The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
Embodiments of the present invention will be described hereinafter with reference to accompanying drawings. Note that in descriptions of the embodiments and modifications described hereinafter, the same reference numerals are used for the same components and descriptions thereof are omitted or simplified.
As is apparent from
According to the embodiments of the invention, in a case where a gray-scale level is changed to a halftone, a response speed of liquid crystal is improved by performing pulse-surface-area modulation using divided pixels without performing overdrive processing.
As shown in
Here, a configuration of the pixel unit A1 will be described in detail. Note that each of the pixels according to the embodiment of the invention includes at least two adjacent subpixels as a group. Description will be made hereinafter for each of the pixels including two subpixels, that is, a first subpixel 20 and a second subpixel 30.
The first subpixel 20 includes, as shown in
The switching device 24 is connected to the pixel electrode 21 through a first terminal (a source terminal or a drain terminal), is connected to a scanning line Y1a through a second terminal (a gate terminal), and is connected to a data line X1 through a third terminal (a drain terminal or a source terminal).
The second subpixel 30 includes, as shown in
The switching device 34 is connected to the pixel electrode 31 through a first terminal (a source terminal or a drain terminal), is connected to a scanning line Y1b through a second terminal (a gate terminal), and is connected to the data line X1 through a third terminal (a drain terminal or a source terminal) similarly to the third terminal of the switching device 24.
Accordingly, for example, in one horizontal scanning period, switching between the scanning lines Y from one to another is selectively performed so that low-gray-scale-level display is achieved using the first subpixel 20 and high-gray-scale-level display is achieved using the second subpixel 30 whereby pulse-surface-area modulation is performed and halftone display is achieved.
Furthermore, in the electro-optical device 1 according to this embodiment of the invention, at least two subpixels are included in a group, and the scanning lines Y1a and Y1b which correspond to the subpixels and between which switching is successively performed in one horizontal scanning period are set as a pair of scanning lines. In this condition, switching between the scanning line Y1a and the scanning line Y1b is performed every horizontal scanning period.
The scanning line driving circuit 40 supplies selection voltages successively to the scanning lines Y so that the switching device 24 or the switching device 34 is brought into a conduction state.
The common electrode driving circuit 41 supplies a first voltage and a second voltage which has a potential higher than that of the first voltage to the common electrodes 22 and 32 alternately every one horizontal period.
The data line driving circuit 42 supplies image signals to the data lines X. By this, an image voltage is supplied to the pixel electrode 21 or 31 in accordance with one of the image signals through the switching device 24 or 34 which is in an on-state.
Here, the data line driving circuit 42 performs positive-polarity writing in which image signals which have potentials higher than those of the common electrodes 22 and 32 are supplied to the data lines X and image voltages generated on the basis of the image signals having the positive polarities are written to the pixel electrodes 21 and 31, and performs negative-polarity writing in which image signals which have potentials lower than those of the common electrodes 22 and 32 are supplied to the data lines X and image voltages generated on the basis of the image signals having the negative polarities are written to the pixel electrodes 21 and 31. The positive-polarity writing and the negative-polarity writing are alternately performed every horizontal scanning line.
The gray-scale-level detection unit 43 detects gray-scale levels of input image signals and supplies results of the detection to the determination unit 44. Note that in this embodiment, although the gray-scale-level detection unit 43 detects gray-scale levels of the image signals in 256 gray-scale levels, the present invention is not limited to this.
The determination unit 44 determines, for each of the gray-scale levels of the image signals supplied from the gray-scale-level detection unit 43, whether the gray-scale level is within a predetermined range (for example, a range from 64 to 128) considered to be a halftone. When the determination is affirmative, the determination unit 44 controls the scanning line driving circuit 40 and the data line driving circuit 42 as needed to display an image using pulse-surface-area modulation. On the other hand, when the determination is negative, since it is not necessary to perform the pulse-surface-area modulation, the determination unit 44 controls the scanning line driving circuit 40 and the data line driving circuit 42 as needed so that normal gray-scale display is performed.
Here, operations of the scanning line driving circuit 40 and the data line driving circuit 42 performed in a case where it is determined that a gray-scale level, which is detected using the gray-scale-level detection unit 43 which is controlled by the determination unit 44, is within a range considered to be a halftone will be described with reference to
As shown in
The data line driving circuit 42 modulates the image signals to be supplied to the data lines X so that pulse-surface-area modulation is performed in low-gray-scale-level display and high-gray-scale-level display entirely in each of the pixels constituted by pairs of pixel electrodes ((D) of
For example, if a detected gray-scale level is “64”, an image signal is modulated so that the first subpixel 20 performs display with a gray-scale level of “0” and the second subpixel 30 performs display with a gray-scale level of “192”. As described above, since the pulse-surface-area modulation is performed, a response speed is improved while the entire pixel performs display with a gray-scale level of “64”. Note that, in this example, the response speed is 44 msec.
On the other hand, in a case where it is determined that a gray-scale level, which is detected using the gray-scale-level detection unit 43 which is controlled by the determination unit 44, is out of a range considered to be a halftone, that is, it is determined that the detected gray-scale level is a low gray-scale level or a high-gray-scale level, for example, the image signal may be modulated so that the first subpixel 20 and the second subpixel 30 perform display with the same gray-scale level. Alternatively, one of the pixel electrodes included in the first subpixel 20 and the second subpixel 30 may be controlled so as not to be driven.
As described above, since the electro-optical device 1 according to the embodiment of the invention causes each of the pixels to perform display using a pair of subpixels, halftone display is achieved without performing overdrive processing. Accordingly, since a memory necessary for the overdrive processing can be eliminated, a size of the entire device and production cost thereof can be reduced, and a response speed of the liquid crystal can be improved. Furthermore, the amount of electric power required for the overdrive processing can be reduced.
Note that the first subpixel 20 and the second subpixel 30 may be configured in a different area ratio.
A second embodiment according to the invention will now be described. As shown in
Here, a configuration of the pixel unit A2 will be described in detail. Note that each of the pixels according to the embodiment of the invention includes at least two adjacent subpixels as a group. Description will be made hereinafter for each of the pixels including two subpixels, that is, a first subpixel 60 and a second subpixel 61.
The first subpixel 60 includes, as shown in
The first switching device 65 is connected to the pixel electrode 62 through a first terminal (a source terminal or a drain terminal), is connected to a scanning line Y1 through a second terminal (a gate terminal), and is connected to a data line X1 through a third terminal (a drain terminal or a source terminal).
The second subpixel 61 includes, as shown in
The second switching device 69 is connected to the pixel electrode 66 through a first terminal (a source terminal or a drain terminal), is connected to a corresponding one of the control lines W through a second terminal (a gate terminal), and is connected to the first terminal of the first switching device 65 through a third terminal (a drain terminal or a source terminal).
The third switching device 70 is connected to the pixel electrode 66 through a first terminal (a source terminal or a drain terminal), is connected to a corresponding one of the control lines W through a second terminal (a gate terminal), and is connected to the common electrode 67 through a third terminal (a drain terminal or a source terminal).
Accordingly, for example, switching between the second switching device 69 and the third switching device 70 is selectively performed so that low-gray-scale-level display is achieved using the first subpixel 60 and high gray-scale-level display is achieved using the second subpixel 61 whereby pulse-surface-area modulation is performed and halftone display is achieved.
The gray-scale-level detection unit 80 detects gray-scale levels of input image signals and supplies results of the detection to the determination unit 81. Note that in this embodiment, although the gray-scale-level detection unit 80 detects gray-scale levels of the image signals in 256 gray-scale levels, the present invention is not limited to this.
The determination unit 81 determines, for each of the gray-scale levels of the image signals supplied from the gray-scale-level detection unit 80, whether the gray-scale level is within a predetermined range (for example, a range from 64 to 128) considered to be a halftone.
The switching unit 82 controls the second switching device 69 and the third switching device 70 to be turned on or off in accordance with a result of the determination output from the determination unit 81.
Specifically, in a case where the determination unit 81 determines that a gray-scale level detected using the gray-scale-level detection unit 80 is within the predetermined range considered to be a halftone, the switching unit 82 supplies a first switching signal to the corresponding one of the control lines W so that the second switching device 69 is turned off and the third switching device 70 is turned on in one horizontal scanning period. On the other hand, in a case where the determination unit 81 determines that a gray-scale level detected using the gray-scale-level detection unit 80 is out of the predetermined range considered to be a halftone, the switching unit 82 supplies a second switching signal to the corresponding one of the control lines W so that the second switching device 69 is turned on and the third switching device 70 is turned off in one horizontal scanning period.
The second switching device 69 is formed of an N-channel transistor and the third switching device 70 is formed of a P-channel transistor. Accordingly, when a low-level signal is supplied as the first switching signal to the corresponding one of the control lines W, the second switching device 69 is turned off whereas the third switching device 70 is turned on. On the other hand, when a high-level signal is supplied as the first switching signal to the corresponding one of the control lines W, the second switching device 69 is turned on whereas the third switching device 70 is turned off. The second switching device 69 may be formed of a P-channel transistor and the third switching device 70 may be formed of an N-channel transistor.
Referring to
In a case where the determination unit 81 determines that the gray-scale level detected using the gray-scale-level detection unit 80 is within the predetermined range considered to be a halftone, that is, it is determined that the detected gray-scale level is an intermediate gray-scale level, the switching unit 82 supplies a first switching signal to corresponding one of the control lines W so that the second switching device 69 is turned off and the third switching device 70 is turned on whereby pulse-surface-area modulation is performed. The second subpixel 61 has potentials at both ends the same as those applied to the common electrodes 63 and 67 resulting in no voltage being applied to the second subpixel 61. On the other hand, in the first subpixel 60, a predetermined potential is applied to the liquid crystal in accordance with a voltage supplied from the corresponding one of the data lines X through the first switching device 65. Accordingly, halftone display is realized by pulse-surface-area modulation using the first subpixel 60 and the second subpixel 61.
On the other hand, in a case where the determination unit 81 determines that the gray-scale level detected using the gray-scale-level detection unit 80 is out of the predetermined range considered to be a halftone, that is, it is determined that the detected gray-scale level is a low gray-scale level or a high-gray-scale level, since it is not necessary to perform pulse-surface-area modulation, the switching unit 82 supplies a second switching signal to the corresponding one of the control lines W so that the second switching device 69 is turned on and the third switching device 70 is turned off. Accordingly, since the same potentials are applied to the first subpixel 60 and the second subpixel 61, normal gray-scale display is performed.
As described above, since the electro-optical device 2 according to the embodiment of the invention causes each of the pixels to perform display using the first subpixel 60 and the second subpixel 61, halftone display is achieved without performing overdrive processing. Accordingly, since a memory necessary for the overdrive processing can be eliminated, a size of the entire device and production cost thereof can be reduced, and a response speed of the liquid crystal can be improved. Furthermore, the amount of electric power required for the overdrive processing can be reduced.
Note that the first subpixel 60 and the second subpixel 61 may be configured in a different area ratio.
In the above-described first and second embodiments, although each of the pixels is constituted by two subpixels, the present invention is not limited to this. Alternatively, each of the pixels may be constituted by three or more subpixels. Furthermore, image signals may be supplied to subpixels at the same time or at different times. Moreover, in the above-described first and second embodiments, although an MVA method is employed as an example of a method for driving the liquid crystal, an ECB (electrically controlled birefringence) method may be employed. Here, the ECB method is a method in which a voltage to be applied to a liquid crystal layer is changed to change orientation of liquid crystal molecules, and change of birefringent property of the liquid crystal layer which occurs as a result of the change of the orientation of the liquid crystal molecules is detected using a pair of polarizing plates. The ECB method is applied to color display.
An electronic apparatus to which the electro-optical device 1 or 2 according to the above-described embodiments is applied will be described.
Examples of such an electronic apparatus to which the electro-optical device 1 or 2 is applicable include, in addition to the apparatus shown in
The entire disclosure of Japanese Patent Application No. 2006-216511, filed Aug. 9, 2006 is expressly incorporated by reference herein.
Number | Date | Country | Kind |
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2006-216511 | Aug 2006 | JP | national |