JPS5856875B2 - display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a display device that has a display surface in which a large number of display elements that can emit light (on state) and stop (off state) can display images having intermediate tones. Along with displaying
The present invention relates to a display device that can change the brightness of the entire display screen.

BACKGROUND ART Conventionally, display devices such as light bulbs and light emitting diodes arranged in a matrix have been used as large-sized or flat display devices such as scoreboards in stadiums.

In order to display an image with halftones by pressing a button on these display devices, the on-state (light emission) time width of each display element is controlled by controlling the on time (lighting time) or off time (lighting out time) of the display element. A method was used in which the level of the image signal was made proportional to the image signal.Furthermore, when adjusting the brightness of the screen, a method was used in which the level of the image signal was reduced.

However, according to this method, the time T that can be used for on/off judgment and control of one display element is defined as the image display period, where the number of TF halftones is y, and the number of display elements is X. Since Tc=Tp/((y-1)XX), as the number of gradations and the number of display elements increases, To becomes smaller, making it difficult to increase the number of intermediate gradations and the number of display elements. Ta.

Furthermore, when performing brightness control, since the level of the image signal is changed, there are drawbacks such as a reduction in the number of halftones that can be effectively used when displaying at low brightness.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above.The amplitude change range of the image signal is roughly divided into m levels, and these levels are further divided into n levels, and the whole image signal is divided into m levels. Divide the levels into m×n ways as
An image signal is represented by two level signals a and b.

By turning on the display element with these two level signals a and b and making it possible to freely change the off time based on this on time, the number of on/off decisions can be reduced and multi-gradation can be easily realized. In addition to making halftone display possible,
This makes it possible to realize a display device that can change the brightness of the entire display screen without changing the number of halftones.

An embodiment of the present invention will be described below with reference to the drawings.

Also in Figure 1, 1 is a level discrimination circuit, 2 is a memory,
3 is an on (lighting) judgment circuit, 4 is a synchronization signal generation circuit, 5
Reference numeral 1 indicates an address designation circuit, 6 a row selection circuit, 7 a reset pulse generation circuit, 8 an on (lighting) signal memory, and 9 a display board in which display elements having a memory function are arranged in a matrix.

A display element having this memory function is the same even when the display element itself does not have a memory function or when combined with another memory element.

The image signal is sent to the level discrimination circuit 1 and is divided into m levels as shown in FIG. 2, and within these levels, it is further divided into n levels, resulting in a total of mXn levels.

If the image signal is represented by ■, the m-divided level signal is a, and the n-divided level signal is b, then it can be expressed as follows.

These level signals a and b are stored in the memory 2.

The lighting (on operation) of the display element is controlled based on this stored level signal.

Hereinafter, a display element with one line of needles will be focused on and explained according to FIGS. 3 and 4.

In Fig. 3, the horizontal axis shows time and the vertical axis shows the amplitude of the image signal, and in Fig. 4, the horizontal axis shows time and the vertical axis shows the row. are shown respectively.

So, for example, m=4. Let's talk about the case where you want to express 16 gray levels with n=4. In this case, as shown in FIG. 3, TB3. TB2. TBL.

Controls lighting (on) and non-lighting (off) of the light emitting element at time TAO+TAlt TA2 * TA3 t.

For simplicity, it is assumed that the processes described below are performed at the same time.

The addressing circuit 5 reads the level signal corresponding to the display element, and the on (lighting) judgment circuit 3 compares it with the level corresponding to that time to judge whether it is on (lighting) or not. is b≧3. At time TB2, b
≧2. At time TBl, b≧1 + at time TAI, a≧l; at time TA2, a≧2. At the time of TA3, a
If ≧3, an on signal is generated.

This on (lighting) signal is stored in a one-line valve on (lighting) signal storage circuit.

The row selection circuit 6 selects a row to be turned on (lighted up) based on the address signal, generates a set pulse, and applies it to the display element.

At this point, it is turned on (lit) from the signal storage circuit.
The display element to which the signal was applied turns on (lights up), and since it has a memory function, it maintains the on state at 1 when the next reset pulse is applied.

The reset pulse generating circuit 7 generates a reset pulse with a certain time delay after the set pulse is generated, and applies it to the display element.

The display element stops being on due to a reset pulse, and then stops being on when an on (lighting) signal and a set pulse are applied.

The time at which this set pulse color reset pulse is generated is TB3. If it is assumed that there is a delay of time T from the time of TB2°TBl, then TAl, TA2. From the time of TA3, the time is multiplied by n, that is, nXT.

By changing this time T, it is possible to change the ratio of the on time and off time within the time span in proportion to the image signal, thereby adjusting the brightness of the image.

For the buttons in FIG. 2, it is assumed that the time width T satisfies O≦T≦1.

Regarding the entire display element, the times corresponding to TB and TA are different for each row, and as shown in FIG. 4, at time X, TB3 of row X is controlled, and at time Y, TB2 of row y is controlled. Scanning is performed by the addressing circuit 5 for control purposes.

Here, for simplicity, we have described an example of a circuit that stores a level signal in a memory, but converts an image signal into a binary code, stores this binary code in a memory, and converts the upper bit group into the above-mentioned a and the lower bit group. The same thing applies to b.

Furthermore, although control has been explained in units of rows, it is clear that the combination of rows and columns can be changed freely.

According to the present invention, when displaying mXn intermediate tones, the conventional method required mXn-1 ON/OFF determinations, but only n+m-2 determinations are required, and the display cycle is kept constant. can easily have multiple gradations.

Further, even when the brightness of the image is changed, there is no change in the number of gradations, so a great practical advantage is obtained, such as being able to display a good image.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIGS. 2 to 4 are diagrams explaining the operation of the device shown in FIG.
Figure 2 is a graph showing the level classification, Figure 3 is the on state (
(light emission), off state (light emission stop) duration and on (lighting)
FIG. 4 is a timing chart showing the relationship between time and off (lights out) time, and FIG. 4 is a timing chart showing the relationship between row and scan. In the figure, 1 is a level discrimination circuit, 2 is a memory, 3 is an on-discrimination circuit, 4 is a synchronization signal generation circuit, 5 is an address designation circuit, 6 is a row selection circuit, 7 is a reset pulse generation circuit,
8 is an on-signal memory, and 9 is a display element board. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A display board in which display elements having a memory function are arranged in a matrix, a level discrimination circuit that divides image signals into levels, a memory that stores this level signal, a read address button of this memory, and a display element that is to be turned on. an on-determination circuit that compares this read level signal with a level corresponding to the time and determines whether it is on or not; and a display element to which this on-signal is designated by the addressing circuit. It has a row selection circuit and an on-signal storage circuit for applying the on-signal to the display element, and a reset pulse generation circuit that starts for a certain period of time from the time when the on-signal is applied to the display element and stops the on-state. A display device characterized in that the brightness of the entire screen can be changed by changing the ratio of the on time width and the off time width within the time width.