Abstract:
Provided is a backlight device wherein when the drive duty and the drive current are controlled according to a motion, the image quality is improved by preventing flicker caused by the change of the drive waveform. A light-emitting unit ( 121 ) comprises a plurality of light-emitting areas. A motion amount detecting unit ( 131 ) detects the motion amount of an image in each of a plurality of motion areas each corresponding to at least one or more light-emitting areas. A drive condition specifying unit specifies a drive condition including the duty and pulse height value of a drive pulse for causing each of the plurality of light-emitting areas to emit light, on the basis of the detected motion amount. A drive unit drives each of the plurality of light-emitting areas according to the specified drive condition. The drive condition specifying unit adjusts the drive condition such that the drive condition temporally smoothly changes.

Description:
TECHNICAL FIELD 
     The present invention relates a backlight apparatus and a display apparatus using the backlight apparatus. 
     BACKGROUND ART 
     A non-self-luminous display apparatus typified by a liquid-crystal display apparatus has a backlight apparatus (to be also simply referred to as a “backlight” hereinafter) on a backside thereof. The display apparatus displays an image through a light modulating section that adjusts an amount of reflection or an amount of transmission of light radiated from the backlight depending on an image signal. In the display apparatus, in order to reduce blurring of a moving image appearing in a hold type driving display apparatus, a light source is intermittently lighted in synchronism with scanning of an image. 
     In general, in order to perform the intermittent lighting, a scheme that causes an entire light emitting area of the backlight to light at a predetermined timing (to be generally referred to as “backlight blink”) and a scheme that vertically divides the light emitting area of the backlight into a plurality of scanning areas as shown in  FIG. 1  and causes the scanning areas to sequentially flash in synchronism with scanning of an image as shown in  FIG. 2  (to be generally referred to as “backlight scanning”) are used. 
     For example, in a liquid display apparatus using a backlight blink scheme described in Patent Literature 1, it is determined whether an input image is a still image or a moving image, and a driving duty (to be also referred to as a “duty” hereinafter) and a driving current (to be also referred to as a “peak value” hereinafter) of a light source is controlled. 
     For example, in a liquid display apparatus using a backlight scanning scheme described in Patent Literature 2, driving duties of a light source are controlled in units of scanning areas depending on the magnitude of motion of an image. 
     CITATION LIST 
     Patent Literature 
     PTL 1 
     
         
         Japanese Patent Publication No. 3535799
 
PTL 2
 
         Japanese Patent Application Laid-Open No. 2006-323300 
       
    
     SUMMARY OF THE INVENTION 
     Solution to Problem 
     In a liquid crystal display apparatus described in Patent Literature 2, even though an input image is a moving image, when a partial image in a certain image display area corresponding to a certain scanning area does not move, the scanning area is maintained without decreasing the driving duty of the scanning area. To be more specific, when duties of only the other scanning areas are decreased without decreasing a driving duty of the certain scanning area, a moving image resolution can be increased while suppressing blurring of the moving image. 
     In this case, in order to equally maintain brightness of all the scanning areas, a driving current of a scanning area the driving duty of which is decreased needs to be relatively increased. 
     However, when a driving duty and a driving current are controlled depending on motion as described above, although an average brightness does not change, a light source is driven by a driving waveform pattern (combination of a driving duty and a driving current changing depending on motion. For this reason, even though driving waveform patterns in which the same brightness are obtained are used, in transition from a certain driving waveform to another driving waveform, a flicker disadvantageously occurs under specific conditions. 
     In general, it is known that, when a brightness changes by a predetermined quantity or more within a residual image time (about 30 msec) of human eyes, the change in brightness is recognized as a flicker. The present inventor found that, even though driving waveform patterns in which the same brightness are obtained are used, flicker is generated upon change of driving waveforms under specific conditions. 
     For example, as shown in  FIG. 3A , an average brightness of brightnesses obtained after and before a period of transition of driving waveforms is A, a brightness in the period of transition of the driving waveforms diverges from A and becomes B (A(B). Therefore, when the degree of the divergence is large (for example, a change in peak value is large), a brightness changes to A (B (A in the residual image time of human eyes, a brightness changes by a predetermined quantity or more. For this reason, the change in brightness is recognized as a flicker. 
     As shown in  FIG. 3B , driving pulses are smoothly switched (for example, peak values are change smoothly in stages), a switching cycle (interval between timings of pulse switching) is excessively short, the same problem as described above is posed, and the change can be recognized as a flicker. 
     It is therefore an object of the present invention to provide a backlight apparatus and a display apparatus that prevent flicker caused by change of driving waveforms to make it possible to improve image quality when a driving duty and a driving current are controlled depending on motion. 
     Solution to Problem 
     A backlight apparatus according to the present invention includes a light emitting section having a plurality of light emitting areas; a motion amount detecting section that detects the amount of motion of an image in each of a plurality of moving areas corresponding to at least one of the light emitting areas; a driving condition designating section that designates driving conditions including the duty and peak value of a driving pulse to cause the plurality of light emitting areas to emit light based on the detected amount of motion; and a drive section that drives the plurality of light emitting areas according to the designated driving conditions, the driving condition designating section adjusts the driving conditions such that the driving conditions change smoothly in time. 
     The display apparatus according to the present invention includes a light modulating section that modulates illumination lights from the plurality of light emitting areas depending on an image signal to display an image. 
     Advantageous Effects of Invention 
     According to the present invention, when a driving duty and a driving current are controlled depending on motion, flicker caused by change of driving waveforms is prevented to make it possible to improve image quality. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram showing an example of a conventional scanning area; 
         FIG. 2  is a diagram for explaining a conventional backlight scanning scheme; 
         FIG. 3A  is a diagram showing an example of change of driving waveforms to explain a generation principle of a flicker upon change of driving waveforms, and  FIG. 3B  is a diagram showing another example of the change of driving waveforms to explain another example of the change of driving waveforms; 
         FIG. 4  is a block diagram showing a configuration of a liquid crystal display apparatus serving as a display apparatus according to Embodiment 1 of the present invention; 
         FIG. 5  is a diagram showing an image display area of a liquid crystal panel according to the embodiment; 
         FIG. 6  is a diagram showing a light emitting area and a scanning area of a display section according to the embodiment; 
         FIG. 7  is a block diagram showing a configuration of an LED driver according to the embodiment; 
         FIG. 8  is a diagram showing macro blocks segmented from an image display area according to the embodiment; 
         FIG. 9  is a block diagram showing a configuration of a motion amount detecting section in the embodiment; 
         FIG. 10  is a diagram for explaining a limiting rule of a change in peak value in the embodiment; 
         FIG. 11  is a block diagram showing an example of a configuration of a change control section in the embodiment; 
         FIG. 12  is a block diagram showing another example of a configuration of a change control section in the embodiment; 
         FIG. 13A  is a diagram showing an example of an ON/OFF signal waveform controlled by a scanning controller in the embodiment, and  FIG. 13B  is a diagram showing a duty of the ON/OFF signal shown in  FIG. 13A ; 
         FIG. 14A  is a diagram showing another example of an ON/OFF signal waveform controlled by a scanning controller in the embodiment, and  FIG. 14B  is a diagram showing a duty of an ON/OFF signal shown in  FIG. 14A ; 
         FIG. 15A  is a diagram showing a first example of a control result in the embodiment,  FIG. 15B  is a diagram showing a second example of the control result in the embodiment,  FIG. 15C  is a diagram showing a third example of a control result in the embodiment,  FIG. 15D  is a diagram showing a fourth example of the control result in the embodiment,  FIG. 15E  is a diagram showing a fifth example of a control result in the embodiment, and  FIG. 15F  is a diagram showing a sixth example of the control result in the embodiment; and 
         FIG. 16  is a block diagram showing a configuration of a liquid crystal display apparatus serving as a display apparatus according to Embodiment 2 of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In each of the embodiments, as a display apparatus, a liquid crystal display apparatus of an LED immediately-below type that directly radiates light of an LED from a backside of a liquid crystal panel will be described as a display apparatus. 
     (Embodiment 1) 
     Embodiment 1 of the present invention will be described below. 
     In the embodiment, a case in which a change in peak value and an updating cycle are suppressed in backlight scanning to prevent flicker upon change of driving waveforms will be described. The backlight scanning, as described above, is a technique that sequentially lights of scanning areas in synchronism with scanning of an image to reduce a residual image (moving image blurring). 
     &lt;1-1 Configuration of Liquid Crystal Display Apparatus&gt; 
     A configuration of a liquid crystal display apparatus will be described first.  FIG. 4  is a block diagram showing a configuration of a liquid crystal display apparatus according to the embodiment. Liquid crystal display apparatus  100  shown in  FIG. 4  has liquid crystal panel section  110 , illuminating section  120 , and drive control section  130 . A configuration of illuminating section  120  and drive control section  130  configures a backlight apparatus. 
     Configurations of the sections will be described below in detail. 
     &lt;1-1-1 Liquid Crystal Panel Section&gt; 
     Liquid crystal panel  110  has liquid crystal panel  111 , source driver  112 , gate driver  113 , and liquid crystal controller  114 . 
     In liquid crystal panel  110 , signal voltages are given from source driver  112  and gate driver  113  to pixels of liquid crystal panel  111  serving as a display section at a timing controlled by liquid crystal controller  114  to control a transmittance. Therefore, liquid crystal panel  111  can modulate an illumination light radiated from the backside of liquid crystal panel  111  depending on the image signals. In this manner, the image can be displayed in an image display area having a large number of pixels. To be more specific, liquid crystal panel  110  configures a light modulating section. 
     In this case, an image display area of liquid crystal panel  11  is partitioned by broken lines in  FIG. 4 . However, this clearly shows that liquid crystal panel  111  has a plurality of image display areas and does not mean that liquid crystal panel  111  is structurally divided or that the lines are displayed in the image. The same applies to other drawings. 
     In the embodiment, for example, as shown in  FIG. 5 , liquid crystal panel  111  will be explained such that liquid crystal panel  111  has, 16 (=4(4) image display areas  11  to  44  obtained by dividing an entire screen in the form of a matrix. 
     Although liquid crystal panel  111  is not specified, a panel using an IPS (In Plane Switching) scheme, a VA (Vertical Alignment) scheme, or the like can be used. 
     &lt;1-1-2 Illuminating Section&gt; 
     Illuminating section  120  emits an illumination light to display an image on liquid crystal panel  111  and radiates an the illumination light from the backside of liquid crystal panel  111  onto liquid crystal panel  111 . 
     Illuminating section  120  has light emitting section  121 . Light emitting section  121  employs a so-called direct-type configuration. Light emitting section  121  is arranged to face the backside of liquid crystal panel  111 , and a large number of point-like light sources are arranged in the form of a plane along the backside of liquid crystal panel  111  so as to emit lights towards the LCP  111 . Thereafter, light emitting section  121  emits the light generated from the light source and being incident on the backside from a front surface side. 
     In the embodiment, LEDs  122  are used as point-like light sources are used. All LEDs  122  emit white lights, and are configured to emit equal brightness when LEDs  122  are driven under the same driving conditions. Each of LEDs  122  may emit a white light by itself or may be configured to emit a white light by mixing RGB lights. 
     As the point-like light sources, light sources except for LEDs may be used, or light sources that emit lights except for white lights may be used. 
     In this case, in  FIG. 4 , a light emitting surface of light emitting section  121  is partitioned by a solid line. However, this clearly shows that light emitting section  121  has 4 (4=16) light emitting areas (see  FIG. 6 ) and does not mean that light emitting section  121  is structurally divided. The same applies to other drawings. 
     To be more specific, in the embodiment, as shown in  FIG. 6 , light emitting section  121  has 16 (=4(4) light emitting areas  11  to  44  obtained by dividing an entire light emitting surface in the form of a matrix. In this case, light emitting areas  11  to  14  are included in scanning area  1 , light emitting areas  21  to  24  are included in scanning area  2 , light emitting areas  31  to  34  are included in scanning area  3 , and light emitting areas  41  to  44  are included in scanning area  4 . 
     Illuminating section  120  has LED driver  123  serving as a drive section that drives LED  122 . LED driver  123  is arranged for each light emitting area. To be more specific, the light emitting area is a minimum driving control unit. 
       FIG. 7  shows an example of the configuration of LED driver  123 . LED driver  123  has constant current circuit  141  that supplies a current to a plurality of LEDs  122  connected in series with each other, communication interface (I/F)  142  that receives current value data representing a peak value of which constant current circuit  141  is notified from drive control section  130  via a communication terminal, digital to analog converter (DAC)  143  that converts the current value data into a current command signal serving as an analog signal, and switch  144  that makes it possible to input the current command signal from DAC  143  to constant current circuit  141  or blocks the current command signal. To be more specific, LED driver  123  is configured such that a current being in proportion to a signal voltage of the current command signal is supplied from constant current circuit  141  to LED  122  when switch  144  is in an ON state and the current supply is cut when the switch  144  is in an OFF state. In the embodiment, the configuration is equipped for each light emitting area. 
     With the above configuration, LED driver  123  independently drives a plurality of light emitting areas according to driving conditions including a duty (ON duty) and a peak value of a driving pulse designated per light emitting area to make it possible to emit light. In this manner, each light emitting area mainly radiates light on an image display area facing the light emitting area in a state in which the light emitting area is arranged to face the image display area corresponding to liquid crystal panel  111 . It is mentioned here that the light emitting area “mainly radiates light” because an illumination light is also radiated on an image display area that does not face the light emitting area. 
     &lt;1-1-3. Driving Control Section&gt; 
     Drive control section  130  is an arithmetic processing apparatus having motion amount detecting section  131 , brightness control section  132 , and brightness command value determining section  136 , and controls driving conditions including the duty and peak value of a driving pulse for each light emitting area based on an input image signal of each of the image display areas. Brightness control section  132  has peak value determining section  133 , change control section  134 , and duty determining section  135 . In drive control section  130 , a combination of brightness control section  132  (peak value determining section  133 , change control section  134 , and duty determining section  135 ) and scanning controller  136  configures a driving condition designating section that designates driving conditions based on the amount of motion. 
     &lt;1-1-3-1. Motion Amount Detecting Section&gt; 
     Motion amount detecting section  131  detects the amount of motion of an image based on an input image signal. The amount of motion is not calculated as two values such as 50% and 100% but is calculated as many values such as 3 or more values to optimize an apparent moving image resolution and an electric power. 
     As a method of detecting the amount of motion, a method of calculating an amount of motion by pattern matching a current frame with a previous frame with respect to all macro blocks in units of macro blocks is known. In this case, the macro block is each area defined by segmenting an image display area.  FIG. 8  shows a macro block in image display area  24  of liquid crystal panel  111 . As a simpler amount of motion detecting method, a method using a magnitude of a difference between image signals of a current frame and a previous frame at the same pixel position in place of a result of pattern matching or the like is known. 
     In the embodiment, motion amount detecting section  131  employs a configuration in which a maximum value of an amount of motion of each macro block calculated by the method that is the former is output as a detection value. To be more specific, when the maximum values of the moving areas when an image moves in an entire image display area and when an image moves in only a part of the image display area are equal to each other, the same values are output. 
       FIG. 9  shows a configuration of motion amount detecting section  131 . Motion amount detecting section  131  has 1 V delay section  151  that delays an input image signal by 1 frame, a macro block motion amount calculating section  152  that calculates the amount of motion of an image for each macro block, and maximum value calculating section  153  that calculates a maximum value in the calculated amount of motions. This configuration is equipped for each of the moving areas. 
     With the configuration, motion amount detecting section  131  detects the amount of motion of an image for each image display area. 
     &lt;1-1-3-2. Brightness Control Section&gt; 
     Brightness control section  132  determines a light emitting peak value and a light emitting duty of each light emitting area based on the amount of motion detected by motion amount detecting section  131 . In the embodiment, in order to prevent a change in brightness caused by a difference (in general, an adjusting resolution is lower than an adjusting resolution of a duty) between adjusting resolutions of a peak value and a duty of a driving pulse in LED driver  123 , after the light emitting peak value having a low adjusting resolution is determined first, a the duty having a high adjusting resolution is determined. To be more specific, after the light emitting peak value is determined based on the amount of motion, the light emitting duty is determined based on the obtained peak value. In this case, in the embodiment, in order to suppress flicker upon change of driving waveforms, a change in peak value and an updating cycle that are to be determined first are suppressed. Brightness control section  132  has peak value determining section  133 , change control section  134 , and duty determining section  135 . 
     Peak value determining section  133  determines a light emitting peak value for each light emitting area based on the amount of motion detected by motion amount detecting section  131 . To be more specific, for example, peak value determining section  133  applies a predetermined transformation formula to the amount of motion detected for each of the image display areas to calculate a light emitting peak value for each light emitting area, and the light emitting peak value is determined as a light emitting peak value designated per light emitting area. 
     Change control section  134  suppresses the change in peak value that is determined by peak value determining section  133  and the updating cycle according to corresponding predetermined limiting rules, respectively, to prevent flicker upon change of driving waveforms. The limiting rules are set with respect to the change in peak value and the updating cycle in advance based on, for example, an experiment result. 
     It is assumed that a command of changing peak value a to peak value a to peak value b by changing an output from motion amount detecting section  131  is received. These states are shown in  FIG. 10 . The states are driving pulses A and B each having the same duty (duty obtained in previous updating) and having peak value a and peak value b, respectively. At this time, a change in peak value in every updating is suppressed such that an average brightness of driving pulse A has a change (|(((|/((100(2) in peak value (=|a−b|) that is a change within a predetermined value (for example, 2%, desirably 1%) with respect to an average brightness of driving pulse B. In duty determining section  135  to be described later, the difference between the average brightnesses is cancelled. However, the difference appears as a flicker. Therefore, a change in peak value in which a flicker is allowed varies depending on duties at different times. To be more specific, a allowed change in peak value iDUTY (the unit of which is, for example, [mA]) is calculated each time the duty changes. When a command that causes a change in peak value exceeding the allowed peak value is received, the excess may be cut. In practice, since a change in average brightness with respect to a peak value is large when a duty is large, when all the changes in peak value&#39; are regulated by an allowed change in peak value i100 obtained when the duty is maximum (i.e. 100%), the change in peak value can be controlled. To be more specific, when the change in peak value is i100 or less, the change in peak value is not limited. However, when the change in peak value exceeds i100, the excess is cut. In this manner, change control section  134  outputs the peak value the change of which is controlled (i.e. corrected) as a controlled peak value. The controlled peak value is output to LED driver  123  of illuminating section  120  and duty determining section  135 . In this manner, the peak value is finally designated as a driving condition to each light emitting area. 
     Change control section  134  limits an updating cycle according a predetermined limiting rule. For example, change control section  134  suppresses the updating cycle to a half (about 15 msec) of an integral cycle (residual image time) of human eyes and does not make the updating cycle smaller than the half of the integral cycle. To be more specific, change control section  134  sets the updating cycle to a predetermined value (for example, 15 msec) or more. To be more specific, when a driving pulse is updated in accordance with a V cycle (vertical cycle) of an image signal having a frequency of 48 Hz, 50 Hz, or 60 Hz, these cycles are 16.6 msec at the shortest frequency of 60 Hz. For this reason, the above limiting rule is originally satisfied. In contrast to this, for example, when an amount of motion is detected for each image having a V cycle of 120 Hz to change driving pulses, since the cycle at 120 Hz is 8.3 msec, the limiting rule is not satisfied without changing the conditions. Therefore, in this case, for example, an updating cycle of a driving pulse is suppressed to an updating cycle that is every 2 Vs. As a result, the same updating cycle as that obtained at 60 Hz is set. Similarly, when the V cycle is 240 Hz, updating is performed in a cycle given as every 4 Vs. To be more specific, change control section  134  sets an output updating interval the V cycle of the image signal or an integral multiple of the V cycle to suppress the updating cycle within the predetermined limit. In this manner, change control section  134  determines the unit of the updating cycle as a V unit (when V is a constant speed) to make it possible to set the number of Vs every which updating is performed. 
     In place of the setting in which the updating cycle is an integral multiple of the V cycle, the change in peak value is limited to one integerth of an original allowable change in peak value to make it possible to prevent flicker upon change of driving waveforms. For example, when updating is performed every 120 Hz or 240 Hz, the updating cycle is not limited every 2 Vs or every 4 Vs, the change in peak value is limited to ½ or ¼ the original allowable change to make it possible to obtain the same effect. However, in this case, the nonlinearlity of brightness with respect to a peak value of a light source is neglected. However, the allowable change iDUTY or i100 is generally a narrow peak value range, and the range of variation of brightness corresponding to the peak value range is also narrow. Therefore, since it can be regarded that a relationship between the peak value and the brightness is almost linear in the above range, the above theory is satisfied. On the other hand, an allowable change in peak value calculated by limiting 2% (desirably, 1%) that is an allowable brightness change range serving as a conventional reference to ½ or ¼ is an accurate value. 
       FIG. 11  is a block diagram showing an example of a configuration of change control section  134 . In the example, change control section  134  uses a change limiter as a means that limits a change in peak value. To be more specific, change control section  134  has comparator  161  that detects a difference between a current peak value and a previous peak value (i.e. a peak value obtained in previous updating), limiter circuit  162  that limiting the detected difference to a predetermined value (i100) or less, adder  163  that adds or subtracts the difference limited to the predetermined value or less and the previous peak value to generate a controlled peak value, latch circuit  164  that temporarily holds the generated controlled peak value to cause the controlled peak value to pass in a predetermined updating cycle, and V counter  165  that sets an updating cycle to designate the number of Vs every which updating is performed. Limiter  162  configures a change limiter, and a combination of V counter  165  and latch circuit  164  configures an output updating interval setting section. With respect to an allowable change, a limiter upper limit iDUTY may be calculated every updating based on a duty obtained in previous updating. 
       FIG. 12  is a block diagram showing another example of a configuration of change control section  134 . In the example, change control section  134  uses filter  171  in a direction of time as a means that limits a change in peak value. Filter  171  filters an input (light emitting peak value) in a direction of a time axis (output is a controlled peak value). As filter  171 , as shown in  FIG. 12 , a general infinite impulse response ( 11 R) filter circuit can be used. In  FIG. 12 , for ease of explanation, latch circuit  164  and V counter  165  shown in  FIG. 11  are omitted. 
     Duty determining section  135  determines a light emitting duty of each light emitting area based on the controlled peak value the change of which is limited by change control section  134 . To be more specific, for example, duty determining section  135  applies a predetermined transformation formula to the controlled peak value determined for each light emitting area to calculate a light emitting duty to each light emitting area, and the light emitting duty is determined as a light emitting duty designated per light emitting area. The predetermined transformation formula, for example, is an ideal brightness retention curve calculated by measurement. Duty determining section  135  calculates a light emitting duty at which a brightness can be kept at a constant level based on the controlled peak value determined for each light emitting area. 
     In this case, brightness control section  132  controls the light emitting duty to increase the light emitting duty when the amount of motion is small and controls the light emitting duty to decrease the light emitting duty when the amount of motion is large, and controls the controlled peak value and the light emitting duty to keep a light emitting brightness serving as a result of the controlled peak value and the light emitting duty at a predetermined value. 
     When motion suddenly change, the amount of motion may vary for a short period of time. When scenes of an input image change or when there are a plurality of scenes, a motion detection error may occur in motion amount detecting section  131 . For this reason, the amount of motion may vary significantly. In this case, the driving conditions such as the duty and peak value of a driving pulse vary significantly within a short period of time depending on the amount of motion. In duty determining section  135 , a duty is calculated such that a constant brightness can be obtained even though a peak value changes. However, as described above, when driving waveforms having the same brightness are used, the same brightness may not be able to be accurately maintained in a period of transition of driving waveforms. Since human eyes have high sensitivity to a change in brightness, even an instantaneous slight change in brightness is recognized as a flicker. 
     According to the embodiment, since change control section  134  is arranged to suppress change of peak value and updating cycle, flicker generated upon change of driving waveforms can be prevented. 
     In the embodiment exemplifies a case in which, after the peak value is determined first, a duty is determined. However, the invention is not limited to the example. The present invention is also applicable to a case in which, after a duty is determined first, a peak value is determined. In this case, in order to suppress flicker upon change of driving waveforms, in addition to the updating cycle, a change of duty to be determined first is suppressed. Also in the case in which the change of duty is limited, the limiting rules for the change of duty may be set based on an experiment result in advance. To be more specific, the duty may be limited such that the duty does not change by 2% or more with reference to a duty obtained 1 V ago. 
     &lt;1-1-3-3. Scanning Controller&gt; 
     Scanning controller  136  generates an ON/OFF signal for each light emitting area at a timing (the updating cycle set as described above) set with reference to a vertical sync signal according to a driving duty (light emitting duty) determined for each light emitting area and outputs the generated ON/OFF signal to LED driver  123  of illuminating section  120 . In this manner, the driving duty is designated per light emitting area as a driving condition. In this manner, LED driver  123 , when an ON/OFF signal of a certain light emitting area is ON, drives the light emitting area to cause the light emitting area to emit light, and, when the ON/OFF signal is OFF, does not drive the light emitting area to generate a driving pulse without causing the light emitting area to emit light. As a result, the driving pulse is supplied to LED  122  included in the light emitting area. 
     Scanning controller  136  also performs pulse driving to have up to one pulse for one frame cycle of writing of liquid crystal panel  111 . In this manner, a residual image reducing, effect by narrowing a duty can be maximized. Furthermore, scanning controller  136  performs backlight scanning in which the timing of the driving pulse is synchronized with the timing at which pixels of liquid crystal panel  111  are updated and scanned. 
       FIG. 13A  shows an example of an ON/OFF signal waveform output from scanning controller  136 . In this case, an ON/OFF signal that is output when all driving duties determined with respect to four light emitting areas  11 ,  21 ,  31 , and  41  as shown in  FIG. 13B  are equal to each other (i.e. 50% is shown). Since image scanning is performed to image display area  11 , image display area  21 , image display area  31 , and image display area  41  in the order named, backlight scanning is also performed to light emitting area  11 , light emitting area  21 , light emitting area  31 , and light emitting area  41  in the order named. 
     In the example shown in  FIG. 13A , in an image scanning period of light emitting areas  11 ,  21 ,  31 , and  41 , timings at corresponding light emitting areas  11 ,  21 ,  31 , and  41  are turned off are controlled. For this reason, a moving image resolution can be improved. 
       FIG. 14A  shows another example of an ON/OFF signal waveform output from scanning controller  136 . In this case, ON/OFF signals output when driving duties determined with respect to four light emitting areas  11 ,  21 ,  31 , and  41  as shown in  FIG. 14B  are different from each other is shown. As shown in  FIG. 14A , when the driving duties of light emitting areas  11 ,  21 ,  31 , and  41  are changed, rising phases are changed without changing falling phases in the ON/OFF signals of light emitting areas  11 ,  21 ,  31 , and  41 . 
     The configuration of liquid crystal display apparatus  100  has been described above. 
     &lt;1-2. Operation of Liquid Crystal Display Apparatus&gt; 
     An operation (overall operation) executed by entire liquid crystal display apparatus  100  having the above configuration will be described below with a central focus on characteristic operations of the present invention. 
     &lt;1-2-1. Overall Operation&gt; 
     Motion amount detecting section  131  detects the amount of motion of an image based on an input image signal. The detected amount of motion is output to brightness control section  132 . 
     Brightness control section  132  determines controlled peak values and light emitting duties of the light emitting areas based on the amount of motion detected by motion amount detecting section  131 . In this case, in the embodiment, in order to prevent image quality from being deteriorated due to a low resolution of peak value adjustment, after a light emitting peak value having a low adjusting resolution is determined, a light emitting duty having a high adjusting resolution is determined. Furthermore, in order to prevent flicker upon change of driving waveforms, when driving conditions are changed, the driving conditions are adjusted such that the driving conditions change smoothly in time. In this case, in the embodiment, in order to suppress flicker upon change of driving waveforms, a change in peak value that is to be determined first and an updating cycle are suppressed. 
     To be more specific, peak value determining section  133  applies a predetermined transformation formula to the amount of motion detected by motion amount detecting section  131  to determine a light emitting peak value for each light emitting area. Change control section  134  suppresses the change in peak value determined by peak value determining section  133  and the updating cycle according to corresponding predetermined limiting rules, respectively. Thereafter, duty determining section  135  applies a predetermined transformation formula to a controlled peak value obtained for each light emitting area every updating to determine a light emitting duty for each light emitting area. In this case, the light emitting duty is controlled to increase the light emitting duty when the amount of motion is small, and the light emitting duty is controlled to decrease the light emitting duty when the amount of motion is large, and the controlled peak value and the light emitting duty are controlled to keep a light emitting brightness serving as a result of the controlled peak value and the light emitting duty at a predetermined value. The controlled peak value obtained by change control section  134  is output to LED driver  123  of illuminating section  120 , and the light emitting duty determined by duty determining section  135  is output to scanning controller  136 . 
     Scanning controller  136  generates an ON/OFF signal for each light emitting area at a timing (the updating cycle set as described above) set with reference to a vertical sync signal according to a light emitting duty determined by duty determining section  135  for each light emitting area. The generated ON/OFF signal is output to LED driver  123  of illuminating section  120 . 
     &lt;1-2-2. Effect&gt; 
     With the above operation, for example, driving waveforms are controlled as shown in  FIG. 15A to 15F  to make it possible to prevent flicker upon change of driving waveforms (however, except for the cases shown in  FIGS. 15B and 15D ). 
     To be more specific, for example, in the case shown in  FIG. 15A , the maximum change C in peak value is a predetermined value (iDUTY) or less, and the updating cycle is sufficiently large. For this reason, flicker is not generated upon change of driving waveforms. In contrast to this, as shown in  FIG. 15B , even though the updating cycle is sufficiently large, when the maximum change D in peak value exceeds the predetermined value (iDUTY), flicker is generated upon change of driving waveforms. 
     In the case shown in  FIG. 15C , maximum change in peak value C is a predetermined value (iDUTY) or less, and the updating cycle (15 msec) is a predetermined value (15 msec) or more. For this reason, flicker is not generated upon change of driving waveforms. In contrast to this, as shown in  FIG. 15D , even though maximum change in peak value D is a predetermined value (iDUTY) or less, when the updating cycle (7.5 msec) is shorter than the predetermined value (15 msec), flicker is generated upon change of driving waveforms. 
     However, in the case shown in  FIG. 15D , for example, the updating cycle is doubled as shown in  FIG. 15E , or, as shown in  FIG. 15F , the maximum change in peak value is ½ the original allowable change C to make it possible to prevent flicker upon change of driving waveforms. 
     In this manner, according to the embodiment, since change control section  134  is arranged to suppress change of peak value and updating cycle, flicker generated upon change of driving waveforms can be prevented. Therefore, when a driving duty and a driving current are controlled depending on motion, flicker caused by change of driving waveforms is prevented to make it possible to improve image quality. 
     In the embodiment, the case in which a plurality of different driving duties and a plurality of different driving currents are controlled in a horizontal direction in the same scanning area. However, the present invention is not limited to the configuration. For example, the present invention is also applicable to the case in which light emitting areas are not divided in the horizontal direction (i.e. amount of motion detection is not performed in image display areas divided in the horizontal direction). Furthermore, the scanning area may be separated from a vertical dividing unit for detecting the amount of motion as a lighting phase control unit. In this case, the image display area and an area boundary of backlight scanning are overlapped, and an LED needs to be driven and controlled in new area units surrounded by the boundary. To be more specific, the overlapped boundary is a virtual boundary of new light emitting areas. This is also applied to the subsequent embodiments. 
     (Embodiment 2) 
     Embodiment 2 of the present invention will be described below. A liquid crystal display apparatus according to the embodiment has the same basic configuration as that of the liquid crystal display apparatus according to the embodiment described above. Therefore, the same reference numerals as in the above embodiment denote the same or corresponding constituent elements in Embodiment 2, and a description thereof will be omitted. Different points between Embodiment 2 and the embodiment described above will be mainly described below. 
     In the embodiment, a case in which a change in peak value and an updating cycle are suppressed in a combination of backlight scanning and local dimming to prevent flicker upon change of driving waveforms will be described. In this case, the local dimming is a technique that controls a brightness for each light emitting area in accordance with an image to improve a contrast. 
     &lt;2-1. Configuration of Liquid Crystal Display Apparatus&gt; 
       FIG. 16  is a block diagram showing a configuration of a liquid crystal display apparatus according to the embodiment. Liquid crystal display apparatus  200  shown in  FIG. 16  has drive control section  210  in place of drive control section  130 . Drive control section  210  is an arithmetic processing apparatus having motion amount detecting section  131 , brightness control section  132 , feature amount detecting section  211 , brightness command value determining section  212 , duty correcting section  213 , and scanning control section  136   a , and controls driving conditions including the duty and peak value of a driving pulse for each light emitting area based on an input image signal of each of the image display areas. Brightness control section  132  has peak value determining section  133 , change control section  134 , and duty determining section  135 . In drive control section  210 , a combination of brightness control section  132  (peak value determining section  133 , change control section  134 , and duty determining section  135 ), duty correcting section  213 , and scanning controller  136   a  configures a driving condition designating section that designates driving conditions based on the amount of motion. 
     The scanning area is a control unit of backlight scanning, and the light emitting area is a drive control unit of an LED. In the embodiment, a case in which the scanning area corresponds to a plurality of image display areas, respectively. 
     &lt;2-1-1. Feature Amount Detecting Section&gt; 
     Feature amount detecting section  211  detects a feature amount of an input image signal. To be more specific, feature amount detecting section  211  mainly detects a feature amount of the input image signal for each image display area of liquid crystal panel  111 . In this case, the “feature amount” is a feature amount related to the brightness of an image signal of each of the image display areas on liquid crystal panel  111 . As the feature amount, for example, a maximum brightness level and a minimum brightness level of the image signal of each of the image display areas on liquid crystal panel  111 , the difference between the maximum brightness level and the minimum brightness level, an average brightness level, and the like can be used. The “mainly” is added in the above description because final feature amounts of the image display areas may be determined in consideration of the feature amounts of all the image signals and the feature amounts of an image display area arranged around an image display area to be calculated. 
     &lt;2-1-2. Brightness Command Value Determining Section&gt; 
     Brightness command value determining section  212  determines a brightness command value of each light emitting area based on the amount of feature detected by feature amount detecting section  211 . To be more specific, for example, brightness command value determining section  212  calculates a brightness value (brightness command value) at which each light emitting area should emit light from the detected feature amount by using a transformation table, a transformation function, and the like having predetermined characteristics. The brightness command value is set with reference to a brightness command value obtained when the light emitting duty is 100%. 
     &lt;2-1-3. Duty Correcting Section&gt; 
     Duty correcting section  213  corrects the brightness command value determined by brightness command value determining section  212  based on a light emitting duty determined by duty determining section  135 . To be more specific, for example, duty correcting section  213  is configured by a multiplier. The brightness command value determined by brightness command value determining section  212  is multiplied (superposed) by the light emitting duty determined by the duty determining section  135  to determine a correction duty serving as a final light emitting duty. To be more specific, duty correcting section  213  normalizes (corrects) a brightness command value obtained by local dimming by using the light emitting duty obtained based on a detected amount of motion and outputs the result as a correction duty. 
     In the above explanation, a dividing operation generally performed in normalization is not described. It is assumed that duty correcting section  213  is a digital input/output. For example, in the specification, the brightness command value duty and the light emitting duty are input in 8 bits each and output to scanning control section  136   a  in 16 hits. In this case, since a multiplication result of duties each having 8 bits has 16 hits, a dividing operation is not performed. When the multiplication result is rounded to have  8  bits and then multiplied by, the eighth power of 2 to obtain a 16-bit result, a rounding error is generated in vain. Such an operation is not performed here. When the output has X bits, only high X bits are wired and output based on a multiplication result between the brightness command value and the light emitting duty. In this manner, when an input/output of duty correcting section  213  is digital data, a functional block serving as a divider need not be specially arranged. A dividing operation that cuts off lower bits depending on the number of output bits is merely interposed. Therefore, in the above description, it is assumed that duty correcting section  213  is configured by a multiplier. 
     &lt;2-1-4. Scanning Controller&gt; 
     Scanning controller  136   a  generates an ON/OFF signal for each light emitting area at a timing (the updating cycle set as described above) set with reference to a vertical sync signal according to a correction duty determined for each light emitting area and outputs the generated ON/OFF signal to LED, driver  123  of illuminating section  120 . 
     In this manner, according to the embodiment, as in Embodiment 1, since change control section  134  is arranged to suppress change of peak value and updating cycle, flicker generated upon change of driving waveforms can be prevented. 
     Therefore, in the configuration obtained by combining backlight scanning and local dimming, even though a driving duty and a driving current are controlled depending on motion, flicker generated by change of driving waveforms is prevented to make it possible to improve image quality. 
     In the embodiment, reference image display areas in detection of an amount of motion and detection of a feature amount for local dimming are similar divided units. However, the areas may be different from each other. In this case, it is assumed that the former is called a moving area and the latter is called a brightness area for ease of explanation. In this manner, the image display area is defined as an area surrounded by a boundary obtained by overlapping a virtual boundary of moving areas and a virtual boundary of brightness areas. In Embodiment 1, the image display area and the moving area are equal to each other. In Embodiment 2, an image display area, a moving area, and a brightness area are equal to each other. A light emitting area serving as an LED driving control unit is an area surrounded by a boundary obtained when a boundary of the image display areas and a boundary of the scanning areas are overlapped. 
     Embodiments of the present invention have been described above. The above explanation is an exemplification of a preferred embodiment of the present invention, and the spirit and scope of the present invention are not limited to the embodiments. To be more specific, the configurations and the operations of the apparatus described in each of the embodiments are only illustrations. The configurations and the operations can be partially changed, added, and deleted without departing from the spirit and scope of the invention as a matter of course. 
     For example, each embodiment above exemplifies a case where the present invention is applied to a liquid crystal display apparatus. However, even though a light modulating section has a display section different from a liquid crystal panel, another non-self-luminous configuration can be employed. To be more specific, the present invention is also applicable to a non-self-luminous display apparatus except for a liquid crystal display apparatus. 
     The disclosure of Japanese Patent Application No. 2009-230734, filed on Oct. 2, 2009, including the specification, drawings and abstract; is incorporated herein by reference in its entirety. 
     INDUSTRIAL APPLICABILITY 
     A backlight apparatus and a display apparatus according to the present invention, when a driving duty and a driving current are controlled depending on motion, advantageously prevent flicker caused by change of driving waveforms to make it possible to improve image quality, and are useful as a backlight apparatus and a display apparatus using a scheme that controls a driving duty and a driving current depending on motion. 
     REFERENCE SIGNS LIST 
     
         
           100 ,  200  Liquid crystal display apparatus 
           110  Liquid crystal panel section 
           111  Liquid crystal panel 
           112  Source driver 
           113  Gate driver 
           114  Liquid crystal controller 
           120  Illuminating section 
           121  Light emitting section 
           122  LED 
           123  LED driver 
           130 ,  210  Drive control section 
           131  Motion amount detecting section 
           132  Brightness control section 
           133  Peak value determining section 
           134  Change control section 
           135  Duty determining section 
           136 ,  136   a  Scanning controller 
           211  Feature amount detecting section 
           212  Brightness command value determining section 
           213  Duty correcting section 
           141  Constant current circuit 
           142  Communication I/F 
           143  DAC 
           144  Switch 
           151  1-V Delay section 
           152  Macro block motion amount calculating section 
           153  Maximum value calculating section 
           161  Comparator 
           162  Limiter circuit 
           163  Adder 
           164  Latch circuit 
           165  V counter 
           171  Filter in direction of time