JPS643431B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an adapter-type device for receiving character information transmitted by a television multiplexed teletext signal, and a method for displaying character information when the character information is displayed on a cathode ray tube of a monitor television. A device capable of lowering the brightness of the background screen in the area without causing any positional shift to provide an easy-to-see display, and which can minimize the number of connections between the teletext receiver and the monitor television. The purpose is to provide

The TV multiplexed teletext signal is received by an adapter-type receiver, converted into R, G, and B primary color signals for displaying text information, and sent to a monitor TV along with the video signal for the normal TV screen. By supplying this information, text information is displayed on a cathode ray tube in a superimposed manner on the television screen and a portion of the screen. In this case, in order to make the text information easier to see, the background television screen is darkened only in the portion where the text information is superimposed and displayed. However, in conventional devices of this type, the control signal for darkening the background of the text information display area is transmitted to the text broadcast receiving unit ( Since the power was supplied to the monitor TV from an adapter (adapter), the disadvantage was that it required a large number of cables and terminals to connect the two.

Therefore, the present invention solves such conventional drawbacks, and even when controlling to darken the background of a portion where text information is superimposed and displayed, it is possible to darken the background without causing positional shift, and, The object is to provide a device that allows the number of required connections to be reduced to a minimum. In order to achieve such an objective, in the present invention, a video signal for displaying a background screen on a monitor television and primary color signals of R, G, and B for displaying text information are supplied from a teletext receiving unit that is an adapter. In addition, the video signal for displaying the television screen in the background is processed in advance in the teletext receiving unit to lower the brightness of the video signal at the text information display position, and the R.G. This is characterized in that the B primary color signal is delayed by a predetermined amount of time compared to the video signal.

In this way, the video signal itself supplied to the monitor TV can darken the background, and the background can be darkened without positional shift. Moreover, the background control signal can be separately monitored. It is possible to eliminate the need for supplying power to the television and to minimize the number of connections between the two.

EMBODIMENT OF THE INVENTION Hereinafter, the present invention will be described in detail with reference to the drawings showing one embodiment thereof.

First, FIG. 1 shows the overall configuration of an embodiment of the present invention. In the figure, portions 1 to 11 indicate a color monitor television receiver equipped with a changeover switch and connection terminals. 1 is a tuner VIF and video detection circuit, which outputs a video signal and a 4.5MHz SIF signal. 2 is a buffer amplifier and connects 1VP- to terminal A3.
Outputs a P (75Ω system) video signal. 3 is a demodulator for audio multiplexed signals, the left signal is sent to terminal A1, and the left signal is sent to terminal A.
2, the right signal is output as each line out (level). 9 is the internal part of the audio signal input.
External selector switch, 10 is the internal/video signal input
It is an external changeover switch. 4 is an integrated amplifier for audio, and 5 is an input buffer amplifier for video signals. 6 is an NTSC signal decoder that processes the video signal and outputs R, G, and B baseband primary color signals. 7 is a deflection system circuit including a synchronous separation circuit, a horizontal AFC/oscillation circuit, a vertical oscillation/output circuit, a horizontal output circuit, a high voltage generation circuit, etc. 8 is R.G.
The output amplifier for each primary color signal of B outputs a signal to drive the cathode of the cathode ray tube. Reference numeral 11 indicates R, G, and B primary color signal outputs for displaying text information from the teletext receiving unit (portions 12 to 17 in FIG. 1) as an adapter, and R, G, and B primary color signal outputs from the decoder 6. This is a high frequency analog switch for mixing or switching with the primary color signal output. Of these 1 to 11, the parts other than the switch 11 have the same functions as a combination of a so-called television signal tuner and a video input type monitor television.

Next, the teletext receiving section of the adapter will be described in detail. 12 is a tuner/VIF/video detection circuit similar to 1, and 13 is an audio multiplexing demodulator similar to 2. Reference numeral 14 is a synchronization separation/color subcarrier regeneration circuit, and the functions of these 12 to 14 are similar to those in a normal television with built-in audio multiplexing. 15 is a processing circuit for the received teletext signal, which extracts, for example, the teletext signal superimposed on the 20th H during the vertical blanking period (VBL), and stores only the signal representing the necessary text information in a pattern memory for one screen. and color code memory, read out in accordance with the horizontal and vertical scanning of the cathode ray tube, and output R, G, and B primary color signals and switching control signals for character information display to terminal B.
It is transmitted to terminals A9 to A12 via terminals A9 to B12.
When character information is displayed, it is amplified by the output amplifier 8 via the changeover switch 11, and is displayed on the cathode ray tube as shown in FIG.
Character/graphic information as shown in B is displayed. A is a case where text information is superimposed and displayed on a part of a normal television screen on a negative line tube screen, and B is a case where only text information is displayed on the entire screen. 16 is an encoder that converts the R, G, and B primary color signal outputs of the teletext signal processing circuit 15 into NTSC video signals; 17 is an RF signal output from the encoder 16;
This is an RF converter that modulates a carrier wave and converts it into an RF signal.

Now, in the apparatus shown in FIG. 1, when receiving teletext, the teletext signal processing circuit 15 is operated by operating the teletext operation button (or switch), etc.
The control output from the terminal is transmitted to the terminals B5 and B8, and the switches 9 and 10 are respectively switched to the connection state between b and c. The switch 11 has a terminal B12 as described below.
By changing the control output at high speed and switching between the connection state between a and b and the connection state between b and c at high speed, a superimposed display as shown in FIG. 2A may be produced.

Now, in the receiving device as shown in Fig. 1, the second
As shown in Figure A, when text information is superimposed on a part of the television screen of a regular TV program, the video signal of the television screen in the background of the part where the text information is displayed (the part surrounded by the broken line) The text information becomes easier to read if the luminance level of the text is lowered so that the luminance of white text, etc. in the background screen is lower than that of the superimposed text information.

On the other hand, when the monitor TV and the teletext receiver are connected only through the connection terminal as shown in Fig. 1, the brightness level of the video signal transmitted from terminal B4 to the switch 11 via the video buffer amplifier 5 and decoder 6 is In order to partially lower the voltage, conventionally, in addition to the terminals A9 to A12, another terminal and a connection line are provided, and a control signal is applied from the teletext receiver to the monitor TV, whereby the decoder 6
It was necessary to reduce the DC level of the primary color signal (or video signal) for displaying the output background screen.

According to the present invention, it is possible to control the background screen of the character information display portion and reduce the brightness without adding such terminals or cables.

In order to superimpose and display text information received by teletext on the normal television screen that serves as the background, the switch 11 is normally short-circuited between a and b, and the R, G, and It is sufficient to switch to the b-c short-circuit state only during the period when the B primary color signal exists. This switching is carried out by sending a message to the terminal A12 during the period when there is text information, that is, during the period when the output of the luminance memory (pattern memory) in the teletext signal processing circuit 15 is "1" (see the output of R, G, and B primary color signals). and the period in which the OR output of the three primary color signals R, G, and B is "1"), switch 11 is set to b.
-c It is sufficient to supply a control signal that causes the short-circuit state. The switch 11 can be easily realized using an analog switch circuit formed into an IC, an analog gate made of a transistor, a diode, etc.

Next, a description will be given of means for lowering the brightness level of the video signal for background screen display at the character information display position. First, in the current general color television receiver circuit, a signal is applied to terminal A4, and then switch 11 is applied.
There will be a delay of approximately 0.5μsec until the value is reached. Therefore, the teletext reception signal processing circuit 15 shown in FIG.
Among the outputs, the video signal for displaying the background screen is used as is, and the brightness level of the video signal for the text information display portion is lowered, and the primary color signals of R, G, and B for displaying the text information are Approximately 0.5μs
By delaying, it is necessary to advance the portion of the video signal whose brightness level is to be lowered substantially by the delay time. That is,
Currently, in the teletext system being considered in Japan, the reduction in brightness is specified by a specific combination of 4 bits of the color designation code.
As shown in the figure, a color is designated for each dot of each character in the character information. Therefore, since the same designation is made for the brightness reduction area, any deviation from the primary color signal for character information display is not allowed. Therefore, as shown in FIG. 4, a 3-bit x 4 shift register 21 transfers the R, G, and B primary color signals and switching signals for 3 bits of a 175 nsec clock, that is, approximately
It is recommended to delay by 0.5μsec. Note that this signal delay means may have any circuit configuration.

23 is a circuit that controls the DC level of the video signal for background display to control the brightness level of the background screen, and the background level control signal Z of the output of the processing circuit 20 is of horizontal 8-bit width in FIG. signal (or a signal whose width is an integral multiple of the width). This FIG. 4 shows a part of the teletext signal reception processing circuit 15.
22 is a pedestal clamp circuit that pedestally clamps the video signal output from the tuner/VIF/video detection circuit 12. Pedestal clamp circuit 2
2 is applied to the level control circuit 23, and the brightness level of the video signal is reduced only during the period when the level control signal Z is at a low level. The processing circuit 20 uses a luminance signal representing a character from a luminance signal memory 18, which is a character information memory, and a 4-bit output from a color code memory 19, which specifies the coloring of each character. - Forms a switch control signal of G and B primary color signals and their logical sum. Then, it supplies them to the delay shift register 21, and also forms a level control signal Z for lowering the background brightness level. For example, R.G.
Both of the B primary color signals are “0”, that is, “black”,
Further, a control signal Z is generated at the level when the display mode is the superimposed display mode.

The level control circuit 23 is constructed, for example, as shown in FIG. 5, where 24 is an emitter follower transistor, 25 is an emitter resistor, 26 is a brightness reducing diode, 27 is an output buffer transistor, 28 is an emitter resistor, and 29 is an emitter resistor. 30 is a base leak resistance of a switching transistor, and 31 is a switching diode. When the level control signal is output to the output of the processing circuit 20, the diode 31 becomes conductive and the transistor 29
The base of transistor 29 becomes conductive. Therefore, the emitter of the transistor 24 is pulled to the ground side through the diode 26, and the DC level of the video signal shown in the waveform of FIG. Depending on how the current flowing through the transistor 29 is selected, as shown in B',
It is also possible to clip the white side.

As described above, according to the present invention, when displaying text information by superimposing it on a part of the television screen, it is possible to make it easier to see by reducing the brightness of the background image only in the part where the text information is superimposed. From the teletext receiving adapter to the monitor TV, the video signal for background display and the R signal for displaying text information are sent.
When supplying G and B primary color signals, the adapter processes the video signal in advance to lower the level of the background screen in the text information display area, thereby reducing the number of terminals for connection between the two. This allows the number of cables to be minimized. Among the signals supplied from the adapter to the color monitor television receiver, the R, G, and B primary color signals for character display are delayed than the video signals, so the processing of the video signal within the color monitor television receiver is delayed. Even if a delay occurs due to this, it is possible to prevent a time lag between the two signals in the display on the cathode ray tube, and a clear display without color shift or outline shift can be achieved. This is a particular problem when some of the circuits in the color monitor television receiver, such as the video amplifier, are also used to display characters from the adapter. becomes possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a teletext receiver according to an embodiment of the present invention, FIGS. 2A, B, and 3 are front views showing its display mode, and FIGS. 4 and 5 are partial views thereof. The block diagram and FIG. 6 are waveform diagrams illustrating its operation. 1...Tuner/VIF/video detection circuit, 2...
Buffer amplifier, 5...Video buffer amplifier, 6
... Decoder, 7 ... Deflection system circuit, 8 ... Output amplifier, 9, 10, 11 ... Switch, 12 ... Tuner/VIF/video detection circuit, 14 ... Synchronization separation, color subcarrier regeneration circuit, 15 ... Teletext signal processing circuit, 18 ... Brightness memory, 19 ... Color code memory, 20 ... Processing circuit, 21 ... Delay circuit,
22...DC clamp circuit, 23...Level control circuit.

Claims (1)

[Claims] 1. A tuner/VIF/video detection circuit that receives a television signal and obtains a video signal, an amplifier that amplifies the video signal, and processes the output video signal of the amplifier to generate R, G, and B signals. A color monitor television receiver equipped with a decoder that outputs primary color signals of R and GB, an output amplifier that amplifies the primary color signals of R and GB and supplies them to a cathode ray tube, and a television signal in which teletext signals are multiplexed. The tuner/VIF/video detection circuit that receives the signal and processes the received television signal,
Video signals for displaying the television screen of regular television programs, R, G, and B primary color signals for displaying text information superimposed on the television signal, and control output for switching video signals. and a character signal processing section for outputting a control output for switching primary color signals and supplying the output to the color monitor television receiver, and an adapter for receiving teletext broadcasts provided separately from the color monitor television receiver. The control output for switching the video signal controls the video signal input changeover switch in the color monitor television receiver, and the control output for switching the video signal from the tuner, VIF, and video detection circuit in the color monitor television receiver is controlled. The video signal and the video signal from the adapter are switched and inputted to the amplifier, and the control output for switching the video signal causes the video signal input switch in the color monitor television receiver to switch between the video signal from the adapter and the video signal from the adapter. When the signal side is switched to the signal side, the primary color signal switching switch in the color monitor television receiver is controlled by the control output for switching the primary color signal, and the R signal from the decoder in the color monitor television receiver is controlled.
It is configured to switch between the G and B primary color signals and the R, G and B primary color signals for displaying character information from the adapter and input them to the output amplifier, and the character signal processing section of the adapter. In order to reduce the brightness of only the part of the television screen corresponding to the display position of the character information where the R, G, and B primary color signals for displaying the character information are present, the television screen is A control circuit that lowers the signal level of the relevant part of the video signal for display in advance, and a control circuit that lowers the signal level of the relevant portion of the video signal for display, and a control circuit for the R, G, and B primary color signals for displaying the above-mentioned character information than the video signal for displaying this television screen. 2. A teletext receiving device, comprising: a delay circuit that delays the video signal by a time equal to the delay time of the video signal within the color monitor television receiver.