JPH0630348A - On-vehicle television receiver - Google Patents

Abstract

PURPOSE:To improve the apparent S/N and to prevent disturbance in a picture by adjusting stepwise a high frequency characteristic of a video amplifier circuit as a vehicle speed rises and selecting softer picture quality attended with the vehicle speed. CONSTITUTION:When a video reception circuit 2 is operated to receive a desired radio wave, an audio signal of a broadcast wave is fed to a speaker 4 and a video image is received by a monitor 6. Simultaneously a frequency counter of a control section 9 is reset and speed information of a vehicle supplied to an input terminal 7 is read and counted. The control section 9 discriminates the current vehicle speed based on the result of count of the frequency counter. An output pulse train is compared with data A stored in the control section 9 and the result is discriminated. Thus, a control signal is outputted to an output port A and a picture quality adjustment circuit 10 generates a signal controlled from the output port A. Thus, the frequency characteristic of a video amplifier circuit 5 is corrected so as to attenuate a high frequency by one stage and the apparent S/N is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television receiver mounted on a vehicle, and more specifically, it improves the S / N ratio of a video circuit which is deteriorated due to a reception failure while the vehicle is running, and displays an image with less disturbance. The present invention relates to a vehicle-mounted television device that can be displayed.

[0002]

2. Description of the Related Art Television receivers that receive VHF and UHF band television broadcast waves are often subject to various types of reception interference, and the quality of images and audio is significantly affected by some reception interference. May be damaged. It is well known that ghosting and loss of sharpness occur in images, especially when subjected to multi-path interference.

On the other hand, an on-vehicle television receiver is more likely to be damaged than a home-use television receiver. For example, when the vehicle is driving in a city area, the fluctuation of the input electric field strength and the influence of multipath may occur. The image is frequently disturbed, and the more the influence of the obstacle is, the more the image is distorted. In order to prevent such a reception obstacle, a vehicle-mounted television device is usually equipped with a diversity receiving device.

[0004]

Receiving obstacles that the in-vehicle television apparatus is affected are mainly multipaths and fluctuations in electric field strength while driving in urban areas, and the in-vehicle television receiver is affected by the above-mentioned receiving obstacles. The noise in the received signal increases, which significantly degrades the S / N of the video circuit and causes image distortion.

However, even a television set equipped with a diversity receiving device has a problem that the influence of the reception obstacle cannot be avoided as the traveling speed of the vehicle increases and the effect of the diversity antenna is hardly obtained.

The present invention has been made in view of the above circumstances.
The vehicle speed information is introduced into the receiving device, and the apparent S / V of the video circuit is obtained by the image quality adjustment signal obtained from this speed information.
It is an object of the present invention to provide a vehicle-mounted television device capable of improving N and preventing image distortion due to increase in traveling speed.

[0007]

In order to achieve the above-mentioned object, in a vehicle-mounted television device of the present invention, a means for introducing speed information of a vehicle into the device, and the speed information is counted and for each constant count value. Frequency counting means for sequentially sending signals to the control unit output port, image quality adjustment signal generating means for controlling the frequency characteristic of the video amplifier circuit based on the sent signal, and display means for displaying the video amplifier circuit output, It is characterized by having.

[0008]

In the television device while the vehicle is running, the S / N is deteriorated due to the fluctuation of the input electric field strength or the influence of multipath, and the image is disturbed due to the S / N. The apparent S / N can be improved and the disturbance of the image can be prevented by adjusting the high frequency characteristic of the video amplifier circuit so as to be lowered.

In the present invention, vehicle speed information is fetched into the control unit in the form of a pulse train and counted by the frequency counter. Based on the counting result, the high frequency characteristic of the video amplifier circuit is adjusted stepwise in accordance with the increase of the vehicle traveling speed, and the image quality is switched to a soft image according to the vehicle traveling speed.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a vehicle-mounted television device. In the figure, 1 is a receiving antenna, 2 is a video receiving circuit, 3 is an audio signal circuit, 4 is a speaker, 5 is a video amplifying circuit, 6 is a monitor device such as a CRT or LCD,
Reference numeral 7 is an input terminal to which vehicle speed information is supplied, 8 is a buffer circuit for matching the impedance of the input signal, 9 is a control unit, and 10 is an image quality adjustment circuit.

The speed information supplied to the input terminal 7 is usually a pulse signal for driving or displaying the speedometer of the vehicle and is extracted from the transmission of the vehicle.
It is generated in the form of a pulse train whose frequency is proportional to the traveling speed. This pulse train forms a frequency of 0.35 Hz when the speed is 1 km / H and 21.23 Hz when the speed is 60 km / H, for example. In the embodiment, velocity information consisting of this pulse train is used.

The control unit 9 is composed of a microcomputer and controls the operation of each unit of the receiver and controls the image quality adjusting circuit 10 in the next stage. The control unit 9 counts the pulse train of the input signal and A, B , C, D four output ports are provided. As a result of counting the frequency of the input signal, the frequency counter is configured to sequentially output the control signal to each of the four output ports for each predetermined count value.

Further, the image quality adjusting circuit 10 includes an image amplifying circuit 5
Is a circuit for controlling the high frequency characteristics of the above to adjust the image quality, and is composed of, for example, an integral type correction circuit. This circuit raises the high frequency for signals with a good signal-to-noise ratio S / N, adjusts the contours for clear image quality, and lowers the high frequency for signals with degraded S / N. , Which can lower the sharpness and improve the apparent S / N, and is provided as a sharpness circuit in a general television receiver.

FIG. 4 shows an example of the frequency characteristic of the image quality adjusting circuit 10. The image quality adjusting circuit is controlled by the control signals sent to the four output ports of the control section 9, and as a result,
The high frequency of the image amplification circuit 5 is adjusted to the characteristic shown in the figure.

Next, the operation of the embodiment will be described with reference to the flow charts of FIGS. First, step (S-
In the initial setting of 1), when the video reception circuit 2 is operated to receive a desired radio wave, the speaker 4 receives the audio signal of the broadcast wave, and the monitor 6 receives the video. At the same time, the control unit 9 resets the frequency counter to read and count the vehicle speed information supplied to the input terminal 7 (S-2).

The control unit 9 then determines the current vehicle speed from the counting result of the frequency counter. For example, when the actual vehicle speed is 20 km / H or less, as a result of comparing this output pulse train with the data A stored in the control unit 9, 2
It is judged to be 0 km / H or less (S-3). As a result, the control signal is output to the output port A, and the image quality adjustment circuit 10 generates the signal controlled by the output port A. Therefore,
The frequency characteristic of the video amplifier circuit 5 is corrected so that the high frequency is attenuated by one step as shown by the curve A in FIG. 4, and the sharpness of the image displayed on the monitor is slightly lowered (S
-6).

Next, in step (S-4), the count result of the input pulse train is compared with the data B, and when it is determined that the current vehicle speed is less than 40 km / H, a control signal is output to the output port B. Is output (S-7), and the image quality adjustment circuit 10 is controlled based on this signal. As a result, the high frequency characteristic of the video amplifier circuit 5 is further attenuated by one stage as shown by the curve B in FIG.

If it is determined in step (S-4) that the vehicle speed is 40 km / H or higher, it is determined in the next step (S-5) whether the current vehicle speed is 60 km / H or higher. If the determination result is as follows, a signal is sent to the output port C of the control unit 9 (S-8). Then, the high frequency characteristic of the video amplifier circuit 5 is corrected to the C curve of FIG.

If it is determined in step (S-5) that the vehicle speed is 60 km / H or more, there is an output at the output port D of the control unit 9, and similarly, the high frequency characteristic of the video amplifier circuit 5 is obtained. Is corrected like a D curve (S-
9).

As described above, when the vehicle speed increases, the high frequency characteristic of the video amplifier circuit 5 is corrected in accordance with the increase, and the apparent S / N ratio is improved.
The image displayed on the monitor 6 is sharp when the vehicle is stopped or the speed is low, but as the vehicle speed increases, the high frequency decreases by one step and gradually becomes soft. Therefore, the disturbance of the image when the influence of the multipath while the vehicle is traveling or when the obstacle such as the fluctuation of the electric field strength is received is substantially improved.

By the way, when the vehicle travels on a congested road, the traveling speed constantly changes, so that the output port of the control unit 9 for outputting the control signal also frequently changes. As a measure for avoiding such an unnecessary operation, the process of FIG. 3 may be added to the route returning from the point A of the flowchart of FIG. 2 to step (S-2).

In the processing of FIG. 3, when a control signal is sent to any of the output ports, this control signal is held for a certain period of time, and the high frequency characteristic of the video amplifier circuit 5 is kept constant by the held control signal. I try to control the time.

In step (S-10), the output port output by the control signal is stored, and the timer starts time measurement. In step (S-11),
When the fixed time has elapsed, the stored output port is reset and the control signal obtained from the counting result of the frequency proportional to the current vehicle speed is validated (S-12).

As described above, by adding the process of FIG. 3 to the flow of FIG. 2, it is possible to prevent the image quality from being constantly changed due to the frequent fluctuation of the vehicle speed. In the embodiment, the number of output ports that makes the image quality stepwise soft is provided at four stages, but the present invention is not limited to this, and may be four or more, or two.

[0025]

As described above, according to the vehicle-mounted television device of the present invention, means for introducing the vehicle speed information into the device, and a signal to the output port for reading the speed information and for each constant count value. Since the frequency counting means for sending out and the image quality adjustment signal generating means for controlling the frequency characteristic of the video amplifier circuit are provided, the video amplifier circuit is controlled so that a sharp image is displayed while the vehicle is stopped or running at low speed. Then, when the vehicle speed increases, the high frequency characteristics of the video circuit are corrected so that the image is switched to a softer image in accordance with the increase, and there is a reception failure due to multipath and variations in the electric field strength while the vehicle is running. Accordingly, the deteriorated S / N can be improved, and thereby the image disturbance can be substantially prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a vehicle-mounted television device.

FIG. 2 is a flowchart illustrating the operation of the embodiment.

FIG. 3 is a flowchart illustrating the operation of the embodiment.

FIG. 4 is a frequency characteristic diagram of a video amplifier circuit.

[Explanation of symbols]

 2 image receiving circuit 3 audio signal circuit 4 speaker 5 image amplifying circuit 6 monitor device 7 vehicle speed information input terminal 9 control unit 10 image quality adjusting circuit

Claims (1)

[Claims] 1. A means for introducing vehicle speed information into the device, a frequency counting means for counting the speed information and sequentially sending a signal to a control unit output port at a constant count value, and a frequency counting means for sending the signal. An on-vehicle television set comprising: an image quality adjustment signal generating means for controlling a frequency characteristic of a video amplifier circuit based on the display means; and a display means for displaying an output of the video amplifier circuit.