JPS593777B2 - cathode ray tube display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a cathode ray tube display device in which data entry is performed using a light pen.

Recently, display devices using cathode ray tubes are often used as terminals for electronic computers, etc., and it is also known that light pens are often used as a means of writing data directly onto the cathode ray tube screen. . Such a light pen detects the light displayed on the screen and generates an output pulse that roughly corresponds to the raster light that traverses the field of view, but this output pulse depends on the afterglow time characteristics of the phosphor of the cathode ray tube and the brightness of the screen. Waveform distortion, pulse width, peak level, etc. change depending on the situation.

Particularly in color cathode ray tube display devices, the phosphors of each of the three primary colors have different afterglow time characteristics, and the output pulses detected by the light pen vary depending on the displayed color.

Particularly in this case, the red phosphor has an afterglow time (10% afterglow) of several milliseconds, which is longer than the several microseconds of the blue phosphor. Therefore, the level of the output pulse detected by the light pen is high when blue display light is detected, and becomes extremely low when red display light is detected. Further, when detecting red display light, the pulse width becomes wider than when detecting blue display light. As a result, when detecting the display light on the screen of such a color cathode ray tube,
The output pulse became extremely unstable in detection and output. For this reason, conventionally, when inputting data using such a light pen, the raster on the screen was switched to white or blue to avoid writing in unstable red. on the other hand,
The detection and output of such a light pen also changes depending on the brightness of the screen.

In particular, when data is displayed on the screen and you write over it, the brightness of the data is the brightness of the background.In other words, if the contrast between the displayed data and the background is strong, the output pulse of the detected light pen will be The waveform is distorted and the pulse width also changes. As a result, the data to be written was not input at the correct position on the screen where the light pen was applied. For example, the brightness level of this type of device is typically set as shown in Figure 1A;
When the light pen is applied to a position A where no data is displayed on the screen, a pulse having a waveform like that shown in FIG. 1B is outputted from the light pen. However, if the light pen is applied to a position immediately in front of the displayed data, as shown at the mouth in Figure 1A,
Pulses with different pulse widths are output with waveform distortion similar to the shape of a mouth. The opportunity for the light pen to be applied to the position of the mouth in Figure 1 A is because this type of device makes characters, figures, etc. displayed on the screen consist of a set of bright spots. This is often caused by the fact that it is formed by several units of bright spots and is narrow. As a result, as mentioned above, the output of the light pen has waveform distortion and a different pulse width, and depending on the performance of the light pen, a situation where the written data is not input at the correct position on the screen often occurs. It was hot. The present invention takes into consideration the afterglow time characteristics of the phosphor of a cathode ray tube as described above, and reduces the brightness on the screen, especially the contrast between data and the background, when writing data, thereby improving the screen display color. without switching to white or blue.
The object of the present invention is to provide a cathode ray tube display device that allows data input using a color display based on a combination of three primary colors.

Further, the present invention aims to provide a cathode ray tube display device that enables data input at an accurate position even when writing data on the screen where data is displayed. .

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a cathode ray tube display device, whether color or monochrome, in which output pulses obtained from a light pen are always stable when writing data.

The present invention will be described below with reference to the drawings.

FIG. 2 is a diagram showing an example of the contrast ratio between data and the background during data writing by the device according to the embodiment of the present invention, which will be described later.Here, as shown in FIG. 2A, the data amplitude is lowered to, for example, about 80%, The case is illustrated in which the background level, that is, the DC clamp level, is raised to about 60% to soften the contrast between the two compared to when displaying data. Therefore, the contrast ratio between the two when displaying data is herein assumed to be a first ratio as shown in FIG. 1A, and the contrast ratio shown in FIG. 2A is referred to as a second ratio. The first and second ratios are appropriately set to optimal values depending on the characteristics of the cathode ray tube, the performance of the light pen, etc., by means described later. FIG. 3 shows a main circuit of an apparatus according to an embodiment of the present invention, and here the case of a monochrome cathode ray tube display apparatus is shown.

Further, FIG. 4 shows the main part configuration of an embodiment of the present invention in the case of a color cathode ray tube display device using a three-primary color demodulation excitation method.
A specific example of the circuit after the main circuit is constructed in the same manner as the main circuit shown in FIG. 3, so it is omitted here. First, the structure and operation of the embodiment apparatus shown in FIG. 3 will be explained.

Reference numeral 1 designates a cathode ray tube, 11 a cathode electrode thereof, 2 a drive circuit, and 3 a data input terminal into which a signal corresponding to a video signal in a well-known standard television broadcast system receiver is input.

Here, the signal input to this terminal 3 is binary code data corresponding to a bright spot on the screen. Further, as is well known, this data is read from the refresh memory, and the details will be omitted. 4 is Read/Write (
A signal indicating that the device is in a writing state is input to a terminal (hereinafter simply referred to as R/W).

This signal is inverted when the device is no longer in the write state, and the user can appropriately select whether the device is in the data write state or only displays data. In addition, this selection operation is performed using the R/W switch provided on the keyboard or the R/W switch provided on the handle of the light pen, as is well known.
This is carried out as appropriate using a W switch or the like, and the above-mentioned signal is inverted in response to this operation. Reference numeral 5 denotes a synchronization input terminal to which a horizontal synchronization signal or a decoded synchronization signal to be applied to a DC clamp circuit and a brightness adjustment circuit in a well-known standard television broadcast receiver is input.

6 is a level control circuit, which includes transistors 61, 62, inverters 63, 64, variable resistors 65, 66, 67, coupling capacitor 68, resistors 69, 70, 71, 72, 73,
It is constituted by a capacitor 74.

Now, when the device is put into the writing state to input zeta on the screen with the light pen, the R/W terminal 4 is LO
A signal of level w (hereinafter simply referred to as 81L1q) is input.

Therefore, the output of the inverter 64 becomes High (hereinafter simply referred to as "H?W") level, and the output of the inverter 6
The output of No. 3 is at the 1LV1 level. On the other hand, data is input to terminal 3, but the output of inverter 63 is WlLlV
Since it is a level, the input zeta is divided by a resistor 69 and a variable resistor 65, and is applied to the next stage DC clamp and brightness adjustment circuit via a coupling capacitor 68.
This circuit has a transistor 61 at its core, a variable resistor 66
, 67, resistors 71, 72, and a capacitor 74. Also, in this circuit, the output of the inverter 64 is now 1.
Since it is at the 1H1 level, the variable resistor 66 becomes irrelevant, and the voltage divided by the resistor 72 and the variable resistor 67 is applied to the emitter of the transistor 61, and the voltage is applied to the collector of the transistor 61 via the coupling capacitor 68. Clamp the applied signal to approximately this voltage. Therefore, the data level shown in FIG. 2A is determined by adjusting the variable resistor 65, and the background level is determined by adjusting the variable resistor 67. This level setting is determined by considering the contrast ratio between the data and the background so that the output pulse obtained by the light pen is stable and optimal. Therefore, the already mentioned second ratio is preset by the variable resistors 65 and 67. Next, when the device is put into a state where only data is displayed, the signal input to the R/W terminal 4 is inverted and ! 2H? An F level signal is input.

Therefore, the output of the inverter 64 is at the 1L17 level, and the output of the inverter 63 is at the 1H level. As a result, since the output of the inverter 63 is at the 1H1 level, the data input to the terminal 3 is gradually applied via the coupling capacitor 68 regardless of the variable resistor 65. On the other hand, since the output of the inverter 64 is at the 1L1V level, the potential of the emitter of the transistor 61 is lowered by current flowing through the variable resistor 66, which has been unrelated. The emitter potential at this time is the resistor 72, variable resistor 66, and 67
Determined by.

Since the variable resistor 67 has been set as described above, the emitter potential at this time is adjusted by the variable resistor 66, which has been unrelated. This emitter potential ultimately determines the background level shown in FIG. 2A, as already mentioned. Therefore, the variable resistor 66 is adjusted so that the background level becomes, for example, a black level as shown in FIG. 1A. Also, since the variable resistor 65 has already become irrelevant to the data level at this time, the resistor 69
For example, 10 as shown in FIG.
It is set to a level of 0%. As a result, when the device is only displaying data, the data and The background level is set. Here, the transistor 8 is a base and emitter follower of the transistor 61 and is coupled via the capacitor 10, and is connected to the synchronous input terminal 5.
The transistor 61 is switched in response to a synchronization signal input to the gate.

As described above, when the device is in the writing state, the level control circuit 5 displays the data and the background on the screen using the second ratio of contrast ratio set by the variable resistors 65 and 67, and the device simply writes the data. In display only mode,
The data and the background are displayed on the screen using the first contrast ratio set by the variable resistor 66 and the resistor 69.

As a result, the output pulses obtained from the light pen when writing data are stable as shown in Figure 2 B, even if the light pen is applied to the positions 2 and E in Figure 2 A. A waveform with a relatively uniform width can be obtained.
Although the above has been explained with reference to an example of a black and white cathode ray tube display device, the present invention can also be applied to a color cathode ray tube display device as shown in FIG.

This example will be described below, and the same or equivalent parts as in FIG. 3 are given the same reference numerals for convenience of explanation. Further, this embodiment exemplifies a well-known three-primary-color demodulation excitation system in which bright spots of each color are displayed by a combination of three primary colors. Therefore, in the embodiment shown in FIG. 4, the level control circuit 6 shown in FIG.
3 is provided. In addition, data input terminals 31 and 32
, 33, red, green, and blue data are input simultaneously, that is, in parallel. Inverter 641, 642,
643 corresponds to the inverter 64 in FIG. In the apparatus of the embodiment shown in FIG. 4 having such a configuration, the red, green, and blue level control circuits 601, 602, and 603 operate in exactly the same manner and simultaneously as the level control circuit 6 shown in FIG. 3. Therefore, the contrast ratio between each of the red, green, and blue data and the background is individually set by each level control circuit 601, 602, 603. As a result, it becomes possible to make the contrast ratios of each of the three primary colors different. This means that, for example, taking into consideration the afterglow time characteristics of the red phosphor, the mixing ratio of the three primary colors can be set to different values in advance for just data display and for data writing. As described above, the present invention can obtain stable output pulses from the light pen without changing the displayed color on the screen during data input.

Furthermore, even if data is written over the display data, the output pulses obtained from the light pen are detected as stable.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the screen brightness level of the cathode ray tube when displaying data, FIG. 2 is a diagram showing the screen brightness level when writing, and FIG. 3 is a circuit diagram of a main part of an apparatus according to an embodiment of the present invention. FIG. 4 shows a block diagram of main parts of an apparatus according to another embodiment of the present invention. 69, 66, 72...゜...゛First circuit means, 65,
67, 72... second circuit means, 63, 64...
...゛Switching circuit means.

Claims (1)

[Claims] 1 Read the data stored in the memory and display it on the screen of the cathode ray tube, detect the position of any data displayed on the screen by applying a light pen, and detect the corresponding position stored in the memory. The cathode ray tube display device reads out data and rewrites it on the screen, and when displaying data on the screen by reading out data from the memory, the contrast ratio between the data on the screen and the background is set to a first value. first circuit means for setting the contrast ratio to a second value smaller than the first value when writing data with the light pen; and second circuit means for setting the contrast ratio to a second value smaller than the first value; means for switching said cathode ray tube from said first circuit means to said second circuit means in response to a signal representing said cathode ray tube display apparatus.