, and this signal is used as a switching signal for the selection circuit 23.

By the above operation, the encoding method can be fixed in the portion which is surely the still image portion and the moving image portion, and unnecessary encoding method switching can be suppressed to prevent deterioration of the signal-to-noise ratio. In addition to being able to display an image that is not present, intermediate encoding can be performed in a portion located between the still image area and the moving image area, and encoding can be switched in stages to smoothly switch. In addition, since the switching control signal is modulated at the boundary portion of coding switching, the conspicuous coding switching shock is further suppressed.

<Sixth Embodiment> FIG. 22 is a block diagram showing a configuration of an image display apparatus according to the present embodiment. As shown in FIG. 22, the image display device includes the boundary detection circuit 18 and a random number generation circuit 20 (here, it is assumed that a random number “0” or “1” is generated). Instead of the signal modulation circuit 17 of the image display device according to the fourth embodiment, signal modulation circuits 25 and 26 that perform amplitude modulation on the output signals from the still image coding circuit 4 and the moving image coding circuit 5 are provided. There is.

FIG. 23 shows an example of the input image and the motion detection result in this embodiment. Assuming that the triangular object 209 shown in FIG. 23 (a) moves to the right as shown in FIG. 23 (b), the moving part detected from the TV field before and after the input image signal is the black part shown in FIG. 23 (c). It becomes like 210. On the other hand, the boundary detection circuit 18 obtains a boundary portion where the motion detection signal changes, and in this portion, a random number is generated by the random number generation circuit 20 and used as an operation switching signal for the signal modulation circuit 25 and the signal modulation circuit 26.

Then, the signal modulation circuits 25 and 26 perform modulation in the amplitude direction of the image signal, and the image signals from the signal modulation circuit 25 and the signal modulation circuit 26 are selected by the selection circuit using the motion detection signal as a switching signal. It As a result, the image signal that has passed through the selection circuit is the black-painted portion 21 in FIG.
It is represented by 1. In FIG. 23D, the image signal is drawn in a checkered pattern.

When the image signal thus modulated at the boundary between the moving image and the still image is used, the image at the boundary has a random shape in the same manner as described above, and therefore still image coding is performed at the switching boundary. Since a region in which the encoding method and the encoding method different from the moving image encoding method are mixed is formed, the change of the encoding is not accompanied by the change of the temporal characteristics of the light emission in the PDP 10, and the encoding is switched. This makes it difficult to notice, and the switching between the still image coding portion and the moving image coding portion can be smoothly performed.

In addition, since the encoding method is modulated at the boundary between the moving image and the still image, it is ensured that the image is a still image portion and a moving image portion while suppressing the encoding switching shock. In the region, the coding method can be fixed, and unnecessary switching of the coding method can be suppressed to perform image display without deterioration of the signal-to-noise ratio.

<Embodiment 7> FIG. 24 is a block diagram showing a configuration of an image display apparatus according to the present embodiment. As shown in FIG. 24, the image display device is replaced with the spatial modulation circuit 15 of the image display device according to the third embodiment.
Spatial modulation circuits 27 and 28 that perform spatial modulation on the image signals from the still picture coding circuit 4 and the moving picture coding circuit 5 are provided. Hereinafter, differences from the third embodiment will be described.

FIG. 25 shows an example of the input image and the motion detection result in this embodiment. If the triangular object 212 shown in FIG. 25 (a) moves to the right as shown in FIG. 25 (b), the moving parts detected from the TV field before and after the input image signal are shown in black in FIG. 25 (c). It becomes like 213. On the other hand, the random number generation circuit 16 generates a random number from "-3" to "3", and the value thereof is the spatial modulation circuit 26.
And 28, the spatial modulation circuits 27 and 28 shift the pixel position of the image signal of the moving image portion of FIG. 25C in the horizontal direction or the vertical direction by the pixel corresponding to the generated random number,
The spatially modulated signal is selected by the selection circuit using the signal from the motion detection circuit as a switching signal, and the image signal represented by the black-painted portion 214 in FIG. 25D is obtained in the moving image portion.

When the image signal thus modulated at the boundary between the moving image and the still image is used, the image at the boundary has a random shape in the same manner as described above. Therefore, still image coding is performed at the switching boundary. Since a region in which the encoding method and the encoding method different from the moving image encoding method are mixed is formed, the change of the encoding is not accompanied by the change of the temporal characteristics of the light emission in the PDP 10, and the encoding is switched. This makes it difficult to notice, and the switching between the still image coding portion and the moving image coding portion can be smoothly performed.

In addition, since the coding method is modulated at the boundary between the moving image and the still image, it is ensured that the image is a still image portion and a moving image portion while suppressing the encoding switching shock. In the region, the coding method can be fixed, and unnecessary switching of the coding method can be suppressed to perform image display without deterioration of the signal-to-noise ratio.

Incidentally, in the above third to seventh embodiments,
In particular, the coding switching method is not linear in this part by limiting the non-edge part in which the gradation value of the input image signal does not change at all or is small as the image part where the shock of coding switching is conspicuous. By doing so, it is possible to quickly switch the encoding method in the edge portion of the image while suppressing the encoding switching shock that is easily noticeable in the non-edge portion of the image.
It is more desirable because suitable coding can be performed for each area without degrading the average signal-to-noise ratio of the entire image.

It is also possible to combine the second embodiment with the above third to seventh embodiments. It should be noted that in the second embodiment, the display gradation magnification setting circuit 14 tries to display the reference gradation value with respect to the reference gradation value.
The case where the magnification “K value” of the maximum gradation value of the image of the frame (1 TV field) is all positive numbers has been described, but it is not limited to positive numbers and may be a decimal number. FIG. 26 is a characteristic diagram showing the correlation between the coding pattern and the input image signal and the emission luminance when K = 2.5.

As shown in FIG. 26A, the reference coding pattern (here, the luminance weights of the subfields are "1, 2, 3, 6, 10" in the time order shown in FIG. 14A).
In the luminance weight in the pattern), a value obtained by multiplying the low-luminance luminance weight by a value equal to or less than the K value is set as the luminance weight, and the high-luminance luminance weight is multiplied by a value exceeding the K value. Each pixel in the frame having the corresponding K value is displayed by using the coding pattern in which is set as the luminance weight.

Specifically, the brightness weights "1, 2, 3, 6, 1
The coefficients to be multiplied by "0" are 1, 1.5, 2.33, 2.5, 2.
It becomes 9. By setting the brightness weighting in this way, it is possible to increase the brightness value to be displayed and also to expand the dynamic range of the gradation value to be displayed. That is, as shown in FIGS. 26B and 26C, in the correlation between the input image signal and the light emission luminance, the luminance is kept small with respect to the input in the low gradation portion.
It is possible to maintain the resolution in the low gradation value portion and widen the dynamic range.

[0110]

As described above, the present invention is
An image display device configured to configure a TV field by arranging a plurality of subfields each having a brightness weight in time order, and displaying a 1TV field image in multiple gradations by turning on a desired subfield. 1 of the luminance weight of the subfield having the next largest luminance weight
It is characterized in that it includes subfields that are less than / 2.

Further, one TV field is constructed by arranging a plurality of subfields each having a luminance weight in time order, and a desired subfield is turned on to perform 1TV.
An image display device for displaying an image of a field in multi-gradation, wherein the subfields are arranged in ascending order of brightness weight, and when the brightness weight of the subfield having the i-th smallest brightness weight is W _i , W ₁ + W It is characterized in that the luminance weights are assigned so that there exists n in which ₁ + W ₂ + ... + W _n <W _{n + 1} .

With these, when all selectable luminance value (gradation value) combinations are rearranged in the order of luminance value (gradation value), a portion where the luminance (gradation) jumps can be generated. The ratio between the minimum luminance value and the maximum luminance value that can be expressed can be made larger than in the conventional case, so that image display with a wide dynamic range can be realized.

Further, according to the present invention, one TV field is configured by arranging a plurality of subfields each having a luminance weight in time order, and a desired subfield is turned on to display an image of one TV field in multiple gradations. When the subfields are arranged in ascending order of brightness weight and the brightness weight of the subfield having the jth smallest brightness weight is W _j , W _i + W ₁ + W ₂ + ... + W _n <
It is characterized in that the brightness weights are assigned so that n of W _{n + 1} and i of 2 or more exist.

Thus, when all selectable luminance value (gradation value) combinations are rearranged in the order of luminance value (gradation value), it is possible to cause a jump in luminance (gradation). The ratio between the minimum luminance value and the maximum luminance value that can be expressed can be made larger than in the conventional case, so that image display with a wide dynamic range can be realized. Further, by this, the jump width of the brightness value can be controlled according to the gradation value of the input image signal. For example, the jump width of the brightness value is allowed as the brightness value is higher, and the maximum brightness value that can be displayed is further increased. It can be set large.

Further, according to the present invention, one TV field is constructed by arranging a plurality of sub-fields each having a luminance weight in time order, and a desired sub-field is turned on to display an image of one TV field in multiple gradations. In addition, in the image display device configured to control the maximum display brightness according to the characteristics of the input image signal, a TV field including a plurality of subfields configured by a combination of predetermined brightness weights is a reference TV field. And the luminance weights of all subfields in the coding pattern used to display the display TV field to be displayed at present with respect to the sum of the luminance weights of all subfields in the coding pattern used to display the reference TV field. When the ratio of the sum of the
The coding pattern used to display the fields is a subfield having a luminance weight calculated by multiplying the luminance weight of a predetermined subfield in the reference TV field by a coefficient of K or less, and a predetermined subfield in the reference TV field. Sub-field having a luminance weight calculated by multiplying the luminance weight of 1 by a coefficient exceeding K.

As a result, when the maximum displayable luminance value is controlled according to the maximum gradation value of the image or the distribution degree of the high gradation area, the minimum displayable luminance value is always kept small and the displayable maximum luminance value is maintained. The maximum brightness value can be controlled as needed. In general, in an image including a relatively bright portion, if the maximum luminance value that can be displayed is increased more than necessary, the power consumption as a whole will decrease in a display device such as a plasma display panel that has a high correlation between the emission luminance and the power consumption. Since it may increase, it is desirable to control the maximum displayable brightness value according to the content of the image. When such control is performed, even if the maximum displayable luminance value is increased, for example, a subfield having a small luminance weight is always kept a relatively small value, while a subfield having a relatively large luminance weight is kept. Since the brightness weight is changed according to the desired maximum displayable brightness value, the ratio between the minimum brightness value and the maximum brightness value can be made large, and even if the maximum brightness value is displayed large, the image The part close to the black level does not rise, and the sense of contrast is not impaired.

Further, according to the present invention, one TV field is formed by arranging a plurality of subfields each having a luminance weight in time order, and the input image is selected from the gradation values that can be expressed by combining the subfields. An image display device for performing multi-gradation display of an image of a desired 1 TV field by performing different encoding depending on the amount of motion by using a combination of different luminance weights depending on the amount of motion of a signal. In this case, the image signal at the switching boundary portion of the encoding method is encoded so as to include an area in which a plurality of encoding methods are mixed in a portion having a predetermined characteristic.

Further, according to the present invention, one TV field is formed by arranging a plurality of subfields each having a luminance weight in time order, and the input image is selected from among the gradation values that can be expressed by combining the subfields. An image display device for performing multi-gradation display of an image of a desired 1 TV field by performing different encoding according to the amount of motion by using a combination of different luminance weights according to the amount of motion of a signal,
At the time of the encoding, in a portion where the image signal at the switching boundary portion of the encoding method has a predetermined characteristic, the signal for switching the encoding method is irregularly shifted in the pixel direction.

Further, according to the present invention, one TV field is formed by arranging a plurality of subfields each having a luminance weight in time order, and the input image is selected from among the gradation values that can be expressed by combining the subfields. An image display device for performing multi-gradation display of an image of a desired 1 TV field by performing different encoding according to the amount of motion by using a combination of different luminance weights according to the amount of motion of a signal,
At the time of the encoding, in a portion where the image signal at the switching boundary portion of the encoding method has a predetermined characteristic, the signal for switching the encoding method is regularly shifted in the pixel direction. .

Further, according to the present invention, one TV field is formed by arranging a plurality of subfields each having a luminance weight in time order, and the input image is selected from among the gradation values that can be expressed by combining the subfields. An image display device for performing multi-gradation display of an image of a desired 1 TV field by performing different encoding according to the amount of motion by using a combination of different luminance weights according to the amount of motion of a signal,
At the time of the encoding, in the portion where the image signal at the switching boundary portion of the encoding method has a predetermined characteristic, the shape at the switching boundary portion of the signal for switching the encoding method has the pixel interval as the minimum unit. It is characterized by having a shape including a polygonal line as a main element.

Further, according to the present invention, one TV field is formed by arranging a plurality of subfields each having a luminance weight in time order, and the input image is selected from among the gradation values that can be expressed by combining the subfields. An image display device for performing multi-gradation display of an image of a desired 1 TV field by performing different encoding according to the amount of motion by using a combination of different luminance weights according to the amount of motion of a signal,
At the time of the encoding, a modulation signal having a period of at least a pixel interval is applied to the image signal at the switching boundary portion of the encoding method.

Further, according to the present invention, one TV field is formed by arranging a plurality of subfields each having a luminance weight in time order, and the input image is selected from among the gradation values that can be expressed by combining the subfields. An image display device for performing multi-gradation display of an image of a desired 1 TV field by performing different encoding according to the amount of motion by using a combination of different luminance weights according to the amount of motion of a signal,
At the time of the encoding, the image signal at the switching boundary of the encoding method is subjected to modulation for shifting the display position.

As a result, even if a switching shock occurs in the image portion for which the encoding method has been switched, this position can be dispersed, so that the switching shock can be reduced while suppressing the moving image pseudo contour. it can.
This means that, for example, when different processings are performed on the still image portion and the moving image portion in the image encoding process, the transition to the encoding method switching can be smoothly performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an image display device according to a first embodiment.

FIG. 2 is a diagram showing a correspondence between an input image signal and an image signal to be converted in a still image encoding circuit.

FIG. 3 is a diagram showing a correspondence between an input image signal and an image signal to be converted in the moving picture coding circuit.

FIG. 4 is a block diagram showing a configuration of a motion detection circuit.

FIG. 5 is a block diagram showing a configuration of a subfield control circuit.

FIG. 6 is a diagram showing a correspondence between an input image signal and subfield information.

FIG. 7 is a diagram showing a configuration of a frame memory in a subfield control circuit.

FIG. 8 is a block diagram showing a configuration of a display control circuit.

FIG. 9 is a diagram showing an operating method of a PDP.

10A, 10B, and 10C are characteristic diagrams and charts showing the correlation between the value of the input image signal and the emission luminance.

FIG. 11 is a block diagram showing a configuration of an image display device according to a second embodiment.

12A to 12E are charts showing modes when switching the encoding in the subfield control circuit based on the value of each K value (conventional ones).

FIG. 13 is a characteristic diagram showing the correlation between the input image signal and the emission brightness as shown in (a) to (e) (conventional one).

14 (a) to 14 (e) are diagrams showing aspects when switching the encoding in the subfield control circuit based on the value of each K value (the present invention).

FIG. 15 is a characteristic diagram showing the correlation between the input image signal and the emission brightness as shown in (a) to (e) (of the present invention).

FIG. 16 is a block diagram showing a configuration of an image display device according to a third embodiment.

FIG. 17 shows an example of an input image and a motion detection result.

FIG. 18 is a block diagram showing a configuration of an image display device according to a fourth embodiment.

FIG. 19 shows an example of an input image and a motion detection result.

FIG. 20 is a block diagram showing a configuration of an image display device according to a fifth embodiment.

FIG. 21 is a diagram showing an aspect of encoding in each image encoding circuit.

FIG. 22 is a block diagram showing a configuration of an image display device according to a sixth embodiment.

FIG. 23 shows an example of an input image and a motion detection result.

FIG. 24 is a block diagram showing a configuration of an image display device according to a seventh embodiment.

FIG. 25 shows an example of an input image and a motion detection result.

FIG. 26 is a characteristic diagram showing the correlation between the coding pattern and the input image signal in the case of K = 2.5 and the emission luminance.

[Explanation of symbols]

1 Input image signal 2 Inverse gamma correction circuit 3 adder circuit 4 Still picture coding circuit 5 Video coding circuit 6 Motion detection circuit 7 selection circuit 8 Subfield control circuit 9 Display control circuit 10 AC type plasma display panel 11 Difference circuit 12 coefficient circuit group 13 Delay circuit group 14 Display gradation magnification setting circuit 15 Spatial modulation circuit 16 Random number generator 17 Signal modulation circuit 18 Boundary detection circuit 19 adder circuit 20 Random number generator 21, 22, 23 Image coding circuit 24 selection circuit 25,26 Signal modulation circuit 27, 28 Spatial modulation circuit 81 Subfield conversion circuit 82 write address control circuit 83A, 83B frame memory

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09G 3/20 660 G09G 3/20 660W 3/28 3/28 K

Claims (9)

[Claims] 1. A 1TV field is configured by arranging a plurality of subfields each having a luminance weight in time order, and the amount of motion of an input image signal is selected from gradation values that can be expressed by combining the subfields. An image display device that performs different encoding according to the amount of motion by using a combination of different brightness weights according to the above, and that displays an image of a desired 1 TV field in multiple gray scales. An image display device characterized in that an image signal at a switching boundary portion of an encoding method is encoded so as to include an area in which a plurality of encoding methods are mixed in a portion having a predetermined characteristic. 2. A 1TV field is configured by arranging a plurality of subfields each having a luminance weight in time order, and the amount of motion of an input image signal is selected from gradation values that can be expressed by combining the subfields. An image display device which performs multi-gradation display of an image of a desired 1TV field by performing different encoding according to the amount of motion by using a combination of different brightness weights according to, An image display device characterized in that a signal for switching the encoding method is irregularly shifted in a pixel direction in a portion where an image signal at a switching boundary portion of the encoding method has a predetermined characteristic. 3. A 1 TV field is formed by arranging a plurality of subfields each having a luminance weight in time order, and the movement of the input image signal is selected from the gradation values that can be expressed by combining the subfields. An image display device for performing multi-gradation display of an image of a desired 1 TV field by performing different encoding according to the amount of motion by using a combination of different brightness weights according to the amount, and at the time of the encoding An image display device characterized in that a signal for switching the encoding method is regularly shifted in the pixel direction in a portion where an image signal at a switching boundary portion of the encoding method has a predetermined characteristic. 4. A 1TV field is configured by arranging a plurality of subfields each having a luminance weight in time order, and the amount of motion of an input image signal is selected from gradation values that can be expressed by combining the subfields. An image display device which performs multi-gradation display of an image of a desired 1TV field by performing different encoding according to the amount of motion by using a combination of different brightness weights according to, In the portion where the image signal at the switching boundary portion of the encoding method has a predetermined feature, the shape at the switching boundary portion of the signal for switching the encoding method includes a polygonal line whose minimum unit is a pixel interval as a main element. An image display device having a shape. 5. The image display device according to claim 4, wherein the shape including a polygonal line whose minimum unit is a pixel interval as a main element is a checkered shape. 6. The image according to claim 4, wherein the shape including a polygonal line having a pixel interval as a minimum unit as a main element is a shape in which polygonal lines having a pixel interval as a minimum unit are randomly combined. Display device. 7. The image display according to claim 1, wherein the predetermined image portion of the portion where the image signal has a predetermined characteristic is a non-edge portion of the image signal. apparatus. 8. A 1TV field is configured by arranging a plurality of subfields each having a luminance weight in time order, and the amount of motion of an input image signal is selected from gradation values that can be expressed by combining the subfields. An image display device which performs multi-gradation display of an image of a desired 1TV field by performing different encoding according to the amount of motion by using a combination of different brightness weights according to, An image display device, wherein a modulation signal having a cycle of at least a pixel interval is applied to the image signal at the switching boundary of the encoding method. 9. A 1TV field is configured by arranging a plurality of subfields each having a luminance weight in time order, and the amount of motion of an input image signal is selected from gradation values that can be expressed by combining the subfields. An image display device which performs multi-gradation display of an image of a desired 1TV field by performing different encoding according to the amount of motion by using a combination of different brightness weights according to, An image display device, wherein the image signal at the boundary of switching of the encoding method is modulated to shift the display position.