JPH03174117A - Gradation display method of liquid crystal panel - Google Patents

Abstract

PURPOSE:To allow the execution of the gradation display in more stages than heretofore by simple means while suppressing the generation of flickering by defining one frame by the time to apply signals to approximately all the picture elements of a display screen and defining the plural frames as a large period and then forming one unit of images for every large period. CONSTITUTION:The time for applying the signals to approximately all the picture elements of the display screen is defined as the frame and the plural frames are defined as the large period. The time of the respective frames in the large period varies respectively and the brightness of the picture elements is controlled with the large period as a unit. Namely, the frame periods within the large period, one period of which is the plural frames, are constituted of the plural different frame periods to increase the number of the combinations for the gradation display without increasing the time for the large period. The gradation display in the larger number of the steps than in the conventional method is executed in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for relatively easily displaying multi-level gradation on a liquid crystal panel.

[Conventional technology]

In recent years, the performance of matrix-type liquid crystal panels that can freely display a variety of displays has improved, and they are now widely used in place of cathode ray tubes for applications that require smaller size and lighter weight, such as display devices for personal computers. It has come to be like this.

In this type of application, there is a huge stock of off-the-shelf software created for conventional personal computers that use cathode ray tubes as display elements, so it is best to utilize that stock with as little modification as possible. It is desirable to be able to do so.

Many of these software programs use color cathode ray tubes as display devices, and display images in different colors and gradations depending on the content.

If these off-the-shelf software are to be used in a liquid crystal display, the liquid crystal display must be able to support gradation display.

As is well known, the relationship between the density of an image displayed on a liquid crystal panel and the voltage (effective value) applied to the liquid crystal changes as shown in FIG. Therefore, by varying the applied voltage within an appropriate range, it is possible to display multi-level gradations including so-called intermediate densities (Japanese Patent Publication No. 16894/1983).

Here, since the voltage value shown on the horizontal axis of Fig. 3 is the effective value,
It can be changed by changing not only the absolute value of the voltage but also the voltage application time.

Conventionally, a method as shown in FIG. 2, for example, has been used to meet the demand for gradation display. In Figure 2, F L M (
Frame Line Marker) is a frame start signal. In Figure 2, three frames are set as one set, and each frame is configured according to the desired gradation, and as shown in A, no voltage is applied to all three frames (not in a selected state), or Apply voltage only in the first frame of the three frames as in B, or apply voltage in the first and last frames as in C, or apply voltage only in the first two frames as in D. Or, as shown in E, a state is disclosed in which voltage is applied in all frames.

That is, gradation display can be performed by combining these states.

When gradation display is performed using the conventional technique shown in Fig. 2, the image density is determined by the effective value of the applied voltage.
-H out of five types of drive voltage application methods.

Since C and D have the same effective value as the driving voltage, they are displayed at the same density and cannot be distinguished, and although there are five combinations of selected and non-selected states of three frames, in the end only four gradations can be displayed.

[Problem to be solved by the invention]

The so-called frame thinning technique described above can be applied to up to about 8 gradations without any problems. However, recently, there has been a demand for multi-level display with six or more levels. If we were to perform such a multi-stage display using the conventional method, we would have to change the 3T in Fig. 2 to 4T in order to increase the number of combinations.

It is necessary to increase it to 5T, 6T, etc.

In this case, a so-called printing force phenomenon occurs on the display screen, causing discomfort to the user of the display device, and causing a problem that it is not practical.

[Means to solve the problem]

An object of the present invention is to provide a gradation display method for a liquid crystal panel that can solve the problems of the prior art described above and can display gradation levels in more stages than before using simple means while suppressing the occurrence of the printing force phenomenon. shall be.

[Operation] In order to achieve the above object, in the present invention, in a large period in which a plurality of frames constitute one period, the frame period within the large period is made into a plurality of different frames, and the time of the large period is increased. This increases the number of combinations that can be used to display one gradation level.

〔Example〕

FIG. 1(a) shows an embodiment of the present invention. In the example of FIG. 1(,), a normal 3-frame period is 3T.

It is subdivided into three short periods, each having a different length: 615T, T, and 415T. As shown in FIG. 2(a), in addition to A when all vehicle periods are in the non-selected state and cases where all vehicle periods are in the selected state, B-1, B-2, B-3, C-
It is possible to display six types of intermediate gradations: 1, C-2, and C-3, making the total number of gradations eight. In other words, in the conventional method, the 3-frame period 3T could be divided into 3 equal parts and only 4 types of gradations could be displayed, but with the method of the present invention, the same frame period 3T could be divided into 3 different lengths. By re-dividing the periods, it becomes possible to display eight types of gradation, which is twice as many as before. The reason why flicker is often perceived in conventional frame thinning methods is that frames are thinned out in a makeshift manner in order to increase the number of gradations.

FIG. 1(b) shows the basic system configuration for implementing the method of the present invention, in which 1 is a liquid crystal display device, 2 is a liquid crystal display controller, 3 is a buffer memory, 4 is a video RAM, and 5 is a CPU. , 6 is a bus.

The CPU 5 controls the operation of the entire system.

Video RAM 4 stores digital data to be displayed on liquid crystal display device 1 . The liquid crystal display controller 2 is Video R.
It reads display data from the AM 4 and writes it into the buffer memory 3, reads the data again from there, transfers the data to the liquid crystal display device 1, and displays it. The liquid crystal display controller 2 also generates timing signals and control signals necessary for the liquid crystal display device 1. The role of the buffer memory 3 is to temporarily write the data read from the video RAM 4 into this buffer memory 3, and then read the data at the timing of multiple types of frame periods of different lengths by the function of the liquid crystal display controller 2. This enables the operation of the method of the invention.

FIG. 1(c) shows a partial detailed view of the liquid crystal display controller 2, which is the central part of the present invention, and its relationship with the liquid crystal display device 1.

In FIG. 1(Q), 21 is a display color determination circuit, which determines what intermediate color or gradation should be displayed from data received from the video RAM 4 or the buffer memory 3.

22 is a large cycle setting circuit. Reference numeral 23 denotes a frame period setting circuit, which specifically determines the period of the first FLM.

24 is a data button generator; 1 display color determination circuit 2;
This circuit combines the video data from 1 and various frame periods obtained from the frame period setting circuit to create data that enables gradation display.

25 is a timing circuit that generates a timing pulse to drive the liquid crystal. CL↓ is a data latch signal and a pulse for scanning, and CL2 is a pulse for data shifting.

Further, M is a multiplier, which is a signal for AC driving the liquid crystal. Reference numeral 26 denotes a successive control circuit, which has a function of controlling the read speed of the video RAM 4 according to the frame period determined by the frame period setting circuit 23.

In FIG. 1(C), the liquid crystal display section 11 has n
It is divided into two screens with the book's scan lines, and the two screens are driven simultaneously. Here, Dl is a data signal to the upper screen, and t02 is a data signal to the lower screen.

FIG. 1(d) shows an example of the timing chart of the liquid crystal drive signal shown in FIG. 1(c). can be changed by

FIG. 1(e) shows the liquid crystal display section 11 in FIG. 1(c).
Figure 1 (Q
), 2n parallel X electrodes are formed in the horizontal direction, and m parallel X electrodes are formed in the vertical direction. The m electrodes in the vertical direction are located at the top and bottom of the screen, and the screen is divided into the top and bottom, and each screen is driven. A liquid crystal is sandwiched between the X electrodes, and the light transmittance of the liquid crystal changes depending on the effective value of the voltage between the X electrodes, thereby making it possible to display an image.

In FIG. 1(e), the number of pixels is 2nXm.

〔Effect of the invention〕

As explained above, according to the present invention, it becomes possible to perform gradation display with a greater number of steps than the conventional method using simple means.

[Brief explanation of the drawing]

Fig. 1 (a) is an explanatory diagram of the method of the present invention, Fig. 1 (b) is a diagram showing the basic system configuration for implementing the method of the present invention,
(Fig. 1(c) is a partial detailed view of the liquid crystal display controller in Fig. 1(b), a detailed view of the liquid crystal display section, and the construction drawing (d)
2 is a diagram showing a timing chart of liquid crystal drive signals.
The figure is a diagram for explaining an example of a conventional gradation display method, and FIG. 3 is a diagram showing the relationship between the effective voltage value applied to the liquid crystal and the density of the displayed image. 1...Liquid crystal display device, 2...Liquid crystal display controller, 3.
...Buffer memory, 4...Video RAM, 5...
CPU, 6... bus, 11... liquid crystal display section, 21.
...Display color judgment circuit, 22...Large cycle setting circuit, 23 - Frame period setting period Figure 1 (a) YIYY3 Figure 2 E Effective voltage (V) Procedural amendment (method) Case display flat Im, 2nd year patent application No. 190663 Name of the invention Name related to the case involving a person who corrects the gradation display method of a liquid crystal panel

Claims (1)

[Claims] 1.1 frame is defined by the time for applying a signal to almost all pixels of the display screen, a plurality of the frames is defined as a large period, and the time of each frame within the large period is A method for driving a matrix display element, characterized in that each image is different from the other, and one unit of the image is formed for each of the large periods. 2. A matrix display system using the driving method according to claim 1, wherein the brightness of each pixel constituting the screen is controlled in units of the large cycle. 3. Using the driving method according to claim 1, wherein a plurality of the pixels constitute a basic pixel, and the brightness of the basic pixel is controlled in units of the large period. Matrix display system. 4. The driving method according to claim 1, wherein a plurality of the basic pixels constitute tone constituent pixels, and the display color by the tone constituent pixels is constituted in units of the large period. Matrix display system used. 5. A plurality of parallel first conductive film groups, a plurality of parallel second conductive film groups perpendicular thereto, and sandwiched between the first conductive film group and the second conductive film group. In a liquid crystal display element made of liquid crystal, opposing portions of the first conductive film and the second conductive film form pixels, and a time frame is used to apply signals to substantially all pixels of the display screen; A liquid crystal display system characterized in that the plurality of frames constitute a large period, the time of each frame within the large period is different, and the brightness of the pixel is controlled in units of the large period. 6. The liquid crystal according to claim 5, wherein the brightness of the pixel depends on the effective value of the potential difference between the first conductive film and the second conductive film facing each other. display system. 7. The liquid crystal display system according to claim 6, wherein a plurality of the pixels constitute basic pixels, and the brightness of the basic pixels is controlled in units of the large period. 8. The liquid crystal display system according to claim 7, wherein a plurality of the basic pixels constitute color tone constituent pixels, and the displayed color by the tone constituent pixels is constituted using the large period as a unit. .