JP2007322901A - Display device and method for driving the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device that is free from degradation of image display quality while changing the luminance of a backlight according to the total brightness of a display screen. <P>SOLUTION: The display device includes a display unit comprising a transmissive liquid crystal display device, a backlight illuminating the back face of the display unit, and a driving unit. The driving unit inspects whether an average of the whole input signals is equal to or larger than a predetermined value or not; when the average of the whole entire input signals is equal to or larger than the predetermined value, the driving unit renders the exponent in the γ correction of input signals into γ<SB>11</SB>and controls the luminance of the back light to Y<SB>11</SB>; and when the average of the whole entire input signals is less than the predetermined value, the driving unit renders the exponent in the γ correction of the input signals into γ<SB>12</SB>(wherein γ<SB>12</SB>>γ<SB>11</SB>) and controls the luminance of the backlight to Y<SB>12</SB>(wherein Y<SB>12</SB>>Y<SB>11</SB>). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a display device including a display unit including a liquid crystal display device and a backlight, and a driving method thereof.

  In the liquid crystal display device, the liquid crystal material itself does not emit light. Accordingly, for example, a direct type backlight is disposed on the back surface of the liquid crystal display device. In the color liquid crystal display device, one pixel includes, for example, three sub-pixels of a red light-emitting sub pixel, a green light-emitting sub pixel, and a blue light-emitting sub pixel. Then, by operating the liquid crystal cell constituting each pixel or each sub-pixel as a kind of light shutter (light valve), that is, controlling the light transmittance (aperture ratio) of each pixel or each sub-pixel, An image is displayed by controlling the light transmittance of illumination light (for example, white light) emitted from the backlight.

  Conventionally, the backlight illuminates the entire liquid crystal display device with uniform and constant brightness. However, the backlight has a different configuration, that is, a plurality of display areas in the liquid crystal display device. For example, Japanese Patent Application Laid-Open No. 2005-258403 discloses a backlight that includes a plurality of light source units corresponding to the display area unit and has a configuration for changing the illuminance distribution in the display area unit.

Such a backlight is controlled based on the method described below. A control signal for controlling the light transmittance of the pixel is supplied from the drive unit to each pixel based on an input signal input from the outside to the drive unit. That is, the maximum luminance of each light source unit constituting the backlight is Y _max, and the maximum value (specifically, for example, 100%) of the light transmittance (aperture ratio) of the pixel in the display area unit is L t _max . . Further, when each light source unit constituting the backlight has the maximum luminance Y _max , the light transmittance (aperture ratio) of each pixel for obtaining the display luminance y ₀ of each pixel in the display area unit is expressed as Lt ₀ . To do. Then, in this case, the light source luminance Y ₀ of each light source unit constituting the backlight is
Y ₀ · Lt _max = Y _max · Lt ₀
It may be controlled so as to satisfy In addition, the conceptual diagram of such control is shown to (A) and (B) of FIG. Here, the light source luminance Y ₀ of the light source unit is changed for each frame (referred to as an image display frame for convenience) in the image display of the liquid crystal display device.

  Such backlight control (also referred to as backlight split driving) can increase the white level in the liquid crystal display device and increase the contrast ratio due to the decrease in the black level. As a result, the quality of the image display can be improved. Improvement can be achieved and power consumption of the backlight can be reduced.

  In addition, as described in May 2005, Optoelectronic Industry and Technology Promotion Association, 2004 FY-003 Optical Technology Trend Survey Report, page 313, a television having a conventional cathode ray tube. The John receiver is equipped with an automatic beam limit circuit (Auto Beam Limit circuit, ABL circuit) and an automatic power limit circuit (Auto Power Limit circuit, APL circuit) to limit the load factor, and the entire display screen is white. In the case of display, the brightness is lowered in order to prevent an excessive increase in power and an adverse effect on the device life. On the contrary, if the area of the display screen that displays white is small, the luminance of the portion of the display screen that displays white is relatively increased compared to the case where the entire display screen displays white. Brings a sense of brightness to the image. For broadcast waves and the like, picture creation (video signal generation) is performed on the premise of the characteristics of a television receiver having such a conventional cathode ray tube. Therefore, the video signal carried by the broadcast wave is set so that the luminance of the portion of the display screen that displays white is high (RGB value is large).

JP-A-2005-258403 May 2005, Optoelectronic Industry and Technology Promotion Association, page 313 of the 2004 FY-003 Optical Technology Trend Survey Report (http://www.oitda.or.jp/main/technology/ technology2004.html)

  By the way, the current color liquid crystal display device normally reproduces the video signal carried by the broadcast wave as it is, so that the luminance of the backlight light source can be increased regardless of whether the area of the display screen displaying white is small or large. The display brightness in the color liquid crystal display device is the same, and there is a problem that the white image portion is not particularly bright.

As described above, the input signal when the brightness of the entire display screen is relatively dark and a high-luminance display portion such as a portion of the display screen displaying white is present is schematically shown in FIG. The light source luminance of the backlight at this time is “Y” as schematically shown in FIG. 10B, and the display luminance at this time is schematically “y _H ” as shown in FIG. 10C. , “Y _L ”. Then, when the backlight brightness is simply increased from the state schematically shown in FIG. 10B, as schematically shown by the dotted line as the light source brightness “Y ′” in FIG. In addition, the display brightness of the high brightness display portion becomes “y _H '” as shown by the dotted line, and the display brightness of the black display portion (high brightness display portion) becomes “y _L '” as shown by the dotted line. As a result, the image becomes brighter and the image display quality is degraded.

  Therefore, the first object of the present invention is to cause a problem that the black display portion becomes brighter and the image display quality is deteriorated while changing the luminance of the backlight according to the brightness of the entire display screen. It is an object of the present invention to provide a display device having a configuration that can be avoided and a driving method thereof. The second object of the present invention is to display an image by changing the brightness of the backlight while the brightness of the backlight is changed according to the brightness of the entire display screen, and when the brightness of the backlight is changed. It is an object of the present invention to provide a display device having a configuration capable of avoiding the occurrence of a problem that the quality of the display device deteriorates and a driving method thereof.

The display device according to the first aspect of the present invention for achieving the first object, or the display device in the method for driving the display device according to the first aspect of the present invention,
(A) a display unit composed of a transmissive liquid crystal display device having a display area composed of pixels arranged in a matrix;
(B) a backlight for illuminating the back surface of the display unit, and
(C) a drive unit that controls and drives the display unit and the backlight based on an external input signal;
Is a display device.

In the display device according to the first aspect of the present invention, the drive unit is
Check whether the average value of all input signals is greater than or equal to a predetermined value,
If the average value of all the input signals is a predetermined value or more, the exponent and gamma ₁₁ in gamma correction of the input signal, and to control the luminance of the backlight to Y _11,
When the average value of all input signals is less than a predetermined value, the power index in the γ correction of the input signal is γ ₁₂ (where γ ₁₂ > γ ₁₁ ), and the backlight brightness is Y ₁₂ (where Y ₁₂ > Y ₁₁ ).

In the driving method of the display device according to the first aspect of the present invention,
Check whether the average value of all input signals is equal to or greater than a predetermined value or not in the drive unit,
When the average value of all the input signals is equal to or greater than a predetermined value, the driving unit controls the power index in the γ correction of the input signal to γ ₁₁ and the backlight brightness to Y ₁₁ ,
When the average value of all the input signals is less than a predetermined value, the driving unit sets the power exponent in the γ correction of the input signal to γ ₁₂ (where γ ₁₂ > γ ₁₁ ), and the luminance of the backlight is Y _12. (However, Y ₁₂ > Y ₁₁ ).

The display device according to the second aspect of the present invention for achieving the second object, or the display device in the method for driving the display device according to the second aspect of the present invention,
(A) a display unit composed of a transmissive liquid crystal display device having a display area composed of pixels arranged in a matrix;
(B) a light source unit individually arranged corresponding to a plurality of display area units constituting the display area, a backlight for illuminating the back surface of the display unit, and
(C) a drive unit that controls and drives the display unit and the backlight based on an external input signal;
With
The drive unit is a display device that controls the light emission state of the light source unit corresponding to the display area unit based on the in-display area unit / maximum input signal having the maximum value among the input signals corresponding to each display area unit. .

And in the display apparatus which concerns on the 2nd aspect of this invention, a drive part is
(A) Check whether the average value of all input signals is equal to or greater than a predetermined value,
(B-1) When the average value of all input signals is greater than or equal to a predetermined value, the power index in the γ correction of the input signals corresponding to each display area unit is γ ₂₁ and the light source corresponding to the display area unit Control the brightness of the unit based on the value of the maximum input signal in the display area unit,
(B-2) When the average value of all input signals is less than a predetermined value,
In the display area unit in the display area unit and the value of the maximum input signal is equal to or greater than the specified value, the power index in the γ correction of the input signal corresponding to the display area unit is γ ₂₂ (where γ ₂₂ > γ ₂₁ ). And the brightness of the light source unit corresponding to the display area unit is controlled to be higher than the brightness based on the value of the maximum input signal in the display area unit,
In the display area unit, the value of the maximum input signal in the display area unit is less than the specified value. The input index corresponding to the display area unit is γ ₂₁ in the γ correction and corresponds to the display area unit. The luminance of the light source unit is controlled to the luminance based on the value of the maximum input signal in the display area unit.

In the display device driving method according to the second aspect of the present invention,
(A) The drive unit checks whether the average value of all input signals is equal to or greater than a predetermined value,
If the average value of (B-1) the total input signal is a predetermined value or more, in the drive unit, and gamma ₂₁ the exponent in the gamma correction of the input signal corresponding to each display area unit, and, the display area units Control the brightness of the light source unit corresponding to the brightness based on the value of the maximum input signal in the display area unit,
(B-2) When the average value of all input signals is less than a predetermined value,
In the display area unit, in the display area unit in which the value of the maximum input signal is equal to or greater than the specified value, the driving unit sets the power exponent in the γ correction of the input signal corresponding to the display area unit to γ ₂₂ (where γ ₂₂ > γ ₂₁ ), and the luminance of the light source unit corresponding to the display area unit is controlled to be higher than the luminance based on the value of the maximum input signal in the display area unit,
In the display area unit, in the display area unit in which the value of the maximum input signal is less than the specified value, the driving unit sets the power index in the γ correction of the input signal corresponding to the display area unit to γ ₂₁ , and The brightness of the light source unit corresponding to the display area unit is controlled to be based on the value of the maximum input signal in the display area unit.

In the following description of the display device or the driving method thereof according to the second aspect of the present invention (hereinafter, these may be collectively referred to simply as the second aspect of the present invention), a plurality of display areas A unit (this display area unit is a virtual one) may be referred to as P × Q display area units. In this case, the number of light source units is P × Q. Further, in an input signal corresponding to one display area unit (the number of input signals is equal to the number of pixels constituting this display area unit, or alternatively, the number of sub-pixels constituting this display area unit). The value of the maximum input signal in the display area unit may be expressed as “x _U-max ”. Furthermore, the maximum value among the values x _U-max of the display area unit / maximum input signal (the number of display area units / maximum input signals is P × Q) is expressed as “x _MAX ”. There is a case.

When the liquid crystal display device is a color liquid crystal display device, one pixel is composed of, for example, three subpixels of a red light emitting subpixel, a green light emitting subpixel, and a blue light emitting subpixel. Accordingly, the input signal is also a set of three input signals: an input signal for the red light emitting subpixel, an input signal for the green light emitting subpixel, and an input signal for the blue light emitting subpixel. In this case, the value (x _U-max ) within the display area unit is the value of the input signal for the maximum red light emission subpixel and the maximum green light emission subpixel in one display area unit. It refers to the maximum value of the input signal value for the pixel and the input signal value for the largest blue-emitting subpixel.

  The light transmittance (also referred to as aperture ratio) Lt of a pixel or sub-pixel, the luminance (display luminance) y of the portion of the display area unit corresponding to the pixel or sub-pixel, and the luminance (light source luminance) Y of the light source unit are as follows: Define as follows.

Y ₁ ... The light source luminance in the normal operating state (when the power index in the γ correction of the input signal is γ ₁₁ or γ ₂₁ ), for example, the maximum luminance, and hereinafter, the light source luminance and the first specified value Sometimes called.
Lt ₁ ... Is the maximum value of the light transmittance (aperture ratio) of a pixel or sub-pixel in the display area or display area unit, for example, and may hereinafter be referred to as the light transmittance / first specified value.
Lt ₂ ... In the second aspect of the present invention, when the light source luminance is the light source luminance and the first specified value Y ₁ , it corresponds to the display area unit and the maximum input signal (value: x _U-max ). The light transmittance (aperture ratio) of the pixel or sub-pixel when it is assumed that the control signal is supplied to the pixel or sub-pixel, and may be hereinafter referred to as the light transmittance / second specified value. In addition, 0 ≦ Lt ₂ ≦ Lt ₁
y ₂ ... In the second aspect of the present invention, the light source luminance is the light source luminance and the first specified value Y ₁ , and the light transmittance (aperture ratio) of the pixel or sub-pixel is the light transmittance or the second specified value. This is the display luminance obtained when it is assumed that the value Lt ₂ , and may be hereinafter referred to as “display luminance / second prescribed value”.
Y ₂ ... In the second aspect of the present invention, it is assumed that a control signal corresponding to the maximum input signal (value: x _U-max ) in the display area unit is supplied to the pixel or sub-pixel, Assuming that the light transmittance (aperture ratio) of the pixel or sub-pixel at this time is corrected to the light transmittance / first specified value Lt ₁ , the luminance of the pixel or sub-pixel is set to the display brightness / second specified value (y ₂ ) The light source brightness of the light source unit. However, the light source luminance Y ₂ may be corrected in consideration of the influence of the light source luminance of each light source unit on the light source luminance of other light source units.

Here, “2.2” can be exemplified as the values of γ ₁₁ and γ ₂₁ . In this case, the luminance Y ₁₁ of the backlight may be set to the light source luminance / first specified value Y ₁ , or the luminance Y ₂₁ of the light source unit corresponding to the display area unit is set in the display area unit. The light source luminance Y ₂ that is the luminance based on the value of the maximum input signal may be used.

  In the second aspect of the present invention including the preferred mode and configuration described above, one light source unit is surrounded by four light source units, or alternatively, one of three light source units and a casing (described later). Surrounded by side surfaces, or alternatively, surrounded by two light source units and two side surfaces of the housing.

  In the display device or the driving method thereof according to the first to second aspects of the present invention including the preferred embodiments and configurations described above (hereinafter, these may be collectively referred to simply as the present invention). As the light source of the backlight or the light source unit constituting the backlight, a light emitting diode (LED) can be cited, or a cold cathode fluorescent lamp, an electroluminescence (EL) device, A cathode field electron emission device (FED), a plasma display device, and a normal lamp can also be mentioned. When the light source is composed of a light emitting diode, for example, a red light emitting diode that emits red light with a wavelength of 640 nm, for example, a green light emitting diode that emits green light with a wavelength of 530 nm, and a blue light emitting diode that emits blue light with a wavelength of 450 nm, for example. It can be configured to obtain white light, or white light can be obtained by light emission of a white light emitting diode (for example, a light emitting diode that emits white light by combining an ultraviolet or blue light emitting diode and phosphor particles). You may further provide the light emitting diode which light-emits 4th color other than red, green, blue, 5th color ....

  When the light source is composed of light emitting diodes, a plurality of red light emitting diodes that emit red light, a plurality of green light emitting diodes that emit green light, and a plurality of blue light emitting diodes that emit blue light are arranged and arranged in a housing. Has been. More specifically, (one red light emitting diode, one green light emitting diode, one blue light emitting diode), (one red light emitting diode, two green light emitting diodes, one blue light emitting diode), (two red light emitting diodes) A light source can be composed of a light emitting diode unit composed of a combination of a light emitting diode, two green light emitting diodes, and one blue light emitting diode). In this case, at least one light emitting diode unit is provided in the backlight or one light source unit.

  The light emitting diode may have a so-called face-up structure or a flip chip structure. That is, the light-emitting diode includes a substrate and a light-emitting layer formed on the substrate, and may have a structure in which light is emitted from the light-emitting layer to the outside, or light from the light-emitting layer passes through the substrate. It is good also as a structure radiate | emitted outside. More specifically, the light emitting diode (LED) is formed on, for example, a first cladding layer and a first cladding layer made of a compound semiconductor layer having a first conductivity type (for example, n-type) formed on a substrate. The active layer, and a second clad layer stack structure comprising a compound semiconductor layer having a second conductivity type (for example, p-type) formed on the active layer, and electrically connected to the first clad layer. One electrode and a second electrode electrically connected to the second cladding layer are provided. The layer constituting the light emitting diode may be made of a known compound semiconductor material depending on the emission wavelength.

  In the present invention, an optical sensor for measuring the light emission state of the light source (specifically, for example, the luminance of the light source, or the chromaticity of the light source, or the luminance and chromaticity of the light source) is provided. It is desirable that The number of photosensors may be at least one, but a configuration in which one set of photosensors is arranged in one light source unit makes it possible to reliably measure the light emission state of each light source unit. Desirable from. As the optical sensor, a known photodiode or CCD device can be cited. When the light source is configured, for example, as a set of a red light emitting diode, a green light emitting diode, and a blue light emitting diode, the light emission state of the light source measured by the optical sensor is the luminance and chromaticity of the light source. Also, in this case, a pair of photosensors is connected to a photodiode with a red filter attached to measure the light intensity of red light, a photodiode attached with a green filter to measure the light intensity of green light, And, it can be composed of a photodiode with a blue filter attached to measure the light intensity of blue light.

  The drive unit includes, for example, a control circuit (backlight control circuit, and a pulse width modulation (PWM) signal generation circuit, a duty ratio control circuit, a light emitting diode (LED) drive circuit, an arithmetic circuit, a storage device (memory), etc. Light source unit driving circuit) and a liquid crystal display device driving circuit including a known circuit such as a timing controller.

  The backlight can be configured to further include an optical function sheet group such as a diffusion plate, a diffusion sheet, a prism sheet, and a polarization conversion sheet, and a reflection sheet.

  Control of pixel brightness (display brightness) and backlight or light source unit brightness (light source brightness) is performed for each image display frame. Note that the number of image information (images per second) sent as electrical signals to the drive unit per second is the frame frequency (frame rate), and the inverse of the frame frequency is the frame time (unit: seconds).

  The transmissive liquid crystal display device includes, for example, a front panel having a transparent first electrode, a rear panel having a transparent second electrode, and a liquid crystal material disposed between the front panel and the rear panel. Consists of.

  More specifically, the front panel includes, for example, a first substrate made of, for example, a glass substrate or a silicon substrate, and a transparent first electrode (also called a common electrode, for example, ITO provided on the inner surface of the first substrate. And a polarizing film provided on the outer surface of the first substrate. Further, in the transmissive color liquid crystal display device, a color filter covered with an overcoat layer made of acrylic resin or epoxy resin is provided on the inner surface of the first substrate. Examples of the color filter arrangement pattern include a delta arrangement, a stripe arrangement, a diagonal arrangement, and a rectangle arrangement. The front panel further has a configuration in which a transparent first electrode is formed on the overcoat layer. An alignment film is formed on the transparent first electrode. On the other hand, the rear panel more specifically includes, for example, a second substrate made of a glass substrate or a silicon substrate, a switching element formed on the inner surface of the second substrate, and conduction / non-conduction by the switching element. A transparent second electrode to be controlled (also called a pixel electrode, which is made of, for example, ITO) and a polarizing film provided on the outer surface of the second substrate. An alignment film is formed on the entire surface including the transparent second electrode. Various members and liquid crystal materials constituting the liquid crystal display device including these transmissive color liquid crystal display devices can be formed of known members and materials. Examples of the switching element include a three-terminal element such as a MOS type FET and a thin film transistor (TFT) formed on a single crystal silicon semiconductor substrate, and a two-terminal element such as an MIM element, a varistor element, and a diode.

  An area where the transparent first electrode and the transparent second electrode overlap and includes a liquid crystal cell corresponds to one pixel (pixel) or one sub-pixel (sub-pixel). In the transmissive color liquid crystal display device, the red light emitting sub-pixel (sub-pixel [R]) that constitutes each pixel (pixel) is composed of a combination of the region and a color filter that transmits red, and green. The light emitting sub-pixel (sub-pixel [G]) is composed of a combination of the region and a color filter that transmits green, and the blue light-emitting sub-pixel (sub-pixel [B]) is a color filter that transmits the region and blue. It is comprised from the combination. The arrangement pattern of the sub-pixel [R], sub-pixel [G], and sub-pixel [B] matches the arrangement pattern of the color filter described above. The pixel is not limited to a configuration in which three sub-pixels of a red light-emitting subpixel, a green light-emitting subpixel, and a blue light-emitting subpixel are configured as one set. Alternatively, one set including a plurality of sub-pixels (for example, one set including a sub-pixel emitting white light for improving luminance, one set adding a sub-pixel emitting sub-color to expand a color reproduction range, In order to expand the color reproduction range, one set including a sub-pixel emitting yellow and one set including a sub-pixel emitting yellow and cyan in order to expand the color reproduction range may be used.

When expressed as the number M ₀ × N ₀ of a matrix in pixels arranged _{(pixels) (M 0, N 0)} , the value of (M _0, N _0), specifically, VGA (640, 480), S-VGA (800, 600), XGA (1024, 768), APRC (1152, 900), S-XGA (1280, 1024), U-XGA (1600, 1200), HD-TV (1920, 1080), Q-XGA (2048, 1536), (1920, 1035), (720, 480), (1280, 960), and some other image display resolutions. It is not limited to values. Further, the relationship between the value of (M ₀ , N ₀ ) and the value of (P, Q) is not limited, but can be exemplified in Table 1 below. Examples of the number of pixels constituting one display area unit include 20 × 20 to 320 × 240, preferably 50 × 50 to 200 × 200. The number of pixels in the display area unit may be constant or different.

  In the first aspect or the second aspect of the present invention, when the brightness of the entire display screen is relatively dark, the luminance of the backlight is increased while the power index in the γ correction of the input signal is increased. The display screen portion that should be displayed brighter can be displayed brighter, and the increase in the brightness of the black display portion can be suppressed, resulting in a problem that the image display quality deteriorates. It can be avoided reliably.

Furthermore, in the second aspect of the present invention, for example, it is assumed that a control signal corresponding to an input signal having a value equal to the value x _U-max in the display area unit / maximum input signal is supplied to the pixel. The brightness of the light source constituting the light source unit corresponding to the display area unit is driven so that the brightness of the pixel (light transmittance, display brightness at the first specified value Lt ₁ , second specified value y ₂ ) is obtained. Because it controls the power consumption of the backlight, not only can the power consumption of the backlight be reduced, but the white level can be increased or the black level can be decreased, and a high contrast ratio (external light reflection on the screen surface of the liquid crystal display device) can be achieved. (Brightness ratio of the all-black display portion and all-white display portion) not included, and the brightness of a desired display area can be emphasized, so that the quality of image display can be improved. .

  Hereinafter, with reference to the drawings, the display device of the present invention will be described based on examples, but prior to that, an outline of a display unit and a backlight composed of a transmissive color liquid crystal display device suitable for use in the examples, This will be described with reference to FIGS. 4, 5, and 6A and 7B, and FIG.

As shown in a conceptual diagram of FIG. 4, the transmissive color liquid crystal display device 10 of which corresponds to the display unit, ₀ M along a first direction, N ₀ along the second direction, the total M A display area 11 in which ₀ × N ₀ pixels are arranged in a matrix is provided. In the display device suitable for use in the second embodiment, it is assumed that the display area 11 is divided into P × Q virtual display area units 12. The display area 11 or each display area unit 12 is composed of a plurality of pixels. Specifically, for example, the image display resolution satisfies the HD-TV standard, and the number M ₀ × N ₀ of pixels (pixels) arranged in a matrix is expressed as (M ₀ , N ₀ ). For example, (1920, 1080).

  Further, in the display device suitable for use in the second embodiment, the display area 11 (shown by a one-dot chain line in FIG. 4) composed of pixels arranged in a matrix has P × Q virtual images. It is divided into display area units 12 (the boundaries are indicated by dotted lines). The value of (P, Q) is (19, 12), for example. However, in order to simplify the drawing, the number of display area units 12 (and light source units 42 described later) in FIG. 4 is different from this value. Each display area unit 12 is composed of a plurality of (M × N) pixels, and the number of pixels constituting one display area unit 12 is, for example, about 10,000.

  Each pixel is configured as a set of a plurality of sub-pixels that emit different colors. More specifically, each pixel has three light emitting subpixels (subpixel [R]), a green light emitting subpixel (subpixel [G]), and a blue light emitting subpixel (subpixel [B]). It consists of sub-pixels (sub-pixels). The transmissive color liquid crystal display device 10 is line-sequentially driven. More specifically, the color liquid crystal display device 10 includes scan electrodes (extending along the first direction) and data electrodes (extending along the second direction) that intersect in a matrix. Then, a scanning signal is input to the scanning electrode to select and scan the scanning electrode, and an image is displayed based on the data signal (a signal based on the control signal) input to the data electrode to constitute one screen.

  The color liquid crystal display device 10 includes a front panel 20 provided with a transparent first electrode 24, a rear panel 30 provided with a transparent second electrode 34, and a schematic partial sectional view shown in FIG. The liquid crystal material 13 is disposed between the front panel 20 and the rear panel 30.

  The front panel 20 includes, for example, a first substrate 21 made of a glass substrate and a polarizing film 26 provided on the outer surface of the first substrate 21. A color filter 22 covered with an overcoat layer 23 made of acrylic resin or epoxy resin is provided on the inner surface of the first substrate 21, and a transparent first electrode (also called a common electrode) is provided on the overcoat layer 23. (For example, made of ITO) 24 is formed, and an alignment film 25 is formed on the transparent first electrode 24. On the other hand, the rear panel 30 more specifically includes, for example, a second substrate 31 made of a glass substrate, and switching elements (specifically, thin film transistors and TFTs) formed on the inner surface of the second substrate 31. 32, a transparent second electrode (also referred to as a pixel electrode, made of, for example, ITO) 34 whose conduction / non-conduction is controlled by the switching element 32, and a polarizing film 36 provided on the outer surface of the second substrate 31, It is composed of An alignment film 35 is formed on the entire surface including the transparent second electrode 34. The front panel 20 and the rear panel 30 are joined via a sealing material (not shown) at their outer peripheral portions. Note that the switching element 32 is not limited to a TFT, and may be composed of, for example, an MIM element. Reference numeral 37 in the drawing is an insulating layer provided between the switching element 32 and the switching element 32.

  Since various members and liquid crystal materials constituting these transmissive color liquid crystal display devices can be composed of well-known members and materials, detailed description thereof is omitted.

  In the display device suitable for use in the first embodiment, the backlight (directly-type planar light source device) 40 illuminates the display area 11 from the back surface. In the display device suitable for use in the second embodiment, the backlight (directly-type planar light source device) 40 is individually arranged corresponding to the P × Q virtual display area units 12. The light source units 42 illuminate the display area unit 12 corresponding to the light source units 42 from the back side. The light sources provided in the light source unit 42 are individually controlled.

    Although the backlight 40 is positioned below the color liquid crystal display device 10, the color liquid crystal display device 10 and the backlight 40 are separately displayed in FIG. The arrangement and arrangement of light emitting diodes and the like in the backlight 40 are schematically shown in FIG. 6A, and a schematic partial sectional view of the display device including the color liquid crystal display device 10 and the backlight 40 is shown in FIG. Shown in (B). The light source includes a light emitting diode 41 driven based on a pulse width modulation (PWM) control method.

  As shown in the schematic partial cross-sectional view of the display device in FIG. 6B, the backlight 40 includes a housing 51 having an outer frame 53 and an inner frame 54. The end of the transmissive color liquid crystal display device 10 is held by the outer frame 53 and the inner frame 54 so as to be sandwiched between the spacers 55A and 55B. A guide member 56 is disposed between the outer frame 53 and the inner frame 54 so that the color liquid crystal display device 10 sandwiched between the outer frame 53 and the inner frame 54 does not shift. A diffusion plate 61 is attached to the inner frame 54 via a spacer 55 </ b> C and a bracket member 57 in the upper portion of the housing 51. On the diffusion plate 61, an optical function sheet group such as a diffusion sheet 62, a prism sheet 63, and a polarization conversion sheet 64 is laminated.

  A reflection sheet 65 is provided inside and below the housing 51. Here, the reflection sheet 65 is disposed so that the reflection surface thereof faces the diffusion plate 61, and is attached to the bottom surface 52 </ b> A of the housing 51 via an attachment member (not shown). The reflection sheet 65 can be composed of, for example, a silver-enhanced reflection film having a structure in which a silver reflection film, a low refractive index film, and a high refractive index film are sequentially laminated on a sheet base material. The reflection sheet 65 reflects the light emitted from the plurality of light emitting diodes 41 (light sources 41), the light reflected by the side wall 52B of the housing 51, or in some cases, the partition wall 44 shown in FIG. reflect. Thus, the light is emitted from a plurality of red light emitting diodes 41R (light source 41R) that emits red light, a plurality of green light emitting diodes 41G (light source 41G) that emits green light, and a plurality of blue light emitting diodes 41B (light source 41B) that emit blue light. The red light, green light, and blue light thus mixed are mixed, and white light with high color purity can be obtained as illumination light. The illumination light passes through the optical function sheet group such as the diffusion plate 61, the diffusion sheet 62, the prism sheet 63, and the polarization conversion sheet 64, and irradiates the color liquid crystal display device 10 from the back side. The light source unit 42 and the light source unit 42 constituting the backlight 40 are partitioned by a partition wall 44. The partition wall 44 is attached to the bottom surface 52 </ b> A of the housing 51 via an attachment member (not shown). In the display device suitable for use in the first embodiment, the partition wall 44 may not be provided.

  In the vicinity of the bottom surface 52A of the housing 51, photodiodes 43R, 43G, and 43B, which are optical sensors, are arranged. The photodiode 43R is a photodiode with a red filter attached to measure the light intensity of red light, and the photodiode 43G is a photo diode with a green filter attached to measure the light intensity of green light. The photodiode 43B is a photodiode to which a blue filter is attached in order to measure the light intensity of blue light. Here, for example, one light sensor (photodiode 43R, 43G, 43B) is disposed in one light source unit. The light emission states of the light sources 41R, 41G, and 41B measured by the photodiodes 43R, 43G, and 43B that are optical sensors are the luminance and chromaticity of the light emitting diodes 41R, 41G, and 41B.

  The arrangement state of the light emitting diodes 41R, 41G, and 41B includes, for example, a red light emitting diode 41R that emits red light (for example, a wavelength of 640 nm), a green light emitting diode 41G that emits green light (for example, a wavelength of 530 nm), and a blue light (for example, A plurality of light emitting diode units each including a blue light emitting diode 41B that emits light having a wavelength of 450 nm may be arranged in a horizontal direction and a vertical direction. In this case, in the display device suitable for use in the second embodiment, one light emitting diode unit is arranged in one light source unit 42.

As shown in FIGS. 4 and 5, the driving unit for driving the backlight 40 and the color liquid crystal display device 10 based on an input signal from the outside (display circuit) is based on the pulse width modulation control method. The light emitting diode 41R, the green light emitting diode 41G, and the blue light emitting diode 41B are configured by a backlight control circuit 70 and a light source unit driving circuit 80 that perform on / off control, and a liquid crystal display device driving circuit 90. The backlight control circuit 70 includes an arithmetic circuit 71 and a storage device (memory) 72. In the display device suitable for use in the first embodiment, only one light source unit drive circuit 80 is required. In the display device suitable for use in the second embodiment, based on the display area unit maximum input signal having the maximum value x _U-max among the input signals corresponding to each display area unit 12, The light emission state of the light source unit 42 corresponding to the display area unit 12 is controlled.

  The light source unit driving circuit 80 includes an arithmetic circuit 81, a storage device (memory) 82, an LED driving circuit 83, a photodiode control circuit 84, switching elements 85R, 85G, and 85B composed of FETs, and a light emitting diode driving power source (constant current source). 86). These circuits constituting the backlight control circuit 70 and the light source unit driving circuit 80 can be known circuits.

On the other hand, a liquid crystal display device driving circuit 90 for driving the color liquid crystal display device 10 includes a known circuit such as a timing controller 91. The color liquid crystal display device 10 is provided with a gate driver, a source driver, and the like (not shown) for driving the switching element 32 formed of a TFT constituting the liquid crystal cell. The light emitting states of the light emitting diodes 41R, 41G, and 41B in an image display frame are measured by the photodiodes 43R, 43G, and 43B, and the outputs from the photodiodes 43R, 43G, and 43B are input to the photodiode control circuit 84, and the photo In the diode control circuit 84 and the arithmetic circuit 81, for example, data (signals) as the luminance and chromaticity of the light emitting diodes 41R, 41G, and 41B are transmitted to the LED driving circuit 83, and light emission in the next image display frame is performed. A feedback mechanism is formed in which the light emission states of the diodes 41R, 41G, and 41B are controlled. Further, resistors r _R , r _G , r _B for current detection are inserted in series with the light emitting diodes 41R, 41G, 41B downstream of the light emitting diodes 41R, 41G, 41B, and the resistors r _R , r The operation of the light-emitting diode drive power supply 86 is controlled under the control of the LED drive circuit 83 so that the currents flowing through _{G 1} and r _B are converted into voltages, and the voltage drops in the resistors r _R , r _G and r _B have predetermined values. Is controlled. Here, FIG. 5 shows one light emitting diode driving power source (constant current source) 86, but actually, the light emitting diode driving power source for driving each of the light emitting diodes 41R, 41G, and 41B. 86 is arranged.

In the display device suitable for use in the second embodiment, a display area composed of pixels arranged in a matrix is divided into P × Q display area units. When expressed in terms of “row” and “column”, it can be said that the display area unit is divided into Q rows × P columns. The display area unit 12 is composed of a plurality of (M × N) pixels. When this state is expressed by “row” and “column”, it is composed of pixels of N rows × M columns. I can say. It should be noted that the display is arranged in a matrix and is located in the q-th row and the p-th column [where q = 1, 2,..., Q and p = 1, 2,. The area unit and the light source unit are represented as a display area unit 12 _{(q, p)} and a light source unit 42 _{(q, p)} , respectively, and the display area unit 12 _{(q, p)} or the light source unit 42 _{(q, p)} . The subscript “(q, p)” or “-(q, p)” may be added to related elements and items.

  In addition, the red light emitting subpixel (subpixel [R]), the green light emitting subpixel (subpixel [G]), and the blue light emitting subpixel (subpixel [B]) are collectively displayed as “subpixel [R]. , G, B] ”and may be referred to as subpixel [R, G, B] for controlling the operation (specifically, for example, controlling the light transmittance (aperture ratio)). The red light emission control signal, the green light emission control signal, and the blue light emission control signal input to R, G, B] may be collectively referred to as “control signals [R, G, B]”. A red light emitting subpixel input signal, a green light emitting subpixel input signal, and a blue light emitting subpixel input from the outside to drive the subpixels [R, G, B] constituting the display area or the display area unit. The pixel input signals may be collectively referred to as “input signals [R, G, B]”.

Each pixel has three subpixels (subpixels): a subpixel [R] (red light emitting subpixel), a subpixel [G] (green light emitting subpixel), and a subpixel [B] (blue light emitting subpixel). However, in the description of the following embodiments, the luminance control (gradation control) of each of the sub-pixels [R, G, B] is 8-bit control, and 2 from 0 to 255. ^{This is} done in ⁸ stages. Therefore, the value of the input signal [R, G, B] input to the liquid crystal display device driving circuit 90 to drive each of the sub-pixels [R, G, B] in each pixel constituting each display area unit 12. x _R, x _G, each x _B, takes a value of 2 ⁸ steps. Further, the values S _R , S _G , and S _B of the pulse width modulation output signal for controlling the respective light emission times of the red light emitting diode 41R, the green light emitting diode 41G, and the blue light emitting diode 41B constituting each light source unit are also 0. It takes 2 ⁸ stages of the value of 255. However, the present invention is not limited to this. For example, 10-bit control can be performed in 2 ¹⁰ stages from 0 to 1023. In this case, if an 8-bit numerical expression is multiplied by, for example, 4 times Good.

  A control signal for controlling the light transmittance Lt of each pixel is supplied from the driving unit to each pixel. Specifically, a control signal [R, G, B] for controlling the light transmittance Lt of each of the sub-pixels [R, G, B] is transmitted to each of the sub-pixels [R, G, B]. Supplied from the drive circuit 90. That is, in the liquid crystal display device driving circuit 90, a control signal [R, G, B] is generated from the input signal [R, G, B] that is input, and the control signal [R, G, B] is subpixel. [R, G, B] are supplied (output). Since the backlight or the light source luminance Y of the light source unit 42 is changed for each image display frame, the control signal [R, G, B] basically changes the value of the input signal [R, G, B]. A value obtained by performing correction (compensation) based on a change in the light source luminance Y with respect to the γ-corrected value. Then, a control signal [R, G, B] is sent from the timing controller 91 constituting the liquid crystal display device driving circuit 90 to the gate driver and source driver of the color liquid crystal display device 10 by a known method. Based on [R, G, B], the switching element 32 constituting each subpixel is driven, and a desired voltage is applied to the transparent first electrode 24 and the transparent second electrode 34 constituting the liquid crystal cell. The light transmittance (aperture ratio) Lt of the sub-pixel is controlled. Here, the larger the value of the control signal [R, G, B], the higher the light transmittance (subpixel aperture ratio) Lt of the subpixel [R, G, B], and the subpixel [R, G, B]. B] brightness (display brightness y) increases. That is, an image composed of light passing through the sub-pixels [R, G, B] (usually a kind of dot) is bright.

  The display luminance y and the light source luminance Y are controlled for each image display frame, each display area unit, and each light source unit in the image display of the color liquid crystal display device 10. Further, the operation of the color liquid crystal display device 10 and the operation of the backlight 40 in one image display frame are synchronized.

Example 1 relates to a display device and a driving method thereof according to the first aspect of the present invention. As described above, the display device of Example 1 is
(A) a display unit comprising a transmissive color liquid crystal display device 10 having a display area 11 composed of pixels arranged in a matrix;
(B) a backlight 40 that illuminates the back surface of the display unit (color liquid crystal display device 10), and
(C) Drive units 70, 80, 90 for controlling and driving the display unit (color liquid crystal display device 10) and the backlight 40 based on external input signals [R, G, B],
It has.

Then, the driving unit checks whether or not the average value x _ave of all the input signals [R, G, B] is equal to or greater than a predetermined value PD ₁ and determines the average value of all the input signals [R, G, B]. When x _ave is equal to or greater than the predetermined value PD ₁ , the power index in the γ correction of the input signal [R, G, B] is set to γ ₁₁ , and the luminance of the backlight 40 is controlled to the light source luminance Y _11. When the average value x _ave of the input signal [R, G, B] is less than the predetermined value PD ₁ , the power exponent in the γ correction of the input signal [R, G, B] is γ ₁₂ (where γ ₁₂ > γ ₁₁ ) and the luminance of the backlight 40 is controlled to the light source luminance Y ₁₂ (where Y ₁₂ > Y ₁₁ ). That is, in the first embodiment, the backlight 40 is not driven in a divided manner, but the light source luminance of the entire backlight 40 is controlled.

In the first embodiment or the second embodiment described later, the predetermined value PD ₁ may be determined by performing various display tests on the display device. The value of γ ₁₁ was set to 2.2.

  Hereinafter, a method for driving the display device according to the first embodiment will be described with reference to FIGS. 1, 4, and 5.

[Step-100]
An input signal [R, G, B] and a clock signal CLK for one image display frame sent from a known display circuit such as a scan converter are input to the backlight control circuit 70 and the liquid crystal display device driving circuit 90 ( (See FIG. 4). The input signals [R, G, B] are output signals from the image pickup tube, for example, when the input light amount to the image pickup tube is y _in, and are output from, for example, a broadcasting station and the light transmittance Lt of the pixel Is an input signal that is also input to the liquid crystal display device drive circuit 90 to control the above, and can be expressed as a function of the input light amount y _{in to} the power of 0.45. The values x _R , x _G , x _B of the input signals [R, G, B] for one image display frame input to the backlight control circuit 70 are stored in a storage device (memory) that constitutes the backlight control circuit 70. ) 72 is temporarily stored. Further, the values x _R , x _G , x _B of the input signals [R, G, B] for one image display frame inputted to the liquid crystal display device driving circuit 90 are also stored in the liquid crystal display device driving circuit 90. (Not shown) once stored.

[Step-110]
Next, the arithmetic circuit 71 constituting the backlight control circuit 70 reads the values of all the input signals [R, G, B] stored in the storage device 72 and averages the input signals [R, G, B]. _{Find the} value x _ave . Then, it is checked whether or not the average value x _ave is equal to or greater than a predetermined value PD ₁ . If the average value x _ave is less than the predetermined value PD ₁ , the average value flag is changed from the initial value “0” that has already been reset to “1”.

[Step-120]
When the average value x _ave of all input signals is equal to or greater than a predetermined value PD ₁ , that is,
x _ave ≧ PD ₁
Average value flag = 0
In order to set the power exponent in the γ correction of the input signal to γ ₁₁ (= 2.2), the value of the already reset γ value flag is kept at the initial value “0”, and Let the luminance of the light 40 be the light source luminance Y ₁₁ (= Y ₁ ).

On the other hand, when the average value x _ave of all input signals is less than the predetermined value PD ₁ , that is,
x _ave <PD ₁
Average value flag = 1
In order to set the power exponent in the γ correction of the input signal to γ ₁₂ (where γ ₁₂ > γ ₁₁ ), the value of the already reset γ value flag is changed from the initial value “0” to “1”. And the backlight brightness is set to the light source brightness Y ₁₂ (where Y ₁₂ > Y ₁₁ = Y ₁ ). Note that γ ₁₁ and γ ₁₂ are stored in advance in a storage device constituting the liquid crystal display device driving circuit 90.

In the processing in [Step-120] described above, more specifically, the value S _R of the pulse width modulation output signal for controlling the light emission time of the red light emitting diode 41R in the backlight 40. (Y ₁₁ ), S _R (Y ₁₂ ), pulse width modulation output signal values S _G (Y ₁₁ ), S _G (Y ₁₂ ) for controlling the light emission time of the green light emitting diode 41G, and the blue light emitting diode 41B The values S _B (Y ₁₁ ) and S _B (Y ₁₂ ) of the pulse width modulation output signal for controlling the light emission time are stored in the storage device 72, and according to the value of the average value flag, the arithmetic circuit 71 To read these values. Note that “S _R (Y ₁₁ )” means the value S _R of the pulse width modulation output signal required for setting the luminance of the backlight 40 to the light source luminance Y ₁₁ .

[Step-130]
Next, the value of the pulse width modulation output signal obtained in the arithmetic circuit 71 constituting the backlight control circuit 70 is sent to the storage device 82 of the light source unit drive circuit 80 and stored in the storage device 82. The clock signal CLK is also sent to the light source unit drive circuit 80 (see FIG. 5).

Then, the values [S _R (Y ₁₁ ), S _G (Y ₁₁ ), S _B (Y ₁₁ )] or [S _R (Y ₁₂ ), S _G (Y ₁₂ ), S _B ( Y ₁₂ )], on-time t _R-ON and off-time t _{R-OFF of} the red light-emitting diode 41R constituting the backlight 40, on-time t _G-ON and off-time t _{G-OFF of the} green light-emitting diode 41G The arithmetic circuit 81 determines the on time t _B-ON and the off time t _B-OFF of the blue light emitting diode 41B. still,
t _R-ON + t _R-OFF = t _G-ON + t _G-OFF = t _B-ON + t _B-OFF = constant value t _Const
It is. The duty ratio in driving based on pulse width modulation of the light emitting diode is
t _ON / (t _ON + t _OFF ) = t _ON / t _Const
It can be expressed as

Then, signals corresponding to the _ON times t _R-ON , t _G-ON and t _B-ON of the red light emitting diode 41R, the green light emitting diode 41G and the blue light emitting diode 41B constituting the backlight 40 are sent to the LED drive circuit 83. Based on the signal values corresponding to the _ON times t _R-ON , t _G-ON , t _B-ON from the LED drive circuit 83, the switching elements 85R, 85G, 85B are turned on by the ON time t _R-ON. , T _G-ON and t _B-ON are turned on, and the LED driving current from the light emitting diode driving power supply 86 is caused to flow to each of the light emitting diodes 41R, 41G and 41B. As a result, each of the light emitting diodes 41R, 41G, and 41B emits light for the on times t _R-ON , t _G-ON , and t _B-ON in one image display frame. Thus, the display area 11 is illuminated at a predetermined illuminance.

[Step-140]
On the other hand, the values x _R , x _G , x _B and γ value flags of the input signals [R, G, B] inputted to the liquid crystal display device driving circuit 90 are sent to the timing controller 91, The control signals [R, G, B] corresponding to the input signals [R, G, B] are supplied (output) to the sub-pixels [R, G, B]. The values X _R and X _{G of the} control signal [R, G, B] generated by the timing controller 91 of the liquid crystal display device driving circuit 90 and supplied from the liquid crystal display device driving circuit 90 to the sub-pixels [R, G, B]. , X _B and the values x _R , x _G , x _{B of} the input signals [R, G, B] when the γ value flag is “0”, the following equations (1-1) and ( 1-2) and Expression (1-3), and when the γ value flag is “1”, the following Expression (2-1), Expression (2-2), Expression (2-3) ). For example, the meaning of f (x _R (γ ₁₁ )) means that the base is x _R and the power index is γ ₁₁ , and more specifically, x _R is raised to the power of γ _11. To do.

X _R = f (x _R (γ ₁₁ )) (1-1)
X _G = f (x _G (γ ₁₁ )) (1-2)
X _B = f (x _B (γ ₁₁ )) (1-3)

X _R = f (x _R (γ ₁₂ )) (2-1)
X _G = f (x _G (γ ₁₂ )) (2-2)
X _B = f (x _B (γ ₁₂ )) (2-3)

  Thus, the image display operation in one image display frame is completed.

FIG. 3 shows the relationship between the normalized input signal value and the display luminance when γ ₁₁ is 2.2, γ ₁₂ = 2.4, and Y ₁₂ / Y ₁₁ = 2.0. Shown in Note that the horizontal axis of FIG. 3 is the value of the normalized input signal (x), and the vertical axis is the value of the normalized display luminance (y). In FIG. 3, a curve “a” indicates a case where the backlight 40 has normal brightness (that is, 1.0 as a normalized display luminance value) and γ ₁₁ = 2.2. The curve “b” shows the case where the brightness of the backlight 40 is doubled in the state of γ ₁₁ = 2.2 (2.0 as the normalized display luminance value). Comparing these curves “a” and “b”, when the value of the input signal (x) is large (that is, when the level of the normalized input signal is close to 1.0), a desired high display luminance is obtained. On the other hand, when the value of the input signal (x) is small (when the level of the normalized input signal is close to 0), the display luminance is similarly increased. It deviates from the curve “a” when the input signal (x) is small. A curve “c” shows a state where the brightness of the backlight 40 is doubled and γ ₁₂ = 2.4. It can be seen from the curve “c” that when the value of the normalized input signal (x) is small, the difference between the normalized display luminance (y) value and the value obtained from the curve “a” is small. That is, when the brightness of the entire display screen is relatively dark, the luminance of the backlight 40 is increased while the power index in the γ correction of the input signal is increased, so that the portion of the display screen that should be displayed brighter is displayed brighter. In addition, the increase in the brightness of the black display area can be suppressed, and the simple control of changing the γ correction parameter reliably prevents the occurrence of problems such as deterioration in image display quality. can do.

Example 2 relates to a display device and a driving method thereof according to the second aspect of the present invention. As described above, the display device of Example 2 is
(A) a display unit comprising a transmissive color liquid crystal display device 10 having a display area 11 composed of pixels arranged in a matrix;
(B) a backlight 40 configured to illuminate the back surface of the display unit (color liquid crystal display device 10), which includes light source units 42 arranged individually corresponding to the plurality of display region units 12 constituting the display region 11, and
(C) Drive units 70, 80, 90 for controlling and driving the display unit (color liquid crystal display device 10) and the backlight 40 based on external input signals;
It has. Then, the drive unit is based on the display area unit internal / maximum input signal having the maximum value x _U-max among the input signals [R, G, B] corresponding to each display area unit 12. The light emission state of the light source unit 42 corresponding to is controlled. That is, in the second embodiment, the backlight 40 is driven in a divided manner.

Here, the drive unit checks whether or not the average value x _ave of all input signals is equal to or greater than a predetermined value PD ₁ .

If the average value x _ave of all the input signals is equal to or greater than the predetermined value PD ₁ , the power exponent in the γ correction of the input signal corresponding to each display area unit 12 _{(q, p)} is γ ₂₁ , and this The luminance of the light source unit 42 _{(q, p)} corresponding to the display area unit 12 _{(q, p)} is determined based on the value x _{U-max (q, p)} of the maximum input signal in the display area unit Y _{2− Let (q, p)} .

On the other hand, when the average value x _ave of all input signals is less than the predetermined value PD ₁ , the following processing is performed.

That is, in the display area unit 12 _{(q, p)} in which the value x _{U-max (q, p) of the} maximum display signal in the display area unit is equal to or greater than the specified value PD ₂ , the display area unit 12 _{(q, p ) For} the γ correction of the input signal [R, G, B] corresponding to ₎ is γ ₂₂ (where γ ₂₂ > γ ₂₁ ), and the light source unit corresponding to the display area unit 12 _{(q, p)} The luminance of 42 _{(q, p)} is set to a light source luminance Y _{22- (q, p)} higher than the light source luminance Y _{2- (q, p)} based on the value x _U-max in the display area unit and the maximum input signal. To do. The value of the maximum input signal in the virtual display area unit at this time is assumed to be x _{U-max (q, p)} '.

On the other hand, in the display area unit 12 _{(q, p)} in which the value x _{U-max (q, p) of} the display area unit / maximum input signal is less than the specified value PD ₂ , the display area unit 12 _{(q, p ) For} the γ correction of the input signal corresponding to ₎ is γ ₂₁ , and the luminance of the light source unit 42 _{(q, p)} corresponding to this display area unit 12 _{(q, p)} [light source luminance Y _{22- (q , p)} ′] is the light source luminance Y _{2- (q, p)} based on the value x _{U-max (q, p)} in the display area unit and the maximum input signal.

In the second embodiment, the value of the specified value PD ₂ may be determined by performing various display tests on the display device. The value of γ ₂₁ is set to 2.2. In this case, the light source luminance Y ₂₁ of the light source unit 42 _{(q, p)} corresponding to the display region unit 12 _{(q, p)} is set to the light source luminance Y which is a luminance based on the value of the maximum input signal in the display region unit. ₂ Furthermore, the light source unit 42 _{(q, p)} and the light source luminance Y _22, the light source luminance Y ₂ in this case, the luminance based on the value x _U-max in the display area unit · maximum input signal _{(q, p)} And Y ₂₂ / Y ₂ > 1.

  Hereinafter, a method for driving the display device according to the second embodiment will be described with reference to FIGS. 2, 4, and 5.

[Step-200]
First, the same steps as [Step-100] and [Step-110] of the first embodiment are executed.

[Step-210]
Next, in the arithmetic circuit 71 constituting the backlight control circuit 70, the value of the input signal [R, G, B] stored in the storage device 72 is read and the (p, q) th [however, first, p = 1, q = 1] in the display area unit 12 _{(q, p)} , the sub-pixels [R, G in all the pixels constituting the (p, q) -th display area unit 12 _{(q, p)} , B] _{(q, p)} for driving the input signal [R, G, B] _{(q, p)} values x _{R- (q, p)} , x _{G- (q, p)} , x _{B- (q, p)} the value of the maximum value display area unit · maximum input signal of the x _U-max a _{(q, p),} determined in the arithmetic circuit 71. Then, the value x _{U-max (q, p)} of the display area unit maximum input signal is stored in the storage device 72. This step is executed for all of m = 1, 2,..., M, n = 1, 2,..., N, that is, for M × N pixels.

For example, x _{R- (q, p)} is a value corresponding to “110”, x _{G- (q, p)} is a value corresponding to “250”, and x _{B- (q, p)} is “ In the case of a value corresponding to “50”, x _{U−max (q, p)} is a value corresponding to “250”.

This operation is repeated from (p, q) = (1, 1) to (P, Q), and the value x _U-max in the display area unit in all display area units 12 _{(q, p) (q, p)} is stored in the storage device 72.

[Step-220]
When the average value x _ave of all input signals is equal to or greater than a predetermined value PD ₁ , that is,
x _ave ≧ PD ₁
Average value flag = 0
In order to set the power exponent in the γ correction of the input signal corresponding to each display area unit 12 _{(q, p)} to γ ₂₁ (= 2.2), the value of the already-reset γ value flag is set to It was left initial value of "0", and, the display area unit 12 _{(q, p)} the light source unit 42 _{(q, p)} corresponding to the light source luminance Y _{21- (q, p)} of the display area unit A light source luminance Y _{2- (q, p)} based on the maximum input signal value x _{U-max (q, p)} . Specifically, the control signal [R, G, B] _{(q, p)} corresponding to the maximum input signal (value x _{U-max (q, p)} ) within the display area unit is subpixel [R, G, B], and the light transmittance (aperture ratio) of the sub-pixel [R, G, B] at this time is assumed to be corrected to the light transmittance / first specified value Lt ₁ . Then, the light source luminance Y _{2- (q, p)} of the light source unit for obtaining the luminance of the sub-pixel [R, G, B] as the display luminance / second specified value (y _{2- (q, p) )} is obtained. Process. That is, the light source luminance of the light source unit is increased or decreased under the control of the light source unit drive circuit 80 _{(q, p)} .

On the other hand, when the average value x _ave of all input signals is less than the predetermined value PD ₁ , that is,
x _ave <PD ₁
Average value flag = 1
If so, the following processing is performed.

That is, in the display area unit 12 _{(q, p)} in which the value x _{U-max (q, p) of the} maximum display signal in the display area unit is equal to or greater than the specified value PD ₂ , the display area unit 12 _{(q, p ) In} the γ correction of the input signal [R, G, B] corresponding to ₎ is set to γ ₂₂ (where γ ₂₂ > γ ₂₁ ), the value of the already reset γ value flag is set to the initial value. The luminance of the light source unit 42 _{(q, p)} corresponding to the display area unit 12 _{(q, p)} is changed from “0” to “1”, and the value x _{U of the} maximum input signal in the display area unit is set. _The light source brightness Y _{22- (q, p)} is higher than the light source brightness Y _{2− (q, p)} based on _{−max (q, p)} .

Further, in the display area unit 12 _{(q, p)} in which the value x _U-max of the maximum input signal in the display area unit is less than the specified value PD ₂ , the input corresponding to this display area unit 12 _{(q, p)} In order to set the power index in the γ correction of the signal to γ ₂₁ , the value of the already reset γ value flag is kept at the initial value “0” and corresponds to the display area unit 12 _{(q, p)} . The light source luminance Y _{22- (q, p)} 'of the light source unit 42 _{(q, p)} is converted into the light source luminance Y _{2− (} based on the value x _{U-max (q, p)} of the maximum input signal in the display area unit. _{q, p)} .

In the processing in [Step-220] described above, more specifically, the following expressions (3-1), (3-2), and (3-3) are satisfied. Thus, the light source luminances Y ₂₁ , Y ₂₂ , Y ₂₂ ′ may be controlled for each image display frame and for each light source unit. That is, the luminance of the light source 41 is controlled based on the equations (4-1), (4-2), and (4-3) that are the light source luminance control function g (x _nol-max ), and the equation (3) -1), formulas (3-2), and formulas (3-3), the light source luminances Y ₂₁ , Y ₂₂ , and Y ₂₂ ′ may be controlled. A conceptual diagram of such control is shown in FIGS. 8A and 8B. However, as will be described later, it is necessary to perform correction based on the influence of the other light source unit 42 on the light source luminances Y ₂₁ , Y ₂₂ , Y ₂₂ ′. It should be noted that these relations relating to the control of the light source luminances Y ₂₁ , Y ₂₂ , Y ₂₂ ′, that is, the value x _{U-max of} the display area unit / maximum input signal, and an input having a value equal to the maximum value x _U-max The value of the control signal corresponding to the signal, the display luminance when assuming that such a control signal is supplied to the pixel (sub-pixel), the second specified value y ₂ , and the light transmittance (aperture) of each sub-pixel at this time Rate) [light transmittance / second prescribed value Lt ₂ ], and the display transmittance / second prescribed value Y ₂₁ when the light transmittance (aperture ratio) of each sub-pixel is the light transmittance / first prescribed value Lt _1. , Y ₂₂ , Y ₂₂ ′, the relationship between the luminance control parameters in the light source unit may be obtained in advance and stored in the storage device 72 or the like.

Y ₂₁ · Lt ₁ = Y ₁ · Lt ₂ (3-1)
g (x _nol-max ) = a ₁ · (x _nol-max ) ^2.2 + a ₀ (4-1)
Y ₂₂ · Lt ₁ = Y ₁ · Lt ₂ (4-1)
g (x _nol-max ') = a ₁ · (x _nol-max ') ^2.2 + a ₀ (4-2)
Y ₂₂ '· Lt ₁ = Y ₁ · Lt ₂ (3-3)
g (x _nol-max ) = a ₁ · (x _nol-max ) ^2.2 + a ₀ (4-3)

Here, input signals (input signals [R, G, B]) that are input to the liquid crystal display driving circuit 90 to drive the pixels (or the sub-pixels [R, G, B] constituting the pixels). ) _Is the maximum value x _In-max ,
x _nol-max ≡ x _U-max / x _In-max
And a ₁ and a ₀ are constants,
a ₁ + a ₀ = 1
0 <a ₀ <1, 0 <a ₁ <1
It can be expressed as For example,
a ₁ = 0.99
a ₀ = 0.01
And it is sufficient. The value x _R, x _G of the input signal [R, G, B], each x _B, and takes a value of 2 ⁸ steps, the value of x _{an In-max} is a value corresponding to "255" .

By the way, in the backlight, for example, assuming brightness control of the light source unit 42 _(1, 1) of (p, q) = (1, 1), the other P × Q light source units 42 It is necessary to consider the effects of Since the influence of such a light source unit 42 from other light source units 42 is known in advance by the light emission profile of each light source unit 42, the difference can be calculated by back calculation, and as a result, correction is possible. The basic form of calculation will be described below.

P × Q based on the request of Formula (3-1), Formula (3-2), Formula (3-3), Formula (4-1), Formula (4-2), and Formula (4-3) The luminance (light source luminance Y ₂₁ , Y ₂₂ ) required for the light source unit 42 is represented by a matrix [L _PxQ ]. Further, the luminance of a certain light source unit obtained when only a certain light source unit is driven and the other light source units are not driven is obtained in advance for the P × Q light source units 42. Such luminance is represented by a matrix [L ′ _PxQ ]. Further, the correction coefficient is represented by a matrix [α _PxQ ]. Then, the relationship between these matrices can be expressed by the following equation (5-1). The correction coefficient matrix [α _PxQ ] can be obtained in advance.
[L _PxQ ] = [L ′ _PxQ ] · [α _PxQ ] (5-1)
Therefore, what is necessary is just to obtain | _require matrix [L' _PxQ ] from Formula (5-1). The matrix [L ′ _PxQ ] can be obtained from the inverse matrix operation. That is,
[L ′ _PxQ ] = [L _PxQ ] · [α _PxQ ] ⁻¹ (5-2)
Should be calculated. Then, the light source 41 _{(q, p)} may be controlled so that the luminance represented by the matrix [L ′ _PxQ ] is obtained. Specifically, the operation and processing are stored in the storage device (memory) 82. What is necessary is just to perform using the information (data table). In the control of the light source 41 _{(q, p)} , since the value of the matrix [L ′ _PxQ ] cannot take a negative value, it is needless to say that the calculation result needs to be kept in a positive region. . Therefore, the solution of equation (5-2) may not be an exact solution but an approximate solution.

As described above, the expressions (3-1), (3-2), (3-3), (4-1), and (4) obtained in the arithmetic circuit 71 included in the backlight control circuit 70 are obtained. -2) Based on the matrix [L _PxQ ] and the correction coefficient matrix [α _PxQ ] obtained based on the values of Equation (4-3), as described above, it is assumed that the light source unit is driven alone. A luminance matrix [L ′ _PxQ ] is obtained, and further converted into a corresponding integer in the range of 0 to 255 based on the conversion table stored in the storage device 72. Thus, in the arithmetic circuit 71 constituting the backlight control circuit 70, the value S _R of the pulse width modulation output signal for controlling the light emission time of the red light emitting diode 41R _{(q, p) in} the light source unit 42 _{(q, p)} . _{- (q, p),} a green light emitting diode 41G _{(q, p)} of the pulse width modulation output signal for controlling the light emission time of the value S _{G- (q, p),} the blue LED 41B _{(q, p)} of The value S _{B− (q, p)} of the pulse width modulation output signal for controlling the light emission time can be obtained.

[Step-230]
Next, the values S _{R- (q, p)} , S _{G- (q, p)} , S _{B- (q, p ) of} the pulse width modulation output signal obtained in the arithmetic circuit 71 constituting the backlight control circuit 70. ₎ Is sent to the storage device 82 of the light source unit drive circuit 80 _{(q, p)} provided corresponding to the light source unit 42 _{(q, p)} and stored in the storage device 82. The clock signal CLK is also sent to the light source unit drive circuit 80 _{(q, p)} (see FIG. 5).

Then, based on the values S _{R− (q, p)} , S _{G− (q, p)} , S _{B− (q, p)} of the pulse width modulation output signal, the red color constituting the light source unit 42 _{(q, p)} ON time t _R-ON and OFF time t _{R-OFF of} the light emitting diode 41R _{(q, p)} , ON time t _G-ON and OFF time t _{G-OFF of} the green light emitting diode 41G _{(q, p)} , blue light emitting diode The arithmetic circuit 81 determines an on time t _B-ON and an off time t _B-OFF of 41B _{(q, p)} . still,
t _R-ON + t _R-OFF = t _G-ON + t _G-OFF = t _B-ON + t _B-OFF = constant value t _Const
It is. The duty ratio in driving based on pulse width modulation of the light emitting diode is
t _ON / (t _ON + t _OFF ) = t _ON / t _Const
It can be expressed as

The on-time t _{R-ON- of} the red light emitting diode 41R _{(q, p)} , the green light emitting diode 41G _{(q, p)} , and the blue light emitting diode 41B _{(q, p)} constituting the light source unit 42 _{(q, p).} Signals corresponding to _{(q, p)} , t _{G-ON- (q, p)} , t _{B-ON- (q, p)} are sent to the LED drive circuit 83, and the on-time from the LED drive circuit 83 Based on the value of the signal corresponding to t _{R-ON- (q, p)} , t _{G-ON- (q, p)} , t _{B-ON- (q, p)} , switching element 85R _{(q, p)} , 85G _{(q, p)} and 85B _{(q, p)} are only ON times t _{R-ON- (q, p)} , t _{G-ON- (q, p)} , t _{B-ON- (q, p)} The LED driving current from the light emitting diode driving power source 86 is turned on, and the LED driving current is supplied to each of the light emitting diodes 41R _{(q, p)} , 41G _{(q, p)} , 41B _{(q, p)} . As a result, each of the light emitting diodes 41R _{(q, p)} , 41G _{(q, p)} , 41B _{(q, p)} has an on time t _{R-ON- (q, p)} , t _{G- in} one image display frame. Only _{ON- (q, p)} and t _{B-ON- (q, p)} emit light. Thus, the (p, q) -th display area unit 12 _{(q, p)} is illuminated at a predetermined illuminance.

[Step-240]
On the other hand, the values x _{R- (q, p)} , x _{G- (q, p)} , x _{B- (of} the input signal [R, G, B] _{(q, p)} inputted to the liquid crystal display device driving circuit 90. _{q, p)} and a γ value flag are sent to the timing controller 91, and the timing controller 91 receives a control signal [R, G, corresponding to the input signal [R, G, B] _{(q, p).} , B] _{(q, p)} is supplied (output) to the sub-pixel [R, G, B] _{(q, p)} . Control signals [R, G, B] _(q generated by the timing controller 91 of the liquid crystal display device driving circuit 90 and supplied from the liquid crystal display device driving circuit 90 to the sub-pixels [R, G, B] _{(q, p) , p)} values X _{R- (q, p)} , X _{G- (q, p)} , X _{B- (q, p)} and the value x of the input signal [R, G, B] _{(q, p) R- (q, p)} , x _{G- (q, p)} , x _{B- (q, p)} are the following formulas (6-1) and (6) when the γ value flag is “0”: When the γ value flag is “1”, the relations of (7-1), (7-2), and (7-3) are satisfied. There is a relationship. For example, the meaning of f ′ (x _R (γ ₂₁ )) means that the base is x _R and the power index is γ ₂₁ , and more specifically, x _R is raised to the power of γ _21. means.
X _R = f ′ (x _R (γ ₂₁ )) (6-1)
X _G = f ′ (x _G (γ ₂₁ )) (6-2)
X _B = f ′ (x _B (γ ₂₁ )) (6-3)

X _R = f ′ (x _R (γ ₂₂ )) (7-1)
X _G = f ′ (x _G (γ ₂₂ )) (7-2)
X _B = f ′ (x _B (γ ₂₂ )) (7-3)

Further, since the light source luminances Y _{2- (q, p)} , Y _{22- (q, p)} , Y _{22- (q, p)} ′ of the light source unit 42 _{(q, p)} are changed for each image display frame, The control signal [R, G, B] _{(q, p)} basically has a light source luminance Y _{2− with} respect to a value obtained by γ-correcting the value of the input signal [R, G, B] _{(q, p). (q, p)} , Y _{22- (q, p)} , Y _{22- (q, p)} 'has a value _subjected to correction (compensation) based on changes. That is, in the second embodiment, the light source luminances Y _{2- (q, p)} , Y _{22- (q, p)} , Y _{22- (q, p)} ′ change every image display frame. Appropriate display brightness and second specified value y _{2- (q, p)} are obtained at light source brightness Y _{2- (q, p)} , Y _{22- (q, p)} , Y _{22- (q, p)} ' determining control signals [R, G, B] ( q, p) the value X _R- of _{(q, p), X G-} (q, p), X B- and _{(q, p)} as the correction (compensation And the light transmittance (aperture ratio) Lt of the sub-pixel is controlled. Here, the function f ′ of Expression (6-1), Expression (6-2), Expression (6-3), Expression (7-1), Expression (7-2), and Expression (7-3) is It is a function determined in advance for performing such correction (compensation).

  Thus, the image display operation in one image display frame is completed.

  As mentioned above, although this invention was demonstrated based on the preferable Example, this invention is not limited to these Examples. The configurations and structures of the transmissive color liquid crystal display device, backlight, light source unit, display device, and driving unit described in the embodiments are examples, and members, materials, and the like constituting these are also examples, and may be changed as appropriate. can do. Luminance compensation (correction) and temperature control of the light source unit 42 may be performed by monitoring the temperature of the light emitting diode with a temperature sensor and feeding back the result to the light source unit drive circuit 80. In the embodiments, the description has been made on the assumption that the display area of the liquid crystal display device is divided into P × Q virtual display area units. However, in some cases, the transmissive liquid crystal display device has P × Q. You may have the structure divided | segmented into the actual display area unit.

In the first embodiment, when the average value x _{ave of} all the input signals [R, G, B] is less than the predetermined value PD ₁ , the power exponent in the γ correction of the input signals [R, G, B] is γ ₁₂ ( However, γ ₁₂ > γ ₁₁ ) and the luminance of the backlight 40 is controlled to the light source luminance Y ₁₂ (Y ₁₂ > Y ₁₁ ). At this time, any of the following requirements is further weighted: May be.
(11) red light emitting maximum input signal subpixel input signal x _R, green light-emitting maximum input signal subpixel input signal x _G, the maximum input signal of the maximum input signal of the blue-emitting subpixel input signal x _B x _{max- When (RGB)} exceeds a certain value.
(12) The average value [(x _R + x _G + x _B ) / 3] of the red light emission sub-pixel input signal, the green light emission sub-pixel input signal and the blue light emission sub-pixel input signal in the three sub-pixels constituting one pixel The maximum value x _max-ave in the above exceeds a certain value.
(13) is a red light emitting subpixel input signal x _R in the three sub-pixels constituting one pixel specified value PD ₂ or more, and is a green light-emitting sub-pixel input signal x _G is the specified value PD ₂ or more, and, when the blue light-emitting sub-pixel input signal x _B is the prescribed value PD ₂ or more.
(14) In the case of (11) above, sub-pixels having a maximum input signal of 0.9 times or more of the maximum input signal x _{max- (RGB)} , for example, are present in a predetermined ratio or more with respect to all sub-pixels .
(15) In the case of (12) above, a set of sub-pixels (pixels) having an average value of, for example, 0.9 times or more of the maximum value x _max-ave exists in a predetermined ratio or more with respect to all pixels. If.
(16) In the case of (13) above, the number of pixels satisfying the requirement of (13) above is greater than or equal to a predetermined ratio with respect to all the pixels constituting one display area unit.

In the second embodiment, whether or not the value x _{U-max (q, p) in} the display area unit is equal to or greater than the specified value PD ₂ is checked. maximum If the input signal has one of the following values, it can be judged that the value _{x U-max (q, p} ) of the display area unit · maximum input signal is the specified value PD ₂ or more.
(21) red light emitting maximum input signal subpixel input signal x _R, green light-emitting maximum input signal subpixel input signal x _G, the value x of the maximum input signal of the maximum input signal of the blue-emitting subpixel input signal x _{B U-max (q, p)} - (RGB) is the specified value PD ₂ or more.
(22) The average value [(x _R + x _G + x _B ) / 3] of the red light emission sub-pixel input signal, the green light emission sub-pixel input signal, and the blue light emission sub-pixel input signal in the three sub-pixels constituting one pixel the maximum value _{x U-max (q, p} ) of the inner _-ave is defined value PD ₂ or more.
(23) The red light emission subpixel input signal x _R in three subpixels constituting one pixel is not less than a specified value PD ₂ , and the green light emission subpixel input signal x _G is not less than the specified value PD ₂ , and is a blue light-emitting sub-pixel input signal x _B is the prescribed value PD ₂ or more.
(24) In the case of (21) above, a sub-pixel having a maximum input signal of, for example, 0.9 times or more of the maximum input signal value x _{U−max (q, p) − (RGB)} is one display region. When there is a predetermined ratio or more with respect to all the sub-pixels constituting the unit.
(25) In the case of (22) above, a set of subpixels (pixels) having an average value of, for example, 0.9 times or more of the maximum value _{xU-max (q, p) -ave} is one display area unit. When there is a predetermined ratio or more with respect to all the pixels constituting the.
(26) In the case of (23) above, the number of pixels satisfying the requirement of (23) is greater than or equal to a predetermined ratio with respect to all the pixels constituting one display area unit.

FIG. 1 is a flowchart for explaining a method of driving the display device according to the first embodiment. FIG. 2 is a flowchart for explaining a method of driving the display device according to the second embodiment. FIG. 3 shows the normalized input signal value and display luminance when γ ₁₁ is 2.2, γ ₁₂ = 2.4, and Y ₁₂ / Y ₁₁ = 2.0. It is a graph which shows a relationship. FIG. 4 is a conceptual diagram of a color liquid crystal display device suitable for use in the embodiment and a display device including a backlight. FIG. 5 is a conceptual diagram of a portion of a drive circuit suitable for use in the embodiment. 6A is a diagram schematically showing the arrangement and arrangement of light emitting diodes and the like in the backlight of the example. FIG. 6B is a diagram illustrating the color liquid crystal display device and the backlight of the example. It is a typical partial sectional view of a display device which consists of. FIG. 7 is a schematic partial cross-sectional view of a color liquid crystal display device. 8A and 8B show display luminance when it is assumed that a control signal corresponding to an input signal having a value equal to the value x _U-max in the display area unit and the maximum input signal is supplied to the pixel. FIG. 6 is a conceptual diagram for explaining a state in which the light source luminance Y ₂ of the light source unit is increased or decreased under the control of the drive unit so that the second specified value y ₂ is obtained by the light source unit. FIGS. 9A and 9B are conceptual diagrams for explaining the relationship among the light source luminance of the backlight, the light transmittance (aperture ratio) of the pixel, and the display luminance in the display area unit. FIGS. 10A, 10B, and 10C respectively show the state of light transmittance (aperture ratio) in the pixels constituting the display area unit and the light source luminance for explaining problems in the conventional technique. It is the figure which showed typically the state of and the state of display luminance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Color liquid crystal display device, 11 ... Display area, 12 ... Display area unit, 13 ... Liquid crystal material, 20 ... Front panel, 21 ... 1st board | substrate, 22. .... Color filter, 23 ... Overcoat layer, 24 ... Transparent first electrode, 25 ... Alignment film, 26 ... Polarizing film, 30 ... Rear panel, 31 ... Second 32 ... switching element, 34 ... transparent second electrode, 35 ... alignment film, 36 ... polarizing film, 37 ... insulating layer, 40 ... backlight, 41, 41R , 41G, 41B ... light emitting diode (light source), 42 ... light source unit, 43, 43R, 43G, 43B ... photodiode (light sensor), 44 ... partition wall, 51 ... housing, 52A ... Bottom of the housing, 52B ... Side surface of the casing, 53 ... outer frame, 54 ... inner frame, 55A, 55B ... spacer, 56 ... guide member, 57 ... bracket member, 61 ... diffusing plate, 62. ..Diffusion sheet, 63... Prism sheet, 64... Polarization conversion sheet, 65 .. reflection sheet, 70... Backlight control circuit, 71. Memory), 80... Light source unit drive circuit, 81... Arithmetic circuit, 82... Storage device (memory), 83... LED drive circuit, 84 ... photodiode control circuit, 85R, 85G, 85B ... Switching element, 86 ... Light emitting diode drive power supply, 90 ... Liquid crystal display drive circuit, 91 ... Timing controller

Claims (4)

(A) a display unit composed of a transmissive liquid crystal display device having a display area composed of pixels arranged in a matrix;
(B) a backlight for illuminating the back surface of the display unit, and
(C) a drive unit that controls and drives the display unit and the backlight based on an external input signal;
A display device comprising:
The drive unit
Check whether the average value of all input signals is greater than or equal to a predetermined value,
If the average value of all the input signals is a predetermined value or more, the exponent and gamma ₁₁ in gamma correction of the input signal, and to control the luminance of the backlight to Y _11,
When the average value of all input signals is less than a predetermined value, the power index in the γ correction of the input signal is γ ₁₂ (where γ ₁₂ > γ ₁₁ ), and the backlight brightness is Y ₁₂ (where Y ₁₂ > Y ₁₁ ). (A) a display unit composed of a transmissive liquid crystal display device having a display area composed of pixels arranged in a matrix;
(B) a light source unit individually arranged corresponding to a plurality of display area units constituting the display area, a backlight for illuminating the back surface of the display unit, and
(C) a drive unit that controls and drives the display unit and the backlight based on an external input signal;
With
The drive unit is a display device that controls the light emission state of the light source unit corresponding to the display area unit based on the in-display area unit maximum input signal having the maximum value among the input signals corresponding to each display area unit. And
The drive unit
(A) Check whether the average value of all input signals is equal to or greater than a predetermined value,
(B-1) When the average value of all input signals is greater than or equal to a predetermined value, the power index in the γ correction of the input signals corresponding to each display area unit is γ ₂₁ and the light source corresponding to the display area unit Control the brightness of the unit based on the value of the maximum input signal in the display area unit,
(B-2) When the average value of all input signals is less than a predetermined value,
In the display area unit in the display area unit and the value of the maximum input signal is equal to or greater than the specified value, the power index in the γ correction of the input signal corresponding to the display area unit is γ ₂₂ (where γ ₂₂ > γ ₂₁ ). And the brightness of the light source unit corresponding to the display area unit is controlled to be higher than the brightness based on the value of the maximum input signal in the display area unit,
In the display area unit, the value of the maximum input signal in the display area unit is less than the specified value. The input index corresponding to the display area unit is γ ₂₁ in the γ correction and corresponds to the display area unit. And controlling the brightness of the light source unit to a brightness based on the value of the maximum input signal in the display area unit. (A) a display unit composed of a transmissive liquid crystal display device having a display area composed of pixels arranged in a matrix;
(B) a backlight for illuminating the back surface of the display unit, and
(C) a drive unit that controls and drives the display unit and the backlight based on an external input signal;
A driving method of a display device comprising:
Check whether the average value of all input signals is equal to or greater than a predetermined value or not in the drive unit,
When the average value of all the input signals is equal to or greater than a predetermined value, the driving unit controls the power index in the γ correction of the input signal to γ ₁₁ and the backlight brightness to Y ₁₁ ,
When the average value of all the input signals is less than a predetermined value, the driving unit sets the power exponent in the γ correction of the input signal to γ ₁₂ (where γ ₁₂ > γ ₁₁ ), and the luminance of the backlight is Y _12. (However, Y ₁₂ > Y ₁₁ ) (A) a display unit composed of a transmissive liquid crystal display device having a display area composed of pixels arranged in a matrix;
(B) a light source unit individually arranged corresponding to a plurality of display area units constituting the display area, a backlight for illuminating the back surface of the display unit, and
(C) a drive unit that controls and drives the display unit and the backlight based on an external input signal;
With
The drive unit drives the display device that controls the light emission state of the light source unit corresponding to the display area unit based on the in-display area unit / maximum input signal having the maximum value among the input signals corresponding to each display area unit. A method,
(A) The drive unit checks whether the average value of all input signals is equal to or greater than a predetermined value,
If the average value of (B-1) the total input signal is a predetermined value or more, in the drive unit, and gamma ₂₁ the exponent in the gamma correction of the input signal corresponding to each display area unit, and, the display area units Control the brightness of the light source unit corresponding to the brightness based on the value of the maximum input signal in the display area unit,
(B-2) When the average value of all input signals is less than a predetermined value,
In the display area unit, in the display area unit in which the value of the maximum input signal is equal to or greater than the specified value, the driving unit sets the power exponent in the γ correction of the input signal corresponding to the display area unit to γ ₂₂ (where γ ₂₂ > γ ₂₁ ), and the luminance of the light source unit corresponding to the display area unit is controlled to be higher than the luminance based on the value of the maximum input signal in the display area unit,
In the display area unit, in the display area unit in which the value of the maximum input signal is less than the specified value, the driving unit sets the power index in the γ correction of the input signal corresponding to the display area unit to γ ₂₁ , and A drive method for a display device, wherein the brightness of a light source unit corresponding to the display area unit is controlled to a brightness based on a value in the display area unit and the maximum input signal.

Images