JP5836717B2 - Image display device - Google Patents

Description

  The present invention relates to an image display device provided with a brightness adjustment function for a display image.

  In general, a liquid crystal display device is driven to be supplied to a light source (for example, a plurality of light emitting diodes (LEDs) or a cold cathode fluorescent lamp (CCFL)) of a backlight module disposed on the back side of the liquid crystal display panel according to a user operation. It has a function of increasing or decreasing the display brightness of an image on the liquid crystal display panel by increasing or decreasing the power.

  However, if the ambient light of the liquid crystal display device (for example, external light entering a room through a window or illumination light from a room lighting device) increases, the viewer (human) may experience a decrease in the brightness of the displayed image. On the other hand, when the ambient light decreases, the viewer feels that the brightness of the display image has increased too much (and thus consumes more power than necessary). There was a problem.

  As a solution to such a problem, there has been proposed an image display device that measures the illuminance of ambient light and automatically adjusts the luminance of the display image according to the measurement result (see, for example, Patent Documents 1 to 4). ).

Japanese Patent Laid-Open No. 9-146073 JP 2006-72255 A JP 2007-310096 A JP 2010-181763 A

  However, since the image display devices disclosed in Patent Documents 1 to 3 do not include an illuminance sensor on the back side, there is a window on the back side of the image display device, and external light directed to the viewer from the back side. When the brightness is high, there is a problem that the brightness of the display image cannot be adjusted appropriately.

  Further, the image display device disclosed in Patent Document 4 includes an illuminance sensor on both the front side (front side) and the back side (back side), but a number of reference tables are prepared in advance. There is a problem that a large amount of memory is required because it must be stored in the memory.

  Accordingly, the present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide an image display device that can appropriately adjust the brightness of a display image without requiring a large-capacity memory. Is to provide.

であり、前記係数ｋは、−０．１以上０．２以下の範囲内の値に設定され、前記係数Ｃ _１ は、０．０以上０．１以下の範囲内の値に設定され、前記係数Ｃ _２ は、０．９以上１．０以下の範囲内の値に設定されることを特徴としている。
An image display device according to an aspect of the present invention includes an image display unit including an image display surface provided on a front surface of a housing, and a display control unit that displays an image based on image data on the image display surface, A first illuminance measurement unit that measures a first ambient light incident illuminance that is an incident illuminance of first ambient light traveling from the front side of the housing toward a reference plane including the image display surface; A second illuminance measurement unit that measures a second ambient light incident illuminance that is an incident illuminance of second ambient light that travels toward the reference plane from the back side that is the surface opposite to the front surface of the body; A first calculation formula for calculating a third ambient light incident illuminance at a predetermined position on the front side of the image display surface from the first ambient light incident illuminance and the second ambient light incident illuminance in advance. The first ambient light incident illuminance, and the second ambient light incident illumination. , And an incident illuminance calculation unit that calculates the third ambient light incident illuminance using the first calculation formula, and the display control unit is configured to calculate the third periphery calculated by the incident illuminance calculation unit. A suitable display brightness of an image to be displayed on the image display surface is determined from the light incident illuminance and the display brightness indicated by the image data, and an image is displayed on the image display surface with the suitable display brightness. The calculation formula indicates the first ambient light incident illuminance as I _FRO , the second ambient light incident illuminance as I _REA , the third ambient light incident illuminance as I _EYE , and a predetermined value When the coefficients of k are represented by k, C ₁ and C ₂ ,

Der is, the coefficient k is set to a value in the range of -0.1 to 0.2, the coefficient _{C 1} is set to a value in the range of 0.0 to 0.1, It said coefficients C ₂ is characterized that it is set to a value in the range of 0.9 to 1.0.

  According to the image display device according to an aspect of the present invention, an effect that the luminance of the display image can be appropriately adjusted without requiring a large-capacity memory can be obtained.

It is a figure which shows roughly an example of the left side surface of the liquid crystal display device as the image display device according to Embodiment 1 of the present invention and the surrounding environment. 6 is a diagram illustrating an example of a path of ambient light that is incident on a position (predetermined position) that is assumed to be a position of an eye of a viewer of the liquid crystal display device according to Embodiment 1. FIG. It is a figure which shows an example (photographing when the outside of a window is bright) of the installation environment of the liquid crystal display device which concerns on Embodiment 1. FIG. It is a figure which shows an example (photographing when the outside of a window is a little bright) of the installation environment of the liquid crystal display device which concerns on Embodiment 1. FIG. It is a figure which shows an example (photographing when the outside of a window is dark) of the installation environment of the liquid crystal display device which concerns on Embodiment 1. FIG. 1 is a block diagram schematically showing an example of a configuration of a liquid crystal display device according to Embodiment 1. FIG. It is a block diagram which shows roughly an example of a structure of the display control part shown by FIG. FIG. 7 is a diagram schematically showing a system configuration for calculating an incident illuminance coefficient used in an incident illuminance calculation unit shown in FIG. 6. The figure which shows the time change of the incident illumination intensity in each position (The position of a viewer's eye, the front surface of a liquid crystal display device, a back surface, an upper surface, a left surface, and a right surface) in case there is a window on the back side of the liquid crystal display device It is. It is a figure which shows the relationship between the predicted value of the incident illumination intensity in the position of an eye, and the measured value of the incident illumination intensity in the position of an eye. It is a table | surface which shows the relationship between the visual field brightness | luminance of a viewer, and the incident illumination intensity to eyes. It is a figure which shows the relationship between the measured value by a front surface illumination intensity sensor, and the incident illumination intensity in the position of an eye in a 1st comparative example. It is a figure which shows the relationship between the measured value by a back surface illumination intensity sensor, and the incident illumination intensity in the position of an eye in the 2nd comparative example. It is a block diagram which shows roughly an example of a structure of the display control part of the liquid crystal display device which concerns on Embodiment 2 of this invention.

Embodiment 1 FIG.
FIG. 1 is a diagram schematically showing an example of a left side surface 11c and a surrounding environment of a liquid crystal display device 10 as an image display device according to Embodiment 1 of the present invention. In the example of FIG. 1, the liquid crystal display device 10 is installed indoors such that the back surface (back surface) 11 b of the housing 11 faces the window 21 and the front surface (front surface) 11 a of the housing 11 faces the center of the room. Has been. In the example of FIG. 1, the lighting fixture 22 is installed on the ceiling of the room. From the window 21, external light Fa such as light from the sun enters the room toward the back surface 11 b of the liquid crystal display device 10 or through the reference plane 12 including the display surface of the liquid crystal display panel 5. Illumination light Fb is emitted from the lighting fixture 22. In the eyes of the viewer (human) in the room, not only the image from the liquid crystal display panel 5 that is the image display surface of the liquid crystal display device 10, but also a part of the external light Fa and a part of the illumination light Fb. Is incident. Here, the light existing in the surrounding environment of the liquid crystal display device 10 such as the external light Fa and the illumination light Fb is referred to as “ambient light”. The installation environment of the liquid crystal display device 10 (for example, the size, number, position, direction, etc. of the windows, and the number, position, type, etc. of lighting fixtures) and the shape of the liquid crystal display device 10 are the same as in the example of FIG. It is not limited.

  FIG. 2 is a diagram illustrating an example of a path of ambient light that enters the eye position of the viewer 23 of the liquid crystal display device 10 according to the first embodiment. As shown in FIG. 2, the external light Fa that has entered from the window 21 travels toward the back surface 11 b of the liquid crystal display device 10 and its periphery. Part of the external light Fa is, for example, the ambient light Fa2 that passes outside the left side surface 11c of the liquid crystal display device 10, the ambient light Fa3 that passes outside the right side surface 11d of the liquid crystal display device 10, and the liquid crystal display device 10. The light enters the eyes of the viewer 23 as ambient light Fa1 passing above the upper surface 11e. Further, a part of the illumination light Fb comes from, for example, the ambient light Fb1 reflected by the liquid crystal display panel 5 that is the image display surface of the liquid crystal display device 10, the ambient light Fb2 reflected by the floor or the wall, and the lighting fixture 22. It enters the eyes of the viewer 23 as the ambient light Fb3. Note that the path and type of the ambient light incident on the eyes of the viewer 23 are not limited to the illustrated example.

As shown in FIGS. 3 and 4, when the ambient light of the liquid crystal display device 10 (for example, the external light Fa entering the room through the window 21 or the illumination light Fb from the lighting fixture 22) increases, Ambient light incident on the eyes also increases, and as a result, the viewer 23 can easily feel that the brightness of the display image is too low (thus lowering the visibility). Conversely, as shown in FIG. 5, when the ambient light decreases, the ambient light incident on the eyes of the viewer 23 decreases, and the viewer 23 feels that the brightness of the display image has increased too much. Easy (and therefore consumes more power than necessary). The liquid crystal display device 10 according to the first embodiment has a function of adjusting luminance of the image displayed on the liquid crystal display panel 5, a predetermined distance D _P from the liquid crystal display panel 5 _(e.g., 2 [m]) apart When an image displayed on the liquid crystal display panel 5 is viewed from the position, the image is automatically adjusted so that an image of optimum quality can be viewed.

In the first embodiment, the liquid crystal display device 10 includes at least two illuminance measurement units (for example, the front illuminance sensor 1 that is the first illuminance measurement unit and the back illuminance sensor that is the second illuminance measurement unit in FIG. 1). with 2) at least two intensity measurements, using a first equation described below, is assumed from the liquid crystal display panel 5 with a predetermined distance D _P apart a predetermined position (observer eye position When the image displayed on the liquid crystal display panel 5 is viewed from 13), the brightness of the display image is automatically adjusted so that an image of optimum quality can be viewed.

  FIG. 6 is a block diagram schematically showing an example of the configuration of the liquid crystal display device 10 according to the first embodiment. As shown in FIGS. 1, 2, and 6, the liquid crystal display device 10 includes an image display unit 7, a front illuminance sensor 1 as a first illuminance measurement unit, and a back illuminance as a second illuminance measurement unit. A sensor 2 and an incident illuminance calculation unit 3 are provided. However, the configuration of the liquid crystal display device 10 is not limited to the example of FIG. For example, the present invention can be applied to an image display device other than a liquid crystal display device as long as the image display device has a brightness adjustment function.

  The image display unit 7 causes the liquid crystal display panel 5 as an image display surface provided on the front surface 11 a of the housing 11, the backlight module 6, and an image based on input image data to be displayed on the liquid crystal display panel 5, And a display control unit 4 for driving the backlight module 6.

The front illuminance sensor 1 is a first ambient light (for example, as shown in FIG. 1) that travels from the front surface 11a side (a position away from the front surface 11a) of the housing 11 toward the reference plane 12 including the display surface of the liquid crystal display panel 5. Fb, the first ambient light incident illuminance _IFRO that is the incident illuminance of Fb1) in FIG. 2 is measured. The back surface illuminance sensor 2 is a second ambient light (for example, shown in FIG. 1) that travels toward the reference plane 12 from the back surface 11b side (a position away from the back surface 11b) that is the surface opposite to the front surface 11a of the housing 11. The second ambient light incident illuminance _IREA , which is the incident illuminance of Fa), is measured. In the first embodiment, the front illuminance sensor 1 as the first illuminance measurement unit is provided on the front surface 11a of the housing 11 with the light receiving surface facing forward, and the rear illuminance sensor as the second illuminance measurement unit. 2 is provided on the back surface 11b of the housing 11 with the light receiving surface facing rearward. However, the attachment position of the first illuminance measurement unit and the second illuminance measurement unit may be outside the housing 11. The first illuminance measurement unit is configured to detect the incident illuminance of the first ambient light Fb1 that travels from the front surface 11a side (position away from the front surface 11a) of the housing 11 toward the reference plane 12 including the display surface of the liquid crystal display panel 5. As long as the measuring instrument can measure the first ambient light incident illuminance I _FRO , other structures and other positions may be used. In addition, the second illuminance measurement unit receives the second ambient light incident that is the incident illuminance of the second ambient light traveling toward the reference plane 12 from the back surface 11b side (position away from the back surface 11b) of the housing 11. Other structures and other positions may be used as long as the measuring instrument can measure the illuminance _IREA .

The incident illuminance calculation unit 3 calculates a third ambient light incident illuminance I _{EYE at} a predetermined position 13 on the front surface 11a side of the liquid crystal display panel 5 from the first ambient light incident illuminance I _FRO and the second ambient light incident illuminance I _REA. The first calculation formula for calculating the first ambient light incident illuminance I _FRO , the second ambient light incident illuminance I _REA , and the first calculation formula to be described later is used. The ambient light incident illuminance I _EYE is calculated.

The display control unit 4 uses the third ambient light incident illuminance I _EYE calculated by the incident illuminance calculation unit 3 and the display luminance L _DIS indicated by the input image data to display a suitable display luminance L of the image to be displayed on the liquid crystal display panel 5. By determining the _PRE and adjusting the power supplied to the light source in the backlight module 6, an image is displayed on the liquid crystal display panel 5 with a suitable display brightness L _PRE .

In order to calculate the third ambient light incident illuminance I _EYE using the first ambient light incident illuminance I _FRO , the second ambient light incident illuminance I _REA , and predetermined coefficients k, C ₁ , C ₂ , As a calculation formula of 1, for example, the following formula (1) is used.

The first calculation formula (formula (1)) uses the variable logI _EYE as the objective variable, the variable (I _REA / I _FRO ), the variable (I _FRO / I _REA ), and the variable log (I _REA + I _FRO ). Each is an explanatory variable, and is a multiple regression equation derived using a variable increase / decrease method. For the obtained multiple regression equation, the multiple regression equation having the highest correlation with the significance by the “t test” is used. Adjusted for the number of explanatory variables, the degree of freedom adjusted R ² value (that is, the explanation rate) is 0.84, and it can be predicted with 84% reliability including the environment that is difficult to predict even though it was measured this time. . R represents a multiple correlation coefficient.

In the first embodiment, the coefficient k is set to a value in the range of −0.1 to 0.2, and the coefficient C ₁ is set to a value in the range of 0.0 to 0.1. , the coefficient _{C 2} is set to a value in the range of 0.9 to 1.0.

More preferably, the coefficient k is set to a value in the range of −0.004 to 0.132, the coefficient C ₁ is set to a value in the range of 0.016 to 0.024, and the coefficient C ₂ is set to a value within the range of 0.911 to 0.963.

As a preferable example, C ₁ = 0.020, C ₂ = 0.937, and k = 0.064 can be set.

  FIG. 7 is a block diagram schematically showing an example of the configuration of the display control unit 4 shown in FIG. As shown in FIG. 7, the display control unit 4 includes a display panel control unit 401 and a display panel drive unit 402. The display panel control unit 401 controls the display panel drive unit 402 based on the input image data, and the display panel drive unit 402 drives the liquid crystal display panel 5 to display an image based on the image data.

  The display control unit 4 further includes an average input luminance calculation unit 411, an average display luminance calculation unit 412, a display luminance calculation unit 413 that holds the second calculation formula, a backlight control unit 414, and a backlight driving unit. 415 and a coefficient input unit 416 which is an input unit of the coefficient p included in the second calculation formula.

Average input brightness calculating section 411, the average input brightness level from the image data (Average Picture Level _(APL)) to calculate the _{L IN.}

The average display brightness calculating unit 412, based on the average input brightness level _{L IN} obtained from the average input luminance calculating section 411, the average display brightness of the screen display (Average Luminance Level _(ALL)) to calculate the _{L DIS.}

In determining the preferred display brightness by the display control unit 4, a preferred display brightness, indicated at L _PRE, a third peripheral light incident illuminance, indicated by I _EYE, the average value of the display luminance indicated by the input image data In order to calculate a suitable display brightness L _PRE when a certain average display brightness is indicated by L _DIS and a predetermined coefficient is indicated by C ₃ , C ₄ , p, Equation (2) is used.

In the first embodiment, the coefficient C ₃ is set to a value in the range of 0.2 to 0.4, and the coefficient C ₄ is set to a value in the range of 0.1 to 0.3. The coefficient p is set to a value within the range of 1.5 to 1.8.

More preferably, the coefficient C ₃ is set to a value within the range of 0.296 to 0.348, the coefficient C ₄ is set to a value within the range of 0.15 to 0.218, and the coefficient p Is set to a value within the range of 1.52 to 1.676.

As a preferred example, when the age of the viewer is not taken into consideration, C ₃ = 0.322, C ₄ = 0.184, and p = 1.593 can be set. When the viewer is an elderly person or the like, about p = 1.8 may be used instead of p = 1.582.

Equation (2), C ₃ = 0.322, and C ₄ = 0.184 were performed as 22 subjects (performed with 25 subjects, 3 of the 25 were consistent in relation to experimental conditions It is a formula derived from an evaluation experiment by young people (excluded from aggregation because no trend was seen). Data were acquired by displaying 18 types of images with different average display brightness (ALL) on a 24-inch monitor, increasing the brightness from the lowest value, and presenting the subject with a preferable brightness. The field brightness is 3 conditions (10 [cd / m ² ], 50 [cd / m ² ], 250 [cd / m ² ]), and a total of 54 conditions (18 types × 3 conditions = 54 conditions) for each subject. Evaluation was made. The multiple regression analysis was performed by setting the incident illuminance to the eye as I _EYE and the average display luminance (ALL) of the display image as L _DIS [%], and the formula (2) was derived. The table in FIG. 8 is calculated based on the formula (2). In the horizontal direction of the table, the average display luminance (ALL) is 20%, 25%, 50%, 80%, 100%. In the vertical direction of the table, values in the case of 30 [lx], 100 [lx],..., 30000 [lx] are described as the illuminance incident on the eyes. The following formula (3) is a specific example of the formula (2).

The meaning of each term in equation (3) will be described.
The first term on the right side (0.322 × logI _EYE ) is a term determined by factors relating to the surrounding environment of the liquid crystal display device 10.
The second term (0.184 × logL _DIS ) on the right side is a term determined by factors relating to the content displayed by the video data.
The third term “p” on the right side is a term determined by factors due to individual differences of viewers (viewers).
L _{PRE on the} left side is a term relating to the illuminance (environment) incident on the eyes of the viewer (viewer).
In FIG. 5, 20%, 25%, 50%, 80%, and 100% are average display luminances (ALL) of the display image, and are values that vary depending on the brightness of the content. Therefore, the coefficient p is set as a user-adjustable coefficient. In particular, in the case of elderly people, it is often necessary to adjust the coefficient p according to individual characteristics.

FIG. 9 is a diagram schematically showing a system configuration for calculating the incident illuminance coefficient k used in the incident illuminance calculation unit 3 shown in FIG. The incident illuminance coefficient calculation unit 8 includes a measured value I _FRO of the front illuminance sensor 1, a measured value I _REA of the rear illuminance sensor 2, and an illuminance sensor placed at a predetermined position 13 assumed to be the position of the eyes of the viewer. The coefficient k in the first calculation formula is derived based on the measured value of the photodetector 8a.

  FIG. 10 shows the incident illuminance (A1) at the position assumed to be the eye position of the viewer in an environment where ambient light exists, as shown in FIGS. ) Incident illuminance (A2) to 11a, incident illuminance (A3) to the back surface (back) 11b of the liquid crystal display device, incident illuminance (A4) to the upper surface (top) 11e of the liquid crystal display device, left side surface of the liquid crystal display device It is an example of the data which actually measured the incident illuminance (A5) to the (left) 11c and the incident illuminance (A6) to the right side surface (right) 11d of the liquid crystal display device. The measurement was performed at 20 minute intervals for 24 hours at each location. In addition, the value at night without lighting is not shown in FIG. 10, and is not used for deriving the first calculation formula. Although FIG. 10 shows data for 24 hours, it is desirable to acquire such data in any state of clear, cloudy, and rainy. In FIG. 10, the horizontal axis represents time, and the vertical axis represents incident illuminance on each sensor. The position of the eyes of the viewer, the surface of the liquid crystal display panel 5, and the incident illuminance on the back of the liquid crystal display device at each time. Is expressed in time series. Note that the data A4, A5, and A6 in the graph of FIG. 10 are reference data that are not used for deriving the coefficient k, but these data can also be used for deriving the coefficient k.

As in FIG. 10, data for 22 locations, such as outdoor walls, semi-outdoors facing the outdoors, and indoor windows, are measured every 20 minutes for 24 hours. When the regression analysis is performed, the relationship between the incident illuminance I _EYE at the predetermined position 13 assumed to be the position of the eye of the viewer, the incident illuminance I _{FRO at} the front surface of the liquid crystal display device, and the incident illuminance I _REA at the rear surface of the liquid crystal display device. The above formula (1) was obtained as a relational expression indicating:

In actual measurement, illuminance sensors having the same characteristics are used on both the front surface 11a side and the back surface 11b side of the housing 11. Coefficients C ₁ and the coefficient C _2, in order to change the sensitivity of the illumination sensor, when the characteristic of the illuminance sensor is different on the side and rear 11b of the front 11a also changes the coefficient of the equation. For example, if there is a sensitivity difference between the incident illuminance I _REA on the back surface 11b of the liquid crystal display device 10 and the incident illuminance I _{FRO on} the front surface 11a of the liquid crystal display device 10, the sensitivity difference is expressed as (I _REA / I _FRO ), (I _FRO + I _REA ) and adjusting the coefficient C ₁ and the coefficient C ₂ is desirable.

In calculating the incident illuminance I _EYE at a predetermined position assumed to be the position of the eye of the viewer, the above formula (1) is used. The value of the coefficient k obtained from the results at 22 locations was 0.064. That is, it is desirable to use 0.064 as the coefficient k. Thereby, it is not necessary to acquire a lot of data for predicting the illuminance, and it is not necessary to have many tables on the memory.

  Further, this coefficient k may be adjusted to accurately match the installation environment. For example, the incident illuminance coefficient calculating unit 21 uses the value of the incident illuminance input unit for inputting the value measured by an external measuring instrument such as an illuminometer, and the measured values of the front illuminance sensor 1 and the rear illuminance sensor 2. The coefficient k is obtained from the equation (1). The coefficient k is measured a plurality of times and obtained from the average value. In adjusting the coefficient k, the coefficient k may be obtained by calculation other than the average value. For example, a median value may be used instead of the average value.

  Conventionally, brightness setting tables are created from many illuminance measurement values and many tables are stored in the memory. In this method, it is necessary to take several environments. According to the apparatus, the coefficient k can be acquired by performing measurement a plurality of times at an arbitrary time.

FIG. 11 is a diagram illustrating the relationship between the predicted value [lx] of the incident illuminance at the eye position (predetermined position 13) and the actual measured value [lx] of the incident illuminance at the eye position. In FIG. 11, the horizontal axis represents the predicted value, and the vertical axis represents the incident illuminance I _EYE (actually measured value) at the predetermined position 13 assumed to be the eye position. By using this relational expression, it is possible to predict the incident illuminance I _EYE at a predetermined position assumed to be the eye position with an accuracy of about 84%. As shown in FIGS. 12 and 13, when only the front illuminance sensor is used and when only the back illuminance sensor is used, as shown in the circled regions in each figure, the nonlinearity is obtained. Although the portion exists, in the case of the first embodiment, there is no nonlinear portion as shown in FIG.

  The incident illuminance input to the incident illuminance coefficient calculation unit 8 may be directly input from the photodetector 8a by direct connection to the output end of the photodetector (illuminance sensor) 8a, or instead of being input directly, wirelessly. You may input into the incident illumination intensity count calculation part 8 using communication etc. In addition, a value measured by an external illuminometer may be directly input using an input device such as a remote controller. Thereby, the coefficient k is calculated and can be used for the coefficient k of the expression (1) which is the first calculation formula of the incident illuminance calculation unit 3.

  As shown in FIG. 1, at least one front illuminance sensor 1 is installed on the image display surface side (front side) of the liquid crystal display device. Further, as shown in FIG. 1, at least one back surface illuminance sensor 2 is installed on the opposite side (back side) of the image display surface side (front side) of the liquid crystal display device. In the first embodiment, an example in which one front illuminance sensor 1 is installed on the front side of the liquid crystal display device and one back illuminance sensor 2 is installed on the back side of the image display surface of the liquid crystal display device will be described.

  When a plurality of front surface illuminance sensors 1 are installed on the front surface 11a side of the liquid crystal display device 10, for example, an average value of a plurality of detected values by the plurality of front surface illuminance sensors 1 is an illuminance on the front side of the liquid crystal display device. Used as However, other values such as an intermediate value between a maximum value and a minimum value of a plurality of detection values by the plurality of front surface illuminance sensors 1 may be used as the illuminance on the front side of the liquid crystal display device.

  When a plurality of back surface illuminance sensors 2 are installed on the back side of the liquid crystal display device, for example, an average value of a plurality of detected values by the plurality of back surface illuminance sensors 2 is used as a representative value of the illuminance on the back side of the liquid crystal display device. Used. However, other values such as an intermediate value between a maximum value and a minimum value of a plurality of detection values by a plurality of back surface illuminance sensors 2 may be used as a representative value of the illuminance on the back side of the liquid crystal display device.

  Moreover, when calculating the representative value of the illuminance on the back side of the liquid crystal display device, for example, a method of obtaining the representative value by calculating the average or median of a plurality of illuminance sensors may be taken. When calculating the representative value, a coefficient may be prepared for each illuminance sensor according to the position installed in the liquid crystal display panel, and the representative value may be calculated with weighting.

The back surface illuminance sensor 2 installed on the back side of the liquid crystal display device has a window on the back side of the liquid crystal display device, but is covered by a shield such as a wall partially provided with the back surface illuminance sensor 2. Is also possible. In order to acquire the ambient light more accurately, the back surface illuminance sensor 2 is desirably provided in a place not affected by the shielding object. When the back surface illuminance sensor 2 is installed on the wall surface, It is desirable to leave a gap of, for example, about 10 cm between them. In the special case where the liquid crystal display device is installed embedded in a wall surface or the like, the above-described gap cannot be formed. As a result, the back surface illuminance sensor 2 is completely obstructed by the wall surface or the like, and the incident ambient light becomes 0 (or an infinitely small value), so that the value of the incident illuminance _IREA is set as a fixed value 0. Can be substituted.

Thus, when the value of the incident illuminance _IREA does not change, a fixed value may be set and used instead of the value of the incident illuminance _IREA obtained by the back surface illuminance sensor 2. In that case, the essence of the present invention is not lost even when the liquid crystal display device is not provided with the back surface illuminance sensor 2, but when the value is set to a fixed value in advance, a sufficient effect can be obtained except in a limited installation environment. Therefore, it is desirable that the back surface illuminance sensor 2 includes the back surface illuminance sensor 2 even when the value of the incident illuminance _IREA does not change.

In the first embodiment, the front illuminance sensor 1 is disposed on the display surface side of the liquid crystal display device, and the back illuminance sensor 2 is disposed on the opposite side of the image display surface of the liquid crystal display device. This is because these positions are suitable for calculating the incident illuminance I _EYE at a predetermined position assumed to be the position of the eyes of the viewer described later.

In the display luminance calculation unit 413, an incident illuminance calculation unit is calculated from the incident illuminance _IFRO on the front surface of the liquid crystal display device of the front illuminance sensor 1 and the incident illuminance _IREA on the rear surface of the liquid crystal display device of the rear illuminance sensor 2 by Equation (1). 3 using the incident illuminance I _EYE at a predetermined position assumed to be the eye position obtained in 3, the average display brightness L _DIS obtained from the average display brightness calculation unit 412, and the coefficient p adjusted by the user. The display brightness L _PRE is calculated and output to the backlight control unit 414.

By mounting this formula, the display average input brightness level L _IN of the incident illuminance I _EYE image at a predetermined position that is assumed positions of the eyes, easily adjusted to a suitable display luminance L _PRE in small coefficient be able to.

  The coefficient input unit 416 is an input unit that inputs the value of the coefficient p of the second calculation formula (formula (2)). When the value of the coefficient p is increased, the display luminance becomes higher than the input illuminance value to the eyes, and therefore it is preferable to use it for setting when an elderly person looks at the liquid crystal display device. Although p was able to obtain high correlation with 1.592 from evaluation result, about 1.8 is good for general people, such as an elderly person.

The average display brightness L _DIS is determined from the average input brightness level L _IN image obtained at an average input brightness calculating unit 411, for example, for the liquid crystal display device gamma value γ is 2.2, the average input The luminance level _LIN is a value raised to the power of 2.2.
L _DIS = L _IN ^γ

The coefficient input unit 416 inputs a gamma value γ used by the average display luminance calculation unit 412 to obtain the average display luminance L _DIS . The gamma value γ varies depending on the light emission characteristics of the display, but usually γ = 2.2 or γ = 1.9 or γ = 2.5 is used.

According to the liquid crystal display device 10 according to the first embodiment, the first calculation formula for predicting the incident illuminance I _EYE at the predetermined position 13 that is assumed to be the position of the eye is mounted, so that a large-capacity memory is not provided. Even an apparatus can perform image quality settings adapted to the brightness environment of the surrounding environment. For this reason, it is possible to easily set display brightness suitable for the eyes of the viewer.

  Further, by making the coefficient p variable, it is possible to reflect the user's preferred brightness.

Embodiment 2. FIG.
FIG. 14 is a block diagram schematically showing an example of the configuration of the display control unit 41 of the liquid crystal display device as the image display device according to the second embodiment of the present invention. In FIG. 14, the same reference numerals are given to the same or corresponding components as those shown in FIG. As illustrated in FIG. 14, the display control unit 41 generates a surface reflection calculation unit 421 that calculates reflected light from the surface of the liquid crystal display panel 5, and an adjustment value for the black level of the display image according to the surface reflection amount. A black level calculation unit 422 and a saturation calculation unit 423 that generates an adjustment value of the saturation of the display image according to the surface reflection amount. The display panel control unit 401 adjusts the luminance in the same manner as the liquid crystal display device according to the first embodiment. In addition, the display panel control unit 401 adjusts the black level and the saturation of the display image.

  A value of the surface reflectance Q of the liquid crystal display panel 5 is input to the surface reflection calculation unit 421 from an input unit (not shown). As the input value, a value such as a specification describing the characteristics of the liquid crystal display panel is used, or the surface reflectance Q is measured and input by an existing method.

The surface reflection calculation unit 421 measures the light irradiated on the surface of the screen from the incident illuminance _IFRO output from the front surface illuminance sensor 1 on the front surface of the liquid crystal display device, and calculates the reflection luminance _LREF . The calculated reflection luminance L _REF is output to the black level calculation unit 422. The reflection luminance L _REF can be obtained by the following equation (4) using the surface reflectance Q obtained from the input unit, for example.
L _REF = I _FRO × Q / π Formula (4)

The black level calculation unit 422 gives a signal for adjusting the black level of the display image to the display panel control unit 401 based on the reflection luminance L _REF calculated by the surface reflection calculation unit 421. In an example of a method for adjusting the black level based on the reflection luminance L _REF , for example, in a bright environment, when the reflection luminance L _{REF on} the surface of the liquid crystal display panel is 10 [cd / m ² ], Since the reflected light is stronger than the environment, adjustment is made to increase the black level in order to make it easier to visually recognize bright portions in the display image. By such adjustment, the image quality is suitable for the reflection characteristics of the display surface of the liquid crystal display panel 5, and it is possible to suppress a decrease in visibility due to light reflection.

The saturation calculation unit 423 adjusts the color intensity based on the reflection luminance L _REF obtained by the surface reflection calculation unit 421 using Expression (4). In an example of a method for adjusting the saturation based on the reflection luminance L _REF , for example, when the reflection luminance is increased, adjustment is performed to increase the saturation. By such adjustment, the image quality (the color becomes darker) suitable for the reflection characteristics of the display surface of the liquid crystal display panel 5 can be obtained, and a decrease in the visibility of the color due to the reflection of light can be suppressed. It becomes easy.

  Although it is desirable to perform image quality correction by the black level calculation unit 422 and the saturation calculation unit 423 in order to suppress a reduction in visibility, a configuration in which only luminance control is performed by the backlight control unit 414 and image quality correction is not performed (implementation) The configuration of the first embodiment) may be adopted.

  Alternatively, only one of the image quality correction of black level correction or saturation correction may be performed.

According to the liquid crystal display device according to the second embodiment, in order to perform the image quality setting adapted to the brightness environment by installing the calculation formula for predicting the incident illuminance I _EYE at a predetermined position assumed to be the eye position. Therefore, it is possible to easily set the display brightness suitable for the eyes of the viewer by omitting the conventionally required measurement.

Modified example.
The image quality adjustment described in the first and second embodiments can be applied not only to a display device using a backlight module but also to all image display devices capable of adjusting the brightness.

  DESCRIPTION OF SYMBOLS 1 Front illuminance sensor (1st illuminance measurement part), 2 Back illuminance sensor (2nd illuminance measurement part), 3 Incident illuminance calculation part, 4 Display control part, 5 Liquid crystal display panel, 6 Backlight module, 7 Image display Unit, 8 incident illuminance coefficient calculation unit, 8a photodetector (illuminance measuring device), 10 liquid crystal display device (image display device), 11 housing, 11a front surface, 11b back surface, 11c left side surface, 11d right side surface, 11e top surface, 11f lower surface, 12 reference plane, 13 predetermined position (position assumed to be the position of the eye of the viewer), 21 window, 22 lighting fixture, 23 viewer (human), 401 display panel control unit, 402 display panel drive 411 average input luminance calculation unit, 412 average display luminance calculation unit, 413 display luminance calculation unit, 414 backlight control unit, 4 15 backlight drive unit, 416 coefficient p input unit, 421 surface reflection calculation unit, 422 black level calculation unit, 423 saturation calculation unit, Fa, Fa1 to Fa3 external light (ambient light), Fb, Fb1 to Fb3 illumination light ( Ambient light).

Claims (11)

An image display unit including an image display surface provided on the front surface of the housing; and a display control unit configured to display an image based on image data on the image display surface;
A first illuminance measurement unit that measures a first ambient light incident illuminance that is an incident illuminance of first ambient light that travels from the front side of the housing toward a reference plane that includes the image display surface;
A second illuminance measurement unit that measures a second ambient light incident illuminance that is an incident illuminance of second ambient light that travels from the back side, which is the surface opposite to the front surface of the housing, toward the reference plane. When,
A first calculation formula for calculating a third ambient light incident illuminance at a predetermined position on the front side of the image display surface from the first ambient light incident illuminance and the second ambient light incident illuminance in advance. An incident illuminance calculation unit that holds the first ambient light incident illuminance, the second ambient light incident illuminance, and calculates the third ambient light incident illuminance using the first calculation formula; Prepared,
The display control unit determines a suitable display luminance of an image to be displayed on the image display surface from the third ambient light incident illuminance calculated by the incident illuminance calculation unit and the display luminance indicated by the image data, Displaying an image at the preferred display brightness on the image display surface;
The first calculation formula is:
The first ambient light incident illuminance is denoted by I _FRO ,
The second ambient light incident illuminance is indicated by _IREA ,
The third ambient light incident illuminance is indicated by I _EYE
When the predetermined coefficients are indicated by k, C ₁ and C ₂ ,

Der is,
The coefficient k is set to a value within a range of −0.1 or more and 0.2 or less,
The coefficient _{C 1} is set to a value in the range of 0.0 to 0.1,
The coefficient C _2, the image display device characterized in that it is set to a value in the range of 0.9 to 1.0. The first calculation formula is:
Let the variable logI _EYE be the objective variable,
Variable I _REA / I _FRO and variable (I _FRO / I _REA ),
And each of the variables log (I _REA + I _FRO ) are explanatory variables,
The image display device according to claim 1, wherein the image display device is a multiple regression equation derived using a variable increase / decrease method. The coefficient k is set to a value within a range of −0.004 to 0.132.
The coefficient _{C 1} is set to a value in the range of 0.016 or more 0.024 or less,
The coefficient _{C 2,} the image display apparatus according to claim 1 or 2, characterized in that it is set to a value in the range of 0.911 or more 0.963 or less. The determination of the suitable display brightness by the display control unit is as follows:
The preferred display brightness is denoted by L _PRE ,
An average display brightness that is an average value of display brightness indicated by the image data is indicated by L _DIS ,
When the predetermined coefficients are indicated by C ₃ , C ₄ , and p,
The following second formula

It is calculated by using the,
Said coefficients _{C 3} is set to a value in the range of 0.2 to 0.4,
The coefficient _{C 4} is set to a value in the range of 0.1 to 0.3,
The coefficient p is an image display apparatus according to any one of claims 1 to 3, characterized in that it is set to a value in the range of 1.5 to 1.8. It said coefficients _{C 3} is set to a value in the range of 0.296 or more 0.348 or less,
The coefficient _{C 4} is set to a value in the range of 0.15 or more 0.218 or less,
The image display device according to claim 4 , wherein the coefficient p is set to a value within a range of 1.52 to 1.676. The image display device according to claim 4, further comprising an input unit that changes a value of the coefficient p. The first illuminance measurement unit includes a front illuminance sensor provided on the front surface of the housing,
The second illuminance measurement unit, an image display device according to item 1 any one of claims 1 to 6, characterized in that it comprises a rear illumination sensor provided in the rear of the housing. The image display unit is a liquid crystal display unit,
The image display surface is a liquid crystal display panel provided with a backlight,
The image display device according to any one of claims 1 to 7 , wherein the display control unit includes a backlight control unit that controls luminance of the backlight. A surface reflectance calculation unit that calculates the reflectance of the image display surface based on the measurement value of the first illuminance measurement unit;
A black level calculator that calculates a black level suitable for a display image using the reflectance; and
The image display apparatus according to any one of claims 1 to 8 , wherein the display control unit changes a black level of a display image in accordance with the calculated black level. A surface reflectance calculation unit that calculates the reflectance of the image display surface based on the measurement value of the first illuminance measurement unit;
A saturation calculation unit for calculating a saturation suitable for a display image using the reflectance; and
The image display apparatus according to any one of claims 1 to 8 , wherein the display control unit changes a saturation of a display image according to the calculated saturation. Further comprising a saturation calculation unit for calculating a saturation suitable for the display image using the reflectance,
The image display device according to claim 9 , wherein the display control unit changes a saturation of a display image according to the calculated saturation.

Images