JP2007163557A - Display device, and method for controlling luminance thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device with which unnecessary operation for adjusting and controlling screen luminance is prevented even when surrounding illumination on the display device temporarily varies due to interior illumination, shining in of external light, image contents and so on when an image is viewed in dark surroundings, and a method for controlling luminance thereof. <P>SOLUTION: An image display device, with which an image is displayed by inputting an image signal thereto, and brightness of the screen is adjusted corresponding to the surrounding illumination, is equipped with: surrounding illumination acquiring means 1, 8 to acquire surrounding illumination per period of sampling; a computing means 1 to compute a backlight luminance set value based on the acquired surrounding illumination; and a backlight luminance control means 2 to control the backlight luminance based on the computed backlight luminance set value. A malfunction in adjusting and controlling of screen luminance caused by fluctuation in a screen luminance level while appreciating the image in dark surroundings is prevented with the surrounding illumination acquiring means by changing sensitivity corresponding to the backlight luminance set value computed in the period of sampling immediately before. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a display device and a brightness adjustment method thereof, and particularly a display device capable of preventing malfunction of screen brightness adjustment control due to a change in screen brightness level when viewing an image in a dark state. And a luminance adjustment method thereof.

  The optimal brightness of the screen when viewing images on a display such as a television screen changes depending on the ambient brightness. For example, when the surroundings are dark, it is easier to see if the screen is dark. Also, when viewing in a bright room, it is difficult to see unless the screen is brightened.

In order to cope with such a situation, conventionally, the brightness of the screen is automatically adjusted according to the ambient brightness. The prior art disclosed in Patent Document 1 is an example. According to Patent Document 1, the characteristics as shown in FIG. 10 with respect to the ambient illuminance, that is, the screen is bright when the ambient illuminance is high (bright), and the screen is dark when the ambient illuminance is low (dark). Is described. In this prior art, ambient illuminance is detected by a surrounding light receiving unit (ambient illuminance sensor), and the brightness of the screen is adjusted based on the relationship between the detected amount and FIG.
JP-A-6-308991

  However, the above prior art simply detects a change in ambient illuminance and reflects it in the backlight luminance. For example, when viewing an image in a dark room, it becomes brighter instantaneously (for example, some light In response to the change in illuminance when the light in the room flickers and temporarily becomes dark while watching the image in a bright room. Operation (malfunction) that does not require screen brightness adjustment control will occur. In addition, ambient ambient light may include light coming from its own screen. For example, when an image that makes the entire screen whitish for a few seconds such as explosion or flame, the brightness level of the screen increases during that time, and as a result, the ambient illuminance sensor detects this. Then, in response to this, the backlight luminance increases so as to temporarily blink. In particular, when the illuminance level of ambient ambient light is low, the influence of the screen brightness becomes large, and malfunctions are likely to occur in the screen brightness adjustment control.

  FIG. 11 shows the state of this malfunction. In FIG. 11, a dotted line abcb shows a change in ambient illuminance. A solid line de-fe shows a change in screen brightness. Here, the symbols a, b, c, d, e, and f are the same as those shown in FIG. A portion indicated by a dotted line c indicates a state where the ambient illuminance is temporarily brightened from a dark state. In response to this change in ambient illuminance, the screen changes from a dark state of e to a bright state of f and returns to a dark state of e. Since the ambient illuminance c is temporary, if the screen brightness reacts to this change like f, the screen becomes instantaneously difficult to see. The brightness of the screen should not react to such a temporary change in ambient illuminance.

  In view of the above problems, the object of the present invention is to watch a video in a dark surroundings, even if the ambient illuminance of the display device changes temporarily due to room lighting, outside light lighting, video content, etc. It is an object of the present invention to provide a display device capable of preventing unnecessary operation of screen brightness adjustment control and a brightness adjustment method thereof.

The gist of the invention according to claim 1 of the present invention is to provide a video display device capable of inputting a video signal to display a video and adjusting the brightness of the screen according to the ambient illuminance. Ambient illuminance acquisition means to be acquired, a calculation means for calculating a backlight luminance setting value based on the ambient illuminance acquired by the ambient illuminance acquisition means, and a backlight based on the backlight luminance setting value calculated by the calculation means Backlight brightness control means for controlling the brightness of the light is provided, and the ambient illuminance acquisition means resides in a display device characterized in that sensitivity can be changed.
The gist of the invention according to claim 2 of the present invention is characterized in that the ambient illuminance acquisition means changes the sensitivity according to a backlight luminance setting value calculated in the immediately preceding sampling period. 1. The display device according to 1 is present.
The gist of the invention according to claim 3 of the present invention is that the larger the backlight luminance setting value calculated in the immediately preceding sampling period is, the more the amount of change in the backlight luminance setting value updated for each sampling is increased. 3. The display device according to claim 2, wherein the sensitivity is changed.
The gist of the invention according to claim 4 of the present invention is to change the sensitivity by decreasing the sampling interval for updating the backlight luminance setting value as the backlight luminance setting value calculated in the immediately preceding sampling period is larger. The display device according to claim 2 is provided.
The gist of the invention according to claim 5 of the present invention is that the ambient illuminance acquisition means changes the sensitivity so as not to detect a change in ambient illuminance when the level of the video luminance signal exceeds a predetermined value. The display device according to claim 1 is provided.
The gist of the invention according to claim 6 of the present invention is that the ambient luminance is not more than a predetermined value and the average value of the luminance levels of the display video signal in one field or one frame of the video signal, or the screen 6. The display according to claim 5, wherein the sensitivity is changed so that a change in ambient illuminance is not detected when a ratio of a screen having a luminance level equal to or higher than a threshold value temporarily exceeds a predetermined threshold value. Exists in the device.
Further, the gist of the invention according to claim 7 of the present invention is that the calculating means has an optimum backlight luminance setting value corresponding to the acquired ambient illuminance and a backlight luminance setting value calculated in the immediately preceding sampling period. When different, the amount of change of the backlight luminance setting value corresponding to the backlight luminance setting value calculated in the immediately preceding sampling period is obtained, and the luminance setting calculated in the immediately preceding sampling period is determined 7. The display device according to claim 1, further comprising a backlight luminance setting value updating unit that adds a value to obtain a new backlight luminance setting value. 8.
The gist of the invention according to claim 8 of the present invention is that the computing means has an optimum backlight luminance setting value corresponding to the acquired ambient illuminance and a backlight luminance setting value calculated in the immediately preceding sampling period. When different, a backlight luminance setting value updating means for obtaining a sampling interval corresponding to the backlight luminance setting value calculated in the immediately preceding sampling period and updating a new backlight luminance setting value at the obtained sampling interval. It exists in the display apparatus as described in any one of Claims 1 thru | or 6 characterized by the above-mentioned.
The gist of the invention according to claim 9 of the present invention is to sample the ambient illuminance in a video display device that can input a video signal to display a video and adjust the screen brightness according to the ambient illuminance. Ambient illuminance acquisition means acquired every period, a calculation means for calculating a video luminance signal correction value based on the ambient illuminance acquired by the ambient illuminance acquisition means, and the video luminance signal correction value calculated by the calculation means There is provided a video luminance signal control means for controlling the luminance of the video signal based on the display device, wherein the ambient illuminance acquisition has a sensitivity changeable.
The gist of the invention according to claim 10 of the present invention is that the video signal can be displayed by inputting a video signal and the brightness of the screen can be adjusted according to the ambient illuminance. Ambient illuminance is acquired for each sampling period, a backlight luminance setting value is calculated based on the acquired ambient illuminance, a backlight luminance is controlled based on the calculated backlight luminance setting value, and the ambient illuminance is calculated. The present invention resides in a luminance adjustment method characterized in that the sensitivity at the time of obtaining can be changed.
The gist of the invention according to claim 11 of the present invention is that the sensitivity is changed according to a backlight brightness setting value calculated in the immediately preceding sampling period. Exist.
The gist of the invention according to claim 12 of the present invention is that the larger the backlight luminance setting value calculated in the immediately preceding sampling period is, the more the amount of change in the backlight luminance setting value updated for each sampling is increased. 12. The brightness adjustment method according to claim 11, wherein the sensitivity is changed.
The gist of the invention according to claim 13 of the present invention is to change the sensitivity by decreasing the sampling interval for updating the backlight luminance setting value as the backlight luminance setting value calculated in the immediately preceding sampling period is larger. The brightness adjustment method according to claim 11, wherein:
The gist of the invention according to claim 14 of the present invention is that the sensitivity is changed so as not to detect a change in ambient illuminance when the level of the video luminance signal exceeds a predetermined value. 10. The brightness adjustment method according to 10.
The gist of the invention according to claim 15 of the present invention is that the ambient luminance is not more than a predetermined value and the average value of the luminance levels of the display video signal in one field or one frame of the video signal, or the screen 15. The luminance according to claim 14, wherein the sensitivity is changed so that a change in ambient illuminance is not detected when a ratio of a screen having a luminance level equal to or higher than a threshold value temporarily exceeds a predetermined threshold value. It exists in the adjustment method.
The gist of the invention according to claim 16 of the present invention is that when the optimal backlight luminance setting value corresponding to the acquired ambient illuminance differs from the backlight luminance setting value calculated in the immediately preceding sampling period, The amount of change in the backlight luminance setting value corresponding to the backlight luminance setting value calculated during the sampling period is obtained, and the obtained amount of change is added to the luminance setting value calculated during the immediately preceding sampling period. The brightness adjustment method according to any one of claims 10 to 15, wherein a new backlight brightness setting value is set.
The gist of the invention according to claim 17 of the present invention is that when the optimum backlight luminance setting value corresponding to the acquired ambient illuminance differs from the backlight luminance setting value calculated in the immediately preceding sampling period, A backlight luminance setting value updating unit is provided that obtains a sampling interval corresponding to the backlight luminance setting value calculated in a sampling period and updates a new backlight luminance setting value at the obtained sampling interval. The brightness adjustment method according to any one of claims 10 to 15.
The gist of the invention according to claim 18 of the present invention is that, in the method of adjusting the brightness of the video display device, the video signal can be input and displayed, and the brightness of the screen can be adjusted according to the ambient illuminance. Ambient illuminance obtaining means for obtaining ambient illuminance for each sampling period, a computing means for computing a video luminance signal correction value based on the ambient illuminance obtained by the ambient illuminance obtaining means, and the video brightness computed by the computing means The luminance adjustment method includes a video luminance signal control means for controlling the luminance of the video signal based on the signal correction value, and the ambient illuminance acquisition can change the sensitivity.

  According to the present invention, when viewing an image of a display device in a dark environment, even if the ambient illuminance of the display device changes temporarily due to room lighting, external light lighting, video content, etc., the screen brightness It is possible to prevent unnecessary operation of the height adjustment control and view the video in an optimum state.

  Next, the best mode for carrying out the present invention will be specifically described with reference to the drawings.

(First embodiment)
FIG. 1 is a control configuration diagram of a display device according to the present embodiment, and shows an example of a liquid crystal display. Note that although an example of a liquid crystal display is shown as a display device in this embodiment mode, the present invention is not limited to a liquid crystal display as a display device, but is applied to a CRT display, a plasma display, and other general display devices that can adjust luminance. can do.

  In FIG. 1, reference numeral 1 denotes an arithmetic circuit composed of a microcomputer (hereinafter referred to as a microcomputer), which comprises a central processing unit CPU, storage means (ROM, RAM) and the like. The ROM of the storage means stores programs necessary for carrying out the present invention and other various programs, and the RAM of the storage means temporarily stores calculation results and values during the calculation.

  Reference numeral 2 denotes a backlight control unit which controls the luminance of the backlight based on the backlight luminance setting value input from the arithmetic circuit 1.

  A backlight driving unit 3 receives a control signal from the backlight control unit, and is supplied with power corresponding to the backlight luminance setting value.

  Reference numeral 4 denotes a backlight, and a light source such as a cold cathode tube or an LED is used.

  Reference numeral 5 denotes a video display unit using a liquid crystal display, which is disposed in front of the backlight and displays a video based on a video signal.

  Reference numeral 8 denotes an OPC (ambient illuminance sensor), which is usually provided in a cabinet portion on the front surface of the display device in order to detect the ambient illuminance from the viewer side. The OPC 8 is basically used as a function for automatically setting the optimum screen brightness in ambient light. Especially when the ambient illuminance due to ambient light is low, the OPC 8 rotates from the screen of the liquid crystal display 5. Including ambient light, it will be detected as ambient illuminance. The OPC 8 receives ambient ambient light and light that has entered from the screen of the liquid crystal display 5 and outputs a signal proportional to the ambient illuminance to the arithmetic circuit 1. The arithmetic circuit 1 inputs a value proportional to the ambient illuminance from the OPC 8, calculates a backlight luminance setting value, and outputs it to the backlight control unit 2.

  Reference numeral 6 denotes a video signal input unit to which a video signal received and demodulated by the television receiver is input. Reference numeral 7 denotes a video signal processing unit, which is composed of an IP conversion / RGB processor or the like, and generates interlaced and progressive conversion and R, G, and B signals.

  Thus, the video signal is processed into a signal suitable for video display by the video signal processing unit 7, and the video is displayed on the video display unit 5.

  Reference numeral 9 denotes a screen brightness adjusting means by the viewer, and the screen brightness can be arbitrarily set according to the viewer's preference. A screen brightness correction coefficient α is input from the screen brightness adjusting means 9 to the arithmetic circuit 1, and a backlight brightness setting value corrected by the screen brightness correction coefficient α is output from the arithmetic circuit 1. The screen brightness adjusting means 9 may be configured to be able to directly input a numerical value corresponding to the screen brightness correction coefficient α, or to adjust according to the screen brightness adjustment menu on the screen. The brightness correction coefficient α may be output to the computing means 1. Alternatively, the screen brightness correction coefficient α may be output to the computing means 1 by operating a button on a remote controller (not shown).

FIG. 2 shows an outline of the operation of the present embodiment. In FIG. 2, the horizontal axis represents time, and the vertical axis represents illuminance or luminance. The thick solid line indicates the ambient illuminance. Also, the thick dashed line indicates the backlight luminance setting value. A thin solid line is a change in the video luminance level, and shows the amount of screen light that wraps around the OPC 8. Further, a chain line a thin one-dot luminance of images shows the threshold Y _c affecting the environmental light, the ambient illumination sensor senses this exceeds the threshold value Y _c.

  When the backlight brightness adjustment control is performed according to the ambient light, the backlight brightness should not react to a change in the brightness level of the screen image. However, when the illuminance level of the ambient ambient light is low, the relative influence of the screen luminance level on the entire ambient illuminance level increases, and it becomes easy to react to changes in the luminance level of the screen.

  In the prior art, the screen brightness adjustment control (performed by backlight brightness adjustment control in the case of a liquid crystal display device) linearly increases / decreases the backlight brightness setting value in proportion to the ambient illuminance, and the sensitivity of the OPC 8 to the ambient illuminance. In this embodiment, the sensitivity of the OPC 8 is changed according to the backlight luminance setting value (or luminance suppression value described later) calculated in the immediately preceding sampling period, and the backlight luminance setting value is optimized. It is made to correspond to the backlight luminance setting value. By changing the sensitivity of the OPC 8 in this manner, when the ambient illuminance is high (the surrounding is bright), the OPC 8 responds sensitively to the ambient illuminance, and when the ambient illuminance is low (the surrounding is dark), the response is dull. It becomes like this. In this case, even if the ambient illuminance temporarily increases, the backlight brightness setting value hardly increases, and malfunction is prevented. Here, the sensitivity of the OPC 8 is not only the sensitivity of the OPC 8 itself but also the total (equivalent) sensitivity including how the ambient illuminance is acquired in the arithmetic circuit 1 from the output of the OPC 8. To tell. In other words, it is the sensitivity as the ambient illuminance acquisition means for acquiring the ambient illuminance for each sampling period.

The operation of the first embodiment according to the present invention will be described in detail with reference to FIG. The ambient illuminance decreases from L ₁ to L ₂ at time t ₁ , and the backlight luminance setting value decreases in response to this from the Y ₁ to the optimal backlight luminance setting value Y ₂ corresponding to L ₂ . At this time, since the backlight luminance setting value when close to ambient illuminance is higher L ₁ has a large value corresponding to L _1, the sensitivity of OPC8 is in a high state. Accordingly, the change in the backlight luminance setting value is sharply reduced. Since the backlight luminance setting value and the small value according to the ambient illuminance is closer to a low L _2, change in the backlight luminance setting value sensitivity of OPC8 gradually becomes dull becomes gentle. Backlight luminance setting value reaches the optimum backlight luminance setting value Y2 at time t _2.

Further, if the change in ambient illuminance due to the sneak in the screen image exceeds the minimum level (threshold Y _c ) detected by the OPC 8 during the time t _{3 to} t ₄ , the OPC 8 detects the change in ambient illuminance. However, at this time, the backlight brightness setting value calculated in the immediately preceding sampling period is a small value, so the sensitivity of the OPC 8 is in a low state and does not immediately respond to the change in ambient illuminance due to the influence of the screen image, and is shown in the figure. It rises dull from _{Y 2} of _{t 3} to _{Y 3} of _{t 4} as. Also, t ₄ after, but below the minimum level detected by the OPC8 (threshold Y _c), is in a low state the sensitivity of OPC Again, not responsive to changes in the ambient illumination as shown in FIG. , T ₄ slowly changes from Y _{3 at} t ₄ to Y ₂ at t ₅ .

  As shown in FIG. 2, even if the OPC 8 detects the sneak light of the screen image when the ambient illuminance is low, the screen brightness level hardly changes.

  In the present embodiment, the sensitivity of the OPC 8 is changed according to the backlight luminance setting value (or luminance suppression value described later), not the ambient illuminance itself. This is because when the sensitivity of the OPC 8 is changed in accordance with the ambient illuminance, it reacts quickly to a temporarily bright image, and when the image returns to the original dark state, the screen brightness is quite good. This is because a problem of not returning will occur. For example, if the sensitivity of the OPC 8 is changed in accordance with the ambient illuminance, when the image is viewed in a dark environment and the screen suddenly becomes bright in an explosion scene or the like, the sensitivity of the OPC 8 depends on the brightness of the screen. Increases and the backlight brightness setting value suddenly increases. On the other hand, when the explosion scene ends and it becomes dark again, the sensitivity of the OPC 8 becomes low, and it does not easily return. Therefore, in the present embodiment, in order to avoid this problem, it is changed according to the backlight luminance setting value.

  As a method of changing the sensitivity of the OPC 8 in the present embodiment, a method of reducing the change width of the backlight luminance setting value to be calculated next as the previous backlight luminance setting value is smaller (Example 1), or the backlight. There is a method (Example 2) in which the update timing of the backlight luminance setting value is delayed (the sampling interval is increased) as the light luminance setting value is smaller.

  The sensitivity of the OPC 8 is determined by how to determine the change width of the backlight brightness setting value to be changed in a certain time or the update timing of the backlight brightness setting value. That is, the sensitivity of the OPC 8 is equivalently reduced if the change range of the backlight luminance setting value that is changed for a certain time is reduced, and the sensitivity of the OPC 8 is equivalent even if the timing of updating the luminance level (sampling interval) is long. It becomes low.

  Next, as the present embodiment, the sensitivity of the OPC 8 is changed by a method (Example 1) in which the change width of the backlight luminance setting value to be calculated next is reduced as the previous backlight luminance setting value is smaller. The operation at this time will be described with reference to FIG.

FIG. 3 is a diagram conceptually illustrating a control operation according to the first embodiment. In FIG. 3, the horizontal axis represents time, and the vertical axis represents the backlight luminance setting value (left side) and the luminance suppression value (right side). Time points t ₁ , t ₂ , t ₃ ,..., The dotted lines at the time points indicate the separation of the sampling period.

  Here, the luminance suppression value is a value indicating how much the luminance is suppressed with respect to the maximum luminance that the backlight can emit, and when the brightest luminance is set as the luminance that can be set for the backlight. 0% (luminance suppression value = 0% in the sense that the luminance is not suppressed at all), 100% (luminance suppression in the sense that the luminance is suppressed by 100%) when the backlight luminance is 0 (cd / m2) Value = 100%). The luminance suppression value is calculated by the arithmetic circuit 1 so as to change between a brighter limit value (0%) and a darker limit value (for example, 85%) corresponding to the ambient illuminance.

  On the other hand, the backlight luminance setting value has an inverse relationship between the luminance suppression value and the magnitude, and is 100% * α when the luminance suppression value = 0%, and 0% when the luminance suppression value = 100%. ing. Here, α is a screen brightness correction coefficient, which is a coefficient value for correcting the screen brightness input from the screen brightness adjusting means 9 when the screen is brightened or darkened according to the preference of the viewer. That is, the backlight brightness setting value is obtained by correcting with the screen brightness correction coefficient α based on the calculated brightness suppression value, and corresponds to the actual backlight brightness.

Further, the luminance suppression value is updated every time t ₁ , t ₂ , t ₃ ,..., And the amount of change in the luminance suppression value for each sampling is referred to as the luminance suppression value change amount.

In FIG. 3, when the screen brightness correction coefficient α is set to 1, the backlight brightness setting values 100%, y ₁ %, y ₂ %,... Y ₆ % are multiplied by the screen brightness correction coefficient α. The values 100% * α, y ₁ % * α, y ₂ % * α,... Y ₆ % * α are taken as the backlight brightness setting values on the left vertical axis. The backlight luminance setting value on the left vertical axis is the backlight luminance setting value corrected by the screen brightness correction coefficient α from the screen brightness adjusting means 9. Then, in order to change the backlight luminance setting value according to the backlight luminance setting value calculated in the immediately preceding sampling period, luminance suppression value change amounts Δy ₁ , Δy ₂ , Δy ₃ . For example, Δy ₁ = F (0), Δy ₂ = F (100−y ₁ ), Δy ₃ = F (100−y ₂ )... (Where the function F is 100−y It is a decreasing function with respect to _n , where n is an integer).

  Further, in FIG. 3, the luminance suppression value starts changing from 0% and changes to the dark limit value, but the luminance suppression value does not necessarily change to the dark limit value. Also, it does not necessarily change to the bright limit value. It goes without saying that the target luminance suppression value to be changed may be a value between the brighter limit value and the darker limit value. In this case, an optimum luminance suppression value corresponding to the ambient illuminance is obtained and changes with the target as the target. There is a possibility that the ambient illuminance changes every sampling, and therefore the optimum luminance suppression value also changes every sampling, and the luminance suppression value changes so as to follow it.

  In FIG. 3, the change width of the luminance suppression value for each sampling is drawn relatively large. Actually, the minimum change width of the luminance suppression value is 1 for the change width from 0% to 100%. The sampling interval is as small as about 1/1000 with respect to the time for the luminance suppression value to change from 0% to 100%. Therefore, the change in the luminance suppression value is a substantially smooth change. Further, if the change of the luminance suppression value for each sampling is interpolated by linear interpolation or the like, it can be changed more smoothly. A characteristic line (backlight luminance setting value) indicated by a thick dashed line shown in FIG. 2 corresponds to a characteristic line (backlight luminance setting value) changing in a staircase pattern shown in FIG. However, the characteristic of FIG. 2 corresponds to the characteristic in which the change is made smoothly as described above with respect to FIG. 3 and there is almost no step-like change.

As described above, the magnitudes of the luminance suppression value change amounts Δy ₁ , Δy ₂ , Δy ₃ ,... Are the luminance suppression values 0, 100-y ₁ , 100-y ₂ , 100-y ₃ ,. In relation to..., The amount of change Δy ₁ , Δy ₂ , Δy ₃ ,. The amount of change in luminance suppression value Δy ₁ , Δy ₂ , Δy ₃ ,... Is changed by Δy _{n + 1} = F ₁ (100−y _n ), and the function F _{1 is set} to 100−y _n . Decrease function may be determined by selecting this function. For example, an inversely proportional relationship can be used, but the present invention is not limited to this. Since the function F ₁ is Aru Elect decreasing function of 100-y _n, it can be as sensitivity equivalently OPC8 the brightness suppression value increases is deteriorated. Since the screen brightness correction coefficient alpha = backlight luminance setting value y _n and brightness suppression value at 1 (100-y _n) corresponds uniquely, the brightness suppression value change amount in FIG. 3, for example Δy _n + ₁ = F ₁ has obtained as _{(100-y n), Δy} n + 1 = F 1 with the backlight luminance setting value _{y n} when the screen brightness correction coefficient alpha = 1 'calculated as _{(y n)} May be. However, in this case, the function _{F 1} 'and increasing function of _{y n.}

  Next, the backlight brightness adjustment operation of the display device according to the first embodiment will be described with reference to the control flowchart of FIG. Before entering this operation process, the optimum luminance suppression value for the ambient illuminance is determined in advance and stored in the storage means (ROM) 1 in the arithmetic circuit 1 as the ambient illuminance-optimum luminance suppression value correspondence table TB1. Here, the correspondence relationship between the ambient illuminance and the optimum luminance suppression value stored as the table TB1 can be obtained by an investigation such as collecting experimental data from a large number of examinees in advance and obtaining an average value thereof. it can. Alternatively, if statistical data already exists, it can be used. Further, the program processing shown in the control flowchart of FIG. 4 is executed by the microcomputer constituting the arithmetic circuit 1.

In the present embodiment, for each sampling, a previously stored table is referenced or the luminance suppression value change amount is obtained by calculation corresponding to the luminance suppression value calculated in the immediately preceding sampling period. Then, for each sampling period, control is performed to add the obtained luminance suppression value change amount to the previous luminance suppression value to obtain a new luminance suppression value. When the luminance suppression value change amount is obtained by referring to a previously stored table, the luminance suppression value change amount corresponding to the luminance suppression value may be stored in the storage unit as the table TB2 (or The amount of change in the backlight luminance setting value with respect to the backlight luminance setting value when the screen brightness correction coefficient α = 1 may be stored. The amount of change in the luminance suppression value corresponding to the luminance suppression value is related to the sensitivity of the OPC 8 with respect to the ambient illuminance, and the sensitivity characteristic of the OPC 8 can be determined depending on how this correspondence is set. Further, when calculated by determining the brightness suppression value change amount can be determined by the function F ₁ or a function F _{1, '.} The function F ₁ or the function F ₁ ′ is also related to the sensitivity of the OPC 8 with respect to the ambient illuminance, and the sensitivity characteristic of the OPC 8 can be determined depending on what function is used. Specifically, the correspondence relationship between the luminance suppression value and the luminance suppression value change amount stored in the table TB2 is updated to the luminance suppression value calculated in a certain sampling period and the sampling period immediately thereafter, as shown in FIG. It is the a relationship between the brightness suppression value change amount [Delta] y _n.

  First, in step S1, ambient illuminance is acquired from a signal taken into the arithmetic circuit 1 from the OPC 8 at a predetermined sample timing.

  Next, the process proceeds to step S2. In step S2, the optimum brightness suppression value corresponding to the ambient illuminance is obtained by referring to the table TB1 stored in advance in the storage means (ROM), and compared with the brightness suppression value calculated in the immediately preceding sampling period. It is determined whether or not the luminance suppression value is the optimum luminance suppression value.

  If the current luminance suppression value is the optimal luminance suppression value (in the case of YES), the process returns to step S1 and the processing is continued.

  If it is determined in step S2 that the luminance suppression value is not the optimal luminance suppression value (in the case of NO), the process proceeds to step S3, and the current luminance suppression value is too small with respect to the optimal luminance suppression value, or It is judged whether it is too large. In this determination, an optimum luminance suppression value corresponding to the ambient illuminance is obtained by referring to the table TB1 stored in advance in the storage means (ROM), and compared with the luminance suppression value calculated by the arithmetic circuit 1 in the immediately preceding sampling period. Is done. This comparison can also be executed as a process in step S2 instead of being executed again in step S3.

  If it is determined in step S3 that the luminance suppression value is too small, the process proceeds to step S4. In step S4, it is checked whether or not the current luminance suppression value is not a limit value in the dark direction. If it is determined in step S4 that the limit value in the dark direction has been reached (in the case of NO), the luminance suppression value is not increased any more (or cannot be increased any more), and the process returns to step S1 to perform the processing. continue.

If it is determined in step S4 that the limit value in the dark direction has not been reached (in the case of YES), in step S5, corresponding to the luminance suppression value calculated in the immediately preceding sampling period, as described above. as referring to the table TB2 stored in advance in the storage unit or, alternatively by calculation using the function F ₁ obtains the brightness suppression value variation.

  Next, it progresses to step S6 and the new luminance suppression value change amount calculated | required by step S5 is added to a dark direction with respect to a luminance suppression value, and a new luminance suppression value is calculated | required. In step S7, it is checked whether the new luminance suppression value is a limit value in the dark direction. If it is determined that it is not the limit value in the dark direction, the process proceeds to step S14, and the backlight brightness setting value is set based on the new brightness suppression value and the screen brightness correction coefficient α input from the screen brightness adjustment means 9. Update. The new backlight brightness setting value at this time is obtained by correcting the backlight brightness setting value (screen brightness correction coefficient α = 1) obtained based on the new brightness suppression value with the screen brightness correction coefficient α. .

  In step S15, the operation is performed based on the new backlight luminance setting value, and the backlight luminance is controlled. Thereafter, the process returns to step S1 to continue the process.

  If it is determined in step S7 that the limit value is in the dark direction (NO), the luminance suppression value is set to the limit value in the dark direction in step S8. In step S14, the backlight brightness setting value is updated based on the new brightness suppression value and the screen brightness correction coefficient α. Thereafter, the process returns to step S1 to continue the process.

  If it is determined in step S3 that the dark luminance suppression value is too large, the process proceeds to step S9. In step S9, it is checked whether the current luminance suppression value is not a limit value in the bright direction. If it is determined in step S9 that the limit value in the bright direction has been reached (in the case of NO), the luminance suppression value is not further reduced (or cannot be further reduced), and the process returns to step S1 to perform the process. continue.

If it is determined in step S9 that the limit value in the bright direction has not been reached (in the case of YES), in step S10, corresponding to the luminance suppression value calculated in the immediately preceding sampling period, as described above. as referring to the table TB2 stored in advance in the storage unit or, alternatively by calculation using the function F ₁ obtains the brightness suppression value variation.

  Next, it progresses to step S11 and the new luminance suppression value change amount calculated | required by step S10 is added to a bright direction with respect to a luminance suppression value, and a new luminance suppression value is calculated | required. In step S12, it is checked whether the new luminance suppression value is a limit value in the bright direction. If it is determined that it is not the limit value in the bright direction, the process proceeds to step S14, and the backlight brightness setting value is set based on the new brightness suppression value and the screen brightness correction coefficient α input from the screen brightness adjustment means 9. Update. The new backlight brightness setting value at this time is obtained by correcting the backlight brightness setting value (screen brightness correction coefficient α = 1) obtained based on the new brightness suppression value with the screen brightness correction coefficient α. .

  In step S15, the operation is performed based on the new backlight luminance setting value, and the backlight luminance is controlled. Thereafter, the process returns to step S1 to continue the process.

  If it is determined in step S12 that the limit value is in the bright direction (NO), the brightness suppression value is set to the limit value in the bright direction in step S13. In step S14, the backlight brightness setting value is updated based on the new brightness suppression value and the screen brightness correction coefficient α. Thereafter, the process returns to step S1 to continue the process.

  As is clear from the above description, according to the present embodiment, when watching a movie or the like in a dark environment, even if the brightness of the image changes only for a short time in an explosion scene or the like, The brightness can be hardly changed. On the other hand, when the ambient illuminance is surely changed, the brightness of the screen can be changed to the optimum screen brightness corresponding to the ambient illuminance.

  Next, as the present embodiment, when the sensitivity of the OPC 8 is changed by a method (Example 2) that delays the update timing of the backlight luminance setting value (increases the sampling interval) as the backlight luminance setting value decreases. Will be described with reference to FIG.

FIG. 5 is a diagram conceptually illustrating the control operation according to the second embodiment.
In FIG. 5, the horizontal axis represents time, and the vertical axis represents the backlight luminance setting value (left side) and the luminance suppression value (right side). Time points t ₁ , t ₂ , t ₃ ,..., The dotted lines at the time points indicate the separation of the sampling period.

  The second embodiment shown in FIG. 5 is different from the first embodiment in that the first embodiment changes the change width of the luminance suppression value change amount according to the luminance suppression value. The difference is that the interval is changed according to the luminance suppression value.

  That is, as shown in FIG. 5, the sampling interval for updating the luminance suppression value is shortened when the luminance suppression value is decreased, and the sampling interval for updating the luminance suppression value is increased when the luminance suppression value is increased. Therefore, when the ambient illuminance decreases and the luminance suppression value increases accordingly, the update interval of the luminance suppression value becomes longer, so that the sensitivity of the OPC 8 can be equivalently deteriorated.

Sampling intervals Δt ₁ , Δt ₂ , Δt ₃ ,... Are related to luminance suppression values 0, 100-y ₁ , 100-y ₂ , 100-y ₃ ,... Calculated in the immediately preceding sampling period. However, as the luminance suppression value increases, it increases correspondingly. If the sampling intervals Δt ₁ , Δt ₂ , Δt ₃ ,... Are changed corresponding to the luminance suppression value, Δt _{n + 1} = F ₂ (100−y _n ), F ₂ is 100−. an increase function of y _n, determined by the choice of this function. For example, it can be a direct proportional relationship, but is not limited thereto. Since the function F ₂ is Aru Elect increasing function, the sampling interval becomes longer as the brightness suppression value increases, it as sensitivity equivalently OPC8 deteriorates.

Incidentally, as in Example 1 Similarly, since the backlight luminance setting value y _n and brightness suppression value 100-y _n when the screen brightness correction coefficient alpha = 1 corresponds uniquely, the sampling interval in FIG. 5 For example, it is calculated as Δt _{n + 1} = F ₂ (100−y _n ), but may be calculated as Δt _{n + 1} = F ₂ ′ (y _n ). However, in this case, the function _{F 2} 'a decreasing function of _{y n.}

  Next, the backlight luminance adjustment operation of the display device according to the second embodiment will be described with reference to the control flowchart of FIG. Before entering this operation process, the optimum luminance suppression value for the ambient illuminance is determined in advance and stored in the storage means (ROM) 1 in the arithmetic circuit 1 as the ambient illuminance-optimum luminance suppression value correspondence table TB1. Further, the program processing shown in the control flowchart of FIG. 6 is executed by a microcomputer constituting the arithmetic circuit 1.

In the present embodiment, the sampling interval corresponding to the luminance suppression value calculated in the immediately preceding sampling period is obtained by referring to a table stored in advance or by calculation at each update timing, and luminance suppression is performed at each sampling interval. Control to update the value. When referring to a previously stored table, the sampling interval corresponding to the luminance suppression value may be stored in the storage means as the table TB3 (or when the screen brightness correction coefficient α = 1). The sampling interval for the backlight brightness setting value may be stored). The sampling interval corresponding to the luminance suppression value is related to the sensitivity of the OPC 8 with respect to the ambient illuminance, and the sensitivity characteristic of the OPC 8 can be determined depending on how this correspondence is set. Further, when calculated by determining the sampling interval can be determined by the function F ₂ or a function F _{2, '.} The function F ₂ or the function F ₂ ′ is also related to the sensitivity of the OPC 8 with respect to the ambient illuminance, and the sensitivity characteristic of the OPC 8 can be determined depending on what function is used. Specifically, as shown in FIG. 5, the correspondence relationship between the luminance suppression value stored in the table TB3 and the sampling interval is the relationship between the luminance suppression value calculated during a certain sampling period and the length of the sampling period immediately thereafter. become.

First, in step S21, the sampling interval corresponding to the brightness suppression value calculated in the sampling period immediately before, refer to the table TB3 stored in advance in the storage unit, or obtained by calculation using the function F _2.

  Next, it progresses to step S22 and waits only for the time according to the sampling interval calculated | required by step S21.

  Next, it progresses to step S23 and ambient illuminance is acquired by the signal taken in into the arithmetic circuit 1 from OPC8.

  Next, the process proceeds to step S24. In step S24, an optimum luminance suppression value corresponding to the current luminance suppression value is obtained by referring to the table TB1 stored in advance in the storage means (ROM), and the luminance suppression value calculated by the arithmetic circuit 1 in the immediately preceding sampling period. To determine whether or not the current luminance suppression value is the optimal luminance suppression value.

  If the current luminance suppression value is the optimum luminance suppression value, the process returns to step S21 and the processing is continued.

  If it is determined in step S24 that the value is not an appropriate value (NO), the process proceeds to step S25, where it is determined whether the current luminance suppression value is too small or too large. This determination is performed by referring to the table TB1 stored in advance in the storage means (ROM) to obtain the optimum luminance suppression value corresponding to the ambient illuminance and comparing it with the luminance suppression value calculated in the immediately preceding sampling period. . This comparison can be executed not as a new step in step S25 but as a process in step S24.

  If it is determined in step S25 that the luminance suppression value is too small, the process proceeds to step S26. In step S26, it is checked whether or not the luminance suppression value calculated in the immediately preceding sampling period is a limit value in the dark direction. If it is determined in step S26 that the limit value in the dark direction has been reached (in the case of NO), the luminance suppression value is not increased any more (or cannot be increased any more), and the process returns to step S21 to perform the processing. continue.

If it is determined in step S26 that the dark limit value has not been reached (in the case of YES), a predetermined amount (Δy _a ) corresponding to the luminance suppression value calculated in the immediately preceding sampling period in step S27. Is added in the dark direction.

  Next, in step S28, it is checked whether the new luminance suppression value is not the limit value in the dark direction. If it is determined that the value is not the limit value in the dark direction (in the case of YES), the process proceeds to step S34, and a value obtained by correcting the new luminance suppression value with the screen brightness correction coefficient α input from the screen brightness adjustment means 9 is obtained. Obtain the backlight brightness setting value. The new backlight brightness setting value at this time is obtained by correcting the backlight brightness setting value (screen brightness correction coefficient α = 1) obtained based on the new brightness suppression value with the screen brightness correction coefficient α. .

  In step S35, the operation is performed based on the new backlight luminance setting value, and the backlight luminance is controlled. Thereafter, the process returns to step S21 to continue the processing.

  If it is determined in step S28 that the limit value is in the dark direction (NO), the luminance suppression value is set to the limit value in the dark direction in step S29. Next, proceeding to step S34, a value obtained by correcting the new brightness suppression value with the screen brightness correction coefficient α input from the screen brightness adjusting means 9 is obtained, and the backlight brightness setting value is updated. The new backlight brightness setting value at this time is obtained by correcting the backlight brightness setting value (screen brightness correction coefficient α = 1) obtained based on the new brightness suppression value with the screen brightness correction coefficient α. .

  In step S35, the operation is performed based on the new backlight luminance setting value, and the backlight luminance is controlled. Thereafter, the process returns to step S21 to continue the processing.

  If it is determined in step S25 that the luminance suppression value is too large, the process proceeds to step S30. In step S30, it is checked whether or not the luminance suppression value calculated in the immediately preceding sampling period is a limit value in the bright direction. If it is determined in step S30 that the limit value in the bright direction has been reached (in the case of NO), the luminance suppression value is not further reduced (or cannot be further reduced), and the process returns to step S21 to perform the process. continue.

When it is determined in step S30 that the limit value in the bright direction has not been reached (in the case of YES), a predetermined amount (Δy _a ) corresponding to the luminance suppression value calculated in the immediately preceding sampling period in step S31. Is added in the brighter direction.

  Next, in step S32, it is checked whether the new luminance suppression value is a limit value in the bright direction. If it is determined that it is not the limit value in the bright direction (in the case of YES), the process proceeds to step S34, and a value obtained by correcting the new brightness suppression value with the screen brightness correction coefficient α input from the screen brightness adjustment means 9 is obtained. Obtain the backlight brightness setting value. The new backlight brightness setting value at this time is obtained by correcting the backlight brightness setting value (screen brightness correction coefficient α = 1) obtained based on the new brightness suppression value with the screen brightness correction coefficient α. .

  In step S35, the operation is performed based on the new backlight luminance setting value, and the backlight luminance is controlled. Thereafter, the process returns to step S21 to continue the processing.

  If it is determined in step S32 that the limit value is in the bright direction (in the case of NO), the luminance suppression value is set to the limit value in the bright direction in step S33. Next, proceeding to step S34, a value obtained by correcting the new brightness suppression value with the screen brightness correction coefficient α input from the screen brightness adjusting means 9 is obtained, and the backlight brightness setting value is updated. The new backlight brightness setting value at this time is obtained by correcting the backlight brightness setting value (screen brightness correction coefficient α = 1) obtained based on the new brightness suppression value with the screen brightness correction coefficient α. .

  In step S35, the operation is performed based on the new backlight luminance setting value, and the backlight luminance is controlled. Thereafter, the process returns to step S21 to continue the processing.

  As is clear from the above description, according to the present embodiment, when the ambient illuminance changes only for a short time, the brightness of the screen can be hardly changed. Further, when the ambient illuminance changes with certainty, the brightness of the screen can be changed to the optimum screen brightness corresponding to the ambient illuminance. Therefore, as in the first embodiment, when viewing an image in a dark environment, it is possible to prevent malfunction of screen brightness adjustment control due to a change in screen brightness level.

(Second Embodiment)
FIG. 7 is a control configuration diagram of the display device according to the second embodiment, and shows an example of a liquid crystal display.

  In the first embodiment, the luminance suppression value change amount or the sampling interval is changed according to the luminance suppression value calculated in the immediately preceding sampling period to change the sensitivity of the OPC 8 equivalently. In the embodiment, the luminance suppression value of the backlight is not less than a certain level, and the illuminance level of the ambient light is low enough to affect the OPC 8 by the wraparound from the screen. Stop the OPC8 operation or disable the OPC8 control system while the average value of the luminance level of the display video signal is above a certain value or the screen with the luminance level above the threshold in the screen is above a certain percentage The difference is that the sensitivity of the OPC 8 is equivalently set to 0 by blocking with a switch or the like. In this case, since the operation of the OPC 8 is stopped or the control system of the OPC 8 is shut off and the information on the ambient illuminance is not updated, the luminance suppression value (or luminance setting value) of the backlight is in the hold state.

  As a result, for example, when watching a movie in a dark room, the screen temporarily becomes bright in an explosion scene etc., and the illuminance level of the surrounding ambient light may be temporarily raised, Meanwhile, the ambient illuminance information is not updated by the OPC 8, and the backlight brightness setting value is not updated based on the information.

  Compared with the display device in the first embodiment, in the display device in the second embodiment, the video signal processing unit 22 (in place of the video signal processing unit 7 in the first embodiment) is provided. A video signal luminance level determination circuit 23 is provided, and a video signal luminance level determination signal is output from the video signal luminance level determination circuit 23 to the arithmetic circuit 21.

  The video signal luminance level determination circuit 23 is based on the luminance signal input from the video signal input unit 6, and the average value of the luminance levels of the display video signal in one field or one frame of the video signal or the threshold value in the screen. The ratio of the screen having the above luminance level is obtained, and it is determined whether this value is larger or smaller than a predetermined value (threshold value) set in advance. The luminance level determination signal is output to the arithmetic circuit 21. When the ambient illuminance detected by the OPC 8 is equal to or less than a predetermined value and the value obtained by the video signal luminance level determination circuit 23 temporarily exceeds a predetermined threshold, the arithmetic circuit 1 The backlight brightness setting value output from the arithmetic circuit 1 is held so that the update is not performed.

  The other components having the same reference numerals as those in FIG.

  Next, the backlight luminance adjustment operation of the display device according to the second embodiment will be described with reference to the control flowchart of FIG. Before entering this operation process, the optimum luminance suppression value for the ambient illuminance is determined in advance and stored in the storage means (ROM) 1 in the arithmetic circuit 1 as the ambient illuminance-optimum luminance suppression value correspondence table TB1. Further, the program processing shown in the control flowchart of FIG. 8 is executed by the microcomputer constituting the arithmetic circuit 1.

  In this embodiment, every sampling, it is checked whether or not the luminance level of the display image on the screen affects the ambient illuminance detected by the OPC 8. When the level is influential, it is output from the arithmetic circuit 1 during that time. The backlight brightness setting value is held and the update is not performed.

  First, in step S41, ambient illuminance is obtained from a signal taken into the arithmetic circuit 1 from the OPC 8 at a predetermined sample timing.

  Next, the process proceeds to step S42. In step S42, the video signal luminance level determination circuit 23 determines the average value of the luminance level of the display video signal in one field or one frame of the video signal, or the ratio of screens having a luminance level equal to or higher than the threshold in the screen. The determination result is output from the video signal luminance level determination circuit 23 to the arithmetic circuit 1 as a luminance level determination signal.

  The average value of the luminance level of the display video signal in one field or one frame of the video signal, or the proportion of screens having a luminance level equal to or higher than the threshold value in the screen temporarily exceeds a predetermined threshold value, and is detected by the OPC8. When the ambient illuminance is less than or equal to the predetermined value, the arithmetic circuit 1 determines that the luminance level of the current display image has an influence on the ambient illuminance (YES), and returns the process to step 41. In this case, since no processing is performed on the luminance suppression value, the backlight luminance setting value output from the arithmetic circuit 1 is held during this time.

  If it is determined in step S42 that the brightness level of the current display image does not affect the ambient illuminance (in the case of NO), the process proceeds to step S43. In step S43, an optimum luminance suppression value corresponding to the current luminance suppression value is obtained by referring to the table TB1 stored in advance in the storage means (ROM), and the luminance suppression value calculated by the arithmetic circuit 1 in the immediately preceding sampling period. To determine whether or not the current luminance suppression value is the optimal luminance suppression value.

  If the current luminance suppression value is the optimum luminance suppression value (in the case of YES), the process returns to step S41 and the processing is continued.

  When it is determined in step S43 that the luminance suppression value is not the optimal luminance suppression value (in the case of NO), the process proceeds to step S44, and the current luminance suppression value is too small with respect to the optimal luminance suppression value, or It is judged whether it is too large. This determination is performed by referring to the table TB1 stored in advance in the storage means (ROM) to obtain the optimum luminance suppression value corresponding to the ambient illuminance and comparing it with the luminance suppression value calculated in the immediately preceding sampling period. . This comparison can be executed not as a new step in step S44 but as a process in step S43.

  If it is determined in step S44 that the luminance suppression value is too small, the process proceeds to step S45. In step S45, it is checked whether or not the luminance suppression value calculated in the immediately preceding sampling period is a limit value in the dark direction. If it is determined in step S45 that the limit value in the dark direction has been reached (in the case of NO), the luminance suppression value is not increased any more (or cannot be increased any more), and the process returns to step S41 to perform the processing. continue.

  If it is determined in step S45 that the limit value in the dark direction has not been reached (in the case of YES), a predetermined amount (Δya) corresponding to the luminance suppression value calculated in the immediately preceding sampling period is determined in step S46. Add in dark direction.

  In step S49, the backlight brightness setting value is updated based on the new brightness suppression value and the screen brightness correction coefficient α input from the screen brightness adjusting means 9. The new backlight brightness setting value at this time is obtained by correcting the backlight brightness setting value (screen brightness correction coefficient α = 1) obtained based on the new brightness suppression value with the screen brightness correction coefficient α. .

  In step S50, the operation is performed based on the new backlight luminance setting value, and the backlight luminance is controlled. Thereafter, the process returns to step S41 to continue the processing.

  If it is determined in step S44 that the luminance suppression value is too large, the process proceeds to step S47. In step S47, it is checked whether or not the luminance suppression value calculated in the immediately preceding sampling period is a limit value in the bright direction. If it is determined in step S47 that the limit value in the bright direction has been reached (in the case of NO), the luminance suppression value is not further reduced (or cannot be further reduced), and the process returns to step S41 for processing. continue.

  When it is determined in step S47 that the limit value in the dark direction has not been reached (in the case of YES), a predetermined amount (Δya) corresponding to the luminance suppression value calculated in the immediately preceding sampling period is set in step S48. Add in the bright direction.

  In step S49, the backlight brightness setting value is updated based on the new brightness suppression value and the screen brightness correction coefficient α input from the screen brightness adjusting means 9. The new backlight brightness setting value at this time is obtained by correcting the backlight brightness setting value (screen brightness correction coefficient α = 1) obtained based on the new brightness suppression value with the screen brightness correction coefficient α. .

  In step S50, the operation is performed based on the new backlight luminance setting value, and the backlight luminance is controlled. Thereafter, the process returns to step S41 to continue the processing.

  As is apparent from the above description, according to the present embodiment, even if the luminance of the video displayed on the screen in a state where the ambient illuminance is lower than a predetermined value temporarily exceeds a certain threshold value, luminance suppression during this period is suppressed. You can hold the value to keep the screen brightness from changing. Therefore, as in the first embodiment, when viewing an image in a dark environment, it is possible to prevent malfunction of screen brightness adjustment control due to a change in screen brightness level.

(Third embodiment)
Next, FIG. 9 shows a third embodiment of the display device of the present invention.
The first and second embodiments described above are applied to a liquid crystal display device that adjusts the luminance of the backlight in order to adjust the brightness of the screen, but the present embodiment shown in FIG. The present invention is applied to a display device that adjusts the brightness of a screen by correcting a video luminance signal, such as a CRT display or a plasma display.

  In FIG. 9, reference numeral 31 denotes an arithmetic circuit composed of a microcomputer, which comprises a central processing unit CPU, storage means (ROM, RAM) and the like. The ROM of the storage means stores programs necessary for carrying out the present invention and other various programs, and the RAM of the storage means temporarily stores calculation results and values during the calculation.

  Reference numeral 34 denotes an image display unit such as a CRT display or a plasma display, which displays an image based on the input image signal.

  Reference numeral 35 denotes an OPC that detects ambient ambient light and light that circulates from the screen. Then, the OPC 35 outputs a signal proportional to the ambient illuminance to the arithmetic circuit 31. The arithmetic circuit 31 inputs a value proportional to the ambient illuminance from the OPC 35, calculates a video luminance signal correction value, and outputs it to the video signal processor 33.

  Reference numeral 32 denotes a video signal input unit to which a video signal received and demodulated by the television receiving unit is input. The output signal from the video signal input unit 32 includes a video luminance signal representing the brightness of the video.

  Reference numeral 33 denotes a video signal processing unit, which is composed of an IP conversion / RGB processor or the like, and receives signals from the video signal input unit 32 to generate interlaced and progressive conversion and R, G, B signals. Further, it has a function of inputting the video luminance signal correction value from the arithmetic circuit 31 and correcting the video luminance signal from the video signal input unit 32.

  Thus, the video signal is processed into a signal suitable for video display by the video signal processing unit 33, and the video is displayed on the video display unit 34.

  Reference numeral 36 denotes screen brightness adjusting means operated by the viewer, which is the same as the screen brightness adjusting means 9 of the first and second embodiments. A screen brightness correction coefficient α is input from the screen brightness adjusting means 36 to the arithmetic circuit 31, and a video luminance signal correction value corrected by the screen brightness correction coefficient α is output from the arithmetic circuit 31.

  In the first and second embodiments, the backlight luminance setting value output from the arithmetic circuits 1 and 21 of FIGS. 1 and 7 is input to the backlight control 2 to control the luminance of the backlight. In contrast, the present embodiment is different in that the video luminance signal correction value output from the arithmetic circuit 31 is input to the video signal processing unit 33 to correct the video luminance signal. However, the calculation in the calculation circuit 31 can be performed basically as the same as the first and second embodiments. That is, control is performed according to a control flowchart in which “backlight luminance” in step S14, step S15, step S34, step S35, step S49, and step S50 in the flowcharts of FIGS. 4, 6, and 8 is replaced with “video luminance signal”. can do. Also in this embodiment, the same effects as those of the first and second embodiments can be obtained.

  As mentioned above, although it demonstrated by specific embodiment, this invention is not limited to the said embodiment. For example, in the above embodiment, the ambient brightness-optimum brightness suppression value correspondence table TB1 is stored in advance in the storage means as the optimal brightness setting value corresponding to the ambient illumination, and the backlight brightness setting value is used using the brightness suppression value. The image brightness signal correction value is calculated, but instead of the ambient illuminance-optimum brightness suppression value correspondence table, the ambient illuminance-optimum brightness value correspondence table is stored in advance in the storage means, and the brightness value is used for back-up. The light luminance setting value and the video luminance signal correction value may be calculated. In the present invention, the optimum brightness setting value stored in the storage means as a value for achieving the optimum screen brightness corresponding to the ambient illuminance is not limited to the optimum brightness suppression value or the optimum brightness value. As such, it is only necessary to store a value corresponding to the optimum luminance for which the optimum screen brightness corresponding to the ambient illuminance is obtained from the value stored in the storage means.

  In the above embodiment, the screen brightness correction coefficient α from the screen brightness adjusting means 9 and 36 is input to the arithmetic circuits 1, 21, and 31 for correction. You may make it correct | amend by inputting into the signal processing parts 7 and 33. FIG. Further, the arithmetic circuit 1 can be provided with the function of the luminance level determination circuit 23 for the video signal in the second embodiment. In this case, the luminance signal may be output from the video signal processing unit 22 to the arithmetic circuit 1 so that the arithmetic circuit 1 performs the same processing as the luminance level determination circuit 23 of the video signal.

  Moreover, it goes without saying that the present invention can be implemented by changing the embodiment without departing from the scope of the invention.

  The present invention is not limited to a liquid crystal display, but can be applied to a CRT display, a plasma display, and other displays that can adjust luminance. The present invention can be applied not only to a display device of a television receiver but also to a monitor device of various devices such as a personal computer and a game machine.

It is a figure which shows the control structure of the display apparatus in 1st Embodiment by this invention. It is a figure explaining control operation in a 1st embodiment by the present invention. Example 1 in which the sensitivity of the OPC 8 in the first embodiment according to the present invention is changed by a method of reducing the change width of the backlight luminance setting value to be calculated next as the immediately preceding backlight luminance setting value decreases. FIG. It is a control operation | movement flowchart of Example 1 in 1st Embodiment by this invention. FIG. 10 is an operation explanatory diagram of the first embodiment in which the sensitivity of the OPC 8 is changed by a method of delaying the update timing of the backlight luminance setting value as the backlight luminance setting value is smaller in the first embodiment of the present invention. It is a control operation | movement flowchart of Example 2 in the 1st Embodiment by this invention. It is a figure which shows the control structure of the display apparatus in 2nd Embodiment by this invention. It is a control operation | movement flowchart in 2nd Embodiment by this invention. It is a figure which shows the control structure of the display apparatus in 3rd Embodiment by this invention. It is a figure which shows an example of the characteristic of ambient illuminance and screen luminance of the screen luminance adjustment control by a prior art. It is a figure which shows an example of operation | movement of the screen brightness adjustment control by a prior art.

Explanation of symbols

1, 21, 31, arithmetic circuit 2, backlight controller 3, backlight drive unit 4, backlight 5, 34, video display unit 6, 32, video signal input Units 22, 22, 33 ... Video signal processing unit 8, 35 ... OPC (ambient illuminance sensor)
9 ... Screen brightness adjusting means 23 ... Video signal luminance level determination circuit

Claims (18)

In a video display device that can input a video signal to display a video and adjust the screen brightness according to the ambient illuminance,
Ambient illuminance acquisition means for acquiring ambient illuminance for each sampling period;
A calculation means for calculating a backlight luminance setting value based on the ambient illuminance acquired by the ambient illuminance acquisition means;
Backlight brightness control means for controlling the brightness of the backlight based on the backlight brightness setting value calculated by the calculation means,
The ambient illuminance acquisition means can change sensitivity.   The display device according to claim 1, wherein the ambient illuminance acquisition unit changes the sensitivity according to a backlight luminance setting value calculated in the immediately preceding sampling period.   3. The sensitivity is changed by increasing the amount of change in the backlight luminance setting value updated for each sampling as the backlight luminance setting value calculated in the immediately preceding sampling period is larger. Display device.   3. The display device according to claim 2, wherein the sensitivity is changed by decreasing a sampling interval for updating the backlight luminance setting value as the backlight luminance setting value calculated in the immediately preceding sampling period is larger.   The display device according to claim 1, wherein the ambient illuminance acquisition unit changes the sensitivity so as not to detect a change in ambient illuminance when the level of the video luminance signal exceeds a predetermined value.   The ratio of screens that have an ambient illuminance of a predetermined value or less and that have an average luminance level of a display video signal within one field or frame of the video signal, or a luminance level that is equal to or higher than a threshold value within the screen is temporary The display device according to claim 5, wherein the sensitivity is changed such that a change in ambient illuminance is not detected when a predetermined threshold is exceeded. The computing means is
When the optimal backlight luminance setting value corresponding to the acquired ambient illuminance is different from the backlight luminance setting value calculated in the immediately preceding sampling period,
Obtain the amount of change in the backlight brightness setting value corresponding to the backlight brightness setting value calculated in the immediately preceding sampling period,
2. A backlight luminance setting value updating unit that adds the obtained change amount to the luminance setting value calculated in the immediately preceding sampling period to obtain a new backlight luminance setting value. The display apparatus as described in any one of thru | or 6. The computing means is
When the optimal backlight luminance setting value corresponding to the acquired ambient illuminance is different from the backlight luminance setting value calculated in the immediately preceding sampling period,
A backlight luminance setting value updating unit is provided for obtaining a sampling interval corresponding to the backlight luminance setting value calculated in the immediately preceding sampling period and updating a new backlight luminance setting value at the obtained sampling interval. The display device according to claim 1, wherein: In a video display device that can input a video signal to display a video and adjust the screen brightness according to the ambient illuminance,
Ambient illuminance acquisition means for acquiring ambient illuminance for each sampling period;
A computing means for computing a video luminance signal correction value based on the ambient illuminance acquired by the ambient illuminance acquiring means;
Video luminance signal control means for controlling the luminance of the video signal based on the video luminance signal correction value calculated by the calculating means;
The display device characterized in that the sensitivity can be changed in the ambient illuminance acquisition. In the method of adjusting the brightness of the video display device that can input the video signal to display the video and adjust the screen brightness according to the ambient illuminance,
Acquire ambient illuminance for each sampling period,
Calculate a backlight brightness setting value based on the acquired ambient illuminance,
Control the brightness of the backlight based on the calculated backlight brightness setting value,
A luminance adjustment method characterized in that the sensitivity at the time of obtaining the ambient illuminance can be changed.   The brightness adjustment method according to claim 10, wherein the sensitivity is changed according to a backlight brightness setting value calculated in the immediately preceding sampling period.   12. The sensitivity is changed by increasing the amount of change in the backlight luminance setting value updated for each sampling as the backlight luminance setting value calculated in the immediately preceding sampling period is larger. Brightness adjustment method.   12. The brightness adjustment method according to claim 11, wherein the sensitivity is changed by decreasing a sampling interval for updating the backlight brightness setting value as the backlight brightness setting value calculated in the immediately preceding sampling period is larger. .   The brightness adjustment method according to claim 10, wherein the sensitivity is changed so that a change in ambient illuminance is not detected when the level of the video brightness signal exceeds a predetermined value.   The ratio of screens that have an ambient illuminance equal to or lower than a predetermined value and that have an average luminance level of a display video signal within one field or frame of the video signal or a luminance level that is equal to or higher than a threshold value within the screen is temporary. The brightness adjustment method according to claim 14, wherein the sensitivity is changed so that a change in ambient illuminance is not detected when a predetermined threshold is exceeded. When the optimal backlight luminance setting value corresponding to the acquired ambient illuminance is different from the backlight luminance setting value calculated in the immediately preceding sampling period,
Obtain the amount of change in the backlight brightness setting value corresponding to the backlight brightness setting value calculated in the immediately preceding sampling period,
The obtained change amount is added to the luminance setting value calculated in the immediately preceding sampling period to obtain a new backlight luminance setting value. Brightness adjustment method. When the optimal backlight luminance setting value corresponding to the acquired ambient illuminance is different from the backlight luminance setting value calculated in the immediately preceding sampling period,
A backlight luminance setting value updating unit is provided for obtaining a sampling interval corresponding to the backlight luminance setting value calculated in the immediately preceding sampling period and updating a new backlight luminance setting value at the obtained sampling interval. The brightness adjustment method according to any one of claims 10 to 15, wherein: In the method of adjusting the brightness of the video display device that can input the video signal to display the video and adjust the screen brightness according to the ambient illuminance,
Ambient illuminance acquisition means for acquiring ambient illuminance for each sampling period;
A computing means for computing a video luminance signal correction value based on the ambient illuminance acquired by the ambient illuminance acquiring means;
Video luminance signal control means for controlling the luminance of the video signal based on the video luminance signal correction value calculated by the calculating means;
The brightness adjustment method according to claim 1, wherein the ambient illuminance acquisition can change sensitivity.

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