WO2012098887A1 - Dispositif de visualisation d'image et procédé de commande pour dispositif de visualisation d'image - Google Patents

Dispositif de visualisation d'image et procédé de commande pour dispositif de visualisation d'image Download PDF

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Publication number
WO2012098887A1
WO2012098887A1 PCT/JP2012/000298 JP2012000298W WO2012098887A1 WO 2012098887 A1 WO2012098887 A1 WO 2012098887A1 JP 2012000298 W JP2012000298 W JP 2012000298W WO 2012098887 A1 WO2012098887 A1 WO 2012098887A1
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Prior art keywords
code
subfield
gradation
image signal
pixel
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PCT/JP2012/000298
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English (en)
Japanese (ja)
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広史 本田
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パナソニック株式会社
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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/2003—Display of colours
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/28—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using luminous gas-discharge panels, e.g. plasma panels
    • G09G3/288—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using luminous gas-discharge panels, e.g. plasma panels using AC panels
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0242—Compensation of deficiencies in the appearance of colours
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2360/00—Aspects of the architecture of display systems
    • G09G2360/16—Calculation or use of calculated indices related to luminance levels in display data
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/2007—Display of intermediate tones
    • G09G3/2044—Display of intermediate tones using dithering
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/2007—Display of intermediate tones
    • G09G3/2059—Display of intermediate tones using error diffusion

Definitions

  • the present invention relates to an image display device that displays an image in an image display region by combining binary control of light emission and non-light emission in a light emitting element that constitutes a pixel, and a driving method of the image display device.
  • a plasma display panel (hereinafter abbreviated as “panel”) is a typical image display device that displays an image in an image display area by combining binary control of light emission and non-light emission in a light emitting element constituting a pixel. is there.
  • a large number of discharge cells which are light-emitting elements constituting pixels, are formed between a front substrate and a rear substrate that are arranged to face each other.
  • a plurality of pairs of display electrodes composed of a pair of scan electrodes and sustain electrodes are formed on the front glass substrate in parallel with each other.
  • a dielectric layer and a protective layer are formed so as to cover the display electrode pairs.
  • the back substrate has a plurality of parallel data electrodes formed on the glass substrate on the back side, a dielectric layer is formed so as to cover the data electrodes, and a plurality of barrier ribs are formed thereon in parallel with the data electrodes. ing. And the fluorescent substance layer is formed in the surface of a dielectric material layer, and the side surface of a partition.
  • the front substrate and the rear substrate are arranged opposite to each other and sealed so that the display electrode pair and the data electrode are three-dimensionally crossed.
  • a discharge gas containing xenon at a partial pressure ratio of 5% is sealed, and a discharge cell is formed in a portion where the display electrode pair and the data electrode face each other.
  • ultraviolet rays are generated by gas discharge in each discharge cell, and the phosphors of each color of red (R), green (G) and blue (B) are excited and emitted by the ultraviolet rays. Display an image.
  • a subfield method is generally used as a method for displaying an image in an image display region by combining binary control of light emission and non-light emission in a light emitting element.
  • each discharge cell In the subfield method, one field is divided into a plurality of subfields having different emission luminances.
  • each discharge cell light emission / non-light emission of each subfield is controlled by a combination according to a desired gradation value.
  • each discharge cell emits light with the emission luminance of one field set to a desired gradation value, and an image composed of various combinations of gradation values is displayed in the image display area of the panel.
  • each subfield has an address period and a sustain period.
  • the scan pulse is sequentially applied to the scan electrodes, and the address pulse is selectively applied to the data electrodes based on the image signal to be displayed.
  • an address discharge is generated between the scan electrode and the data electrode of the discharge cell to emit light, and a wall charge is formed in the discharge cell (hereinafter, these operations are also collectively referred to as “address”). ).
  • the number of sustain pulses based on the gradation weights determined for each subfield is alternately applied to the display electrode pairs composed of the scan electrodes and the sustain electrodes.
  • a sustain discharge is generated in the discharge cell that has generated the address discharge, and the phosphor layer of the discharge cell emits light (hereinafter referred to as “lighting” that the discharge cell emits light by the sustain discharge, and “non-emitting”). Also written as “lit”.)
  • each discharge cell is made to emit light with the luminance according to the gradation weight.
  • each discharge cell of the panel is caused to emit light with a luminance corresponding to the gradation value of the image signal, and an image is displayed in the image display area of the panel.
  • the plasma display device has an image signal processing circuit.
  • the image signal processing circuit converts an image signal (hereinafter simply referred to as “image signal”) input to the plasma display device into a subfield code indicating lighting / non-lighting for each subfield in each discharge cell.
  • the image signal processing circuit has a conversion table composed of a plurality of subfield codes.
  • one subfield code is associated with one gradation value. That is, when one gradation value is input, the conversion table outputs one subfield code associated with the gradation value.
  • the conversion table is stored in a semiconductor storage element such as a ROM and provided in the image signal processing circuit. Then, using the conversion table, the image signal processing circuit converts each gradation value of the image signal into a subfield code (data indicating light emission / non-light emission for each subfield) corresponding to each gradation value. Output to the circuit.
  • the number of gradation values that can be displayed on the panel is determined by the number of subfield codes constituting the conversion table. If the number of subfield codes constituting the conversion table is large, the number of gradation values that can be displayed on the panel increases, and if the number of subfield codes constituting the conversion table is small, the number of gradation values that can be displayed on the panel. Decrease.
  • the number of gradation values that can be displayed on the panel is related to the power consumption of the plasma display device, and the number of gradation values that can be displayed on the panel is relatively reduced when the power consumption is reduced. Therefore, the subfield codes constituting the conversion table are generally determined in consideration of the power consumption of the plasma display device, the smoothness of the image that can be displayed on the panel, and the like.
  • the gradation values that cannot be displayed on the panel increase. For example, if the conversion table includes the subfield code of gradation value “7” and gradation value “9” and does not include the subfield code of gradation value “8”, the gradation value “8” is displayed on the panel. "Cannot be displayed. However, gradation values that cannot be displayed on the panel can be displayed on the panel in a pseudo manner by using a generally known method such as a dither method or an error diffusion method.
  • this moving image pseudo contour changes according to the number of subfield codes constituting the conversion table, and when the number of subfield codes constituting the conversion table increases, the moving image pseudo contour is likely to occur. .
  • the plasma display device it is desirable to display the image with a smooth gradation change by increasing the gradation values that can be displayed on the panel as much as possible, while reducing the moving image pseudo contour as much as possible.
  • the plasma display device includes a plurality of conversion tables having different numbers and types of subfield codes constituting the conversion table, and the plurality of conversion tables. Has been disclosed (for example, see Patent Document 1).
  • a plasma display device includes a plurality of conversion tables. Then, a minimum value and an average value of the image signal are obtained, and a threshold value is calculated from the minimum value and the average value. Then, one conversion table is selected from a plurality of conversion tables based on this threshold value. Then, the image signal is converted into a subfield code based on the selected conversion table.
  • the number of conversion tables to be provided in the plasma display device is very large as compared with the conventional plasma display device. For this reason, it is difficult to configure an image signal processing circuit having such a large number of conversion tables and selecting an optimum one from a large number of conversion tables according to various conditions. It is coming.
  • the plasma display device includes a plurality of electrode driving circuits for driving each electrode, and the driving voltage waveforms necessary for displaying an image on the panel are respectively displayed using the plurality of electrode driving circuits. Apply to electrode.
  • the plurality of electrode drive circuits include a data electrode drive circuit for driving the data electrodes.
  • the data electrode driving circuit applies a write pulse for a write operation to each of the plurality of data electrodes according to the image signal. Therefore, the data electrode driving circuit is generally configured using a dedicated integrated circuit (IC) for generating an address pulse.
  • IC integrated circuit
  • the data electrode viewed from the data electrode driving circuit is a capacitive load having a stray capacitance between adjacent data electrodes, a stray capacitance between the scan electrodes, and a stray capacitance between the sustain electrodes. Therefore, in order to apply a drive voltage waveform to the data electrode, the data electrode drive circuit must charge and discharge this capacitor, and power consumption for that purpose is required.
  • a plurality of subfields having gradation weights constitute one field, and each of the plurality of subfields is expressed using a subfield code indicating a combination of light emission and non-light emission in each of the plurality of subfields.
  • This is an image display device that controls the light emission and non-light emission, displays a gradation value based on an image signal on each of a plurality of pixels constituting the image display area, and displays an image in the image display area.
  • This image display device includes an image signal processing circuit that outputs a display code that is a subfield code for displaying a gradation value based on an image signal on a pixel.
  • the image signal processing circuit calculates the difference level of luminance by calculating the difference of the red image signal, the difference of the green image signal, and the difference of the blue image signal between the pixels adjacent in the direction in which the data electrode extends.
  • an allowable noise calculation unit that calculates an allowable noise level of luminance based on the difference level of luminance, and a red that outputs a subfield code for displaying a gradation value of a red image signal on a pixel as a red display code.
  • Image signal processing unit a green image signal processing unit that outputs a subfield code for displaying a gradation value of a green image signal on a pixel as a green display code, and a gradation value of a blue image signal
  • a blue image signal processing unit that outputs a sub-field code for display on a pixel as a blue display code.
  • the red image signal processing unit calculates a red threshold value from the allowable noise level of luminance and the red luminance conversion coefficient, and indicates that a subfield having a gradation weight smaller than the red threshold value does not emit light.
  • a red display code is generated using the prohibited subfield code.
  • the green image signal processing unit calculates a green threshold from the allowable noise level of luminance and the green luminance conversion coefficient, and prohibits a subfield having a gradation weight smaller than the green threshold from not emitting light.
  • a green display code is generated using the subfield code.
  • the blue image signal processing unit calculates a blue threshold value from the allowable noise level of luminance and the blue luminance conversion coefficient, and prohibits a subfield having a gradation weight smaller than the blue threshold value from not emitting light.
  • a blue display code is generated using the subfield code.
  • the conversion from the image signal to the subfield code can be performed by calculation using the calculation circuit. Therefore, even in an image display device that needs to cope with high functionality and multi-function, it is not necessary to provide a huge number of conversion tables for converting image signals into subfield codes. That is, it is not necessary to configure the image signal processing circuit so as to select an optimal one from a vast number of conversion tables according to various conditions. Furthermore, power consumption can be suppressed while preventing deterioration in image display quality in the image display device.
  • the difference between the red image signals described above is calculated between the target pixel and a pixel adjacent to one side of the target pixel in the direction in which the data electrode extends.
  • the absolute value of the difference between the image signals and the absolute value of the difference between the red image signal calculated between the target pixel and a pixel adjacent to the other side of the target pixel in the direction in which the data electrode extends are smaller. To be.
  • the absolute value of the difference between the green image signals calculated between the pixel of interest and the pixel adjacent to one side of the pixel of interest in the direction in which the data electrode extends and The absolute value of the difference between the green image signals calculated between the pixel of interest and the pixel adjacent to the other side of the pixel of interest in the direction in which the data electrode extends is the smaller one.
  • the absolute value of the difference between the blue image signals calculated between the pixel of interest and the pixel adjacent to one side of the pixel of interest in the direction in which the data electrode extends and The absolute value of the difference between the blue image signals calculated between the pixel of interest and the pixel adjacent to the other side of the pixel of interest in the direction in which the data electrode extends is the smaller one.
  • each of the red image signal processing unit, the green image signal processing unit, and the blue image signal processing unit includes a base code generation unit, a rule generation unit, a rule addition unit, And an upper and lower code generation unit and a display code selection unit.
  • the base code generation unit has a gradation value that is larger than the gradation value of the image signal at the target pixel and has the closest gradation value to the gradation value of the image signal at the target pixel, from among a plurality of basic subfield codes.
  • the field code is selected as the upper gradation base code.
  • the rule generation unit generates a first rule for generating a new subfield code by changing the light-emitting subfield in the upper gradation base code to a non-light-emitting subfield based on the image signal at the target pixel.
  • the rule adding unit calculates a threshold value from the allowable noise level of luminance and the luminance conversion coefficient, and generates a second rule that prohibits subfields having gradation weights smaller than the threshold value from not emitting light.
  • the upper / lower code generation unit applies a value greater than the gradation value of the image signal at the target pixel from among the subfield codes newly generated by applying the first rule and the second rule to the upper gradation base code.
  • the subfield code having the gradation value closest to the gradation value of the image signal at the target pixel is selected as the upper gradation code, and the gradation of the image signal at the attention pixel is equal to or lower than the gradation value of the image signal at the target pixel.
  • the subfield code having the gradation value closest to the value is selected as the lower gradation code.
  • the display code selection unit calculates a gradation value to be displayed on the target pixel by adding a predetermined value to the gradation value of the image signal in the target pixel, and sets the target pixel of the upper gradation code and the lower gradation code. One having a gradation value closer to the gradation value to be displayed is selected as a display code.
  • the plurality of basic subfield codes described above are all subfields having the largest gradation weight among the subfields that emit light, and all having a gradation weight smaller than that subfield.
  • This is a sub-field code in which the sub-field emits light.
  • the predetermined value described above is an error generated by error diffusion processing and a dither value generated by dither processing.
  • the present invention also comprises a plurality of subfields using a subfield code indicating a combination of light emission and non-light emission in each of the plurality of subfields, with a plurality of subfields having gradation weights defined.
  • Method for driving an image display apparatus for controlling each light emission and non-light emission of each of the image display, displaying a gradation value based on an image signal on each of a plurality of pixels constituting the image display area, and displaying an image on the image display area It calculates a difference level of luminance by calculating a difference of a red image signal, a difference of a green image signal, and a difference of a blue image signal, respectively, between pixels adjacent in the direction in which the data electrode extends.
  • a threshold value is calculated from the threshold value and the luminance conversion coefficient, and a second rule for prohibiting the subfield having a gradation weight smaller than the threshold value from emitting no light is included in the upper gradation base code.
  • the level closest to the gradation value of the image signal at the target pixel is larger than the gradation value of the image signal at the target pixel.
  • Selecting a lower gradation code calculating a gradation value to be displayed on the target pixel by adding a predetermined value to the gradation value of the image signal in the target pixel;
  • a display which is a subfield code for displaying a gradation value based on an image signal on a target pixel, which has a gradation value closer to the gradation value to be displayed on the target pixel, of the gradation code and the lower gradation code. Selecting as a code.
  • the conversion from the image signal to the subfield code can be performed by calculation using the calculation circuit. Therefore, even in an image display device that needs to cope with high functionality and multi-function, it is not necessary to provide a huge number of conversion tables for converting image signals into subfield codes. That is, it is not necessary to configure the image signal processing circuit so as to select an optimal one from a vast number of conversion tables according to various conditions. Furthermore, power consumption can be suppressed while preventing deterioration in image display quality in the image display device.
  • the difference between the red image signals described above is calculated between the pixel of interest and a pixel adjacent to one side of the pixel of interest in the direction in which the data electrode extends. Either the absolute value of the difference between the red image signals and the absolute value of the difference between the red image signals calculated between the pixel of interest and a pixel adjacent to the other side of the pixel of interest in the direction in which the data electrode extends Or the smaller one.
  • the absolute value of the difference between the green image signals calculated between the pixel of interest and the pixel adjacent to one side of the pixel of interest in the direction in which the data electrode extends and The absolute value of the difference between the green image signals calculated between the pixel of interest and the pixel adjacent to the other side of the pixel of interest in the direction in which the data electrode extends is the smaller one.
  • the absolute value of the difference between the blue image signals calculated between the pixel of interest and the pixel adjacent to one side of the pixel of interest in the direction in which the data electrode extends and The absolute value of the difference between the blue image signals calculated between the pixel of interest and the pixel adjacent to the other side of the pixel of interest in the direction in which the data electrode extends is the smaller one.
  • FIG. 1 is an exploded perspective view showing a structure of a panel used in an image display apparatus according to an embodiment of the present invention.
  • FIG. 2 is an electrode array diagram of a panel used in the image display apparatus according to the embodiment of the present invention.
  • FIG. 3 is a diagram schematically showing drive voltage waveforms applied to the respective electrodes of the panel used in the image display device according to the embodiment of the present invention.
  • FIG. 4 is a diagram showing an example of a code set when one field is composed of eight subfields.
  • FIG. 5 is a diagram schematically showing an example of a circuit block constituting the image display device according to the embodiment of the present invention.
  • FIG. 1 is an exploded perspective view showing a structure of a panel used in an image display apparatus according to an embodiment of the present invention.
  • FIG. 2 is an electrode array diagram of a panel used in the image display apparatus according to the embodiment of the present invention.
  • FIG. 3 is a diagram schematically showing drive voltage waveforms applied to the respective electrodes of the panel used
  • FIG. 6 is a diagram schematically showing an example of a circuit block constituting the image signal processing circuit of the image display apparatus according to the embodiment of the present invention.
  • FIG. 7 is a diagram schematically showing an example of a circuit block constituting the R signal processing unit of the image display apparatus according to the embodiment of the present invention.
  • FIG. 8A is a diagram illustrating an example of a base code set used in the image display device according to the embodiment of the present invention.
  • FIG. 8B is a diagram showing another example of the base code set used in the image display device according to the embodiment of the present invention.
  • FIG. 8C is a diagram illustrating another example of the base code set used in the image display device according to the embodiment of the present invention.
  • FIG. 8A is a diagram illustrating an example of a base code set used in the image display device according to the embodiment of the present invention.
  • FIG. 8B is a diagram showing another example of the base code set used in the image display device according to the embodiment of the present invention.
  • FIG. 8C
  • FIG. 9A is a diagram illustrating an example of an intermediate code set generated by the intermediate code generation unit of the image display device according to the embodiment of the present invention.
  • FIG. 9B is a diagram showing another example of the intermediate code set generated by the intermediate code generation unit of the image display device according to the embodiment of the present invention.
  • FIG. 9C is a diagram showing another example of the intermediate code set generated by the intermediate code generation unit of the image display device according to the embodiment of the present invention.
  • FIG. 10A is a diagram showing an example of a dither pattern used in the image display device in one embodiment of the present invention.
  • FIG. 10B is a diagram showing another example of the dither pattern used in the image display device according to the embodiment of the present invention.
  • FIG. 10A is a diagram showing an example of a dither pattern used in the image display device in one embodiment of the present invention.
  • FIG. 10B is a diagram showing another example of the dither pattern used in the image display device according to the embodiment of the present invention.
  • FIG. 11 is a diagram showing the error diffusion coefficient of the error diffusion unit of the image display device according to the embodiment of the present invention.
  • FIG. 12 is a flowchart showing the operation of the image signal processing circuit of the image display device according to the embodiment of the present invention.
  • FIG. 13A shows an intermediate code generated in the intermediate code generation unit based on the first rule generated in the rule generation unit of the image display device and the second rule generated in the rule addition unit in the embodiment of the present invention. It is a figure which shows an example of a code set.
  • FIG. 13B shows an intermediate code generated in the intermediate code generation unit based on the first rule generated in the rule generation unit of the image display device and the second rule generated in the rule addition unit according to the embodiment of the present invention. It is a figure which shows an example of a code set.
  • FIG. 1 is an exploded perspective view showing the structure of panel 10 used in the image display apparatus according to the embodiment of the present invention.
  • a plurality of display electrode pairs 14 each including a scanning electrode 12 and a sustaining electrode 13 are formed on a glass front substrate 11.
  • a dielectric layer 15 is formed so as to cover the scan electrode 12 and the sustain electrode 13, and a protective layer 16 is formed on the dielectric layer 15.
  • This protective layer 16 has been used as a panel material in order to lower the discharge start voltage in the discharge cell, and has a large secondary electron emission coefficient and durability when neon (Ne) and xenon (Xe) gas is sealed. It is made of a material mainly composed of magnesium oxide (MgO).
  • the protective layer 16 may be composed of a single layer or may be composed of a plurality of layers. Moreover, the structure which particle
  • a plurality of data electrodes 22 are formed on the rear substrate 21, a dielectric layer 23 is formed so as to cover the data electrodes 22, and a grid-like partition wall 24 is further formed thereon.
  • a phosphor layer 25R that emits red (R)
  • a phosphor layer 25G that emits green (G)
  • a phosphor layer 25B that emits blue (B).
  • the phosphor layer 25R, the phosphor layer 25G, and the phosphor layer 25B are collectively referred to as a phosphor layer 25.
  • the front substrate 11 and the rear substrate 21 are arranged to face each other so that the display electrode pair 14 and the data electrode 22 intersect each other with a minute space therebetween, and a discharge space is provided in the gap between the front substrate 11 and the rear substrate 21.
  • the outer peripheral part is sealed with sealing materials, such as glass frit.
  • sealing materials such as glass frit.
  • a mixed gas of neon and xenon is sealed in the discharge space as a discharge gas.
  • the discharge space is partitioned into a plurality of sections by the barrier ribs 24, and discharge cells, which are light-emitting elements constituting the pixels, are formed at the intersections between the display electrode pairs 14 and the data electrodes 22.
  • one pixel is composed of three consecutive discharge cells arranged in the direction in which the display electrode pair 14 extends.
  • the three discharge cells are a discharge cell having a phosphor layer 25R and emitting red (R) (red discharge cell), and a discharge cell having a phosphor layer 25G and emitting green (G) (green). And a discharge cell having a phosphor layer 25B and emitting blue (B) light (blue discharge cell).
  • the structure of the panel 10 is not limited to the above-described structure, and may be, for example, provided with a stripe-shaped partition wall.
  • FIG. 2 is an electrode array diagram of panel 10 used in the plasma display device according to one embodiment of the present invention.
  • the panel 10 includes n scan electrodes SC1 to SCn (scan electrode 12 in FIG. 1) extended in the horizontal direction (row direction and line direction) and n sustain electrodes SU1 to SUn (FIG. 1).
  • the sustain electrodes 13) are arranged, and m data electrodes D1 to Dm (data electrodes 22 in FIG. 1) extending in the vertical direction (column direction) are arranged.
  • m discharge cells are formed on one pair of display electrodes 14 and m / 3 pixels are formed.
  • pixels continuously arranged on one data electrode 22 are referred to as “vertically continuous pixels” or “pixels adjacent in the vertical direction”.
  • the “vertical direction” described in the following description refers to an array of pixels continuously arranged on one data electrode 22, and is “pixels on one pixel of the target pixel” and “target pixel”.
  • the “pixel below one pixel” means a pixel adjacent on one data electrode 22.
  • the plasma display device in the present embodiment drives the panel 10 by the subfield method.
  • the subfield method one field of an image signal is divided into a plurality of subfields on the time axis, and a gradation weight is set for each subfield. Therefore, each field has a plurality of subfields having different gradation weights.
  • Each subfield has an initialization period, an address period, and a sustain period. Based on the image signal, light emission / non-light emission of each discharge cell is controlled for each subfield. That is, a plurality of gradations based on the image signal are displayed on the panel 10 by combining the light-emitting subfield and the non-light-emitting subfield based on the image signal.
  • an initializing operation is performed in which initializing discharge is generated in the discharge cells and wall charges necessary for the address discharge in the subsequent address period are formed on each electrode.
  • Initialization operation includes “forced initialization operation” that forcibly generates an initializing discharge in all discharge cells regardless of the operation of the immediately preceding subfield and an addressing discharge that occurs in the addressing period of the immediately preceding subfield.
  • the forced initializing operation the rising ramp waveform voltage and the falling ramp waveform voltage are applied to the scan electrode 12 to generate an initializing discharge in the discharge cell.
  • the forced initializing operation is performed in all discharge cells in the initializing period of one subfield, and all the discharge cells are selected in the initializing period of the other subfield. Perform initialization.
  • force initialization period the initialization period in which the forced initialization operation is performed
  • subfield having the forced initialization period is referred to as “forced initialization subfield”.
  • An initialization period for performing the selective initialization operation is referred to as a “selective initialization period”
  • a subfield having the selective initialization period is referred to as a “selective initialization subfield”.
  • subfield SF1 is a forced initialization subfield
  • the other subfields are selected initialization subfields.
  • the present invention is not limited to the above-described subfields as subfields for forced initialization subfields and subfields for selective initialization subfields.
  • the structure which switches a subfield structure based on an image signal etc. may be sufficient.
  • a scan pulse is applied to the scan electrode 12 and an address pulse is selectively applied to the data electrode 22 to selectively generate an address discharge in the discharge cells to emit light. Then, an address operation is performed to form wall charges in the discharge cells for generating a sustain discharge in the subsequent sustain period.
  • sustain pulses of the number obtained by multiplying the gradation weight set in each subfield by a predetermined proportional constant are alternately applied to the scan electrode 12 and the sustain electrode 13 to generate an address discharge in the immediately preceding address period.
  • a sustain discharge is generated in the discharged discharge cell, and a sustain operation for emitting light from the discharge cell is performed.
  • This proportionality constant is a luminance multiple.
  • the gradation weight represents the ratio of the magnitude of the luminance displayed in each subfield, and the number of sustain pulses corresponding to the gradation weight is generated in the sustain period in each subfield. Therefore, for example, the subfield with the gradation weight “8” emits light with a luminance about eight times that of the subfield with the gradation weight “1”, and about four times as high as the subfield with the gradation weight “2”. Emits light. Therefore, for example, if the subfield with the gradation weight “8” and the subfield with the gradation weight “2” are emitted, the discharge cell can emit light with a luminance corresponding to the gradation value “10”.
  • each discharge cell emits light with various gradation values by selectively emitting light in each subfield by controlling light emission / non-light emission of each discharge cell for each subfield in a combination according to the image signal. That is, a gradation value corresponding to an image signal can be displayed on each discharge cell, and an image based on the image signal can be displayed on the panel 10.
  • one pixel includes three consecutive discharge cells arranged in the direction in which the display electrode pair 14 extends, that is, a red discharge cell, a green discharge cell, and a blue discharge.
  • a red discharge cell is also referred to as a “red pixel”, a green discharge cell as a “green pixel”, and a blue discharge cell as a “blue pixel”.
  • FIG. 3 is a diagram schematically showing drive voltage waveforms applied to the respective electrodes of panel 10 used in the plasma display device according to one embodiment of the present invention.
  • FIG. 3 shows data electrode D1 to data electrode Dm, scan electrode SC1 that performs the address operation first in the address period, scan electrode SCn that performs the address operation last in the address period (for example, scan electrode SC1080), sustain electrode SU1 to The drive voltage waveform applied to each of the sustain electrodes SUn is shown.
  • Scan electrode SCi, sustain electrode SUi, and data electrode Dk in the following represent electrodes selected based on image data (data indicating light emission / non-light emission for each subfield) from among the electrodes.
  • FIG. 3 shows a subfield SF1 that is a forced initialization subfield, and a subfield SF2 and a subfield SF3 that are selective initialization subfields.
  • the subfield SF1, the subfield SF2, and the subfield SF3 have different waveform shapes of the drive voltage applied to the scan electrode 12 in the initialization period.
  • each subfield except subfield SF1 is a selective initialization subfield, and substantially the same drive voltage waveform in each period except the number of sustain pulses. Is generated.
  • the voltage 0 (V) is applied to the data electrode D1 to the data electrode Dm and the sustain electrode SU1 to the sustain electrode SUn.
  • a voltage Vi1 is applied to scan electrode SC1 through scan electrode SCn after voltage 0 (V) is applied, and a ramp waveform voltage that gradually rises from voltage Vi1 to voltage Vi2 (hereinafter referred to as an “upward ramp waveform voltage”). ) Is applied.
  • voltage Vi1 is set to a voltage lower than the discharge start voltage for sustain electrode SU1 to sustain electrode SUn
  • voltage Vi2 is set to a voltage exceeding the discharge start voltage for sustain electrode SU1 to sustain electrode SUn.
  • the wall voltage on the electrode represents a voltage generated by wall charges accumulated on the dielectric layer covering the electrode, the protective layer, the phosphor layer, and the like.
  • the positive voltage Ve is applied to the sustain electrodes SU1 to SUn, and the voltage 0 (V) is applied to the data electrodes D1 to Dm.
  • a scan waveform SC1 to scan electrode SCn are applied with a ramp waveform voltage that gently falls from voltage Vi3 to negative voltage Vi4 (hereinafter referred to as “down ramp waveform voltage”).
  • Voltage Vi3 is set to a voltage lower than the discharge start voltage with respect to sustain electrode SU1 through sustain electrode SUn
  • voltage Vi4 is set to a voltage exceeding the discharge start voltage with respect to sustain electrode SU1 through sustain electrode SUn.
  • the above voltage waveform is a forced initializing waveform that generates an initializing discharge in the discharge cell regardless of the operation of the immediately preceding subfield.
  • the operation for applying the forced initialization waveform to the scan electrode 12 is the forced initialization operation.
  • the forced initialization operation in the initialization period Ti1 of the forced initialization subfield ends.
  • initializing discharge is forcibly generated in all the discharge cells in the image display area of the panel 10.
  • voltage Ve is applied to sustain electrode SU1 through sustain electrode SUn
  • voltage 0 (V) is applied to data electrode D1 through data electrode Dm
  • scan electrode SC1 through scan electrode SCn are applied. Applies a voltage Vc.
  • a negative scan pulse having a negative voltage Va is applied to the first (first row) scan electrode SC1 in terms of arrangement.
  • a positive address pulse of a positive voltage Vd is applied to the data electrode Dk of the discharge cell that should emit light in the first row of the data electrodes D1 to Dm.
  • sustain electrode SU1 since voltage Ve is applied to sustain electrode SU1 through sustain electrode SUn, sustain electrode SU1 in a region intersecting data electrode Dk is induced by a discharge generated between data electrode Dk and scan electrode SC1. Discharge also occurs between scan electrode SC1 and scan electrode SC1. Thus, address discharge is generated in the discharge cells (discharge cells to emit light) to which the scan pulse voltage Va and the address pulse voltage Vd are simultaneously applied.
  • a positive wall voltage is accumulated on the scan electrode SC1
  • a negative wall voltage is accumulated on the sustain electrode SU1
  • a negative wall voltage is also accumulated on the data electrode Dk.
  • the address operation in the discharge cells in the first row is completed.
  • the discharge cell having the data electrode Dh to which the address pulse is not applied the data electrode Dh is the data electrode D1 to the data electrode Dm excluding the data electrode Dk
  • the intersection of the data electrode Dh and the scan electrode SC1 Since the voltage of the portion does not exceed the discharge start voltage, the address discharge does not occur, and the wall voltage after the end of the initialization period Ti1 is maintained.
  • a scan pulse of the voltage Va is applied to the second (second row) scan electrode SC2 from the top, and the voltage Vd is applied to the data electrode Dk corresponding to the discharge cell to emit light in the second row. Apply the write pulse.
  • address discharge occurs in the discharge cells in the second row to which the scan pulse and address pulse are simultaneously applied.
  • the address operation in the discharge cells in the second row is performed.
  • voltage Ve applied to sustain electrode SU1 through sustain electrode SUn in the second half of initialization period Ti1 and voltage Ve applied to sustain electrode SU1 through sustain electrode SUn in address period Tw1 may have different voltage values. .
  • the voltage 0 (V) is applied to the sustain electrodes SU1 to SUn. Then, sustain pulse of positive voltage Vs is applied to scan electrode SC1 through scan electrode SCn.
  • the voltage difference between the scan electrode SCi and the sustain electrode SUi exceeds the discharge start voltage, and is maintained between the scan electrode SCi and the sustain electrode SUi. Discharge occurs.
  • the phosphor layer 25 of the discharge cell in which the sustain discharge has occurred emits light by the ultraviolet rays generated by the sustain discharge.
  • a negative wall voltage is accumulated on scan electrode SCi
  • a positive wall voltage is accumulated on sustain electrode SUi.
  • a positive wall voltage is also accumulated on the data electrode Dk.
  • the sustain discharge does not occur in the discharge cells in which the address discharge has not occurred in the address period Tw1.
  • the sustain pulses of the number obtained by multiplying the gradation weight by a predetermined luminance multiple are alternately applied to scan electrode SC1 through scan electrode SCn and sustain electrode SU1 through sustain electrode SUn.
  • the discharge cells that have generated the address discharge in the address period generate the sustain discharges the number of times corresponding to the gradation weight, and emit light with the luminance corresponding to the gradation weight.
  • scan electrode SC1 to scan are performed while voltage 0 (V) is applied to sustain electrode SU1 to sustain electrode SUn and data electrode D1 to data electrode Dm.
  • An upward ramp waveform voltage that gradually rises from voltage 0 (V) to voltage Vr is applied to electrode SCn.
  • the sustain of the discharge cell that has generated the sustain discharge is maintained while the rising ramp waveform voltage applied to scan electrode SC1 through scan electrode SCn exceeds the discharge start voltage.
  • a weak discharge (erase discharge) is continuously generated between the electrode SUi and the scan electrode SCi.
  • the charged particles generated by this weak discharge are accumulated as wall charges on the sustain electrode SUi and the scan electrode SCi so as to reduce the voltage difference between the sustain electrode SUi and the scan electrode SCi.
  • the wall voltage on scan electrode SCi and the wall voltage on sustain electrode SUi are weakened while the positive wall voltage on data electrode Dk remains.
  • unnecessary wall charges in the discharge cell are erased.
  • the voltage 0 (V) is applied to the data electrodes D1 to Dm, and the positive voltage Ve is applied to the sustain electrodes SU1 to SUn.
  • Scan electrode SC1 to scan electrode SCn decrease from a voltage lower than the discharge start voltage (for example, voltage 0 (V)) toward negative voltage Vi4 at the same gradient as the downward ramp waveform voltage generated in initialization period Ti1. Apply a downward ramp waveform voltage.
  • the voltage Vi4 is set to a voltage exceeding the discharge start voltage.
  • the negative wall voltage on scan electrode SCi and the positive wall voltage on sustain electrode SUi are weakened.
  • an excessive portion of the positive wall voltage on the data electrode Dk is discharged.
  • the wall voltage in the discharge cell is adjusted to a wall voltage suitable for the address operation in the address period Tw2.
  • the voltage waveform described above is a selective initialization waveform in which an initializing discharge is selectively generated in a discharge cell that has performed an address operation in the address period (here, address period Tw1) of the immediately preceding subfield.
  • the operation of applying the selective initialization waveform to the scan electrode 12 is the selective initialization operation.
  • the same drive voltage waveform as that in the address period Tw1 of the subfield SF1 is applied to each electrode.
  • the number of sustain pulses corresponding to the gradation weights are alternately applied to the scan electrodes SC1 to SCn and the sustain electrodes SU1 to SUn.
  • each subfield after subfield SF3 the same drive voltage waveform as in subfield SF2 is applied to each electrode except for the number of sustain pulses generated in the sustain period.
  • Voltage Vc ⁇ 60 (V)
  • voltage Va ⁇ 200 (V)
  • voltage Vs 200 (V)
  • voltage Vr 200 (V)
  • voltage Ve 130 (V)
  • voltage Vd 70 (V)
  • the gradient of the rising ramp waveform voltage generated in the initialization period Ti1 is about 1.3 V / ⁇ sec
  • the gradient of the rising ramp waveform voltage generated in each sustain period is about 10 V / ⁇ sec.
  • the gradient of the generated downward ramp waveform voltage is about ⁇ 1.5 V / ⁇ sec.
  • the specific numerical values such as the voltage value and the gradient described above are merely examples, and the present invention is not limited to the numerical values described above for each voltage value and the gradient.
  • Each voltage value, gradient, and the like are preferably set optimally based on the discharge characteristics of the panel and the specifications of the plasma display device.
  • subfield SF1 is a forced initialization subfield for performing a forced initialization operation
  • other subfields are a selective initialization subfield for performing a selective initialization operation
  • the present invention is not limited to this configuration.
  • the subfield SF1 may be a selective initialization subfield and other subfields may be forced initialization subfields, or a plurality of subfields may be forced initialization subfields.
  • one field is composed of a plurality of subfields in which gradation weights are determined in advance. Then, by combining a subfield that is lit (lighting subfield) and a subfield that is not lit (non-lighting subfield), each discharge cell emits light with a light emission luminance corresponding to the magnitude of the gradation value based on the image signal. .
  • subfield code a combination of a lighting subfield and a non-lighting subfield
  • code set a set of a plurality of subfield codes
  • a subfield code is selected from a plurality of subfield codes constituting a code set according to a gradation value. Then, light emission / non-light emission of each subfield is controlled based on the subfield code, and the discharge cell is caused to emit light with a luminance corresponding to the magnitude of the gradation value, and an image is displayed on the panel 10.
  • the gradation value when displaying black (the gradation value when no sustain discharge occurs) is assumed to be “0”.
  • a gradation value corresponding to the gradation weight “N” is expressed as a gradation value “N”.
  • the gradation value displayed by the discharge cells that emit light only in the subfield SF1 having the gradation weight “1” is the gradation value “1”.
  • FIG. 4 is a diagram showing an example of a code set when one field is composed of eight subfields.
  • the numerical value shown immediately below the notation indicating each subfield represents the gradation weight of each subfield.
  • FIG. 4 includes eight subfields SF1 to SF8 in one field, and each subfield is “1”, “2”, “3”, “5”, “8”, respectively. ”,“ 13 ”,“ 21 ”, and“ 34 ”indicate code sets having gradation weights.
  • the light emitting subfield is indicated by “1”
  • the non-light emitting subfield is indicated by a blank
  • the leftmost column indicates the gradation value to be displayed in each subfield code.
  • the subfield code corresponding to the gradation value “2” is “01000000”.
  • subfield code data 0 or 1 is arranged in the order of subfield SF1, subfield SF2, subfield SF3, subfield SF4, subfield SF5, subfield SF6, subfield SF7, and subfield SF8 from the left.
  • binary numerical values shown as subfield codes are arranged in the order of subfield SF1, subfield SF2, subfield SF3,.
  • the subfield code corresponding to the gradation value “14” is “11101000”. Accordingly, in the discharge cell displaying the gradation value “14”, the subfield SF1, the subfield SF2, the subfield SF3, and the subfield SF5 emit light.
  • FIG. 5 is a diagram schematically showing an example of a circuit block constituting the image display device 30 according to the embodiment of the present invention.
  • the image display device 30 includes a panel 10 and a drive circuit that drives the panel 10.
  • the drive circuit includes an image signal processing circuit 31, a data electrode drive circuit 32, a scan electrode drive circuit 33, a sustain electrode drive circuit 34, a timing generation circuit 35, and a power supply circuit (not shown) that supplies necessary power to each circuit block. It has.
  • the image signals input to the image signal processing circuit 31 are a red image signal, a green image signal, and a blue image signal. Based on the red image signal, the green image signal, and the blue image signal, the image signal processing circuit 31 sets each gradation value of red, green, and blue (a gradation value expressed by one field) to each discharge cell. To do.
  • the input image signal includes a luminance signal (Y signal) and a saturation signal (C signal, or RY signal and BY signal, or u signal and v signal, etc.).
  • a red image signal, a green image signal, and a blue image signal are calculated based on the luminance signal and the saturation signal, and then, each gradation value of red, green, and blue is set in each discharge cell.
  • the red, green, and blue gradation values set for each discharge cell are subfield codes indicating lighting / non-lighting for each subfield (light emission / non-light emission corresponds to digital signals “1” and “0”).
  • the subfield code is output as a display code. That is, the image signal processing circuit 31 converts the red image signal, the green image signal, and the blue image signal into a red display code, a green display code, and a blue display code and outputs the converted signals.
  • the image signal processing circuit 31 does not convert an image signal into a subfield code using a conversion table, but converts the image signal into a subfield code by a logical operation. Details of this will be described later.
  • the timing generation circuit 35 generates various timing signals for controlling the operation of each circuit block based on the horizontal synchronization signal and the vertical synchronization signal.
  • the generated timing signal is supplied to each circuit block (data electrode drive circuit 32, scan electrode drive circuit 33, sustain electrode drive circuit 34, image signal processing circuit 31, etc.).
  • Scan electrode drive circuit 33 includes a ramp waveform generation unit, a sustain pulse generation unit, and a scan pulse generation unit (not shown in FIG. 5), and generates a drive voltage waveform based on a timing signal supplied from timing generation circuit 35. Then, the voltage is applied to each of scan electrode SC1 to scan electrode SCn.
  • the ramp waveform generator generates a forced initialization waveform and a selective initialization waveform to be applied to scan electrode SC1 through scan electrode SCn during the initialization period based on the timing signal.
  • the sustain pulse generator generates a sustain pulse to be applied to scan electrode SC1 through scan electrode SCn during the sustain period based on the timing signal.
  • the scan pulse generator includes a plurality of scan electrode drive ICs (scan ICs), and generates scan pulses to be applied to scan electrode SC1 through scan electrode SCn during the address period based on the timing signal.
  • Sustain electrode drive circuit 34 includes a sustain pulse generation unit and a circuit (not shown in FIG. 5) for generating voltage Ve, and generates and maintains a drive voltage waveform based on the timing signal supplied from timing generation circuit 35.
  • the voltage is applied to each of electrode SU1 through sustain electrode SUn.
  • a sustain pulse is generated based on the timing signal and applied to sustain electrode SU1 through sustain electrode SUn.
  • voltage Ve is generated based on the timing signal and applied to sustain electrode SU1 through sustain electrode SUn.
  • the data electrode drive circuit 32 includes the same number of switch circuits 36 as the data electrodes 22. In this embodiment, since the number of data electrodes 22 is “m”, the data electrode drive circuit 32 includes m switch circuits 36 (switch circuit 36 (1) to switch circuit 36 (m)). Each of the m switch circuits 36 (1) to 36 (m) corresponds to each of the m data electrodes D1 to Dm.
  • the data electrode drive circuit 32 generates an address pulse corresponding to each of the data electrodes D1 to Dm based on the display code of each color output from the image signal processing circuit 31 and the timing signal supplied from the timing generation circuit 35. .
  • the data electrode drive circuit 32 then writes a write pulse (write pulse voltage Vd or 0 (V) from the switch circuit 36 (1) to the switch circuit 36 (m) to the data electrode D1 to the data electrode Dm during the write period. )) Is applied.
  • the dedicated IC In order for the dedicated IC to operate normally, it is necessary to keep the power consumption, temperature, etc. within the predetermined range as the standard for the dedicated IC. For example, if the power consumption exceeds a predetermined upper limit of power consumption (allowable power loss), the dedicated IC may cause an abnormal operation. Therefore, in the image display device 30, the data electrode drive circuit 32 needs to operate so that the power consumption of the dedicated IC does not exceed a predetermined upper limit.
  • the display code is generated so as to reduce the power consumption of the data electrode driving circuit 32 while preventing the image display quality in the image display device 30 from deteriorating. Details of generation of the display code will be described later.
  • FIG. 6 is a diagram schematically showing an example of a circuit block constituting the image signal processing circuit 31 of the image display device 30 according to the embodiment of the present invention.
  • the image signal processing circuit 31 includes an attribute detection unit 41, an allowable noise calculation unit 42, and an image signal processing unit 48 corresponding to each of a red image signal, a green image signal, and a blue image signal.
  • the image signal processing unit 48 corresponding to the red image signal is referred to as “R signal processing unit 48R”
  • the image signal processing unit 48 corresponding to the green image signal is referred to as “G signal processing unit 48G”
  • the image signal processing unit 48 corresponding to the image signal is referred to as a “B signal processing unit 48B”. That is, the R signal processing unit 48R is a “red image signal processing unit”, the G signal processing unit 48G is a “green image signal processing unit”, and the B signal processing unit 48B is a “blue image signal processing unit”. It is.
  • the red image signal is abbreviated as “R signal”
  • the green image signal is abbreviated as “G signal”
  • the blue image signal is abbreviated as “B signal”.
  • the attribute detection unit 41 specifies the relationship between the image signal and the position of the pixel that displays the image signal for each of the R signal, the G signal, and the B signal.
  • time differentiation of the image signal corresponding to each pixel detecting a change in the image signal between the current field and the next field for the same discharge cell of the same pixel
  • whether each pixel is in the moving image area Detect whether it is in the still image area.
  • the allowable noise calculation unit 42 calculates the allowable noise level Ynz of luminance based on the R signal (SigR), G signal (SigG), and B signal (SigB) for one pixel.
  • an R signal SigR (upper) corresponding to a pixel one pixel above the target pixel, an R signal SigR (middle) corresponding to the target pixel, and an R signal SigR (lower) corresponding to a pixel one pixel below the target pixel.
  • the difference ⁇ SigR in the vertical direction of the R signal SigR is used.
  • abs (x) described above is a function for obtaining the absolute value of x.
  • Min (x, y) is a function for obtaining the smaller one (including the case where x and y are equal).
  • the G signal SigG (upper) corresponding to the pixel one pixel above the target pixel, the G signal SigG (middle) corresponding to the target pixel, and the G signal SigG (lower) corresponding to the pixel one pixel below the target pixel.
  • the calculation formula is as follows.
  • ⁇ SigG Min (abs (SigG (upper) -SigG (middle)), abs (SigG (middle) -SigG (lower)))
  • the B signal SigB (upper) corresponding to the pixel one pixel above the target pixel
  • the B signal SigB (middle) corresponding to the target pixel
  • the B signal SigB (lower) corresponding to the pixel one pixel below the target pixel.
  • ⁇ SigB Min (abs (SigB (upper) -SigB (middle)), abs (SigB (middle) -SigB (lower)))
  • ⁇ Y KR ⁇ ⁇ SigR + KG ⁇ ⁇ SigG + KB ⁇ ⁇ SigB
  • KR is a red luminance conversion coefficient
  • KG is a green luminance conversion coefficient
  • KB is a blue luminance conversion coefficient.
  • the value obtained by multiplying KG and the value obtained by multiplying the vertical difference ⁇ SigB of the B signal SigB by the blue luminance conversion coefficient KB is added to calculate the vertical luminance difference level ⁇ Y.
  • the calculated luminance difference level ⁇ Y is multiplied by a predetermined coefficient to calculate a luminance allowable noise level Ynz.
  • the predetermined coefficient is the power control signal Cnt.
  • the power control signal Cnt is generated in a power estimation unit (not shown).
  • the power estimation unit estimates power consumption in the image display device 30 based on the image signal, temperature, and the like.
  • the power estimation unit outputs the power control signal Cnt by increasing the value of the power control signal Cnt if the estimated value of power consumption is large, and decreasing the value of the power control signal Cnt if the estimated value of power consumption is small.
  • the method for estimating the power consumption in the power estimation unit may be a generally known power estimation method. For example, if the design of an image is detected, the estimated power consumption is increased if the design is fine, and the estimated power consumption is decreased if the design is small. A method of increasing the value or a method of increasing the estimated value of power consumption when the temperature of the image display device 30 rises may be used.
  • the power control signal Cnt is a real number equal to or greater than “0” and is continuously changed according to the change of the image signal.
  • the power control signal Cnt is not limited to this.
  • the object of the image signal processing circuit 31 in the present embodiment is to reduce the power consumption of the data electrode driving circuit 32 while preventing the image display quality in the image display device 30 from being deteriorated.
  • the image signal processing circuit 31 reduces the number of subfield codes used for displaying an image.
  • the image signal processing circuit 31 uses the luminance allowable noise level Ynz calculated by the allowable noise calculation unit 42 in order to reduce the number of subfield codes used for image display.
  • the R signal processing unit 48R calculates the red threshold value WRth by dividing the luminance allowable noise level Ynz by the red luminance conversion coefficient KR. Then, a red display code is output using a subfield code that prohibits a subfield having a gradation weight smaller than the red threshold WRth from becoming a non-lighting subfield.
  • the red display code is a subfield code used when displaying a gradation value corresponding to the R signal SigR on the red discharge cell.
  • the G signal processing unit 48G calculates the green threshold value WGth by dividing the allowable noise level Ynz of luminance by the green luminance conversion coefficient KG. Then, a green display code is output using a subfield code that prohibits a subfield having a gradation weight smaller than the green threshold WGth from becoming a non-lighting subfield.
  • the green display code is a sub-field code used when a gradation value corresponding to the G signal SigG is displayed on the green discharge cell in the target pixel.
  • the B signal processing unit 48B calculates the blue threshold WBth by dividing the luminance allowable noise level Ynz by the blue luminance conversion coefficient KB. Then, a blue display code is output using a subfield code that prohibits a subfield having a gradation weight smaller than the blue threshold WBth from becoming a non-lighting subfield.
  • the blue display code is a sub-field code used when a gradation value corresponding to the B signal SigB is displayed on the blue discharge cell in the target pixel.
  • the pixel of interest is a pixel that is a target of calculation of a gradation value at that time.
  • G signal processing unit 48G and the B signal processing unit 48B have the same circuit configuration as the R signal processing unit 48R except for the handled signals, and thus description thereof is omitted.
  • FIG. 7 is a diagram schematically showing an example of a circuit block constituting the R signal processing unit 48R of the image display device 30 according to the embodiment of the present invention.
  • the R signal processing unit 48R includes a base code generation unit 50R, a rule generation unit 61R, a rule addition unit 62R, an upper / lower code generation unit 70R, and a display code selection unit 80R.
  • a subfield code that is basic in subsequent signal processing is referred to as a “basic code”, and a code set including the base code is referred to as a “basic code set”.
  • the base code is a subfield code generated by lighting one by one or two in order from the subfield having the smallest gradation weight. Therefore, the base code is a subfield code in which a subfield having the largest gradation weight among the subfields to emit light and all subfields having a gradation weight smaller than that subfield emit light.
  • the base code generation unit 50R selects the tone value of the R signal input to the image signal processing circuit 31 (hereinafter referred to as “R input tone” or simply “input” from the base code set including a plurality of base codes. Based on “gradation”, “upper gradation base code” is selected.
  • the upper tone base code is a base code having a tone value larger than the R input tone and having a tone value closest to the R input tone. Accordingly, in the upper gradation base code, the subfield having the largest gradation weight among the lighting subfields and all subfields having the gradation weight smaller than that subfield are the lighting subfields.
  • the base code generation unit 50R selects a base code having a gradation value that is larger than the R input gradation and closest to the R input gradation, and outputs it as an upper gradation base code.
  • FIG. 8A is a diagram illustrating an example of a base code set used in the image display device 30 according to an embodiment of the present invention.
  • FIG. 8B is a diagram showing another example of the base code set used in the image display device 30 according to the embodiment of the present invention.
  • FIG. 8C is a diagram illustrating another example of the base code set used in the image display device 30 according to the embodiment of the present invention.
  • the light-emitting subfield is “1”
  • the non-light-emitting subfield is blank
  • each subfield code (base) is displayed in the second column from the left.
  • Code) represents the gradation value to be displayed.
  • the numerical value written immediately below the notation indicating each subfield in each base code set represents the gradation weight of each subfield.
  • FIG. 8A shows an example of a base code set often used in the NTSC standard.
  • one field is composed of eight subfields, and each subfield is “1”, “2”, “3”, “5”, “ It has gradation weights of “8”, “13”, “21”, and “34”.
  • the first subfield (subfield SF1) of one field is set to the subfield having the smallest gradation weight, and thereafter, the subfields are arranged so that the gradation weight is sequentially increased. . And it is set as a lighting subfield one by one in an order from the subfield with the smallest gradation weight. Therefore, the number of base codes included in this base code set is (the number of subfields constituting one field + 1). For example, in the example of the base code set shown in FIG. 8A, the number of base codes is nine.
  • FIG. 8B shows an example of a base code set often used in the PAL standard.
  • one field includes 12 subfields, and each subfield is “1”, “2”, “4”, “9”, “9” in order from the subfield SF1. It has gradation weights of “18”, “36”, “65”, “5”, “7”, “15”, “33”, “60”.
  • the base code set shown in FIG. 8B has two subfield groups.
  • the first subfield group is composed of subfields SF1 to SF7, and the second subfield group is composed of subfields SF8 to SF12.
  • Each subfield group has the first subfield of each subfield group (subfield SF1 and subfield SF8 in the example shown in FIG. 8B) as the subfield having the smallest gradation weight in each subfield group. Thereafter, the subfields are arranged so that the gradation weights are sequentially increased. In each subfield group, one or two lighting subfields are set in order from the subfield having the smallest gradation weight. Therefore, the number of base codes included in this base code set is equal to or less than (the number of subfields constituting one field + 1). For example, in the example of the base code set shown in FIG. 8B, the number of base codes is 10.
  • FIG. 8C shows an example of a base code set used in a 3D display device (stereoscopic display device).
  • the base code set shown in FIG. 8C includes one sub-field consisting of five sub-fields, and each sub-field is “1”, “16”, “8”, “4”, “ 2 "gradation weight.
  • the first subfield (subfield SF1) of one field is the subfield having the smallest gradation weight
  • the second subfield (subfield SF2) is the subfield having the largest gradation weight.
  • the subfields are arranged so that the gradation weights are sequentially reduced. And it is set as a lighting subfield one by one in an order from the subfield with the smallest gradation weight. Therefore, the number of base codes included in this base code set is (the number of subfields constituting one field + 1). For example, in the example of the base code set shown in FIG. 8C, the number of base codes is 6.
  • the image display device 30 generates a new code set based on the base code set as described above, and uses the code set to input gradation (R input gradation, G input gradation, and B input). Each input gradation of gradation) is converted into a subfield code.
  • the base code generation unit 50R includes a base code storage unit 52R and a base code selection unit 54R.
  • the base code storage unit 52R stores a base code set and gradation values of a plurality of base codes constituting the base code set. Each base code and each gradation value of the base code are associated with each other and stored in the base code storage unit 52R.
  • the base code selection unit 54R compares each tone value of the base code constituting the base code set with the R input tone. Then, a base code having a gradation value larger than the R input gradation and closest to the R input gradation is selected. Then, the selected base code is output as an upper gradation base code.
  • a new subcode not included in the base code set is obtained.
  • the rule generation unit 61R generates a first rule for generating this new subfield code.
  • the rule generation unit 61R uses the basis of the R signal SigR and the attributes detected by the attribute detection unit 41 (attributes associated with the R signal SigR) to increase the number of subfield codes used for image display.
  • a first rule for changing the lighting subfield in the upper gradation base code selected by the code generation unit 50R to the non-lighting subfield is generated.
  • the first rule generated by the rule generation unit 61R defines a law for changing the lighting subfield in the upper gradation base code to the non-lighting subfield.
  • the rule generated by the rule generation unit 61R restricts subfields to be changed from lighting to non-lighting in the upper gradation base code. This is because the gradation value of the new subfield code created by changing the lighting subfield to the non-lighting subfield in the upper gradation base code is smaller than the upper gradation base code. This is in order not to fall below.
  • the upper gradation base code allows unlimited subfields to change from lighting to non-lighting, all lighting subfields become non-lighting subfields, and subfield codes with a gradation value of “0” are generated. This is because there is a possibility that it may occur.
  • the first rule is generated so that the subfield code generated based on the rule has the next gradation value.
  • the “lower gradation base code” is a base code having a gradation value that is equal to or lower than the R input gradation and closest to the R input gradation.
  • the first rule generated by the rule generation unit 61R includes one or more of the following three rules. 1) A rule for setting the first subfield to be changed from the lighting subfield to the non-lighting subfield. 2) A rule for setting the second subfield to be changed from the lighting subfield to the non-lighting subfield. 3) A rule for setting a sub-field that prohibits non-lighting.
  • the rule adding unit 62R generates a second rule that occurs for each pixel.
  • the second rule is provided to suppress the power consumption of the data electrode driving circuit 32 while preventing the image display quality in the image display device 30 from deteriorating.
  • the rule adding unit 62R calculates the red threshold value WRth by dividing the luminance allowable noise level Ynz by the red luminance conversion coefficient KR. Then, the following rules are generated. 4) It is prohibited to turn off a subfield having a gradation weight smaller than the calculated red threshold value WRth.
  • This rule is the second rule. Details of these rules will be described later.
  • the rule adding unit 62R when the base code set shown in FIG. 8A is used, the rule adding unit 62R generates a rule of “prohibiting turning off the subfield SF1, subfield SF2, and subfield SF3”.
  • the difference level ⁇ Y in the vertical direction of luminance changes for each pixel based on the change of the image signal. Therefore, the allowable noise level Ynz of luminance also changes for each pixel based on the change of the image signal. That is, the second rule generated by the rule adding unit 62R also changes for each pixel based on the change in the luminance allowable noise level Ynz.
  • the second rule is generated and used together with the first rule.
  • the luminance allowable noise level Ynz used in the second rule is a variable that changes in proportion to the luminance vertical difference level ⁇ Y. Then, according to the second rule, it is prohibited that the subfield that displays the luminance smaller than the allowable noise level Ynz of the luminance on the target pixel is not turned off.
  • the change in luminance is easily noticeable in the region where the luminance difference level ⁇ Y is small, and the change in luminance is not easily noticeable in the region where the luminance difference level ⁇ Y is large.
  • the number of subfield codes (intermediate codes described later) that can be used for image display is relatively reduced and compared. An image can be displayed with a rough gradation change. Further, if the number of subfield codes that can be used for image display is reduced, the power consumption in the data electrode driving circuit 32 can be reduced. Then, by increasing the number of subfields prohibited from being turned off, the number of subfield codes that can be used for image display can be reduced.
  • the power consumption of the data electrode drive circuit 32 can be suppressed while suppressing a decrease in image display quality in the image display device 30.
  • the same operation as the R signal SigR is performed.
  • the upper and lower code generation unit 70R applies the first rule generated by the rule generation unit 61R and the second rule generated by the rule addition unit 62R to the upper tone base code output from the base code generation unit 50R.
  • the upper gradation code and the lower gradation code are generated.
  • the upper gradation code is a gradation value that is larger than the R input gradation and closest to the R input gradation among subfield codes that can be newly generated based on the first rule and the second rule. Is a subfield code having
  • the lower gradation code is a gradation that is lower than the R input gradation and closest to the R input gradation among the subfield codes that can be newly generated based on the first rule and the second rule.
  • a subfield code having a value is a gradation that is lower than the R input gradation and closest to the R input gradation among the subfield codes that can be newly generated based on the first rule and the second rule.
  • the upper / lower code generation unit 70R includes an intermediate code generation unit 72R and an upper / lower code selection unit 74R.
  • the intermediate code generation unit 72R converts the lighting subfield in the upper gradation base code into a non-lighting subfield. Change to generate a new subfield code.
  • the newly generated subfield code is referred to as “intermediate code”.
  • a set obtained by adding the original upper tone base code to these intermediate codes is referred to as an “intermediate code set”.
  • the intermediate code is a subfield code used when displaying an image on panel 10. Therefore, each discharge cell of panel 10 emits light with a luminance of a gradation value based on the intermediate code.
  • FIG. 9A is a diagram illustrating an example of an intermediate code set generated by the intermediate code generation unit 72R of the image display device 30 according to the embodiment of the present invention.
  • FIG. 9B is a diagram illustrating another example of the intermediate code set generated by the intermediate code generation unit 72R of the image display device 30 according to the embodiment of the present invention.
  • FIG. 9C is a diagram illustrating another example of the intermediate code set generated in the intermediate code generation unit 72R of the image display device 30 according to the embodiment of the present invention.
  • the light-emitting subfield is “1”
  • the non-light-emitting subfield is blank
  • the second column from the left is the subfield code (intermediate code).
  • Code represents the gradation value to be displayed.
  • the numerical value written immediately below the notation indicating each subfield in each intermediate code set represents the gradation weight of each subfield.
  • one field includes eight subfields, and each subfield is “1”, “2”, and “3” in order from the subfield SF1. , “5”, “8”, “13”, “21”, “34”.
  • FIG. 9A as an example of the intermediate code set, the above-described “1) rule for setting the first subfield to be changed from the lighting subfield to the non-lighting subfield” is shown in FIG.
  • An intermediate code set generated by applying to the base code “11111100” of the value “32” is shown.
  • rule 1 This “1) rule for setting the first subfield to be changed from a lighting subfield to a non-lighting subfield” is a rule that “one of the lighting subfields is changed to a non-lighting subfield”. (Hereinafter referred to as “rule 1”).
  • subfield SF1 to subfield SF6 are lighting subfields.
  • the subfield code “11111000” obtained by changing the subfield SF6 to the non-lighting subfield is equal to the base code (order .6) of the gradation value “19” illustrated in FIG. 8A. Accordingly, five subfield codes excluding the subfield code “11111000” are newly generated intermediate codes.
  • FIG. 9B as an example of the intermediate code set, in addition to the above-described rule 1, “2) a rule for setting the second subfield to be changed from the lighting subfield to the non-lighting subfield” is shown in FIG.
  • Rule 2 for setting the second subfield to be changed from the lighting subfield to the non-lighting subfield is “the subfield code having the smallest gradation value among the newly generated intermediate codes”.
  • the sub-field SF2 is a non-lighting sub-field ”(hereinafter referred to as“ rule 2 ”).
  • FIG. 9C as an example of the intermediate code set, in addition to the above-described rule 1, “3) a rule for setting a subfield that prohibits non-lighting” is shown in the gradation value “A” a rule for setting a subfield that prohibits non-lighting” is shown in the gradation value “A” a rule for setting a subfield that prohibits non-lighting” is shown in the gradation value “A” a rule for setting a subfield that prohibits non-lighting” is shown in the gradation value “ An intermediate code set generated by applying to the base code “11111100” of “32” is shown.
  • rule for setting a subfield that prohibits non-lighting is a rule that “subfield SF1 and subfield SF2 are prohibited from being non-lighting subfield” (hereinafter “rule”). 3 ”).
  • sub-field code in which sub-field SF1 or sub-field SF2 is a non-lighting sub-field has a sub-field code “10111100” with a gradation value “30” and a gradation value “ 31 ”is a sub-field code“ 01111100 ”.
  • the subfield codes having the gradation value “30” and the gradation value “31” are excluded from the intermediate code set.
  • rule 1 and rule 3 are used as the first rule.
  • rule 2 may be added to the first rule.
  • the image display device 30 displays an image with relatively low power consumption, or when an image with relatively little occurrence of moving image pseudo contour is displayed, the number of intermediate codes generated can be increased. It is. Then, by increasing the number of intermediate codes generated, an image can be displayed with a smoother gradation change.
  • the intermediate code generation unit 72R sets the lighting subfield in the upper gradation base code to the non-lighting subfield based on the first rule generated by the rule generation unit 61R and the second rule generated by the rule addition unit 62R. Change to field to generate intermediate code and generate intermediate code set.
  • FIGS. 9A, 9B, and 9C show an example in which an intermediate code set is generated based only on the first rule. An example of generating an intermediate code set based on the second rule in addition to the first rule will be described later.
  • the intermediate code generation unit 72R adds the first rule generated by the rule generation unit 61R and the second rule generated by the rule addition unit 62R to the upper gradation base code output from the base code generation unit 50R.
  • an intermediate code is generated and an intermediate code set is generated.
  • the upper / lower code selection unit 74R compares each gradation value of the subfield code constituting the intermediate code set generated by the intermediate code generation unit 72R with the R input gradation. Then, the upper / lower code selection unit 74R selects a subfield code having a gradation value larger than the R input gradation and closest to the R input gradation, and outputs it as an upper gradation code. Further, the upper / lower code selection unit 74R selects a subfield code having a gradation value equal to or lower than the R input gradation and closest to the R input gradation, and outputs it as a lower gradation code.
  • the display code selection unit 80R calculates a gradation value to be displayed on the target pixel by adding a predetermined value to the R input gradation. Then, the display code selection unit 80R selects one of the upper gradation code and the lower gradation code that has a gradation value closer to the gradation value to be displayed on the target pixel, and outputs it as a display code.
  • the pixel of interest is a pixel that is a target of calculation of the gradation value at that time, and in the above example, means a red discharge cell in the pixel of interest.
  • the above-described predetermined value added to the input gradation is an error diffused by the error diffusion process and a dither value calculated by the dither process. Therefore, the display code selection unit 80R adds the error and the dither value to the R input gradation to calculate the gradation value to be displayed on the target pixel, and selects the attention value from among the upper gradation code and the lower gradation code. The display code having a gradation value closer to the gradation value to be displayed on the pixel is selected. Further, the display code selection unit 80R calculates the difference between the gradation value to be displayed on the target pixel and the gradation value of the display code, and diffuses the difference as an error to surrounding pixels. For example, in the above-described case, the display code selection unit 80R diffuses the error to the red discharge cells in the peripheral pixels.
  • the display code selection unit 80R includes a dither selection unit 82R, an error diffusion unit 84R, and a display code determination unit 86R.
  • the dither selection unit 82R stores a plurality of dither patterns. Then, one dither pattern is selected from a plurality of stored dither patterns based on the red image signal (R signal) and the attribute detected by the attribute detection unit 41.
  • the dither selection unit 82R selects a dither element corresponding to the position of the pixel from the selected dither pattern based on the position of the pixel displaying the R signal. Further, the dither selection unit 82R calculates the dither value by multiplying the selected dither element by the difference between the gradation value of the upper gradation code and the gradation value of the lower gradation code.
  • FIG. 10A is a diagram illustrating an example of a dither pattern used in the image display device 30 according to an embodiment of the present invention.
  • FIG. 10B is a diagram showing another example of the dither pattern used in the image display device 30 according to the embodiment of the present invention.
  • one column represents one pixel.
  • FIG. 10A shows the simplest binary dither.
  • “+0.25” and “ ⁇ 0.25” are arranged in a checkered pattern as dither elements.
  • FIG. 10B is a diagram showing an example of quaternary dither. In FIG. 10B, dither elements “+0.375”, “+0.125”, “ ⁇ 0.375” and “ ⁇ 0.125” are arranged.
  • the error diffusion unit 84R outputs an error to be added to the red discharge cell of the target pixel to the display code determination unit 86R and diffuses the error output from the display code determination unit 86R to the peripheral pixels of the target pixel.
  • the dither selection unit 82R stores, for example, the two types of dither patterns shown in FIGS. 10A and 10B, and selects one of the dither patterns based on the R signal and the attribute detected by the attribute detection unit 41. .
  • the dither pattern shown in FIG. 10A is selected, the dither element is either “+0.25” or “ ⁇ 0.25”.
  • the dither element shown in FIG. 10B is selected, the dither element is “+0”. .375 ”,“ +0.125 ”,“ ⁇ 0.375 ”, and“ ⁇ 0.125 ”.
  • the dither selection unit 82R selects any one of these dither elements based on the position of the pixel displaying the R signal. Further, the dither value is calculated by multiplying the selected dither element by the difference between the tone value of the upper tone code and the tone value of the lower tone code. The calculated dither value is added to the R input gradation in the display code selection unit 80R.
  • FIG. 11 is a diagram showing error diffusion coefficients of the error diffusion unit 84R of the image display device 30 according to the embodiment of the present invention.
  • one column represents one pixel.
  • the middle column in FIG. 11 represents a pixel (target pixel) that is a target of error diffusion processing.
  • the error diffusion unit 84R diffuses (adds) a value obtained by multiplying the error generated in the pixel arranged at the upper left of the target pixel by the diffusion coefficient k1 to the target pixel. Further, the error diffusion unit 84R diffuses (adds) a value obtained by multiplying the error generated in the pixel arranged on the target pixel by the diffusion coefficient k2 to the target pixel. Further, the error diffusion unit 84R diffuses (adds) a value obtained by multiplying the error generated in the pixel arranged at the upper right of the target pixel by the diffusion coefficient k3 to the target pixel. Further, the error diffusion unit 84R diffuses (adds) a value obtained by multiplying the error generated in the pixel arranged on the left side of the target pixel by the diffusion coefficient k4 to the target pixel.
  • the error diffusion unit 84R diffuses (adds) a value obtained by multiplying the error generated in the target pixel by the diffusion coefficient k4 to the pixel arranged to the right of the target pixel. Further, the error diffusion unit 84R diffuses (adds) a value obtained by multiplying the error generated in the target pixel by the diffusion coefficient k3 to the pixel arranged at the lower left of the target pixel. Further, the error diffusion unit 84R diffuses (adds) a value obtained by multiplying the error generated in the target pixel by the diffusion coefficient k2 to the pixel arranged below the target pixel. Further, the error diffusion unit 84R diffuses (adds) a value obtained by multiplying the error generated in the target pixel by the diffusion coefficient k1 to the pixel arranged at the lower right of the target pixel.
  • which diffusion coefficient is selected is determined using a random number generated by a random number generator (not shown).
  • the display code determination section 86R converts the display code actually used for image display into the upper gradation. Either a code or a lower gradation code is determined.
  • the display code determination unit 86R adds a dither value and an error to the R input gradation, and calculates a gradation value to be displayed on the red discharge cell in the target pixel.
  • the display code is selected as the display code.
  • the display code determination unit 86R calculates a difference between the gradation value to be displayed in the red discharge cell in the target pixel and the gradation value of the display code, and uses the difference as a newly generated error as the error diffusion unit 84R. Output to.
  • the G signal processing unit 48G has the same configuration as the R signal processing unit 48R. That is, the G signal processing unit 48G includes a base code generation unit 50G, a rule generation unit 61G, a rule addition unit 62G, an upper and lower code generation unit 70G, and a display code selection unit 80G. Since each circuit block constituting the G signal processing unit 48G has the same configuration and operation as each circuit block constituting the R signal processing unit 48R, detailed description thereof is omitted.
  • the B signal processing unit 48B has the same configuration as the R signal processing unit 48R. That is, the B signal processing unit 48B includes a base code generation unit 50B, a rule generation unit 61B, a rule addition unit 62B, an upper and lower code generation unit 70B, and a display code selection unit 80B. Since each circuit block constituting the B signal processing unit 48B has the same configuration and operation as each circuit block constituting the R signal processing unit 48R, detailed description thereof is omitted.
  • the image signal processing circuit 31 operates based on the following conditions. 1)
  • the base code set shown in FIG. 8A is used as the base code set. 2)
  • the rules used in the description of FIG. 9A are used. That is, rule 1 “change any one of the lighting subfields to a non-lighting subfield” is used. 3) Based on the attribute accompanying the image signal, “Rule for setting sub-field forbidden to turn off” (rule 3) is added to rule 1.
  • a threshold (WRth, WGth, WBth) is calculated from the allowable noise level Ynz of luminance and the luminance conversion coefficients (KR, KG, KB), and “a subfield having a gradation weight smaller than the threshold is not “Prohibit light emission” (second rule) is used together with the first rule.
  • FIG. 12 is a flowchart showing the operation of the image signal processing circuit 31 of the image display device 30 according to the embodiment of the present invention.
  • the image signal processing circuit 31 executes the following series of steps.
  • Step S41 Three image signals corresponding to one pixel (target pixel), that is, an R signal SigR (middle), a G signal SigG (middle), and a B signal SigB (middle) are input to the image signal processing circuit 31.
  • the attribute detection unit 41 detects an attribute associated with the image signal.
  • the image signal processing circuit 31 includes an R signal SigR (upper), a G signal SigG (upper), and a B signal SigB (upper) corresponding to a pixel one pixel above the target pixel, and one pixel below the target pixel.
  • the R signal SigR (lower), the G signal SigG (lower), and the B signal SigB (lower) corresponding to the pixels are input.
  • the image signal processing circuit 31 determines the vertical difference ⁇ SigR of the R signal SigR, the vertical difference ⁇ SigG of the G image signal SigG, and the vertical difference ⁇ SigB of the B image signal SigB based on the above-described calculation formula. Are calculated respectively.
  • the gradation value (R input gradation) of the R signal SigR (medium) is “25”
  • the gradation value (G input gradation) of the G signal SigG (medium) Is “20”
  • the gradation value (B input gradation) of the B signal SigB (medium) is “45”.
  • the attribute associated with the image signal is a moving image and contour The description will be made on the assumption that the detection result of the part is obtained.
  • the allowable noise calculation unit 42 determines the allowable noise level Ynz of the luminance based on the vertical difference ⁇ SigR of the R signal SigR, the vertical difference ⁇ SigG of the G image signal SigG, and the vertical difference ⁇ SigB of the B image signal SigB. Is calculated.
  • the gradation value of the R signal SigR (upper) is “8”, the gradation value of the R signal SigR (lower) is “41”, and the gradation value of the G signal SigG (upper) is “50”.
  • the gradation value of the G signal SigG (lower) is “49”, the gradation value of the B signal SigB (upper) is “21”, and the gradation value of the B signal SigB (lower) is “70”. ”.
  • the vertical difference ⁇ SigR of the R signal SigR, the vertical difference ⁇ SigG of the G image signal SigG, and the vertical difference ⁇ SigB of the B image signal SigB have the following numerical values, respectively.
  • the vertical difference between the image signals of the respective colors is the absolute value of the difference between each gradation value of the target pixel and each gradation value of the pixel adjacent to the target pixel, and each gradation value of the target pixel.
  • the absolute value of the difference from each gradation value of the pixel adjacent below the target pixel is equal to the smaller one (including the case where they are equal).
  • the base code generation unit 50R selects an upper gradation base code corresponding to the R signal.
  • the base code generation unit 50G selects the upper tone base code corresponding to the G signal.
  • the base code generation unit 50B selects the upper tone base code corresponding to the B signal.
  • step S50 the sub-field code having a gradation value that is larger than the gradation value of the image signal at the target pixel and closest to the gradation value of the image signal at the target pixel is selected from the plurality of basic sub-field codes.
  • the field code is selected as the upper gradation base code.
  • the base code generation unit 50R compares each tone value of the base code constituting the base code set stored in the base code storage unit 52R with the R input tone. Then, a base code having a gradation value larger than the R input gradation and closest to the R input gradation is selected and output as an upper gradation base code.
  • the base code generation unit 50G compares each tone value of the base code constituting the base code set stored in the base code storage unit 52G with the G input tone. Then, a base code having a gradation value larger than the G input gradation and closest to the G input gradation is selected and output as an upper gradation base code.
  • the base code generation unit 50B compares each tone value of the base code constituting the base code set stored in the base code storage unit 52B with the B input tone. Then, a base code having a gradation value larger than the B input gradation and closest to the B input gradation is selected and output as an upper gradation base code.
  • the base code generation unit 50R selects the base code “11111100” having the gradation value “32” and outputs it as the upper gradation base code.
  • the base code set shown in FIG. 8A has a gradation value larger than the gradation value “20” and closest to the gradation value “20”.
  • the base code is a base code having a gradation value of “32”. Therefore, the base code generation unit 50G selects the base code “11111100” having the gradation value “32” and outputs it as the upper gradation base code.
  • the base code set shown in FIG. 8A has a gradation value that is larger than the gradation value “45” and closest to the gradation value “45”.
  • the base code is a base code having a gradation value of “53”. Therefore, the base code generation unit 50B selects the base code “11111110” having the gradation value “53” and outputs it as the upper gradation base code.
  • Step S61 Each of the rule generation unit 61R, the rule generation unit 61G, and the rule generation unit 61B generates a first rule for generating an intermediate code set.
  • step S61 based on the image signal at the target pixel, the first rule for generating a new subfield code by changing the light emitting subfield in the upper gradation base code to the non-light emitting subfield is generated. To do.
  • each of the rule generation unit 61R, the rule generation unit 61G, and the rule generation unit 61B if the attribute attached to the image signal is a still image, A basic rule (rule 1) of “change to field” is generated.
  • Each of the rule generation unit 61R, the rule generation unit 61G, and the rule generation unit 61B can be used to display an image in order to suppress the moving image pseudo contour if the attribute attached to the image signal is a moving image.
  • Limit field codes are used to display an image in order to suppress the moving image pseudo contour if the attribute attached to the image signal is a moving image.
  • the subfield codes include those that have a high effect of suppressing moving image pseudo contours and those that do not.
  • the base codes shown in FIGS. 8A to 8C are subfield codes that have a high effect of suppressing the moving image pseudo contour.
  • the appearance of the moving image pseudo contour depends on the subfield code that can be used to display the image, and the image is displayed using the subfield code that is highly effective in suppressing the moving image pseudo contour.
  • the moving image pseudo contour can be suppressed.
  • the subfield code that can be used for displaying an image is limited as compared with the case where the suppression of the moving image pseudo contour is unnecessary. This is the reason for limiting the subfield codes that can be used for image display in order to suppress the moving image pseudo contour in each of the rule generation unit 61R, the rule generation unit 61G, and the rule generation unit 61B.
  • each of the rule generation unit 61R, the rule generation unit 61G, and the rule generation unit 61B is based on the basic rule 1 in order to suppress the moving image pseudo contour. "Rules for setting subfields that are prohibited from being unlit” are added. This additional rule is, for example, rule 3 described with reference to FIG. 9C, that “subfield SF1 and subfield SF2 are prohibited from being non-lighting subfields”. Thereby, each of the rule generation unit 61R, the rule generation unit 61G, and the rule generation unit 61B restricts subfield codes that can be used for displaying an image.
  • each of the rule generating unit 61R, the rule generating unit 61G, and the rule generating unit 61B generates the first.
  • the attribute attached to the image signal is a still image (that is, when the image signal at the target pixel is a still image)
  • each of the rule generation unit 61R, the rule generation unit 61G, and the rule generation unit 61B Includes the first rule to be generated.
  • Step S62 Each of the rule adding unit 62R, the rule adding unit 62G, and the rule adding unit 62B generates a second rule.
  • a threshold (WRth, WGth, WBth) is calculated from the allowable noise level Ynz of luminance and the luminance conversion coefficients (KR, KG, KB), and subfields having gradation weights smaller than the threshold are calculated.
  • a second rule that prohibits the non-lighting is generated.
  • the rule adding unit 62R calculates the red threshold WRth by dividing the luminance allowable noise level Ynz by the red luminance conversion coefficient KR. Then, the subfield having a gradation weight smaller than the red threshold WRth is prohibited from being turned off. This is the second rule generated by the rule adding unit 62R.
  • the rule adding unit 62G calculates the green threshold value WGth by dividing the luminance allowable noise level Ynz by the green luminance conversion coefficient KG. Then, it is prohibited that a subfield having a gradation weight smaller than the green threshold WGth is not lit. This is the second rule generated by the rule adding unit 62G.
  • the rule adding unit 62B calculates the blue threshold value WBth by dividing the luminance allowable noise level Ynz by the blue luminance conversion coefficient KB. Then, it is prohibited that the subfield having the gradation weight smaller than the blue threshold WBth is not turned on. This is the second rule generated by the rule adding unit 62B.
  • the red threshold value WRth is the following numerical value.
  • the subfields having gradation weights smaller than “4.1” are subfield SF1 having gradation weight “1”, subfield SF2 having gradation weight “2”, and This is a subfield SF3 having a gradation weight of “3”. Therefore, the rule adding unit 62R generates the second rule that “the subfield SF1, the subfield SF2, and the subfield SF3 are prohibited from becoming non-lighting subfields”.
  • the second rule is used together with the first rule generated by the rule generation unit 61R.
  • subfields having a gradation weight smaller than “2.05” are a subfield SF1 having a gradation weight “1” and a subfield SF2 having a gradation weight “2”. is there. Therefore, the rule adding unit 62G generates a second rule that “the subfield SF1 and the subfield SF2 are prohibited from becoming non-lighting subfields”. The second rule is used together with the first rule generated by the rule generation unit 61G.
  • the blue threshold WBth is as follows.
  • subfields having gradation weights smaller than “12.3” are subfield SF1 having gradation weight “1”, subfield SF2 having gradation weight “2”, A subfield SF3 having a tone weight “3”, a subfield SF4 having a tone weight “5”, and a subfield SF5 having a tone weight “8”.
  • the rule adding unit 62B generates a second rule that “inhibits each subfield from subfield SF1 to subfield SF5 from becoming a non-lighting subfield”.
  • the second rule is used together with the first rule generated by the rule generation unit 61B.
  • Step S72 Each of the intermediate code generation unit 72R, the intermediate code generation unit 72G, and the intermediate code generation unit 72B generates an intermediate code set.
  • the intermediate code generation unit 72R generates an intermediate code from the upper gradation base code based on the first rule generated by the rule generation unit 61R and the second rule generated by the rule addition unit 62R. Generate an intermediate code set.
  • the intermediate code generation unit 72G generates an intermediate code from the upper gradation base code based on the first rule generated by the rule generation unit 61G and the second rule generated by the rule addition unit 62G, and generates an intermediate code set To do.
  • the intermediate code generation unit 72B generates an intermediate code from the upper gradation base code based on the first rule generated by the rule generation unit 61B and the second rule generated by the rule addition unit 62B, and generates an intermediate code set To do.
  • FIG. 13A shows an intermediate code generation unit 72R based on the first rule generated by the rule generation unit 61R of the image display device 30 and the second rule generated by the rule addition unit 62R in the embodiment of the present invention. It is a figure which shows an example of the intermediate
  • FIG. 13B shows the intermediate code generation unit 72B based on the first rule generated in the rule generation unit 61B of the image display device 30 and the second rule generated in the rule addition unit 62B in the embodiment of the present invention. It is a figure which shows an example of the intermediate
  • the intermediate code generation unit 72R generates the code set shown in FIG. 9C based on the R input gradation and the first rule. Indicates an intermediate code set generated by applying a rule.
  • the first rule at this time is rule 1 “change any one of the lighting subfields to the non-lighting subfield” and rule 3 “set the subfield SF1 and the subfield SF2 to the nonlighting subfield. It is assumed that the second rule is “inhibiting subfield SF1, subfield SF2, and subfield SF3 from becoming non-lighting subfields”.
  • the newly generated subfield codes based on the first rule are “11110100” of the gradation value “24”, “11101100” of the gradation value “27”, and “11011100” of the gradation value “29”. If there is, the gradation value “29” “11011100” violates the second rule because the subfield SF3 is a non-lighting subfield. Accordingly, the two subfield codes of the gradation value “24” and the gradation value “27” excluding the gradation value “29” are newly generated intermediate codes based on the first rule and the second rule. . Thus, the intermediate code set shown in FIG. 13A is obtained.
  • the second rule is “inhibiting subfield SF1 and subfield SF2 from becoming non-lighting subfields”
  • the second rule is equal to rule 3. Therefore, for example, the intermediate code generation unit 72G generates the code set shown in FIG. 9C based on the G input gradation and the first rule, and further, the sub-field SF1 and the sub-field SF2 are not included in this code set. If the second rule “prohibit to become a lighting subfield” is applied, the intermediate code generated based on the first rule and the second rule is equal to the code set shown in FIG. 9C.
  • the intermediate code generation unit 72B newly generates four subfield codes based on the B input gradation and the first rule. Indicates an intermediate code set generated by applying a rule.
  • the B signal processing unit 48B selects “11111110” of the gradation value “53” as the upper gradation base code based on the B input gradation and the first rule composed of the rules 1 and 3.
  • Four sub-field codes of gradation value “40” “11111010”, gradation value “45” “11110110”, gradation value “48” “11101110”, and gradation value “50” “11011110” Is newly generated.
  • the rule adding unit 62B generates a second rule “inhibiting each subfield from subfield SF1 to subfield SF5 from becoming a non-lighting subfield”, the gradation value “45”.
  • the sub-field code of the gradation value “40” excluding those gradation values is an intermediate code newly generated based on the first rule and the second rule. In this way, the intermediate code set shown in FIG. 13B is obtained.
  • Step S74 Each of the upper / lower code selection unit 74R, the upper / lower code selection unit 74G, and the upper / lower code selection unit 74B selects an upper gradation code and a lower gradation code.
  • step S74 the target pixel larger than the tone value of the image signal in the target pixel is selected from the intermediate code set generated by applying the first rule and the second rule described above to the upper tone base code.
  • the subfield code having the gradation value closest to the gradation value of the image signal at is selected as the upper gradation code, and the gradation value of the image signal at the target pixel is equal to or lower than the gradation value of the image signal at the target pixel
  • the subfield code having the closest gradation value is selected as the lower gradation code.
  • the upper / lower code selection unit 74R compares each gradation value of the subfield code constituting the intermediate code set with the R input gradation. Then, a subfield code having a gradation value larger than the R input gradation and closest to the R input gradation is selected, and is output as an upper gradation code. Further, a subfield code having a gradation value equal to or lower than the R input gradation and closest to the R input gradation is selected and output as a lower gradation code.
  • the upper / lower code selection unit 74G compares each gradation value of the subfield code constituting the intermediate code set with the G input gradation. Then, a subfield code having a gradation value larger than the G input gradation and closest to the G input gradation is selected and output as an upper gradation code. In addition, a subfield code having a gradation value which is equal to or less than the G input gradation and closest to the G input gradation is selected and output as a lower gradation code.
  • the upper / lower code selection unit 74B compares each gradation value of the subfield code constituting the intermediate code set with the B input gradation. Then, a subfield code having a gradation value larger than the B input gradation and closest to the B input gradation is selected and output as an upper gradation code. In addition, a subfield code having a gradation value which is equal to or less than the B input gradation and closest to the B input gradation is selected and output as a lower gradation code.
  • the subfield code corresponding to the upper gradation code is the floor code. This is a subfield code of the key value “27”.
  • the subfield code corresponding to the lower gradation code is a subfield code having a gradation value of “24”. Therefore, the upper / lower code selection unit 74R selects the subfield code “11101100” having the gradation value “27” as the upper gradation code and the subfield code “11110100” having the gradation value “24” as the lower gradation code. ”Is selected.
  • the subfield code corresponding to the upper gradation code is This is a subfield code of the key value “24”.
  • the subfield code corresponding to the lower gradation code is a subfield code having a gradation value “19”. Therefore, the upper / lower code selection unit 74G selects the subfield code “11110100” having the gradation value “24” as the upper gradation code and the subfield code “11111000” having the gradation value “19” as the lower gradation code. ”Is selected.
  • the subfield code corresponding to the upper gradation code is the scale. This is a subfield code of the key value “53”.
  • the subfield code corresponding to the lower gradation code is a subfield code having a gradation value of “40”. Therefore, the upper / lower code selection unit 74B selects the subfield code “11111110” having the gradation value “53” as the upper gradation code and the subfield code “11111010” having the gradation value “40” as the lower gradation code. ”Is selected.
  • Step S82 Each of the dither selection unit 82R, the dither selection unit 82G, and the dither selection unit 82B selects a dither element based on the attribute of the image signal.
  • the dither selection unit 82R For example, if the dither pattern shown in FIG. 10A and the dither pattern shown in FIG. 10B are stored in each of the dither selection unit 82R, dither selection unit 82G, and dither selection unit 82B, the dither selection unit 82R, Each of the dither selector 82G and the dither selector 82B selects one of the dither patterns based on the image signal and the attribute detected by the attribute detector 41.
  • the dither pattern shown in FIG. 10A is selected. If the attribute attached to the image signal is not a contour portion, the dither pattern shown in FIG. 10B is selected. If each of the selection unit 82R, the dither selection unit 82G, and the dither selection unit 82B is set, and the attribute attached to the image signal is a contour portion, the dither selection unit 82R, the dither selection unit 82G, and the dither selection unit 82B Each select the dither pattern shown in FIG. 10A.
  • Each of the dither selection unit 82R, the dither selection unit 82G, and the dither selection unit 82B selects one of the dither elements set in the dither pattern based on the position of the target pixel. For example, each of the dither selection unit 82R, the dither selection unit 82G, and the dither selection unit 82B selects “0.25” as the dither element based on the dither pattern shown in FIG. 10A.
  • Step S83 Each of the dither selection unit 82R, the dither selection unit 82G, and the dither selection unit 82B calculates a dither value.
  • Each of the dither selection unit 82R, dither selection unit 82G, and dither selection unit 82B multiplies the selected dither element by the difference between the tone value of the upper tone code and the tone value of the lower tone code. Calculate the value.
  • the upper gradation code selected in step S74 is the gradation value “27”, the gradation value of the lower gradation code selected in step S74 is “24”, and the dither selected in step S82. If the element is “0.25”, the dither selection unit 82R multiplies the difference “3” between the gradation value of the upper gradation code and the gradation value of the lower gradation code by the dither element “0.25”. Then, the dither value “0.75” is calculated.
  • the upper gradation code selected in step S74 is the gradation value “24”
  • the gradation value of the lower gradation code selected in step S74 is “19”
  • the dither selected in step S82 If the element is “0.25”, the dither selection unit 82G multiplies the difference “5” between the gradation value of the upper gradation code and the gradation value of the lower gradation code by the dither element “0.25”. Then, the dither value “1.25” is calculated.
  • the upper gradation code selected in step S74 is the gradation value “53”, the gradation value of the lower gradation code selected in step S74 is “40”, and the dither selected in step S82. If the element is “0.25”, the dither selector 82B multiplies the difference “13” between the gradation value of the upper gradation code and the gradation value of the lower gradation code by the dither element “0.25”. Then, the dither value “3.25” is calculated.
  • Step S86 Each of the display code determination unit 86R, the display code determination unit 86G, and the display code determination unit 86B calculates a gradation value to be displayed on the target pixel.
  • step S86 a predetermined value is added to the gradation value of the image signal at the target pixel to calculate the gradation value to be displayed on the target pixel.
  • each of the display code determination unit 86R, the display code determination unit 86G, and the display code determination unit 86B adds the dither value calculated in step S83 to each input gradation of R, G, and B. Further, based on the calculation result in step S88, errors output from each of the error diffusion unit 84R, error diffusion unit 84G, and error diffusion unit 84B are added to calculate a gradation value to be displayed on the target pixel. Therefore, the predetermined value described above is the dither value output from each of the dither selection unit 82R, dither selection unit 82G, and dither selection unit 82B, and the error diffusion unit 84R, error diffusion unit 84G, and error diffusion unit 84B. It is a numerical value obtained by adding the error output from each.
  • the R input gradation is the gradation value “25”
  • the dither value calculated in step S83 is “0.75”
  • the G input gradation is the gradation value “20”
  • the dither value calculated in step S83 is “1.25”
  • the B input gradation is the gradation value “45”
  • the dither value calculated in step S83 is “3.25”
  • Step S87 Each of the display code determination unit 86R, the display code determination unit 86G, and the display code determination unit 86B determines a display code to be used when displaying a gradation value on the target pixel.
  • step S87 the upper gradation code and the lower gradation code having the gradation value closer to the gradation value to be displayed on the target pixel is selected as the display code.
  • each of the display code determination unit 86R, the display code determination unit 86G, and the display code determination unit 86B includes the gradation value to be displayed on the target pixel, the gradation value of the upper gradation code, and the lower gradation. Compare the tone value of the code. If the gradation value to be displayed on the target pixel is closer to the gradation value of the upper gradation code than the gradation value of the lower gradation code, the display used when displaying the gradation value on the attention pixel Select the upper gradation code as the code and output it.
  • the gradation value to be displayed on the target pixel is closer to the gradation value of the lower gradation code than the gradation value of the upper gradation code, it is used when displaying the gradation value on the attention pixel.
  • the lower gradation code is selected as the display code and is output.
  • the gradation value of the upper gradation code is “27”
  • the gradation value of the lower gradation code is “24”
  • the gradation value to be displayed in the red discharge cell in the target pixel is “24. 15 ”
  • the difference between the gradation value of the upper gradation code and the gradation value to be displayed in the red discharge cell in the target pixel is“ 2.85 ”
  • the gradation value of the lower gradation code and the attention The difference from the gradation value to be displayed in the red discharge cell in the pixel is “0.15”. Therefore, in this case, the display code determination unit 86R outputs the lower gradation code “11110100” having the gradation value “24” as the display code.
  • the gradation value of the upper gradation code is “24”
  • the gradation value of the lower gradation code is “19”
  • the gradation value to be displayed in the green discharge cell in the target pixel is “22. 85 ”
  • the difference between the gradation value of the upper gradation code and the gradation value to be displayed on the green discharge cell in the target pixel is“ 1.15 ”
  • the gradation value of the lower gradation code and the attention The difference from the gradation value to be displayed in the green discharge cell in the pixel is “3.85”. Therefore, in this case, the display code determination unit 86G outputs the lower gradation code “11110100” having the gradation value “24” as the display code.
  • the gradation value of the upper gradation code is “53”
  • the gradation value of the lower gradation code is “40”
  • the gradation value to be displayed in the blue discharge cell in the target pixel is “45. 05 ”
  • the difference between the gradation value of the upper gradation code and the gradation value to be displayed in the blue discharge cell in the target pixel is“ 7.95 ”
  • the gradation value of the lower gradation code and the attention The difference from the gradation value to be displayed in the blue discharge cell in the pixel is “5.05”. Therefore, in this case, the display code determination unit 86B outputs the lower gradation code “11111010” having the gradation value “40” as the display code.
  • Step S88 Each of display code determination unit 86R, display code determination unit 86G, and display code determination unit 86B calculates an error and outputs the error to each of error diffusion unit 84R, error diffusion unit 84G, and error diffusion unit 84B.
  • Each of the display code determination unit 86R, the display code determination unit 86G, and the display code determination unit 86B subtracts the gradation value of the display code from the gradation value to be displayed on the target pixel, and newly generates the subtraction result.
  • An error is output to each of the error diffusion unit 84R, the error diffusion unit 84G, and the error diffusion unit 84B.
  • the display code determination unit 86R outputs “0.15” as an error to the error diffusion unit 84R.
  • the display code determination unit 86G outputs “ ⁇ 1.15” as an error to the error diffusion unit 84G.
  • the display code determination unit 86B outputs “5.05” as an error to the error diffusion unit 84B.
  • step S88 When step S88 is completed, the process returns to step S41. In this way, a series of steps from step S41 to step S88 are repeatedly executed.
  • the image signal processing circuit 31 in the present embodiment includes the allowable noise calculation unit 42, the R signal processing unit 48R, the G signal processing unit 48G, and the B signal processing unit 48B.
  • the permissible noise calculation unit 42 calculates a luminance vertical difference ⁇ Y for each pixel, and calculates a luminance allowable noise level Ynz based on the calculated luminance vertical difference ⁇ Y.
  • the R signal processing unit 48R includes a base code generation unit 50R, a rule generation unit 61R, a rule addition unit 62R, an upper and lower code generation unit 70R, and a display code selection unit 80R.
  • the base code generation unit 50R selects a base code having a gradation value larger than the R input gradation and closest to the R input gradation from the base code set, and outputs it as an upper gradation base code.
  • the rule generation unit 61R generates an intermediate code used for displaying an image based on the red image signal and the attribute (attribute associated with the image signal) detected by the attribute detection unit 41. A first rule for changing the lighting subfield to the non-lighting subfield is generated.
  • the rule adding unit 62R calculates the red threshold WRth by dividing the allowable noise level Ynz of luminance by the red luminance conversion coefficient KR, and the subfield having a gradation weight smaller than the calculated red threshold WRth is not turned on Generate a second rule that prohibits
  • the upper and lower code generation unit 70R applies the first rule generated by the rule generation unit 61R and the second rule generated by the rule addition unit 62R to the upper tone base code output from the base code generation unit 50R. Generate intermediate code. An upper gradation code having a gradation value larger than the R input gradation and closest to the R input gradation; and a lower floor code having a gradation value equal to or lower than the R input gradation and closest to the R input gradation. Each key code is selected from the intermediate codes and output.
  • the display code selection unit 80R adds the error and the dither value to the R input gradation, and calculates the gradation value to be displayed on the red discharge cell in the target pixel. Then, of the upper gradation code and the lower gradation code, the one having a gradation value closer to the gradation value to be displayed on the red discharge cell in the target pixel is selected and output as a display code. Further, the display code selection unit 80R calculates a difference between the gradation value to be displayed on the red discharge cell in the target pixel and the gradation value of the display code, and uses the difference as an error for the red discharge cell in the peripheral pixel. Spread.
  • the G signal processing unit 48G and the B signal processing unit 48B have the same configuration as the R signal processing unit 48R and perform the same operation.
  • conversion from an image signal to a display code can be performed by calculation using an arithmetic circuit. Therefore, even in such an image display device, it is not necessary to provide a huge number of conversion tables, and a minimum necessary table (for example, the base code set shown in FIGS. 8A, 8B, and 8C) and an image signal It is only necessary to provide an arithmetic circuit for converting from to display code.
  • an allowable noise level Ynz for luminance is calculated based on the vertical difference ⁇ Y in luminance, and a threshold value for each color is calculated from the allowable noise level Ynz for luminance. Then, a second rule for prohibiting the subfield having a gradation weight smaller than the calculated threshold from being turned off is generated and applied to the selection of the display code. Thereby, the power consumption of the data electrode drive circuit 32 can be suppressed while preventing the image display quality in the image display device 30 from deteriorating.
  • the dither processing and error diffusion processing are performed after setting the subfield for prohibiting the write operation. Therefore, even in the image display device 30 that selects a display code from an intermediate code set having a limited number of subfield codes and uses it to display an image, it is possible to prevent a decrease in image display quality.
  • the conversion from the image signal to the subfield code can be performed by the logical operation, and the data electrode drive circuit is prevented while preventing the image display quality from being deteriorated.
  • the power consumption in 32 can be suppressed.
  • the rule adding unit 62R calculates the red threshold value WRth by dividing the luminance allowable noise level Ynz by the red luminance conversion coefficient KR, and a level smaller than the calculated red threshold value WRth.
  • the example in which the second rule for prohibiting the subfield having the key weight from being turned off has been described.
  • the present invention is not limited to this configuration.
  • the red threshold value WRth may be set as follows using a random number rnd generated between “0” and “1”.
  • WRth Ynz / KR + (W2-W1) ⁇ rnd
  • W2 is the gradation weight of the subfield having the gradation weight closest to (Ynz / KR) and equal to (Ynz / KR) or more.
  • W1 is a gradation weight of a subfield having a gradation weight closest to (Ynz / KR) and less than (Ynz / KR).
  • the rule adding unit 62R may, for example, “subfields from subfield SF1 to subfield SF3 are not lit.
  • the second rule “prohibit” is generated with a probability of 1/2, and the rule “prohibit each subfield from subfield SF1 to subfield SF4 from becoming unlit” has a probability of 1/2 Generate with
  • the second rule by generating the second rule using the random number rnd, the number of intermediate codes generated by the intermediate code generation unit 72R, the intermediate code generation unit 72G, and the intermediate code generation unit 72B is continuously controlled. be able to. Therefore, for example, even when the power control signal Cnt continuously changes, it is difficult for the user to visually recognize the change in the image display quality.
  • the configuration in which the base code generation unit 50R has the base code storage unit 52R and the base code set is stored in the base code storage unit 52R in advance has been described.
  • the present invention is not limited to this configuration.
  • a configuration may be adopted in which a rule for generating a base code is determined in advance and the base code is generated based on the rule. The same applies to the base code generation unit 50G and the base code generation unit 50B.
  • the upper and lower code generation unit 70R selects the upper gradation code and the lower gradation code by the upper and lower code selection unit 74R after the intermediate code set is generated by the intermediate code generation unit 72R.
  • the present invention is not limited to this configuration.
  • an intermediate code is generated in order of increasing gradation value, and at the same time, the intermediate code and the input gradation are sequentially compared to select the upper gradation code and the lower gradation code.
  • the present invention is not limited to this configuration.
  • the dither selection unit 82R can be omitted.
  • the error diffusion unit 84R can be omitted.
  • the image display quality may be lowered, so care must be taken. The same applies to the display code selection unit 80G and the display code selection unit 80B.
  • the number of subfields constituting one field, the subfields that are forced initialization subfields, the gradation weights of each subfield, and the like are not limited to the above-described numerical values. Moreover, the structure which switches a subfield structure based on an image signal etc. may be sufficient.
  • the drive voltage waveform shown in FIG. 3 is merely an example in the embodiment of the present invention, and the present invention is not limited to this drive voltage waveform.
  • circuit configurations shown in FIGS. 5, 6, and 7 are merely examples in the embodiment of the present invention, and the present invention is not limited to these circuit configurations.
  • each circuit block shown in the embodiment of the present invention may be configured as an electric circuit that performs each operation shown in the embodiment, or a microcomputer that is programmed to perform the same operation. May be used.
  • the number of subfields constituting one field is not limited to the above number.
  • the number of gradations that can be displayed on the panel 10 can be further increased.
  • the time required for driving panel 10 can be shortened by reducing the number of subfields.
  • one pixel is constituted by discharge cells of three colors of red, green, and blue.
  • a panel in which one pixel is constituted by discharge cells of four colors or more has been described.
  • the specific numerical values shown in the embodiment of the present invention are set based on the characteristics of the panel 10 having a screen size of 50 inches and the number of display electrode pairs 14 of 1024. It is just an example.
  • the present invention is not limited to these numerical values, and each numerical value is desirably set optimally in accordance with panel specifications, panel characteristics, plasma display device specifications, and the like. Each of these numerical values is allowed to vary within a range where the above-described effect can be obtained.
  • the number of subfields constituting one field, the gradation weight of each subfield, and the like are not limited to the values shown in the embodiment of the present invention, and the subfield configuration is based on an image signal or the like. May be configured to switch.
  • the present invention since conversion from an image signal to a subfield code can be performed by calculation, it is not necessary to use a conversion table composed of a large number of subfield codes, and power consumption can be prevented while preventing deterioration in image display quality. Therefore, the present invention is useful as an image display device that displays an image in an image display region by combining binary control of light emission and non-light emission in a light emitting element that constitutes a pixel, and a driving method of the image display device.

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Abstract

Selon l'invention, la conversion d'un signal d'image en un code de sous-champ dans un dispositif de visualisation d'image est calculée sans recours à une table de conversion. A cette fin, le dispositif de visualisation d'image comprend une unité de calcul de bruit acceptable, un processeur de signal d'image rouge, un processeur de signal d'image verte, et un processeur de signal d'image bleue. L'unité de calcul de bruit acceptable calcule la différence du signal d'image pour chaque couleur, entre des pixels adjacents, dans la direction où s'étend une électrode de données; calcule une différence de niveau de luminosité; et calcule un niveau de bruit acceptable pour la luminosité, sur la base de cette différence de niveau de luminosité. Le processeur de signal d'image rouge calcule un seuil rouge à partir du niveau de bruit acceptable pour la luminosité et un coefficient de conversion de luminosité, et génère un code d'affichage rouge au moyen d'un code de sous-champ destiné à empêcher qu'un sous-champ présentant un poids de gradient inférieur à celui du seuil rouge ne devienne non émetteur. Le processeur de signal d'image verte et le processeur de signal d'image bleue présentent la même configuration que le processeur de signal d'image rouge.
PCT/JP2012/000298 2011-01-20 2012-01-19 Dispositif de visualisation d'image et procédé de commande pour dispositif de visualisation d'image WO2012098887A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007041251A (ja) * 2005-08-03 2007-02-15 Matsushita Electric Ind Co Ltd プラズマディスプレイパネルの駆動方法
JP2007041474A (ja) * 2005-08-05 2007-02-15 Matsushita Electric Ind Co Ltd 画像表示方法
JP2008257055A (ja) * 2007-04-06 2008-10-23 Hitachi Ltd マトリックス表示装置
JP2010139689A (ja) * 2008-12-11 2010-06-24 Panasonic Corp プラズマディスプレイ装置の駆動方法

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007041251A (ja) * 2005-08-03 2007-02-15 Matsushita Electric Ind Co Ltd プラズマディスプレイパネルの駆動方法
JP2007041474A (ja) * 2005-08-05 2007-02-15 Matsushita Electric Ind Co Ltd 画像表示方法
JP2008257055A (ja) * 2007-04-06 2008-10-23 Hitachi Ltd マトリックス表示装置
JP2010139689A (ja) * 2008-12-11 2010-06-24 Panasonic Corp プラズマディスプレイ装置の駆動方法

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