JPH0686170A - Screen display system - Google Patents

Abstract

PURPOSE:To make it possible to display not only black but also the halftone of black in an image by the blank signal. CONSTITUTION:By a BLANK control circuit 12, a P channel MOS transistor 18a and an N channel MOS transistor 18b are almost simultaneously turned ON, partial pressure is performed for power supply voltage Vcc by the internal resistances of these transistors, and as a result of this partial pressure, the output of a BLANK signal 19 of an intermediate level is made possible. By this BLANK signal of the intermediate level, the halftone of black is made to be displayed. Thus, not only black but also the halftone of black can be displayed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screen display circuit device for displaying a black portion on a part of an image on a screen of a television (TV) or the like, and displaying characters, symbols and the like on the black portion. The present invention relates to a screen display device capable of displaying the color of a black portion in black halftone.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing a conventional screen display device. In FIG. 5, 50 is a display circuit, 13 is an R signal for displaying red, 14 is a G signal for displaying green,
15 is a B signal for displaying blue, 19 is a B signal for displaying black
LANK (blank) signal, 51 is CRT (cathode ray tube)
Is. Next, the display operation of the conventional screen display device will be described with reference to FIG.
Will be explained. First, on the TV screen (actually,
Consider a case where "1" is displayed in a black box and then "7" is displayed in a blue box on a part of the video display screen of the television broadcast, as shown in FIG. Now, the R signal 13, the G signal 14, and the B signal 1 in the scanning at the time points (B) and (B ′)
5, waveforms of the BLANK signal 19 are shown in (a) to (d). At this time, the yellow number "1" is displayed by the R signal 13 and the G signal 14 (waveform (a) in FIG. 6,
(B)). The blue number "7" is displayed by the B signal 15 (waveform (c) in FIG. 6). Furthermore, BL
The ANK signal 19 is a signal for cutting the video signal of the television, and is black because the video signal is cut while the BLANK signal is at the "H" level. As a result, the box with the number "1" shown in FIG. 6 becomes black. of course,
The blank signal 19 is output to the CRT 51 even while the numbers "1" and "7" are being displayed, but this is because the video signals are cut, and as a result, the R, G, B signals are numbers, This is to display characters and symbols clearly. if,
If the video signal is not cut by the BLANK signal, for example, the TV image flickers below the numbers "1" and "7", making it difficult to see.

[0003]

The conventional screen display device is configured as described above, and the box of the number "1" can be displayed only in one black color. That is,
Since the BLANK signal has only two levels of "H" and "L" levels, only black display was performed. Therefore, for example, when displaying numbers, characters, symbols, etc. on a part of the image display screen of a television broadcast, it is desirable to display a color other than black (for example, a black halftone in which black is light) depending on the background color. There was a problem that I could not do it.

The present invention has been made in order to solve the above-mentioned problem, and the BLANK signal is a signal having not only the "H" and "L" levels but also the amplitude of the intermediate level, so that the numbers and characters can be reproduced. The color of the box that displays etc. can be displayed not only in black but also in black halftone.
It is an object of the present invention to provide a screen display system capable of obtaining a large amount of black color from a LANK signal.

[0005]

In the screen display system according to the first invention, as shown in FIG. 1, an image signal is partially erased by a blank (BLANK) signal of H level and L level. In the image display system in which a black portion is displayed in an image on a screen of a television or the like by erasing, and characters or symbols of a predetermined color are displayed on the black portion, a power source (Vcc)
And the ground (GND), the first and second switching elements (P-channel MOS transistor 18a, N-channel MOS transistor 18b) are connected in series, and the blank signal (BLANK) is applied between the first and second switching elements. Signal 19) can be output, and only the first switching element on the power supply side is turned on to obtain the H level blank signal, and only the second switching element on the ground side is turned on to set the L level blank. By obtaining a signal and turning on both switching elements, the power supply voltage is divided by the internal resistances of the first and second switching elements, an intermediate level blank signal is obtained by this voltage division, and this intermediate level blank signal is used. A halftone black color different in color from the black color is displayed.

In the screen display system according to the second invention,
As shown in FIG. 3, the image signal is partially erased by blank signals of H level and L level, and by this erasing, a black portion is displayed in the image of the screen of a television or the like, and a predetermined color is displayed in the black portion. In an image display system for displaying characters, symbols, etc., first and second switching elements are connected in series between a power supply (Vcc) and a ground (GND), and the blank is placed between the first and second switching elements. A signal can be output, and a resistor connected in series and a third resistor connected in parallel between the ground point of the first and second switching elements (P-channel MOS transistor 18a, N-channel MOS transistor 18b) and ground. Switching element (resistor 20, N-channel MOS transistor 18c)
To turn on only the first switching element on the power source side to obtain the H level blank signal,
By turning on only the second switching element on the ground side, the blank signal of the L level is obtained, and by turning on the first and third switching elements substantially at the same time, the inside of the first and third switching elements is obtained. The power supply voltage is divided by a resistor, an intermediate level blank signal is obtained by this division, and a halftone black color different from the above black color is displayed by the intermediate level blank signal.

In the screen display system according to the third invention,
As shown in FIG. 4, the resistance connected in series with the third switching element (N-channel MOS transistor 18c) is a variable resistance (resistor 30).

[0008]

In the screen display system according to the first aspect of the present invention, the first and second switching elements (P-channel MOS transistor 18a and N-channel MOS transistor 18b) connected in series between the power supply and the ground are provided, and both transistors are provided. The BLANK signal of the intermediate level can be output in addition to the BLANK signal of the H level and the L level by controlling the. That is, H-level BLAN
When the K signal is obtained, only the first switching element on the power supply side is turned on, when the BLANK signal of the L level is obtained, only the second switching element on the ground side is turned on, and when the BLANK signal of the intermediate level is obtained, both are turned on. Controls to turn on the transistor. Of these controls, when turning on the first and second transistors at substantially the same time, these first and second transistors are turned on.
The power supply voltage is divided by the internal resistance of the transistor, and a BLANK signal at an intermediate level is obtained by this division, and a black halftone display different from the conventional black can be displayed.

In the screen display system according to the second invention,
In addition to the switching elements of the first and second transistors described above, a series-connected resistor and a third switching element were provided in parallel between the first and second switching elements and the intermediate point and ground. The BLANK signals of H and L levels are controlled by the same control method as the screen display method of the first invention described above. Further, the intermediate level BLANK signal is obtained by dividing the internal resistances of the first and third switching elements by turning on the first and third switching elements substantially at the same time. As a result, the black color can be changed by arbitrarily selecting the resistance value.

In the screen display system according to the third invention,
By changing the resistance used in the screen display method according to the second invention to a variable resistance, the black color to be displayed can be arbitrarily changed.

[0011]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 shows an embodiment (embodiment 1) of the first invention.
3 is a block diagram of a screen display device showing FIG. In FIG. 1, 10 is a display circuit including a semiconductor integrated circuit, 11 is a display unit, 13 is an R signal for displaying red, 14 is a G signal for displaying green, and 15 is a B signal for displaying blue. . These R signal 13, B signal 15, and G signal 14 are all output to the CRT. Reference numeral 16 is a character signal for displaying characters, symbols and the like, 17 is a control signal, and 12 is a BLANK control unit for performing control for outputting a blank signal. 18a is a P-channel MOS transistor as a first switching element, and 18b is an N-channel MOS transistor as a second switching element.

P-channel MOS transistor 18a
Has a source side connected to the power supply voltage Vcc and a drain side connected to the drain side of the N-channel MOS transistor 18b. The source side of the N-channel MOS transistor 18b is connected to the ground (GND),
A connection point (intermediate point) with the P-channel MOS transistor 18a is connected with a CRT (not shown). This P channel MOS transistor 18a and N channel M
The OS transistor 18b and the BLANK control unit form a buffer circuit, and the BLANK control unit 12 controls the gates of both these transistors,
The BLANK signal 19 of "H" level, L level and intermediate level is output to the CRT. That is, the BLANK control circuit 12 causes the BLAN of the "H" level when only the P-channel MOS transistor 18a on the power supply side is on.
When the K signal 19 is output and only the ground-side N-channel MOS transistor 18b is on, the BLANK signal 19 of "L" level is output, and when both transistors are on, an intermediate level (for example, about 2.5V) The BLANK signal of is output to the CRT. When both the transistors are on, the power supply voltage Vcc is divided by the internal resistances of the P-channel MOS transistor 18a and the N-channel MOS transistor 18b, and as a result of this division, an intermediate level signal is obtained. Then, the BLANK signal of the intermediate level causes the black halftone to be displayed on the video screen of the television or the like.

FIG. 2 is a diagram showing a display operation in the device of the first embodiment. In FIG. 2, (a) to (d)
Are the R signal 13, G signal 14, and (A) and (A ') scanning points in the numbers "1", "7", and "2" in FIG.
The waveforms of the B signal 15 and the BLANK signal 19 are shown.
(E) is a video signal for displaying an image on the screen, (f)
Is a BLANK signal of H level and intermediate level, and (g) is a video signal for outputting characters. As shown in Fig. 2, when displaying a yellow number "1" in a black box, displaying a blue number "7", and displaying a number "2" in a black halftone box, R obtained by the display circuit described above
Use the G and B signals and the BLANK signals of "H" level, "L" level and intermediate level. Video signal is "H"
The amplitude of the signal is cut by BLANK at the level and the intermediate level (waveforms (e) to (g) in FIG. 2). This cut part (black part where the image in the image is erased)
In accordance with the signals (a) to (d), "1", "7",
Display the number "2". In this way, when the amplitude of the video signal is cut in half, the tone of the video to be displayed is reduced compared to the video portion of the other video signal, resulting in a black halftone. Further, for example, for the display portion of the number "2", the display of the number "2" becomes clear by completely cutting the video signal. The BLANK signal at this time is at the “H” level as shown in (d).

Next, the operation of the first embodiment will be described. As shown in FIG. 2, when displaying the number "1",
An instruction is issued from the CPU (not shown) to the display unit 11 of the display circuit 10. The display unit 11 outputs a character signal 16 of “1” and a control signal 17 to the BLANK control unit 12,
Controls the LANK controller. First, P channel MOS
Only the transistor 18a is turned on to output the "H" level signal (FIG. 2). At this time, the video signal is cut and the black box in FIG. 2 is displayed in the image. on the other hand,
The display unit 11 has an R signal 13 and a G signal 14 for the CRT.
Is output and the yellow number "1" is displayed.

Next, when displaying the number "2", the CP
After the instruction from U, the display unit 11 displays the BLANK control unit 1
A character signal 16 of "2" and a control signal 17 are output for 2 to control the BLANK control unit 12. The BLANK control unit 12 turns on only the P-channel MOS transistor 18a and CRs the BLANK signal 19 of "H" level.
Output to T, then P channel MOS transistor 1
Both the 8a and N-channel MOS transistors 18b are turned on substantially at the same time, and the intermediate level
The signal 19 is output to the CRT (waveform (d) in FIG. 2). This intermediate level BLANK signal is obtained by dividing the power supply voltage by the internal resistance of both transistors as described above. On the other hand, the display unit 11 displays the white number "2".
In order to display, the R signal 13, the G signal 14, and the B signal 15 are output to the CRT during the output of the BLANK signal ((a) to (c) of FIG. 2). At this time, only the portion displaying the number "2" has the BLANK signal of the "H" level. Therefore, the number display of "2" becomes clear.

FIG. 3 is a circuit block diagram of a screen display device showing an embodiment (embodiment 2) of the second invention. Figure 3
18c is N as the third switching element.
The channel MOS transistor, 20 is a resistor and has the same configuration as that of the first embodiment except for the above. One end of the resistor 20 is connected to the drain side of the N-channel MOS transistor 18c, and the other end is connected to the P-channel MOS transistor 18a and N-channel.
It is connected to the connection point with the channel MOS transistor 18b. Also, the N-channel MOS transistor 1
The source of 8c is connected to the ground (GND).
The channel MOS transistor 18c is controlled by the BLANK controller 12. In this second embodiment, "H"
The operation when the BLANK signal 19 of the level "L" is output is the same as that in the first embodiment. The operation is different when the BLANK signal of the intermediate level is output. At this time, the P-channel MOS transistor 18
The a and N channel MOS transistors 18c are turned on almost at the same time. As a result, the power supply voltage Vcc is divided by the internal resistance of the P channel MOS transistor 18a and the N channel MOS transistor 18b and the resistance 20.
The resistance value of the resistor 20 is determined in advance at the design stage. B output from the display circuit of the second embodiment
The LANK signal can be set to BLA by selecting the resistance value.
The level of the NK signal can be changed to change the black halftone color from a color close to white to a color close to black.

FIG. 4 is a circuit block diagram of a screen display device showing an embodiment (embodiment 3) of the third invention. Figure 4
In, 30 is a variable resistance. The configuration is almost the same as that of the second embodiment, except that the resistance is a variable resistance. With this variable resistor, the black halftone color can be freely changed. In particular, by externally attaching this variable resistor, the user can freely change the color of the black portion displayed in a part of the image according to his / her preference.

[0018]

As described above, according to the first aspect of the present invention, by turning on the first and second switching elements substantially at the same time, an intermediate level is generated between the first and second switching elements. The blank signal can be output, so that there is an effect that a black halftone can be displayed with a simple structure.

According to the second aspect of the invention, since the resistor and the third switching element are further added, in addition to the effect of the first aspect of the invention, black color can be changed by the resistance value of the resistor. There is an effect that can be done.

According to the third aspect of the invention, since the resistance connected to the third switching element is a variable resistance, in addition to the effect of the first aspect of the invention, a black color is used as the variable resistance. There is an effect that the resistance value can be changed arbitrarily.

[Brief description of drawings]

FIG. 1 is a block diagram of a screen display device showing an embodiment of the first invention.

FIG. 2 is a diagram showing a display operation of the device of FIG.

FIG. 3 is a block diagram of a screen display device showing an embodiment of the second invention.

FIG. 4 is a block diagram of a screen display device showing an embodiment of the third invention.

FIG. 5 is a block diagram showing a conventional screen display device.

6 is a diagram showing a display operation in the device of FIG.

[Explanation of symbols]

 10 display circuit 11 display section 12 BLANK control section 13 R signal 14 G signal 15 B signal 16 character signal 17 control signal 18a P-channel MOS transistor 18b, 18c N-channel MOS transistor 20 resistance 30 variable resistance

Claims (3)

[Claims] 1. An image signal is partially erased by a blank signal of H level and L level, a black portion is displayed in an image on a screen of a television etc. by this erasing, and a character of a predetermined color is displayed on the black portion. In an image display system for displaying symbols and the like, first and second switching elements are connected in series between a power source and ground, and the blank signal can be output between the first and second switching elements. First on the side
By turning on only the switching element of, the H level blank signal is obtained, and by turning on only the second switching element on the ground side, the L level blank signal is obtained and both switching elements are turned on. The power supply voltage is divided by the internal resistance of the first and second switching elements, an intermediate level blank signal is obtained by this division, and a halftone black color different from the above black color is displayed by this intermediate level blank signal. A screen display method characterized in that 2. An image signal is partially erased by a blank signal of H level and L level, a black portion is displayed in an image on a screen of a television or the like by this erasing, and a character of a predetermined color is displayed on the black portion. In the image display system for displaying symbols and the like, the first and second switching elements are connected in series between the power supply and the ground, and the blank signal can be output between the first and second switching elements. By connecting a series-connected resistor and a third switching element in parallel between the intermediate point of these first and second switching elements and ground, and turning on only the first switching element on the power supply side, A blank signal of H level is obtained, and the blank signal of L level is obtained by turning on only the second switching element on the ground side, and the first and third switching elements are almost By turning on at the same time, the power supply voltage is divided by the internal resistances of the first and third switching elements, a blank signal of an intermediate level is obtained by this division, and a half signal different from the black color and the color is obtained by the blank signal of the intermediate level. A screen display method characterized by displaying a black tone. 3. The screen display system according to claim 2, wherein the resistance connected in series with the third switching element is a variable resistance.