JP2001034229A - Picture display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display a picture having a really wide dynamic range by increasing a ratio of a maximum value to a minimum value of a brightness value displayable within a same screen, by including a sub-field of which the brightness weight is made smaller than a half of a brightness weight of a sub-field having the next largest brightness weight. SOLUTION: A sub-field conversion part 81 receives the supply of a picture signal from a selection circuit, and converts a picture signal corresponding to each pixel into field information having a predetermined prescribed weighting. To expand a dynamic range, when the combinations of all selectable brightness values are rearranged in order of brightness value, a sub-field control circuit 8 is able to generate a jumping part of the brightness values, and this makes it possible to increase a ratio of a minimum brightness value to an expressible maximum brightness value. To make a brightness value jump, a brightness weight is to be set so that a prescribed brightness weight is smaller than a half of the brightness weight of a sub-field having the next largest brightness weight.

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 which divides one TV field of an image into a plurality of sub-field images and displays the divided images to perform multi-tone display. The present invention relates to an image display device capable of displaying an image having a wide dynamic range by enlarging a ratio between a maximum value and a minimum value of luminance values that can be displayed within the image display device.

Further, the present invention relates to a display device for displaying a multi-gradation image by dividing an image for one TV field into a plurality of sub-field images and displaying the image. The present invention relates to a multi-gradation image display device capable of performing display with improved disturbance.

[0003]

When a multi-tone image is displayed using a display panel based on binary display, such as when a plasma display panel is used, one TV field of the image is divided into a plurality of images. There is known a method of dividing an image into sub-fields, giving each sub-field a predetermined luminance weight, controlling the presence or absence of light emission for each sub-field, and displaying an image.

For example, to display 256 gradations,
One TV field of the input image signal is divided into eight subfields, and the luminance weight of each subfield is set to "1,""2,""4,""8,""16," and "3."
2 "," 64 ", and" 128 ". Further, assuming that the input image signal is an 8-bit digital signal, this is assigned to eight sub-field images in order from the least significant bit and displayed. Each subfield image is a binary image.

On the other hand, in image display using a CRT, CR
Even if T itself has a so-called inverse gamma characteristic and the maximum luminance value is a value corresponding to a value proportional to “255”,
The minimum luminance value is a value corresponding to a value proportional to a decimal number equal to or less than “1”, and the so-called dynamic range is a sufficient value of 255 or more. However, in the plasma display panel, the emission characteristics are linear, and the gradation value is displayed by the sum of the emission luminances substantially proportional to the subfield weights. The luminance value is a value corresponding to the sum of the weights of the respective sub-fields, "255". Since the minimum luminance value is larger than that of the CRT, the image display has a narrow dynamic range.

On the other hand, it is not easy to increase the number of subfields that can be displayed by increasing the number of subfields, because of limitations such as the discharge speed of the plasma display. Is done. Further, in the above-described method of displaying 256 gradations using eight subfields in the related art, it is known that a so-called remarkable pseudo-contour-like gradation disturbance occurs in moving image display.

Therefore, as one method of eliminating the gradation disturbance, an attempt has been made to detect the motion of an image and change the encoding for each pixel or each area. This is because, for example, by changing the encoding method for each image region, the light emission of 256 gradation values is performed for the input 256 gradations in the still image portion, and the gradation value is limited in the moving image portion. To emit light. By doing so, in the moving image portion, encoding is performed in which the continuity of the change of the light emission pattern is secured to some extent with respect to a monotonous change in the gradation value of the input image signal. The contour can be reduced. Further, in the still image portion, the original sufficient gradation is secured.

However, in such a conventional method alone, coding is switched at a boundary between a moving image portion and a still image portion, and a switching shock may be observed in this portion depending on an image. In particular, this switching shock may be seen near the boundary of an image in which the object moves with a flat portion as a background. The present invention
The present invention has been made in view of the above problems, and has been made in consideration of the following.
In a display device using a plasma display panel or the like, in which a field component is divided into a plurality of sub-field images and displayed for multi-gradation 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 having a truly wide dynamic range by increasing the ratio.

It is another object of the present invention to provide a multi-tone image display device capable of improving the gradation disturbance of the half tone display generated at the time of displaying a moving image and displaying an image in which the switching shock is inconspicuous. The purpose of.

[0010]

In order to achieve the first object, according to the present invention, one TV field is constituted by arranging a plurality of sub-fields each having a luminance weight in chronological order. Turn on the subfield and 1T
An image display apparatus for displaying an image of a V field in multiple gradations, wherein the image display device includes a subfield whose luminance weight is set to less than 輝 度 of the luminance weight of a subfield having the next highest luminance weight. .

Further, one TV field is composed of a plurality of sub-fields each having a luminance weight and arranged in chronological order.
The image field an image display apparatus for a multi-tone display, when arranging the subfields in ascending order of the luminance weight, the luminance weights of the subfields with small luminance weight i-th and the W _i, W ₁ + W wherein the luminance weight as ₁ + W is _{2 + ··· + W n <W} n + 1 a is n there is assigned.

Thus, when all selectable combinations of luminance values (gradation values) are rearranged in the order of luminance values (gradation values), a portion where the luminance (gradation) jumps can be generated. Since the ratio between the minimum luminance value and the representable maximum luminance value can be made larger than in the past, an image display with a wide dynamic range can be realized.

Further, one TV field is constituted by arranging a plurality of subfields each having a luminance weight in chronological order.
The image field an image display apparatus for a multi-tone display, when arranging the subfields in ascending order of the luminance weight, the luminance weights of the subfields with small luminance weight j th was W _j, W _i + W ₁ + W ₂ +... + W _n <W _{n + 1} , wherein a luminance weight is assigned so that n and two or more i exist.

Thus, when all selectable combinations of luminance values (gradation values) are rearranged in the order of luminance values (gradation values), a portion where the luminance (gradation) jumps can be generated. Since the ratio between the minimum luminance value and the representable maximum luminance value can be made larger than in the past, an 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 higher the brightness value, the more the jump width of the brightness value is allowed, and further the maximum displayable brightness value is set. Can be set large.

Further, according to the present invention, one TV field is constituted by arranging a plurality of sub-fields each having a luminance weight in chronological order, and a desired sub-field is turned on to display an image of one TV field in multi-gradation. An image display device configured to control a maximum display luminance according to characteristics of an input image signal, wherein a TV field including a plurality of subfields formed by a combination of predetermined luminance weights is used as a reference TV field. And the luminance weight of all the subfields in the encoding pattern used to display the display TV field to be currently displayed with respect to the sum of the luminance weights of all the subfields in the encoding pattern used when displaying the reference TV field When the ratio of the sum of
An encoding pattern used for displaying a field includes a subfield having a luminance weight calculated by multiplying a luminance weight of a predetermined subfield in the reference TV field by a coefficient equal to or less than K, and a predetermined subfield in the reference TV field. And a subfield having a luminance weight calculated by multiplying the luminance weight by a coefficient exceeding K.

Accordingly, when the maximum luminance value that can be displayed is to be controlled in accordance with the maximum gradation value of the image or the degree of distribution of the high gradation area, the minimum displayable luminance value is always kept small, and the displayable minimum luminance value is maintained. The maximum brightness value can be controlled as needed. In general, if the maximum luminance value that can be displayed is increased more than necessary for an image including a relatively bright portion, the power consumption of a display device such as a plasma display panel, which has a high correlation between the light emission luminance and the power consumption, as a whole, is reduced. It is desirable to control the maximum luminance value that can be displayed according to the content of the image because there is a possibility that it will increase. When such control is performed, even if the maximum luminance value that can be displayed is particularly increased, for example, a subfield with a small luminance weight always keeps a relatively small value, while a subfield with a relatively large luminance weight Changes the luminance weight according to the desired maximum displayable luminance value, so that the ratio between the minimum luminance value and the maximum luminance value can be increased. The portion 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 coefficients set based on a rule defined in 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 may be a coefficient that increases monotonously 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 an isotropic 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 an isometric 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 smaller than K is a subfield fixed to a luminance weight multiplied by a settable minimum value among a plurality of possible values of the K value. May 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”.
2: 5 "," 1: 2: 6 "," 1: 3: 7 "," 1:
4: 9 ”,“ 2: 6: 12 ”, and“ 2: 6: 16 ”and at least one of the encoding patterns determined according to the characteristics of the desired input image signal. 2
One of the subfields may be configured with the luminance weight.

Here, assuming that the sum of the luminance weights of all the subfields is S, a gradation display corresponding to a value “R” of “0” or more and “S” or less is selected from each subfield and performed. The combination of subfields in which the sum of the luminance weights of the selected subfields is the sum of the luminance weights closest to the value “R” may be selected and displayed in gradation.

As a result, a tone value which cannot be expressed only by a combination of a single subfield can be corrected by a well-known tone correction technique such as error diffusion or dither method. An image with a wide dynamic range can be displayed satisfactorily with smoothly corrected gradations while keeping the maximum luminance value large.

Here, the combination of luminance weights to be selected can be controlled by the amount of motion of the image or an approximate value of the motion of the image. As a result, the minimum luminance value is kept small, and the maximum luminance value is kept large, so that an image with a wide dynamic range can be displayed satisfactorily with smoothly corrected gradations. Can be suppressed.

Although the generation of the pseudo contour of the moving image is caused by the movement of the line of sight relative to the screen displayed by the observer, the amount of the image movement or the approximate value of the image movement may be used. Thus, a practically sufficient effect of suppressing false contours can be obtained.
Here, in a part where the amount of motion of the image or the approximate value of the amount of motion of the image is large, the coding is limited to the coding in which the increase in the gradation level of the input image signal and the temporal distribution of the luminance weight arrangement pattern have a monotonically increasing correlation. It can be.

This eliminates the control of the subfield from the ON state to the OFF state when the gradation value of the input image signal increases, or eliminates the control from the ON state when the gradation value of the input image signal increases. Since the luminance weight of the subfield controlled to be in the off state can be relatively reduced, it is possible to display an image in which the generation of the moving image false contour is more effectively suppressed.

Further, in order to achieve the second object, the present invention provides that one TV field is constituted by arranging a plurality of subfields each having a luminance weight in chronological order, and expressing the subfields in combination. An image in which a desired 1 TV field image is displayed in multiple gradations by using different combinations of luminance weights according to the amount of motion of the input image signal from among possible gradation values to perform different encoding according to the amount of motion. In the display device, at the time of the encoding, in a portion where the image signal at a switching boundary portion of the encoding method has a predetermined characteristic, the image signal is encoded so as to include a region where a plurality of encoding methods are mixed. It is characterized by.

In order to attain the second object, the present invention provides a TV field in which a plurality of subfields each having a luminance weight are arranged in chronological order, and the subfields are expressed in combination. By using different combinations of luminance weights according to the amount of motion of the input image signal from among possible gradation values, different coding is performed according to the amount of motion, and a desired 1 TV field image is displayed in multiple tones. 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 a pixel direction. It is characterized by making it.

In order to achieve the second object, according to the present invention, one TV field is constituted by arranging a plurality of subfields each having a luminance weight in chronological order, and expressed by combining the subfields. By using different combinations of luminance weights according to the amount of motion of the input image signal from among possible gradation values, different coding is performed according to the amount of motion, and a desired 1 TV field image is displayed in multiple tones. 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 regularly shifted in a pixel direction. It is characterized by having made it.

In order to achieve the second object, the present invention provides a TV field in which a plurality of sub-fields each having a luminance weight are arranged in chronological order, and the sub-fields are expressed in combination. By using different combinations of luminance weights according to the amount of motion of the input image signal from among possible gradation values, different coding is performed according to the amount of motion, and a desired 1 TV field image is displayed in multiple tones. 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 characteristic, the shape at the switching boundary portion of the signal to switch the encoding method, It is characterized by having a shape including a polygonal line having a pixel interval as a minimum unit as a main element.

As described above, even if a switching shock occurs in an image portion whose coding method has been switched, the occurrence position can be dispersed, so that the switching shock can be reduced while suppressing the moving image false contour. it can.
This means that, for example, when the image encoding process is performed differently for the still image portion and the moving image portion, the transition to the switching between the encoding methods can be smoothly performed.

Here, the shape including a polygonal line having a pixel interval as a minimum unit as a main element can be a checkerboard shape. Here, the shape including a polygonal line having a pixel interval as a minimum unit as a main element can be a shape obtained by randomly combining polygonal lines having a pixel interval as a minimum unit.

Here, the predetermined image portion of the portion where the image signal has predetermined characteristics can be a non-edge portion of the image signal. Thereby, in particular, since the encoding switching shock is suppressed in the non-edge portion of the image where the encoding switching shock is conspicuous, it is possible to quickly switch the encoding method in the edge portion of the image. Encoding suitable for each region can be performed without deteriorating the average signal-to-noise ratio of the entire image.

In order to achieve the second object, according to the present invention, one TV field is constituted by arranging a plurality of subfields each having a luminance weight in chronological order, and can be expressed by combining the subfields. An image in which a desired 1 TV field image is displayed in multiple tones by performing different encoding in accordance with the amount of motion by using a combination of different luminance weights according to the amount of motion of the input image signal from among various grayscale values A display device, at the time of the encoding, in the image signal at the switching boundary portion of the encoding method,
A modulation signal having a cycle of at least a pixel interval is applied.

In order to achieve the second object, according to the present invention, one TV field is constituted by arranging a plurality of sub-fields each having a luminance weight in chronological order.
By using different combinations of luminance weights according to the amount of motion of the input image signal from among the gradation values that can be expressed by combining the subfields, different encodings according to the amount of motion are performed, and the desired 1 An image display apparatus for displaying an image in multiple gradations, wherein at the time of the encoding, a modulation for shifting a display position is performed on an image signal at a switching boundary of the encoding method.

As described above, even if a switching shock occurs in an image portion whose coding method has been switched, the occurrence position can be dispersed, so that the switching shock can be reduced while suppressing the moving image false contour. it can.
This means that, for example, when the image encoding process is performed differently for the still image portion and the moving image portion, the transition to the switching between the encoding methods can be smoothly performed.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image display device according to an embodiment will be specifically described below with reference to the drawings. First Embodiment [Overall Configuration] An image display device according to the present embodiment is an AC-type plasma display panel (hereinafter, referred to as a “PD”).
An image display device that performs halftone display by expressing a gradation by the sum of light emission of a predetermined number (for example, 10) of subfields having a predetermined number of light emission times as a luminance weight It is.

FIG. 1 is a block diagram showing a configuration of an image display device according to the present embodiment of the present invention. The image display device includes an inverse gamma correction circuit 2 as shown in FIG.
, An addition circuit 3, a still picture coding circuit 4, a moving picture coding 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. It comprises a panel 10 (hereinafter referred to as “PDP10”), a difference circuit 11, a coefficient circuit group 12, and a delay circuit group 13.

The inverse gamma correction circuit 2 is a circuit for performing an exponential function correction process for further suppressing light emission luminance in a portion where the tone value of the input image signal 1 is small. That is, it is configured to output a 12-bit image signal obtained by adding 4 decimal bits of an 8-bit input image signal. This is because the input image signal 1 is generally based on the inverse gamma characteristic of a CRT. If the light emission luminance is digitally controlled by the number of light emission pulses like a PDP, the input image signal 1 Since the tonal value and the light emission luminance have a linear relationship, it is impossible to correctly express the gradation, and this is provided to avoid this.

The signal passing through the addition circuit 3 is supplied to a still picture coding circuit 4 and a 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 performs desired encoding based on this table. FIG. 2 shows a part of the lookup table. Note that the left vertical column in FIG. 2 shows the value of the input image signal, and the horizontal column shows the value of a signal to be converted from the input image signal.

As shown in the figure, basically, encoding for converting into a signal having the same value as the input image signal is performed. However, in "4", "9", "14",. (For example, a column with a thick frame 41 in the figure) encodes a signal having a value different from that of the input image signal into a signal of a nearby value (in the case of “4”, “5”, and in the case of “9”, "15" in the case of "10" or "14"). In this method, all input image signals are represented by some value, and the luminance value is continuously changed, in accordance with encoding in the subfield control circuit (encoding that is divided into subfields having a predetermined luminance weight). This is for causing a jump in a change portion of the luminance value without changing the luminance value.

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 performs desired coding based on this table. FIG. 3 shows a part of the lookup table.
Note that the left vertical column in FIG. 3 shows the value of the input image signal, and the horizontal column shows the value of a signal to be converted from the input image signal.

As shown in this figure, basically, encoding for converting into a signal having the same value as the input image signal is performed, but "4", "9", "14",... In (in the figure, a column with a thick line frame 51, etc.), all input image signals are represented by some value and the luminance value is continuously changed in correspondence with the encoding in the subfield control circuit in the same manner as described above. In order to cause a jump in a change portion of the luminance value without changing the luminance value, a signal different from the input image signal is encoded into a signal near the gradation value (in the case of “4”, “5”, “9”). "
Is "10" in the case of "14" and "15" in the case of "14"). Further, the moving image encoding circuit 5 performs unique encoding that is not performed by the still image encoding circuit 4. That is, the hatching 51 in FIG.
"40", "50", "7"
A predetermined input image signal having a value such as "0", "80",... Can be displayed on the panel by the sum of the luminance weights of the respective subfields. A value close to that value (for example, “30” for an input image signal with a value of “40”,
If the input image signal has a value of “50”, encoding is performed to convert it into “60” or the like.

FIG. 4 is a block diagram showing a detailed configuration of the motion detection circuit 6. As shown in this figure, the motion detection circuit 6 outputs one image signal each supplied from the inverse gamma correction circuit.
Two frame memories 61 for storing frames
A, 61B, a difference circuit 62, and a motion detection signal generation circuit 6
3 As a result, the difference circuit 62 reads out the image signals from the frame memories 61A and 61B, compares the frame to be displayed and the image signals of the immediately preceding frame and two frames, and calculates a difference value for each pixel. The difference value is supplied to the motion detection signal generation circuit 63, and the motion detection signal generation circuit 63 determines that the moving image is detected when the difference value exceeds the reference value, and that the image is a still image when the difference value is equal to or less than the reference value. Is generated and output to the selection circuit 7.

Next, the selection circuit 7 uses the motion detection signal, which is supplied from the motion detection circuit and indicates whether the image is a still image or a moving image, as a selection signal, from the still image coding circuit 4 and the moving image coding circuit 5. 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 the 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 specifying signal for specifying 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 sub-field converter 81 includes a selector 7
, And converts the image signal corresponding to each pixel into 10-bit field information having a predetermined weight in this case. Specifically, a predetermined look-up table in which information to be converted 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. The image signal is divided into a number of subfields. The dividing process for each pixel is performed by a PL (not shown).
This 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 should be turned on / off. Here, the field information corresponding to each pixel generated in this manner is stored in the frame memories 83A and 83B in units of lines, pixels, and fields by specifying a physical address by an address specifying signal from the write address control circuit 82. It is written for each screen.

FIG. 6 shows correspondence between information to be converted in accordance with the gradation level of the input image signal in the subfield converter 81. FIG. 6 shows that each of the input signals is classified into "1", "2", "5", "10", "20", "3" in order of time.
3 "," 48 "," 66 "," 87 "," 111 ", and an input image signal for converting into 10-bit subfields SF1 to SF10 on / off information comprising luminance weights that change, The vertical column of this table shows the value of the input image signal, and the horizontal column shows a 10-bit field to which the input image signal is to be converted. Indicates information. In this figure, the subfield described as "1" is "ON (lit)", and the other subfields have their field periods set to "OFF (non-lit)" (hereinafter the same). .

For example, in the subfield conversion circuit 81, if the image signal is "40" (the field indicated by the thick line frame 84), the image signal is subjected to luminance weights "2", "5", "3".
"0000100" combining the subfields of "3"
110 "and converted to 10-bit data and output.
Here, the bit expression is a notation in which the number of the subfield is associated with the digit in the bit expression.

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

The frame memory 83B includes a first memory area 83B1 for storing field information corresponding to the latter half (L + 1 to 2L (480) lines) of one screen, and a second half (L + 1 to L + 1 to 2L) of another screen. Second memory area 83 for storing field information corresponding to 2L (480) lines)
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, one screen is divided into a front half and a rear half, and field information on a combination of 10-bit subfields corresponding to two screens is used as information on lighting / non-lighting of each subfield. Written to SFM10. In the present embodiment, the sub-field memories SFM1 to SFM
M10 uses a 1-bit input and 1-bit output semiconductor memory. Also, the frame memories 83A and 83B
Is a two-port frame memory capable of writing field information and reading data to the display control circuit 9 at the same time.

To write the field information into the frame memories 83A and 83B, the first half of the field information of one screen is written into the first memory 83A1, and the second half of the field information of the one screen is written into the first memory 83A1. 83B1, the first half of the field information of the next screen is stored in the second memory area 83A2, and the second half of the field information of the other screen is stored in the second memory area 83B2. Four memory areas 83A1, 8 of frame memories 83A, 83B
It is performed alternately for 3B1, 83A2 or 83B2. Then, one of the memory areas 83A1, 83B1, 83A2 and 83B2
The field information is written into the 10 sub-field memories SFM1 to SFM by using 10-bit data output from the sub-field conversion circuit 81 in synchronization with the pixel clock.
It is executed in such a manner that the data is distributed and written into the FM 10 bit by bit. Which bits of the 10-bit data are stored in which subfield memories SFM1 to SFM10 is determined in advance.

The display control circuit 9 comprises a display line control circuit 91 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 out to the PDP 10
1, 83A2 or 83B2, a line, and a subfield are designated, and an instruction is given as to which line of the PDP 10 is to be scanned.

The operation of the display line control section 91 is based on the frame memories 83A, 83A in the subfield control circuit 8.
The writing operation to 3B is synchronized with the screen unit order. That is, the display line control unit 91 writes the 10-bit data to the memory areas 83A2, 83B2 (83A1, 83A2).
Reading is not performed from B1), and reading is performed from the already written memory areas 83A1, 83B1 (83A2, 83B2).

The address driver 92A transfers subfield information corresponding to one line serially input bit by bit on the basis of the memory area designation, readout line designation and subfield designation of the display line control unit 91. Bits (640 bits) corresponding to the number of pixels are converted into address pulses in parallel and output to the first half line on the screen. The address driver 92B converts the subfield information into an address pulse and outputs the address pulse to the second half of the screen, similarly to the line driver 92A.

The line driver 93 specifies to which line of the PDP 10 the subfield information is to be written by a scanning voltage pulse. With the configuration of the display control circuit 9 described above, the frame memory 83
Reading of field information from A and 83B to PDP 10 is performed. 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 first half and the rear half. That is, the subfield information is simultaneously read from the memory areas 83A1 and 83B1 for each pixel sequentially from the subfield memories SFM1, SFM2,..., SF10. More specifically, first,
Subfield information corresponding to each pixel on the first line is sequentially read out one bit at a time from the subfield memories SFM1 in both the memory areas 83A1 and 83B1. After waiting for the line designation by the line driver 93, a latent image is formed on the first line of each of the first and second half screens (addressing), and then the same subfield memory SFM1 is formed.
, The subfield information corresponding to each pixel on the second line of the first and second half screens is read out and sequentially input to the address drivers 92A and 92B in the same manner, and bits corresponding to the number of pixels of one line, here 640 bits The subfield information is output to the PDP 10 in parallel and addressing is performed. Such reading (writing)
Is completed up to the respective last lines in the divided area of the screen, the number of discharge pulses corresponding to the luminance weight of the subfield SF1 is applied by the address driver, and the pixels emit light simultaneously.

After the subfield information relating to the lighting / non-lighting of the next subfield SF2 is read out one line at a time in the same manner as described above and addressing is performed, then this operation is repeated up to the subfield SF10.
Reading (writing) of the field information for the screen is completed. FIG. 9 shows the 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 horizontal direction of P, ie, the scanning / discharge sustaining electrode, is indicated, the address of the pixel to emit light is designated by the hatched portion, and the pixel is caused to emit light at the shaded portion. That is, the subfield SF is applied to all the horizontal pixels on the scanning / discharge sustaining electrodes of the first line of each divided screen.
Addressing is performed by applying an address pulse to an address electrode running in the vertical direction at the timing when 1 starts. When the addressing of the first line of the scanning / discharge sustaining electrode is completed, the same operation is repeated for the subsequent lines. When the addressing of the last scanning / sustaining electrode is completed in the divided screen, the time t1 to
It shifts to the t2 discharge maintenance period. In this period, the number of sustaining pulses proportional to the weight is applied to the sustaining electrodes, but only the pixels for which light emission has been instructed by the above address designation emit light. Then, as will be described repeatedly, the above-described operations of addressing in the subfield and simultaneous lighting of all pixels are repeated, thereby completing the gradation display for one TV field.

Then, in parallel with the reading, the field information corresponding to the first half and the rear half of the next screen written in another memory area is read in the same manner as described above, so that the image display is successively performed. Next, the addition 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 that calculates the difference between the image signal output from the selection circuit and the image signal that has passed through the addition 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 and 3/16.

The delay circuit group 13 delays the signal passing through the coefficient circuit group 12, and specifically, one pixel (1
D) One line (1H) +1 pixel (1D), one line (1H), one line (1H) -1 pixel (1D) is delayed. The addition circuit 3 adds the image signal passed through the inverse gamma correction circuit 2 and the signal passed through the delay circuit group 13 and supplies the result to the still picture coding circuit 4, the moving picture coding circuit 5, and the difference circuit 11. I do.

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

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

On the other hand, as shown in FIG. 10C, when light emission is performed in a high gradation value portion, for example, in all subfields, the maximum luminance value becomes “1 + 2 + 5 + 10 + 33 +”.
48 + 66 + 87 + 111 ”=“ 383 ”, so that a maximum luminance value 1.5 times the maximum luminance value of the conventional general“ 255 ”can be obtained, and an image representation with a wide dynamic range can be realized.

The reason why the dynamic range can be expanded in this way is that the combination of all selectable luminance values (gradation values) in the subfield control circuit is rearranged in the luminance value order (gradation value order). A portion where the luminance value (gradation value) jumps can be generated (the gradation value of the input image signal is “4”, “9”, “14”, etc.), whereby the minimum luminance value and the maximum expressible value are obtained. This is because it is possible to increase the ratio with the luminance value as compared with the related art.

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

To obtain a wider dynamic range, it is necessary to increase the value at which the luminance value jumps. In this case, therefore, arranges the subfield 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 +
... + W _n <W _{n +1 The} luminance weight is assigned so that n and two or more i exist. This makes it possible to further expand 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 values used for displaying a still image is used. For example, the hatching 51 in FIG.
As shown in the column marked with, the input image signals having values of “40” and “50” use the image signals converted to “30” and “60”, respectively. What if you don't do such a conversion? That is, normally, an image signal having a value of “40” has luminance weights “2”, “5”, and “3”.
Light emission is performed in three subfields of "3", and the subfield of luminance weight "20" emitted when an image signal having a value of "30" is displayed is turned off.

Therefore, 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, the gradation value of the input image signal “40” is “3”.
As shown in the example in which an image signal is replaced with an image signal having a value of “0”, the image display device according to the present embodiment allows the sub-field of the on-state to the off-state when the gradation value of the input image signal increases. Eliminating the control or reducing the luminance weight of the subfield controlled from the on-state to the off-state when the gradation value of the input image signal increases, the generation of the moving image false contour can be reduced. The suppressed image display can be performed.

Further, as described above, the still picture coding circuit 4
In addition, since the moving image encoding circuit 5 performs encoding such that a predetermined input image signal is converted into a value different from the original gradation value, the difference from the gradation value actually displayed on the PDP as it is However, it cannot always be said that images can be displayed correctly. Therefore, the above-described addition circuit 3, difference circuit 11, coefficient circuit group 12, and delay circuit group 1
The error diffusion loop constituted by 3 performs a process of allocating a difference between a tone value that should be originally displayed to peripheral pixels and a tone value that is actually displayed.

As a result, the gradation jump is compensated, and a good gradation display is performed. In the present embodiment, the above content is an example of the number of subfields and the luminance weight in each subfield, and the present invention is not limited to this. In particular, when the number of sub-fields can be increased, a sub-field with a smaller luminance weight is added to improve the gradation resolution at low luminance, or a sub-field with a larger luminance weight is added. It goes without saying that the maximum luminance value can be improved.

<Embodiment 2> FIG. 11 is a block diagram showing a configuration of an image display apparatus according to the present embodiment of the present invention. As shown in FIG. 11, the image display device has a configuration in which a display gradation scale setting circuit 14 is added to the configuration of the image display device according to the first embodiment. This embodiment is different from the first embodiment in that the coding in the still picture coding circuit 4, the moving picture coding circuit 5, and the subfield control circuit 8 is switched. Hereinafter, the differences will be described. In addition,
Here, for the sake of simplicity, the description will be made on the assumption that the input image signal is a signal in the range of about 22 to 110 gradations for convenience.

The display gradation scale setting circuit 14 sets a magnification (hereinafter, referred to as a scale) of a maximum gradation value of an image of one frame (1 TV field) to be displayed with respect to a reference gradation value (22 gradations). This value is referred to as “K value.” This K value is to 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 the subfields used when displaying the field. ) Is calculated, and the calculated K value is used as the still image encoding circuit 4 and the moving image encoding circuit 5,
And supplies it to the subfield control circuit 8.

The still picture coding circuit 4, the moving picture coding circuit 5, and the subfield control circuit 8 perform predetermined coding based on the K value. First, the still picture coding circuit 4
Performs predetermined encoding when the K value is 1, 2, 3, 4, and 5, but when K is other than 1, a code that causes a jump in the gradation value (luminance value) is generated. Perform the conversion. Such encoding includes a plurality of look-up tables (similar to those shown in FIG. 2) in which an input image signal is associated with a gradation value to be converted (encoded) for each K value. ). In the encoding at each value of K = 2, 3, 4, and 5, in FIGS.
(D) As shown in the leftmost column of each figure, the specific gradation value (luminance value) jumps without continuously changing the gradation value (luminance value).

The moving picture coding circuit 5 also performs predetermined coding when the K value is 1, 2, 3, 4, and 5, however, except when K = 1, the gradation value (Luminance value) is encoded so that a jump occurs. Further, the encoding is limited to an image signal of a specific gradation value (the image signal is marked with a star on the left side of each drawing in FIG. 14 and is limited to a signal of a specific gradation value. Similarly, in FIG. 26 described later, the image signal is limited to a signal of a specific gradation value so as not to use the image signal marked with *.) Such encoding includes a plurality of look-up tables (similar to those shown in FIG. 3) in which an input image signal is associated with a gradation value to be converted (encoded) for each K value. ).

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 determine the image signal corresponding to each pixel. Is converted into 5-bit field information having a predetermined weight. Normally, when encoding is switched in the subfield control circuit based on the value of the K value, FIG.
To (e), a reference coding pattern (here, a pattern in which the luminance weight of each subfield is “1, 2, 3, 6, 10” in the time order shown in FIG. 12A) Each pixel in a frame having a corresponding K value is displayed using an encoding pattern set as a luminance weight obtained by multiplying a luminance value by a K value and each luminance weight. However, in this case, although the luminance value to be displayed can be increased, the dynamic range of the displayed gradation value cannot be widened. That is, as shown in FIGS. 13A to 13E, in the correlation between the input image signal and the emission luminance,
In the low gradation part, since the luminance becomes larger than the input (the part indicated by a circle 201 in the drawing), the resolution in the low gradation value part also decreases, and the dynamic range cannot be expanded. Note that the right figure in FIG. 13 is an enlarged view of the left figure 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, a reference coding pattern (here, each time sequence shown in FIG. The luminance weight of the subfield is “1, 2, 3,
6, 10 "), 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 a value exceeding the K value. Is displayed using a coding pattern in which a value obtained by multiplying by K is set as a luminance weight.

The coefficient for multiplying the luminance weight can be a coefficient that increases monotonically according to the order of the magnitude of the luminance weight. Further, such a coefficient by which the luminance weight is multiplied may be a coefficient that changes in an equal manner according to the order of the magnitude of the luminance weight. Further, the coefficient by which such luminance weight is multiplied can be a coefficient that changes in an equal ratio according to the order of the magnitude of the luminance weight.

In particular, in order to further expand the dynamic range, it is effective to use a coefficient that changes in an equal ratio. Specifically, at each K value, the coefficient by which the luminance 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, K = 4; 1, 2.5, 4, 3.83, 4.7, K = 5; 2, 3.5, 4.67, 4.83, and 5.8. Here, for example, when K = 2 and K = 3, the subfields belonging to the subfield group calculated by multiplying by a coefficient equal to or less than the K value are among a plurality of possible values of the K value. By including a fixed subfield with a luminance weight multiplied by the minimum value (coefficient: 1) that can be set in step (1), an increase in luminance with respect to input in a low gradation portion is suppressed. Also, as the K value increases, the value of the coefficient by which the luminance weight of the reference coding pattern is multiplied is generally increased in order to increase the maximum luminance value.

That is, image display is performed using an encoding pattern composed of a subfield group having a luminance weight multiplied by a coefficient equal to or less than the K value and a subfield group having a luminance weight multiplied by a coefficient exceeding the K value. . By setting the luminance weights in this way, it is possible not only to increase the luminance value to be displayed, but also to widen the dynamic range of the gradation values 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 part (the circle 202 in the figure). ), The resolution in the low gradation value portion can be maintained, and the dynamic range can be expanded.

Furthermore, in order to increase the dynamic range as the K value increases, it is necessary to increase the value at which the luminance value jumps. Therefore, the ratio of the value to be multiplied by the high-luminance luminance weight to the value to be multiplied by the low-luminance luminance weight is made larger in the TV field where the K value is larger. 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 + ···
A luminance weight can be assigned to a TV field having a large K value such that _n satisfying + W _n <W _{n + 1} and two or more i exist.

In the above example, W ₁ = 1, W ₂ = 5,
When W ₃ = 12, W ₄ = 23, and W ₅ = 47, W ₂ + W ₁ +
_{W 2 + ··· + W 4 (} 46) < is W ₄ + 1 (47) and comprising n = 4 and i = 2 would be present. As described above, in the TV field having a large K value, the dynamic range can be effectively expanded by further increasing the degree of the jump of the luminance value.

It should be noted that the present invention is not limited to the above combinations of the luminance weights, and the approximate values of the ratio of the luminance weights are “1: 2: 3” and “1: 2”.
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 tone value to be displayed originally to the surrounding pixels and the tone value to be actually displayed is performed. By performing the above, it is possible to compensate for the jump of the gradation and to perform a good gradation display. <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 a spatial modulation circuit 15 for spatially modulating the motion detection signal from the motion detection circuit 6 with the image display device according to the first embodiment. A modulation circuit 15 and a random number generation circuit 16 for supplying a random number value are added. Hereinafter, differences from the first embodiment will be described. FIG. 17 shows an example of an input image and a motion detection result in the present embodiment.

The triangular object 203 shown in FIG.
17B has moved to the right as shown in FIG. 17B, the moving portion detected from the TV field before and after the input image signal is as shown by a black portion 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 outputs only pixels corresponding to the generated random number in FIG.
The pixel position of the motion detection signal of the signal (c) is shifted in the horizontal direction or the vertical direction, and a motion signal represented by a black portion 205 in FIG. 17D is obtained as a switching signal of the selection circuit.

Conventionally, a still image portion and a moving image portion are switched and coded using the motion detection signal shown in FIG. 17C. However, if the region of the switching signal is linear, it is accompanied by the switching. The light emission pattern also tends to be linear, resulting in a switching shock. On the other hand, when the signal shown in FIG. 17D is used as the encoding switching signal, the boundary portion has a random shape. Therefore, when the encoding is switched using such a signal, Since a region where a different encoding method between the still image encoding method and the moving image encoding method is mixed is formed at the switching boundary portion, the PD is changed according to the switching of the encoding.
Changes in the temporal characteristics of the light emission at P10 also become uniform, making it difficult to notice that the encoding has been switched, so that the switching between the still image encoding portion and the moving image encoding portion can be smoothly performed.

If the shape of the boundary portion of the switching signal is not straight, the above effect is recognized. In the above description, the pixel position is shifted irregularly. However, the pixel position may be shifted regularly. . In addition, the above-described effect can be obtained even when the switching signal has a shape including a polygonal line having a pixel interval as a minimum unit as a main element. <Embodiment 4> FIG. 18 is a block diagram showing a configuration of an image display apparatus according to the present embodiment.

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

FIG. 19 shows an example of an input image and a motion detection result according to the present embodiment. Assuming that the triangular object 206 shown in FIG. 19A has moved 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 part shown in FIG. 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 at the boundary portion of the motion detection signal. Then, a signal represented by a peripheral portion 208A of the black portion 208 in FIG. 19D is obtained as a switching signal of the selection circuit. In FIG. 19 (d), the modulation signal is drawn in a checkered pattern.

As described above, by using the switching signal modulated at the boundary between the moving image and the still image,
Since the boundary portion has a random shape, a region in which different coding methods of the still image coding method and the moving image coding method are mixed is formed at the switching boundary portion. When the encoding is switched, the temporal characteristics of the light emission in the PDP 10 are not evenly changed due to the switching of the encoding, and the switching of the encoding becomes inconspicuous. Switching to the encoding portion can be performed smoothly.

In addition, since the encoding method is modulated at the boundary between a moving image and a still image, it is ensured that the image is a still image portion and a moving image portion while suppressing a noticeable encoding switching shock. In the region, the encoding method can be fixed, and unnecessary image method switching 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 is shown in FIG. 19 as a regular pattern, the same effect can be obtained by using a random number as the modulation method at the detected boundary. Can be <Embodiment 5> FIG. 20 is a block diagram showing a configuration of an image display apparatus according to the present embodiment.

As shown in FIG. 20, the image display apparatus is different from that of the fourth embodiment in that an addition circuit 19 and a random number generation circuit 20 (here, “1”, It is assumed that random numbers “0” and “−1” are generated.) And three image encoding circuits 21, 22, and 23 are used instead of the still image encoding circuit 4 and the moving image encoding circuit 5. Is provided with a selection circuit 24 having three signal inputs in place of the selection circuit 7, and the motion detection circuit 6 detects the amount of motion of an image in three stages.

Each of the image coding circuits 21, 22, and 23 performs stepwise coding as shown in FIGS. That is, as shown in FIG. 21A, encoding is performed with emphasis on gradation characteristics in a still image portion, and in FIG.
Encoding is limited to gradations in which a moving image false contour hardly occurs as shown in (b) and (c). FIG. 21A shows coding performed in an intermediate motion portion, and FIG. 21C shows coding performed in a relatively large motion portion.

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

By the above operation, the encoding method can be fixed in the portion where the still image portion and the moving image portion are surely secured, unnecessary switching of the encoding method is suppressed, and deterioration of the signal-to-noise ratio is reduced. In addition to being able to display no image, a portion located between the still image region and the moving image region can be subjected to intermediate encoding and the encoding can be switched stepwise so that the switching can be smoothly performed. In addition, since the switching control signal is modulated at the boundary of the coding switching, the coding switching shock is further suppressed from being noticeable.

<Embodiment 6> 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 the random number generation circuit 20 (here, it is assumed that a random number of “0” or “1” is generated), and further, Instead of the signal modulation circuit 17 of the image display device according to the fourth embodiment, signal modulation circuits 25 and 26 for performing amplitude modulation on output signals from the still image encoding circuit 4 and the moving image encoding circuit 5 are provided. I have.

FIG. 23 shows an example of an input image and a motion detection result according to the present embodiment. Assuming that the triangular object 209 shown in FIG. 23A has moved to the right as shown in FIG. 23B, the moving part detected from the TV field before and after the input image signal is a black part shown in FIG. It looks like 210. On the other hand, the boundary detection circuit 18 finds a boundary portion where the motion detection signal changes, and in this portion, generates a random number by the random number generation circuit 20 and uses it as an operation switching signal for the signal modulation circuit 25 and the signal modulation circuit 26.

Then, the modulation of the image signal in the amplitude direction is performed by the signal modulation circuits 25 and 26, and the image signal from the signal modulation circuit 25 and the signal modulation circuit 26 is selected by the selection circuit using the motion detection signal as a switching signal. You. As a result, the image signal that has passed through the selection circuit is converted to the black 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 modulated at the boundary between the moving image and the still image is used as described above, the image at the boundary has a random shape in the same manner as described above. Since a region in which different encoding methods of the video encoding method and the moving image encoding method are mixed is formed, the temporal characteristics of the light emission in the PDP 10 do not become uniform with the switching of the encoding, and the encoding is switched. This makes the switching between the still image coding portion and the moving image coding portion smooth.

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

<Seventh Embodiment> 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 different from the image display device according to the third embodiment in that
Spatial modulation circuits 27 and 28 for performing spatial modulation on image signals from the still image encoding circuit 4 and the moving image encoding circuit 5 are provided. Hereinafter, differences from the third embodiment will be described.

FIG. 25 shows an example of an input image and a result of motion detection according to the present embodiment. Assuming that the triangular object 212 shown in FIG. 25A has moved to the right as shown in FIG. 25B, the moving part detected from the TV field before and after the input image signal is a black part shown in FIG. 213 On the other hand, the random number generation circuit 16 generates a random number from, for example, “−3” to “3”,
And 28, and 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 an image signal represented by a black portion 214 in FIG. 25D is obtained in the moving image portion.

When the image signal modulated at the boundary between the moving image and the still image is used as described above, the image at the boundary has a random shape in the same manner as described above. Since a region where a different encoding method is mixed with the moving image encoding method is formed, the temporal characteristics of the light emission in the PDP 10 do not change even when the encoding is switched, and the encoding is switched. This makes the switching between the still image coding portion and the moving image coding portion smooth.

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

In the third to seventh embodiments,
In particular, an image portion where the shock of encoding switching is conspicuous is limited to a non-edge portion where there is no or little change in the gradation value of the input image signal, and the encoding switching method in this portion is not linear. By doing so, it is possible to quickly switch the encoding method in the edge portion of the image while suppressing the coding switching shock in which the non-edge portion of the image is conspicuous,
This is more preferable because it is possible to perform encoding suitable for each region without deteriorating the average signal-to-noise ratio of the entire image.

It is also possible to combine Embodiment 2 with Embodiments 3 to 7 described above. In the second embodiment, the reference gradation value obtained by the display gradation magnification setting circuit 14 is set to be 1
Although the magnification “K value” of the maximum gradation value of the image of the frame (1 TV field) has been described as being a positive number, it is not limited to a positive number and may be a decimal number. FIG. 26 is a characteristic diagram showing the correlation between the coding pattern and the input image signal when K = 2.5 and the light emission luminance.

As shown in FIG. 26 (a), the reference encoding pattern (here, the luminance weight of each subfield is "1, 2, 3, 6, 10" in the order of time shown in FIG. 14 (a))
In the luminance weight in (1), a value obtained by multiplying the low luminance luminance 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 a frame having a corresponding K value is displayed using an encoding pattern in which is set as a luminance weight.

Specifically, the luminance weights “1, 2, 3, 6, 1”
0 "is 1, 1.5, 2.33, 2.5, 2.
It becomes 9. By setting the luminance weights in this way, it is possible not only to increase the luminance value to be displayed, but also to widen the dynamic range of the gradation values to be displayed. That is, as shown in FIGS. 26 (b) and (c), in the correlation between the input image signal and the light emission luminance, the luminance in the low gradation portion is maintained smaller than that of the input.
While maintaining the resolution in the low gradation value portion, the dynamic range can be expanded.

[0109]

As described above, the present invention has the following features.
An image display device in which a TV field is configured by arranging a plurality of subfields each having a luminance weight in chronological order, and a desired subfield is turned on to display an image of one TV field in multiple gradations. The weight of the subfield having the next largest luminance weight is 1
/ 2 is included.

Further, one TV field is composed of a plurality of subfields each having a luminance weight and arranged in chronological order.
The image field an image display apparatus for a multi-tone display, when arranging the subfields in ascending order of the luminance weight, the luminance weights of the subfields with small luminance weight i-th and the W _i, W ₁ + W wherein the luminance weight as ₁ + W is _{2 + ··· + W n <W} n + 1 a is n there is assigned.

Thus, when all selectable combinations of luminance values (gradation values) are rearranged in the order of luminance values (gradation values), a portion where the luminance (gradation) jumps can be generated. Since the ratio between the minimum luminance value and the representable maximum luminance value can be made larger than in the past, an image display with a wide dynamic range can be realized.

Further, according to the present invention, one TV field is constituted by arranging a plurality of subfields each having a luminance weight in chronological order, and a desired subfield is turned on to display an image of one TV field in multi-tone display. an image display apparatus which arranges the subfield 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 + ··· + W _n <
It is characterized in that luminance weights are assigned so that n which is W _{n + 1} and two or more i exist.

Thus, when all selectable combinations of luminance values (gradation values) are rearranged in the order of luminance values (gradation values), a portion where the luminance (gradation) jumps can be generated. Since the ratio between the minimum luminance value and the representable maximum luminance value can be made larger than in the past, an 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 higher the brightness value, the more the jump width of the brightness value is allowed, and further the maximum displayable brightness value is Can be set large.

Further, according to the present invention, one TV field is constituted by arranging a plurality of subfields each having a luminance weight in chronological order, and a desired subfield is turned on to display an image of one TV field in multi-tone display. An image display device configured to control a maximum display luminance according to characteristics of an input image signal, wherein a TV field including a plurality of subfields formed by a combination of predetermined luminance weights is used as a reference TV field. And the luminance weight of all the subfields in the encoding pattern used to display the display TV field to be currently displayed with respect to the sum of the luminance weights of all the subfields in the encoding pattern used when displaying the reference TV field When the ratio of the sum of
An encoding pattern used for displaying a field includes a subfield having a luminance weight calculated by multiplying a luminance weight of a predetermined subfield in the reference TV field by a coefficient equal to or less than K, and a predetermined subfield in the reference TV field. And a subfield having a luminance weight calculated by multiplying the luminance weight by a coefficient exceeding K.

Thus, when the maximum luminance value that can be displayed is controlled in accordance with the maximum gradation value of an image or the degree of distribution of a high gradation area, the minimum displayable luminance value is always kept small, The maximum brightness value can be controlled as needed. In general, if the maximum luminance value that can be displayed is increased more than necessary for an image including a relatively bright portion, the power consumption of a display device such as a plasma display panel, which has a high correlation between the light emission luminance and the power consumption, as a whole, is reduced. It is desirable to control the maximum luminance value that can be displayed according to the content of the image because there is a possibility that it will increase. When such control is performed, even if the maximum luminance value that can be displayed is particularly increased, for example, a subfield with a small luminance weight always keeps a relatively small value, while a subfield with a relatively large luminance weight Changes the luminance weight according to the desired maximum displayable luminance value, so that the ratio between the minimum luminance value and the maximum luminance value can be increased. The portion 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 constituted by arranging a plurality of subfields each having a luminance weight in chronological order, and the input image is selected from gradation values that can be expressed by combining the subfields. An image display apparatus that performs 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, and displays an image of a desired 1 TV field in multiple gradations. At this time, in a portion where the image signal at a switching boundary portion of the encoding method has a predetermined characteristic, encoding is performed so as to include a region where a plurality of encoding methods are mixed.

Further, according to the present invention, one TV field is constituted by arranging a plurality of subfields each having a luminance weight in chronological order, and the input image is selected from gradation values which 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 luminance weights according to the amount of motion of a signal to display a desired 1 TV field image in multiple gradations,
At the time of the encoding, in a portion where the image signal at the switching boundary 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 constituted by arranging a plurality of sub-fields each having a luminance weight in chronological order, and the input image is selected from gradation values which can be expressed by combining the sub-fields. An image display device that performs 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 to display a desired 1 TV field image in multiple gradations,
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, a signal for switching the encoding method is regularly shifted in a pixel direction. .

Further, according to the present invention, one TV field is constituted by arranging a plurality of sub-fields each having a luminance weight in chronological order, and the input image is selected from gradation values which can be expressed by combining the sub-fields. An image display device that performs 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 to display a desired 1 TV field image in multiple gradations,
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 shape at the switching boundary portion of the signal for switching the encoding method is set to a pixel interval as a 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 constituted by arranging a plurality of sub-fields each having a luminance weight in chronological order, and an input image is selected from gradation values which can be expressed by combining the sub-fields. An image display device that performs 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 to display a desired 1 TV field image in multiple gradations,
At the time of the encoding, a modulation signal having a cycle of at least a pixel interval is applied to an image signal at a switching boundary of the encoding method.

Further, according to the present invention, one TV field is constituted by arranging a plurality of sub-fields each having a luminance weight in chronological order, and an input image is selected from gradation values which can be expressed by combining the sub-fields. An image display device that performs 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 to display a desired 1 TV field image in multiple gradations,
At the time of the encoding, the image signal at a switching boundary of the encoding method is subjected to modulation for shifting a display position.

As a result, even if a switching shock occurs in an image portion whose coding method has been switched, the occurrence position can be dispersed, so that the switching shock can be reduced while suppressing the moving image false contour. it can.
This means that, for example, when the image encoding process is performed differently for the still image portion and the moving image portion, the transition to the switching between the encoding methods can be smoothly performed.

[Brief description of the drawings]

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

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

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

FIG. 5 is a block diagram illustrating 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 the subfield control circuit.

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

FIG. 9 is a diagram showing an operation method of the PDP.

FIGS. 10 (a), (b), and (c) are a characteristic diagram and a chart showing a correlation between a value of an input image signal and light emission luminance.

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

FIGS. 12 (a) to (e) are tables showing modes when switching the encoding in the subfield control circuit based on each K value (conventional one).

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

FIGS. 14 (a) to (e) are diagrams showing aspects of 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 a correlation between an input image signal and emission luminance as shown in (a) to (e) (of the present invention).

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

FIG. 21 is a diagram illustrating an encoding mode in each image encoding circuit.

FIG. 22 is a block diagram illustrating 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 illustrating 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 a correlation between an encoding pattern and an input image signal and emission luminance when K = 2.5.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 input image signal 2 inverse gamma correction circuit 3 addition circuit 4 still image coding circuit 5 moving image 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 generation circuit 17 Signal modulation circuit 18 Boundary detection circuit 19 Addition circuit 20 Random number generation circuit 21, 22, 23 Image encoding 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

Claims (22)

[Claims] 1. An image display device in which one TV field is constituted by arranging a plurality of subfields each having a luminance weight in chronological order, and a desired subfield is turned on to display an image of one TV field in multiple gradations. An image display device, comprising: a subfield whose luminance weight is set to be less than half the luminance weight of a subfield having the next highest luminance weight. 2. An image display device in which one TV field is constituted by arranging a plurality of subfields each having a luminance weight in chronological order, and a desired subfield is turned on to display an image of one TV field in multiple gradations. Wherein the subfields are arranged in ascending order of luminance weight, and the luminance weight of the subfield having the i-th smallest luminance weight is represented by W _i.
Where W ₁ + W ₁ + W ₂ +... + W _n <W _{n + 1}
An image display device, wherein a luminance weight is assigned so that the image exists. 3. An image display device in which one TV field is constituted by arranging a plurality of subfields each having a luminance weight in chronological order, and a desired subfield is turned on to display an image of one TV field in multiple gradations. Where the subfields are arranged in ascending order of luminance weight, and the luminance weight of the subfield having the jth smallest luminance weight is represented by W _j
Where W _i + W ₁ + W ₂ +... + W _n <W _{n + 1}
And an image display device, wherein luminance weights are assigned so that two or more i exist. 4. A 1TV field is constituted by arranging a plurality of subfields each having a luminance weight in chronological order. A desired subfield is turned on to display an image of the 1TV field in multiple gradations. An image display device configured to control a maximum luminance according to characteristics of an input image signal, wherein a TV field including a plurality of subfields formed by a combination of predetermined luminance weights is set as a reference TV field, The ratio of the sum of the luminance weights of all the subfields in the encoding pattern used to display the display TV field to be currently displayed to the sum of the luminance weights of all the subfields in the encoding pattern used when displaying the TV field Is K,
An encoding pattern used for displaying the display TV field includes a subfield having a luminance weight calculated by multiplying a luminance weight of a predetermined subfield in the reference TV field by a coefficient equal to or less than K, and a predetermined pattern in the reference TV field. And a subfield having a luminance weight calculated by multiplying the luminance weight of the subfield by a coefficient exceeding K. 5. The method according to claim 1, wherein the coefficient equal to or less than K and the coefficient exceeding K are coefficients set based on a rule defined in the order of magnitude of luminance weight of each subfield in the reference TV field. The image display device according to claim 4. 6. The coefficient set based on a rule defined in the order of magnitude of the degree weight is a coefficient that increases monotonically in accordance with the order of the magnitude of the luminance weight. Item 6. The image display device according to Item 5. 7. A coefficient set based on a rule defined by the order of magnitude of the luminance weight is an isometric coefficient according to the order of magnitude of the luminance weight. Item 6. The image display device according to Item 5. 8. The coefficient set based on a rule defined in the order of magnitude of the luminance weight is a coefficient that is isometric according to the order of the magnitude of the luminance weight. Item 6. The image display device according to Item 5. 9. A subfield having a luminance weight calculated by multiplying a coefficient equal to or smaller than K is a subfield fixed to a luminance weight multiplied by a settable minimum value among a plurality of possible values of the K value. The image display device according to claim 4, further comprising a field. 10. The approximate values of the ratios of the luminance weights of 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: 4:
9 "," 2: 6: 12 "and" 2: 6: 16 "and at least two of the coding patterns determined according to the characteristics of the desired input image signal. The image display device according to any one of claims 4 to 9, wherein the luminance weight of the sub-field is configured. 11. The sum of luminance weights of all subfields is expressed by S
When a gradation display corresponding to a value “R” of “0” or more and “S” or less is selected from each subfield and performed,
11. The gray scale display according to claim 1, wherein a combination of subfields is selected so that the sum of the luminance weights of the selected subfields is the sum of the luminance weights closest to the value "R". The image display device according to any one of the above. 12. The image display device according to claim 1, wherein a combination of luminance weights to be selected is controlled by an amount of motion of the image or an approximate value of the motion of the image. 13. A coding method in which the amount of motion of an image or the approximate value of the amount of motion of the image is large, wherein the increase in the gradation level of the input image signal and the temporal distribution of the luminance weight arrangement pattern have a monotonically increasing correlation. 13. The image display device according to claim 12, wherein the image display device is limited. 14. A 1TV field is configured by arranging a plurality of subfields each having a luminance weight in chronological order, and a motion amount 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 in accordance with the amount of motion by using a combination of different luminance weights according to the multi-gradation display of an image of a desired 1TV field. An image display device, characterized in that a portion having a predetermined characteristic in an image signal at a switching boundary portion of an encoding method is encoded so as to include a region where a plurality of encoding methods are mixed. 15. A 1TV field is composed of a plurality of subfields each having a luminance weight, which are arranged in chronological order, and a motion amount 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 in accordance with the amount of motion by using a combination of different luminance weights according to the multi-gradation display of an image of a desired 1TV field. An image display device characterized in that the signal for switching the encoding method is shifted irregularly in the pixel direction at a portion where the image signal at the switching boundary of the encoding method has a predetermined characteristic. 16. A TV field is composed of a plurality of sub-fields each having a luminance weight and arranged in chronological order, and a motion of an input image signal is selected from among gradation values that can be expressed by combining the sub-fields. An image display device that performs different encoding according to the amount of motion by using a combination of different luminance weights according to the amount and displays a multi-gradation image of a desired 1 TV field. An image display device characterized in that the signal for switching the encoding method is regularly shifted in the pixel direction at a portion where the image signal at the switching boundary of the encoding method has a predetermined characteristic. 17. A 1-TV field is composed of a plurality of sub-fields each having a luminance weight and arranged in chronological order, and a motion amount of an input image signal is selected from among gradation values that can be expressed by combining the sub-fields. An image display device that performs different encoding in accordance with the amount of motion by using a combination of different luminance weights according to the multi-gradation display of an image of a desired 1TV field. In a portion where the image signal at the switching boundary of the encoding method has a predetermined characteristic, the shape of the signal at the switching boundary of the switching of the encoding method includes a polygonal line having a pixel interval as a minimum unit as a main element. An image display device having a shape. 18. The image display device according to claim 17, wherein the shape including a polygonal line having a pixel interval as a minimum unit as a main element is a checkerboard shape. 19. The image according to claim 17, wherein the shape including a polygonal line having a pixel interval as a minimum unit as a main element is a shape obtained by randomly combining polygonal lines having a pixel interval as a minimum unit. Display device. 20. The image display according to claim 14, wherein the predetermined image portion of the portion where the image signal has a predetermined feature is a non-edge portion of the image signal. apparatus. 21. One TV field is configured by arranging a plurality of subfields each having a luminance weight in chronological order, and a motion amount of an input image signal is selected from among gradation values that can be expressed by combining the subfields. An image display device that performs different encoding in accordance with the amount of motion by using a combination of different luminance weights according to the multi-gradation display of an image of a desired 1TV field. An image display device, wherein a modulation signal having a cycle of at least a pixel interval is applied to an image signal at a switching boundary of the encoding method. 22. One TV field is configured by arranging a plurality of subfields each having a luminance weight in chronological order, and the motion amount of the input image signal is selected from among gradation values that can be expressed by combining the subfields. An image display device that performs different encoding in accordance with the amount of motion by using a combination of different luminance weights according to the multi-gradation display of an image of a desired 1TV field. An image display device, characterized in that an image signal at a switching boundary portion of the encoding method is subjected to modulation for shifting a display position.