This non-provisional application claims priority of China patent application No. 202210102253.4, filed on 27th Jan., 2022, included herein by reference in its entirety.
The invention relates to a display method, and in particular, to a display device for reducing motion blur and a control method thereof.
A liquid crystal display (LCD) is a flat display device that uses a backlight to display images. In the LCD, liquid crystals require a finite amount of time to perform phase transitions. If the backlight is turned on continuously, and one or more moving objects are present in consecutive images, the user will see the process of phase transitions of the liquid crystals, resulting in image artifact or motion blur, and degrading user experience while viewing a video. Therefore, how to reduce the motion blur in images on the display device remains a challenging issue in the related display field.
According to an embodiment of the invention, a control method for use in a display device includes obtaining a duty cycle of a backlight control signal of controlling a backlight source of the display device, and adjusting a starting time of a pulse in the backlight control signal according to at least the duty cycle.
According to another embodiment of the invention, a display device includes a backlight source and a controller. The controller is coupled to the backlight source, and is used to obtain a duty cycle of a backlight control signal, and adjust a starting time of a pulse in the backlight control signal according to at least the duty cycle. The backlight control signal is used to control the backlight source.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
The display system 1 includes a display device 10 and an input device 12. The display device 10 includes a display panel 102, a backlight source 104 and a controller 106. The display panel 102 may be disposed on the backlight source 104. In some embodiments, other optical elements such as a light guide plate, a diffuser, a brightness enhancement film, and a polarizer may be disposed between the display panel 102 and the backlight source 104. The controller 106 may be coupled to the input device 12, the display panel 102 and the backlight source 104.
The controller 106 may be a microcontroller or other control circuits. The controller 106 may receive a frame signal and a synchronization signal from a display card or other video sources, and transmit a video frame signal VD to the display panel 102 and a backlight control signal BL to the backlight source 104. The synchronization signal may be a vertical synchronization signal. The display panel 102 may update the screen from top to bottom and row by row according to the video frame signal VD, and the backlight source 104 may be controlled by the backlight control signal BL to emit light and illuminate the display panel 102 to display the image on the display panel 102. The luminance of the backlight source 104 may be controlled by pulse width modulation, that is, controlled by the duty cycle of the backlight control signal BL. The user may enter or alter the duty cycle of the backlight control signal BL via the input device 12. The input device 12 may be implemented by a combination of software, firmware and hardware, and may be integrated into the display device 10 or may operate separately from the display device 10. In some embodiments, the input device 12 may be a touch screen, a keyboard, a mouse, a key or other input devices. The user may use the input device 12 to select a level of backlight or adjust the backlight control slider to adjust the duty cycle of the backlight control signal BL. The duty cycle of the backlight control signal BL may be stored in an internal memory or an external memory of the controller 106. The controller 106 may obtain the duty cycle of the backlight control signal BL from the internal memory or the external memory thereof, and adjust a starting time of the pulse of the backlight control signal BL according to at least the duty cycle, so as to reduce the motion blur.
The display panel 102 may be a liquid crystal panel with a relatively slow transition of liquid crystals, such as an in-plane-switching panel or a vertical alignment panel. Since the phase transitions of the liquid crystals of the display panel 102 are relatively slow, all the liquid crystals may be rotating when the screen 20 is updated, and the data of portion C of the previous screen 20 may be overlapping with the current screen 20 due to the phase transitions of the overdriven liquid crystals, resulting in motion blurs in the portion C of the previous picture 20 and the portion A of the current picture 20. For example, it may take 2 milliseconds (ms) to overdrive the liquid crystals to perform phase transitions, the number of rows in the entire area of the display device 10 may be 1215, the update rate may be 240 Hz, and the length of the overdriven liquid crystal transition may be 583 rows (=0.002/(240*1215)−1), and consequently, the last row of the portion C of the previous screen 20 will be overlapping with the portion A of the current screen 20.
Step S402: Obtain a duty cycle of the backlight control signal BL;
Step S404: Adjust a starting time of a pulse of the backlight control signal BL according to at least the duty cycle.
In Step 404, when the duty cycle increases, the controller 106 may bring forward the starting time of the pulse of the backlight control signal BL, and when the duty cycle decreases, the controller 106 may postpone the starting time of the pulse of the backlight control signal BL. For example, if the duty cycle is 25% and the number of rows in the entire area is 1215, the starting time of the pulse of the backlight control signal BL may fall in the period of the display device 10 updating 24.2% of the number of rows in the entire area, and the backlight source 104 may be turned on when the display panel 102 updates the 294th row (=1215*0.242). If the duty cycle is 30%, the starting time of the pulse of the backlight control signal BL may fall in the period of the display device 10 updating 19.2% of the number of rows in the entire area, and the backlight source 104 may be turned on when the display panel 102 updates the 233rd row (=1215*0.192). If the duty cycle is 22%, the starting time of the pulse of the backlight control signal BL may fall in the period of the display device 10 updating 27% of the number of rows in the entire area, and the backlight source 104 may be turned on when the display panel 102 updates the 328th row (=1215*0.27). Therefore, when the duty cycle is increased from 25% to 30%, the starting time of the pulse of the backlight control signal BL may be brought forward from the 294th row to the 233rd row; and when the duty cycle is reduced from 25% to 22%, the starting time of the pulse of the backlight control signal BL may be postponed from the 294th row to the 328th row. In some embodiments, the controller 106 may adjust the starting time of the pulse of the backlight control signal BL according to the duty cycle, the number of rows in the entire area of the display device 10, the number of rows in the vertical front porch of the display device 10, and the number of rows in the active area of the display device 10, and the actual implementation thereof may be shown in
Step S502: Generate a threshold Th of the display device 10;
Step S504: Adjust the starting time Ts of the pulse of the backlight control signal BL according to the duty cycle Y %, Vtotal, Vfront, and Vactive;
Step S506: Determine whether the starting time Ts is less than 0? if so, proceed to Step S508; if not, go to Step S510;
Step S508: Update the starting time Ts to 0; exit Step S404.
Step S510: Determine whether the starting time Ts is greater than the threshold Th? If so, go to Step S512; if not, exit Step S404.
Step S512: Update the starting time Ts to the threshold Th; exit Step S404.
In Step 502, the controller 106 generates the threshold Th of the display device 10 according to Equation (1) as follows:
Th=((Vactive/4+Vfront)/(Vtotal/100)) Equation (1)
where Th is the threshold;
Vactive is the number of rows in the active area of the display device 10;
Vfront is the number of rows in the vertical front porch of the display device 10; and
Vtotal is the number of rows in the entire area of the display device 10.
For example, the number of rows Vactive in the active area may be 1080, the number of rows in the vertical front porch Vfront may be 57, the number of rows in the entire area may be 1215, and the threshold Th may be approximately 27% (=1080/4+57)/(1215/100)).
In Step 504, the controller 106 generates the threshold Th of the display device 10 according to Equation (2) as follows:
Ts=Th−((Y%*Vtotal−(Vactive/4))/(Vtotal/100)) Equation (2)
Wherein Ts is the starting time of the pulse of the backlight control signal BL;
Th is the threshold;
Y % is the duty cycle;
Vtotal is the quantity of rows in the entire area of the display device 10; and
Vactive is the number of rows in the active area of the display device.
For example, the threshold Th may be 27%, the duty cycle may be 25%, the number of rows in the active area Vactive may be 1080, the number of rows in the vertical front porch may be 57, and the number of rows in the entire area may be 1215, and the starting time Ts of the pulse of the backlight control signal BL may be 24.2%(=2740.25*1215-1080/4)/(1215/100))). Table 1 shows the duty cycles Y % and the starting times Ts of the pulse of the backlight control signal BL computed according to Equation (2). The starting time Ts is expressed in percentage of the number of rows in the entire area. For example, when the duty cycle Y % is 25%, the starting time Ts is the 294th row (=1215*0.242) in the entire area.
In Step 506, if the starting time Ts is less than 0, the pulse of the backlight control signal BL starts from the previous screen 20. Since the earliest time the pulse of the backlight control signal BL may start is the beginning of the current screen 20, if the starting time Ts is less than 0, the controller 106 updates the starting time Ts to 0 (Step 508) to set the pulse of the backlight control signal BL to start from the first row of the entire area, and Step S404 is exited. For example, in Table 1, when the duty cycle Y % is 56%, the starting time Ts is less than 0 (−6.8<0), and thus, the controller 106 updates the starting time Ts to 0. If the starting time Ts is greater than 0, the pulse of the backlight control signal BL will not start until the starting time Ts is reached.
In Step 510, if the starting time Ts is greater than the threshold Th, the pulse of the backlight control signal BL will start after ¼ of the screen 20. However, since the preferred starting time of the pulse of the backlight control signal BL falls in ¼ of the screen 20, the controller 106 updates the starting time Ts to the threshold Th (Step 512), so that the pulse of the backlight control signal BL starts from the position of ¼ of the screen 20. For example, in Table 1, when the duty cycle If the ratio Y % is 10%, the starting time Ts is greater than the threshold Th (39.2<27), and the controller 106 updates the starting time Ts to 27%. And Step S404 is exited. If the starting time Ts is less than the threshold Th, the optimal starting time of the pulse of the backlight control signal BL falls in the period of the display panel 102 updating ¼ of the screen 20, and Step S404 is exited. For example, in Table 1, when the duty cycle Y % is 25%, the starting time Ts is less than the threshold Th (24.2<27), and thus, the starting time Ts is maintained at 24.2%.
In some embodiments, Steps S506 and S508 and Steps S510 and S512 may also be swapped in place, so that the comparison between the starting time Ts and the threshold Th is performed first, and then the comparison between the starting time Ts and 0 is performed.
At Time t1, the video frame signal VD is disabled, and the blanking interval VB1 begins. Between Times t2 and t3, the controller 106 receives the synchronization signal VSYNC. The interval between Times t1 and t2 is referred to as the VFP interval. The starting time Ts is measured from the end of the pulse in the synchronization signal VSYNC (t3). At Time t4, the video frame signal VD is enabled, and the active video frame VA1 starts. The interval between Times t3 and t4 is referred to as the VBP interval. At Time t5, the display panel 102 has updated to 27% of the number of rows in the entire area, and the pulse of the backlight control signal BL starts. At Time t6, the display panel 102 has updated to 37% of the number of rows in the entire area, and the pulse of the backlight control signal BL ends. The interval between Time t5 and Time t6 is referred to as the ON time Ton of the pulse of the backlight control signal BL. At Time t7, the frame data B1 ends. At Time t8, the active video frame VA1 ends. At Time t9, the active video frame VA2 starts, and at Time t10, the pulse of the backlight control signal BL starts again. The interval between Time t6 and Time t10 is referred to as the OFF time Toff of the pulse of the backlight control signal BL.
Since the pulse of the backlight control signal BL starts at ¼ of the screen 20 and ends before ½ of the screen 20, the level of blurriness of the portions A and C of the screen 20 are similar and the image in the portion B is sharper, thereby reducing the motion blur.
Since the pulse of the backlight control signal BL starts at the first row of the entire area and ends at ½ of the screen 20, the images in the portions A and C of the screen 20 are blurred and the image in the portion B is sharper, thereby reducing the motion blur.
While the optimal time for turning on the backlight in the embodiment is set at the period of updating the upper half of the screen, those skilled in the art may also set the time for turning on the backlight at the period of updating other areas of the screen as required according to the duty cycle of the backlight control signal BL, so as to sharpen the preset location.
The embodiments in
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
Number | Date | Country | Kind |
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202210102253.4 | Jan 2022 | CN | national |