JPH035715B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a character/graphic signal superimposition device, more specifically, a method for superimposing predetermined character/graphic information on image information received by a television receiver, or for superimposing the character/graphic information independently. This invention relates to a superimposing device for displaying images on a computer.

As shown in FIG. 1 or 2, this type of superimposing device has conventionally been used, for example, on the input side of a drive circuit 2 for driving a CRT 1 (cathode ray tube) of a color television receiver, or on the input side of a drive circuit 2 for driving a CRT1 (cathode ray tube) of a color television receiver. on the output side of the color television receiver.
A color signal representing image information from IC3 (integrated color signal demodulation circuit) and a color signal representing character/graphic (hereinafter referred to as text character) information from a teletext receiver or teletext receiver (not shown) are used. A mixing circuit 4 or 4' for mixing is provided, and a switching device is provided between the chroma IC 3 and the mixing circuit 4, or between the chroma IC 3 and the drive circuit 2, which operates a switch based on the above-mentioned text character signal to be superimposed. Circuit 5 or 5'
and is configured to block the color signal output from the chroma IC 3 for a period corresponding to the text character signal so that the text character portion superimposed on the color image received by the television receiver does not mix colors. It is publicly known.

However, in the conventional superimposing device described above, the switching circuit 5 and the mixing circuit 4 or the switching circuit 5' are connected to the chroma IC 3 and the drive circuit 2 mounted on the main circuit board (not shown) in the television receiver. The connection mechanism for connecting the mixing circuit 4' is very complex and requires a large number and fairly long lead wires;
However, due to the stray capacitance of the lead wire, the CRT
The problem was that the color signals of the image information to be displayed on the CRT 1 were adversely affected, resulting in a decrease in the quality of the image displayed on the CRT 1.

Furthermore, as described above, since the switching circuit and the mixing circuit are separated, the timing of applying the text character signal to be superimposed to the mixing circuit and the switching circuit controlled based on the text character signal can be adjusted. There is a "lag" between the movement timing and the text characters displayed on the CRT 1, resulting in black level parts, so-called black edges, which are extremely difficult to distinguish, especially when the displayed text characters are small. There was also a drawback.

The present invention was made to eliminate the above-mentioned drawbacks, and the demodulated television image is connected to the base of the transistor in the input stage of an amplifier circuit configured using at least two transistors so that the amplification factor is 1. A cutoff signal is generated based on a superimposition video information signal to be superimposed on the television image signal while inputting the signal, and is used to cut off a portion of the television image signal that corresponds to the superimposition video information signal. is applied to the base of the transistor in the output stage of the amplifier circuit, and
By applying a signal representing the superimposition video information to the output terminal of the transistor in the output stage, the superimposition video information with good image quality is displayed on the video screen of the television receiver together with the television image or alone. To provide a character/graphic signal superimposition device that can be easily connected to an existing television receiver without changing the circuit configuration of the existing television receiver.

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

As shown in FIG. 3, a superimposing device 10 according to the present invention includes, for example, a receiving device 11 provided in a color television receiver (hereinafter referred to as a television receiver) for receiving commercial television broadcast signals.
A plug-in connection is made between a chroma IC (not shown) in the television receiver and a drive device 12 that drives the CRT 13 of the television receiver.

The superimposing device 10 receives from the chroma IC in the receiving device 11 three color signals (hereinafter, three color signals representing demodulated color image information of a television broadcast signal received by the television receiver). The signals are R (red) signal, G (green) signal, and B (blue) signal) are input, as well as a horizontal blanking signal (hereinafter referred to as To,
For example, a signal (hereinafter referred to as a text character signal) representing information such as characters or figures received by a teletext receiver (hereinafter referred to as a text character signal) is transmitted from a teletext receiver (not shown as it is a known one). ) (hereinafter, these color signals will be referred to as R' signal, G' signal, and B' signal) are input.

The superimposing device 10 uses the above-mentioned R signal, G signal, B signal, (R'+G'+B') signal, and R' signal, G' signal, and B' signal to perform a process on the CRT 13 using a method described in detail later. A drive signal is generated to control the operation of the drive circuit 12 so that a color image with text superimposed on a television image, or a color image of text characters alone, is displayed on the screen.

FIG. 4 shows the basic components of the superimposing device 10.

In FIG. 4, the basic circuit 15 for superimposition shown surrounded by a dashed line consists of two PNP transistors 1
6 and PNP transistor 17, resistor 18,
19, 20, and 21, an amplifier circuit 22 is connected in a complementary manner so that the amplification factor is 1, and a first logic gate IC 23 is connected to the base of the NPN transistor 17 in the output stage of the amplifier circuit 22. , and a second logic gate IC25 connected to the output terminal 24 of the amplifier circuit 22. Note that this amplifier circuit 22 may be configured using an NPN transistor in the input stage and a PNP transistor in the output stage.

First and second logic gates IC23 and 2
5 are both formed by integrating open collector type transistors, for example. A signal (BLK+R'+G'+B') consisting of the above-mentioned text character signal to be superimposed and a blanking signal is applied to the first logic gate IC23,
The second logic gate IC25 has the above (BLK+
R′+G′+B′) signal, and a signal obtained by inverting the R′ signal, G′ signal, and B′ signal from a control signal generation circuit 31, which will be described in detail later, in the superimposing device;
A G' signal and a ' signal are applied.

In the superimposing device according to the present invention, the chroma IC in the receiving device 11 receives color signals of three primary colors, that is,
In the case of a demodulation circuit of a type that outputs an R signal, a G signal, and a B signal, three basic circuits 15 are provided corresponding to each color signal. In addition, the chroma IC is a color difference signal, that is, an R-Y signal, a G-Y signal,
In the case of a demodulation circuit of a type that outputs a B-Y signal, four basic circuits 15 are provided corresponding to each color difference signal and luminance signal (Y signal).

Next, a specific example of a superimposing device in the case where the chroma IC is a color signal demodulation circuit of a type that outputs three primary color signals will be described with reference to FIGS. 5 and 6.

In FIG. 5, 30-R, 30-G, 30-
Both of B are amplifier circuits equivalent to the amplifier circuit 22 in the basic circuit 15 described above. The input stage of each amplifier circuit 30-R, 30-G, 30-B
The base of each PNP transistor has a chroma IC (not shown) in the TV receiver.
, the demodulated R signal, G signal, and B signal of the three primary colors of the television image signal received by the television receiver.
A signal is now applied.

31 is a control signal generation circuit that generates a control signal for superimposing a text character signal on the television image signal received by the television receiver.
This control signal generation circuit 31 generates, for example, R' signals of three primary colors representing color text characters to be superimposed from a teletext receiver (not shown);
A blanking signal (hereinafter referred to as a BLK signal) is connected to the teletext receiver so as to receive the G' signal and the B' signal, and is transmitted from a blanking signal generating circuit (not shown) provided in the teletext receiver. ) is connected to the blanking generation circuit. The control signal generation circuit 31 includes, for example, inverters 32-R and 32-R using open collector transistors.
G, 32-B, the output stage of each of the above-mentioned amplifier circuits 30-R, 30-G, 30-B, respectively.
At the base of the NPN transistor, (BLK+R′+
G'+B') signal, and the collectors of the output stage transistors in each amplifier circuit 30-R, 30-G, 30-B, i.e.
Output terminals 33-R, 33- in the superimposing device
NAND gate 3 connected to G and 33-B respectively
The above-mentioned (BLK+R'+G'+B') signal is commonly connected to one input terminal of 4-R, 34-G, and 34-B. Further, the control signal generation circuit 31 includes each of the NAND gates 3 described above.
Connected to the other input terminals of 4-R, 34-G, and 34-B so as to apply the 'signal, 'signal, and 'signal, which are inverted polarities of the R'signal, G'signal, and B'signal, respectively. are doing.

The above inverters 32-R, 32-G, 32-B
is a circuit corresponding to the first logic gate IC23 in the basic circuit 15 described above, and the NAND gates 34-R, 34-G, and 34-B are the circuits corresponding to the second logic gate IC23 in the basic circuit 15 described above.
This circuit corresponds to the logic gate IC25.

Furthermore, output terminals 33-R, 33-G, 33-
B is for each television receiver.
It is connected to a drive circuit (see Fig. 3) connected to the three R, G, and B cathode terminals of the CRT 13 (see Fig. 3). This drive circuit is similar to the conventional drive circuit shown in FIGS.
It is constructed using three power transistors for driving the R, G, and B cathodes.

In the superimposing device having the above configuration, a color image is basically projected on the CRT 13 of the television receiver in the projection modes (1) to (3).

(1) Picture mode (hereinafter referred to as PIC mode) that displays only the color image of the television signal received by the television receiver.

(2) For example, a color image of text characters from a teletext receiver is superimposed and displayed on the color image of the television signal; MIX mode (hereinafter referred to as MIX mode).

(3) Display only the color image of the above text characters; text mode (hereinafter referred to as TEXT mode) In the circuit shown in Figure 5, the demodulated output from the chroma IC in the television receiver, that is, R, G, and B signals are blocked or killed based on the following conditions.

(a) In TEXT mode, block the entire image based on the television signal; BLK=1 (b) Block the part of the television image corresponding to the text character to be superimposed; R'+G'+B'=
1 In order to satisfy the above (a) and (b), BLK+R+G+B=...

Furthermore, in order to drive the drive circuit 12 according to the color output from the chroma IC, the color output is applied to the drive circuit 12 based on the following conditions,
That is, it passes through the superimposing device. Note that the color output is shown only for the red component, and the same applies to the other green and blue components, so these will be omitted.

(1) In TEXT mode, pass through the red part of the text character; BLK・R=1 (2) In MIX mode, pass through the red part of the text character; ・R=1 (3) In PIC mode;...= 1 (4) In MIX mode, pass through parts that do not correspond to text characters; ... = 1 On the other hand, block or kill the color output from the chroma IC mentioned above. Note that the color output is shown only for the red component, and the same applies to the other green and blue components, and these will be omitted.

(5) In text mode, type the text character G′ or
Block or kill the part corresponding to B′; BLK・G・＋BLK・B・=1 (6) In MIX mode, block or kill the part corresponding to text character G′ or B′; ・G・+・B・=1 (7) In TEXT mode, block or kill the part that does not correspond to the text character signal; BLK...=1 The conditions (1) to (7) above are shown in the VEITCH diagram. It will look like Figure 6.

The above-described superimposition device shown in FIG. 5 is similar to that shown in FIG.
This is a circuit that satisfies the conditions of the VEITCH diagram.

Next, the operation of the superimposing device having the above configuration is shown in FIG.
This will be explained with reference to FIGS. 7a, b, and c and FIG. 8.

Each red (R) component, green (G) component, and blue component of the demodulated color output from the chroma IC in the TV receiver
(B) components are amplifier circuits 30-R and 30-, respectively.
G, 30-B in the input stage PNP transistor (denoted as Tr-1 in FIG. 5), while trying to superimpose the demodulated color output from the teletext receiver (not shown) on the television image. A red (R') component, a green (G') component, and a blue (B') component are applied to the control signal generation circuit 31 for the portion of the text character to be displayed.

In the case of MIX mode, the text characters are now red, i.e.
R'="1", G'="0", and B'="0", and this period is defined as _T1 . It is also assumed that a blanking signal (hereinafter referred to as a BLK signal) = "0" is applied to the control signal generating circuit 31 from a blanking signal generating circuit (not shown) in the teletext receiver.

During period _T1 , the control signal generation circuit 31:
(BLK+R′+G′+B′)=“0”+“1”+“0”+
“0” = “1” signal to each inverter 32-R, 3
2-G, 32-B, and the signal "1" is applied to each inverter 32-R, 32-G,
32-B, and this signal "0" is inverted to "0" by the amplifier circuits 30-R and 30-B, respectively.
It is applied to the base of the PNP transistor (denoted as Tr-1 in FIG. 5) in the input stage at 0-G and 30-B. Further, the control signal generation circuit 3
1 sends the ′=“0”, ′=“1”, and ′=“1” signals to the NAND gates 34-R, 34-G, and
34-B to the other input terminal, and the above (BLK+R′+G′+B′)=“1” signal,
Each NAND gate 34-R, 34-G, 34-B
Therefore, each NAND gate 34-R, 34-G, 34-B applies the logically determined "1", "0", "0" signal to each amplifier circuit, respectively. 30-R, 30-G,
It is applied to the collector of the NPN transistor (denoted as Tr-2 in FIG. 5) in the output stage at 30-B.

As a result, in the amplifier circuit 30-R, the R signal from the chroma IC is applied to the base of the transistor Tr-1, and the transistor Tr-1
A voltage corresponding to the R signal is output to the collector of the amplifier circuit 30-R, and this voltage is applied to the base of the transistor Tr-2 of the amplifier circuit 30-R. Further, a "0" signal is applied from the inverter 32-R to this transistor Tr-2, and the base potential of this transistor Tr-2 decreases and is cut off, so that this transistor Tr-2 is cut off.
The collector output of -2 becomes approximately zero, as shown in FIG. 7b. Further, a "1" signal is applied to this collector output from the NAND gate 34-R, and the collector voltage, that is, the output terminal 33-R of the amplifier circuit 30-R has a high voltage as shown in FIG. 7c. A voltage appears, ie a voltage corresponding to the red component of the text character portion.

On the other hand, in the amplifier circuit 30-G, G from the chroma IC is applied to the base of the transistor Tr-1.
A signal is applied, and a voltage corresponding to the G signal appears at the collector of the transistor Tr-1, and therefore at the base of the transistor Tr-2, in the same way as in the amplifier circuit 30-R described above. A "0" signal is applied from 32-G to the base of transistor Tr-2, and the transistor Tr-2 is cut off. Therefore, the collector output of this transistor Tr-2 is applied to the base of the transistor Tr-2 in the above-mentioned amplifier circuit 30-R. Similar to the collector output of Tr-2, it becomes approximately zero. Furthermore, this transistor Tr-2
A "0" signal is applied from the NAND gate 34-G to the collector of the amplifier circuit 30-G.
Unlike the case in R, the transistor Tr
−2 collector output, therefore output terminal 3
The voltage of 3-G is approximately zero. That is, of the green component of the television image signal, a portion corresponding to the text character portion (red component) to be superimposed is killed.

Also, in the amplifier circuit 30-B, similarly to the above-mentioned amplifier circuit 30-G, the collector of the output stage transistor Tr-2 is connected to the collector of the output stage transistor Tr-2.
A signal "0" is applied from the NAND gate 34-B, thereby killing a portion of the blue component of the television image signal that corresponds to the text character portion (red component) to be superimposed.

As a result, in period T ₁ , drive circuit 1
A transistor (not shown) connected to the R cathode terminal of the CRT 13 in No. 2 is turned on by receiving (R+R') from the output terminal 33-R of the superimposing device, and is connected to the G and B cathode terminals of the CTR 13, respectively. The connected transistors (not shown) both have output terminals 33-G,
It receives a substantially zero signal from 33-B and is turned off. Therefore, on the screen of CRT13, in Figure 8,
As shown in area A, the red portion of the text is displayed superimposed on the television image,
In addition, the green (G) component and the blue (B) component of the overlapping portion of text characters in the television image are killed as described above, and this overlapping portion is correctly colored red without causing color mixture. Display.

Next, the text characters are green, i.e.
The operation for period _T2 in which R'=“0”, G’=“1”, and B’=0 will be explained. In addition, BLK="0"
Suppose that

During period T ₂ , in the same manner as in period T ₁ described above, the control signal generation circuit 31 supplies each inverter 32-R, 32-G, and 32-B with
Commonly, (BLK+R′+G′+B′)=“0”+“0”+
While applying “1” + “0” + “0” = “1” signal,
To the two input terminals of NAND gate 34-B,
(BLK+R′+G′+B′)=“1” and′=“0”
is applied, and each NAND gate 34-R, 3
“1” to each of the two input terminals of 4-B
and '="1", "1" and '="1" are applied.
Therefore, each amplifier circuit 3 is connected to each amplifier circuit 3 from each number gate 34-G, 34-R, and 34-B.
Signals "1", "0" and "0" are applied to the collectors of the output stage transistors Tr-2 in 0-G, 30-R and 30-B.

The amplifier circuit 30-G operates during the above-mentioned period T ₁
In the same way as the amplifier circuit 30-R in , the (G+G') signal is sent to the output terminal 33-G, and the other amplifier circuits 30-R and 30-B
The collector outputs of both are approximately zero, therefore, the output terminals 33-R and 33-B are both approximately zero.

Note that during this period _T2 , as an example of an operation for suppressing the above-mentioned color mixture, the amplifier circuit 30
The collector output of the transistor Tr-2 in the output stage at -R is shown in FIG. 7c.

As a result, in the drive circuit 12, the CRT
A transistor (not shown) connected to the G cathode terminal of No. 13 is turned on, and the CRT
The transistors (not shown) connected to the R and B cathode terminals of No. 13 are both:
It is considered off. Therefore, on the CRT13 screen,
As shown in area B in Figure 8, the above period
As in _T1 , the green portion of the text character is displayed superimposed on the television image without color mixing with the red and green components of the television image.

Furthermore, in period T ₃ , the text character part is blue, that is, R′=“0”, G′=“0”,
When B′=“1” and BLK=“0”, the blue part of the text character is the red component of the television image in the same way as in the periods T ₁ and T ₂ described above. and is displayed superimposed on the television image without color mixing with the green component.

In addition, in this period _T3 , the above-mentioned operation of suppressing color mixture is taken as an example, and the above-mentioned amplifier circuit 30
The collector output of the transistor Tr-2 in the output stage at -R is shown in FIG. 7c.

On the other hand, in the above period _T1 , along with the R' signal representing the red component of the text character part, the G' = "1" and B' = "1" signals representing the green component and blue component of the character part. is applied to the control signal generation circuit 31, each amplifier circuit 30-R, 30-
Output stage transistor in G, 30-B
"1", "1", "1" signals are applied to the collector output of Tr-2 from NAND gates 34-R, 34-G, and 34-B, respectively, and the text character part is a television image. output terminal 33-R, without color mixing with the color signal of
33-G and 33-B each have (R+
R'), (G+G'), and (B+B') appear. As a result, based on the operation of the drive circuit 12 described above, the portion of the television image corresponding to the text character portion is displayed in white on the screen of the CRT 13. This state is shown by area c in FIG.

Further, for example, when a BLK="1" signal is output from a blanking generation circuit (not shown) provided in the teletext receiver during the period _T1 , this signal BLK="1" is output.
is applied to the above-mentioned chroma IC in addition to the control command signal generation circuit 31, and the output of the demodulated color signal from the chroma IC is stopped. As a result, the above
On the screen of the CRTP 13, as shown by area D in FIG. 8, a red portion of the text character against a black background is displayed in a pixel area that displays the text character portion.

In the case of TEXT mode, the input of color signals R, G, and B from the chroma IC to each amplifier circuit 30-R, 30-G, and 30-B in the TV receiver is prohibited, and A BLK="1" signal is applied to the control signal generation circuit 31 from a blanking signal generation circuit (not shown). Further, from the teletext receiver, the control signal generation circuit 31 receives an R' signal, a G' signal, and a G' signal representing the text characters received by the teletext receiver.
B′ signal is applied.

The above text characters are red, i.e.
When R′=“1”, G′=“0”, and B′=“0”, the control signal generation circuit 31 generates (BLK+R′+G′+
B') = (“1” + “1” + “0” + “0”) = “1”
The signal is inverter 32-R, 32-G, 32-B
Each amplifier circuit 30-R, 30-G, 3
Output stage transistor Tr-2 at 0-B
is applied to the base of In addition, the above (BLK+
R′+G′+B′)=“1” signal is for each NAND gate 3
It is applied to one input terminal of 4-R, 34-G, 34-B, and the control signal generation circuit 31
'="0", '="1", and '="1" are respectively applied to the other input terminal of each NAND gate. Therefore, these Nand Gate 3
Output signals "1", "0", "0" from 4-R, 34-G, 34-B are output to the output stage transistor Tr in each amplifier circuit 30-R, 30-G, 30-B, respectively. -2 collector.

As a result, (R+R')=(0+
R') = R' appears, while the other output terminal 33-
Substantially zero voltage appears in both G and 33-B. These output signals, R', 0, 0, are applied to the drive circuit 12, and thus the CRT 13
On the screen, as shown in area E in Figure 8,
A red portion of the text character against a black background is displayed within the pixel area displaying the portion of the text character.

Also, the text character part from the teletext receiver is white, i.e., R′=“1”, G′=
"1", B'="1", or blue, that is, K'="0", G'="0", B="1", or green, that is, R ′=“0”,
When G'="1" and B'="0", they are displayed on the screen of the CRT 13 as shown in areas F, G, and H in FIG. 8, respectively.

In the case of PIC mode, the control signal generation circuit 31 is turned off, and from this control signal generation circuit 31, (BLK+B'+R'+
B′) signal and ′, ′, ′ signal are not output. Therefore, each amplifier circuit 30-R, 30-
G, 30-B is an R signal representing a television image from the Chroma IC in the television receiver;
Upon receiving the G signal and B signal, these color signals are amplified with an amplification factor of 1, that is, each color signal is outputted to the output terminal 33- without changing the color signal.
It is applied to the CRT drive circuit 12 via R, 33-G, and 33-B. Therefore, only the color television image received by the television receiver is displayed on the screen of the CRT 13.

Next, the chroma IC generates three color difference signals R-
FIG. 9 shows a specific example of a superimposing device in the case of a color signal demodulation circuit of a type that outputs Y, G-Y, B-Y and a luminance signal Y.

Note that in FIG. 9, parts equivalent to those in FIG. 5 are given the same reference numerals and explanations will be omitted.

In FIG. 9, as mentioned above, basic circuit 1
Amplification circuits 30-R, 30-G, 30- equivalent to 5
B, 30-Y are provided, and the receiving device 12 (see FIG. 3) is provided at the base of the transistor Tr-1 of each input stage in these amplifier circuits.
The color difference signals R-Y, G- are generated from the chroma IC in a known method based on the demodulated color signals of the television image received by the television receiver.
Y, B-Y, and a luminance signal Y are connected to be input.

In FIG. 9, a control signal generating circuit 31 shown enclosed by a dashed line is configured to generate a text character from a teletext receiver (not shown), for example.
Input terminals 36-R, 36-G, 36-B connected to receive R' signal, G' signal, and B' signal
are connected to open collector type NAND gates 34-R, 34- via open collector type inverters 37-R, 37-G, and 37-B, respectively.
It is connected to the other input terminal of G and 34-B.
Further, the input terminal 36-BLK connected to receive the blanking signal BLK from the teletext receiver is connected to one input terminal of the two-input NAND gate 39 via the inverter 38-BLK. , the above-mentioned input terminal 36-R,
36-G and 36-B are inverter 3, respectively.
It is commonly connected to the other input terminal of the NAND gate 39 via 8-R, 38-G, and 38-B. The output terminals of the NAND gate 39 are the aforementioned NAND gates 34-R, 34-G, 3.
(BLK+) is commonly connected to one input terminal of 4-B.
It is connected to input the R′+G′+B′) signal. Further, the output terminal of the NAND gate 39 is connected to an open collector type inverter 43 and a variable resistor 44.
is connected to the collector of the transistor Tr-2 in the output stage of the amplifier circuit 30-Y.
Further, one input terminal of this NAND gate 39 is connected to the output of the amplifier circuit 30-Y via an inverter 40, an open collector inverter 41, and a variable resistor 42 provided outside the control signal generating circuit 31. stage transistor
It is connected to the collector of Tr-2 so as to input the ('+'+') signal.

The collectors of the output stage transistors Tr-2 in the amplifier circuits 30-R, 30-G, and 30-B are connected to a resistor 45-R and a capacitor 46-, respectively.
NAND gate 34 through a filter circuit consisting of R, 45-G and 46-G, 45-B and 46-B.
-R, 34-G, 34-B, and the output terminal 33- of the superimposing device.
Connected to R, 33-G, and 33-B. Furthermore, the collector of the output stage transistor Tr-2 in the amplifier circuit 30-Y is connected to the output terminal 33-Y via the base-emitter of a PNP transistor 47 whose collector is grounded.

50 is the output terminal 33- in the superimposing device.
This clamp circuit 50 is a clamp circuit for controlling the output level of the output terminals 33-R, 33-G, and 33-B to a predetermined level, as shown in FIG. , 33-B and the diodes 51-R, 51-G, 51-, respectively connected to
A (++) signal is input from the other input terminal of the NAND gate 39 in the control signal generation circuit 31 to the transistor 52 whose collector is common to the anodes of these diodes and the base of the transistor 52. It is composed of a variable resistor 53, an open collector type inverter 54, and an inverter 55, which are connected so as to be connected to each other.

The operation of the superimposing device having the above configuration is basically the same as when using the device shown in FIG. If the characters are in MIX mode, TEXT mode, or
In the PIC mode, the text characters are displayed superimposed on the screen of the CRT 13 without color mixing with the television image. The operation of this superimposing device is almost the same as that of the device shown in FIG. 5 described above, and the explanation of the operation will be omitted.

As described above, in the superimposition apparatus shown in FIGS. 5 and 8, the text characters to be superimposed applied to the first logic gate 23 (inverters 32-R, 32-G, 32-B) are (R′+
G'+B') Based on the signal, the amplifier circuits 30-R, 30 are
-G, 30-B, among the color signals representing the television image input, the operation of killing the color signal of the part corresponding to the text characters and superimposing or mixing the text characters on the television image. This can be done simultaneously and reliably superimposes the text characters to be superimposed onto the television image on the television receiver's video screen while preventing color mixing with the red, green, and blue components of the television image. It is possible to display clear images even when

Furthermore, in the superimposing device having the above configuration, the portion of the television image signal on which text characters are to be superimposed is cut off, and the television image signal and the text characters are mixed, as in conventional devices. The amplifier circuit 30 is integrated without using separate switching means and mixing means.
-R, 30-G, and 30-B, the connecting lead wires between the component parts can be shortened to the minimum necessary length, which reduces noise in the color signals transferred between the component parts. It is possible to display a high-quality image on the screen of a television receiver by suppressing the occurrence of this phenomenon.

Furthermore, the superimposition device with the above configuration simply connects the input terminal of the amplifier circuit in the superimposition device and the output terminal of the device to the chroma IC in the existing television receiver and the drive circuit for driving the CRT, respectively. It can be easily installed in a so-called plug-in manner without changing the circuit configuration provided on the chassis of the television receiver.

In the above embodiment, the case where color text characters are superimposed on a color television image has been described. However, when monochrome text characters are superimposed on a monochrome television image, the television image in the superimposition device is A demodulated image signal of a monochrome television signal is commonly applied to input terminals for R, G, and B signals, and a demodulated image signal of a monochrome television signal is commonly applied to input terminals for R, G, and B text character signals in a control signal generation circuit. , in common,
By applying a monochrome text character signal, the superimposition device can be used in both color and monochrome applications.

As is clear from the above description, according to the present invention, while applying a demodulated television image signal to the input terminal of an amplifier circuit configured using at least two transistors so that the amplification factor is 1, A first control circuit generates a cutoff signal based on superimposition video information such as characters and figures, and transmits a cutoff signal that cuts off a portion of the television image signal corresponding to the superimposition video signal to the base of the transistor in the output stage of the amplifier circuit. At the same time, a signal representing the superimposition video information generated by the second control circuit is applied to the output terminal of the transistor of the output stage, so that the superimposition video information signal of the television image signal is applied to the output terminal of the transistor in the output stage. Since the corresponding portions are cut off and the television image signal and the video information signal for superimposition are simultaneously mixed using the amplifier circuit described above, noise generation is suppressed more than with conventional superimposing devices. The image is displayed more clearly on the video screen of the television receiver along with the television image signal.
Alternatively, it has the excellent advantage of being able to display video information such as the above-mentioned characters and figures by itself.

Alternatively, simply connecting the input terminal of the amplifier circuit to the output terminal of a demodulation circuit for a television image signal in an existing television receiver,
By simply connecting the output terminal of the amplifier circuit to the input terminal of the video device in the television receiver, it can be easily installed in the television receiver without changing the circuit configuration of the television receiver. There is also the advantage of being able to do so.

[Brief explanation of the drawing]

1 and 2 are diagrams showing the basic configuration of a typical conventional superimposing device, and FIG. 3 is a block diagram showing the overall configuration of a television system to which the superimposing device according to the present invention is applied. Figure 4 is
FIG. 3 is a block circuit diagram showing the basic configuration of the superimposing device, FIG. 5 is an electric circuit diagram showing an example of a specific circuit of the superimposing device shown in FIG. VEITCH that represents the function of a circuit
7a, b, and c are signal waveform diagrams for explaining the operation of the amplifier circuit in the circuit of FIG. 5, and FIG. 8 is a signal waveform diagram for explaining the operation of the amplifier circuit in the circuit of FIG. FIG. 9, which is a diagram for explaining the display mode of the image displayed on the video screen of the receiver, is an electric circuit diagram showing another specific example of the superimposing device according to the present invention. 10... Superimposition device according to the present invention, 11... Receiving device in a television receiver, 12...
CRT drive circuit, 13...color CRT,
15...Basic circuit of superimposition device according to this invention, 1
6...PNP transistor, 17...NPN transistor, 23...first logic gate IC, 25...
...Second logic gate IC, 30-R, 30-G,
30-B, 30-Y...Amplification circuit, 31...Control signal generation circuit, 32-R, 32-G, 32-B,
32-Y...Inverter, 33-R, 33-G,
33-B, 33-Y...output terminal, 34-R, 3
4-G, 34-Y...Nand Gate, 36-
BLK, 36-R, 36-G, 36-B... Input terminal of the control signal generation circuit, 50... Clamp circuit, R, G, B... Demodulated red, green, and blue components of the television signal. Representing color signal, Y...luminance signal, R-Y, G-Y, B-Y...color difference signal,
BLK...Blanking signal, R', G', B'...Color signal representing the red, green, and blue components of text characters or figures, A, B,..., F, G...One signal on the video screen. Area corresponding to pixels.

Claims (1)

[Scope of Claims] 1. An amplifier circuit configured to have an amplification factor of 1 using at least two transistors and inputting a demodulated television image signal to the base of the input stage transistor; A cutoff signal that is generated based on the video information signal for superimposition that is to be superimposed and that cuts off a portion of the television image signal that corresponds to the video information signal for superimposition is input to the base of the transistor in the output stage of the amplifier circuit. a first control circuit; and a second control circuit for applying a signal representing the video information for superimposition to an output terminal of a transistor in an output stage of the amplifier circuit, on the receiver's video screen,
A text/graphic signal superimposition device characterized in that superimposition video information is displayed together with television image information or alone.