1. Field of the Invention
The invention relates in general to the method of display by sub-frame driving, and more particularly to the method of display on a monitor by sub-frame driving.
2. Description of the Related Art
With the improvement and innovation of science and technology, the development of display technology changes rapidly and makes progress at a tremendous pace. The traditional CRT (Cathode Ray Tube) display has gradually dropped out the display market due to its large volume and serious radiation and is gradually replaced by LCD (Liquid Crystal Display), OLED (Organic Light Emitter Diode), or PDP (Plasma Display Panel), which are thin and have low radiation, low power consumption.
The frame data input to the display has two parts—pixel data and display timings. A driving voltage is determined according to the pixel data, and then the brightness of a pixel is determined according to the driving voltage. In addition to the pixel data, the frame data include a set of display timings, which have three parameters. The three parameters are Hs (Horizontal Synchronal signal), Vs (Vertical Synchronal signal), and CK (pixel clock). CK (pixel clock) represents the number of the pixels per second, which determines the interval between the action of displaying colors of some pixel and that of the next pixel. When the pixel corresponding to the input pixel data is the last pixel in a row, Hs (Horizontal Synchronous signal) controls to display the first pixel in the next row. Therefore, Hs (Horizontal Synchronous signal) determines the number of the rows per second. When the pixel corresponding to the input pixel data is the pixel of the last column of the last row in the screen, Vs (Vertical Synchronous signal) controls to display the first pixel of the first row. Therefore, Vs (Vertical Synchronous signal) determines the number of the displayed frames per second.
Take an LCD monitor for example. The transparency of each pixel is changed according to the driving voltage Vd applied, and accordingly the brightness of the pixel is determined. According to the pixel data, a target driving voltage VD is determined to let the pixel achieve a target transparency TD. When the driving voltage Vd rises to the target driving voltage VD, the transparency of the pixel cannot achieve the target transparency TD in real time due to the slow response of the liquid crystal in the pixel of the LCD monitor.
A well-known method to speed up the response of the liquid crystal is to apply an over-drive voltage Vo, which is higher in magnitude than the desired target driving voltage VD.
However, it is not easy to control the magnitude of the over-drive voltage Vo. If the over-drive voltage Vo is too high, the transparency may exceed the target transparency TD; if the over-drive voltage Vo is too low, the response of the liquid crystal may not be fast enough.
It is therefore an object of the invention to provide a method of driving pixels to shorten the response time thereof.
The invention achieves the above-identified objects by providing a method of display by sub-frame driving on a monitor. The monitor has pixels arranged in an m*n array, where m and n are integers. The monitor receives a frame signal for displaying a frame for a frame period. The frame signal includes the pixel data for each of the pixels of the monitor. The frame period is divided into a first sub-frame period and a second sub-frame period. A first sub frame is displayed during the first sub-frame period, and a second sub frame is displayed during the second sub-frame period. The first sub frame corresponds to a first driving voltage, and the second sub frame corresponds to a second driving voltage. The first driving voltage and the second driving voltage for the pixel (i,j) are unequal, wherein 0<i≦m, 0<j≦n, i, and j are integers. The method comprises the steps of displaying the first sub-frame according to the first driving voltage and displaying the second sub-frame according to the second driving voltage.
Other objects, features, and advantages of the invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings.
The method of display by sub-frame driving according to this invention is used for displaying frames on a monitor. The monitor has pixels arranged in an m*n array, where m and n are integers. The monitor receives a frame signal for displaying a frame for a frame period. For example, if the refresh rate of the monitor is 60 Hz, the frame period is 1/60 second. The frame signal includes the pixel data for each of the pixels of the monitor. In this invention, the frame period is divided into k sub-frame periods, and a sub frame is displayed during each of the sub-frame period. In other words, a frame is displayed during k steps, and at each step a sub-frame is displayed for the corresponding sub-frame period. Each of the sub frames corresponds to a driving shift. Note that the sub-frame periods are not necessarily equal and k is an integer.
The preferred embodiment according to this invention takes LCD monitor for example. Each pixel of the LCD monitor includes liquid crystal, and the transparency of the liquid crystal is determined by a driving voltage. A frame period is divided into a first sub-frame period and a second sub-frame period. A frame is displayed in two steps: a first sub-frame is displayed during the first sub-frame period, and then a second sub-frame is displayed during the second sub-frame period. The first sub-frame corresponds to a first driving shift, and the second sub-frame corresponds to a second driving shift.
The method of displaying a frame by sub-frame driving includes the following steps. First, display the first sub frame for the first sub-frame period at time ts0. Then display the second sub frame for the second sub-frame period at time ts1.
While the first sub frame is displayed, the driving voltage is the over-drive voltage Vo generated from the target driving voltage VD, derived from the pixel data, plus the first driving shift. The first driving shift is larger than zero, and thus speeds up the response of the liquid crystal. While the second sub frame is displayed, the driving voltage is the target driving voltage VD, derived from the pixel data, plus the second driving shift. The second driving shift is zero in this embodiment for maintaining the transparency of the liquid crystal at the target transparency TD.
The above-mentioned embodiment controls the magnitude of the first sub-frame period and the first driving shift to speed up the response time, and then maintain the target transparency during the second sub-frame period. Accordingly, the control is simpler.
The invention is not limited to the two sub frames for a frame. More sub frames for a frame can be used.
The invention displays one frame at several steps. A sub frame is displayed during each step. Although the refresh rate increases if the number of the sub frames per frame increases, the polarity of the driving voltage for the sub frames of a frame remain the same. Accordingly, the power is saved.
Receiver component 605 is connected to a sub-frame determination component 610. Sub-frame determination component 610 divides the frame represented by the frame signal into a sequence of k sub-frames and the frame period into a sequence of k sub-frame periods. The parameter k is an integer, and in one embodiment, k=2. The sub-frame periods are not necessarily equal, though they may be.
Sub-frame determination component 610 is connected to a sub-frame target voltage component 620 and a sub-frame driving shift voltage component 625. Sub-frame target voltage component 620 determines a target driving voltage corresponding to the pixel data from the frame signal for each of the pixels (i,j) in a frame, and sub-frame driving shift voltage component 625 determines a driving shift voltage corresponding to each of the sub-frames for a frame. As explained above, the determined driving shift voltage may be a voltage that, when added to the target driving voltage, results in an overdrive voltage for the pixel. Also as explained above, the determined driving shift voltage may be zero.
Sub-frame target voltage component 620 and sub-frame driving shift voltage component 625 are connected to a sub-frame driving voltage component 630. Sub-frame driving voltage component 630 determines the driving voltage for each pixel(i,j) in a sub-frame based on the target driving voltage corresponding to the pixel data for each of the pixels (i,j) in a frame and the driving shift voltage corresponding to each of the sub-frames for a frame. In one embodiment, the driving voltage (i,j) is determined by adding the target driving voltage corresponding to the pixel data with the driving shift voltage corresponding to the sub-frame. The determined driving voltages for a given pixel (i,j) in two different sub-frames may be of the same polarity.
Sub-frame driving voltage component 630 is connected to a sub-frame display component 635, which is connected to a screen 640, such as an LCD screen, an OLED screen, or a PDP screen. Sub-frame display component 635 provides a signal for continuously displaying pixel data during the sequence of sub-frames for a frame, by applying the driving voltage (i,j) (determined by sub-frame driving voltage component 630) to each pixel (i,j) during the sequence of sub-frames that make up a frame. For example, if there are two subframes for a frame, sub-frame display component 635 provides a signal for continuously displaying pixel data for the first sub-frame during the first sub-frame period, then provides a signal for continuously displaying pixel data for the second sub-frame during the second sub-frame period. As is known in the art, the signal for displaying pixel data is typically an analog signal that may be produced by a DAC (digital-to-analog converter), an amplifier, or some combination of circuit elements.
Receiver 705 is connected to a divider 710. Divider 710 divides the frame represented by the frame signal into a sequence of k sub-frames and the frame period into a sequence of k sub-frame periods. The parameter k is an integer, and in one embodiment, k=2. The sub-frame periods are not necessarily equal, although they may be.
Divider 710 is connected to a sub-frame target voltage determiner 720 and a sub-frame driving shift voltage determiner 725. Sub-frame target voltage determiner 720 determines a target driving voltage corresponding to the pixel data from the frame signal for each of the pixels (i,j) in a frame, and sub-frame driving shift voltage determiner 725 determines a driving shift voltage corresponding to each of the sub-frames for the frame. As explained above, the determined driving shift voltage for a given pixel in a given sub-frame may be a voltage that, when added to the target driving voltage, results in an overdrive voltage for the pixel during the sub-frame's period. Furthermore, as also explained above, the determined driving shift voltage may be zero.
Sub-frame target voltage determiner 720 and sub-frame driving shift voltage determiner 725 are connected to a summer 730. Summer 730 determines the driving voltage for each pixel(i,j) in a sub-frame by adding the target driving voltage corresponding to the pixel data for each of the pixels (i,j) in a frame to the driving shift voltage corresponding to each of the sub-frames for a frame. The driving voltages output by summer 730 for a given pixel (i,j) in two different sub-frames may be of the same polarity.
Summer 730 is connected to a driving voltage generator 735, which is connected to a screen 740, such as an LCD screen, an OLED screen, or a PDP screen. Driving voltage generator 735 provides a signal for continuously displaying pixel data during the sequence of sub-frames for a frame, by supplying the driving voltage (i,j) (determined by summer 730) for each pixel (i,j) during the sequence of sub-frames that make up a frame. For example, if there are two subframes for a frame, driving voltage generator 735 generates a signal for continuously displaying pixel data for the first sub-frame during the first sub-frame period, then generates a signal for continuously displaying pixel data for the second sub-frame during the second sub-frame period. As is known in the art, the signal for displaying pixel data is typically an analog signal that may be produced by a DAC (digital-to-analog converter), an amplifier, or some combination of circuit elements.
As is known in the art, the exemplary devices, components, systems, and subsystems illustrated may be implemented in hardware, software, or a combination thereof. Furthermore, one of ordinary skill will now recognize that the exemplary devices, components, systems, and subsystems depicted may have parts added, deleted, replaced, or connected differently, yet remain within the scope of the invention.
While the invention has been described by way of example and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.
Number | Date | Country | Kind |
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90112165 A | May 2001 | TW | national |
This is a continuation of application Ser. No. 10/124,487, filed 18 Apr. 2002, now U.S. Pat. No. 6,870,530 and claims the benefit of Taiwan application Serial No. 90112165, filed May 21, 2001, both of which are incorporated herein by reference.
Number | Name | Date | Kind |
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6011606 | Ohe et al. | Jan 2000 | A |
6046716 | McKnight | Apr 2000 | A |
6157356 | Troutman | Dec 2000 | A |
6215466 | Yamazaki et al. | Apr 2001 | B1 |
6423385 | Kagawa et al. | Jul 2002 | B1 |
6587084 | Alymov et al. | Jul 2003 | B1 |
Number | Date | Country | |
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20050162416 A1 | Jul 2005 | US |
Number | Date | Country | |
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Parent | 10124487 | Apr 2002 | US |
Child | 11034918 | US |