JP2010085891A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device capable of displaying an image with easily viewable brightness and capable of reducing power consumption. <P>SOLUTION: The display device 100 includes: a picture illuminance measurement unit 1 for measuring the picture illuminance Ei of a display device 15; a setting condition input unit 2 for input of the information of an observer of the display device 15 and the information of a visual distance L between the display device 15 and the observer; an operation unit 51 for finding out luminance at which the observer begins to feel glare based on the picture illuminance Ei and the information input to the setting condition input unit 2; a picture luminance control unit 7 for determining the maximum luminance of the display device 15 in a range which does not exceed the luminance found out by the operation unit 51; and a control signal generation unit 40 for generating a control signal for controlling the luminance of the display device 15 to the same luminance as the maximum luminance or luminance most close to the maximum luminance in a predetermined luminance range in which the efficiency of light emission of the display device 15 is high and controlling the luminance of the display device 15 by using the control signal. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a display device that automatically adjusts screen brightness to brightness suitable for a viewer.

  In recent years, flat panel display devices such as liquid crystal display devices and plasma display devices have become widespread in television receivers used in general homes, instead of cathode ray tube displays. In the flat panel type display device, the brightness has been increased by improving the device performance. However, increasing the brightness of the display device increases the visibility, but causes fatigue and eye fatigue due to a dazzling feeling.

  In addition, there is a problem that power consumption increases in order to increase the brightness of a liquid crystal display device or a plasma display device.

  For these reasons, a method of mounting a light receiving element for measuring ambient brightness on a display device and adjusting screen brightness in accordance with the ambient brightness environment is generally performed. For example, the screen brightness is adjusted low when the surroundings are dark, and the screen brightness is adjusted high when the surroundings are bright. Thereby, visibility in a bright environment and a dazzling feeling in a dark environment can be suppressed, and power consumption can also be reduced.

  For example, in a conventional display device, the screen brightness is automatically adjusted to a brightness that is easy for a viewer to view based on the ambient light of the display device. Specifically, a light receiving element is arranged in the vicinity of the display device toward the viewer, the brightness in the vicinity of the display device is measured by the light receiving element, and the brightness of the display device is obtained based on the measurement result. Is adjusted so that the viewer can easily see the brightness. The luminance of the display device is calculated from the brightness in the vicinity of the display device and a certain constant (for example, Patent Document 1).

  In another conventional display device, the brightness of the screen is set with parameters such as the visual acuity and age of the viewer, the size of the display screen, the viewing distance that is the distance between the display device and the viewer, and the illuminance of the display screen. By calculating, the screen brightness is adjusted to a brightness suitable for the brightness environment and the characteristics of the viewer (for example, Patent Document 2).

JP-A-6-308991 (pages 4 to 6, FIG. 1) JP 2007-279405 A

  In a conventional display device, it is necessary to control the brightness of the display device. For example, in a liquid crystal display device that is cited as an example of a display device, brightness control of the backlight device is necessary as a method for controlling the brightness. Become. As a structure of a backlight apparatus, it is comprised from the light source and the light-guide plate for carrying out the plane light emission of the light of a light source. Conventionally, the light source using CCFL (Cold Cathode Tube) has been mainly used as a light source. However, in recent years, particularly for small devices such as mobile phones and high color gamut displays, a backlight device using LEDs (hereinafter referred to as LED). The so-called backlight device has become the mainstream. With regard to the brightness control of this LED backlight device, there are cases where the direct current flowing through the LED is simply controlled, but there are more cases where the control is performed by changing the duty ratio of the PWM signal that can be easily controlled by a CPU or the like. Yes.

  Moreover, in the conventional display apparatus, the power saving of the display apparatus was implement | achieved by controlling the brightness of a display device so that a viewer may not feel glare. For example, in the case of a liquid crystal display device, the brightness of the backlight device is controlled by simply changing the current applied to the backlight LED. The power consumption of the backlight device is determined by the product of the LED forward voltage and the current value. Since the relationship between the brightness of the LED and the applied current generally varies linearly, for example, to increase the brightness of the backlight device in order to increase the brightness of the backlight device, it is necessary to increase the applied current. Power consumption increases.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a display device that can display an image with brightness that is easily visible to a viewer of the display device and can reduce power consumption. To do.

  In order to solve the above object, a first aspect of the present invention includes a display device, a screen illuminance measurement unit that measures screen illuminance of the display device, information on a viewer of the display device, and the display device. Based on the setting condition input unit for inputting information of the viewing distance, which is the distance to the viewer, the screen illuminance measured by the screen illuminance measuring unit and the information input to the setting condition input unit, A calculation unit that determines the luminance of the display device that the viewer starts to feel dazzling; a screen luminance control unit that determines the maximum luminance of the display device within a range not exceeding the luminance determined by the calculation unit; and the display A control signal for controlling the brightness of the device to a brightness closest to the maximum brightness determined by the screen brightness control unit within a predetermined brightness range where the light emission efficiency of the display device is good, A control signal generator for controlling the brightness of the display device by using a control signal in which comprises a.

  According to the first aspect of the present invention, the brightness of the display device that the viewer starts to feel dazzling is obtained based on the screen illuminance of the display device and the viewer's information, and the display device's brightness is within a range that does not exceed the brightness. The maximum brightness is determined, and the brightness of the display device is controlled to the brightness closest to the maximum brightness within a predetermined brightness range where the light emission efficiency of the display device is good. This makes it possible to reduce viewer fatigue even when viewed for a long time. Furthermore, since the luminance of the display device is controlled in consideration of increasing the light emission efficiency of the display device, power consumption can be reduced.

Embodiment 1 FIG.
<Overall configuration>
As shown in FIG. 1, the display device 100 according to this embodiment includes a screen illuminance measurement unit 1, a setting condition input unit 2, a background luminance calculation unit 3, a storage unit 4, and a luminance adjustment constant calculation unit 5. , Brightness sensation luminance calculation unit 6, screen luminance control unit 7, video signal luminance calculation unit 9, distance sensor 10, video signal analysis unit 12, viewing angle constant calculation unit 13, imaging unit 14, and display A device 15 and a backlight control signal generation unit 40 are provided. The calculation unit 51 is configured by the units 3, 4, 5, 6, 11, and 13.

  The display device 15 includes a liquid crystal panel 18, a liquid crystal display driver 50 that drives the liquid crystal panel 18, a backlight device 19 for the liquid crystal panel 18, and a backlight control unit 16 that controls the luminance of the backlight device 19. Is done. The backlight device 19 includes a backlight light source 19a and a light guide plate 19b for planarly emitting light from the light source 19a. Here, the backlight light source 19a is configured by using, for example, LEDs 19c of RGB colors as shown in FIG.

  In the display device 15, the liquid crystal display driver 50 drives the liquid crystal panel 18 based on the video signal to generate an image on the liquid crystal panel 18. Then, the backlight control unit 16 controls the luminance of the backlight device 19 based on the backlight control signal from the backlight control signal generation unit 40. As a result, the video generated on the display panel 18 is illuminated (that is, displayed) with the optimum brightness for the viewer.

  Here, the characteristics of the display device 100 will be described.

  The human eye is affected by all light in view. FIG. 2 is a diagram for explaining an experiment in which the background brightness around the display device 15 and the brightness of the display device 15 at which the viewer 20 starts to feel dazzle are evaluated by the subjectivity of the viewer 20. For example, the display device 100 is installed in a theater room, and the viewer 20 is viewing the display device 100. A region that affects the field of view of the viewer 20 is divided into two regions. One is a display screen area (television screen area 21) of the display device 15, and the other is a surrounding area (background luminance area 22) of the television screen area 21.

  Here, if the dazzling feeling of the viewer 20 is affected by the area ratio between the TV screen area 21 and the background luminance area 22 in the field of view, the dazzling feeling of the viewer 20 is determined by the TV screen area 21. And its brightness, the area of the background luminance region 22 and its brightness, the visual acuity of the viewer 20, the viewing distance, and the like. For this reason, a simple method of adjusting the brightness (luminance) of the display screen by only measuring the brightness of the background luminance region 22 does not necessarily adjust the brightness to the optimal level for the viewer 20. . Therefore, in order to adjust the brightness of the display screen to the optimum brightness for the viewer, it is necessary to further consider the area of the TV screen region 21 and its brightness, the visual acuity of the viewer 20, the viewing distance, and the like. (It is desirable that the age of the viewer 20 is actually reflected as described later).

  Therefore, the display device 100 displays on the display device 15 in consideration of the area and brightness of the television screen area 21, the area and brightness of the background luminance area 22, the visual acuity of the viewer 20, the viewing distance, and the like. By controlling the luminance of the device 15, the luminance of the display screen is optimized for the viewer (that is, viewing) within a range where the light emission efficiency of the display device 15 can be increased (that is, a range considering power saving). The maximum brightness within a range not exceeding the brightness at which the person begins to feel dazzling is adjusted.

  Next, a description will be given of how to determine the luminance at which the viewer begins to feel dazzling.

  A preliminary experiment conducted to clarify the above (the fact that the dazzling feeling of the viewer 20 is affected by the area ratio between the TV screen region 21 and the background luminance region 22 in the field of view) will be described. The relationship between the screen illuminance Ei of the display device 15 and the surrounding background luminance La when the brightness of the room in which the display device 100 is installed was changed by illumination or the like was obtained.

  Here, as described above, the screen illuminance Ei is the illuminance near the center of the display device 15 when the display device 15 is off, and is measured near the display device 15 with the illuminance meter facing the viewer 20. Brightness. The background luminance La is obtained by capturing the imaging device 100 with a fisheye image having a 180-degree field of view from the position of the viewer 20, and excluding the luminance of the display screen of the display device 100 by performing image processing on the captured image. The luminance is the average of the luminance of only the background portion of the display device 100. As a result of the measurement, it was found that the screen illuminance Ei and the background luminance La can be satisfactorily approximated by a linear relational expression as shown in Equation 1.

La = Re × Ei (1)
Here, Re is a constant (background luminance calculation constant) determined by the reflectance of the wall of the room, the shape of the room, the relative position between the display device 100 and the viewer, and the like.

FIG. 3 shows a result of an experiment for determining the relationship between the background luminance La and the luminance Lw of the display device 15 at which the viewer begins to feel dazzling. Experiments under background luminance La is ^{5cd / m 2, 0cd / m} 2, each lighting environment of 80 cd / m ^2, of different sizes circular pattern on the display device 15 (viewing angle φ = 1 °, 5 °, 25 °) is displayed and presented to 20 young people from 18 to 24 years old, for example, and 24 elderly people from 65 to 80 years old, for example. It was done in a way that evaluates the brightness to start feeling. In addition, the item of subjective evaluation was made into 1 item regarding a dazzling feeling, and the evaluation scale was evaluated in four steps.

  Note that the viewing angle φ of the circular pattern is obtained by the equation (2) from the viewing distance L between the display device 15 and the viewer 20 and the area S of the circular pattern as shown in FIG.

φ = 2 × Tan ⁻¹ (√ (S / π) / L) (2)
Since the above description is a principle description, a circular pattern is used for convenience. However, in actuality (that is, in a situation where the viewer is viewing the display device 100), an image being displayed on the display device 100 is displayed. The effective area of (display image) is used as the area S.

The above experiment was performed with the viewing distance L fixed at, for example, 1 m. Then, each of the above illumination environment ^{(La = 5cd / m 2,} 20cd / m 2, 80cd / m 2) and the viewing angle (φ = 1 °, 5 ° , 25 °) in, the circular pattern on the display device 15 The luminance was gradually increased, and the luminance Lw of the display device 15 when each viewer began to feel dazzling was measured. In FIG. 2, the average values of 20 young people and 24 elderly people are plotted as the luminance Lw at which dazzling begins to be felt. From this experimental result, Expression (3) was obtained as a relational expression between the background luminance La and the luminance Lw at each viewing angle φ.

Lw = k × La ^α (3)
Here, α is a visual constant, and k is a luminance adjustment constant. 3, the visual constant α is a constant related to the age Ag and the viewing angle φ, and the luminance adjustment constant k is a constant mainly related to the viewing angle φ (that is, the size of the display screen and the viewing distance L). In this way, the luminance Lw at which the viewer begins to feel dazzling is obtained from the expression (3). In the display device 100, the luminance of the display screen is determined from the luminance Lw and video information displayed on the display screen.

  Next, the luminance of the display screen in a range where the light emission efficiency of the display device 15 (that is, the backlight device 19) can be increased will be described.

As described above, the luminance of the display screen is determined from the luminance Lw of the display device 15 when the viewer starts to feel dazzling and the video information displayed on the display screen. For example, in FIG. 3, in the case where the background luminance La = 1 cd / m ² (the brightness when the room illumination is turned off to watch a movie in the room) and the viewing angle φ = 25 °, the young person displays the display device 15 When the brightness exceeds 160 cd / m ² , the display screen starts to feel dazzling.

Therefore, in a recent general liquid crystal TV having a maximum screen brightness of 500 cd / m ² , if the screen brightness of the TV is not set sufficiently dark, the maximum brightness remains dazzling and the viewer's eyes I can see that I get tired. In order to solve this, it is effective to reduce the luminance of the display device 15 in an environment where the background luminance La is low.

  Many means are conceivable for reducing the screen brightness. For example, in the case of the display device 15 shown in FIG. 1, since an LED is used as the backlight light source 19a, the drive current flowing through the backlight light source 19a may be reduced in order to reduce the screen brightness. Specifically, since the drive current of the backlight light source 19a is controlled by the backlight control unit 16, the backlight is controlled by the change in the frequency F or the duty ratio D of the PWM signal P from the backlight control signal generation unit 40, for example. The brightness of the light source 19a may be reduced.

  The PWM signal P is a digital signal represented by “0” or “1”, and is controlled by converting the current value of the backlight light source 19a into the duty ratio D of the pulse signal. For example, when the duty ratio D = 50%, “0” and “1” are generated at the same ratio per unit time, and when the duty ratio D = 5%, “0” and “1”. Is generated at a ratio of 95: 5.

  Here, by driving the backlight light source 19a by the PWM signal P, the light emission efficiency of the backlight light source 19a may be dramatically increased as compared with the case where the light source 19a is DC driven. Among the new technology presentations held by the Japan Science and Technology Agency, LED lighting using the visual psychological effect of pulse drive at the “New Technology Briefing Meeting from Shikoku Area Four Universities” held on April 4, 2008 In the “High efficiency technology” (Masafumi Kamino, Associate Professor, Department of Electronic Information Engineering, Graduate School of Science and Engineering, Ehime University) There is a report that it feels 30% to 60% or more brighter than in the case of, and if this technology is used, it becomes possible to significantly reduce current consumption as compared with the case of conventional DC lighting.

  The frequency is ideally 60 Hz as described above. However, since it is necessary to adjust according to the display device 15, it is desirable to consider in the range of 40 Hz to 120 Hz including 60 Hz. This range is a range that takes into account that deterioration in image quality due to flicker or the like is noticeable at 40 Hz or less, and that hardware cannot be used at 120 Hz or more.

  The duty ratio is ideally 5% as described above. However, since it is necessary to adjust the duty ratio according to the display device 15, it is desirable to consider it in the range of 5% to 20%. This range takes into consideration that the luminance is too dark at less than 5%, and that the luminous efficiency deteriorates at more than 20%.

  As described above, in the display device 100, as the luminance of the display screen in the range in which the light emission efficiency of the display device 15 (that is, the backlight device 19) can be increased, for example, the frequency is considered to be in the range of 40 Hz to 120 Hz. Consider a range of 5% to 20% for the ratio. Thereby, the light emission efficiency of the display device 15 can be made extremely high compared with the case of the conventional direct current lighting.

  Based on the above, each part of the display device 100 will be described.

  Although not shown, the screen illuminance measurement unit 1 is a light receiving element that includes, for example, a silicon photodiode subjected to visibility correction and an amplifier. The screen illuminance measurement unit 1 is arranged near the center of the display device 15 so as to face the viewer, and measures the illuminance (screen illuminance Ei) near the center of the display device 15 when the display device 15 is off. To do. If it is difficult to arrange the screen illuminance measuring unit 1 near the center of the display device 15, it is not problematic to arrange it near the display device 15 and approximate the measured illuminance to the screen illuminance Ei. .

  The setting condition input unit 2 includes a light receiving unit that receives remote control light from a predetermined remote control device (not shown), and receives a predetermined condition (for example, transmitted from the predetermined remote control device by an operator's remote control operation). The age Ag and visual acuity of the viewer, conditions such as the background luminance calculation constant Re, and the viewing distance L are received and stored in the storage unit 4. Note that information such as age described above may use a predetermined default value if it is not input by remote control operation.

  Although not shown, the imaging unit 14 includes an image sensor and an image processing device, and is disposed, for example, in the vicinity of the display device 15. The imaging unit 14 images a viewer of the display device 100, performs image processing on the captured image, and detects the distance (viewing distance) L between the viewer and the display device 15 and the age Ag of the viewer. . As a method for detecting the viewing distance L and the age Ag, a well-known image processing technique can be used. The detection results L and Ag are stored in the storage unit 1 via the setting condition input unit 2, for example.

  In addition, as a method for detecting the age from the captured image, for example, the features such as the face color, eyes, nose, and mouth position in the human face are stored in a database for each person of different age and gender and extracted from the captured image. Further, by comparing the characteristics, the age of the subject person can be specified (hereinafter referred to as face information comparison technology, for example, Japanese Patent No. 0380696 and Japanese Patent No. 03811474).

  As a method for detecting the viewing distance L from the captured image, the area of the entire face can be calculated by using the face information comparison technique described above. Here, in the captured image obtained by the imaging unit 14 in advance, if the relationship between the human face area and the viewing distance L is obtained, the distance L is obtained from the face area.

  The distance sensor 10 uses, for example, ultrasonic waves, and is disposed, for example, in the vicinity of the display device 15 and detects the distance (viewing distance) L between the viewer and the display device 15. The detection result L is stored in the storage unit 1 via the setting condition input unit 2, for example.

  Here, the setting of the viewing distance L is selectively set by any one of a predetermined remote controller, the imaging unit 14, and the distance sensor 10. The setting of the viewer's age Ag is also selectively performed by any one of the predetermined remote controller and the imaging unit 14. These selections can be made with the predetermined remote controller or a selection switch (not shown).

  The background luminance calculation unit 3 obtains the background luminance La from the constant Re stored in the storage unit 4 and the screen illuminance Ei measured by the screen illuminance measurement unit 1 based on the formula (1). The background luminance La is stored in the storage unit 4.

  The video signal analysis unit 12 obtains the effective area S for the video (display image) displayed on the display device 15 from the video signal. The effective area S may be simply the area of the display screen of the display device 15 or may be obtained by multiplying the area of the display screen of the display device 15 by a constant smaller than 1. Thereby, the video signal analysis part 12 can be made unnecessary.

  The visual constant calculation unit 13 calculates the effective video displayed on the display device 15 from the viewing distance L stored in the storage unit 4 and the area S obtained by the video signal analysis unit 12 based on the equation (2). The visual φ of the area S is determined. This vision φ is stored in the storage unit 4.

  In the brightness adjustment constant calculation unit 5, a relationship between the brightness adjustment constant k, the visual φ, and the viewer's age Ag is set, and the brightness adjustment constant calculation unit 5 is stored in the storage unit 4 based on the relationship. A brightness adjustment constant k suitable for the viewer is obtained from the visual sight φ and the age Ag of the viewer. The constant k is stored in the storage unit 4.

  In addition, as said relationship, the table which gives the luminance adjustment constant k from viewing angle (phi) and age Ag may be used, and the appropriate functional formula obtained from the experimental result shown in FIG. 3 may be used. Further, here, the luminance adjustment constant k is obtained based on the visual φ and the age Ag of the viewer. However, since the luminance adjustment constant k mainly depends on the visual φ, only the visual φ is used without using the information on the age Ag. The adjustment constant k may be obtained.

  The visual information calculation unit 11 is set with a relationship between the visual constant α, the age Ag, and the viewing angle φ, and the visual information calculation unit 11 stores the visual φ and the age Ag stored in the storage unit 4 based on the relationship. From this, a visual constant α suitable for the viewer is obtained. The constant α is stored in the storage unit 4.

  In addition, as said relationship, the table which gives visual constant (alpha) from age Ag and viewing angle (phi) may be used, and the appropriate functional formula obtained from the experimental result shown in FIG. 3 may be used. In addition to the viewer's age Ag and viewing angle φ, the visual constant α is determined in consideration of the visual acuity of the viewer stored in the storage unit 4 so as to determine a better visual constant α. Anyway.

  The brightness sensation luminance calculation unit 6 calculates the luminance Lw of the display device 15 when the viewer starts to feel dazzling from the constants La, k, α stored in the storage unit 4 based on Expression (3). Ask.

  The video signal luminance calculation unit 9 obtains the luminance distribution and average luminance of the video (display image) displayed on the display device 15 based on the video signal.

  The screen luminance control unit 7 is based on the luminance Lw obtained by the brightness sensation luminance calculating unit 6 and the luminance distribution and average luminance of the video obtained by the video signal luminance calculating unit 9 and is maximum within a range not exceeding the luminance Lw. The maximum luminance of the video signal (that is, the display device 15) is obtained, and the luminance information B of the video displayed on the display device 15 is generated based on the maximum luminance and is output to the backlight control signal generation unit 40.

  The backlight control signal generation unit (control signal generation unit) 40 is the same as the maximum luminance determined by the screen luminance control unit 7 in a predetermined luminance range in which the light emission efficiency of the backlight device 19 of the display device 15 can be increased. The brightness of the display screen of the display device 15 is controlled so that the brightness is at or near the brightness.

  The backlight control signal generation unit 40 includes a backlight PWM signal generation unit 41 of the display device 15, a duty selection circuit 42, and a frequency selection circuit 43.

  Based on the luminance information B from the screen luminance control unit 7, the duty selection circuit 42 is used for PWM driving for setting the screen luminance of the display device 15 to the maximum luminance within a range that does not exceed the luminance at which the viewer begins to feel dazzling. A first duty ratio is obtained. In the duty selection circuit 42, a predetermined duty ratio range (for example, a range of 5% to 20%) is set as a range of the duty ratio for causing the backlight device 19 to emit light with high light emission efficiency. When the obtained first duty ratio is included in the predetermined duty ratio range, the duty selection circuit 42 uses the first duty ratio as a duty ratio D for PWM driving of the backlight device 19 to perform PWM. On the other hand, when the calculated first duty ratio is not included in the predetermined duty ratio range, the first duty ratio is set within the predetermined duty ratio range. The closest value is output to the PWM signal generation unit 41 as the duty ratio D for PWM driving of the backlight device 19.

  The frequency selection circuit 43 is based on the luminance information B from the screen luminance control unit 7 and is used for PWM driving for setting the screen luminance of the display device 15 to the maximum luminance that does not exceed the luminance at which the viewer starts to feel dazzling. Find the first frequency. In the frequency selection circuit 43, a predetermined frequency range (for example, a range from 40 Hz to 120 Hz) is set as a frequency range for causing the backlight device 19 to emit light with high light emission efficiency. When the obtained first frequency is included in the predetermined frequency range, the frequency selection circuit 43 sets the first frequency as the PWM driving frequency F of the backlight device 19 and the PWM signal generation unit 41. On the other hand, when the obtained first frequency is not included in the predetermined frequency range, a value closest to the first frequency within the predetermined frequency range is set to the backlight. The frequency is output to the PWM signal generator 41 as the PWM driving frequency F of the device 19.

  The PWM signal generation unit 41 is a PWM signal (backlight control) for PWM driving the backlight device 19 of the display device 15 based on the duty ratio D from the duty selection circuit 42 and the frequency F from the frequency selection circuit 43. Signal) P is generated and output to the backlight control unit 16 of the display device 15. As a result, as described above, the image generated on the display panel 18 has an optimum luminance for the viewer (that is, the viewer is dazzled) within a predetermined luminance range in which the light emission efficiency of the backlight device 19 can be increased. The maximum brightness within a range that does not exceed the brightness at which it begins to feel.

<Overall operation>
Next, the operation of the display device 100 will be described.

  When the display device 15 is turned off by the screen illuminance measurement unit 1, the illuminance near the center of the display device 15 (screen illuminance Ei) is measured, and the measurement result is output to the background luminance calculation unit 3.

  The setting condition input unit 2 receives information such as the age Ag and visual acuity of the viewer, the background luminance calculation constant Re, and the visual distance L from a predetermined remote control device, the distance sensor 10 and the imaging unit 14. Information is stored in the storage unit 4.

  Then, the background luminance calculation unit 3 obtains the background luminance La from the screen illuminance Ei from the screen illuminance measurement unit 1 and the background luminance calculation constant Re stored in the storage unit 4 based on the equation (1). The background luminance La is stored in the storage unit 4.

  The video signal analyzing unit 12 analyzes an external video signal and calculates an effective area S of a video (display image) displayed on the display device 15. Then, the visual angle constant calculation unit 13 calculates the video image based on the expression (2) from the viewing distance L stored in the storage unit 4 and the effective area S of the video image analyzed by the image signal analysis unit 12. An effective viewing angle φ of the area S is obtained. The viewing angle φ is stored in the storage unit 4.

  Further, the luminance adjustment constant calculator 5 obtains the luminance adjustment constant k from the age Ag and the visual φ stored in the storage unit 4 based on the relationship between the preset age Ag and the visual φ. The brightness adjustment constant k is stored in the storage unit 4.

  The visual information calculation unit 11 obtains a visual constant α suitable for the viewer based on the relationship between the age Ag and the viewing angle φ set in advance from the age Ag and the viewing angle φ stored in the storage unit 4. . The visual constant α is stored in the storage unit 4.

  Then, the background luminance La, the luminance adjustment constant k, and the visual constant α are output from the storage unit 4 to the brightness sensation luminance calculation unit 6. The brightness sensation luminance calculation unit 6 obtains the luminance Lw at which the viewer starts to feel dazzling based on Expression (3) from these pieces of information La, α, k.

  Then, the screen luminance control unit 7 has a range that does not exceed the luminance Lw based on the luminance distribution and average luminance of the video signal obtained by the video signal luminance computing unit 9 and the luminance Lw obtained by the brightness-sensitive luminance computing unit 6. The maximum luminance of the video signal (that is, the display device 15) which is the maximum is obtained, and the luminance information B of the video displayed on the display device 15 is generated based on the maximum luminance and is output to the backlight control signal generation unit 40.

  Then, the backlight control signal generation unit 40 obtains the first duty ratio and the first frequency based on the luminance information B from the screen luminance control unit 7. When the first duty ratio is included in a predetermined duty ratio range (for example, 5% to 20%) set in advance, the first duty ratio is set as the duty ratio for PWM drive of the backlight device 19. If the first duty ratio is not included in the predetermined duty ratio range, the duty ratio closest to the first duty ratio within the predetermined duty ratio range is backed up. The duty ratio D for PWM drive of the light device 19 is determined. Similarly, when the first frequency is included in a preset predetermined frequency range (for example, 40 Hz to 120 Hz), the first frequency is determined as the PWM driving frequency F of the backlight device 19. On the other hand, if the first frequency is not included in the predetermined frequency range, the frequency closest to the first frequency within the predetermined frequency range is used for the PWM drive of the backlight device 19. Determined as frequency F. Based on the duty ratio D and the frequency F, a PWM signal (backlight control signal) P for PWM driving the backlight device 19 is generated and output to the display device 15.

  In the display device 15, an image is generated on the liquid crystal panel 18 based on the video signal by the liquid layer display driver 50, and a backlight device based on the PWM signal P from the backlight control signal generation unit 40 by the backlight control unit 16. 19 is brightness controlled. As a result, the image generated on the display panel 18 exceeds the optimum luminance for the viewer (that is, the luminance at which the viewer starts to feel dazzling) within a predetermined luminance range in which the light emission efficiency of the backlight device 19 can be increased. (Maximum brightness in no range).

  According to the display device 100 configured as described above, the luminance Lw of the display device 15 at which the viewer starts to feel dazzling is obtained based on the screen illuminance Ei of the display device 15 and the information of the viewer, and the luminance Lw The maximum brightness of the display device 15 is determined within a range not exceeding the threshold, and the brightness of the display device 15 is controlled to the brightness closest to the maximum brightness within a predetermined brightness range where the light emission efficiency of the display device 15 is good. An image can be displayed with a brightness that is easy to see depending on the viewer, thereby reducing the fatigue of the viewer even when viewed for a long time. Further, since the luminance of the display device 15 is controlled in consideration that the luminous efficiency of the display device 15 is increased, the power consumption can be reduced.

  Further, the backlight control signal generation unit 40 outputs the PMW signal P to the backlight control unit 16, and sets the frequency F of the PWM signal P to the maximum brightness within a predetermined frequency range where the light emission efficiency of the display device 15 is good. The duty ratio D of the PWM signal P is controlled to the same value as or the value closest to the corresponding frequency, and the duty ratio corresponding to the maximum luminance is within a predetermined duty ratio range where the light emission efficiency of the display device 15 is good. Therefore, the display device 15 is applicable to the case where the display device 15 includes the backlight device 19 and the brightness of the backlight device 19 is PWM-controlled.

  Further, the predetermined duty ratio range is in the range of 5% to 20%, and the predetermined frequency range is in the range of 40 Hz to 120 Hz. Therefore, the light emission of the backlight device is considered in consideration of image quality and hardware limitations. High efficiency can be achieved.

  In addition, since the viewer information includes the age of the viewer, the brightness of the display device 15 at which the viewer starts to feel dazzling can be obtained more appropriately in consideration of the age of the viewer.

  In order to input the viewer's age, the imaging unit 14 is provided for capturing the viewer, determining the age of the viewer based on the captured image, and inputting the determined age to the setting condition input unit. Can be omitted.

  Further, the background luminance La around the display device 100 is obtained based on the screen illuminance Ei measured by the screen illuminance Ei measurement unit, and the viewer begins to feel dazzling based on the background luminance La, the viewer information, and the viewing distance L. Since the luminance Lw of the display device 15 is obtained, that is, the background luminance La is taken into consideration in addition to the viewer information and the viewing distance L, the luminance of the display device 15 that starts to feel dazzling is more appropriately obtained. Can do.

  Based on the viewing distance L and the effective display screen area S of the display device 15, the effective viewing angle φ of the display screen viewed from the viewer is obtained, and based on the viewing angle φ, the screen illuminance Ei, and the viewer information. Since the brightness of the display device 15 that the viewer starts to feel dazzling is obtained, that is, in addition to the screen illuminance Ei and the viewer information, the effective viewing angle φ of the display screen S viewed from the viewer is considered. The brightness | luminance of the display device 15 which a viewer begins to feel dazzling can be calculated | required more appropriately.

  Since the maximum luminance of the display device 15 is determined within a range not exceeding the luminance of the display device 15 that the viewer starts to feel dazzling based on the luminance information extracted by the video signal luminance calculation unit 9 (luminance information of the display image). That is, since the luminance information of the display image is determined in consideration, the maximum luminance of the display device 15 can be more appropriately determined within a range that does not exceed the luminance of the display device 15 where the viewer starts to feel dazzling.

Embodiment 2. FIG.
In this embodiment, a specific value of the background luminance coefficient Re when the background luminance coefficient Re is set as a fixed value in the setting condition input unit 2 or the storage unit 4 in advance is examined.

  FIG. 5 is a plot of the results of measuring the screen illuminance Ei and the background luminance La in a room where a television is placed in 50 ordinary homes. In FIG. 5, straight lines are drawn when the background luminance coefficient Re of the formula (1) is 1.0 and 0.2. From FIG. 5, it can be seen that, in the environment in a general home, all the home environments can be reflected by setting the background luminance coefficient Re to a value of 1.0 or less. It can also be seen that in a general home environment, it is appropriate to set the background luminance coefficient Re to 0.2.

  In this way, by setting the background luminance coefficient Re to a fixed value, the calculation (calculation for obtaining La) in the background luminance calculation unit 3 can be facilitated.

1 is a block diagram illustrating an image display device according to a first embodiment. It is a figure explaining the subjective evaluation experiment of the brightness | luminance Lw of the display device 15 which begins to feel background brightness | luminance La and dazzling. It is the figure which showed the relationship between the brightness | luminance Lw of the display screen which begins to feel glare, and background brightness | luminance La. It is the figure which showed the relationship between viewing angle (phi), the area S of a display pattern, and the viewing distance L. FIG. It is the figure which showed the relationship between screen illumination intensity Ei and background brightness | luminance La in Embodiment 2. FIG. It is the structure schematic diagram of 19 of the backlight apparatus at the time of comprising the light source 19a for backlights by LED19c of each color of RGB.

Explanation of symbols

  1 screen illuminance measurement unit, 2 setting condition input unit, 3 background luminance calculation unit, 4 storage unit, 5 luminance adjustment constant calculation unit, 6 brightness sensation luminance calculation unit, 7 screen luminance control unit, 9 video signal luminance calculation unit, DESCRIPTION OF SYMBOLS 10 Distance sensor, 11 Visual information calculating part, 13 Visual constant calculating part, 14 Imaging part, 16 Backlight control part, 18 Liquid crystal panel, backlight apparatus, 19a Light source for backlight, 19b Light guide plate, 40 Backlight control signal generation Unit, 41 PWM signal generation unit, 42 duty selection circuit, 43 frequency selection circuit, 50 liquid crystal driver, 51 calculation unit.

Claims (8)

A display device;
A screen illuminance measurement unit for measuring the screen illuminance of the display device;
A setting condition input unit for inputting information of a viewer of the display device and information of a viewing distance which is a distance between the display device and the viewer;
Based on the screen illuminance measured by the screen illuminance measurement unit and the information input to the setting condition input unit, a calculation unit that calculates the luminance of the display device that the viewer starts to feel dazzling,
A screen brightness control unit for determining the maximum brightness of the display device within a range not exceeding the brightness obtained by the calculation unit;
A control signal for controlling the brightness of the display device to the same brightness as the maximum brightness determined by the screen brightness control unit or the brightness closest thereto within a predetermined brightness range in which the light emission efficiency of the display device is good. And a control signal generation unit that controls the luminance of the display device using the control signal;
A display device comprising: The display device is
LCD panel,
A backlight device for the liquid crystal panel;
A backlight control unit that PWM-controls the luminance of the backlight device according to the control signal,
The control signal generator is
A PWM signal generator that outputs a PMW signal to the backlight controller as the control signal;
The frequency of the PWM signal is controlled to the same value as the frequency corresponding to the maximum luminance determined by the screen luminance control unit or the value closest thereto within a predetermined frequency range where the light emission efficiency of the display device is good. A frequency selection circuit;
The duty ratio of the PWM signal is the same value as or closest to the duty ratio corresponding to the maximum brightness determined by the screen brightness control unit within a predetermined duty ratio range where the light emission efficiency of the display device is good. A frequency selection circuit to control,
The display device according to claim 1, further comprising: The predetermined duty ratio range is in the range of 5% to 20%;
The display device according to claim 2, wherein the predetermined frequency range is within a range of 40 Hz to 120 Hz.   The display device according to claim 1, wherein the information of the viewer includes an age of the viewer.   5. The image processing apparatus according to claim 4, further comprising an imaging unit that images the viewer, determines the age of the viewer based on the captured image, and inputs the determined age to the setting condition input unit. The display device described.   The calculation unit obtains a background luminance around the display device based on the screen illuminance measured by the screen illuminance measurement unit, and the viewer based on the background luminance, the viewer information, and the viewing distance. The display device according to claim 1, wherein brightness of the display device that starts to feel dazzling is obtained.   The calculation unit obtains a viewing angle of the effective display screen viewed from the viewer based on the viewing distance and an effective display screen area of the display device, and calculates the viewing angle, the screen illuminance, and the viewing angle. The display device according to claim 1, wherein brightness of the display device at which the viewer starts to feel dazzling is obtained based on information of the viewer. A video signal luminance calculation unit for extracting luminance information of a display image from a video signal displayed on the display device;
The screen luminance control unit determines the maximum luminance of the display device within a range not exceeding the luminance obtained by the calculation unit based on luminance information extracted by the video signal luminance calculation unit. Item 8. The display device according to any one of Items 1 to 7.

Images