BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1
a and 1b are schematic diagrams showing the partition of scanning areas of a conventional LCD device.
FIGS. 2
a and 2b are schematic diagrams showing the scanning sequence according to a first embodiment of the present invention.
FIGS. 3
a and 3b are schematic diagrams showing the interconnection between the gate lines and the scan lines of FIGS. 2a and 2b.
FIG. 4 is a timing diagram according to the first embodiment of the present invention.
FIG. 5 is another timing diagram according to the first embodiment of the present invention.
FIG. 6 is a schematic diagram showing the brightness distribution across the sections of scan lines according to the present invention.
FIGS. 7
a, 7b, and 7c are schematic diagrams showing the scanning sequence according to a second embodiment of the present invention.
FIGS. 8
a, 8b, and 8c are schematic diagrams showing the scanning sequence according to a second embodiment of the present invention.
FIG. 9 is a table summarizing the features of various embodiments of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following descriptions are exemplary embodiments only, and are not intended to limit the scope, applicability or configuration of the invention in any way. Rather, the following description provides a convenient illustration for implementing exemplary embodiments of the invention. Various changes to the described embodiments may be made in the function and arrangement of the elements described without departing from the scope of the invention as set forth in the appended claims.
As mentioned earlier, the present invention arises from the resolution of the discontinuity problem of conventional color-filter-less LCD devices. However, the LCD devices proposed by the present invention can be ones with or without color filters. The related scanning methods are also applicable to LCD devices with or without color filters. In the following, a number of more complicated embodiments of the LCD device of present invention will be described first. These LCD devices all have no color filter, use red, green, and blue LEDs as backlight sources, and separate a frame into red, green, and blue sub-frames which are displayed sequentially. Once these more complicated embodiments are understood, the application of the present invention to LCD devices with color filters requires no further explanation. In other words, the present invention does not specifically require the presence or the omission of the color filter, but the present invention is most valuable when there is no color filter.
FIGS. 2
a and 2b are schematic diagrams showing the scanning sequence according to a first embodiment of the present invention. In this embodiment, it is assumed that the LCD device has a resolution 1920×1080, but the present invention can actually applied to LCD devices of other resolutions. As illustrated, the pixels of the LCD device is partitioned horizontally into scanning areas S1 and S2, each containing 540 rows of pixels numbered as row 1˜540, and row 541˜1080, respectively (hereinafter, each row of pixels is referred to as a scan line). Each scanning area is further partitioned into 10 sections numbered as I1˜I10 and I11˜I20, each containing 54 scan lines. Behind each section, the backlight module of the LCD device (not shown) has a correspond LED set so as to illuminate the scan lines within each section. In other words, the LED set behind the section I1 illuminates the scan lines 1˜54, the LED set behind the section I2 illuminates the scan lines 55˜108, and so on. Each LED set contains an appropriate number of appropriately arranged red, green, and blue LEDs. The backlight module has an appropriate driving circuit under the control of a driving mechanism to individually control the on/off of the various colored LEDs within each set. The number and arrangement of the LEDs and the driving circuit should be quite familiar to people of related arts and their details are omitted here.
To resolve the discontinuity problem of dynamic images, the scan lines of the scanning areas S1 and S2 are scanned line by line towards or away from their interfacing border. As shown in FIG. 2a, the scanning area S1 is scanned from the scan line 540, 539, . . . , down to the scan line 1, while the scanning area S2 is scanned concurrently from the scan line 541, 542, . . . , up to the scan line 1080. In contrast, in FIG. 2b, the scanning area S1 is scanned from the scan line 1, 2, . . . , up to the scan line 540, while the scanning area S2 is scanned concurrently from the scan line 1080, 1079, . . . , down to the scan line 541. In other words, in FIG. 2a, the scanning areas S1 and S2 are scanned in an opposite direction away from their interfacing border (i.e., from the scan lines 540 and 541 respectively). In FIG. 2b, the scanning areas S1 and S2 are scanned also in an opposite direction towards their interfacing border (i.e., to the scan lines 540 and 541 respectively). As such, the jump or discontinuity phenomenon across the border can be completely resolved.
To achieve the scanning sequence shown in FIG. 2a, the implementation is explained as follows. As shown in FIG. 3a, to scan the scanning areas S1 and S2 in an opposite direction away from their border, the scan line 540 of the scanning area S1 and the scan line 541 of the scanning area S2 have to be scanned simultaneously. Therefore, as shown in FIG. 3a, the two scan lines are connected to a gate line G1 from the same gate driver. The scenario applies to other scan lines as well until the scan line 1 of the scanning area S1 and the scan line 1080 of the scanning area S2 are connected to the same gate line G540. Similarly, as shown in FIG. 3b, to achieve the scanning sequence shown in FIG. 2b, the scan line 1 of the scanning area S1 and the scan line 1080 of the scanning area S2 are connected to the same gate line G1, and so on. In the present embodiment, therefore, the LCD device requires total 540 gate lines.
Using FIG. 3a as an example, when the gate line G1 is enabled to scan both the scan lines 540 and 541 of the two scanning areas S1 and S2, image data has to be written into the 1920 pixels of the scan line 540 and the 1920 pixels of the scan line 541 simultaneously. For example, the image data for the first pixels of the scan lines 540 and 541 is written through two data lines 1A and 1A′ respectively, via a so-called source driver or data driver. Similarly, the image data for the 1920th pixels of the scan lines 540 and 541 is written through two data lines 1920A and 1920A′ respectively. In the present embodiment, therefore, the LCD device requires total 1920×2=3840 data lines separated into two groups, each having 1920 data lines for the 1920 pixels of the scan lines of a scanning area. For a conventional 1920×1080 LCD device having color filter, up to 1080 gate lines are required. In addition, as red, green, and blue image data has to be delivered to the three sub-pixels of a pixel simultaneously, up to 1920×3=5760 data lines are required. In contrast, the present embodiment requires only 540 gate lines and, as the red, green, and blue image data is delivered in a time-division manner, only up to 3840 data lines are required.
In this specification, the so-called “horizontal” or “vertical” direction is referred relative to the panel of the LCD device. Please note that, in the foregoing embodiment, the scanning areas are partitioned horizontally because conventionally the scan lines are arranged horizontally and the data lines are arranged vertically. Technically, a panel can also have the scan lines arranged vertically and the data lines arranged horizontally. For this kind of panel, the scanning areas will be partitioned vertically. Therefore, more specifically, the partition of the scanning areas of the present invention is conducted parallel to the scan lines. In the following, for simplicity and without losing generality, the subsequent embodiments assume that the scan lines are arranged horizontally and therefore the scanning areas are partitioned horizontally.
Take the foregoing embodiment as an example, if the scan lines are arranged vertically and the data lines are arranged horizontally, then, up to 960 (1920/2) gate lines and 2160 (1080×2) data lines are required. In other words, for panels of vertically arranged scan lines, the total number of gate lines and data lines will be further reduced, contributing an even lower cost.
To further explain the principle of the present invention, FIG. 4 provides a timing diagram based on the scanning sequence of FIG. 2b. As shown in FIG. 4, each vertical column shows the data and status of the sections I1˜I20 at a particular point of time (i.e., the horizontal axis). For a section, it is denoted as Rn, Gn, or Bn when the section contains the image data of the red, green, or blue sub-frame of a current frame (n), respectively. When the LED set behind the section is turned on, the section is denoted as an Rn, Gn, or Bn encircled by a box. On the other hand, Rn−, Gn−, or Bn− refers to the image data of the red, green, or blue sub-frame of a previous frame (n−); and Rn+, Gn+ or Bn+ refers to the image data of the red, green, or blue sub-frame of a next frame (n+). In the present embodiment, time is measured by a unit ΔT which is the period of time required to scan an entire section. Therefore, a point of time Tn is equal to nΔT and all periods of time are multiple integrals of ΔT. As the period of time required to finish the simultaneous scanning of the scanning areas S1 and S2 cannot exceed the 5.55-ms sub-frame time, the scanning time of each scan line (including the time for enabling the gate line, writing data via the data lines, and storing the data by the pixels) is at most 5.55 ms/540≈10.3 μs. Since each section contains 54 scan lines, the scanning time of a section ΔT is 10.3 μs×54≈0.55 ms. Please note that to reduce the scanning time of a scan line down to 10.3 μs is not practical with existing technologies. However, the present embodiment is described here mainly as a simplified example to the principle and operation of the present invention.
The present embodiment displays the red, green, and blue sub-frames sequentially. Therefore, after the initial 10ΔT (i.e., at T10), the image data R1˜R20 of the red sub-frame has been written into the sections I1˜I20. Then, after another 10ΔT (i.e., at T20), the image data G1˜G20 of the green sub-frame has been written into the sections I1˜I20. Again, after another 10ΔT (i.e., at T30), the image data B1˜B20 of the blue sub-frame has been written into the sections I1˜I20. Accordingly, to display an original frame (i.e., to display its red, green, and blue sub-frames), total 30ΔT (i.e., T0˜T30) is required which is about 0.55 ms×30≈16.6 ms and is marked as the “current frame” in FIG. 4. After T30, it is the frame time of the next frame. Take the sections I1 and I20 as example, they are scanned and the image data R1 and R20 are written during T0˜T1. Then, the red LEDs in the corresponding LED sets cannot be turned on until the liquid crystal molecules complete the response time and reach the target grey levels. If As the response time of liquid crystal molecules is about 3 ms, it has to wait 6ΔT (0.55 ms×6=3.3 ms) and then turns on the red LEDs in the LED sets behind the sections I1 and I20 at T6. The red LEDs remain on until T9, when the image data G1 and G20 of the green sub-frame begins to be written into the sections I1 and I20. In other words, during the 5.55 ms where a section displays a sub-frame, the backlight LEDs corresponding to the section and the sub-frame is turned on for 1.65 ms (T7˜T10), which is long enough to accurately present the color and brightness of the image of the section. Please note that LEDs also have a response time but it is in the range of nano-seconds and therefore is ignored here. How the discontinuity problem is resolved by the present invention can also be seen from FIG. 4. During T15˜T18, the two sections I10 and I11 at the interface of the scanning areas S1 and S2 contains red image data R10 and R11, and the two sections' corresponding red LEDs are turned on as well. In other words, the image data of a same sub-frame is presented continuously across the interface of the scanning areas S1 and S2. Therefore, the discontinuity problem arising from the display of different color images of different sub-frames simultaneously across the interface of scanning areas is effectively resolved. Please note that, during T7˜T10, the image data R1 and R20 of sections I1 and I20 are illuminated while the image data B8−˜B13− of the previous blue sub-frame in sections I8˜I13 are also illuminated. The illuminated data belongs two different frames and is in different colors. However, as there are 54×7=378 scan lines between I1 and I8 and between I13 and I20, the human eye wouldn't develop discontinuous feeling from such a distance. Accordingly, as can be seen from FIG. 4, the discontinuity problem of dynamic images can be effectively resolved by time-division scanning of sub-frames in opposite directions.
As also shown in FIG. 4, during T10˜T11, the red image data R2 of the section I2 is illuminated while the green image data G1 is scanned into the section I1. Ideally, the light from the LED set behind the section I2 wouldn't leak to illuminate the section I1. However, in reality, the light for illuminating a section would inevitably illuminate a number of scan lines in adjacent sections. This would cause incorrect image presentation (e.g., the grey levels of some pixels are determined by green image data while they are illuminated by red light). To resolve this light leakage problem, one way is to more precisely control the scanning time and when to turn on the LEDs by using a time unit of finer granularity.
For example, if the time unit ΔT′ is reduced to ⅓ΔT so that ΔT′=0.183 ms, a frame time would take 90ΔT′, each sub-frame time would take 30ΔT′, and the scanning time of each section is 3ΔT′. Therefore, the timing diagram of FIG. 4 would be extended three folds and a portion of it is shown in FIG. 5. As illustrated, after the first ΔT′, only one third of the scan lines of a section are scanned and the section is denoted as Rn1/3, Gn1/3 or Bn1/3; after the second ΔT′, two third of the scan lines of the section are scanned and the section is denoted as Rn2/3, Gn2/3, or Bn2/3; and after the third ΔT′, all scan lines of the section are scanned and the section is Rn, Gn, or Bn.
As illustrated, when T1 is reached, Rn1/3 is scanned. Similarly, when T2, T3 are reached, Rn2/3 and Rn are scanned respectively. Since the liquid crystal molecules would need 3 ms response time to reach target grey levels, the red LEDs of the LED set behind the section I1 are turned on after waiting 17ΔT′ (0.183 ms×17=3.1 ms) until T20 for the liquid crystal molecules to completely respond. In the previous embodiment where ΔT=0.55 ms, the waiting time is 6ΔT (3.3 ms) and some unnecessary waiting time is wasted. In the present embodiment where ΔT′=0.183 ms, the waiting time is 17 ΔT′ (3.1 ms) and less time is wasted. The scenario applies to the other sections accordingly. For example, the section I2 is scanned from T3 after the section I1 has completed scanning. Then, after T6 where the section I2 has completed scanning, another 17ΔT′ are required to wait for the liquid crystal molecules to respond until T23 where the red LEDs of the LED set behind the section I2 is turned on.
Following the previous embodiment, the red LEDs of the LED sets behind the sections I1 and I2 should remain on until T30 and T33 respectively, where the green image data G1 and G2 begin to be written. However, as shown in FIG. 6, the present embodiment turns off the red LEDs for the sections I1 and I2 prematurely at T29 and T32 respectively. During T29˜T30, the red LEDs for the section I2 is also turned on while the red LEDs for the section I1 is already turned off. During T30˜T31, the red LEDs for the section I2 remains on while the green image data Gn1/3 is scanned into the section I1. During T31˜T32, the red LEDs for the section I2 remains on while the green image data Gn2/3 is scanned into the section I1. As can be seen from FIG. 5, as long as the light leakage does not go beyond one third of the scan lines of the adjacent sections, the light leakage wouldn't produce incorrect image presentation. For example, during T30˜T32, the red light leaked from the section I2 to the section I1 wouldn't illuminate the green image data already scanned into the first two third of the scan lines of the section I1. On the contrary, as the last one third of the scan lines of the section I1 still contains red image data, the light leakage actually enhance the brightness of the image. Then, during T32˜T33, the green image data begins to be scanned into the last one third of the scan lines of the section I1, the red LEDs for the section I2 therefore have to turned off earlier.
FIG. 6 is a schematic diagram showing the brightness distribution across the sections of scan lines according to the present invention. As illustrated, the brightness of the backlight for the section I1 drops linearly to 50% at the border interfacing an adjacent section and further drops to zero when it crosses the border for a distance Δ. As mentioned earlier, Δ should be as small as possible but it cannot be completely eliminated. However, when the backlight LEDs for two adjacent sections are both turned on such as during T23˜T30, the brightness at the border is compensated by the leakage from the adjacent section and therefore is still 100%.
FIGS. 7
a, 7b, and 7c are schematic diagrams showing the scanning sequence according to a second embodiment of the present invention. As shown in FIG. 7a, the panel is partitioned horizontally parallel to the scan lines into three scanning areas S1, S2, and S3, each having 360 scan lines. The scan lines of the scanning areas S1, S2, and S3 are referred to as the scan lines 1˜360, 361˜720, and 721˜1080, respectively. For each scanning area, its scan lines are further partitioned horizontally parallel to the scan lines into ten sections. The sections of the scanning areas S1, S2, and S3 are denoted as I1˜I10, I11˜I20, and I21˜I30, respectively. According to the present invention, the line-by-line scanning directions of any two adjacent scanning areas are either facing each other (i.e., towards their interfacing border) or opposite to each other (i.e., away from their interfacing border). Therefore, the present embodiment can have two scanning sequences as shown in FIGS. 7b and 7c respectively. In FIG. 7b, the scanning directions of the scanning areas S1 and S2 are face-to-face while the scanning directions of the scanning areas S2 and S3 are back-to-back. In FIG. 7c, the scanning directions of the scanning areas S1 and S2 are back-to-back while the scanning directions of the scanning areas S2 and S3 are face-to-face.
As there are three scanning areas in the present embodiment, no matter which scanning sequence of FIG. 7b or 7c is adopted, three scan lines have to be scanned simultaneously. Therefore, for example, the scan lines 1, 720, and 721 are connected to the same gate line and total 1080/3=360 gate lines are required. On the other hand, when three scan lines are scanned at the same time, the image data has to be written into the 1920 pixels of each of the three scan lines simultaneously. The present embodiment therefore requires 1920×3=5760 data lines. As the simultaneous scanning of the three scanning areas has to be finished within the 5.55-ms sub-frame time, the scanning time for each scan line is 5.55 ms/360≈15.4 μs. This speed is achievable by the existing technologies. Each section has 36 scan lines and the scanning time for each section is 15.4 μs×36=0.55 ms. With the 3-ms liquid crystal response time, there is about 2 ms left to turn on the LEDs.
The present embodiment has a ΔT=0.55 ms and each section needs 10ΔT to display a sub-frame. Within the 10ΔT, the first ΔT is for scanning image data into the section, six ΔTs (6×0.55 ms=3.3 ms) are for liquid crystal molecules to fully respond, and three ΔTs are for illuminating the section. In addition, when the scan lines near the border between adjacent scanning areas are scanned according to the present invention, they contain image data of a same sub-frame and therefore there is no discontinuity phenomenon. Similarly, if the time unit ΔT′ is reduced to ⅓ΔT (0.55 ms/3≈0.183 μs), each section needs 30ΔT′ to display a sub-frame. Within the 30ΔT′, the first three ΔT's are for scanning image data into the section, 17ΔT's (17×0.183 μs=3.1 ms) are for liquid crystal molecules to fully respond, nine ΔT's are for illuminating the section, and the last ΔT′ is as a buffer to prevent light leakage problem.
FIGS. 8
a, 8b, and 8c are schematic diagrams showing the scanning sequence according to a third embodiment of the present invention. As shown in FIG. 8a, the panel is partitioned horizontally parallel to the scan lines into four scanning areas S1, S2, S3, and S4, each having 270 scan lines. The scan lines of the scanning areas S1, S2, S3, and S4 are referred to as the scan lines 1˜270, 271˜540, 541˜810, and 811˜1080, respectively. For each scanning area, its scan lines are further partitioned horizontally parallel to the scan lines into ten sections. The sections of the scanning areas S1, S2, S3, and S4 are denoted as I1˜I10, I11˜I20, I21˜I30, and I31˜I40, respectively. The present embodiment can have two scanning sequences as shown in FIGS. 8b and 8c respectively. In FIG. 8b, the scanning directions of the scanning areas S1 and S2 are face-to-face while the scanning directions of the scanning areas S3 and S4 are also face-to-face. In FIG. 8c, the scanning directions of the scanning areas S1 and S2 are back-to-back while the scanning directions of the scanning areas S3 and S4 are also back-to-back. The present embodiment requires 1080/4=270 gate lines and 1920×4=7680 data lines.
As the simultaneous scanning of the four scanning areas has to be finished within the 5.55-ms sub-frame time, the scanning time for each scan line is 5.55 ms/270≈20.57 μs. This speed is easily achievable by the existing technologies. Each section has 27 scan lines and the scanning time for each section is 20.57 μs×27=0.55 ms. With the 3-ms liquid crystal response time, there is about 2 ms left to turn on the LEDs. Again, the present embodiment has a ΔT=0.55 ms and each section needs 10ΔT to display a sub-frame. Within the 10ΔT, the first ΔT is for scanning image data into the section, six ΔTs (6×0.55 ms=3.3 ms) are for liquid crystal molecules to fully respond, and three ΔTs are for illuminating the section. Similarly, when the scan lines near the border between adjacent scanning areas (e.g., the scan lines 540 and 541 of FIG. 8b, and the scan lines 270, 271, and 810, 811 of FIG. 8c) are scanned according to the present invention, they contain image data of a same sub-frame and therefore there is no discontinuity phenomenon. Again, if the time unit ΔT′ is reduced to a smaller granularity, more accurate timing control can be achieved to prevent light leakage problem.
FIG. 9 is a table summarizing the features of various embodiments of the 1920×1080 LCD device according to the present invention. It can be seen from the table that, if there are more scanning areas, less gate lines but more data lines would be required. In addition, the scanning speed can be slower and therefore easier to achieve as there are more scanning areas. Please note that, even though the foregoing embodiments all have the scanning areas partitioned into ten sections, the present invention can be applied to scenarios where the scanning areas are partitioned into an appropriate number M of sections where M is any integer greater than or equal to one (when M=1, there is no partition into sections). Similarly, the present invention is not limited to the partitioning of two, three, or four scanning areas as described. The present invention can be applied to scenarios where the panel is partitioned into an appropriate number N of scanning areas where N is any integer greater than or equal to two. In contrast to the U.S. Pat. No. 6,448,951 which requires the number of sections to be a multiple of three and greater than or equal to six, the present invention allows the designer of a LCD device to strike a balance between speed and cost flexibly.
From the foregoing description, a person skilled in the related arts can easily apply the present invention's partition of scanning areas and the opposite directional scanning sequence to various LCD devices, regardless of whether they have color filter or not, whether the backlight source is based on red, green, and blue LEDs, or based on white-light LEDs, or based on cold cathode fluorescent lamps (CCFLs), or whether the frame is separated into sub-frames or not. The respective details are therefore omitted here.
Although the present invention has been described with reference to the preferred embodiments, it will be understood that the invention is not limited to the details described thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.
Patent Application
20080001906
