JPH0428194B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention is provided in a television receiver equipped with a CRT having a main screen display part and a sub-screen display part for displaying images on a main screen and a sub-screen. The present invention particularly relates to a device for erasing a child screen displayed in a child screen display area.

(Prior Art) Such a television receiver has a main screen display portion 10 on its CRT 10 as shown in FIG.
a and a child screen display part 10b, and each display part 10a, 10b has a main screen (Mt. Fuji in the example).
There is a device that can display a sub screen (a flower in the example) separately. If the images are displayed on each screen as shown in FIG. 5 according to the image signals for the main screen and the child screen, there is no problem in image display.

By the way, if there is no video signal for displaying an image on the sub-screen, the main screen of Mt. Fuji is displayed on the main screen display portion 10a as shown in FIG. The image is not displayed on the sub-screen and the image appears to flow, resulting in an unstable image display, which is undesirable. The reason for such a video display is, for example, that the video signal for displaying the video on the small screen display section 10b is from a VTR connected to this television receiver, and the videotape of that VTR has ended. This is the case when the video signal from the VTR is no longer supplied to the television receiver.

(Object of the Invention) An object of the present invention is to eliminate unstable video display in the sub-screen display portion.

(Structure of the Invention) In order to achieve such an object, the present invention provides a CRT having a main screen display part and a sub-screen display part for displaying images of the main screen and the sub-screen, and a video source switching signal. In response, a video source switching switch switches and outputs the first and second video signals individually, and processes each video signal individually output from the video source switching switch and converts these into main screen video signals. A main screen video signal processing circuit and a sub screen video signal processing circuit each output as a video signal for a sub screen, and a video signal for the main screen and a sub screen from both of the video signal processing circuits are synthesized.
a synthesis circuit that outputs to the CRT; a signal detection circuit that detects the presence or absence of one of the video signals supplied to the sub-screen video signal processing circuit via the video source changeover switch and outputs the detection signal; and a control instruction signal. a control section that outputs the video source switching signal in response to the detection signal and outputs a sub-screen switching signal in response to the detection signal; and a sub-screen changeover switch that cuts off the connection with the synthesis circuit, and in this configuration, when the signal detection circuit does not detect a video signal related to the sub-screen, the control section sends the sub-screen video signal outputting a sub-screen switching signal that cuts off the processing circuit and the synthesis circuit, and activating a sub-screen switching switch using the sub-screen switching signal to perform the blocking;
The sub-screen image is not displayed in the sub-screen display area.

(Example) Hereinafter, the present invention will be described in detail based on an example shown in the drawings. FIG. 1 is a circuit block diagram of a small screen erasing device in a television receiver according to an embodiment of the present invention. By operating the operating section 4, a control instruction signal is given to the control section 5 from the operating section 4. The control unit 5 outputs a video source switching signal in response to a given control instruction signal.
The operation unit 4 also outputs a channel selection signal corresponding to the operation. The tuner 2 selects and outputs the signal of that channel from among the VHF and UHF signals obtained from the antenna 1 in response to the channel selection signal. The intermediate frequency processing circuit 3 processes the channel signal and outputs it as a video signal.

Reference numeral 6 denotes a video source switching switch which is operated in response to a video source switching signal from the control section 5, and is adapted to switch each video signal and output it individually according to this video source switching signal. This video source switching switch 6 consists of two switch sections 61 and 62, one switch section 61 has a first common contact a, two individual contacts b,
The other switch section 62 also includes a second common contact d and two individual contacts e and f. A video signal from a VTR connected to the television receiver of this embodiment is applied to the first common contact a as an external video signal input. The video signal of this television receiver is applied from the medium frequency processing circuit 3 to the second common contact d.

Reference numerals 7 and 8 denote a main screen video signal processing circuit and a sub-screen video signal processing circuit that process each video signal individually output from the video source switching switch 6 and output these as a main screen video signal and a sub-screen video signal, respectively. A signal processing circuit 9 is a synthesis circuit that synthesizes RGB video signals for the main screen and the child screen from both video signal processing circuits 7 and 8 and outputs the RGB signal to the color CRT 10. This color CRT10 is shown in Figures 5 and 6.
As shown in the figure, it has a main screen display section 10a and a sub-screen display section 10b for displaying images of a main screen and a sub-screen. Reference numeral 12 denotes a signal detection circuit that detects the presence or absence of one of the video signals supplied to the small screen video signal processing circuit 8 via the video source changeover switch 6, and outputs the detection signal. The control section 5 outputs a video source switching signal to the video source switching switch 6 as described above in response to a control instruction signal from the operation section 4, and also responds to a detection signal from the signal detection circuit 12. and outputs a sub-screen switching signal. 11 is
This is a small screen switching switch that cuts off the connection between the small screen video signal processing circuit 8 and the combining circuit 9 in response to a small screen switching signal from the control section 5.

FIG. 2 is a concrete circuit block diagram of the signal detection circuit 12. A signal detection method in the signal detection circuit 12 is proposed, for example, in Japanese Patent Publication No. 16790/1983. The method described in this publication calculates the number of synchronization signals of a television signal,
It is determined whether or not the synchronization signal is a regular television signal based on whether or not a predetermined number of synchronization signals are present during a certain period of time. Signal detection circuit 1 in Figure 2
2 has a function of determining whether or not the synchronization signal in the video signal given to the small screen video signal processing circuit 8 is a regular synchronization signal using such technology. In FIG. 2, 13 detects the presence or absence of a video signal from a VTR or television receiver given from the individual contact c of the video source selector switch 6 using a synchronization signal, and outputs an ON signal when there is a video signal. , a detection unit that outputs an OFF signal when there is no video signal; 14 determines whether an OFF signal or an ON signal is input from the detection unit 13, and a count-up output is given from a counter 15, which will be described next. Judgment unit 15 is a judgment unit that issues an output command when
A counter that performs a counting operation for a predetermined period of time after the OFF signal is given, and outputs a count-up output to the judgment unit 14 when the count value N reaches N=M after counting from N=0; 16 is a judgment unit; This is a detection signal output section that outputs a detection signal in response to an output command from 14.

Next, the operation will be explained according to the flowchart of the signal detection circuit 12 shown in FIG. The process starts when the power of the apparatus of this embodiment is turned on, and at step n1 initial settings are made and the counter 15 is reset. In step n2, it is determined whether the detection signal from the detection section 13 is an ON signal. When the sub-screen video signal is supplied to the sub-screen video signal processing circuit 8, the detection signal of the detection unit 13 is an ON signal, so the judgment unit 14 determines that it is YES, and the step is executed.
Proceed to n3. At step n3, the counter 15 is reset. Step n1 again from step n8
Return to Next, the sub-screen video signal is transmitted to the signal detection circuit 1.
When the power is no longer supplied to the second detection unit 13, the step
At n2, it is judged as NO, and the count value N of the counter 15 is increased by +1. At step n5, it is determined whether the count value N is N=M.
If NO is determined, the process returns to step n1 in the same manner as described above.

Then, the count value N of the counter 15 is N=M
If so, it is determined as YES in step n5, and a detection signal is output from the detection signal output section 16 in step n6. That is, as can be seen from the explanation of this flowchart, when the count value of the counter 15 reaches N=M after the sub-screen video signal processing circuit 8 is no longer supplied with the sub-screen video signal, in other words, when the count value of the counter 15 reaches N=M, the predetermined value is A detection signal is provided from the signal detection circuit 12 to the control unit 5 with a delay time.
The control unit 5 switches and operates the small screen changeover switch 11 based on this detection signal. As a result, in the synthesis circuit 9, the sub-screen video signal processing circuit 8
No sub-screen video signal is provided from the sub-screen video signal, and only the main-screen video signal from the main-screen video signal processing circuit 7 is provided. In this way, on the color CRT 10, as shown in FIG. 5, an image of Mt. Fuji is initially displayed on the main screen display section 10a, and an image of flowers is displayed on the sub-screen display section 10b. And VTR
When the video signal is no longer applied to the first common contact a of the video source changeover switch 6 due to the end of the video tape, etc., the sub-screen display section 10b is displayed as shown in FIG. The flower image is not displayed, but after a predetermined period of time, the sub-screen changeover switch 11 is shut off by the sub-screen switching signal from the control unit 5, and after this cut-off, the image of the flower is not displayed. Sub screen display part 10
In b, the flower image that is the child screen is deleted, and only the main screen is displayed.

(Effects of the Invention) As described above, according to the present invention, since the sub-screen switching switch is provided which cuts off the connection between the sub-screen video signal processing circuit and the synthesis circuit in response to the sub-screen switching signal, When the sub-screen video signal is lost, the sub-screen can be deleted from the sub-screen display area of the CRT, and unstable images will no longer be displayed without the sub-screen being displayed in the sub-screen display area.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram of a small screen erasing device for a television receiver according to an embodiment of the present invention, FIG. 2 is a specific circuit block diagram of a signal detection circuit of the device shown in FIG. 1, and FIG. 3 is an embodiment. Flowchart for explaining the operation of the device, Figure 4 is shown in color according to the example device.
Figure 5 is a front view of the CRT when the sub-screen is deleted from the sub-screen display area of the CRT, and a front view of the CRT when the main screen and sub-screen are respectively displayed on the main screen display area and the sub-screen display area of the CRT. Front view of CRT, No. 6
The figure is a front view of the CRT shown in FIG. 5 in a state where an unstable image is displayed on the sub-screen display portion of the CRT. In each figure, numeral 5 is a control unit, 6 is a video source selection switch, 7 is a main screen video signal processing circuit, 8 is a subscreen video signal processing circuit, 9 is a synthesis circuit, 10 is a color CRT, and 11 is a subscreen switch switch, 12 is a signal detection circuit.

Claims (1)

[Claims] 1. A CRT having a main screen display part and a sub-screen display part for displaying images of the main screen and sub-screens.
a video source switching switch that switches and outputs the first and second video signals individually in response to a video source switching signal; and a video source switching switch that processes each video signal that is individually output from the video source switching switch and outputs the first and second video signals individually. a main screen video signal processing circuit and a sub screen video signal processing circuit that respectively output the video signal for the main screen and the video signal for the sub screen, and the video signals for the main screen and the sub screen from both the video signal processing circuits. and a signal detection circuit that detects the presence or absence of one of the video signals supplied to the small screen video signal processing circuit via the video source selection switch and outputs the detection signal. a control unit that outputs the video source switching signal in response to a control instruction signal and outputs a sub-screen switching signal in response to the detection signal; and a control unit that outputs the sub-screen switching signal in response to the sub-screen switching signal; 1. A small screen erasing device for a television receiver, comprising a small screen changeover switch for cutting off connection between a signal processing circuit and the combining circuit.