JPS5856874B2 - display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a display device in which a large number of display elements that have two states, on and off, are arranged as a display surface and display an image having halftones, and in particular, to reduce the brightness of the entire display screen. This invention relates to a display device that can be changed.

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

In order to display images with halftones in these devices, a method is used in which the on-state time width (lighting time width) of the display element is made proportional to the image signal. Similarly, when adjusting the brightness of the entire image, a method of adjusting the level of the image signal is used.

According to such a conventional method, if the number of halftones when displaying an image at maximum brightness is n, then when trying to display an image at half the brightness, the effective halftones are n. /
It becomes 2.

When displaying at such low brightness, there is a drawback that the number of effective halftones decreases and the image deteriorates.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and it is possible to change the on state (lighting) and off state (lighting out) of the display element within a time span generated in proportion to the image signal. To provide a display device that displays a good image without changing the number of halftones even if the image brightness is changed by adjusting the image brightness by changing the time width ratio of the image brightness. The purpose is

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a level discrimination circuit, 2 is a memo IJ-13 is an on-determination circuit, 4 is a scanning signal generation circuit, 5 is an address designation circuit, and 6 is a A row selection circuit, 7 a reset pulse generation circuit, 8 an on-signal memory, and 9 a display board in which display elements having a memory function are arranged in a matrix.

Incidentally, the on-determination circuit 3, the address designation circuit 5, the row selection circuit 6, and the on-signal memory 8 constitute an on-control circuit for each display element on the display board.

The image signal is encoded in the level discrimination circuit 1 and stored in the memory 2.

The on-time of the display element is controlled based on this level signal.

For convenience's sake, we will focus on one row of display elements in Figures 2--
This will be explained according to the fourth item.

In FIGS. 2 and 4, the horizontal axis represents time, and the vertical axis represents the amplitude value of the image signal.

In FIG. 3, the horizontal axis represents time and the vertical axis represents rows.

Therefore, when attempting to display eight gray levels, for example, the address designation circuit 5 operated by the clock signal from the scanning signal generation circuit 4 selects T1 as shown in FIG.
The image signal encoded at each time of ~T7 is read from the memory 2, and the on-determination circuit 3 compares it with the level corresponding to that time, determines whether or not to turn on the corresponding display element, and generates an on-signal. This on-signal for one digit is stored in the on-signal memory 8 and applied to the display element.

The row selection circuit 6 receives an address signal from the address designation circuit 5, selects a corresponding row on the display panel 9, and generates a set pulse.

At this point, the display element to which the on signal has been applied from the on signal memory 8 is turned on, and since it has a memory function, it remains on until the next reset pulse is applied.

After generation of the set pulse, the reset pulse generation circuit 7 generates a reset pulse with a delay of a time T proportional to the image brightness setting signal, applies it to the display element, and the display element stops being on.

By repeating the same operation from T to T7, each display element will display eight gray levels.

In other words, the time width shown by the dotted line in Figure 2 is proportional to the time when the ON signal is applied during the display cycle, that is, the image signal, and the time width T from the generation of the set pulse to the generation of the reset pulse is the brightness setting. Since it changes depending on the signal, the cumulative time duration of the on state is proportional to the image signal, and the brightness setting signal is also proportional.

Therefore, the brightness of each display element can be varied from maximum brightness to zero while maintaining the required number of gradations.

When focusing on all pixels, the above operation is performed for each row, but the times corresponding to T to T7 are different for each row.

For example, as shown in FIG. 3, at time A, T2 is controlled in row a, and at time B, T3 is controlled in row a.
control.

In the above embodiment, a method was described in which control is performed at equal time intervals based on a level signal, but for example, as shown in FIG. At t2, control is performed by signal a, at t3, control is performed by C, i, 8
The time width of i 2 is 4, and the time width of 12<-+13 is 2.
A method is also known in which halftones are displayed by setting the time width of t34+t,' as 1 and making the accumulation of time widths shown by dotted lines proportional to the image signal.

Even in such a case, as mentioned above, 11, 12,
The time span from when a set pulse is generated at 13 to when a reset pulse is generated is 4T, corresponding to the times 11, 12, and 13.

It is clear that similar effects can be obtained by configuring the reset pulse generation circuit so that the pulses are 2T and 2T.

As described above, according to the present invention, the brightness of the entire display screen is adjusted by changing the ratio of the on time width and the off time width within a time width proportional to the image signal without changing the level of the image signal. This provides the great advantage of being able to display halftones with a large number of gradations even at low brightness, and displaying high-quality images.

Furthermore, it also has the practical advantage that the ratio of the on-time duration to the off-time duration can be easily set using a brightness setting signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG.
FIG. 4 is a diagram explaining the operation of the device shown in FIG. 1, and FIG. 2 is a timing chart showing the relationship between the on-state/off-state time width and the on/off time of the light-emitting element in the embodiment. FIG. 3 is a timing chart showing row scanning, and FIG. 4 is a timing chart showing another embodiment. In the figure, 1 is a level discrimination circuit, 2 is a memory, 3 is an ON discrimination circuit, 3 and 4 are scanning signal generation circuits, 5 is an address designation circuit, 6 is a row selection circuit, 7 is a reset pulse generation circuit, and 8 is an ON A signal memory, 9 is a display board. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A display board with a large number of display elements having a memory function arranged as a display surface, each display element being scanned at a predetermined display cycle, and the on-time during the display cycle being displayed on the display element. It has an on control circuit section that performs control in proportion to the amplitude of the image signal to be displayed, and an off control circuit section that controls the off time using a brightness setting signal, By controlling the ratio of the cumulative on time width and off time width within the possible on time width during the display period controlled by the control circuit with the off control circuit, the display has a number of gradation levels independent of brightness. A display device characterized by displaying halftones. 2. The display device according to claim 1, wherein the display device is configured so that the brightness setting time is given from the outside.