JP2561838Y2 - In-vehicle television receiver - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-vehicle television receiver used in an environment where the received electric field strength fluctuates.
More specifically, the present invention relates to an in-vehicle television receiver capable of displaying a reception channel and the like on a relatively small screen by so-called superimposition.

[0002]

2. Description of the Related Art In recent years, a television receiver has been provided with an image insertion function called a superimpose for displaying the number of selected channels for about two seconds after a channel selection operation, for example. In particular, in the case of an in-vehicle television receiver, the received electric field strength is liable to fluctuate, so that there are many opportunities for tuning operation, which is an extremely effective function. However, since the on-vehicle television receiver is relatively small, it is difficult to recognize characters such as inserted characters and figures. Synchronization with the television image is lost, making recognition more difficult.

For this reason, in the typical prior art, measures have been taken to improve the stability of an image under a weak electric field. That is, for example, the response of the AGC circuit is improved, and the reception by the diversity system for selecting the antenna having the best reception state among the plurality of antennas is performed.

[0004]

[Problems to be Solved by the Invention] Even in the above-mentioned prior art,
At the time of instantaneous decrease in electric field strength such as when passing through a building shadow or when switching antennas, the synchronization signal is disturbed,
It is difficult to stabilize the inserted image.

An object of the present invention is to provide a vehicle-mounted television receiver that can stabilize an inserted image.

[0006]

The present invention detects a television signal received by an antenna, separates the television signal into a television video signal and a reception synchronization signal, and supplies the detection circuit to a display means. A character video signal generating means for generating a video signal of a character such as a character or a figure to be inserted into the display means and providing the video signal to the display means; an external synchronizing signal generating means for generating an external synchronizing signal; Control means for outputting a switching control signal when the intensity is less than a predetermined discrimination level,
In response to the switching control signal, the reception synchronization signal is interposed between the detection circuit and the display means when the switching control signal is not applied, and when the switching control signal is applied, the external synchronization Switching means for selectively providing a signal to a display means.

[0007]

According to the present invention, a television signal received by an antenna is converted into a television video signal of an R, G, B color signal or a composite video signal and a vertical and horizontal reception synchronization signal by a detection circuit. Separated. The television image signal separated by the detection circuit is provided to a display means, and the reception synchronization signal is provided to one input of a switching means. A video signal of a character image such as a character or a figure to be inserted into the television image created by the character image signal creating means is also input to the display means.

The other input of the switching means is supplied with an external synchronization signal created by the external synchronization signal generating means. The switching means selectively responds to a switching control signal from the control means to selectively receive a reception synchronization signal separated from the received television signal and an external synchronization signal generated by the external synchronization signal generation means. Give to display means. That is, the control means provides an external synchronization signal to the display means via the switching means when the received electric field strength is low in accordance with the received electric field strength.

Therefore, even if the reception synchronization signal is disturbed due to a decrease in the electric field strength or the like, the character image can be stably displayed by the external synchronization signal.

[0010]

FIG. 1 is a block diagram showing an electric configuration of a television receiver 1 according to an embodiment of the present invention. This television receiver 1 is used for a vehicle, and is therefore used in an environment where the received electric field strength changes frequently. The received signal of the television broadcast received by the antenna 2 is
It includes a tuning / detection circuit, is input to a tuner unit 3 as control means, and outputs color signals of R1, G1, B1 and a synchronization signal SY.
NC1. The respective color signals R1, G1, B1
Are input to the input terminals P1R, P1G, P1B of the image synthesizing unit 4 via the lines L1R, L1G, L1B, respectively. The synchronization signal SYNC1 is given to one of the individual contacts 5a of the changeover switch 5 via the line L1a. The other individual contact 5b of the changeover switch 5
Includes an external synchronization signal SYN from the external synchronization signal generation unit 6.
C2 has been input. Common contact 5c of changeover switch 5
Is the input terminal P1 of the image synthesizing unit 4 via the line L1b.
Input to S.

The tuner section 3 also outputs a line L1
c, a switching control signal is given to the changeover switch 5, and the switching control signal is used as a discrimination level based on the maximum sensitivity of the tuner unit 3 or around 20 dBμV, that is, a mute level of whether or not to display a television image. ,
When the input signal level from the antenna 2 is equal to or higher than the discrimination level, the switching switch 5 is controlled to conduct to the individual contact 5a side, and when the input signal level is lower than the discrimination level, to the individual contact 5b side.

From the output terminal P2S of the image synthesizing unit 4, a character video signal generating unit 7 is connected via a line L2S.
To the synchronization signal SYNC selected by the changeover switch 5.
1 or an external synchronization signal SYNC2 is derived. The character video signal creation unit 7 is configured to output the signals SYNC1, SYNC
In response to C2, the color signals R2 and G of the image of the character such as a character such as a channel number and a volume setting value or a graphic.
2, B2, and input terminals P2R, P2 of the image synthesizing unit 4 via lines L2R, L2G, L2B, respectively.
G, P2B.

The image synthesizing section 4 creates color signals R3, G3, B3 of a video in which a character image is inserted into a television video, and supplies the color signals R3, P3G, P3B to the drive circuit 8 from output terminals P3R, P3G, P3B, respectively. The signals SYNC1 and SYNC2 input to the input terminal P1S are input to the drive circuit 8 from the output terminal P3S of the image synthesis unit 4. In response to the signals SYNC1 and SYNC2, the drive circuit 8 drives a display device 9 such as a liquid crystal display device or a cathode ray tube based on the color signals R3, G3 and B3. Therefore, the electric field strength decreases and the synchronization signal SYNC
Even if 1 becomes unstable, a character image can be stably displayed using the external synchronization signal SYNC2.

The tuner section 3 realizes a horizontal synchronizing signal every one horizontal scanning cycle, that is, every 63.4 μsec, and a vertical synchronizing signal every 1/30 sec from a received signal by, for example, a low-pass filter and a high-pass filter. And separated to the line L1a. When the received electric field intensity becomes lower than the mute level, the tuner unit 3 outputs the color signals R1, G
1, B1 may be equal to or less than the so-called pedestal level (normally, black level), and the display screen of the display device 9 may be black. In this case, the display image is black and stable even without the synchronization signal SYNC1.

However, when displaying a screen other than a black screen, for example, a white screen, a synchronization signal is required. Further, even for the black screen, a synchronization signal for an inserted image is required. Therefore, based on whether the antenna input level is equal to or higher than the mute level, the changeover switch 5
Is switched, and the synchronization signal SYNC1 and the external synchronization signal SYNC are switched.
2 can be combined with the clearly displayed television image when the synchronization signal SYNC1 is used, and the unclear television image can be synthesized when the external synchronization signal SYNC2 is used. Or the mute image, the inserted image can be displayed stably.

[0016]

As described above, according to the present invention, an external synchronization signal is used when the reception electric field strength is lowered and the reception synchronization signal of the received television signal is disturbed. Character images such as power letters and figures can be stably displayed.

In particular, according to the present invention, for example, when receiving a television signal of the same channel, if the received electric field strength of the television signal decreases while the automobile is running, the detection circuit is used to stabilize the inserted image. Is switched to an external synchronizing signal in place of the receiving synchronizing signal, whereby a character image can be stably produced in synchronization with the external synchronizing signal even when reception is disturbed by a television video signal obtained by a detection circuit. Excellent effects are achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electrical configuration of a television receiver 1 according to an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 television receiver 3 tuner section 4 image synthesizing section 5 changeover switch 6 external synchronization signal generating section 7 character video signal generating section 8 drive circuit 9 display device

Claims (1)

(57) [Scope of request for utility model registration] 1. A television signal received by an antenna is detected and separated into a television video signal and a reception synchronization signal. Character video signal generating means for generating a video signal of the character and providing the video signal to the display means; external synchronizing signal generating means for generating an external synchronizing signal; and receiving electric field intensity of a television signal by an antenna being less than a predetermined discrimination level. Control means for outputting a switching control signal at one time, interposed between the detection circuit and display means, in response to the switching control signal, when the switching control signal is not given, the reception synchronization signal, And switching means for selectively supplying the external synchronization signal to display means when a switching control signal is supplied. Television receiver.