Patent Application
20190139500
The present invention relates to a display apparatus and a control method thereof.
Recently, a double liquid crystal technique in which two liquid crystal panels are used after being stacked on top of each other is being put to practical use as a technique for realizing high contrast display by a liquid crystal display apparatus. Since each liquid crystal panel is structured such that a liquid crystal layer is sandwiched between two glass plates, a space is created between the two liquid crystal layers respectively corresponding to the two liquid crystal panels. Therefore, when transmittances of the respective liquid crystal panels are controlled to the same transmittance, an image displayed on a rear surface-side liquid crystal panel does not overlap with an image displayed on a front surface-side liquid crystal panel and a double image is observed when a screen is viewed obliquely.
As a technique for reducing the double image, a technique involving reducing a spatial frequency of an image displayed on the rear surface-side liquid crystal panel is proposed. However, using such a technique results in an occurrence of a halo phenomenon in an image displayed on the screen (display image) and causes a contrast of the display image to decline. A halo phenomenon refers to a phenomenon in which a periphery of a bright part blurs brightly.
As a technique for solving these problems, a technique is proposed which involves switching display modes between a wide viewing angle mode and a narrow viewing angle mode in accordance with contents (a text, a graphic pattern, a natural image, and the like) of an input image (Japanese Patent Application Laid-open No. 2017-26992). A spatial frequency of an image displayed on a rear surface-side liquid crystal panel is only reduced in the narrow viewing angle mode.
As another technique, a technique is proposed which involves detecting maximum transmittance (a maximum gradation value) of an input image and controlling transmittance of a rear surface-side liquid crystal panel to transmittance equal to or higher than the detected maximum gradation value (Japanese Patent Application Laid-open No. 2013-156658).
However, with the technique disclosed in Japanese Patent Application Laid-open No. 2017-26992, when a text and a natural image are both present in an input image, reduction of a double image and high contrast display cannot be both realized regardless of which display mode between the wide viewing angle mode and the narrow viewing angle mode is being set. With the technique disclosed in Japanese Patent Application Laid-open No. 2013-156658, the transmittance of the rear surface-side liquid crystal panel is increased. Therefore, when a spatial frequency of an image displayed on the rear surface-side liquid crystal panel is reduced, a halo phenomenon occurs more prominently. In addition, unless the spatial frequency of the image displayed on the rear surface-side liquid crystal panel is reduced, a double image occurs more prominently. As described above, with conventional techniques, reduction of a double image and suppression of other types of image quality deterioration (an occurrence of a halo phenomenon, a decline in contrast, and the like) cannot be realized at the same time.
The present invention in its first aspect provides a display apparatus comprising:
a backlight module;
a first panel transmitting a light from the backlight module based on a first image data;
a second panel displaying an image on a display area by transmitting a light from the first panel based on a second image data; and
at least one processor and/or at least one circuit to perform the operations of the following units:
an acquiring unit configured to acquire an input image data; and
a generating unit configured to generate the first image data and the second image data based on the input image data,
wherein the generating unit generates the first image data and the second image data such that a decline in transmittance of the second panel due to an increase in a line-of-sight angle which is an angle of a line-of-sight direction relative to the display area becomes larger than a decline in transmittance of the first panel due to the increase in the line-of-sight angle.
The present invention in its second aspect provides a display apparatus comprising:
a backlight module:
a first panel transmitting a light from the backlight module based on a first image data;
a second panel displaying an image on a display area by transmitting a light from the first panel based on a second image data; and
at least one processor and/or at least one circuit to perform the operations of the following units:
a first acquiring unit configured to acquire an input image data;
a second acquiring unit configured to acquire a parameter corresponding to a temperature of the display apparatus; and
a generating unit configured to generate the first image data and the second image data from the input image data based on the parameter.
The present invention in its third aspect provides a control method for a display apparatus including a backlight module, a first panel transmitting a light from the backlight module based on a first image data, and a second panel displaying an image on a display area by transmitting a light from the first panel based on a second image data, the control method comprising:
acquiring an input image data and
generating the first image data and the second image data based on the input image data,
wherein the first image data and the second image data are generated such that a decline in transmittance of the second panel due to an increase in a line-of-sight angle which is an angle of a line-of-sight direction relative to the display area becomes larger than a decline in transmittance of the first panel due to the increase in the line-of-sight angle.
The present invention in its fourth aspect provides a control method for a display apparatus including a backlight module, a first panel transmitting a light from the backlight module based on a first image data, and a second panel displaying an image on a display area by transmitting a light from the first panel based on a second image data, the control method comprising:
acquiring an input image data,
acquiring a parameter corresponding to a temperature of the display apparatus; and
generating the first image data and the second image data from the input image data based on the parameter.
The present invention in its fifth aspect provides a non-transitory computer readable medium that stores a program, wherein
the program causes a computer to execute a control method for a display apparatus including a backlight module, a first panel transmitting a light from the backlight module based on a first image data, and a second panel displaying an image on a display area by transmitting a light from the first panel based on a second image data,
the control method includes:
acquiring an input image data; and
generating the first image data and the second image data based on the input image data, and
the first image data and the second image data are generated such that a decline in transmittance of the second panel due to an increase in a line-of-sight angle which is an angle of a line-of-sight direction relative to the display area becomes larger than a decline in transmittance of the first panel due to the increase in the line-of-sight angle.
The present invention in its sixth aspect provides a non-transitory computer readable medium that stores a program, wherein
the program causes a computer to execute a control method for a display apparatus including a backlight module, a first panel transmitting a light from the backlight module based on a first image data, and a second panel displaying an image on a display area by transmitting a light from the first panel based on a second image data.
the control method includes:
acquiring an input image data;
acquiring a parameter corresponding to a temperature of the display apparatus; and
generating the first image data and the second image data from the input image data based on the parameter.
Further features of the present invention will become apparent from the following description of exemplar) embodiments with reference to the attached drawings.
A first embodiment of the present invention will be described below.
The control unit 101 controls processes of the respective functional units of the display apparatus 10. In
The image acquiring unit 103 acquires image data (input image data; an input image signal) from outside of the display apparatus 10 and outputs the input image data to the inverse γ processing unit 109. Alternatively, the image acquiring unit 103 may acquire the input image data from the storage unit 102.
The information acquiring unit 104 acquires (generates) double image reduction information indicating a degree of reduction of a double image in accordance with a user operation. Specifically, the information acquiring unit 104 acquires double image reduction information indicating a degree of reduction specified by a user. In addition, the information acquiring unit 104 outputs the double image reduction information to the γ setting unit 108. Alternatively, the information acquiring unit 104 may acquire the double image reduction information from outside of the display apparatus 10 or may acquire the double image reduction information from the storage unit 102.
The backlight unit 105 is a light-emitting unit that irradiates light on a rear surface of the first liquid crystal panel 106. Hereinafter, a direction from the backlight unit 105 toward a screen (a surface viewed by the user; a display area) will be described as a forward direction.
The first liquid crystal panel 106 is a liquid crystal panel provided on a front side relative to the backlight unit 105. The first liquid crystal panel 106 transmits, at transmittance based on input image data (specifically, first processed image data (a first image signal) output from the first γ processing unit 110), light emitted from the backlight unit 105.
The second liquid crystal panel 107 is a liquid crystal panel provided on a front side relative to the first liquid crystal panel 106. The second liquid crystal panel 107 transmits, at transmittance based on input image data (specifically, second processed image data (a second image signal) output from the second γ processing unit 111), light emitted from the backlight unit 105 and transmitted through the first liquid crystal panel 106. Accordingly, an image based on the input image data is displayed on a screen. For example, the screen is a front surface of the second liquid crystal panel 107.
In the present embodiment, an example of so-called normally black will be described in which the larger a gradation value of the input image data, the higher a brightness of the input image data, transmittance of the first liquid crystal panel 106, transmittance of the second liquid crystal panel 107, and the like. Moreover, in the present embodiment, it is assumed that the first liquid crystal panel 106 and the second liquid crystal panel 107 are liquid crystal panels of a same type. With the first liquid crystal panel 106 and the second liquid crystal panel 107, the larger the gradation value of the input image data, the higher the transmittance, and the transmittance takes a maximum value when the gradation value takes a maximum value. Therefore, the first liquid crystal panel 106 and the second liquid crystal panel 107 can be described such that the larger the gradation value of the input image data, the higher a ratio of the transmittance to a maximum value of possible transmittances.
Alternatively, at least one of the first liquid crystal panel 106 and the second liquid crystal panel 107 may not be a liquid crystal panel. Various transmission panels that transmit light at transmittance based on the input image data can be used as the first liquid crystal panel 106 and the second liquid crystal panel 107. For example, at least one of the first liquid crystal panel 106 and the second liquid crystal panel 107 may be a MEMS (Micro Electro Mechanical System) shutter-system display panel.
Moreover, in the present embodiment, the first liquid crystal panel 106 and the second liquid crystal panel 107 each have transmission characteristics such that the higher the transmittance (perpendicular transmittance) of light in a direction (a front direction) perpendicular to the screen, the lower a ratio of oblique transmittance to the perpendicular transmittance. The oblique transmittance is transmittance of light in a direction having a prescribed angle relative to the direction perpendicular to the screen. In other words, with each of the first liquid crystal panel 106 and the second liquid crystal panel 107, the higher the perpendicular transmittance, the lower (more inferior) the viewing angle characteristics.
Viewing angle characteristics of the first liquid crystal panel 106 and the second liquid crystal panel 107 will be described with reference to a drawing.
When a gradation value of image data input to the liquid crystal panel changes, voltage supplied to the liquid crystal panel changes and the transmittance (the perpendicular transmittance or the oblique transmittance) of the liquid crystal panel changes. Viewing angle characteristics 301 in
In the present embodiment, a state where a difference between the perpendicular transmittance and the oblique transmittance is small is considered a state where viewing angle characteristics are high (good). In such a state, differences in brightness and color between an image visible when viewing the screen from an oblique direction and an image visible when viewing the screen from the front direction are small. On the other hand, a state where the difference between the perpendicular transmittance and the oblique transmittance is large is considered a state where viewing angle characteristics are low (inferior). In such a state, differences in brightness and color between an image visible when viewing the screen from an oblique direction and an image visible when viewing the screen from the front direction are large.
As shown in
The γ setting unit 108 sets γ values (γ1 and γ2) to be used by the respective γ processing units (to be described later) to generate processed image data. The γ setting unit 108 sets the γ values such that the viewing angle characteristics of the second liquid crystal panel 107 drop below the viewing angle characteristics of the first liquid crystal panel 106. As described above, with the first liquid crystal panel 106 and the second liquid crystal panel 107, the higher the input gradation value, the larger the ratio of the perpendicular transmittance to the maximum value of the perpendicular transmittance and the lower the viewing angle characteristics. Therefore, the γ setting unit 108 sets each γ value so that each liquid crystal element of the second liquid crystal panel 107 is controlled at a higher gradation value than a corresponding liquid crystal element of the first liquid crystal panel 106. Specifically, the γ setting unit 108 sets each γ value so that the γ value (γ2) for generating image data to be used to control the second liquid crystal panel 107 becomes larger than the γ value (γ1) for generating image data to be used to control the first liquid crystal panel 106. Accordingly, the ratio of the perpendicular transmittance of each liquid crystal element of the second liquid crystal panel 107 to the maximum value of the perpendicular transmittance of the second liquid crystal panel 107 becomes higher than the ratio of the perpendicular transmittance of each liquid crystal element of the first liquid crystal panel 106 to the maximum value of the perpendicular transmittance of the first liquid crystal panel 106.
The larger the γ value, the higher the gradation value at which transmittance is controlled. Therefore, the larger the γ value, the lower the viewing angle characteristics of a realized state. In other words, the γ values (γ1 and γ2) set by the γ setting unit 108 are measures indicating a degree of decline in the viewing angle characteristics of each liquid crystal panel (a degree of decline in transmittance relative to a change in the viewing angle).
In the present embodiment, a degree of decline in the transmittance of the first liquid crystal panel 106 due to an increase in the line-of-sight angle is considered a first measure and a degree of decline in the transmittance of the second liquid crystal panel 107 due to an increase in the line-of-sight angle is considered a second measure. In addition, the γ setting unit 108 sets the first measure and the second measure in accordance with a user operation (specifically, double image reduction information output from the information acquiring unit 104). Specifically, in accordance with the double image reduction information, the γ setting unit 108 determines a first γ value (a first gamma parameter) γ1 as the first measure and determines a second γ value (a second gamma parameter) γ2 as the second measure. Furthermore, the γ setting unit 108 outputs the first γ value γ to the first γ processing unit 110 and outputs the second γ value γ2 to the second γ processing unit 111.
The inverse γ processing unit 109 generates linear image data by performing an inverse γ conversion process of converting the γ characteristics of the input image data output from the image acquiring unit 103 into linear characteristics in which the brightness of image data linearly increases relative to an increase in the gradation value. In addition, the inverse γ processing unit 109 outputs the linear image data to the first γ processing unit 110 and the second γ processing unit 111. While a data format of the input image data is not particularly limited, in the present embodiment, it is assumed that a pixel value of the input image data is an RGB value constituted by an 8-bit R value, an 8-bit G value, and an 8-bit B value and that the γ value of the input image data is 2.2. In addition, the inverse γ processing unit 109 converts each pixel value of the input image data using expressions 1 to 3 below. In expressions 1 to 3, “IV_Rmn” denotes an input R value (an R value of the input image data) of an m-th row, n-th column pixel. “IV_Gmn” denotes an input G value (a G value of the input image data) of the m-th row, n-th column pixel. “IV_Bmn” denotes an input B value (a B value of the input image data) of the m-th row, n-th column pixel. “GV_Rmn” denotes a linear R value (an R value of linear image data) of the m-th row, n-th column pixel. “GV_Gmn” denotes a linear G value (a G value of the linear image data) of the m-th row, n-th column pixel. In addition. “GV_Bmn” denotes a linear B value (a B value of the linear image data) of the m-th row, n-th column pixel. A calculation using the expressions 1 to 3 generates linear image data of which a pixel value is an RGB value constituted by an 8-bit R value, an 8-bit G value, and an 8-bit B value and a γ value is 2.2. Moreover, a data format of the linear image data is not particularly limited.
GV_Rmn=255×(IV_Rmn/255)2.2 (expression 1)
GV_Gmn=255×(IV_Gmn/255)2.2 (expression 2)
GV_Bmn=255×(IV_Bmn/255)2.2 (expression 3)
The first γ processing unit 110 generates first processed image data by performing a first process of converting each gradation value of the input image data (specifically, linear image data output from the inverse γ processing unit 109) so as to satisfy a condition described below. In addition, the first γ processing unit 110 outputs the first processed image data to the first liquid crystal panel 106. The following condition may be restated as “the viewing angle characteristics of the second liquid crystal panel 107 is more inferior than the viewing angle characteristics of the first liquid crystal panel 106”.
Condition: a decline in the transmittance of the second liquid crystal panel 107 due to an increase in a line-of-sight angle is larger than a decline in the transmittance of the first liquid crystal panel 106 due to an increase in the line-of-sight angle.
Specifically, the first γ processing unit 110 generates the first processed image data by performing a γ conversion process using the first γ value γ1 output from the γ setting unit 108 on the input image data (specifically, linear image data). In the present embodiment, the first γ processing unit 110 converts each pixel value of the linear image data using expressions 4 to 6 below. In expressions 4 to 6, “GP1_Rmn” denotes a first R value (an R value of the first processed image data) of an m-th row, n-th column pixel. “GP1_Gmn” denotes a first G value (a G value of the first processed image data) of the m-th row, n-th column pixel. In addition, “GP1_Bmn” denotes a first B value (a B value of the first processed image data) of the m-th row, n-th column pixel. A calculation using the expressions 4 to 6 generates first processed image data of which a pixel value is an RGB value constituted by an 8-bit R value, an 8-bit G value, and an 8-bit B value. Moreover, a data format of the first processed image data is not particularly limited.
GP1_Rmn=255×(GV_Rmn/255)γ1 (expression 4)
GP1_Gmn=255×(GV_Gmn/255)γ1 (expression 5)
GP1_Bmn=255×(GV_Bmn/255)γ1 (expression 6)
The second γ processing unit 111 generates second processed image data by performing a second process of converting each gradation value of the input image data (specifically, linear image data output from the inverse γ processing unit 109) so as to satisfy the condition described above. In addition, the second γ processing unit 111 outputs the second processed image data to the second liquid crystal panel 107. Specifically, the second γ processing unit 111 generates the second processed image data by performing a γ conversion process using the second γ value γ2 output from the γ setting unit 108 on the input image data (specifically, linear image data). In the present embodiment, the second γ processing unit 111 converts each pixel value of the linear image data using expressions 7 to 9 below. In expressions 7 to 9, “GP2_Rmn” denotes a second R value (an R value of the second processed image data) of an m-th row, n-th column pixel. “GP2_Gmn” denotes a second G value (a G value of the second processed image data) of the m-th row, n-th column pixel. In addition, “GP2_Bmn” denotes a second B value (a B value of the second processed image data) of the m-th row, n-th column pixel. A calculation using the expressions 7 to 9 generates second processed image data of which a pixel value is an RGB value constituted by an 8-bit R value, an 8-bit G value, and an 8-bit B value. Moreover, a data format of the second processed image data is not particularly limited.
GP2_Rmn=255×(GV_Rmn/255)γ2 (expression 7)
GP2_Gmn=255×(GV_Gmn/255)γ2 (expression 8)
GP2_Bmn=255×(GV_Bmn/255)γ2 (expression 9)
Since the first γ value γ1 is 1.1, the gradation value of 0.5 (the band 603) of the linear image data is converted into the gradation value of 0.467 (=0.51.1) of first processed image data. In addition, the gradation value of 0.3 (the background 602) of the linear image data is converted into the gradation value of 0.266 (=0.31.1) of the first processed image data. In a similar manner, since the second γ value γ2 is 1.1, the gradation value of 0.5 (the band 603) of the linear image data is converted into the gradation value of 0.467 (=0.51.1) of second processed image data. In addition, the gradation value of 0.3 (the background 602) of the linear image data is converted into the gradation value of 0.266 (=0.31.1) of the second processed image data.
First, a case of a line-of-sight angle of 0 degrees will be considered. In this case, as shown in
Next, a case where the band portion is viewed at a line-of-sight angle of 45 degrees will be considered. Light (the light beam 702) incident from the band portion of the first liquid crystal panel 106 to the band portion of the second liquid crystal panel 107 is light having been transmitted through the first liquid crystal panel 106 at the transmittance of 0.467 of the line-of-sight angle of 0 degrees. Therefore, the brightness of the light (the light beam 702) incident from the band portion of the first liquid crystal panel 106 to the band portion of the second liquid crystal panel 107 is 0.467 (=0.467×1). In addition, the transmittance of the band portion of the second liquid crystal panel 107 is the transmittance of 0.233 corresponding to the line-of-sight angle of 45 degrees and the gradation value of 0.467 in the table shown in
Next, a case where the background portion (specifically, a portion into which light from the band portion of the first liquid crystal panel 106 leaks in the background portion) is viewed at the line-of-sight angle of 45 degrees will be considered. Light (the light beam 703) incident from the band portion of the first liquid crystal panel 106 to the background portion of the second liquid crystal panel 107 is light having been transmitted through the first liquid crystal panel 106 at the transmittance of 0.233 which corresponds to the line-of-sight angle of 45 degrees and the gradation value of 0.467 in the table shown in
Since the first γ value γ1 is 1.7, the gradation value of 0.5 (the band 603) of the linear image data is converted into the gradation value of 0.308 (=0.5′) of first processed image data. In addition, the gradation value of 0.3 (the background 602) of the linear image data is converted into the gradation value of 0.129 (=0.31.7) of the first processed image data. In a similar manner, since the second γ value γ2 is 0.5, the gradation value of 0.5 (the band 603) of the linear image data is converted into the gradation value of 0.707 (=0.50.5) of second processed image data. In addition, the gradation value of 0.3 (the background 602) of the linear image data is converted into the gradation value of 0.548 (=0.30.5) of the second processed image data.
First, a case of a line-of-sight angle of 0 degrees will be considered. In this case, as shown in
Next, a case where the band portion is viewed at a line-of-sight angle of 45 degrees will be considered. Light (the light beam 702) incident from the band portion of the first liquid crystal panel 106 to the band portion of the second liquid crystal panel 107 is light having been transmitted through the first liquid crystal panel 106 at the transmittance of 0.308 of the line-of-sight angle of 0 degrees. Therefore, the brightness of the light (the light beam 702) incident from the band portion of the first liquid crystal panel 106 to the band portion of the second liquid crystal panel 107 is 0.308 (=0.308×1). In addition, the transmittance of the band portion of the second liquid crystal panel 107 is the transmittance of 0.255 corresponding to the line-of-sight angle of 45 degrees and the gradation value of 0.707 in the table shown in
Next, a case where the background portion (specifically, a portion into which light from the band portion of the first liquid crystal panel 106 leaks in the background portion) is viewed at the line-of-sight angle of 45 degrees will be considered. Light (the light beam 703) incident from the band portion of the first liquid crystal panel 106 to the background portion of the second liquid crystal panel 107 is light having been transmitted through the first liquid crystal panel 106 at the transmittance of 0.185 which corresponds to the line-of-sight angle of 45 degrees and the gradation value of 0.308 in the table shown in
The perceived brightness of 0.040 of the band 603 in the background portion is lower than the perceived brightness of 0.041 according to conventional art (
Next, the fact that a similar effect to that described above can be obtained even when the gradation value of the linear image data shown in
A case where the background portion is viewed at a line-of-sight angle of 45 degrees will now be considered. The transmittance of the background portion of the second liquid crystal panel 107 is the transmittance of 0.007 corresponding to the line-of-sight angle of 45 degrees and the gradation value of 0.0 in the table shown in
A case where the background portion is viewed at a line-of-sight angle of 45 degrees will now be considered. The transmittance of the background portion of the second liquid crystal panel 107 is the transmittance of 0.007 corresponding to the line-of-sight angle of 45 degrees and the gradation value of 0.0 in the table shown in
The perceived brightness of 0.001 of the band 603 in the background portion is half of the perceived brightness of 0.002 according to conventional art (
As described above, according to the present embodiment, image display is performed so that the viewing angle characteristics of the second liquid crystal panel 107 becomes inferior to the viewing angle characteristics of the first liquid crystal panel 106. In other words, image display is performed so that a decline in the transmittance of the second liquid crystal panel 107 due to an increase in a line-of-sight angle is larger than a decline in the transmittance of the first liquid crystal panel 106 due to an increase in the line-of-sight angle. Accordingly, a double image can be reduced. In addition, since image processing for reducing a spatial frequency of an image or the like is not particularly performed, other types of image quality deterioration (an occurrence of a halo phenomenon, a decline in contrast, and the like) can also be suppressed.
Note that the γ characteristics of the double liquid crystal panel is not limited to γ characteristics expressed as γ value=γ1+γ2=2.2. In addition, the first liquid crystal panel 106 may or may not be a liquid crystal panel capable of displaying color images. The first liquid crystal panel 106 may be a liquid crystal panel that displays monochrome images.
While an example has been described in which an increase in the gradation value causes viewing angle characteristics to deteriorate, the viewing angle characteristics may deteriorate due to a decrease in the gradation value. In this case, for example, a γ value larger than the first γ value γ1 may be used as the second γ value γ2. In addition, while an example of normally black has been described, so-called normally white may be adopted instead in which the larger the gradation value of the input image data, the lower the brightness of the input image data, the transmittance of the first liquid crystal panel 106, the transmittance of the second liquid crystal panel 107, and the like.
The display apparatus may execute a blurring process for obtaining first processed image data having a lower spatial frequency than a spatial frequency of second processed image data. The blurring process is, for example, a filtering process using a smoothing filter such as a Gaussian filter.
Note that the first process is not limited to the γ conversion process using the first γ value γ1. The first process may include the γ conversion process using the first γ value γ1 and other image processing. In addition, the second process is not limited to a γ conversion process using the second γ value γ2. The second process may include the γ conversion process using the second γ value γ2 and other image processing.
A second embodiment of the present invention will be described below. In the first embodiment, an example of setting a first measure (the first γ value γ1) and a second measure (the second γ value γ2) in accordance with a user operation has been described. In the present embodiment, an example of setting the first measure and the second measure in accordance with input image data will be described. Hereinafter, points (configurations and processes) that differ from those of the first embodiment will be described in detail and descriptions of points that are the same as those of the first embodiment will be omitted.
The expansion/compression parameter setting unit 201 sets the first measure and the second measure in accordance with input image data (specifically, linear image data output from the inverse γ processing unit 109). In the present embodiment, the expansion/compression parameter setting unit 201 determines an expansion/compression parameter in accordance with the linear image data. In addition, the expansion/compression parameter setting unit 201 outputs the expansion/compression parameter to the expanding unit 202 and the compressing unit 203. Specifically, the expansion/compression parameter setting unit 201 determines an expansion/compression parameter of each pixel using expressions 10 to 12 below. In expressions 10 to 12, “AM_R” denotes an expansion/compression parameter corresponding to an R component of an m-th row, n-th column pixel, “AM_G” denotes an expansion/compression parameter corresponding to a G component of the m-th row, n-th column pixel, and “AM_B” denotes an expansion/compression parameter corresponding to a B component of the m-th row, n-th column pixel. “a” denotes a coefficient for adjusting the expansion/compression parameter.
AM_Rmn=α×(255/GV_Rmn) (expression 10)
AM_Gmn=α×(255/GV_Gmn) (expression 11)
AM_Bmn=α×(255/GV_Bmn) (expression 12)
In the present embodiment, the expansion/compression parameter is used as a coefficient (a second coefficient) to be multiplied to the gradation value of the linear image data in order to further increase the gradation value of the second processed image data. In addition, a reciprocal of the expansion/compression parameter (the second coefficient) is used as a coefficient (a first coefficient) to be multiplied to the gradation value of the linear image data in order to further reduce the gradation value of the first processed image data. Therefore, the first γ value γ1 and the reciprocal of the expansion/compression parameter may each be described as “a part of the first measure” and the second γ value γ2 and the expansion/compression parameter may each be described as “a part of the second measure”. When the display apparatus 20 does not include the γ setting unit 108, the first γ processing unit 110, the second γ processing unit 111, and the like, the reciprocal of the expansion/compression parameter may be described as “the first measure” and the expansion/compression parameter may be described as “the second measure”. According to the expressions 10 to 12, the lower the brightness (the gradation value) of input image data, the larger the expansion/compression parameter (the second measure) that is set individually for each pixel of the input image data. As a result, the lower the brightness of the input image data the smaller the first measure to be set.
Alternatively, without using the coefficient α, a degree of deviation of the gradation value (the gradation value of linear image data) from an upper limit may be determined (set) as the expansion/compression parameter. However, with such a method, a multiplication of the expansion/compression parameter may cause the gradation value to exceed and/or be limited by the upper limit (saturation). Therefore, preferably, the coefficient α is used and the coefficient α is adjusted so that the saturation is suppressed.
Moreover, a first coefficient corresponding to the first measure may be determined as the expansion/compression parameter. The first coefficient may differ from a reciprocal of a second coefficient corresponding to the second measure.
As shown in expressions 13 to 15 below, the expanding unit 202 multiplies each gradation value of the input image data (specifically, linear image data output from the inverse γ processing unit 109) by the expansion/compression parameter output from the expansion/compression parameter setting unit 201 (expansion process). As a result, expanded image data is generated. In addition, the expanding unit 202 outputs the expanded image data to the second γ processing unit 111. In expressions 13 to 15, “VA_Rmn” denotes an expanded R value (an R value of the expanded image data) of an m-th row, n-th column pixel. “VA_Gmn” denotes an expanded G value (a G value of the expanded image data) of the m-th row, n-th column pixel. In addition, “VA_Bmn” denotes an expanded B value (a B value of the expanded image data) of the m-th row, n-th column pixel. A calculation using the expressions 13 to 15 generates the expanded image data of which a pixel value is an RGB value constituted by an 8-bit R value, an 8-bit G value, and an 8-bit B value. Moreover, a data format of the expanded image data is not particularly limited.
VA_Rmn=GV_Rmn×AM_Rmn (expression 13)
VA_Gmn=GV_Gmn×AM_Gmn (expression 14)
VA_Bmn=GV_Bmn×AM_Bmn (expression 15)
As shown in expressions 16 to 18 below, the compressing unit 203 divides each gradation value of the input image data (specifically, linear image data output from the inverse γ processing unit 109) by the expansion/compression parameter output from the expansion/compression parameter setting unit 201 (compression process). As a result, compressed image data is generated. In addition, the compressing unit 203 outputs the compressed image data to the first γ processing unit 110. In expressions 16 to 18, “VB_Rmn” denotes a compressed R value (an R value of the compressed image data) of an m-th row, n-th column pixel. “VB_Gmn” denotes a compressed G value (a G value of the compressed image data) of the m-th row, n-th column pixel. In addition, “VB_Bmn” denotes a compressed B value (a B value of the compressed image data) of the m-th row, n-th column pixel. A calculation using the expressions 13 to 15 generates the compressed image data of which a pixel value is an RGB value constituted by an 8-bit R value, an 8-bit G value, and an 8-bit B value. Moreover, a data format of the compressed image data is not particularly limited. In addition, a process of dividing a gradation value by the expansion/compression parameter may be described a “process of multiplying the gradation value by a reciprocal of the expansion/compression parameter”.
VB_Rmn=GV_Rmn×AM_Rmn (expression 16)
VB_Gmn=GV_Gmn×AM_Gmn (expression 17)
VB_Bmn=GV_Bmn×AM_Bmn (expression 18)
The first γ processing unit 110 uses the compressed image data in place of the linear image data. Accordingly, the gradation value of the first processed image data becomes smaller than the gradation value according to the first embodiment and the transmittance of the first liquid crystal panel 106 becomes lower than the transmittance according to the first embodiment. In addition, the second γ processing unit 111 uses the expanded image data in place of the linear image data. Accordingly, the gradation value of the second processed image data becomes larger than the gradation value according to the first embodiment and the viewing angle characteristics of the second liquid crystal panel 107 become more inferior than the viewing angle characteristics according to the first embodiment. According to the above, a double image can be made less visible.
As described above, according to the present embodiment, the first measure and the second measure are set further based on input image data. Accordingly, a double image can be made less visible than in the first embodiment.
While an example in which the first measure and the second measure are individually set for each pixel value of input image data has been described, this is not restrictive. For example, the first measure and the second measure may be individually set for each of a plurality of divided regions constituting the screen. The divided region may be a region in which one pixel is displayed or a region in which two or more pixels are displayed. A resolution (the number of liquid crystal elements) of the first liquid crystal panel 106 may be equal to a resolution of the second liquid crystal panel 107 or may be lower than the resolution of the second liquid crystal panel 107. In this case, each liquid crystal element of the first liquid crystal panel 106 corresponds to two or more pixels. The plurality of divided regions may be a plurality of divided regions respectively corresponding to the plurality of liquid crystal elements of the first liquid crystal panel 106. Making the resolution of the first liquid crystal panel 106 lower than the resolution of the second liquid crystal panel 107 enables a production cost of the display apparatus to be reduced. The first measure and the second measure may be set with respect to an entire screen. In other words, a pair of the first measure and the second measure may be set.
A method of setting the first measure and the second measure with respect to a divided region or the entire screen is not particularly limited. For example, the lower a maximum brightness (a maximum gradation value) of the input image data, the smaller the first measure to be set, and the lower the maximum brightness of the input image data, the larger the second measure to be set. The maximum brightness of the input image data (linear image data) is a maximum brightness in the entire screen, a maximum brightness in a divided region, or the like. With a display apparatus that emphasizes image formation such as a television apparatus, a brightness of input image data sometimes need not be reproduced. In such a case, emphasis may be placed on reducing a double image and an average brightness (an average gradation value) of the input image data may be used in place of the maximum brightness of the input image data. The average brightness of the input image data (linear image data) is an average brightness over the entire screen, an average brightness over a divided region, or the like.
While an example in which the first measure and the second measure are set in accordance with a brightness of input image data has been described, this is not restrictive. The higher a spatial frequency of image data, the more visible a double image. Therefore, in accordance with the spatial frequency of the input image data, the higher the spatial frequency of the input image data, the smaller the first measure may be set, and the higher the spatial frequency of the input image data, the larger the second measure may be set. Specifically, with respect to each of a plurality of pairs of two adjacent pixels, a gradation difference (an absolute value of a difference in gradation values of the input image data (linear image data)) between the two pixels may be calculated and the coefficient α may be adjusted such that the larger a sum of a plurality of gradation differences, the larger the value of the coefficient α. Accordingly, the larger the sum of a plurality of gradation differences, the larger the expansion/compression parameter (second measure) to be set.
A third embodiment of the present invention will be described below. In the first embodiment, an example of setting the first γ value γ1 and the second γ value γ2 in accordance with a user operation has been described. In the present embodiment, an example of setting the first γ value γ and the second γ value γ2 in accordance with a liquid crystal panel temperature will be described. The liquid crystal panel temperature is a temperature (a parameter) related to a backlight unit-side liquid crystal panel (the first liquid crystal panel). Hereinafter, points (configurations and processes) that differ from those of the first embodiment will be described in detail and descriptions of points that are the same as those of the first embodiment will be omitted.
With progress toward higher dynamic ranges in liquid crystal display apparatuses, there is a growing demand for high-brightness display. In particular, since a backlight light source (a backlight unit) in a display apparatus using double liquid crystals requires high brightness, there is a problem in that liquid crystals on a side of the backlight light source (liquid crystals of the first liquid crystal panel) reach high temperatures and deteriorate and, consequently, attains higher transmittance than ordinary liquid crystals.
A level at which liquid crystals reach a high temperature may depend on the transmittance of the liquid crystal panel. In backlight light (light emitted from a backlight light source), light shielded by the liquid crystal panel is converted into heat on a surface and inside the liquid crystal panel. Therefore, for example, when a video signal (image data) is dark and the transmittance of the liquid crystal panel is low, a larger amount of the backlight light is shielded by the liquid crystal panel and the liquid crystal panel is more likely to reach a high temperature. Conversely, when the video signal is bright and the transmittance of the liquid crystal panel is high, since the amount of the backlight light shielded by the liquid crystal panel is small, the liquid crystal panel is less likely to reach a high temperature as compared to when the transmittance of the liquid crystal panel is low.
Therefore, in the present embodiment, a method of controlling a temperature rise of a backlight light source-side liquid crystal panel by controlling the first γ value γ1 and the second γ value γ2 will be described.
The temperature sensor detecting unit 302 detects a liquid crystal panel temperature related to the first liquid crystal panel 106 and outputs the detected liquid crystal panel temperature to the γ setting unit 108. The liquid crystal panel temperature may be a temperature of the first liquid crystal panel 106 itself or a temperature at another location (the second liquid crystal panel 107, the backlight unit 105, or the like) inside the display apparatus 30. The liquid crystal panel temperature may be an estimated temperature. An outside temperature of the display apparatus 30 or the like may be taken into consideration when estimating the temperature. The reference temperature storage unit 301 stores and retains a reference temperature to be used as a threshold when setting the first γ value and the second γ value. The γ setting unit 108 determines the first γ value γ1 and the second γ value γ2 in accordance with the reference temperature output from the reference temperature storage unit 301 and the liquid crystal panel temperature output from the temperature sensor detecting unit 302. Furthermore, the γ setting unit 108 outputs the first γ value γ1 to the first γ processing unit 110 and outputs the second γ value γ2 to the second γ processing unit 111.
As described above, according to the present embodiment, the first γ value γ1 and the second γ value γ2 are set based on the liquid crystal panel temperature. Accordingly, when the detected liquid crystal panel temperature is equal to or higher than the reference temperature, in accordance with an increase in the liquid crystal panel temperature, optical transmittance of the first liquid crystal panel 106 increases while the γ characteristics of the double liquid crystal panel constituted by the first liquid crystal panel 106 and the second liquid crystal panel 107 remains unchanged. As a result, since backlight light shielded by the first liquid crystal panel 106 decreases, backlight light converted into heat inside the first liquid crystal panel 106 decreases, and a temperature rise of the first liquid crystal panel 106 which is a primary cause of deterioration of the first liquid crystal panel 106 can be suppressed.
While an example of respectively changing the first γ value γ1 and the second γ value γ2 in accordance with a change in the liquid crystal panel temperature using a reference temperature as a threshold has been described, a method of setting the first γ value γ1 and the second γ value γ2 is not particularly limited. For example, the first γ value γ1 and the second γ value γ2 may be respectively changed in accordance with a change in the liquid crystal panel temperature without using the reference temperature as a threshold. In this case, the first γ value γ1 and the second γ value γ2 are respectively changed even when the liquid crystal panel temperature changes within a temperature range below the reference temperature. For example, the first γ value γ1 and the second γ value γ2 may be respectively changed in steps with respect to a continuous change in the liquid crystal panel temperature or the first γ value γ1 and the second γ value γ2 may be respectively continuously changed with respect to a continuous change in the liquid crystal panel temperature. The first γ value γ1 and the second γ value γ2 may be respectively changed when the liquid crystal panel temperature changes so as to straddle he reference temperature, and the first γ value γ1 and the second γ value γ2 may not be respectively changed when the liquid crystal panel temperature changes within a temperature range equal to or higher than the reference temperature.
A fourth embodiment of the present invention will be described below. In the third embodiment, an example of setting the first γ value γ1 and the second γ value γ2 in accordance with a liquid crystal panel temperature has been described. However, depending on input image data, controlling the first γ value γ1 and the second γ value γ2 in accordance with the liquid crystal panel temperature may cause a double image to become prominent. Therefore, in the present embodiment, an example of setting the first γ value γ1 and the second γ value γ2 in accordance with the liquid crystal panel temperature and the input image data will be described. Specifically, whether or not a double image is readily visible in the input image data is determined in advance from the input image data, and γ value control similar to that in the third embodiment is only performed in a state where a double image is not readily visible. Accordingly, a temperature rise of the liquid crystal panel can be suppressed while preventing a decline in a double image. Hereinafter, points (configurations and processes) that differ from those of the third embodiment will be described in detail and descriptions of points that are the same as those of the third embodiment will be omitted.
Based on the input image data (in accordance with the input image data) output from the image acquiring unit 103, the double image determining unit 401 determines whether or not a double image is readily visible when a person views the displayed input image data. In other words, based on the input image data, the double image determining unit 401 determines whether or not an image of which a double image is readily visible is displayed. In addition, the double image determining unit 401 outputs a determination result thereof (a double image determination result) to the γ setting unit 108. Specifically, the double image determining unit 401 performs a fast discrete Fourier transform (FFT) on the input image data and calculates spatial frequency characteristics. In this case, a maximum value among spatial frequencies in the input image data will be referred to as a maximum spatial frequency. The double image determining unit 401 determines that a double image is readily visible in the input image data and outputs 1 when the maximum spatial frequency is equal to or larger than a threshold, but otherwise outputs 0. In this case, it is assumed that the threshold can be arbitrarily set in accordance with a level of a double image to be suppressed. When the threshold is large, the double image determining unit 401 outputs 0 even in a state where a double image is relatively readily visible. When the threshold is small, the double image determining unit 401 outputs 0 only in a state where a double image is hardly visible.
The γ setting unit 108 determines the first γ value γ1 and the second γ value γ2 in accordance with the reference temperature output from the reference temperature storage unit 301, the double image determination result output from the double image determining unit 401, and the liquid crystal panel temperature output from the temperature sensor detecting unit 302. Furthermore, the γ setting unit 108 outputs the first γ value γ1 to the first γ processing unit 110 and outputs the second γ value γ2 to the second γ processing unit 111. Specifically, the γ setting unit 108 determines the first γ value γ1 and the second γ value γ2 using, for example, the table shown in
As described above, according to the present embodiment, the first γ value γ1 and the second γ value γ2 are set based on the liquid crystal panel temperature only in the case of input image data in which a double image is not readily visible. Accordingly, a temperature rise of the first liquid crystal panel 106 which is a primary cause of deterioration of the first liquid crystal panel 106 can be suppressed while preventing a double image from becoming more visible due to changes in the first γ value γ1 and the second γ value γ2.
While the use of a maximum spatial frequency has been described as a method used by the double image determining unit 401 in order to determine whether or not a double image is readily visible in the input image data, a determination method is not limited thereto. For example, a determination may be made using an average brightness in the screen.
Each functional unit according to the first, second, third, and fourth embodiments may or may not be individual hardware. Functions of two or more functional units may be realized by common hardware. Each of a plurality of functions of a single functional unit may be realized by individual hardware. Two or more functions of a single functional unit may be realized by common hardware. In addition, each functional unit may or may not be realized by hardware. For example, an apparatus may include a processor and a memory storing a control program. Furthermore, functions of at least a part of the functional units included in the apparatus may be realized by having the processor read the control program from the memory and execute the control program.
It should be noted that the first, second, third, and fourth embodiments are merely examples and that configurations obtained by appropriately modifying or altering the configurations of the first, second, third, and fourth embodiments without departing from the spirit and scope of the present invention are also included in the present invention. Configurations obtained by appropriately combining the configurations of the first, second, third, and fourth embodiments are also included in the present invention. For example, the expansion/compression parameter may be set in accordance with a user operation and the first γ value γ1 and the second γ value γ2 may be set in accordance with input image data.
Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2017-216158, filed on Nov. 9, 2017, and Japanese Patent Application No. 2018-080548, filed on Apr. 19, 2018, w ich are hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-216158 | Nov 2017 | JP | national |
| 2018-080548 | Apr 2018 | JP | national |
