JPS6210980A - Mobile television - Google Patents

Abstract

PURPOSE:To evade the displaying of a turbulent image by displaying the picture information at a preceding field as a still picture when a receiving level is lowered than a prescribed value. CONSTITUTION:When the receiving level is lowered and AGC voltage VAGC becomes smaller than the prescribed value, a read out signal SR instead of a write signal SW is supplied from a control circuit 11 to a field memory 10, and a mode becomes a reading mode. And a video signal that is the one before the AGC voltage VAGC is lowered than the prescribed value is read out repeatedly from the field memory 10. At such a time, a change-over switch 5 is connected to a B side. Thereby, a video signal SV1 read out from the field memory 10 is supplied to an image receiving tube 15 through a D/A converter 12, the change-over switch 5, a signal processing circuit 13 and an amplifier 14, and the still picture having no turbulence with the video signal SV1 is displayed.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

8 Industrial field of application B Summary of the invention C Prior art D Problem to be solved by the invention E Means for solving the problem F Effect G Example G1 First example (Figure 1) G2 No. Embodiment 2 (Fig. 2) G3 3rd Embodiment (3131) G4 4th Embodiment (Fig. 4) H Effect of the Invention A Industrial Field of Application The present invention is applicable to mobile objects such as automobiles. Regarding the in-vehicle TV installed.

B. Summary of the Invention The present invention is an in-vehicle television in which, when the reception level drops below a predetermined value, image information of the previous field is displayed as a still image, thereby preventing a distorted image from being displayed.

C. PRIOR ART In-vehicle televisions that receive signals using a single antenna, such as a Rondo antenna, are extremely difficult to view because the image becomes distorted when the direction in which the broadcast waves arrive changes.

Therefore, as a reception method for in-vehicle television, the patent application No. 59-2
As shown in No. 1339, an antenna has been proposed in which a plurality of antennas having directivity in multiple directions are mounted and the one with the strongest electric field is selected. According to this, since the antenna with the strongest electric field strength is always selected, it is possible to perform good reception even if the direction in which the broadcast waves arrive changes.

D Problems to be Solved by the Invention However, even if such a reception method is adopted, when driving in a place where the electric field strength is extremely weak, such as inside a tunnel or a valley, you may see a distorted image. become,
This is extremely unpleasant for viewers.

In view of this point, the present invention is designed to prevent the display of distorted images that cause discomfort to viewers.

E. Means for Solving the Problems In order to solve the above-mentioned problems, the present invention sequentially writes the received signals into the field memory Ol, and when the reception level during driving falls below a predetermined value (at this time, the distorted image is This is to disable writing to the field memory (1 (displayed)), field memory (1), and set this field memory 0I to read mode.Then, the image information of the previous field is displayed as a static IL image.

F Effect When the reception level falls below a predetermined value and the image becomes distorted, the field memory OI is set to read mode, and from this field memory, the reception signal of the previous field whose reception level is higher than the predetermined value is read. is read out, and one picture is displayed every second. In other words, even at this time,
A clear image is displayed.

G Example G1 First Example (FIG. 1) Hereinafter, a first example of the present invention will be described with reference to FIG. 1.

In the figure, (1a) to (ld) are arranged so as to compensate for radio waves in different directions, respectively.1. The television signals received by these antennas (1a) to (ld) are supplied to a tuner (3) via a switching circuit (2).

The tuner (3) includes a high frequency amplification circuit to an intermediate frequency amplification circuit, and the intermediate frequency signal extracted from the tuner (3) is supplied to a video detection circuit (4).

The video signal Sv taken out from the video detection circuit (4) is supplied to the fixed terminal on the A side of the changeover switch (5).

Further, the video signal extracted from the video detection circuit (4) is supplied to the AGC circuit (6). Then, this AGC circuit (6) generates an AGC voltage VAGC corresponding to the reception level.
is taken out, this is supplied to the tuner (3), and the AG
C is applied.

Further, the video signal Sv is supplied to an antenna switching control circuit (7). Further, the video signal Sv is supplied to a synchronization separation circuit (8), and the synchronization signal Ps taken out from this separation circuit (8) is supplied to a control circuit (7). A switching control signal S1 is supplied from the control circuit (7) to the switching circuit (2).

The switching circuit (2) receives the switching control signal S from the control circuit (7).
1, and the antennas (1a) to (1d) are sequentially switched within a predetermined horizontal period of the vertical blanking period. At this time, the control circuit (7) detects and compares the pedestal levels of the video signal Sv when switched to the antennas (1a) to (1d), respectively. The switching control signal S1 is used to select the antenna from which the maximum level can be obtained. As a result, the antenna (1a)
~(ld) sequentially) ij! ! The switching circuit (2) is kept in a state in which the antenna from which the maximum level is obtained is selected until the period when the maximum level is obtained. Note that switching of the antennas (1a) to (ld) is normally performed for each even field or odd field.

The antenna switching system described above is based on the patent application filed in
It is the same as No. 9-21339.

Further, in FIG. 1, the video signal Sv from the video detection circuit +41 is converted into a digital signal by the AID converter +91 and then supplied to the field memory as a write signal. Writing and reading of this field memory Ol is controlled by a control circuit (11). The control circuit (11) is supplied with the synchronization signal Ps from the synchronization separation circuit (8), and the synchronization signal Ps is supplied from the A(, C circuit (6)).
C voltage VAGC is supplied.

A G C voltage VA (when JC is larger than a predetermined value (at this time, the reception level is high and a good image without disturbance is displayed) is written to the field memory QO by the control circuit (11)). A signal Sw is supplied,
Field memory 00) is placed in write mode. On the other hand, when the AGC voltage VAGC is smaller than the predetermined value (at this time, the reception level is low and a distorted image is displayed), the control circuit (11) supplies the readout signal SR to the field memory. The field memory Ol is placed in a read mode, and the video signal for one field is repeatedly read out.

The signal SV1 read from field memory 0 is D
The signal is converted into an analog signal by the /A converter (12) and supplied to the fixed terminal on the B side of the changeover switch (5).

This changeover switch (5) is controlled by the control circuit (1).
1), and as described above, when the AGC voltage VAGC is larger than a predetermined value, it is switched to the A side, and when it is smaller, it is switched to the B side.

The video signal obtained from this changeover switch (5) is passed through a signal processing circuit (13) and an amplifier (14) to a picture tube (1).
5), and the image is displayed on this picture tube (15).

This example is configured as above, the reception level is high,
When the AGC voltage VAGC from the AGC circuit (6) is larger than a predetermined value, the changeover switch (5) is connected to the A side. Therefore, the video signal Sv taken out from the video detection circuit (4) is transferred to the changeover switch (5) and the signal processing circuit (1).
3) and an amplifier (14) to the picture tube (15), and a good image without any disturbance caused by this video signal Sv is displayed. At this time, a write signal Siv is supplied from the control circuit (11) to the field memory 0Φ, the field memory α is placed in a write mode, and the video signals Sv are sequentially written.

In this state, the reception level becomes low and the AGC voltage VAG
When C becomes smaller than a predetermined value, the control circuit (11) supplies the field memory (11) with a read signal SR instead of the write signal 3w0 to enter the read mode.
The video signal for one field before the GC voltage VAGC becomes smaller than a predetermined value is repeatedly read out. At this time,
Since the changeover switch (5) is connected to the B side, the video signal SV1 read from the field memory 01 is connected to the D/A
Converter (12), selector switch (5), signal processing circuit (
13) and an amplifier (14) to the picture tube (15), and a still image without any disturbance caused by the video signal Sv1 is displayed.

In this state, when the reception level becomes high and the AGC voltage VAGC becomes larger than the predetermined value, the selector switch (5
) is connected to the A side, and an image based on the video signal Sv is displayed on the picture tube (15), and at the same time, the field memory O1 is put into a write mode, and the video signal Sv is sequentially written.

According to this example, when the reception level becomes low and the image becomes disturbed, 112 still images of the video signal SV1 repeatedly read out from the field memory 01 are displayed, so that the disturbed image becomes It is not displayed and does not cause discomfort to the viewer.

G2 Second Embodiment (Fig. 2) Next, Figs. 2 to 4 show other embodiments of the present invention, and in these figures, parts corresponding to those in Fig. 1 are designated by the same reference numerals. , and detailed explanation thereof will be omitted.

First, the example shown in FIG. 2 will be explained.

In the same figure, the video signal Sν from the video detection circuit (4)
is supplied to the fixed terminal on the A side of the changeover switch (5).

Further, the video signal Sv is converted into a digital signal by an A/D converter (9) and then supplied as a write signal to the field memory OI via a field delay line (16). Writing and reading of this field memory OI is controlled by a control circuit (11). When the AGC voltage VAGC is larger than a predetermined value (at this time, the reception level is high and a good image without disturbance is displayed), the control circuit (11) outputs field memory 0.
The write signal Sw is supplied to the field memory 0), and the field memory 0@ is placed in the write mode. On the other hand, AGC voltage VA
When GC is smaller than a predetermined value (at this time, the reception level is low and a distorted image is displayed), a read signal SR is supplied from the control circuit (11) to the field memory IJ OI, and the field memory OI is set to read mode, and the video signal for one field is repeatedly read out. In this case, in the example in Figure 1 described in Section 2,
When the AGC voltage VAGC changes from larger to smaller than a predetermined value or from smaller to larger, the signals Sw and SR supplied to the field memory aψ are switched instantaneously, but in the example in FIG. The signals S- and SR are switched after the vertical blanking period.

Video signal SV2 read from field memory Ol
is supplied to the B-side fixed terminal of the changeover switch (5) via the D/A converter (12). This cutting su isochi (5
) is performed by the switching control signal S3 supplied from the control circuit (11), and when the write signal Sw is supplied to the field memory Ol as shown in FIG. When supplied, it is switched to the 13 side.

The video signal sent from this changeover switch (5) is passed through the signal processing circuit (I3) and amplifier (14) to the picture tube (
I5), and the image is displayed on this picture tube (15).

This example is configured as follows, and when the reception level is human and the AGC voltage VA+]C from the AGC circuit (6) is larger than a predetermined value, the changeover switch (5) is connected to the A side. . Therefore, the video signal Sv extracted from the video detection circuit (4) is sent to the picture tube (15) via the changeover switch (51, signal processing circuit (13) and amplifier (14)).
A good image without any disturbance caused by this video signal 14Sv is displayed. At this time, the control circuit (1
1) A write signal S- is supplied to the field memory 000, the field memory is set to write mode, and the video signal Sv' of one field before is sequentially written via the delay line (16).

In this state, the reception level becomes low and the AGC voltage VAG
When C becomes smaller than a predetermined value, the control circuit (11) supplies the read signal SR instead of the write signal S- to the field memory OI after waiting for the next vertical blanking period to set the field memory OI in a read mode. . Then, the video signal of the field before the field in which the AGC voltage VAGC becomes smaller than the predetermined value is repeatedly read out from the field meter F-IJ (Il). At this time, the changeover switch (5) is connected to the B side, so The video signal SV2 read from the field memory is D/A
Converter (12), selector switch (5), signal processing circuit (
13) and an amplifier (14) to the picture tube (15), and a still image without any disturbance caused by the video signal SV2 is displayed.

In this state, when the reception level becomes high and the AGC voltage VAGC becomes larger than a predetermined value, the changeover switch (5) is connected to the A side again after waiting for the next vertical blanking period, and the video signal is sent to the picture tube (15). At the same time that the image based on Sv is displayed, the field memory 01 is put into the write mode, and the video signal Sv' of 1 field I' is sequentially written.

This example also provides the same effects as the example shown in FIG. 1 above. Moreover, according to this example, since the switching between writing and reading in the field memory OI is performed during the vertical blanking period (between fields), there is an advantage that a still image can be constructed with only one field of video signal.

G3 third embodiment (Figure 3) Next, the example shown in FIG. 3 will be explained.

In the same figure, a video signal Sv' taken out from a delay line (16) is supplied to a fixed terminal on the A side of a changeover switch (5), and a fixed terminal on the B side of this changeover switch (5) is connected to a field memory. Video signal S read from 01
V2 is supplied. The video signal obtained from this changeover switch (5) is converted into an analog signal by a D/A converter (12), and then the signal processor I! 8 (13) and an amplifier (14) to a picture tube (15), and an image is displayed on this picture tube (15).

In addition, write/read control of field memory 00),
The switching control of the changeover switch (5) is performed by the control circuit (
11) in the same way as the example in FIG.

In this example, the reception level is high and the AGC circuit (6
) is larger than a predetermined value, the changeover switch (5) is connected to the A side.

Therefore, the video signal Sv' of one field before passed through the delay line (16) is transferred to the changeover switch (5), the D/A converter (
12), the signal is supplied to the picture tube (15) via a signal processing circuit (13) and an amplifier (14), and a good image without disturbance caused by this video signal Sv' is displayed.

At this time, a write signal Sw is supplied from the control circuit (11) to the field memory OI, and the field memo 11 is put into the write mode, and the video signal Sv' of one field before is written via the delay line (16). are performed sequentially.

In this state, the reception level becomes small and the AGC voltage V A
When l1C becomes smaller than a predetermined value, the control circuit (11) supplies the read signal SR instead of the write signal Sw to the field memory OI, waiting for the next vertical blanking period, to set it in the read mode. . Then, from the field memory Ol, the AGC voltage V
The video signal of the field before the field in which the AGC is smaller than a predetermined value is repeatedly read out. At this time, the changeover switch (5) is connected to the B side, so the video signal SV2 read from the field memory O1 is transferred to the changeover switch (5), the D/A converter (12), and the signal processing circuit (1).
3) and an amplifier (14) to the picture tube (15), and a static 11: image without disturbance caused by the video signal SV2 is displayed.

In this state, when the reception level becomes high and the AGC voltage VAGC becomes larger than a predetermined value, the changeover switch (5) is connected to the A side again after waiting for the next vertical blanking period, and the video signal is sent to the picture tube (15). At the same time that the image by Sv' is displayed, the field memo Om is set to the write mode, and the video signal Sv' is written.

This example also provides the same effects as the example shown in FIG.

Moreover, according to this example, when the AGC voltage V
There is an advantage that a distorted image will not be displayed even until the next vertical blanking period when the GC voltage VAGC becomes smaller than a predetermined value and a still image is displayed using the video signal SV2 from the field memory O1.

G4 fourth embodiment (Figure 4) Next, the example shown in FIG. 4 will be explained.

In the figure, the video signal Sv from the video detection circuit (4)
is converted into a digital signal by the A/D converter (9), and then
Provided as a write signal to field memories (IOA) and (IOB). These field memories (
10^) and (10B) are controlled by a control circuit (11).

The write signal Sw from the control circuit (11) is supplied to the field memories (IOA) and (Inn) via fixed terminals on the A side and B side of the changeover switch (17), respectively. Further, the read signal SR from the control circuit (11) is supplied to the field memory (IOB) and (10^) through fixed terminals on the A side and B side of the changeover switch (18), respectively. In addition, the control circuit (
11), switching control signals S4 and S6 are supplied to the changeover switches (17) and (18), respectively. Changeover switch (
When the switch (17) is switched to the A side and B side, the changeover switch (18) is also switched to the A side and B side, respectively. AGC
When the voltage V All C is larger than a predetermined value (at this time, the reception level is high and a good image without disturbance is displayed), the changeover switches (17) and (18)
is alternately switched to the A side and the B side every l vertical periods.

Therefore, the field memory (IOA) is put into a write mode and a read mode every vertical period, and the field memory (10B) is put into a mode opposite to the field memory (IOA) every one vertical period.

On the other hand, when the AGC voltage VAGC is smaller than the predetermined value (at this time, the reception level is low and a distorted image is displayed), the changeover switches (17) and (18) are set to A.
One of the field memories (IOA) and (IOB>) is fixed to the write mode, and the other is fixed to the read mode, and from the read mode side, the image of one field is read. The signal is read out repeatedly.

Further, the video signals SVA and SVB read from the field memories (10^) and (IOB) are supplied to fixed terminals on the A side and B side of the changeover switch (5), respectively. This changeover switch (5) is controlled by the control circuit (
11) The read signal SR is sent to the field memory (IOA) by the switching control signal S6 supplied from the
is supplied, the field memory (I
When the readout signal SR is supplied to OB), it is switched to the B side.

The video signal obtained from this changeover switch (5) is D/A
After being converted into an analog signal by a converter (12), it is sent to a picture tube (1) via a signal processing circuit (13) and an amplifier (14).
5), and the image is displayed on this picture tube (15).

This example is configured as follows. When the reception level is human and the AGC voltage VAoc from the AGC circuit (6) is greater than a predetermined value, the changeover switch (17) is activated.

(1 day), the pressure is switched to the A side and the B side every vertical period. And field memory (10^) and (
The signals SVa and SVB read out every vertical period from the IOB) are transferred to the changeover switch (5) and the D/A converter (1
2), the video signal SVA+S is supplied to the picture tube (15) via the signal processing circuit (13) and the amplifier (14).
An image without any disturbance caused by ■ is displayed.

At this time, field memory (IOA) and (101
1>, the video signal Sv is sequentially written to those not in the read mode.

In this state, the reception level becomes small and the AGC voltage V
When AGC becomes smaller than a predetermined value, the mode of the field memories (10^) and (IOB) is fixed to the mode at that time. Then, the video signal of the field before the field in which the AGC voltage VAGC is smaller than a predetermined value is repeatedly read out from the field memory in the read mode. □This video signal then passes through the changeover switch (5), D/A converter (12), and signal processing circuit (1).
3) and an amplifier (14) to the picture tube (15), and a still image without any disturbance is displayed.

With this lJeLM, the reception level becomes high and the AGC voltage Vi
When c becomes larger than a predetermined value, the changeover switches (17) and (1B) are switched again to the A side and the B side every vertical period.
It is in a state where it can be switched alternately to the side. Then, images are displayed based on video signals SvA and Sva that are alternately read out from the field memories (10^) and (10B) every vertical period.

It is clear that this example can also provide the same effects as the example shown in FIG.

In the above-described embodiment, the reception level is determined based on the AGC voltage VAdC, but the reception level may be determined based on, for example, the count number of the horizontal synchronization signal or the level of the horizontal synchronization signal.

H Effects of the invention According to the invention described above, when the reception level becomes low and the image becomes distorted, a still image based on the video signal of the previous field when the reception level was high is displayed. , a distorted image will not be displayed. Therefore, the viewer will not feel uncomfortable.

[Brief explanation of drawings]

Figure 1 is a configuration diagram showing one embodiment of the present invention, Figures 2 to 4
The figure is a configuration diagram showing another embodiment of the present invention. (3) is a tuner, (4) is a video detection circuit, (5) is a changeover switch, (6) is an AGC circuit, 01 is a field memory, and (11) is a control circuit. Hokkaido 62-10 Kita u (7)

Claims (1)

[Claims] Received signals are sequentially written into the field memory, and when the reception level during driving drops below a predetermined value, writing to the field memory is prohibited and the field memory is set to read mode, and the image information of the previous field is stored as a still image. An in-vehicle TV designed to display .