JP2007322882A - Display device and display control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enlarge the dynamic range of display luminance while suppressing unevenness in a black image. <P>SOLUTION: The display device includes: a light source control circuit 33 that converts luminance setting values BLset<SB>11</SB>to BLset<SB>56</SB>for light sources BL<SB>11</SB>to BL<SB>56</SB>of a backlight 12 supplied from a liquid crystal panel control circuit 31 into backlight control values BLctl<SB>11</SB>to BLctl<SB>56</SB>by using a backlight control value conversion table and supplies the values to the backlight 12; and the liquid crystal panel control circuit 31 that calculates setting gradation S_data' which determines an opening ratio of each pixel in a display unit 21 from the luminance setting values BLset<SB>11</SB>to Beset<SB>56</SB>of the light sources BL<SB>11</SB>to BL<SB>56</SB>based on a setting gradation conversion table for enlarging a dynamic range, corresponding to first display luminance characteristics, and supplies the gradation as drive control signals to the liquid crystal panel 11. For example, the display device is applicable to a liquid crystal display device. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a display device and a display control method, and more particularly to a display device and a display control method capable of expanding a dynamic range of display luminance while suppressing black unevenness.

  A liquid crystal display (LCD) is a liquid crystal panel having a color filter substrate colored with R (Red), G (Green), or B (Blue), a liquid crystal layer, and the like on the back side. It is composed of a backlight that is arranged.

  In a liquid crystal display device, the twist of the liquid crystal molecules in the liquid crystal layer is controlled by changing the voltage, and the backlight light that has passed through the liquid crystal layer according to the twist of the liquid crystal molecules is colored R, G, or B. By passing through the color filter substrate, light of R, G, or B color is obtained and an image is displayed.

  In the following, changing the light transmittance by controlling the twist of the liquid crystal molecules by changing the voltage is referred to as controlling the aperture ratio. The luminance of light emitted from the backlight, which is the light source, is referred to as “emission luminance”, and the luminance of light emitted from the front of the liquid crystal panel, which is the intensity of light felt by the viewer viewing the displayed image. Is referred to as “display luminance”.

  Conventionally, in a liquid crystal display device, the backlight illuminates the entire screen of the liquid crystal panel with a uniform and maximum (almost maximum) brightness, and controls only the aperture ratio of each pixel of the liquid crystal panel, whereby each pixel of the screen is controlled. In such a case, control is performed so as to obtain a necessary display luminance. Therefore, for example, even when the entire screen is dark, the backlight emits light with the maximum light emission luminance, which causes a problem of high power consumption.

  In order to solve this problem, for example, a method has been proposed in which the screen is divided into a plurality of areas and the light emission luminance of the backlight is controlled in units of the divided areas (for example, see Patent Documents 1 and 2).

  Such backlight control will be described with reference to FIG.

  FIG. 1A shows an original image P1 displayed on the liquid crystal display device. The original image P1 has the darkest region R1 having an elliptical shape at a substantially central portion, and the image gradually becomes brighter from the region R1 toward the outer peripheral side.

  FIG. 1B is a simplified diagram showing the structure of the backlight.

  In the backlight shown in FIG. 1B, the light emitting area is divided into 24 parts by dividing into 4 parts in the horizontal direction (horizontal direction) and 6 parts in the vertical direction (vertical direction).

  When the backlight of FIG. 1B emits light corresponding to the original image P1, the backlight is turned on (reduces) while suppressing the luminance of the two shaded areas in FIG. 1B.

  As a result, with respect to the entire backlight, a luminance distribution of light emission luminance as shown in FIG. 1C can be obtained with respect to the original image P1 in FIG. 1A, and a part of the backlight corresponding to the darkest region R1 can be obtained. Since it is dimmed, power consumption is reduced.

JP 2004-221503 A JP 2004-246117 A

  By the way, in the backlight control as described above, as shown in FIG. 2, the luminance of the central region R1 ′ is high (bright), and the luminance of the peripheral region R2 ′ is low (dark). When the original image P1 ′ is displayed, the luminance of the pixels around the region R1 ′ in the region R2 ′ is pulled by the luminance of the region R1 ′ and displayed brighter than the original color (black). Sometimes. This phenomenon is called black unevenness.

  The present invention has been made in view of such a situation, and makes it possible to expand the dynamic range of display luminance while suppressing black unevenness.

  A display device according to a first aspect of the present invention is a display device that displays an image corresponding to an image signal in a predetermined display area, and a plurality of individually arranged corresponding to a plurality of areas obtained by dividing the display area. A backlight having a plurality of light sources, a panel having a plurality of pixels corresponding to the display area, and changing the transmittance of light from the light sources in units of pixels, and the emission luminance of the plurality of light sources in the image signal And a control unit that sets the light transmittance of the pixel corresponding to the light emission luminances of the plurality of light sources set individually, and the control unit transmits the light. The light transmittance of the pixel corresponding to the light emission brightness of the plurality of light sources is set based on the display brightness characteristic representing the relationship between the image rate and the display brightness of the image. Display brightness of the image below the transmittance But with a non-zero value, and has a value lower than the reference display brightness characteristics when setting the emission luminance of the plurality of light sources to the same.

  Storage means for storing a plurality of data corresponding to the display luminance characteristics having different display luminances of the image below the predetermined light transmittance is further provided, and the control means further includes a luminance distribution of the image. Accordingly, one display luminance characteristic is selected from among the plurality of display luminance characteristics, and the light transmittance of the pixel corresponding to the light emission luminance of the plurality of light sources is selected based on the selected display luminance characteristic. Can be set.

  The display control method according to the first aspect of the present invention includes a backlight having a plurality of light sources individually arranged for a plurality of areas obtained by dividing a predetermined display area, and a plurality of pixels corresponding to the display area. A panel that changes the transmittance of light from the light source in units of pixels, and the light emission luminance of the plurality of light sources are individually set according to an image signal, and light emission of the plurality of light sources that are individually set Control means for setting light transmittance of the pixels corresponding to luminance, and in the display control method of a display device for displaying an image corresponding to the image signal in the display region, light emission of the plurality of light sources Brightness is set individually according to the image signal, and the light emission brightness of the plurality of light sources is set individually based on the display brightness characteristic that represents the relationship between the light transmittance and the display brightness of the image Of the pixel light The display luminance characteristic is set such that the display luminance of the image having a predetermined light transmittance or less is a value other than 0 and the light emission luminances of the plurality of light sources are set to be the same. The value is lower than the reference display luminance characteristic at that time.

  In the first aspect of the present invention, the light emission luminances of the plurality of light sources are individually set according to the image signal, and based on display luminance characteristics representing the relationship between the light transmittance and the image display luminance. The light transmittance of the pixels of the panel is set in accordance with the light emission luminances of the plurality of individually set light sources.

  The display device according to the second aspect of the present invention is a display device that displays an image corresponding to an image signal in a predetermined display area, and a plurality of individually arranged corresponding to the plurality of areas obtained by dividing the display area. A backlight having a plurality of light sources, a panel having a plurality of pixels corresponding to the display area, and changing the transmittance of light from the light sources in units of pixels, and conversion means for converting the image signal according to a predetermined function And individually setting the light emission luminance of the plurality of light sources according to the image signal converted by the conversion means, and corresponding to the light emission luminance of the plurality of light sources set individually, Control means for setting the light transmittance, and the control means corresponds to the light emission luminance of the plurality of light sources based on a display luminance characteristic representing a relationship between the light transmittance and the display luminance of the image. The picture to be The display luminance characteristic is set such that the display luminance of the image below a predetermined light transmittance is a value other than 0, and the light emission luminances of the plurality of light sources are set to be the same. The value is lower than the reference display luminance characteristic at that time.

  Storage means for storing a plurality of data corresponding to the display luminance characteristics having different display luminances of the image below the predetermined light transmittance is further provided, and the control means further includes a luminance distribution of the image. Accordingly, one display luminance characteristic can be selected from the plurality of display luminance characteristics, and the light transmittance of the pixel can be set based on the selected display luminance characteristic.

  The display control method according to the second aspect of the present invention includes a backlight having a plurality of light sources individually arranged for a plurality of areas obtained by dividing a predetermined display area, and a plurality of pixels corresponding to the display area. A panel that changes the transmittance of light from the light source in pixel units, conversion means that converts an image signal according to a predetermined function, and the image obtained by converting the light emission luminances of the plurality of light sources by the conversion means Control means for setting the light transmittance of the pixels in correspondence with the light emission luminances of the plurality of light sources set individually according to the signals, and corresponding to the image signal In the display control method of the display device for displaying the image in the display area, the image signal is converted according to a predetermined function, the light emission luminance of the plurality of light sources is individually set according to the converted image signal, Setting the light transmittance of the pixel corresponding to the light emission brightness of the plurality of light sources set individually based on display brightness characteristics representing the relationship between the transmittance of the image and the display brightness of the image, The display luminance characteristic is lower than a reference display luminance characteristic when the display luminance of the image below a predetermined light transmittance is a value other than 0 and the emission luminances of the plurality of light sources are set to be the same. It is a value.

  In the second aspect of the present invention, the image signal is converted according to a predetermined function, and the light emission luminances of the plurality of light sources are individually set according to the image signal, and the light transmittance and the image display luminance are Based on the display luminance characteristics representing the relationship, the light transmittance of the pixels of the panel is set corresponding to the light emission luminances of a plurality of individually set light sources.

  According to one aspect of the present invention, an image can be displayed. In addition, according to one aspect of the present invention, the dynamic range of display luminance can be expanded while suppressing black unevenness.

  Embodiments of the present invention will be described below. Correspondences between the constituent elements of the present invention and the embodiments described in the specification or the drawings are exemplified as follows. This description is intended to confirm that the embodiments supporting the present invention are described in the specification or the drawings. Therefore, even if there is an embodiment which is described in the specification or the drawings but is not described here as an embodiment corresponding to the constituent elements of the present invention, that is not the case. It does not mean that the form does not correspond to the constituent requirements. Conversely, even if an embodiment is described here as corresponding to a configuration requirement, that means that the embodiment does not correspond to a configuration requirement other than the configuration requirement. It's not something to do.

  The display device according to the first aspect of the present invention is a display device that displays an image corresponding to an image signal in a predetermined display area (for example, the liquid crystal display device 101 in FIG. 6), and a plurality of the display areas are divided. A backlight having a plurality of light sources individually arranged corresponding to the region (for example, the backlight 12 in FIG. 6) and a plurality of pixels corresponding to the display region, and light from the light source in units of pixels A panel (for example, the liquid crystal panel 11 in FIG. 6) that changes the transmittance of light and the light emission luminance of the plurality of light sources are individually set according to the image signal, and light emission of the plurality of light sources that are individually set Control means (for example, the liquid crystal panel control circuit 31 in FIG. 6) that sets the light transmittance of the pixel corresponding to the brightness, and the control means has the light transmittance and the display brightness of the image. Display showing relationship with The light transmittance of the pixel corresponding to the light emission brightness of the plurality of light sources is set based on the brightness characteristic, and the display brightness characteristic is such that the display brightness of the image having a predetermined light transmittance or less is other than zero. And a value lower than the reference display luminance characteristic when the light emission luminances of the plurality of light sources are set to be the same.

  The display control method according to the first aspect of the present invention includes a backlight having a plurality of light sources individually arranged for a plurality of areas obtained by dividing a predetermined display area, and a plurality of pixels corresponding to the display area. A panel that changes the transmittance of light from the light source in units of pixels, and the light emission luminance of the plurality of light sources are individually set according to an image signal, and light emission of the plurality of light sources that are individually set Control means for setting light transmittance of the pixels corresponding to luminance, and in the display control method of a display device for displaying an image corresponding to the image signal in the display region, light emission of the plurality of light sources The brightness is individually set according to the image signal (for example, step S23 in FIG. 12), and is set individually based on the display brightness characteristic representing the relationship between the light transmittance and the display brightness of the image. The plurality of light sources Including the step of setting the light transmittance of the pixel corresponding to the light emission luminance (for example, step S24 in FIG. 12), and the display luminance characteristic is such that the display luminance of the image below a predetermined light transmittance is 0 And a value lower than the reference display luminance characteristic when the light emission luminances of the plurality of light sources are set to be the same.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the liquid crystal display device 1 that is the basis of the present invention will be described with reference to FIG.

  3 includes a color filter substrate colored with R, G, or B, a liquid crystal panel 11 having a liquid crystal layer, a backlight 12 disposed on the back side of the liquid crystal panel 11, and a liquid crystal panel. 11 and the control part 13 which controls the backlight 12, and the memory 14. The liquid crystal display device 1 displays an original image corresponding to the input image signal in a predetermined display area (display unit 21). The image signal input to the liquid crystal display device 1 corresponds to an image having a frame rate of 60 Hz (hereinafter referred to as a field image).

  The liquid crystal panel 11 is provided in a one-to-one correspondence with the display unit 21 in which a plurality of openings serving as pixels that transmit light from the backlight 12 are arranged, and to each pixel constituting the display unit 21. It comprises a source driver 22 and a gate driver 23 for sending drive signals to a transistor (TFT: Thin Film Transistor) not shown.

  The backlight 12 emits white light in a predetermined lighting area corresponding to the display unit 21. The lighting area of the backlight 12 is divided into a plurality of areas, and lighting is individually controlled for each of the divided areas.

In FIG. 3, the lighting area of the backlight 12 is divided into 30 parts, which are divided into 5 parts in the horizontal direction and 6 parts in the vertical direction, and is composed of areas A _{11 to} A ₅₆ . The backlight 12 includes light sources BL _{11 to} BL ₅₆ corresponding to the regions A _{11 to} A ₅₆ .

The light sources BL _ij arranged in the region A _ij (i = 1 to 5, j = 1 to 6) are, for example, red light emitting diodes, green light emitting diodes, and blue light emitting diodes arranged in a predetermined order. Consists of. The light source BL _ij generates white light obtained by mixing red, green, and blue at a luminance corresponding to the backlight control value BLctl _ij supplied from the light source control circuit 33.

Note that the areas A _{11 to} A ₅₆ are not the areas in which the backlight 12 is lit physically divided using partition plates or the like, but are virtually divided as areas corresponding to the light sources BL _{11 to} BL _56. It is. Therefore, light emitted from the light source BL _ij is diffused by the scattering plate or scattering sheet (not shown), not only the region A _ij corresponding to the light source BL _ij, even to a region of the periphery of the area A _ij irradiation Is done.

  The control unit 13 includes a liquid crystal panel control circuit 31 that controls the liquid crystal panel 11, a memory 32, and a light source control circuit 33 that controls the backlight 12.

The liquid crystal panel control circuit 31 is supplied with an image signal corresponding to the field image from another device. The liquid crystal panel control circuit 31 obtains the luminance distribution of the field image from the supplied image signal. Then, the liquid crystal panel control circuit 31 calculates the display luminance Areq _ij necessary for the region A _ij from the luminance distribution of the field image.

As described above, light emitted from the light source BL _ij is not only the front region A _ij of the light source BL _ij, it is also irradiated to a region of the periphery of the area A _ij. Conversely, display brightness AREQ _ij required in the region A _ij, are disposed respectively the light emitted from the light source BL _ij arranged in the rear region A _ij, in the region of the peripheral region A _ij Obtained by synthesis with light from a light source.

The liquid crystal panel control circuit 31 calculates an expression that the display luminance Areq _ij of the region A _ij can be obtained by collecting the contributions of the light emission luminance by the light source BL _ij to the region A _ij from the light sources BL _{11 to} BL _56. by solving ₁₁ to a ₅₆ simultaneous equations stood for each (inequalities), calculates the luminance setting value BLset ₁₁ to BLset ₅₆ sets the light emission intensity of the light source BL ₁₁ to BL _56, supplied to the light source control circuit 33 .

Incidentally, the formula to obtain the display luminance AREQ _ij regions A _ij by gathering a contribution to the region A _ij of the light emission intensity by the light source BL _ij to the light source BL ₁₁ to BL ₅₆ is a light source BL ₁₁ to BL ₅₆ The product sum of the luminance set values BLset _{11 to} BLset ₅₆ and the contribution ratio of the light sources BL _{11 to} BL _{56 to} the region A _ij can be expressed by an expression that represents the display luminance Areq _ij (or higher). Here, the contribution rate of each of the light sources BL _{11 to} BL _{56 to} the region A _ij represents the ratio of the light of each of the light sources BL _{11 to} BL ₅₆ included in the light emitted from the region A _ij and is stored in the memory 14 in advance. ing.

Further, the liquid crystal panel control circuit 31, when the luminance set value BLset ₁₁ to BLset ₅₆ is determined, based on the set gradation conversion table stored in the memory 14, the brightness set value BLset ₁₁ to BLset _56, display The set gradation S_data ′ of each pixel constituting the unit 21 is calculated. The set gradation S_data ′ is an 8-bit value that determines the aperture ratio of the pixel. Then, the liquid crystal panel control circuit 31 supplies the calculated set gradation S_data ′ as a drive control signal to the source driver 22 and the gate driver 23 of the liquid crystal panel 11.

The memory 32 is a control signal that can be received by the backlight 12 as an 8-bit (bit), 256-gradation luminance setting value BLset _ij , which is output from the liquid crystal panel control circuit 31, and is a 10-bit, 1024-gradation control signal. The backlight control value conversion table for conversion to the backlight control value BLctl _ij is stored.

The light source control circuit 33 converts the brightness setting values BLset _{11 to} BLset ₅₆ supplied from the liquid crystal panel control circuit 31 to backlight control values (light source control) based on the backlight control value conversion table stored in the memory 32. Value) Converted to BLctl _{11 to} BLctl ₅₆ and supplied to the backlight 12. As a result, the light source BL _ij arranged in the area A _{ij of the} backlight 12 emits light with a luminance corresponding to the backlight control value BLctl _ij . The backlight control value BLctl _ij is, for example, a current value or a PWM (Pulse Width Modulation) width.

As described above, the memory 14 stores, for example, the contribution ratios of the light sources BL _{11 to} BL ₅₆ for the regions A _{11 to} A _{56 that} are obtained in advance through experiments or the like. Further, the memory 14 stores a set gradation conversion table for converting the luminance setting values BLset _{11 to} BLset ₅₆ into the set gradation S_data ′. The set gradation conversion table will be described later with reference to FIG.

  Next, the display control process of the liquid crystal display device 1 of FIG. 3 will be described with reference to the flowchart of FIG.

  First, in step S1, the liquid crystal panel control circuit 31 receives an image signal supplied from another device. This image signal corresponds to one field image.

In step S2, the liquid crystal panel control circuit 31 obtains the luminance distribution of the field image. In step S2, the liquid crystal panel control circuit 31 calculates display luminance Areq _ij necessary for the region A _ij from the luminance distribution of the field image.

In step S3, the liquid crystal panel control circuit 31, the brightness set value BLset ₁₁ to BLset ₅₆ of the light source BL ₁₁ to BL _56, sum of products and contribution ratio display for the region A _ij of the light source BL ₁₁ to BL ₅₆ luminance AREQ _ij The luminance setting values BLset _{11 to} BLset ₅₆ of the light sources BL _{11 to} BL ₅₆ are calculated by solving the simultaneous equations established for the regions A _{11 to} A _56, respectively, and supplied to the light source control circuit 33. To do.

In step S4, the liquid crystal panel control circuit 31 calculates the set gradation S_data ′ of each pixel of the display unit 21 from the brightness setting values BLset _{11 to} BLset ₅₆ based on the set gradation conversion table stored in the memory 14. calculate.

  In step S <b> 5, the liquid crystal panel control circuit 31 supplies the calculated set gradation S_data ′ as a drive control signal to the source driver 22 and the gate driver 23 of the liquid crystal panel 11.

In step S 6, the light source control circuit 33 uses the 8-bit luminance setting values BLset _{11 to} BLset ₅₆ supplied from the liquid crystal panel control circuit 31 based on the backlight control value conversion table stored in the memory 32. The 10-bit backlight control values BLctl _{11 to} BLctl ₅₆ are converted and supplied to the backlight 12.

  In step S <b> 7, the liquid crystal panel control circuit 31 determines whether the image signal is not supplied. If it is determined in step S7 that an image signal has been supplied, the process returns to step S1, and the processes of steps S1 to S7 are executed. Thereby, the liquid crystal display device 1 displays the next field image.

  On the other hand, if it is determined in step S7 that the image signal is no longer supplied, the process ends.

Thus, an image display method each light source BL ₁₁ to BL ₅₆ controls the backlight 12 so that the optimal (minimum) emission luminance for the field image, hereinafter, referred to as partial control of the backlight . In contrast, the maximum light source BL ₁₁ to BL ₅₆ are substantially, and the conventional image display system for controlling the backlight 12 to have the same emission luminance, hereinafter referred backlight entire controlled.

  The conventional backlight overall control and the backlight partial control by the liquid crystal display device 1 of FIG. 3 will be briefly described with specific numerical examples. Note that actual control is required for each of R, G, and B, but for the sake of simplicity, description will be made with a gray scale (monochrome) of 0 to 255 gradations (8 bits).

  For example, in conventional backlight overall control, when it is necessary to set the display luminance of a predetermined pixel PIX of the display unit 21 to 128 from the supplied image signal, the backlight 12 is uniform for all the pixels of the display unit 21. The pixel PIX has a display luminance of 128 (50% of 255 gradations) by setting the aperture ratio to 50%.

On the other hand, in the backlight partial control by the liquid crystal display device 1 of FIG. 3, for example, the luminance setting value BLset _ij of the light source BL _{ij in} the region A _ij including the pixel PIX is set to 128 (that is, 50% output of the light source BL _ij ). And a display luminance of 128 is realized by setting the aperture ratio to 100% for the pixel PIX.

As a result, it is not necessary to cause the light source BL _ij to emit light with the maximum light emission luminance 255, so that power consumption can be reduced. In this example, the maximum display luminance of the pixels in the area A _ij is 128 of the pixel PIX.

  In the backlight partial control, when the aperture ratio of the pixel PIX is set to 50%, which is the same as the overall backlight control, the display luminance of the pixel PIX is 64, which is half of 128, but in the backlight partial control, the liquid crystal panel control circuit It can be said that No. 31 apparently caused the remaining 64 display luminances to emit light by changing the aperture ratio of the pixel PIX from 50% to 100%. Thus, the luminance increased by changing the aperture ratio from the setting at the time of overall backlight control, in other words, the luminance emitted apparently by the aperture ratio control is referred to as liquid crystal correction luminance in this specification.

  The conventional backlight overall control and backlight partial control will be further described with reference to FIG.

FIG. 5 shows display luminance characteristics representing the relationship between the set gradation corresponding to the aperture ratio and the display luminance [nit = cd / m ² ].

  In FIG. 5, the set gradation is 256 gradations. For example, when the set gradation is set to 0, the aperture ratio is 0%, and when the set gradation is set to 255, the aperture ratio is 100%. Become.

In FIG. 5, a display luminance characteristic f ₁ indicated by a solid curve indicates a display luminance characteristic in the overall backlight control. That is, the display luminance characteristic f ₁ represents the display luminance when the set gradation is set to 0 to 255 in a state where the light source BL _ij is illuminated with 100% output. This display luminance characteristic f ₁ serves as a reference for other display luminance characteristics (display luminance characteristic f ₁ ′ and display luminance characteristic f ₁ ″), which will be described later, and is hereinafter referred to as a reference display luminance characteristic f _1. .

On the other hand, a display luminance characteristic f _LOW indicated by a dotted curve indicates a display luminance characteristic in backlight partial control. That is, the display luminance characteristic f _LOW is obtained when the set gradation is set to 0 to 255 in a state where the light source BL _ij is illuminated with the luminance setting value BLset _ij whose output is suppressed by ε% rather than 100%. Indicates display brightness.

In the liquid crystal display device 1 of FIG. 3, as described above, the luminance setting values BLset _{11 to} BLset _{56 of the} light sources BL _{11 to} BL ₅₆ are obtained from the display luminance Areq _ij necessary in the region A _ij .

Considering that the display brightness is set to L_data in the pixel PIX, in the overall backlight control that illuminates the light source BL _ij with 100% output, the set gradation is set to 65 (= S_data) according to the reference display brightness characteristic f _1. ).

On the other hand, in the backlight partial control, the light source BL _ij illuminates with the brightness setting value BLset _ij whose output is suppressed by ε%. Therefore, in order to set the display brightness to L_data in the pixel PIX, FIG. Thus, it is necessary to set the set gradation to 165 (= S_data ′).

In practice, the liquid crystal display device 1, only the set gradation conversion table corresponding to the reference display brightness characteristic f ₁ is stored in the memory 14, the liquid crystal panel control circuit 31, corresponding to the reference display brightness characteristic f ₁ The set gradation S_data ′ is calculated from the set gradation conversion table to be performed as follows.

First, the liquid crystal panel control circuit 31 calculates the output ratio of the light source BL _ij . That is, the liquid crystal panel control circuit 31 are both 100% identical conditions for numerical aperture, and a display luminance L_peak when illuminating the light source BL _ij at 100% output, the light source BL _ij suppressed output only epsilon% A ratio γ _ij with respect to the display luminance L_set _ij when illuminated with the luminance setting value BLset _ij is obtained by the equation (1).

γ _ij = L_peak / L_set _ij (1)

Next, the liquid crystal panel control circuit 31 calculates the set gradation S_data ′ of the pixel PIX based on the ratio γ _ij between the display luminance L_peak and the display luminance L_set _ij and the display luminance L_data according to Expression (2).

S_data ′ = f ⁻¹ (γ _ij × L_data) (2)

In order to obtain the display luminance L_data by the light source BL _ij that is output while being suppressed by ε% in the backlight partial control, the expression (2) is obtained when the light source BL _ij outputs 100%. This indicates that it is necessary to set the same set gradation S_data ′ (= 165) as when γ _ij × L_data).

As described above, in the backlight partial control by the liquid crystal display device 1, the luminance setting values BLset _{11 to} BLset ₅₆ of the light sources BL _{11 to} BL ₅₆ are set so as to be approximately the same as the display luminance in the overall backlight control. The set gradation S_data ′ of each pixel of the display unit 21 is obtained. However, in the overall backlight control, as shown in FIG. 5, the state where the set gradation S_data is set to 0, that is, the aperture ratio of the pixel is set. Even in the state of 0%, the display luminance becomes a predetermined brightness (about 1.0 nit in FIG. 5), that is, the level representing the black (dark) color (hereinafter referred to as the black level) is optimal. That is, there is a problem that it is not expressed in black.

  Therefore, FIG. 6 shows a configuration example of a liquid crystal display device in which the dynamic range of display luminance is expanded by expressing the black level more black. That is, FIG. 6 is a diagram showing a configuration example of an embodiment of a liquid crystal display device to which the present invention is applied.

  In FIG. 6, portions corresponding to those in FIG. 3 are denoted by the same reference numerals, and description thereof is omitted as appropriate.

  The liquid crystal display device 101 in FIG. 6 includes a liquid crystal panel 11, a backlight 12, a control unit 13, and a memory 121.

The memory 121 is different from the set gradation conversion table representing the reference display brightness characteristic f ₁ in FIG. 5 stored in the memory 14 in FIG. 3, and the set gradation representing the display brightness characteristic f ₁ ′ shown in FIG. A conversion table (hereinafter referred to as a dynamic range expansion compatible setting gradation conversion table) is stored.

The display luminance characteristic f ₁ ′ in FIG. 7 has a characteristic that the display luminance for a set gradation of about 50 or less is lower than the reference display luminance characteristic f ₁ . In other words, the display luminance characteristic f ₁ ′ is 0.5 nit when the set gradation is 0, that is, when the aperture ratio of the pixel is 0%, and the display brightness is 10 nit when the set gradation is around 50. Thus, the change (that is, the inclination) of the display luminance per set gradation 1 between the set gradations 0 to 50 is a curve larger than the reference display luminance characteristic f ₁ . Here, the display luminance when the set gradation is 0, that is, when the aperture ratio of the pixel is 0% is referred to as offset OFFSET, and in the display luminance characteristic f ₁ ′ in FIG. 7, the offset OFFSET = 0.5.

When the display luminance Areq _ij as the display luminance L_data is about 10 nits or less, the output suppression rate ε ′ of the light source BL _ij is smaller than ε for the reference display luminance characteristic f _{1 in} FIG. 5 (ε ′ < ε), so γ _ij ′ also becomes smaller. Accordingly, the liquid crystal correction brightness corresponding to the difference between the display brightness based on the set gradation S_data and the display brightness based on the set gradation S_data ′ is also reduced.

  As a result, the liquid crystal display device 101 can express the black level blacker than the liquid crystal display device 1, and can expand the dynamic range of display luminance.

With reference to FIGS. 8 to 10, the set gradation conversion table represented by the reference display luminance characteristic f ₁ (FIG. 5) and the dynamic range corresponding setting floor represented by the display luminance characteristic f ₁ ′ (FIG. 7). A difference in effect due to the key conversion table will be described.

FIG. 8 shows the result of processing the original image P1 ′ shown in FIG. 2 by the liquid crystal display device 1 of FIG. 3 in accordance with the set gradation conversion table represented by the reference display luminance characteristic f ₁ (FIG. 5). Yes.

  FIG. 8A shows an original image P1 'similar to FIG. In FIGS. 8 to 10, the luminance of a region (hereinafter referred to as a target region) composed of a plurality of pixels on the horizontal dotted line in the original image P1 ′ in FIG. 8A will be considered.

  FIG. 8B shows the original image luminance which is the luminance of the target area of the original image P1 '. That is, as shown in FIG. 8B, the original image luminance of the region R2 'of the original image P1' is 0, and the original image luminance of the region R1 'is 30.

FIG. 8C shows the light emission luminance by the light source BL _ij of the backlight 12 with respect to the target region. Here, in order to simplify the description, it is assumed that the light source BL _ij is located at the center (center) of the region R1 ′ of the original image P1 ′.

FIG. 8D shows the liquid crystal correction luminance for the target area. The liquid crystal correction brightness when the original image brightness is 0 corresponds to the set gradation 0 of the reference display brightness characteristic f ₁ in FIG. 5 and is about 1.0 nit.

  FIG. 8E shows display luminance obtained by combining the light emission luminance of the backlight 12 of FIG. 8C and the liquid crystal correction luminance of FIG. 8D. That is, the display brightness of each pixel is expressed by the light emission brightness of the backlight 12 × the liquid crystal correction brightness.

In the display luminance shown in FIG. 8E, the boundary between the region R1 ′ and the region R2 ′ of the original image P1 ′ is clearly distinguished. Further, the display brightness of the region R2 ′, which is the darkest part of the original image P1 ′, is about 1.0 nit, which is the same as the offset OFFSET of the reference display brightness characteristic f ₁ in FIG. The darkest display luminance level corresponding to the original image luminance 0 of the original image P1 ′ is hereinafter referred to as the lowest luminance level.

FIG. 9 shows the result of processing the original image P1 ′ shown in FIG. 2 by the liquid crystal display device 101 of FIG. 5 according to the dynamic range corresponding set gradation conversion table represented by the display luminance characteristic f ₁ ′ (FIG. 7). Is shown.

  9A to 9C are the same as FIGS. 8A to 8C, respectively, and description thereof is omitted.

FIG. 9D shows the liquid crystal correction luminance with respect to the target area, similar to FIG. 8D. The liquid crystal correction luminance when the original image luminance is 0 corresponds to the display tone characteristic f ₁ ′ set gradation 0 of FIG. 7 and is about 0.5 nit.

As a result, as shown in FIG. 9E, the display luminance corresponding to the region R1 ′ of the original image P1 ′ remains at the same level as in FIG. 8E, and the minimum luminance level is the reference indicated by the one-dot chain line. It is lower (blacker) than the lowest luminance level when the display luminance characteristic f ₁ is used. That is, the black level is displayed in black, and the dynamic range of display brightness is expanded.

  Therefore, according to the liquid crystal display device 101 of FIG. 5, the dynamic range of display luminance can be expanded as compared with the liquid crystal display device 1 of FIG. 3.

As the offset OFFSET in the display luminance characteristic f ₁ ′ is set to a smaller value, the minimum luminance level can be brought closer to 0 and the dynamic range of the display luminance can be expanded. However, the offset OFFSET is 0 Any value other than.

FIG. 10 shows a processing result when the offset OFFSET in the display luminance characteristic f ₁ ′ is set to 0.

When the offset OFFSET in the display luminance characteristic f ₁ ′ is 0, when the original image luminance is 0, L_peak is 0, so γ _{ij in} equation (1) is also 0, and S_data ′ = 0, that is, as shown in FIG. 10D. Thus, the liquid crystal correction luminance becomes zero. As a result, the light emission luminance of the backlight 12 in the shaded area in FIG. 10C appears as display luminance as it is as shown in FIG. 10E.

That is, of the 'region R2 of the' original image P1, region R1 'pixels around the regions R1' becomes brighter as pulled luminance was set to 0 an offset OFFSET of the display luminance characteristic f ₁ ' In this case, although the lowest luminance level can be made the lowest, black unevenness occurs.

On the other hand, as shown in FIG. 9, when the offset OFFSET in the display luminance characteristic f ₁ ′ is set to 0.5, black unevenness hardly occurs.

Accordingly, as shown in FIG. 7, the set gradation conversion table corresponding to the dynamic range expansion stored in the memory 121 is displayed with an offset OFFSET other than 0 and less than a predetermined set gradation (about 50 or less in FIG. 7). By making the luminance correspond to the display luminance characteristic f ₁ ′ set to a value lower than the reference display luminance characteristic f ₁ , the dynamic range of the display luminance can be expanded while suppressing black unevenness.

Therefore, as shown in FIG. 11, for example, it is possible to employ a display luminance characteristic f ₁ ″ with an offset OFFSET of 0.1.

  FIG. 12 shows a flowchart of display control processing by the liquid crystal display device 101.

  The processes in steps S21 to S27 in FIG. 12 are basically the same as the processes in steps S1 to S7 in FIG. 4 described above, and a description thereof will be omitted.

However, in step S24, the liquid crystal panel control circuit 31 uses the brightness setting values BLset _{11 to} BLset ₅₆ based on the set gradation conversion table corresponding to the dynamic range expansion stored in the memory 121 to display each pixel of the display unit 21. The only difference is that the set gradation S_data ′ is calculated.

As described above, according to the liquid crystal display device 101 of FIG. 5, the display brightness is predetermined as compared with the reference display brightness characteristic f ₁ representing the relationship between the set gradation S_data and the display brightness L_data in the overall backlight control. Based on the set gradation conversion table corresponding to the dynamic range expansion corresponding to the display luminance characteristic (display luminance characteristic f ₁ ′ in FIG. 7 or display luminance characteristic f ₁ ″ in FIG. 11) that is lower than the set gradation, By calculating the set gradation S_data ′ of each pixel of the display unit 21 from the set values BLset _{11 to} BLset ₅₆ , the dynamic range of display luminance can be expanded while suppressing black unevenness.

In the above-described example, the dynamic range expansion corresponding setting gradation conversion table corresponding to any _one of the display luminance characteristics f ₁ ′ or f ₁ ″ is stored in the memory 121. For example, the display luminance characteristics A plurality of dynamic range expansion compatible set gradation conversion tables, such as a dynamic range expansion compatible set gradation conversion table corresponding to f ₁ ′, and a dynamic range expansion compatible set gradation conversion table corresponding to the display luminance characteristic f ₁ ″ are stored in memory. 121, the display luminance characteristic to be used for the target pixel is selected according to the luminance distribution of the luminance of the pixels around the target pixel when each pixel of the original image is the target pixel. The set gradation conversion table corresponding to the dynamic range expansion corresponding to the selected display luminance characteristic can be used.

In this case, when the amount of change in the luminance of the surrounding pixels is larger than the target pixel, the offset OFFSET is close to the offset OFFSET of the reference display luminance characteristic f ₁ (for example, the display luminance characteristic f ₁ ′). If the change in luminance of the surrounding pixels is small relative to the target pixel using the dynamic range expansion setting gradation conversion table, the offset OFFSET is close to 0 display luminance characteristics (for example, display luminance characteristics By using the dynamic range expansion compatible setting gradation conversion table that is f ₁ ″), the dynamic range of display luminance can be expanded while suppressing black unevenness. Display luminance characteristics may be selected in units of one field image.

  FIG. 13 is a diagram showing a configuration example of another embodiment of a liquid crystal display device to which the present invention is applied.

  In FIG. 13, portions corresponding to those in FIG. 6 are denoted with the same reference numerals, and description thereof will be omitted as appropriate.

  A liquid crystal display device 201 in FIG. 13 includes a liquid crystal panel 11, a backlight 12, a control unit 13, and a memory 211.

  The control unit 13 includes a liquid crystal panel control circuit 221 that controls the liquid crystal panel 11, a memory 32, and a light source control circuit 33 that controls the backlight 12. In other words, the control unit 13 of the liquid crystal display device 201 is provided with a liquid crystal panel control circuit 221 instead of the liquid crystal panel control circuit 31.

  The liquid crystal panel control circuit 221 uses an image signal having a predetermined original image luminance based on a zero gradation conversion table stored in the memory 211, based on an image signal having an original image luminance of 0 among image signals supplied from other devices. Convert to signal. The liquid crystal panel control circuit 221 also performs the same processing as the liquid crystal panel control circuit 31 in FIG.

The memory 211 stores a dynamic range expansion compatible setting gradation conversion table different from the dynamic range expansion compatible setting gradation conversion table representing the display luminance characteristic f ₁ ′ of FIG. 7 stored in the memory 121 of FIG.

The set gradation conversion table corresponding to the dynamic range expansion stored in the memory 211 is a display luminance characteristic having the same tendency as the display luminance characteristic f ₁ ′ of FIG. 7 and has an offset OFFSET of 0. is there. Hereinafter, the setting gradation conversion table corresponding to the dynamic range expansion stored in the memory 211 is distinguished from the above-described dynamic gradation expansion setting gradation conversion table, and is referred to as a 0 gradation dynamic range expansion corresponding setting gradation conversion table. , the display brightness characteristic corresponding to the dynamic range expansion corresponds set gray scale conversion table for the 0th gradation and the display brightness characteristic f _2.

Note that since the vertical axis in FIG. 7 is a logarithmic axis, the display luminance cannot be zero, so the display luminance characteristic f ₂ is not shown, but the 0-gradation dynamic range expansion stored in the memory 211 is supported. In the set gradation conversion table, the display brightness when the set gradation is 0 is set to 0.

  The memory 211 also stores a 0 gradation conversion table.

  The 0 gradation conversion table stored in the memory 211 will be described with reference to FIG.

  The 0 gradation conversion table is a table for converting an image signal having an original image luminance of 0 among image signals supplied from other devices into an image signal having a predetermined original image luminance. The 0 gradation conversion table is represented by a function h shown in FIG. The function h has a larger value of the original image luminance as the distance from the target pixel to the pixel whose original image luminance is other than 0 becomes longer when a predetermined pixel having the original image luminance of 0 is the target pixel. In other words, when the distance from the target pixel to a pixel whose original image luminance is other than 0 is converted to bright luminance, the converted original image luminance is a constant conversion value TG. FIG. 14 shows an example in which the conversion value TG is set to 10.

  Note that the distance from the target pixel to the pixel whose original image luminance is other than 0 may be a distance in a predetermined direction such as the horizontal direction or the vertical direction, or may be a distance around the target pixel. It is good also as an average value of distance about all directions.

  FIG. 15 shows the result of processing the original image P1 ′ shown in FIG. 2 by the liquid crystal display device 201 of FIG. 13 according to the setting gradation conversion table corresponding to the 0 gradation dynamic range expansion and the 0 gradation conversion table. Yes.

  FIG. 15A shows an original image P1 'similar to FIG. In FIG. 15 as well, as in the example described above, the luminance of a region (target region) composed of a plurality of pixels in the horizontal direction is considered.

  FIG. 15B shows the original image luminance of the target area, similar to FIG. 8B and the like.

  FIG. 15C shows the original image luminance after the luminance conversion by the 0 gradation conversion table represented by the function h shown in FIG. 14 is performed on the original image luminance shown in FIG. 15B.

FIG. 15D shows the light emission luminance of the light source BL _ij of the backlight 12 with respect to the target region, similar to FIG. 8C and the like.

  FIG. 15E shows the liquid crystal correction luminance for the target region. Since the liquid crystal correction luminance is determined with respect to the original image luminance after conversion in FIG. 15C, it is as shown in FIG. 15E.

  FIG. 15F shows display luminance obtained by combining the light emission luminance of the backlight 12 of FIG. 15D and the liquid crystal correction luminance of FIG. 15E.

  The display brightness shown in FIG. 15F is the same as that in FIG. 8E, the display brightness corresponding to the region R1 ′ of the original image P1 ′ is the same as that in FIG. 8E, and the minimum brightness level is shown in FIG. It is lower (blacker) than the minimum brightness level. That is, the black level is displayed blacker (darker), and the dynamic range of display luminance is expanded.

  Therefore, according to the liquid crystal display device 201 of FIG. 13, the dynamic range of display luminance can be expanded as compared with the liquid crystal display device 1 of FIG.

  The display control process of the liquid crystal display device 201 in FIG. 13 will be described with reference to the flowchart in FIG.

  First, in step S41, the liquid crystal panel control circuit 221 receives an image signal supplied from another device. This image signal corresponds to one field image.

  In step S <b> 42, the liquid crystal panel control circuit 221 selects a predetermined original image signal based on a 0 gradation conversion table stored in the memory 211, from among image signals supplied from other devices. Convert to image luminance image signal.

In step S43, the liquid crystal panel control circuit 221 obtains the luminance distribution of the field image. In step S43, the liquid crystal panel control circuit 221 calculates the display luminance Areq _ij necessary for the region A _ij from the luminance distribution of the field image. Here, the original image luminance after the conversion in the process of step S42 is used for the pixel having the original image luminance of zero.

In step S44, the liquid crystal panel control circuit 221, the brightness set value BLset ₁₁ to BLset ₅₆ of the light source BL ₁₁ to BL _56, sum of products and contribution ratio display for the region A _ij of the light source BL ₁₁ to BL ₅₆ luminance AREQ _ij The luminance setting values BLset _{11 to} BLset ₅₆ of the light sources BL _{11 to} BL ₅₆ are calculated by solving the simultaneous equations established for the regions A _{11 to} A _56, respectively, and supplied to the light source control circuit 33. To do.

In step S <b> 45, the liquid crystal panel control circuit 221 uses the brightness setting values BLset _{11 to} BLset ₅₆ based on the set gradation conversion table corresponding to the 0 gradation dynamic range expansion stored in the memory 211 to display each of the display unit 21. A set gradation S_data ′ of the pixel is calculated.

  In step S <b> 46, the liquid crystal panel control circuit 221 supplies the calculated set gradation S_data ′ as a drive control signal to the source driver 22 and the gate driver 23 of the liquid crystal panel 11.

In step S47, the light source control circuit 32 converts the 8-bit luminance setting values BLset _{11 to} BLset ₅₆ supplied from the liquid crystal panel control circuit 221 to 10-bit backlight control based on the backlight control value conversion table. The values are converted into values BLctl _{11 to} BLctl ₅₆ and supplied to the backlight 12.

  In step S48, the liquid crystal panel control circuit 221 determines whether the image signal is no longer supplied. If it is determined in step S48 that an image signal has been supplied, the process returns to step S41, and the processes of steps S41 to S48 are executed. Thereby, the liquid crystal display device 1 displays the next field image.

  On the other hand, if it is determined in step S48 that the image signal is no longer supplied, the process ends.

As described above, according to the liquid crystal display device 201 of FIG. 13, as shown in FIG. 14, the image signal of the original image luminance 0 among the image signals is converted into the 0 gradation conversion table represented by the function h. Based on the set gradation conversion table corresponding to the 0 gradation dynamic range expansion corresponding to the display brightness characteristic f ₂ that is converted into an image signal having a predetermined original image brightness based on the display brightness characteristic f ₂ where the offset OFFSET is 0 By calculating the set gradation S_data ′ of each pixel of the display unit 21 from BLset _{11 to} BLset ₅₆ , the dynamic range of display luminance can be expanded while suppressing black unevenness.

It should be noted that, instead of the setting gradation conversion table corresponding to the 0 gradation dynamic range expansion corresponding to the display brightness characteristic f ₂ where the offset OFFSET is 0, the display brightness characteristic f ₁ ′ or f ₁ ″ where the offset OFFSET is other than 0 is used. Even when the set gradation S_data ′ of each pixel of the display unit 21 is calculated from the luminance setting values BLset _{11 to} BLset ₅₆ based on the corresponding dynamic range expansion corresponding setting gradation conversion table, while suppressing black unevenness, The dynamic range of display brightness can be expanded.

  In the above-described example, one 0 gradation conversion table represented by the function h with the conversion value TG of 10 is stored in the memory 211. However, the conversion values TG correspond to different functions h. A plurality of 0 gradation conversion tables are stored in the memory 211, and when each pixel of the original image is a target pixel, the target pixel is assigned to the target pixel according to the luminance distribution of the pixels around the target pixel. Alternatively, the 0 gradation conversion table to be used may be properly used.

  Further, for the 0 gradation dynamic range expansion setting gradation conversion table, a plurality of 0 gradation dynamic range expansion setting gradation conversion tables having different offsets OFFSET are stored in the memory 211, so that Depending on the luminance distribution of the pixel luminance, the set gradation conversion table corresponding to the 0 gradation dynamic range expansion to be used for the target pixel can be used properly.

  In the example described above, an example in which an image is displayed at a frame rate of 60 Hz has been described. However, the frame rate (display rate) of the image is not limited to 60 Hz, and may be smaller than 60 Hz or larger than 60 Hz.

In addition, the areas A _{11 to} A ₅₆ are areas obtained by virtually dividing the lighting area of the backlight 12, but a partition plate or the like is provided between each of the areas A _{11 to} A ₅₆ and is physically divided. Also good.

  In the present specification, the steps described in the flowcharts are executed in parallel or individually even if they are not necessarily processed in time series, as well as processes performed in time series in the described order. It also includes processing.

  In the present invention, a backlight 12 that can be turned on individually for each of a plurality of divided areas is arranged on the back side of the display panel 11, and the backlight partial control of the backlight 12 and the aperture ratio of the pixels of the display panel 11 are controlled. The control can be applied to a liquid crystal display device that displays an image.

  The embodiment of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

It is a figure explaining control of the conventional backlight. It is a figure explaining black nonuniformity. It is a figure which shows the structural example of the liquid crystal display device used as the foundation of this invention. 4 is a flowchart illustrating display control processing of the liquid crystal display device of FIG. 3. It is a figure explaining backlight whole control and backlight partial control. It is a figure which shows the structural example of one Embodiment of the liquid crystal display device to which this invention is applied. It is a diagram illustrating a display luminance characteristic f ₁ '. It is a figure which shows the result of having processed the original image according to the setting gradation conversion table. It is a figure which shows the result of having processed the original image according to the dynamic range corresponding setting gradation conversion table. It is a figure which shows the result of having processed the original image according to the dynamic range corresponding | compatible setting gradation conversion table which made offset OFFSET 0. An offset OFFSET is a diagram showing an example of a display luminance characteristic f ₁ "that was 0.1. It is a flowchart explaining the display control process of the liquid crystal display device of FIG. It is a figure which shows the structural example of other embodiment of the liquid crystal display device to which this invention is applied. It is a figure explaining a 0 gradation conversion table. It is a figure which shows the result of having processed the original image according to the 0 gradation conversion table. It is a flowchart explaining the display control processing of the liquid crystal display device of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Liquid crystal display device, 11 Liquid crystal panel, 12 Backlight, 13 Control part, 14 Memory, 21 Display part, 31 Liquid crystal panel control circuit, 32 Memory, 33 Light source control circuit, 101 Liquid crystal display device, 121 Memory, 201 Liquid crystal display device , 211 Memory, 221 LCD panel control circuit

Claims (6)

In a display device that displays an image corresponding to an image signal in a predetermined display area,
A backlight having a plurality of light sources individually arranged corresponding to a plurality of areas obtained by dividing the display area;
A panel having a plurality of pixels corresponding to the display area, and changing the transmittance of light from the light source in units of pixels;
Control means for individually setting light emission luminances of the plurality of light sources according to the image signal and setting light transmittances of the pixels corresponding to the light emission luminances of the plurality of light sources set individually; With
The control means sets the light transmittance of the pixel corresponding to the light emission luminance of the plurality of light sources based on a display luminance characteristic representing a relationship between the light transmittance and the display luminance of the image,
The display luminance characteristic is lower than a reference display luminance characteristic when the display luminance of the image below a predetermined light transmittance is a value other than 0 and the emission luminances of the plurality of light sources are set to be the same. Value display device. Storage means for storing data corresponding to a plurality of display luminance characteristics, each of which has a display luminance of the image equal to or lower than the predetermined light transmittance;
The control means further selects one of the display luminance characteristics from the plurality of display luminance characteristics according to the luminance distribution of the image, and based on the selected display luminance characteristics, the plurality of light sources The display device according to claim 1, wherein the light transmittance of the pixel corresponding to the light emission luminance is set. A backlight having a plurality of light sources arranged separately for each of a plurality of areas obtained by dividing a predetermined display area, and a plurality of pixels corresponding to the display area, and the transmittance of light from the light source in pixel units And the light emission luminance of the plurality of light sources are individually set according to an image signal, and the light transmittance of the pixel is set in accordance with the light emission luminance of the plurality of light sources set individually. In a display control method of a display device for displaying an image corresponding to the image signal in the display area,
The emission brightness of the plurality of light sources is individually set according to the image signal,
Setting the light transmittance of the pixels corresponding to the light emission luminances of the plurality of light sources set individually based on display luminance characteristics representing the relationship between the light transmittance and the display luminance of the image; Including
The display luminance characteristic is lower than a reference display luminance characteristic when the display luminance of the image below a predetermined light transmittance is a value other than 0 and the emission luminances of the plurality of light sources are set to be the same. Value display control method. In a display device that displays an image corresponding to an image signal in a predetermined display area,
A backlight having a plurality of light sources individually arranged corresponding to a plurality of areas obtained by dividing the display area;
A panel having a plurality of pixels corresponding to the display area, and changing the transmittance of light from the light source in units of pixels;
Conversion means for converting the image signal according to a predetermined function;
The light emission luminances of the plurality of light sources are individually set according to the image signals converted by the conversion means, and the light emission luminances of the pixels corresponding to the light emission luminances of the plurality of light sources set individually are set. Control means for setting the transmittance, and
The control means sets the light transmittance of the pixel corresponding to the light emission luminance of the plurality of light sources based on a display luminance characteristic representing a relationship between the light transmittance and the display luminance of the image,
The display luminance characteristic is lower than a reference display luminance characteristic when the display luminance of the image below a predetermined light transmittance is a value other than 0 and the emission luminances of the plurality of light sources are set to be the same. Value display device. Storage means for storing data corresponding to a plurality of display luminance characteristics, each of which has a display luminance of the image equal to or lower than the predetermined light transmittance;
The control means further selects one display luminance characteristic from among the plurality of display luminance characteristics according to the luminance distribution of the image, and based on the selected display luminance characteristic, the light of the pixel The display device according to claim 4, wherein the transmittance is set. A backlight having a plurality of light sources arranged separately for each of a plurality of areas obtained by dividing a predetermined display area, and a plurality of pixels corresponding to the display area, and the transmittance of light from the light source in pixel units A panel for changing the image signal, conversion means for converting the image signal in accordance with a predetermined function, and emission brightness of the plurality of light sources are individually set according to the image signal converted by the conversion means, and individually set A display control method for displaying an image corresponding to the image signal in the display area, the control means setting the light transmittance of the pixel corresponding to the light emission luminance of the plurality of light sources. In
Converting the image signal according to a predetermined function;
The emission brightness of the plurality of light sources is individually set according to the converted image signal,
Setting the light transmittance of the pixels corresponding to the light emission luminances of the plurality of light sources set individually based on display luminance characteristics representing the relationship between the light transmittance and the display luminance of the image; Including
The display luminance characteristic is lower than a reference display luminance characteristic when the display luminance of the image below a predetermined light transmittance is a value other than 0 and the emission luminances of the plurality of light sources are set to be the same. Value display control method.

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