Lighting device, display device, and method for controlling lighting device

Abstract

To reduce the temperature of a lighting device while maintaining visibility.SOLUTION: A lighting device includes a backlight (12) having a plurality of lighting areas (Bi) and a control unit (16), and the control unit acquires brightness information corresponding to the brightness of each lighting area, derives usage information indicating the usage level of the lighting area on the basis of the brightness information for each lighting area, detects lighting areas having usage information corresponding to a high usage range equal or above a predetermined usage level, and reduces the brightness of the detected one or more lighting areas.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a lighting device, a display device, and a method for controlling a lighting device. [Background technology]

[0002] Patent Document 1 discloses a technique for realizing a liquid crystal display device that effectively suppresses temperature rise in the LEDs of the backlight while suppressing brightness reduction. To achieve this, in the technique described in Patent Document 1, a backlight drive control unit reduces the power supplied to the backlight when the duty ratio of the LEDs is equal to or greater than a threshold for a certain period of time. The backlight drive control unit counts the cumulative number of times the duty ratio is equal to or greater than the threshold, and repeats this process until the cumulative number falls below a lower limit at all points in the backlight (see paragraph 0069). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-45000 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned technology, the brightness is maintained at a reduced level at all points of the backlight until the cumulative number of times falls below the lower limit, which can easily reduce the visibility of the image. For example, when a high-brightness object such as an illuminated object is placed in an overall dark image, such as a night scene, the brightness of the entire image decreases, reducing the visibility of the dark areas.

[0005] An object of one embodiment of the present invention is to provide a lighting device, a display device, and a method for controlling a lighting device, which are capable of reducing the temperature of the lighting device while maintaining visibility. [Means for solving the problem]

[0006] In order to solve the above problems, an illumination device according to one embodiment of the present invention comprises a backlight having a plurality of lighting areas, a backlight driver that drives the backlight, and a control unit, wherein the control unit executes an acquisition process to acquire luminance information corresponding to the luminance of each lighting area, a derivation process to derive usage information indicating the usage degree of the lighting area based on the luminance information for each lighting area, a detection process to detect lighting areas having usage information corresponding to a high usage range equal to or higher than a predetermined usage degree, and an adjustment process to control the backlight driver to reduce the luminance of one or more lighting areas detected in the detection process. [Effects of the Invention]

[0007] According to one aspect of the present invention, it is possible to achieve both a reduction in the temperature of the lighting device and maintenance of visibility. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a block diagram illustrating a configuration of a display device according to a first embodiment of the present invention. [Figure 2] 3 is a flowchart illustrating a control method for the lighting device according to the first embodiment of the present invention. [Figure 3] FIG. 3 is a flowchart illustrating details of the derivation process shown in FIG. 2. [Figure 4] 10 is a graph showing the relationship between brightness and usage. [Figure 5] FIG. 3 is a flow diagram showing details of the detection process and adjustment process shown in FIG. 2. [Figure 6] 10 is a graph showing an example of the relationship between usage and brightness. [Figure 7] FIG. 10 is a diagram illustrating an example of temporal changes in usage for each lighting area. [Figure 8] 3 is a diagram showing the image displayed on the display panel and the luminance distribution of the backlight in correspondence with each other. FIG. [Figure 9] 3 is a diagram showing the image displayed on the display panel and the luminance distribution of the backlight in correspondence with each other. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Embodiment 1] An embodiment of the present invention will be described in detail below. Fig. 1 is a block diagram showing the configuration of a display device 10 according to embodiment 1 of the present invention. Embodiment 1 of the present invention will be described in detail below with reference to Fig. 1.

[0010] The display device 10 includes a display panel 11, a backlight 12, a driving unit 13, a video signal processing unit 14, a storage unit 15, and a control unit 16. Of these, at least a part of the display device 10, for example, the backlight 12, the driving unit 13, the video signal processing unit 14, the storage unit 15, and the control unit 16, function as a lighting device.

[0011] The display panel 11 is, for example, a liquid crystal display panel, and has a display area A0 in which a plurality of pixels P are arranged. The display area A0 has a plurality of partial areas Ai corresponding to a plurality of lighting areas Bi, which will be described later.

[0012] The backlight 12 is composed of, for example, a plurality of LEDs (Light Emitting Diodes) and illuminates and lights up the display panel 11. The backlight 12 has a plurality of lighting areas Bi. The lighting areas Bi correspond to the partial areas Ai and light up the partial areas Ai. The lighting areas Bi of the display panel 11 each have one or more LEDs and the brightness can be controlled independently of each other. The brightness of the lighting areas Bi may be uniform or may have a brightness distribution. The brightness distribution may correspond, for example, to the display state of the partial areas Ai.

[0013] The driver 13 drives the display panel 11 and the backlight 12. The driver 13 includes a display panel driver 13a that drives the display panel 11 and a backlight driver 13b that drives the backlight 12.

[0014] The video signal processor 14 processes the video signal IS and outputs it to the driver 13. The video signal processor 14 may generate an average gradation level (hereinafter also referred to as "APLi"; APL: Average Picture Level) in the partial region Ai and a gradation histogram from the video signal IS. APLi means the average gradation in the partial region Ai. The gradation histogram means the intensity distribution of gradation in the partial region Ai.

[0015] The storage unit 15 stores various parameters (for example, a predetermined degree of use, a predetermined second degree of use) which will be described later.

[0016] The control unit 16 controls the drive unit 13 and the video signal processing unit 14. Details of this will be described later.

[0017] 2 is a flow diagram illustrating a control method S10 for the lighting device (backlight 12) according to embodiment 1 of the present invention. The control method S10 for the lighting device includes an acquisition process S11 (acquisition of brightness information), a derivation process S12 (derivation of usage information), a detection process S13 (detection of high-usage areas), and an adjustment process S14 (adjustment of brightness).

[0018] The acquisition process S11, derivation process S12, detection process S13, and adjustment process S14 may be repeatedly executed. This repetition may be periodic. This period may be, for example, one second, and the acquisition process S11, derivation process S12, detection process S13, and adjustment process S14 may be executed every second.

[0019] Note that some of the acquisition process S11, derivation process S12, detection process S13, and adjustment process S14 may be repeated more than others. For example, the derivation process S12 may be repeatedly executed.

[0020] (1) Acquisition process S11 In acquisition process S11, control unit 16 acquires luminance information corresponding to the luminance duty(i) of each lighting area Bi. The luminance information is information corresponding to the luminance duty(i) of lighting area Bi, for example, the gradation and average gradation level (APLi) of the video signal IS in the partial area Ai corresponding to lighting area Bi. The luminance information may be any of the luminance, average luminance, and maximum luminance of lighting area Bi, and the current of lighting area Bi (i.e., LED).

[0021] (2) In the derivation process S12, the control unit 16 derives, for each lighting area Bi, usage information indicating the usage ST(i) of the lighting area Bi based on the luminance information.

[0022] Fig. 3 is a flow diagram showing details of the derivation process S12 shown in Fig. 2. As shown in Fig. 3, in the derivation process S12, the control unit 16 increases or decreases the usage level ST(i) represented by the usage level information based on the brightness information (steps S121 to S125). Here, the usage level ST(i) increases or decreases within the range of 0, +1, and -0.5, but may also be an appropriate real number.

[0023] As shown below, the usage level ST(i) is increased or decreased within the range of a predetermined usage level UST(i) and a predetermined second usage level LST(i). Note that the initial value of the usage level ST(i) may be set to the predetermined second usage level LST(i).

[0024] In the derivation process S12, if the brightness information corresponds to a high brightness range equal to or greater than a predetermined second brightness Sduty(i), the control unit 16 increases the usage ST(i) represented by the usage information (steps S121 and S122). However, the usage ST(i) has an upper limit (predetermined second usage) UST(i), and when the usage ST(i) reaches the predetermined usage UST(i), further increase of the usage ST(i) is stopped. As the high brightness range, the predetermined second brightness Sduty(i) may be set to, for example, 1.1 times 50% of the maximum (maximum brightness) of the brightness range represented by the brightness information. This means that if the maximum brightness is 2000 [nit], the predetermined second brightness Sduty(i) is set to approximately 1100 [nit].

[0025] In the derivation process S12, if the brightness information corresponds to a low brightness range equal to or lower than a predetermined first brightness Tduty(i), the control unit 16 reduces the usage ST(i) represented by the usage information (steps S123 and S124). However, the usage ST(i) has a lower limit (a predetermined second usage) LST(i), and when the usage ST(i) reaches the predetermined second usage LST(i), further reduction of the usage ST(i) is stopped. As the low brightness range, the predetermined first brightness Tduty(i) may be set to, for example, 0.9 times 50% of the maximum brightness. This means that if the maximum brightness is 2000 [nit], the predetermined first brightness Tduty(i) is set to approximately 900 [nit].

[0026] In the derivation process S12, if the brightness information corresponds to an intermediate brightness range between a predetermined first brightness Tduty and a predetermined second brightness Sduty, the control unit 16 does not change the usage level ST(i) represented by the usage level information (steps S123, S125).

[0027] In the above, the usage level ST(i) is increased or decreased based on the luminance duty. However, as will be described later, the lighting area Bi is ultimately controlled by the luminance GSP(i) determined based on the usage level ST(i). For this reason, when the luminance duty(i) and the luminance GSP(i) do not correspond to each other, it is preferable that the usage level ST(i) be increased or decreased based on the luminance GSP(i). For this reason, it is preferable to convert the luminance GSP(i) to the luminance duty(i) so that the usage level ST(i) can be increased or decreased based on the luminance GSP(i).

[0028] FIG. 4 is a graph showing the relationship between luminance duty(i) and usage level ST(i). As described above, when luminance duty(i) is equal to or greater than a predetermined second luminance Sduty, usage level ST(i) is increased. When luminance duty(i) is equal to or less than a predetermined first luminance Tduty, usage level ST(i) is decreased. When luminance duty(i) is higher than the predetermined first luminance Tduty and lower than the predetermined second luminance Sduty, usage level ST(i) does not change. As a result, as described below, the average luminance GSP(i) of the lighting area Bi settles between the predetermined first luminance Tduty and the predetermined second luminance Sduty, which makes it possible to reduce the temperature of the backlight 12 while maintaining visibility.

[0029] (3) In the detection process S13, the control unit 16 detects the lighting area Bi having usage information corresponding to a high usage range equal to or greater than a predetermined usage level UST(i). That is, an example of the high usage range is when brightness information corresponding to the high brightness range continues a predetermined number of times (for example, a predetermined period of time) and the usage level ST(i) reaches the upper limit UST(i). As shown in FIG. 3 (described later), when the brightness information corresponds to the high brightness range (equal to or greater than a predetermined second brightness Sduty(i)), the usage level ST(i) increases and reaches the upper limit (the predetermined usage level UST(i)).

[0030] Fig. 5 is a flow diagram showing the details of the detection process S13 and the adjustment process S14 shown in Fig. 2. The brightness GSP(i) is the brightness of each lighting area Bi, for example, the maximum brightness. Here, the brightness GSP(i) is determined by increasing or decreasing it within the range of ±Cduty, but the brightness GSP(i) may also be determined by other methods.

[0031] As shown below, the brightness GSP(i) is increased or decreased within the range between the lower brightness limit GSPmin and the upper brightness limit GSPmax. Note that the initial value of the brightness GSP(i) may be the upper brightness limit GSPmax.

[0032] In the detection process S13, the control unit 16 detects lighting areas Bi having usage information corresponding to the high usage range where the usage level ST(i) is equal to or greater than a predetermined usage level UST(i) (greater than a predetermined second usage level LST(i)). The control unit 16 then determines to reduce the brightness GSP(i) of one or more of the detected lighting areas Bi (steps S131 and S132). However, the brightness GSP(i) has a lower limit (brightness lower limit) GSPmin, and when the brightness GSP(i) reaches the brightness lower limit GSPmin, any further reduction of the brightness GSP(i) is stopped.

[0033] In the detection process S13, the control unit 16 detects lighting areas Bi having usage information corresponding to a low brightness range in which the usage level ST(i) is equal to or lower than a predetermined second usage level LST(i). The control unit 16 then determines to increase the brightness GSP(i) of one or more of the detected lighting areas Bi (steps S133 and S134). However, the brightness GSP(i) has an upper limit (upper brightness limit) GSPmax, and when the brightness GSP(i) reaches the upper brightness limit GSPmax, any further increase in the brightness GSP(i) is stopped.

[0034] In the detection process S13, the control unit 16 detects lighting areas Bi having usage information corresponding to an intermediate brightness range in which the usage level ST(i) is greater than a predetermined second usage level LST(i) and less than a predetermined usage level UST(i). The control unit 16 does not change the brightness GSP(i) of the one or more detected lighting areas Bi (steps S133 and S135).

[0035] (4) In the adjustment process S14, the control unit 16 controls the backlight driving unit to reduce the luminance GSP(i) of one or more lighting areas Bi detected in the detection process S13.

[0036] In the detection process S13, if the control unit 16 detects a lighting area Bi having usage information corresponding to a high usage range in which the usage level ST(i) is equal to or greater than a predetermined usage level UST(i), the control unit 16 reduces the brightness GSP(i) of the lighting area Bi in the adjustment process S14 (steps S131, S132).

[0037] In the detection process S13, if the same lighting area Bi is repeatedly detected as a lighting area Bi corresponding to the high use range, the control unit 16 gradually reduces the brightness GSP(i) of the lighting area Bi in the adjustment process S14 (steps S131 and S132). In the adjustment process S14, the control unit 16 reduces the brightness GSP(i) of the lighting area Bi to the brightness lower limit GSPmin.

[0038] If the usage information of the lighting area Bi corresponds to a low usage range equal to or less than a predetermined second usage LST(i), the control unit 16 increases the brightness GSP(i) of the lighting area Bi in the adjustment process S14 (steps S133, S134).

[0039] If the usage information of the lighting area Bi corresponds to an intermediate usage range between the low usage range and the high usage range below the predetermined second usage LST(i), the control unit 16 maintains the brightness GSP(i) of the lighting area Bi below the predetermined second usage in the adjustment process S14 (steps S133, S135).

[0040] 6 is a graph showing an example of the relationship between usage ST(i) and brightness GSP(i). Here, it is assumed that the brightness ST(i) of the video signal in the partial area Ai has a brightness distribution of pattern A (hereinafter also referred to as PA) and pattern B (hereinafter also referred to as PB).

[0041] The image of pattern A has a brightness distribution, and its maximum brightness (here, the brightness at the center of the image) is 2000 [nit]. On the other hand, the image of pattern B has a brightness distribution, and its maximum brightness (here, the brightness at the center of the image) is 1600 [nit]. That is, in this example, the brightness information corresponds to the maximum brightness of the lighting area Bi, and does not correspond to the average brightness. Also, the brightness upper limit GSPmax and the predetermined second brightness Sduty are 2000 [nit], and the brightness lower limit GSPmin and the predetermined first brightness Tduty are 50% of the brightness upper limit GSPmax (here, 2000 [nit]).

[0042] 6, patterns A and B are repeated at times t0 to t2, t2 to t3, t3 to t6, t6 to t7, and t7 to t10. Here, an acquisition process S11, a derivation process S12, a detection process S13, and an adjustment process S14 are executed periodically (for example, every second).

[0043] From time t0 to t1, the brightness duty(i) is 2000 [nit], which corresponds to a predetermined second brightness Sduty, so the usage level ST(i) increases (steps S121, S122). At time t1, the usage level ST(i) reaches the predetermined usage level UST(i). In this case, since the usage level ST(i) has not reached the predetermined usage level UST(i) before time t1, the brightness GSP(i) is maintained at the initial brightness upper limit GSPmax, 2000 [nit], and the lighting area Bi emits light at 2000 [nit], which is the maximum brightness of pattern A.

[0044] Between times t1 and t2, the usage level ST(i) reaches a predetermined usage level UST(i), and therefore the brightness GSP(i) is gradually reduced from the upper brightness limit GSPmax (steps S131 and S132). The brightness is gradually reduced from 2000 [nit] to 1000 [nit] in this manner, rather than abruptly, in order to reduce the discomfort felt by the user due to a sudden reduction in brightness. At time t2, the brightness GSP(i) is reduced to the lower brightness limit GSPmin, i.e., 1000 [nit], and the illumination area Bi emits light at 1000 [nit].

[0045] Thus, just before time t2, while pattern A has a maximum brightness of 2000 [nits], lighting area Bi is emitting light at 1000 [nits], half of that. At time t2, the image switches from pattern A to pattern B, and the maximum brightness of the input image (video signal) becomes 1600 [nits]. However, the maximum output brightness of lighting area Bi at this time is 1000 [nits], and during control to reduce the brightness, the brightness of lighting area Bi is reduced to 50%. As a result, the brightness of lighting area Bi becomes 800 [nits], which is 50% of the brightness of the input image (1600 [nits]). Thereafter, from time t2 to t3, the brightness of lighting area Bi is maintained at 800 [nits].

[0046] From time t3 to t4, the luminance duty(i) is 2000 [nit], which corresponds to the predetermined second luminance Sduty, so the usage level ST(i) increases (steps S121, S122). However, until the usage level ST(i) reaches the predetermined usage level UST(i), the luminance GSP(i) gradually increases toward the luminance upper limit GSPmax (steps S133, S134). That is, the luminance of the lit area Bi gradually increases up to 2000 [nit]. In other words, a sudden increase in the luminance of the lit area Bi, which would cause the screen to flicker, is prevented. At time t4, the luminance GSP(i) reaches the luminance upper limit GSPmax.

[0047] From time t4 to t5, the brightness duty(i) is 2000 [nit], which corresponds to the predetermined second brightness Sduty, so the usage level ST(i) increases (steps S121, S122). At time t5, the usage level ST(i) reaches the predetermined usage level UST(i). In this case, since the usage level ST(i) has not reached the predetermined usage level UST(i) before time t5, the brightness GSP(i) is maintained at the initial brightness upper limit GSPmax, 2000 [nit], and the lighting area Bi emits light at 2000 [nit], which is the maximum brightness of pattern A.

[0048] Between times t5 and t6, the usage level ST(i) reaches a predetermined usage level UST(i), so the brightness GSP(i) decreases stepwise from the upper brightness limit GSPmax (steps S131 and S132). At time t6, the brightness GSP(i) decreases to the lower brightness limit GSPmin, i.e., 1000 [nit], and the lighting area Bi emits light at 1000 [nit].

[0049] After that, the process repeats from time t2 to time t6, so a detailed description will be omitted.

[0050] In graph GR2 of FIG. 6, patterns A and B are repeated at times t0 to t2, t2 to t31, t31 to t41, t41 to t51, and t51 to t51.

[0051] The time t1 to t2 is the same as in graph GR1, so the explanation will be omitted.

[0052] From time t2 to t31, the luminance duty(i) is 800 [nit], which corresponds to a low luminance range equal to or lower than the predetermined first luminance Tduty, so the usage level ST(i) decreases (steps S123, S124). However, the period from time t2 to t31 is shorter than the period from time t2 to t3, and at time t31, the usage level ST(i) has not yet reached the predetermined second usage level LST(i).

[0053] In this case, from time t31 to time t41, the level of use ST(i) is greater than the predetermined second level of use LST(i) and less than the predetermined level of use UST(i), so the brightness GSP(i) does not change (steps S133, S135). That is, the brightness of the illuminated area Bi is maintained at 1000 [nit].

[0054] Thereafter, from time t41 to time t51, the brightness duty(i) is 800 [nit], which corresponds to a low brightness range equal to or lower than the predetermined first brightness Tduty, so the usage level ST(i) decreases again (steps S123, S124). Here, it is assumed that the usage level ST(i) reaches the predetermined usage level UST(i) at time t51.

[0055] In this case, from time t51 onwards, the luminance GSP(i) increases, reaches the upper luminance limit GSPmax, and decreases to the lower luminance limit GSPmin, as shown in the graph GR1 from time t3 to t6. As this has already been described, details of this will be omitted.

[0056] As described above, when the usage level ST(i) reaches a predetermined usage level UST(i), whether or not the usage level TST(i) is reached, and ultimately the change in the brightness GSP(i), will differ depending on the period during which the brightness duty(i) subsequently corresponds to the low brightness range or the number of times.

[0057] 7 is a diagram showing an example of temporal changes in usage ST(i) for each lighting area Bi. The lighting areas Bi are represented as areas (1) to (16). Here, an acquisition process S11, a derivation process S12, a detection process S13, and an adjustment process S14 are executed periodically (for example, every second).

[0058] At times 0 to 30 seconds, 30 to 40 seconds, 40 to 50 seconds, and 50 to 60 seconds, the lighting area Bi has the luminance duties of patterns P1 to P4. In patterns P1 to P4, areas (1) to (16) represented in white and black correspond to a high luminance range equal to or greater than a predetermined second luminance Sduty(i) and a low luminance range equal to or less than a predetermined first luminance Tduty(i).

[0059] As shown in the GA of FIG. 7, from 0 to 30 seconds, in areas (1) to (3), (5) to (7), and (9) to (11), the usage level ST(i) increases and reaches a predetermined usage level UST(i). Here, the upper limit UST(i) of the usage level ST(i) is set to 30. In the GA of FIG. 7, at 30 seconds in pattern P1, for example, the usage level ST(i) in areas (1) to (3) reaches the upper limit UST(i) (=30). Therefore, at 30 seconds, control is initiated to lower the upper limit of the brightness from 2000 [nit] to 1000 [nit], and this control continues until 60 seconds. As a result, in patterns P2 to P4, the usage level ST(i) does not change in the lit areas, and the usage level ST(i) is reduced in the unlit areas.

[0060] Thereafter, from 30 to 40 seconds, 40 to 50 seconds, and 50 to 60 seconds, the lighting area Bi has the luminance duty of patterns P2 to P4. As a result, as shown by GB in Fig. 7, the results are different in areas (1) to (3), (5) to (7), and (9) to (11) where the predetermined usage level UST(i) is reached. That is, in areas (1) and (5), the usage level ST(i) has returned to the predetermined first luminance Tduty (here, 0), but in areas (2), (3), (6), (7), and (9) to (11), the usage level ST(i) has not returned to the predetermined first luminance Tduty (here, 0).

[0061] For example, as shown in the GA of FIG. 7, the usage level ST(i) of area (1) reaches the upper limit UST(i) (=30) at the 30-second point in pattern P1, and then decreases to zero in patterns P2 to P4. Meanwhile, as shown in the GA of FIG. 7, the usage level ST(i) of areas (2) and (3) reaches the upper limit UST(i) (=30) at the 30-second point, just like area (1). Therefore, in the subsequent high-intensity pattern P2, the usage level ST(i) does not change. Then, in patterns P3 to P4, the usage level ST(i) of areas (2) and (3) remains at 10, which is reduced by 20 from 30, and does not become zero. Similarly, the usage level ST(i) of areas (6) and (7) remains at 10, which is reduced by 20 from 30.

[0062] Ideally, when the usage rate ST(i) in all lighting areas Bi returns to the predetermined first brightness Tduty, increasing the brightness GSP(i) of the lighting area Bi is thought to contribute to lowering the temperature of the backlight 12.

[0063] 7, the lighting state and further the usage state (usage ST(i)) of the lighting areas Bi differ depending on the lighting area Bi. Therefore, if the luminance GSP(i) of the lighting areas Bi is increased when the usage ST(i) of all the lighting areas Bi returns to the predetermined first luminance Tduty, the luminance of the lighting areas Bi with low usage ST(i) will decrease, and the luminance of the entire backlight 12 will decrease.

[0064] In this regard, by determining the usage level ST(i) and brightness GSP(i) for each lighting area Bi, it is possible to achieve both a low temperature for the backlight 12 and brightness (visibility). That is, the control unit 16 sets the usage level ST(i) for each lighting area Bi. The control unit 16 stores in the memory unit 15 the lighting area Bi whose usage level ST(i) has reached a predetermined usage level UST(i), and starts reducing the brightness GSP(i) of that lighting area Bi. On the other hand, when the usage level ST(i) reaches a predetermined second usage level LST(i), the control unit 16 restores the brightness GSP(i) from the reduced state.

[0065] As described above, in embodiment 1, the lighting device includes a backlight 12 having a plurality of lighting areas Bi, a backlight driving unit 13b that drives the backlight 12, and a control unit 16. The control unit 16 executes an acquisition process (step S11) that acquires brightness information corresponding to the brightness of each lighting area Bi, a derivation process (step S12) that derives usage information representing the usage level ST(i) of the lighting area Bi based on the brightness information for each lighting area Bi, a detection process (step S13) that detects lighting areas Bi having usage information corresponding to a high usage range equal to or greater than a predetermined usage level UST(i), and an adjustment process (step S14) that controls the backlight driving unit 13b to reduce the brightness GSP(i) of one or more lighting areas Bi detected in the detection process.

[0066] As a result, the lighting device according to the first embodiment can reduce the temperature of the backlight 12 while maintaining visibility by reducing the detected luminance GSP(i) of the lighting area Bi.

[0067] [Embodiment 2] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0068] A display device according to a second embodiment of the present invention will be described in detail below. The configuration of a display device 10 according to the second embodiment can be shown in Fig. 1, similar to that of the first embodiment. Therefore, the second embodiment of the present invention will be described in detail with reference to Fig. 1.

[0069] 8 is a diagram showing the images Fa-Fc displayed on the display panel 11 and the luminance Pa-Pc of the backlight 12 in correspondence with each other. The images Fa-Fc all show flowers and leaves. The flowers and leaves are bright, and the spaces between the flowers and leaves are dark. In other words, the images Fa-Fc are bright overall, but some areas are dark.

[0070] The image Fa and the luminance Pa of the backlight 12 correspond to the brightness of the original image. That is, the luminance Pa of the backlight 12 is bright in areas (3) to (5), (7) to (9), (11) to (13), (15), and (16), and is slightly dark in areas (1), (2), (6), (10), and (14).

[0071] On the other hand, for the images Fb and Fc and the luminances Pb and Pc, the luminance of the backlight 12 is adjusted for the image Fa and the luminance Pa.

[0072] In the image Fb, the luminance Pb of the backlight 12 is adjusted to slightly reduce the luminance in the areas (7), (8), (11), (12), (15), and (16).

[0073] On the other hand, in the image Fc, the luminance Pc of the backlight 12 is adjusted to reduce the luminance of the entire areas (1) to (16). That is, areas (3) to (5), (7) to (9), (11) to (13), (15), and (16) are slightly darker, and areas (1), (2), (6), (10), and (14) are even darker.

[0074] In this way, in an image that includes both bright and dark areas, adjusting the brightness GSP(i) of some of the lit areas Bi may cause the bright areas to become darker, which could disrupt the brightness balance of the entire image.

[0075] That is, if it is detected in the detection process S13 that the usage information of a plurality of lighting areas Bi that exceeds the reference number (or reference ratio) corresponds to a high usage range equal to or greater than a predetermined usage UST(i), the control unit 16 can reduce the brightness GSP(i) of the plurality of lighting areas Bi of the backlight 12 in the adjustment process S14. As a result, the brightness GSP(i) of the entire image is reduced, thereby maintaining the balance of the image. The reference number (or reference ratio) can be set, for example, in the range of 30% to 100% of the number of lighting areas Bi, e.g., 40%.

[0076] [Embodiment 3] If the brightness duty(i) of the lighting area Bi remains in an intermediate brightness range between a low brightness range below a predetermined first brightness Tduty(i) and a high usage range above a predetermined second brightness Sduty(i) for a predetermined period of time or more, the control unit 16 may set the usage level ST(i) represented by the usage level information to the low usage range.

[0077] That is, the control unit 16 may set the usage level ST(i) to a low usage range equal to or lower than the usage level ST(i) based on the temporal change in the brightness of the backlight 12. For example, the control unit 16 sets the usage level ST(i) to a predetermined second usage level LST(i) (resetting the usage level, i.e., initializing). This will be described in detail below.

[0078] 9 is a diagram showing the images Fd and Fe displayed on the display panel 11 in relation to the luminance distributions Pd and Pe of the backlight 12. The images Fd and Fe are displayed in sequence. The image Fd is dark overall, with some bright areas. On the other hand, the image Fe is slightly bright overall, with some dark areas.

[0079] In this way, when an image Fe that is generally slightly bright is displayed after an image Fd that is at least partially bright, the usage level ST(i) in some partial areas Ai tends to remain at or above the predetermined usage level UST(i), and as a result, the brightness GSP(i) tends to remain at the brightness lower limit GSPmin.

[0080] In particular, when the image Fd is displayed again after the images Fd and Fe have been displayed, the brightness duty(i) remains in the high brightness range equal to or greater than the predetermined second brightness Sduty(i), so the brightness GSP(i) is likely to decrease when the image Fd is displayed for the second time.

[0081] That is, in the image Fd, in regions (1), (7), and (8), the brightness GSP(i) corresponds to a high brightness range equal to or greater than the predetermined second brightness Sduty(i), so the usage level ST(i) increases. In the image Fe, in regions (1), (7), and (8), the brightness duty corresponds to an intermediate brightness range between the predetermined first brightness Tduty and the predetermined second brightness Sduty, so the usage level ST(i) does not change, and the usage level ST(i) that increased in the image Fd is maintained. When the image Fd is displayed again, the usage level ST(i), which increased in the initial image Fd, increases again, increasing the likelihood that it will reach the predetermined second brightness Sduty.

[0082] In this way, in an image Fe that is slightly bright overall, the usage level ST(i) does not increase in many lit areas Bi, so when an image Fd that is at least partially bright and an image Fe that is slightly bright overall are displayed alternately, the usage level ST(i) is more likely to reach the specified second brightness Sduty in many lit areas Bi.

[0083] Therefore, if the brightness GSP(i) of the lighting area Bi remains in an intermediate brightness range between the low usage range where the usage level ST(i) is low and the high usage range for a predetermined period of time or longer, the control unit 16 sets the usage level ST(i) represented by the usage level information to the low usage range where the usage level ST(i) is low (the usage level ST(i) is set to the predetermined second usage level LST(i)). As a result, it is possible to reduce the possibility that the usage level ST(i) will reach the high brightness range where the usage level Sduty(i) is equal to or higher than the predetermined second brightness Sduty(i) and the brightness GSP(i) will decrease. The predetermined period of time may be, for example, in the range of 60 to 300 seconds, and may be 120 seconds as an example. The predetermined period of time may be determined by the number of repetitions of the acquisition process S11 to the adjustment process S14.

[0084] (Variation 1) If it is detected in the detection process S13 that the usage information of the plurality of lighting areas Bi corresponds to the high usage range, the control unit 16 may, in the adjustment process S14, set the brightness GSP(i) of the plurality of lighting areas Bi so that as the brightness GSP(i) of the lighting area Bi increases, the number of lighting areas Bi having the brightness GSP(i) decreases, thereby enabling efficient use of power.

[0085] That is, the final brightness of multiple lighting areas Bi may be determined not only based on the determined brightness GSP(i) but also based on the proportion of lighting areas Bi that have that brightness GSP(i). For example, lighting areas Bi that have a brightness GSP(i) of the brightness upper limit GSPmax (100% brightness) may be limited to 30% of the lighting area Bi, and lighting areas Bi that have a brightness GSP(i) of 90% of the brightness upper limit GSPmax (90% brightness) may be limited to 40% of the lighting area Bi. If there are many lighting areas Bi with 100% brightness, setting all of those lighting areas Bi to 100% brightness will increase power consumption, making it difficult to effectively utilize power.

[0086] [Variation 2] The brightness GSP(i) of the lighting area Bi has a brightness upper limit GSPmax, and if the usage information of the lighting area Bi continues to correspond to a high usage range equal to or greater than a predetermined usage UST(i) for a predetermined period of time or longer, the control unit 16 may reduce the brightness upper limit GSPmax (steps S133, S134) and, in the adjustment process S14, adjust the brightness GSP(i) of the lighting area Bi to a range equal to or less than the reduced brightness upper limit GSPmax.

[0087] If a state corresponding to the high use range continues for a predetermined time or more, the upper limit (upper brightness limit GSPmax) of the brightness GSP(i) of the lighting area Bi is reduced, thereby further reducing the temperature of the backlight 12. The predetermined time can be set, for example, in the range of 60 seconds to 300 seconds, as an example, to 20 seconds. The predetermined time may be determined by the number of repetitions of the processes from the acquisition process S11 to the adjustment process S14, instead of the time.

[0088] [Variation 3] In the detection process S13, if a lighting area Bi having usage information corresponding to a high usage range (e.g., a predetermined usage UST(i)) is detected, the control unit 16 may reduce the brightness GSP(i) of one or more lighting areas and shift the level of the low brightness range (e.g., a predetermined second brightness Tduty(i)) in the direction of a higher brightness duty.

[0089] That is, in addition to reducing the brightness GSP(i), the predetermined first brightness Tduty(i) may be increased. In the first embodiment, as described above, when the brightness duty(i) and the brightness GSP(i) do not correspond to each other, it is preferable that the usage ST(i) be determined based on the brightness GSP(i). That is, by reducing the brightness GSP(i), the brightness GSP(i) is more likely to fall into the low brightness range. On the other hand, by increasing the predetermined first brightness Tduty(i), the brightness duty(i) is more likely to fall into the low brightness range. In either case, the usage ST(i) is more likely to decrease, and the brightness GSP(i) is more likely to return to its original state. By performing both of these, the usage ST(i) is more likely to decrease, and the brightness GSP(i) is more likely to return to its original state.

[0090] [Software implementation example] The functions of the display device 10 (hereinafter referred to as the "device") can be realized by a program that causes a computer to function as the device, and a program that causes a computer to function as each control block (particularly the control unit 16) of the device.

[0091] In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The control device and storage device execute the program, thereby realizing the functions described in each of the above embodiments.

[0092] The program may be non-transitory and may be recorded on one or more computer-readable recording media. The recording media may or may not be included in the device. In the latter case, the program may be supplied to the device via any wired or wireless transmission medium.

[0093] Furthermore, some or all of the functions of the control blocks can be realized by logic circuits. For example, an integrated circuit in which a logic circuit that functions as each of the control blocks is formed is also included in the scope of the present invention. In addition, the functions of the control blocks can also be realized by, for example, a quantum computer.

[0094] 〔summary〕 The lighting device according to aspect 1 includes a backlight having a plurality of lighting areas, a backlight driving unit that drives the backlight, and a control unit, and the control unit executes an acquisition process to acquire luminance information corresponding to the luminance of each lighting area, a derivation process to derive usage information indicating the usage degree of the lighting area based on the luminance information for each lighting area, a detection process to detect lighting areas having usage information corresponding to a high usage range equal to or higher than a predetermined usage degree, and an adjustment process to control the backlight driving unit to reduce the luminance of one or more lighting areas detected in the detection process.

[0095] A lighting device according to aspect 2 is the lighting device according to aspect 1, wherein the control unit, in the derivation process, When the brightness information corresponds to a low brightness range equal to or lower than a predetermined first brightness, the usage indicated by the usage information is reduced.

[0096] In the lighting device of aspect 3, in aspect 1 or 2, the control unit increases the usage level represented by the usage level information when, in the derivation process, the brightness information corresponds to a high brightness range equal to or greater than a predetermined second brightness.

[0097] The lighting device according to aspect 4 is any one of aspects 1 to 3, wherein in the derivation process, the control unit does not change the usage level represented by the usage level information if the brightness information corresponds to an intermediate brightness range between a predetermined first brightness and a predetermined second brightness.

[0098] A lighting device according to aspect 5 is any of aspects 1 to 4, wherein if the same lighted area is repeatedly detected in the detection process, the control unit reduces the luminance of the lighted area in a stepwise manner in the adjustment process.

[0099] A lighting device according to a sixth aspect is the lighting device of the fifth aspect, wherein the control unit reduces the luminance of the lighted area to a lower luminance limit in the adjustment process.

[0100] In the lighting device according to aspect 7, in any of aspects 1 to 6, when the usage information of the lighting area corresponds to a low usage range below a predetermined usage level, the control unit increases the brightness of the lighting area in the adjustment process.

[0101] In the lighting device of aspect 8, in any of aspects 1 to 7, when the brightness of the lighting area has a brightness upper limit and the usage information of the lighting area corresponds to the high usage range, the control unit reduces the brightness upper limit and, in the adjustment process, adjusts the brightness of the lighting area within a range equal to or less than the reduced brightness upper limit.

[0102] In the lighting device of aspect 9, in aspect 7, when the detection process detects a lighting area having usage information corresponding to the high usage range, the control unit reduces the brightness of the one or more lighting areas and shifts the level of the low brightness range toward higher brightness.

[0103] In the lighting device of aspect 10, in any of aspects 1 to 9, when the usage information of the lighting area corresponds to an intermediate usage range between a low usage range below a predetermined second usage level and the high usage range, the control unit maintains the brightness of the lighting area in the adjustment process.

[0104] In the lighting device of aspect 11, in any of aspects 1 to 10, if the brightness of the lit area continues to correspond to an intermediate brightness range between a low brightness range below a predetermined first brightness and a high brightness range above a predetermined second brightness for a predetermined period of time or more, the control unit sets the usage represented by the usage information to the low usage range.

[0105] In the lighting device of aspect 12, in any of aspects 1 to 11, if the detection process detects that the usage information corresponds to the high usage range in multiple lighting areas that exceed a reference number, the control unit reduces the brightness of the multiple lighting areas of the backlight in the adjustment process.

[0106] In the lighting device of aspect 13, in any of aspects 1 to 12, if the detection process detects that the usage information of multiple lighting areas corresponds to the high usage range, the control unit, in the adjustment process, sets the brightness of the multiple lighting areas so that as the brightness of a lighting area increases, the number of lighting areas having that brightness decreases.

[0107] A lighting device according to a fourteenth aspect includes the lighting device according to any one of the first to thirteenth aspects.

[0108] A control method for a lighting device according to aspect 15 is a control method for a lighting device that includes a backlight having a plurality of lighting areas and a backlight driving unit that drives the backlight, and includes an acquisition process that acquires brightness information corresponding to the brightness of each lighting area, a derivation process that derives usage information indicating the usage degree of the lighting area based on the brightness information for each lighting area, a detection process that detects lighting areas that have usage information corresponding to a high usage range that is equal to or higher than a predetermined usage degree, and an adjustment process that controls the backlight driving unit to reduce the brightness of one or more lighting areas detected in the detection process.

[0109] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment. [Explanation of symbols]

[0110] 10 Display device 11 Display panel 12 Backlight 13 Drive unit 13a Display panel drive unit 13b Backlight driver 14 Video signal processing section 15 Storage section 16 Control Unit Ai partial area Bi lighting area S10 Control Method S11 Acquisition process S12 Derivation processing S13 Detection process S14 Adjustment process

Claims

1. a backlight having a plurality of lighting areas; a backlight driving unit that drives the backlight; a control unit, The control unit an acquisition process for acquiring luminance information corresponding to the luminance of each lighting area; a derivation process for deriving usage information representing a usage degree of each lighting area based on the luminance information; a detection process for detecting a lighting area having usage information corresponding to a high usage range equal to or higher than a predetermined usage; and performing an adjustment process to control the backlight driving unit to reduce the luminance of one or more lighting areas detected in the detection process.

2. The control unit, in the derivation process, The lighting device according to claim 1 , wherein when the brightness information corresponds to a low brightness range equal to or less than a predetermined first brightness, the usage level indicated by the usage level information is reduced.

3. The control unit, in the derivation process, The lighting device according to claim 1 , wherein when the brightness information corresponds to a high brightness range equal to or greater than a predetermined second brightness, the usage level indicated by the usage level information is increased.

4. The control unit, in the derivation process, The lighting device according to claim 1 , wherein the usage level represented by the usage level information is not changed when the brightness information corresponds to an intermediate brightness range between a predetermined first brightness and a predetermined second brightness.

5. In the detection process, if the same lighting area is repeatedly detected, The lighting device according to claim 1 , wherein the control unit reduces the luminance of the lighted area in a stepwise manner in the adjustment process.

6. The lighting device according to claim 5 , wherein the control unit reduces the luminance of the lighted area to a lower luminance limit in the adjustment process.

7. When the usage information of the lighting area corresponds to a low usage range equal to or lower than a predetermined second usage level, The lighting device according to claim 1 , wherein the control unit increases the luminance of the lighting area in the adjustment process.

8. the brightness of the lighting area has a brightness upper limit, If the usage information of the lighting area corresponds to the high usage range, The control unit Reducing the upper brightness limit, The lighting device according to claim 1 , wherein the adjustment process adjusts the brightness of the lighting area within a range equal to or less than the reduced upper brightness limit.

9. In the detection process, if a lighting area having usage information corresponding to the high usage range is detected, The lighting device according to claim 2 , wherein the control unit reduces the luminance of the one or more lighting areas and shifts the level of the low luminance range toward a higher luminance level.

10. When the usage information of the lighting area corresponds to an intermediate usage range between a low usage range equal to or lower than a predetermined second usage level and the high usage range, The lighting device according to claim 1 , wherein the control unit maintains the luminance of the lighting area in the adjustment process.

11. When the state in which the luminance of the lighting area corresponds to an intermediate luminance range between a low luminance range equal to or lower than a predetermined first luminance and a high luminance range equal to or higher than a predetermined second luminance continues for a predetermined time or more, The lighting device according to claim 1 , wherein the control unit sets the usage level indicated by the usage level information to the low usage range.

12. In the detection process, if it is detected that the usage information corresponds to the high usage range in a plurality of lighting areas exceeding a reference number, The lighting device according to claim 1 , wherein the control unit reduces the luminance of the plurality of lighting areas of the backlight in the adjustment process.

13. In the detection process, if it is detected that the usage information of the plurality of lighting areas corresponds to the high usage range, In the adjustment process, the control unit The lighting device according to claim 1 , wherein the luminance of the plurality of lighting areas is set so that as the luminance of a lighting area increases, the number of lighting areas having that luminance decreases.

14. A display device comprising the lighting device according to claim 1.

15. A method for controlling a lighting device including a backlight having a plurality of lighting areas and a backlight driver that drives the backlight, comprising: an acquisition process for acquiring luminance information corresponding to the luminance of each lighting area; a derivation process for deriving usage information representing a usage degree of each lighting area based on the luminance information; a detection process for detecting a lighting area having usage information corresponding to a high usage range equal to or higher than a predetermined usage; an adjustment process of controlling the backlight driver to reduce the luminance of one or more lighting areas detected in the detection process.

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