CN113406817A

CN113406817A - System and method for measuring moving image response time of liquid crystal display

Info

Publication number: CN113406817A
Application number: CN202010181523.6A
Authority: CN
Inventors: 陈雍之; 林伟智; 魏瑞德; 陈柏安
Original assignee: Realtek Semiconductor Corp
Current assignee: Realtek Semiconductor Corp
Priority date: 2020-03-16
Filing date: 2020-03-16
Publication date: 2021-09-17

Abstract

The invention discloses a system and a method for measuring the moving image reaction time of a liquid crystal display. The method comprises the following steps: controlling the picture displayed by the display panel to switch among a plurality of different gray scales, and measuring the brightness change of the display panel when the display panel switches the gray scales so as to obtain at least one gray scale reaction time normalization curve; integrating the at least one gray scale reaction time normalization curve to obtain at least one motion image reaction time normalization curve; obtaining at least one time interval of at least one moving image response time normalization curve; and calculating the average value of the at least one time interval to obtain the moving image response time of the liquid crystal display.

Description

System and method for measuring moving image response time of liquid crystal display

Technical Field

The present invention relates to a system and method for measuring Motion Picture Response Time (MPRT) of a liquid crystal display, and more particularly, to a system and method for measuring Motion Picture Response Time of a liquid crystal display by measuring Gray Level Response Time (GLRT) of the liquid crystal display.

Background

The reason why the dynamic image of the lcd observed by the human eye is blurred is that the lcd belongs to the Hold Type Display (Hold Type Display), and the dynamic image actually changes the displayed position of the target object in each image to make the human eye feel the movement of the object. Since the motion picture is actually composed of a plurality of still pictures, when the Frame Rate (Frame Rate) of the motion picture is too low, human eyes can easily detect the persistence of vision. In order to be able to specifically express the degree of Motion blur of a moving Picture, a quantized numerical value called Motion Picture Response Time (MPRT) is proposed.

There are two methods currently used for measuring the MPRT, one of which is to capture a change of picture using a mobile camera. This method is based on the assumption that the human eye can move at a constant speed with respect to the object on the display screen, and that the moving object is first displayed on the display screen while the camera is moving at a constant speed to capture the moving object, and finally the blur width is determined by the luminance change received by the camera, and the value of MPRT is further calculated. Another way to measure the MPRT is to use a high-speed camera to capture the motion picture change process and then use spatial integration to obtain the MPRT. In either of the prior art methods, in addition to the cost of the apparatus itself, the speed error of moving the tracked object or the focus error in high-speed capture must be overcome, so that the measurement results may vary greatly from apparatus to apparatus.

Disclosure of Invention

An embodiment of the present invention provides a method for measuring Motion Picture Response Time (MPRT) of a liquid crystal display. The method comprises the following steps: controlling a picture displayed by a display panel of the liquid crystal display to switch among a plurality of different gray scales, and measuring the brightness change of the display panel when the display panel switches the gray scales so as to obtain at least one Gray Level Response Time (GLRT) normalized curve (normalized curve); integrating the at least one gray scale response time normalization curve to obtain at least one motion picture response time normalization curve (MPRT normalized curve); obtaining at least one time interval of the at least one motion image response time normalization curve; and calculating the average value of the at least one time interval to obtain the moving image response time of the liquid crystal display.

Another embodiment of the present invention provides a system for measuring a motion picture response time of a liquid crystal display. The system comprises a computer and a measuring device. The computer is used for controlling the picture displayed by the display panel of the liquid crystal display to switch among a plurality of different gray scales. The measuring device is used for measuring the brightness change of the display panel when the display panel switches the gray scale. The measuring device transmits the measured brightness variation result of the display panel to the computer, and the computer is further used for calculating according to the result to obtain at least one Gray Level Response Time (GLRT) normalized curve (normalized curve). The computer is further configured to integrate the at least one gray scale response time normalization curve to obtain at least one motion picture response time normalization curve (MPRT normalized curve). The computer is further configured to obtain at least one time interval of the at least one motion image response time normalization curve. The computer is further used for calculating an average value of the at least one time interval so as to obtain the motion image response time of the liquid crystal display.

Drawings

FIG. 1 is a functional block diagram of a measurement system and a liquid crystal display under test according to an embodiment of the invention.

FIG. 2 shows one of the Gray Level Response Time (GLRT) normalization curves of the LCD of FIG. 1.

Fig. 3 shows a moving picture response time normalized curve (MPRT normalized curve) corresponding to the gray scale response time normalized curve of fig. 2.

FIG. 4 shows another gray scale response time normalization curve for the LCD of FIG. 1.

Fig. 5 shows a moving picture response time normalization curve obtained by integrating the gray scale response time normalization curve of fig. 4.

FIG. 6 shows one of the gray scale response time normalization curves of the LCD of FIG. 1 when controlling the LCD to display a black screen.

Fig. 7 shows a moving picture response time normalization curve obtained by integrating the gray scale response time normalization curve of fig. 6.

FIG. 8 shows another gray scale response time normalization curve of the LCD of FIG. 1 when controlling the LCD to display a black frame.

Fig. 9 shows a moving picture response time normalization curve obtained by integrating the gray scale response time normalization curve of fig. 8.

FIG. 10 is a flowchart illustrating a method for measuring motion image response time of the LCD of FIG. 1 according to an embodiment of the present invention.

Description of the symbols

1 measuring system

10 liquid crystal display

12 display panel

14 pixels

16 control circuit

20 computer

22 application program

24 central processing unit

100 measuring device

110、130、G_i，j(t)、G′_i，j(t) Gray-level reaction time normalization Curve

120、140、M_i，j(t_s)、M′_i，j(t_s) Moving image reaction time normalization curve

200 method

S210 to S240

D digital signal

Lu brightness

Si display signal

Sc control signal

T_fFrame period

Tr reaction time

T_MMotion image reaction time

t_a、t_b、t_o、t_ePoint in time

Time interval of delta T

Detailed Description

Fig. 1 is a functional block diagram of a measurement system 1 and a liquid crystal display 10 to be measured according to an embodiment of the invention. The measuring system 1 includes a measuring device 100 and a computer 20. The measuring device 100 and the computer 20 are coupled to the liquid crystal display 10, and the measuring device 100 is further coupled to the computer 20. The measuring device 100 includes a photosensitive element (e.g., a photosensitive coupling element) and an analog-to-digital converter, etc. for measuring the brightness variation of the liquid crystal display 10. The liquid crystal display 10 includes a control circuit 16 and a display panel 12. The control circuit 16 receives the display signal Si from the computer 20 to control the pixels of the display panel 12 to display corresponding frames according to the received display signal Si, and the liquid crystal in the display panel 12 is controlled to perform a transition (i.e. polarity inversion) when the display panel 12 displays different frames, so as to prevent the liquid crystal from gradually losing its optical rotation characteristic due to polarization phenomenon. When the liquid crystal of the display panel 12 is switched, the brightness Lu of the display panel 12 is changed. Therefore, the response time Tr (i.e. the time required for the liquid crystal to change state) of the liquid crystal display 10 can be obtained by measuring the change of the luminance Lu by the measuring device 100. Further, in the present embodiment, when the response time Tr of the lcd 10 is to be measured, the pixels 14 of the display panel 12 are controlled to display the same gray level, so that the display panel 12 displays a single color image. Next, the gray levels displayed by the pixels 14 of the display panel 12 are converted from i to j, where i is not equal to j. In the process of converting gray scales of the pixels 14 of the display panel 12, the measuring device 100 measures the change of the luminance Lu of the lcd 10, converts the measured luminance Lu into a digital signal D, and transmits the digital signal D to the computer 20, so that the application program 22 executed by the cpu 24 of the computer 20 calculates the Response Time Tr of the lcd 10 according to the received digital signal D, and obtains a Gray Level Response Time (GLRT) normalization curve (normalized curve) G_i，j(t) as shown in FIG. 2. Wherein，G_i，jT in (t) represents time, i represents a gray level of the pixel 14 before gray-scale conversion, and j represents a gray level of the pixel 14 after gray-scale conversion.

Furthermore, when the measurement is started, the computer 20 signals the measurement apparatus 100 to start the measurement, and the computer 20 can control the pixels 14 of the display panel 12 to perform gray-scale conversion (i.e. the liquid crystal of the display panel 12 starts to transition) through the display signal Si. The communication between the measuring device 100 and the computer 20 can be bi-directional or unidirectional depending on the transmission interface selected by the user. When the measuring device 100 receives the signal for starting the measurement from the computer 20, it starts to measure the brightness Lu and transmits the digital signal D to the computer 20. The ending mode of the measurement can actively initiate an ending signal by the computer 20 to inform the measuring device 100 to stop the measurement. For example, after the computer 20 receives a sufficient amount of data from the digital signal D, it actively transmits a control signal Sc to notify the measuring apparatus 100 to end the measurement. In addition, the measurement may be ended by actively notifying the computer 20 to end the measurement when the measuring device 100 finds that the display of the display panel 12 is no longer changed.

The application 22 executed by the CPU 24 of the computer 20 calculates the gray-scale response time normalization curve 110 shown in FIG. 2, i.e. G, according to the received digital signal D_i，j(t) is used to show the relationship between the luminance Lu of the display panel 12 and the time t when the gray level of each pixel 14 of the display panel 12 is converted from i to j. Time point t in fig. 2_oIs the point in time at which the gray scale conversion of the pixel 14 starts, and the point in time t_eIs the point in time at which the gray scale conversion of the pixel 14 ends. Note that the luminance represented by the vertical axis of fig. 2 is a value obtained after normalization (normalization). In this embodiment, since the gray level i is smaller than j, the brightness of the display panel 12 after the gray level conversion is larger than the brightness before the gray level conversion. Therefore, the luminance of the display panel 12 before the gray-scale conversion (i.e., when the gray-scale value is equal to i) is normalized to be equal to 0, and the luminance of the display panel 12 after the gray-scale conversion (i.e., when the gray-scale value is equal to j) is normalized to be equal to 1. The above description is made for the case where the gray level i is smaller than j, as for grayThe case where the order i is larger than j will be further described later.

The computer 20 controls the pixels 14 of the display panel 12 to switch between different gray scales and measures the change of the brightness Lu of the display panel 12 to obtain a response time normalization curve G of the gray scales of the display panel 12_i，j(t) of (d). In an embodiment of the present invention, the selected gray scale ranges from darkest 0 to brightest 255, and the computer 20 controls the plurality of pixels 14 to switch between seven different gray scales, which may be 0, 60, 90, 120, 160, 200, and 255, respectively. In other words, i and j are selected from the group consisting of seven gray levels of 0, 60, 90, 120, 160, 200, and 255. Because i is not equal to j, the combination of i and j of each gray scale reaction time normalization curve is different from the combination of i and j of other reaction time normalization curves. In this case, a total of 42 (i.e., 7 × 6) gray scale response time normalization curves G are obtained_i，j(t) as in G_0，60(t)、G_0，90(t)、G_0，120(t)、G_0，160(t)、G_0，200(t)、G_0，255(t)、G_60，0(t)、G_60，90(t)、G_60，120(t)、G_60，160(t)、G_60，200(t)、G_60，255(t)......、G_255，0(t)、G_255，60(t)、G_255，120(t)、G_255，160(t)、G_255，200(t) of (d). Wherein G is_0，60(t) represents a gray scale response time normalization curve obtained when the gray scale of the pixel 14 is converted from 0 to 60; g_0，90(t) represents a gray scale response time normalization curve obtained when the gray scale of the pixel 14 is converted from 0 to 90; g_255，90(t) represents the gray scale response time normalization curve obtained when the gray scale of the pixel 14 is converted from 255 to 90, and so on.

In addition, the application 22 executed by the CPU 24 reflects the time normalization curve G to the gray levels_i，j(t) integration was performed separately to simulate acquisition of a plurality of motion picture response time normalized curves (MPRT normalized curve) M_i，j(t_s). Wherein the motion image has positive response timeNormalized curve M_i，j(t_s) Can be represented by the following formula (1):

wherein, t_sIs time, and T_fA frame period (frame period) of the LCD 10_fEqual to the inverse of the refresh rate of the display panel 12. Therefore, by changing the frame refresh rate of the display panel 12, the frame period T can be changed_f. Therefore, the computer 20 can calculate the frame period T according to the frame rate of the display panel 12_f。

According to the above formula (1), the moving image response time normalization curve M obtained by integrating the gray scale response time normalization curve 110 of FIG. 2_i，j(t_s) I.e., the moving image reaction time normalization curve 120 in fig. 3. Note that the vertical axis of fig. 3 represents the luminance obtained after normalization. In addition, time point t in fig. 3_oI.e. the point in time t in fig. 2_oIndicating the time at which the gray level of the pixel 14 begins to transition.

In the embodiment where the computer 20 controls the plurality of pixels 14 to switch between seven different gray levels, the application program 22 executed by the CPU 24 respectively responds to the 42 gray level response time normalization curves G according to the above formula (1)_i，j(t) integration to obtain 42 moving image response time normalization curves M_i，j(t_s). In the case where i and j are selected from the group consisting of seven gray scales of 0, 60, 90, 120, 160, 200, and 255, the 42 moving image response time normalization curves M_i，j(t_s) Are each M_0，60(t_s)、M_0，90(t_s)、M_0，120(t_s)、M_0，160(t_s)、M_0，200(t_s)、M_0，255(t_s)、M_60，0(t_s)、M_60，90(t_s)、M_60，120(t_s)、M_60，160(t_s)、M_60，200(t_s)、M_60，255(t_s)、......、M_255，0(t_s)、M_255，60(t_s)、M_255，90(t_s)、M_255，120(t_s)、M_255，160(t_s)、M_255，200(t_s). Wherein M is_0，60(t_s) A moving image response time normalization curve representing a moving image obtained when the gray scale of the pixel 14 is converted from 0 to 60; m_0，90(t_s) A moving image response time normalization curve representing a moving image obtained when the gray scale of the pixel 14 is converted from 0 to 90; m_255，90(t_s) The moving image obtained when the gradation representing the pixel 14 is switched from 255 to 90 reflects the time normalization curve, and the rest is analogized.

In addition, the application 22 executed by the cpu 24 obtains the moving image response time normalization curve M_i，j(t_s) The time interval of (c). Taking FIG. 3 as an example, the time point t_aAnd t_bTime interval (t) between_b-t_a) I.e., the time interval of the moving picture response time normalization curve 120 that the application 22 is to obtain. Wherein the time-response normalization curves M are represented for different motion pictures_i，j(t_s) May correspond to different time points t_aAnd/or different points in time t_b. In this embodiment, M_i，j(t_a) Equal to 0.1, and M_i，j(t_b) Equal to 0.9. In addition, the application 22 calculates an average value of all time intervals to obtain a moving image response time of the liquid crystal display 10. Suppose that the moving image response time of the liquid crystal display 10 is T_MNormalized curve M of motion image response time_i，j(t_s) Time interval (t)_b-t_a) Is equal to T_i，jThen, the motion image response time TM of the liquid crystal display 10 can be obtained by the following equation (2):

T_i，j＝(t_b-t_a) (3)

wherein N is a moving image reaction time normalization curve M_i，j(t_s) The total number of (c). For example, in the embodiment where the computer 20 controls the plurality of pixels 14 to switch between seven different gray levels, N is equal to 42.

Fig. 2 and fig. 3 are diagrams respectively illustrating a gray scale response time normalization curve and a moving image response time normalization curve corresponding to the gray scale i smaller than j. When the gray scale i is larger than j, the corresponding gray scale response time normalization curve and motion image response time normalization curve can be represented by fig. 4 and 5, respectively. Fig. 4 shows another gray scale reaction time normalization curve 110 of the liquid crystal display 10 of fig. 1, and fig. 5 shows a moving picture reaction time normalization curve 120 obtained by integrating the gray scale reaction time normalization curve 110 of fig. 4. In the embodiment of fig. 4 and 5, since the gray level i is greater than j, the brightness of the display panel 12 after gray level conversion is less than the brightness before gray level conversion. Therefore, the luminance of the display panel 12 before the gray-scale conversion (i.e., when the gray-scale value is equal to i) is normalized to be equal to 1, and the luminance of the display panel 12 after the gray-scale conversion (i.e., when the gray-scale value is equal to j) is normalized to be equal to 0. Furthermore, M_i，j(t_a) Equal to 0.9, and M_i，j(t_b) Equal to 0.1.

In another embodiment of the present invention, the reaction time T is shortened for the purpose of shortening the moving image_MThe control circuit 16 turns off the backlight module of the lcd 10 for illuminating the pixels 14 (i.e., dynamically adjusts the backlight module) in time, so that the display panel 12 displays a black frame within a predetermined time period. The embodiment can simulate the moving image reaction time under different backlight conditions by adding the reaction time curve and the backlight starting time of the changed liquid crystal display. Taking fig. 6 as an example, the area marked by the dots in fig. 6 is the time when the backlight module of the liquid crystal display 10 is turned off; the area not marked by the dots is the time when the backlight module of the liquid crystal display 10 is turned on. Wherein, T_fIs the frame period of the LCD 10, and Δ T is the period of time that the backlight module is turned on, T_oRepresents the point in time at which the gray scale conversion of the pixel 14 begins, and t_eIndicating the point in time at which the gray scale conversion of the pixel 14 ends. In this embodiment, G 'is used as the gray-scale reaction time normalization curve 130'_i，j(t) is the moving picture reaction time normalization curve 140 expressed by M'_i，j(t_s) Is represented by G'_i，j(t) and G_i，jThe relationship between (t) can be represented by the following formula (4), and the moving picture reaction time normalization curve M'_i，j(t_s) Can be represented by the following formula (5):

wherein n is a positive integer.

As can be seen from a comparison of FIGS. 3 and 7, the time intervals (t) in FIG. 7_b-t_a) Will be less than the time interval (t) in fig. 3_b-t_a). Therefore, the time interval (t) can be shortened by turning off the backlight module briefly to make the display panel 12 display black images_b-t_a). According to the above formulas (2) and (3), the time interval (t)_b-t_a) When shortened, the moving image response time of the liquid crystal display 10 is T_MIt is correspondingly shortened.

Fig. 6 and fig. 7 are diagrams respectively illustrating the gray scale response time normalization curve and the moving image response time normalization curve when the gray scale i is smaller than j and the display panel 12 is controlled to display a black frame. When the gray level i is larger than j and the display panel 12 is controlled to display a black frame, the corresponding gray level response time normalization curve and the corresponding motion image response time normalization curve can be respectively shown in fig. 8 and 9. In the embodiment of FIGS. 8 and 9, the display panel 12 is after gray level conversion because the gray level i is greater than jThe luminance is less than the luminance before the gray-scale conversion as shown in fig. 8. Therefore, the luminance of the display panel 12 before the gray-scale conversion (i.e., when the gray-scale value is equal to i) is normalized to be equal to 1, and the luminance of the display panel 12 after the gray-scale conversion (i.e., when the gray-scale value is equal to j) is normalized to be equal to 0. Furthermore, M'_i，j(t_a) Equal to 0.9, and M'_i，j(t_b) Equal to 0.1.

FIG. 10 is a flowchart of a method 200 for measuring motion image response time of the LCD 10 of FIG. 1 according to an embodiment of the present invention. The method 200 comprises the following steps:

step S210: controlling the frame displayed by the display panel 12 to switch between a plurality of different gray scales, and measuring the change of the brightness Lu of the display panel 12 when the display panel 12 switches the gray scales to obtain at least one gray scale response time normalization curve G_i，j(t)；

Step S220: normalizing curve G for the reaction time of the at least one gray scale_i，j(t) integrating to obtain at least one moving image response time normalization curve M_i，j(t_s)；

Step S230: obtaining the at least one motion image response time normalization curve M_i，j(t_s) At least one time interval T_i，j(ii) a And

step S240: calculating the at least one time interval T_i，jTo obtain the moving image response time T of the liquid crystal display 10_M。

Compared with the prior art, the invention simulates and obtains the Motion Picture Response Time (MPRT) of the liquid crystal display by measuring the gray scale response time (GLRT) of the liquid crystal display. Since the gray scale response time of the liquid crystal display can be measured by the light sensing element, the analog-digital converter and other elements, the expensive equipment such as the mobile camera in the prior art is not needed. Therefore, according to the present invention, the MPRT of the liquid crystal display can be obtained without using a complicated measuring apparatus, and the reliability and the convenience of obtaining the numerical value of the MPRT can be greatly improved.

The above-mentioned embodiments are only preferred embodiments of the present invention, and all equivalent changes and modifications made by the claims of the present invention should be covered by the scope of the present invention.

Claims

1. A method of measuring a motion image response time of a liquid crystal display, the method comprising:

controlling a picture displayed by a display panel of the liquid crystal display to switch among a plurality of different gray scales, and measuring the brightness change of the display panel when the display panel switches the gray scales so as to obtain at least one gray scale reaction time normalization curve;

integrating the at least one gray scale reaction time normalization curve to obtain at least one motion image reaction time normalization curve;

obtaining at least one time interval of the at least one motion image response time normalization curve; and

calculating an average value of the at least one time interval to obtain the motion image response time of the LCD.

2. The method according to claim 1, wherein the at least one gray-scale reaction time normalization curve is a plurality of gray-scale reaction time normalization curves, and each gray-scale reaction time normalization curve is expressed by G_i,jAnd (t) represents the relationship between the brightness of the display panel and time when the gray scale of each pixel of the display panel is converted from i to j, wherein t is time and i is not equal to j.

3. The method of claim 2, wherein i and j are selected from the group consisting of seven gray levels, which are 0, 60, 90, 120, 160, 200, and 255, respectively.

4. The method according to claim 2 or 3, wherein the combination of i and j of each gray scale reaction time normalization curve is different from the combination of i and j of other reaction time normalization curves.

5. As claimed inThe method of claim 2, wherein the time response to gray scale is normalized by a curve G_i,j(t) the moving image response time normalization curve obtained by integration is M_i,j(t_s) To do so

Wherein t is_sIs time, and T_fIs a frame period of the LCD.

6. The method according to claim 5, wherein the moving image response time normalization curve M_i,j(t_s) Is equal to (t)_b-t_a)，t_aAnd t_bAt two different time points, and M_i,j(t_a) And M_i,j(t_b) Between 0 and 1.

7. The method of claim 6, wherein when i is less than j, M_i,j(t_a) Less than M_i,j(t_b) (ii) a And

wherein when i is greater than j, M_i,j(t_a) Greater than M_i,j(t_b)。

8. The method of any of claims 1-3 and 5-7, further comprising:

and turning off a backlight module of the liquid crystal display for at least a preset period in the process of switching the gray scale of the picture of the display panel.

9. A system for measuring motion image response time of a liquid crystal display, the system comprising:

a computer for controlling the switching of the picture displayed by a display panel of the liquid crystal display between a plurality of different gray scales; and

a measuring device for measuring the brightness change of the display panel when the display panel switches the gray scale;

the computer is used for calculating according to the result to obtain at least one gray scale reaction time normalization curve;

wherein, the computer is also used for integrating the at least one gray scale reaction time normalization curve to obtain at least one motion image reaction time normalization curve;

wherein, the computer is further used for obtaining at least one time interval of the at least one moving image reaction time normalization curve; and is

The computer is further configured to calculate an average value of the at least one time interval to obtain the motion image response time of the liquid crystal display.

10. The system of claim 9, wherein the at least one gray-scale reaction time normalization curve is a plurality of gray-scale reaction time normalization curves, and each gray-scale reaction time normalization curve is expressed by G_i,jAnd (t) represents the relationship between the brightness of the display panel and time when the gray scale of each pixel of the display panel is converted from i to j, wherein t is time and i is not equal to j.