TECHNICAL FIELD
The present invention relates to liquid crystal display devices employing a scanning backlight scheme, and methods for controlling a scanning backlight.
BACKGROUND ART
Liquid crystal display devices are a hold-type or non-stroboscopic display. Therefore, when a moving image is displayed, a smearing or ghosting artifact may occur. The smearing or ghosting artifact is a phenomenon that, for example, when a white ball is moving in the black background, a gray shadow appears in the wake of the white ball. A state in which the smearing or ghosting artifact is present is called a motion blur. This does not occur in cathode ray tube (CRT) displays, which are an impulse-type or stroboscopic display.
In order to reduce the motion blur, the backlight may be intermittently turned on. For example, as described in PATENT DOCUMENTS 1-3, a scanning backlight scheme is known in which a backlight is divided into a plurality of regions, and the regions are successively turned on.
CITATION LIST
Patent Document
PATENT DOCUMENT 1: Japanese Patent Publication No. 2007-123233
PATENT DOCUMENT 2: Japanese Patent Publication No. 2009-063751
PATENT DOCUMENT 3: Japanese Patent Publication No. 2009-133956
SUMMARY OF THE INVENTION
Technical Problem
FIG. 25 is a diagram for describing a process for the turn-on timing of a light source in the conventional scanning backlight scheme. Examples of the light source include an LED, a CCFL, an HCFL, an organic EL, etc. As shown in FIG. 25, in the conventional scanning backlight scheme, LEDs for regions S1-S8 corresponding to the uppermost to lowermost scanning lines, which are obtained by dividing an image formation region, are turned on/off in a region-by-region basis in synchronization with timings of writing image data schematically indicated by an arrow Dt. In FIG. 25, the reference character S1 indicates the uppermost position, and the reference character S2 indicates the second uppermost position. Therefore, for example, leakage light L1 from the region S1 to the region S2 occurs.
FIG. 26 is a diagram for describing an influence of the leakage light from the region S1 into the region S2. In FIG. 26, a reference character LS indicates a light source, a reference character LC indicates liquid crystal, a reference character Lon indicates that the light source is on, a reference character Loff indicates that the light source is off, a reference character RE indicates that the response of liquid crystal has been finished, and a reference character RM indicates that liquid crystal is responding. As shown in FIG. 26, in each of the regions S1 and S2, when the response of liquid crystal has been finished, the LED is on, and when liquid crystal is responding, the LED is off. Therefore, when the LED of the region S1 is on, the light L1 leaks into the region S2, the region S3, etc. As a result, because liquid crystal is responding in the region S2, the region S3, etc., the light leaking into the region S2, the region S3, etc., adversely affects display in the region S2, the region S3, etc. In the region S2 adjacent to the region S1, the response period of liquid crystal almost ends, and therefore, the influence is relatively small. However, as one progresses away from the region S1 to the region S3, the region S4, etc., illumination occurs at a timing closer to the midpoint of the response period, resulting in a greater influence on display. Specifically, when the leakage light from the uppermost region S1 reaches the lowermost region, the timing offset is greatest, resulting in a most adverse influence on display.
Such leakage light is generated not only by the LEDs of upper regions, but also by the LEDs of lower regions. The presence of leakage light causes mixture of images of successive frames, disadvantageously resulting in a degradation in display quality.
The present invention has been made in view of the above problem. It is an object of the present invention to provide a liquid crystal display device employing a scanning backlight scheme which reduces the degradation of display quality, and a method for controlling a scanning backlight.
Solution to the Problem
In order to achieve the object, in the present invention, a delayed turn-on process of delaying turn-on timings of a predetermined number of uppermost regions, or an advanced turn-off process of advancing turn-off timings of a predetermined number of lowermost regions, is performed.
Specifically, a liquid crystal display device according to a first aspect of the present invention is a liquid crystal display device with a scanning backlight scheme including a light source having a plurality of light emitting units configured to illuminate a plurality of respective regions S1-Sn obtained by dividing an image formation region, corresponding to scanning lines, where the region S1 corresponds to the uppermost scanning line, the Sn region corresponds to the lowermost scanning line, n is a natural number of three or more, and the light emitting units corresponding to the respective regions are turned on on a region-by-region basis during respective predetermined on periods between respective reference turn-on timings and respective reference turn-off timings of the light emitting units in synchronization with respective timings of writing image data. The device includes a timing controller configured to perform a delayed turn-on process of causing turn-on timings of the light emitting units of the regions S1-Si, where i is a natural number of 1≦i<n, to be later than the respective reference turn-on timings, or an advanced turn-off process of causing turn-off timings of the light emitting units of the regions Sn-Sj, where j is a natural number of 1≦i<j≦n, to be earlier than the respective reference turn-off timings. As used herein, the reference turn-on timing refers to a turn-on timing which is used as a reference when the light emitting unit of each region is turned on. As used herein, the reference turn-off timing refers to a turn-off timing which is used as a reference when the light emitting unit of each region is turned off.
With this configuration, leakage light from the light emitting units of the regions S1-Si into lower regions, or leakage light from the light emitting units of the regions Sn-Sj into upper regions, can be reduced. Therefore, light illumination during the start or end of response of liquid crystal can be reduced, and light illumination is performed when liquid crystal is in the stable response state. As a result, the degradation of display quality due to mixture of successive frame images can be reduced.
In the delayed turn-on process, the timing controller preferably delays the turn-on timings of the light emitting units of the regions S1-Si so that the turn-on timings of the light emitting units of the regions S1-Si are the same as the turn-on timing of the light emitting unit of the Si+1 region.
With this configuration, leakage light from the light emitting units of the regions S1-Si into lower regions can be reliably reduced. Therefore, light illumination during the start of response of liquid crystal can be further reduced, whereby the degradation of display quality can be further reduced.
In the advanced turn-off process, the timing controller preferably advances the turn-off timings of the light emitting units of the Sm-Sj regions so that the turn-off timings of the light emitting units of the regions Sn-Sj are the same as the turn-off timing of the light emitting unit of the Sj−1 region.
With this configuration, leakage light from the light emitting units of the regions Sn-Sj ino upper regions can be reliably reduced. Therefore, light illumination during the end of response of liquid crystal can be further reduced, whereby the degradation of display quality can be further reduced.
The number i may be one, i.e., the region Si is the region S1. With this configuration, leakage light from the light emitting unit of the region S1which has a most adverse influence on lower regions can be reduced.
The number j may be n, i.e., the region Sj is the region Sn. With this configuration, leakage light from the light emitting unit of the region Sn which has a most adverse influence on upper regions can be reduced.
The timing controller preferably causes emission intensities of the light emitting units of the regions S1-Si, to be higher than emission intensities of the light emitting units of the other regions. The on periods of the light emitting units of the regions S1-Si are reduced because the respective turn-on timings are delayed, and therefore, the amount of light emitted decreases. With this configuration, the emission intensities of the light emitting units of the regions S1-Si, are increased, whereby the decrease of the amount of light emitted can be reduced or prevented.
The emission intensity of the light emitting unit of the Si region is preferably a maximum of ta/ti times as high as the emission intensities of the light emitting units of the other regions, where ta is the predetermined on period, and ti is an on period of the light emitting unit of the Si region. As used herein, the predetermined on period ta refers to a period of time during which the light emitting unit of the light source is on. In order to uniformly illuminate the entire panel with light of the light source, all rows have equal predetermined on periods. The on period of the region Si is shorter than the normal on period ta, and therefore, the amount of light emitted in the region Si is ti/ta times as high as that in the normal regions. With this configuration, however, the emission intensity of the region Si is increased by a factor of a maximum of ta/ti, whereby the decrease of the amount of light emitted in the region Si can be reliably reduced or prevented.
The timing controller preferably causes emission intensities of the light emitting units of the regions Sn-Sj to be higher than emission intensities of the light emitting units of the other regions. The on periods of the light emitting units of the regions Sn-Sj are reduced because the respective turn-off timings are delayed, and therefore, the amount of light emitted decreases. With this configuration, however, the emission intensities of the light emitting units of the regions Sn-Sj are increased, whereby the decrease of the amount of light emitted can be reduced or prevented.
The emission intensity of the light emitting unit of the Si region is preferably a maximum of ta/tj times as high as the emission intensities of the light emitting units of the other regions, where ta is the predetermined on period, and tj is an on period of the light emitting unit of the Sj region. The on period of the region Sj is shorter than the normal on period ta, and therefore, the amount of light emitted in the region Sj is tj/ta times as high as that in the normal regions. With this configuration, however, the emission intensity of the region Si is increased by a factor of a maximum of ta/tj, whereby the decrease of the amount of light emitted in the region Sj can be reliably reduced or prevented.
The timing controller preferably causes the turn-off timings of the light emitting units of the regions S1-Si to be later than the respective reference turn-off timings. The on periods of the light emitting units of the regions S1-Si are reduced because the respective turn-on timings are delayed, and therefore, the amount of light emitted decreases. With this configuration, the turn-off timings are delayed, and therefore, the on periods are supplemented, whereby the decrease of light emitted can be reduced or prevented.
In this configuration, times by which the turn-off timings of the light emitting units of the regions S1-Si are delayed are preferably shorter than respective times by which the turn-on timings of the light emitting units of the regions S1-Si are delayed. With this configuration, the decrease of light emitted can be reliably reduced or prevented while leakage light into lower regions due to the delayed turn-off timings is reliably reduced or prevented.
The timing controller preferably causes the turn-on timings of the light emitting units of the regions Sn-Sj to be earlier than the respective reference turn-off timings. The on periods of the light emitting units of the regions Sn-Sj are reduced because the respective turn-off timings are advanced, and therefore, the amount of light emitted decreases. With this configuration, the turn-on timings are advanced, and therefore, the on periods are supplemented, whereby the decrease of light emitted can be reduced or prevented.
In this configuration, times by which the turn-on timings of the light emitting units of the regions Sn-Sj are advanced are preferably shorter than respective times by which the turn-off timings of the light emitting units of the regions Sn-Sj are advanced. With this configuration, the decrease of light emitted can be reliably reduced or prevented while leakage light into upper regions due to the advanced turn-on timings is reliably reduced or prevented.
A scanning backlight controlling method according to a second aspect of the present invention is a method for controlling a scanning backlight in a liquid crystal display device including a light source having a plurality of light emitting units configured to illuminate a plurality of respective regions S1-Sn obtained by dividing an image formation region, corresponding to scanning lines, where the region S1 corresponds to the uppermost scanning line, the Sn region corresponds to the lowermost scanning line, n is a natural number of three or more, and the light emitting units corresponding to the respective regions are turned on on a region-by-region basis during respective predetermined on periods between respective reference turn-on timings and respective reference turn-off timings of the light emitting units in synchronization with respective timings of writing image data. A delayed turn-on process of causing turn-on timings of the light emitting units of the regions S1-Si, where i is a natural number of 1≦i<n, to be later than the respective reference turn-on timings, or an advanced turn-on process of causing turn-off timings of the light emitting units of the regions Sn-Sj, where j is a natural number of 1≦i<j≦n, to be earlier than the respective reference turn-off timings, is performed.
According to the present invention, the turn-on timings of a predetermined number of uppermost regions are delayed so that leakage light into lower regions is reduced, or the turn-off timings of a predetermined number of lowermost regions are advanced so that leakage light into upper regions is reduced, whereby the degradation of display quality can be reduced.
ADVANTAGES OF THE INVENTION
According to the present invention, light illumination during the start or end of response of liquid crystal can be reduced, whereby the degradation of display quality can be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing a configuration of a liquid crystal display device according to a first embodiment.
FIG. 2 is a diagram for describing an image formation region of the liquid crystal display device of the first embodiment.
FIG. 3 is a diagram for describing a process of delaying a turn-on timing of an LED of a region S1.
FIG. 4 is a diagram for describing the principle of reduction of leakage light from the region S1 into a region S2.
FIG. 5 is a diagram for describing a process of advancing a turn-off timing of an LED of a region S8.
FIG. 6 is a diagram for describing the principle of reduction of leakage light from the region S8 into a region S7.
FIG. 7 is a diagram for describing a process of delaying the turn-on timing of the LED of the region S1, and in addition, advancing the turn-off timing of the LED of the region S8.
FIG. 8 is a diagram for describing a process of delaying the turn-on timings of the LEDs of the regions S1 and S2.
FIG. 9 is a diagram for describing a liquid crystal display device which displays 3D video which is viewed using optical shutter glasses.
FIG. 10 is a diagram for describing that the timing of writing image data to liquid crystal is asynchronous with the timing of switching the optical shutter glasses between the light transmission mode (on) and the light non-transmission mode (off).
FIG. 11 is a diagram for describing the timing of writing image data to liquid crystal and the timing of switching the optical shutter glasses between the light transmission mode (on) and the light non-transmission mode (off), where the turn-on timings of the regions S1 and S2 are delayed.
FIG. 12 is a diagram for describing a process of advancing the turn-off timings of the LEDs of the regions S8 and S7.
FIG. 13 is a diagram for describing the timing of writing image data to liquid crystal and the timing of switching the optical shutter glasses between the light transmission mode (on) and the light non-transmission mode (off), where the turn-off timings of the regions S8 and S7 are advanced.
FIG. 14 is a diagram for describing a process of delaying the turn-on timings of the LEDs of the regions S1 and S2, and in addition, advancing the turn-off timings of the LEDs of the regions S8 and S7.
FIG. 15 is a diagram for describing the timing of writing image data to liquid crystal and the timing of switching the optical shutter glasses between the light transmission mode (on) and the light non-transmission mode (off), where the turn-on timings of the regions S1 and S2 are delayed, and in addition, the turn-off timings of the regions S8 and S7 are advanced.
FIG. 16 is a diagram for describing a process of delaying the turn-on timings of the LEDs of the regions S1 and S2.
FIG. 17 is a diagram for describing a process of advancing the turn-off timings of the LEDs of the regions S8 and S7.
FIG. 18 is a diagram for describing a process of delaying the turn-on timings of the LEDs of the regions S1 and S2, and in addition, advancing the turn-off timings of the LEDs of the regions S8 and S7.
FIG. 19 is a diagram for describing the decrease of the amount of light emitted in the region S1 which occurs when the turn-on timing of the LED of the region S1 is delayed.
FIG. 20 is an explanatory diagram schematically showing the emission intensity of the LED of the region S1 in the conventional art, the emission intensity of the LED of the region S1 in the first embodiment, and the emission intensity of the LED of the region S1 in a tenth embodiment, for the purpose of comparison.
FIG. 21 is a diagram for describing that when the turn-off timing of the LED of the region S8 is advanced, the amount of light emitted in the region S8 is reduced.
FIG. 22 is an explanatory diagram schematically showing the emission intensity of the LED of the region S8 in the conventional art, the emission intensity of the LED of the region S8 in a second embodiment, and the emission intensity of the LED of the region S8 in an eleventh embodiment, for the purpose of comparison.
FIG. 23 is an explanatory diagram schematically showing the emission intensity of the LED of the region S1 in the conventional art, the emission intensity of the LED of the region S 1 in the first embodiment, and the emission intensity of the LED of the region S1 in a twelfth embodiment, for the purpose of comparison.
FIG. 24 is an explanatory diagram schematically showing the emission intensity of the LED of the region S8 in the conventional art, the emission intensity of the LED of the region S8 in the second embodiment, and the emission intensity of the LED of the region S8 in a thirteenth embodiment, for the purpose of comparison.
FIG. 25 is a diagram for describing a process for the turn-on timing of a light source in the conventional scanning backlight scheme.
FIG. 26 is a diagram for describing an influence of leakage light from the region Si into the region S2.
DESCRIPTION OF EMBODIMENTS
Embodiments of the present invention will be specifically described hereinafter with reference to the accompanying drawings. The embodiments are for the purpose of facilitating understanding of the principle of the present invention. The scope of the present invention is not intended to be limited to the embodiments. Those skilled in the art will make replacements or modifications to the embodiments when necessary without departing the scope of the present invention.
First Embodiment
FIG. 1 is a block diagram showing a configuration of a liquid crystal display device 900 according to a first embodiment. FIG. 2 is a diagram for describing an image formation region of the liquid crystal display device 900 of the first embodiment. The configuration of the liquid crystal display device 900 will be described with reference to FIGS. 1 and 2.
As shown in FIG. 1, the liquid crystal display device 900 includes an array substrate 111 and a counter substrate 112 (transparent substrates) facing each other with a liquid crystal layer 126 being interposed therebetween (i.e., the array substrate 111 and the counter substrate 112 are separated from each other by a predetermined distance). A counter electrode (common electrode) (not shown) is formed on the counter substrate 112. The array substrate 111 and the counter substrate 112 are not particularly limited, but may be, for example, a substrate which can transmit light, such as a glass plate, a quartz plate, etc. The liquid crystal layer 126 is not particularly limited, but may be, for example, of the following types: twisted nematic (TN); guest-host (GH); super-twisted nematic (STN); super-twisted birefringence effect (SBE); electrically controlled birefringence (ECB); etc.
The array substrate 111 includes a plurality of scanning lines 114 (from GL1 (uppermost line) to GLm (lowermost line) arranged in a scan direction). A plurality of data lines 113 are also provided, intersecting with the scanning lines 114. A pixel electrode 115 is provided in each of pixel regions arranged in a matrix and separated by the data lines 113 and the scanning lines 114. The pixel electrode 115 and the counter electrode are formed of a light-transmissive conductive material, such as indium tin oxide (ITO), etc. A thin film transistor (TFT) 116 is provided as a switching element in the vicinity of each of intersection portions of the scanning lines 114 and the data lines 113. The source electrode of the thin film transistor 116 is connected to the data line 113, the gate electrode is connected to the scanning line 114, and the drain electrode is connected to the pixel electrode 115 facing a storage capacitor 125 and the liquid crystal layer 126.
The data lines 113 are connected to a data driver 133 and a data line drive circuit 137. The scanning lines 114 are connected to a gate driver 134 and a scanning line drive circuit 138. The data line drive circuit 137 and the scanning line drive circuit 138 are connected to and controlled by a control circuit 130. An external data signal is input to the control circuit 130 to generate, based on vertical and horizontal synchronization signals, a clock signal for inputting data to the data driver 133 and a clock signal for changing the scanning lines.
As shown in FIG. 2, the image formation region of the liquid crystal display device 900 is divided into a plurality of regions S1-Sn extending along the horizontal scanning lines GL1 (uppermost scanning line) to GLm (lowermost scanning line). In this embodiment, there are eight regions S1-S8.
A backlight 150 is provided on the back side of the array substrate 111, facing the array substrate 111. The backlight 150 is used to illuminate an entire region of the back surface of the liquid crystal display device 900. The backlight 150 includes a plurality of light emitting units. Each light emitting unit is provided for a corresponding one of the regions S1-S8 in order to illuminate that region. In this embodiment, the backlight 150 includes eight direct-type LEDs 151-158 as the light emitting units. The direct-type LEDs 151-158 correspond to the regions S1-S8, respectively.
As shown in FIG. 1, the LEDs are connected to a lamp drive circuit 131 and a drive voltage timing control circuit (timing controller) 132. The drive voltage timing control circuit 132 controls timings of turning on or off the LEDs. Specifically, the drive voltage timing control circuit 132 performs a delayed turn-on process of causing the turn-on timings of the light emitting units of the regions S1-Si to be later than respective reference turn-on timings, or an advanced turn-off process of causing the turn-off timings of the light emitting units of the regions Sn-Sj to be earlier than respective reference turn-off timings, where i and j are natural numbers satisfying 1≦i<j≦8. Note that, if i is one, only the turn-on timing of the LED of the region S1 is delayed. If j is eight, only the turn-on timing of the LED of the region S8 is advanced. Both the delayed turn-on process and the advanced turn-off process can be simultaneously performed.
Next, operation of the liquid crystal display device 900 thus configured will be described with reference to FIGS. 1, 3, and 4. FIG. 3 is a diagram for describing the process of delaying the turn-on timing of the LED of the region Si.In FIG. 3, a reference character S1 indicates the uppermost region, and a reference character S2 indicates the second uppermost region. FIG. 4 is a diagram for describing the principle of reduction of leakage light from the region S1 into the region S2. In FIG. 4, a reference character LS indicates a light source, a reference character LC indicates liquid crystal, a reference character Lon indicates that the light source is on, a reference character Loff indicates that the light source is off, a reference character RE indicates that the response of liquid crystal has been finished, and a reference character RM indicates that liquid crystal is responding. This holds true for the description that follows.
As shown in FIG. 1, the data driver 133 starts operation of a shift register simultaneously with the rise of a start pulse, and performs operation while receiving a clock signal. Data input simultaneously with the clock signal is stored into a sampling memory selected by the shift register. When display data for all horizontal lines has been transferred, the control circuit 130 outputs a latch pulse. When the data driver 133 receives the latch pulse, a hold memory simultaneously latches the data stored in the sampling memory. D/A conversion is performed on the latched data, and the resulting data is output to the data lines 113. An on-voltage is applied to one of the scanning lines 114, so that all the thin film transistors 116 on the corresponding one row are turned on, whereby one line of data is displayed. By repeatedly performing the above operation in a similar manner, all the scanning lines 114 are scanned and driven in the order of from GL1 to GLm.
When a scanning line control signal is successively supplied to the scanning lines GL1-GLm, the lamp drive circuit 131 turns on the LED corresponding to the scanning line 114 to which the scanning line control signal has been supplied. Thus, the LEDs 151-158 are successively turned on. As shown in FIG. 3, the drive voltage timing control circuit 132 causes the turn-on timing of the LED of the region S1 to be later than the reference turn-on timing so that the turn-on timing of the LED of the region S1 is the same as that of the LED of the region S2. Specifically, as shown in FIG. 4, if the regions S1 and S2 have the same turn-on timing, the adverse influence on display of the leakage light from the region S1 into the region S2 and the following regions is reduced or eliminated, whereby the degradation of display quality can be reduced. As one progresses away from the region S1, illumination by the leakage light from the region S1 occurs at a timing closer to the midpoint of the response period, resulting in a greater influence on display. When the leakage light from the region S1 reaches the lowermost region, the timing offset is greatest, resulting in a most adverse influence on display. According to this embodiment, the leakage light from the region S1, which causes such a problem, can be reduced.
Note that, in this embodiment, the regions S1 and S2 have the same turn-on timing, and therefore, the on period of the LED of the region S1 decreases, so that the amount of light emitted decreases, and therefore, the luminance of the region S1 decreases. However, the reduction of the on period to some extent is preferable because the power consumption of the backlight can be reduced, and is also not substantially disadvantageous, because it is at an end portion of the screen that the luminance decreases.
Second Embodiment
In the first embodiment, the turn-on timing of the uppermost region S1 is delayed. The present invention is not limited to such an embodiment. In a second embodiment, the turn-off timing of the lowermost region S8 is advanced.
FIG. 5 is a diagram for describing a process of advancing the turn-off timing of the LED of the region S8. FIG. 6 is a diagram for describing the principle of reduction of leakage light from the region S8 into the region S7.
As shown in FIG. 5, in the second embodiment, the turn-off timing of the LED of the region S8 is caused to be earlier than the reference turn-off timing so that the turn-off timing of the LED of the region S8 is the same as the turn-off timing of the LED of the region S7. Specifically, as shown in FIG. 6, if the region S8 has the same turn-off timing as that of the region S7, the adverse influence on display of leakage light from the region S8 into the region S7 is reduced or eliminated, whereby the degradation of display quality can be reduced. As one progresses away from the region S8, illumination by the leakage light from the region S8 occurs at a timing closer to the midpoint of the response period, resulting in a greater influence on display. When the leakage light from the region S8 reaches the uppermost region, the timing offset is greatest, resulting in a most adverse influence on display. According to this embodiment, the leakage light from the region S8, which causes such a problem, can be reduced.
Note that, in this embodiment, similar to the first embodiment, the on period of the LED of the region S8 decreases, and therefore, the luminance of the region S8 decreases. However, for a reason similar to that of the first embodiment, the reduction of the on period to some extent is not substantially disadvantageous.
Third Embodiment
In the first embodiment, the turn-on timing of the uppermost region S1 is delayed, and in the second embodiment, the turn-off timing of the lowermost region S8 is advanced. The present invention is not limited to such embodiments. In a third embodiment, the turn-on timing of the region S1 is delayed, and in addition, the turn-off timing of the region S8 is advanced.
FIG. 7 is a diagram for describing a process of delaying the turn-on timing of the LED of the region S1, and in addition, advancing the turn-off timing of the LED of the region S8. As shown in FIG. 7, the turn-on timing of the LED of the region S1 is caused to be later than the reference turn-on timing so that the turn-on timing of the LED of the region S1 is the same as the turn-on timing of the LED of the region S2, and in addition, the turn-off timing of the LED of the region S8 is caused to be earlier than the reference turn-off timing so that the turn-off timing of the LED of the region S8 is the same as the turn-off timing of the LED of the region S7. As a result, leakage light from the region S1 into the region 52 can be reduced, and in addition, leakage light from the region S8 into the region S7 can be reduced, whereby the degradation of display quality can be further reduced.
Fourth Embodiment
In the first embodiment, the turn-on timing of the uppermost region S1 is delayed. The present invention is not limited to such an embodiment. In a fourth embodiment, the turn-on timings of the LEDs of a plurality of regions including the uppermost region S1 are delayed. Specifically, the turn-on timings of the LEDs of the region S1 and the region S2 are delayed.
FIG. 8 is a diagram for describing a process of delaying the turn-on timings of the LEDs of the regions S1 and S2. As shown in FIG. 8, the turn-on timings of the LEDs of the regions S1 and S2 are caused to be later than the respective reference turn-on timings so that the turn-on timings of the LEDs of the regions S1 and S2 are the same as the turn-on timing of the LED of the region S3. As a result, leakage light from the regions S1 and S2 into the region S3 can be reduced, whereby the degradation of display quality can be further reduced.
Next, a case where the scanning backlight driving technique of this embodiment is applied to a liquid crystal display device which displays 3D video which is viewed using optical shutter glasses, will be described. FIG. 9 is a diagram for describing the liquid crystal display device 900 which displays 3D video which is viewed using optical shutter glasses. As shown in FIG. 9, the optical shutter glasses 210 includes components for the left and right eyes which have a function of switching between a light transmission mode (on) and a light non-transmission mode (off) to transmit or block image light from the liquid crystal display device 900 so that the left and right eyes are allowed to view only particular images. The liquid crystal display device 900 includes a switch controller which switches the optical shutter glasses 210 between the light transmission mode (on) and the light non-transmission mode (off) in synchronization with image cycles. Specifically, the liquid crystal display device 900 includes an optical shutter glasses control circuit 211. The optical shutter glasses control circuit 211 receives a synchronization signal 221 from the liquid crystal display device 900, and transmits a shutter glasses control signal 222 to the optical shutter glasses 210, to switch the optical shutter glasses 210 between the light transmission mode and the light non-transmission mode in synchronization with the image cycles.
FIG. 10 is a diagram for describing that the timing of writing image data to liquid crystal is asynchronous with the timing of switching the optical shutter glasses between the light transmission mode (on) and the light non-transmission mode (off). Here, for example, white display is performed for the left eye, and black display is performed for the right eye. In FIG. 10, a reference character LW indicates that white display is performed for the left eye, a reference character RB indicates that black display is performed for the right eye, a reference character GRon indicates that the right side of the glasses is on, and a reference character GLomn indicates that the left side of the glasses is on. This holds true for the description that follows. As shown in FIG. 10, the timing of starting writing data to liquid crystal differs from place to place in the liquid crystal screen. Therefore, the timing of writing data to liquid crystal is asynchronous with the timing of switching the optical shutter glasses between the light transmission mode (on) and the light non-transmission mode (off).
In a region II shown in FIG. 10, leakage light from upper regions (the region S1 etc.) is present outside a period tX during which the response of liquid crystal is stable. Also in a region IV, leakage light from upper regions (the region S1 etc.) is present outside a period tX during which the response of liquid crystal is stable. Therefore, in the regions II and IV, an image for one eye enters the other eye due to the leakage light.
On the other hand, FIG. 11 is a diagram for describing the timing of writing image data to liquid crystal and the timing of switching the optical shutter glasses between the light transmission mode (on) and the light non-transmission mode (off), where the turn-on timings of the regions S1 and S2 are delayed. In this embodiment, the turn-on timings of the LEDs of the regions S1 and S2 are delayed to be the same as the turn-on timing of the LED of the region S3, whereby leakage light from the regions S1 and S2 into the region S3 is reduced. Therefore, as shown in FIG. 11, light illumination during the start of response of liquid crystal can be reduced. Therefore, when the scanning backlight driving technique of this embodiment is applied to a liquid crystal display device which displays 3D video which is viewed using shutter glasses, the situation that an image for one eye enters the other eye can be reduced or prevented.
Fifth Embodiment
In the fourth embodiment, the turn-on timings of the S1 (uppermost) and S2 regions are delayed. The present invention is not limited to such an embodiment. In a fifth embodiment, the turn-off timings of the LEDs of a plurality of regions including the lowermost region S8 are advanced. Specifically, the turn-off timings of the regions S8 and S7 are advanced.
FIG. 12 is a diagram for describing a process of advancing the turn-off timings of the LEDs of the regions S8 and S7. As shown in FIG. 12, the turn-off timings of the LEDs of the regions S8 and S7 are caused to be earlier than the respective reference turn-off timings so that the turn-off timings of the LEDs of the regions S8 and S7 are the same as the turn-off timing of the LED of the region S6. As a result, leakage light from the regions S8 and S7 into the region S6 can be reduced, whereby the degradation of display quality can be further reduced.
Next, a case where the scanning backlight driving technique of this embodiment is applied to a liquid crystal display device which displays 3D video which is viewed using optical shutter glasses as in the fourth embodiment, will be described.
As shown in FIG. 10 described above, in the region I, the right eye of the optical shutter glasses is in the light transmission mode (on), but receives left-eye image data. In the region III, the left eye of the optical shutter glasses is in the light transmission mode (on), but receives right-eye image data. Therefore, in the regions I and III of FIG. 10, crosstalk occurs.
On the other hand, FIG. 13 is a diagram for describing the timing of writing image data to liquid crystal and the timing of switching the optical shutter glasses between the light transmission mode (on) and the light non-transmission mode (off), where the turn-off timings of the regions S8 and S7 are advanced. In this embodiment, the turn-off timings of the LEDs of the regions S8 and S7 are advanced to be the same as the turn-off timing of the LED of the region S6, whereby leakage light from the regions S8 and S7 into the region S6 is reduced. Therefore, as shown in FIG. 13, light illumination can be reduced during the end of response of liquid crystal. Therefore, although crosstalk occurs in the regions I and III of FIG. 10 as described above, in this embodiment the emission of the LEDs in the regions I and III can be reduced. Therefore, when the scanning backlight driving technique of this embodiment is applied to a liquid crystal display device which displays 3D video which is viewed using shutter glasses, the situation that inappropriate video enters the eyes due to the occurrence of crosstalk can be reduced or prevented.
Sixth Embodiment
In the fourth embodiment, the turn-on timings of the regions S1 and S2 are delayed, and in the fifth embodiment, the turn-off timings of the regions S8 and S7 are advanced. The present invention is not limited to such embodiments. In a sixth embodiment, the turn-on timings of the LEDs of a plurality of regions including the uppermost region S1 are delayed, and in addition, the turn-off timings of the LEDs of regions including the lowermost region S8 are advanced. Specifically, the turn-on timings of the LEDs of the regions S1 and S2 are delayed, and in addition, the turn-off timings of the LEDs of the regions S8 and S7 are advanced.
FIG. 14 is a diagram for describing a process of delaying the turn-on timings of the LEDs of the regions S1 and S2, and in addition, advancing the turn-off timings of the LEDs of the regions S8 and S7. As shown in FIG. 14, the turn-on timings of the LEDs of the regions S1 and S2 are caused to be later than the respective reference turn-on timings so that the turn-on timings of the LEDs of the regions S1 and S2 are the same as the turn-on timing of the LED of the region S3. As a result, leakage light from the regions S1 and S2 into the region S3 is reduced. The turn-off timings of the LEDs of the regions S8 and S7 are caused to be earlier than the respective reference turn-off timings so that the turn-off timings of the LEDs of the regions S8 and S7 are the same as the turn-off timing of the LED of the region S6. As a result, leakage light from the regions S8 and S7 into the region S6 is reduced. Therefore, the degradation of display quality can be more significantly reduced.
Next, a case where the scanning backlight driving technique of this embodiment is applied to a liquid crystal display device which displays 3D video which is viewed using optical shutter glasses as in the fourth and fifth embodiments, will be described.
FIG. 15 is a diagram for describing the timing of writing image data to liquid crystal and the timing of switching the optical shutter glasses between the light transmission mode (on) and the light non-transmission mode (off), where the turn-on timings of the regions S 1 and S2 are delayed, and in addition, the turn-off timings of the regions S8 and S7 are advanced.
In this embodiment, the turn-on timings of the LEDs of the regions S1 and S2 are delayed to be the same as the turn-on timing of the LED of the region S3, whereby leakage light from the regions S1 and S2 into the region S3 is reduced. In addition, the turn-off timings of the LEDs of the regions S8 and S7 are advanced to be the same as the turn-on timing of the LED of the region S6, whereby leakage light from the regions S8 and S7 into the region S6 is reduced. Therefore, as shown in FIG. 15, light illumination during the start and end of response of liquid crystal can be reduced. As a result, when the scanning backlight driving technique of this embodiment is applied to a liquid crystal display device which displays 3D video which is viewed using shutter glasses, the situation that an image for one eye enters the other eye can be reduced or prevented, and the situation that inappropriate video enters the eyes due to the occurrence of crosstalk can be reduced or prevented.
Seventh Embodiment
In the fourth embodiment, the turn-on timings of the regions S1 and S2 are delayed to be the same as the turn-on timing of the LED of the region S3. The present invention is not limited to such an embodiment. In the seventh embodiment, the turn-on timings of the regions S1 and S2 are not the same as the turn-on timing of the LED of the region S3.
FIG. 16 is a diagram for describing a process of delaying the turn-on timings of the LEDs of the regions S 1 and S2. In this embodiment, as shown in FIG. 16, the turn-on timings of the regions S1 and S2 are delayed until a timing earlier than the turn-on timing of the LED of the region S3. The LEDs of the regions S1 and S2 have the same turn-on timing. In this embodiment, although leakage light into the region S3 is less reduced than in the fourth embodiment, the amount of light emitted in the regions S1 and S2 can be further maintained than in the fourth embodiment.
Eighth Embodiment
In the fifth embodiment, the turn-off timings of the regions S8 and S7 are advanced to be the same as the turn-off timing of the LED of the region S6. The present invention is not limited to such an embodiment. In an eighth embodiment, the turn-off timings of the regions S8 and S7 are not the same as the turn-off timing of the LED of the region S6.
FIG. 17 is a diagram for describing a process of advancing the turn-off timings of the LEDs of the regions S8 and S7. In this embodiment, as shown in FIG. 17, the turn-off timings of the regions S8 and S7 are advanced to a timing later than the turn-on timing of the LED of the region S6. The LEDs of the regions S7 and S8 have the same turn-off timing. In this embodiment, although leakage light into the region S6 is less reduced than in the fifth embodiment, the amount of light emitted in the regions S8 and S7 can be further maintained than in the fifth embodiment.
Ninth Embodiment
In the seventh embodiment, the turn-on timings of the regions S1 and S2 are delayed, and in the eighth embodiment, the turn-off timings of the regions S8 and S7 are advanced. The present invention is not limited to such embodiments. In a ninth embodiment, the turn-on timings of the regions S1 and S2 are delayed without being the same as the turn-on timing of the LED of the region S3, and the turn-off timings of the regions S8 and S7 are advanced without being the same as the turn-off timing of the LED of the region S6.
FIG. 18 is a diagram for describing a process of delaying the turn-on timings of the LEDs of the regions S1 and S2, and in addition, advancing the turn-off timings of the LEDs of the regions S8 and S7. In this embodiment, as shown in FIG. 18, the turn-on timings of the regions S1 and S2 are delayed until a timing earlier than the turn-on timing of the LED of the region S3, and the turn-off timings of the regions S8 and S7 are advanced to a timing later than the turn-on timing of the LED of the region S6. The LEDs of the regions S1 and S2 have the same turn-on timing. The LEDs of the regions S7 and S8 have the same turn-off timing. In this embodiment, leakage light into the region S3 and leakage light into the region S6 can be reduced to some extent while the amount of light emitted is maintained to some extent.
Tenth Embodiment
In the first embodiment, the turn-on timing of the LED of the region S1 is delayed, and therefore, the on period of the LED of the region S1 is reduced, so that the amount of light emitted decreases. In this embodiment, the decrease of the amount of light emitted is reduced while the turn-on timing of the LED of the region S1 is delayed.
FIG. 19 is a diagram for describing the decrease of the amount of light emitted in the region S1 which occurs when the turn-on timing of the LED of the region S1 is delayed. As described in the first embodiment, when the turn-on timing of the LED of the region S1 is caused to be later than the reference turn-on timing, the on periods of the LEDs of the regions S2-S8 are uniformly an on period ta, and the on period of the LED of the region S1 is t1 shorter than ta. Therefore, the on period of the LED of the region S1 is reduced, whereby the amount of light emitted is reduced by an amount corresponding to a portion AL shown in FIG. 19.
In this embodiment, the emission intensity of the LED of the region S1 whose turn-on timing is delayed is caused to be higher than those of the other LEDs. FIG. 20 is an explanatory diagram schematically showing the emission intensity of the LED of the region S1 in the conventional art, the emission intensity of the LED of the region S1 in the first embodiment, and the emission intensity of the LED of the region S1 in the tenth embodiment, for the purpose of comparison. As shown in FIG. 20, in this embodiment, while, as in the first embodiment, the turn-on timing is delayed to a further extent than in the conventional art, the emission intensity of the LED is increased by a factor of a maximum of ta/t1. In FIG. 20, M(ta/t1) indicates that the emission intensity of the LED is ta/t1 times as high. As a result, the decrease of the amount of light emitted can be reduced or prevented while leakage light from the region S1 into the region 52 is reduced to reduce the degradation of display quality.
Note that it is not preferable that the emission intensity of the LED of the region S1 be more than ta/t1 times as high. This is because, if the emission intensity is more than ta/t1 times as high, the demand for a reduction in the power consumption of the backlight is not satisfied, and the luminance of an end portion of the screen is emphasized, resulting in unnatural display.
Eleventh Embodiment
In the second embodiment, the turn-off timing of the LED of the region S8 is advanced, and therefore, the on period of the LED of the region S8 is reduced, so that the amount of light emitted decreases. In this embodiment, the decrease of the amount of light emitted is reduced while the turn-off timing of the LED of the region S8 is advanced.
FIG. 21 is a diagram for describing that when the turn-off timing of the LED of the region S8 is advanced, the amount of light emitted in the region S8 is reduced. As shown in FIG. 21, the turn-off timing of the LED of the region S8 is caused to be earlier than the reference turn-off timing, the on periods of the LEDs of the regions S1-S7 are uniformly an on period ta, and the on period of the LED of the region S8 is t8 shorter than ta. Therefore, the on period of the LED of the region S8 is reduced, whereby the amount of light emitted is reduced by an amount corresponding to a portion AL shown in FIG. 21.
In this embodiment, the emission intensity of the LED of the region S8 whose turn-off timing is advanced is caused to be higher than those of the other LEDs. FIG. 22 is an explanatory diagram schematically showing the emission intensity of the LED of the region S8 in the conventional art, the emission intensity of the LED of the region S8 in the second embodiment, and the emission intensity of the LED of the region S8 in the eleventh embodiment, for the purpose of comparison. As shown in FIG. 22, in this embodiment, while, as in the second embodiment, the turn-off timing is advanced to a further extent than in the conventional art, the emission intensity of the LED is increased by a factor of a maximum of ta/t8. In FIG. 22, M(ta/t8) indicates that the emission intensity of the LED is ta/t8 times as high. As a result, the decrease of the amount of light emitted can be reduced or prevented while leakage light from the region S8 into the region S7 is reduced to reduce the degradation of display quality. Note that, for a reason similar to that described in the tenth embodiment, it is not preferable that the emission intensity of the LED of the region S8 be more than ta/t8 times as high.
Twelfth Embodiment
In the tenth embodiment, the decrease of the amount of light emitted due to the reduction of the on period of the LED of the region S1 is reduced by increasing the emission intensity of the LED. The present invention is not limited to such an embodiment. In this embodiment, while the turn-on timing of the LED of the region S1 is delayed, the decrease of the amount of light emitted is reduced by using a configuration different from that of the tenth embodiment.
FIG. 23 is an explanatory diagram schematically showing the emission intensity of the LED of the region S1 in the conventional art, the emission intensity of the LED of the region S1 in the first embodiment, and the emission intensity of the LED of the region S1 in the twelfth embodiment, for the purpose of comparison. As shown in FIG. 23, in this embodiment, as in the first embodiment, the turn-on timing of the LED of the region S1 is caused to be later than the reference turn-on timing, and the turn-off timing is caused to be later than the turn-off timings of the LEDs of the other regions (the regions S2-S8). Because the turn-on timing is delayed, the on period decreases, and therefore, the amount of light emitted decreases. However, in this embodiment, the on period is extended by delaying the turn-off timing, whereby the decrease of the amount of light emitted can be reduced.
In this embodiment, a time tB1 by which the turn-off timing is delayed is preferably shorter than a time tF1 by which the turn-on timing of the region S1 is delayed. In other words, the on period t1A of the LED of the region S1 of this embodiment is preferably longer than the on period t1 of the LED of the region S1 of the first embodiment and shorter than the on periods ta of the LEDs of the regions S2-S8. This is because, if the time tB1 by which the turn-off timing is delayed is longer than the time tF1 by which the turn-on timing is delayed, the demand for a reduction in the power consumption of the backlight is not satisfied, and the luminance of an end portion of the screen is emphasized, resulting in unnatural display.
Thirteenth Embodiment
In the eleventh embodiment, the decrease of the amount of light emitted due to the reduction of the on period of the LED of the region S8 is reduced by increasing the emission intensity of the LED. The present invention is not limited to such an embodiment. In this embodiment, while the turn-off timing of the LED of the region S8 is advanced, the decrease of the amount of light emitted is reduced by a configuration different from that of the eleventh embodiment.
FIG. 24 is an explanatory diagram schematically showing the emission intensity of the LED of the region S8 in the conventional art, the emission intensity of the LED of the region S8 in the second embodiment, and the emission intensity of the LED of the region S8 in the thirteenth embodiment, for the purpose of comparison. As shown in FIG. 24, in this embodiment, as in the second embodiment, the turn-off timing of the LED of the region S8 is caused to be earlier than the reference turn-off timing, and the turn-on timing is caused to be earlier than the turn-on timings of the LEDs of the other regions (the regions S1-S7). Because the turn-off timing is advanced, the on period decreases, and therefore, the amount of light emitted decreases. However, in this embodiment, the on period is extended by advancing the turn-on timing, whereby the decrease of the amount of light emitted can be reduced.
In this embodiment, a time tF2 by which the turn-on timing is advanced is preferably shorter than a time tB2 by which the turn-off timing is advanced. In other words, the on period t8A of the LED of the region S8 of this embodiment is preferably longer than the on period t8 of the LED of the region S8 of the second embodiment and shorter than the on periods ta of the LEDs of the regions S1-S7. This is because, if the time tF2 by which the turn-on timing is advanced is longer than the time tB2 by which the turn-off timing is advanced, the demand for a reduction in the power consumption of the backlight is not satisfied, and the luminance of an end portion of the screen is emphasized, resulting in unnatural display.
Other Embodiments
In the tenth embodiment, the emission intensity of the LED of the region S1 is increased by a factor of a maximum of ta/t1, and in the eleventh embodiment, the emission intensity of the LED of the region S8 is increased by a factor of a maximum of ta/t8. The present invention is not limited to such embodiments. Alternatively, for example, the emission intensity of the LED of the region S1 may be increased by a factor of a maximum of ta/t1, and in addition, the emission intensity of the LED of the region S8 may be increased by a factor of a maximum of ta/t8.
In the twelfth embodiment, the turn-off timing of the LED of the region S1 is delayed, and in the thirteenth embodiment, the turn-on timing of the LED of the region S8 is advanced. The present invention is not limited to such embodiments. Alternatively, for example, the turn-off timing of the LED of the region S1 is delayed, and in addition, the turn-on timing of the LED of the region S8 is advanced.
In the above embodiments, the backlight 150 includes a plurality of direct-type LEDs. Alternatively, the backlight 150 may include a plurality of cold cathode fluorescent lamps.
INDUSTRIAL APPLICABILITY
The present invention is applicable to a liquid crystal display device employing a scanning backlight scheme, and a liquid crystal display device which displays 3D video which is viewed using optical shutter glasses.
DESCRIPTION OF REFERENCE CHARACTERS
111 ARRAY SUBSTRATE
112 COUNTER SUBSTRATE
113 DATA LINE
114 SCANNING LINE
115 PIXEL ELECTRODE
116 THIN FILM TRANSISTOR
125 STORAGE CAPACITOR
126 LIQUID CRYSTAL LAYER
130 CONTROL CIRCUIT
132 DRIVE VOLTAGE TIMING CONTROL CIRCUIT
133 DATA DRIVER
134 GATE DRIVER
137 DATA LINE DRIVE CIRCUIT
138 SCANNING LINE DRIVE CIRCUIT
150 BACKLIGHT
151-158 LED
210 OPTICAL SHUTTER GLASSES
211 OPTICAL SHUTTER GLASSES CONTROL CIRCUIT
221 SYNCHRONIZATION SIGNAL
222 SHUTTER GLASSES CONTROL SIGNAL
900 LIQUID CRYSTAL DISPLAY DEVICE
Patent Application
20130044273
