JPH0476549B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a synchronization signal processing device for an information display device that displays various types of information as images using superimposition.

2. Description of the Related Art Displaying information on a television receiver is an effective method because it provides a large amount of information and has a large visual appeal. In particular, there is a method that uses superimposition technology to display a television broadcast image in the background and an information image in front of it. This is a convenient method for displaying information because the information image does not occupy the screen of the television receiver.

FIG. 2 is a block diagram of a conventional information display device using superimposition. A video signal inputted from a terminal 1 is separated into a synchronizing signal by a synchronizing signal separating means 2, and is inputted to a video generating means 4 through a switch 3. The video generating means 4 uses the input synchronization signal to generate a video signal for displaying necessary information. This video signal is input to the mixing means 5. The other input of the mixing means 5 is connected to the terminal 1, and the original video signal is also input thereto. The mixing means 5 performs an operation of superimposing the information image generated by the image generating means 4 on the background of the image of the original image signal. The mixed image thus created is output from the terminal 6 and sent to display means such as a television receiver. Further, when no video signal is input from terminal 1, a synchronization signal cannot be obtained. Therefore, at this time, the switch 3 is switched to apply the synchronizing signal output from the synchronizing signal generating means 7 to the video generating means 4. At this time, there is no background video, but it is possible to obtain video to display the necessary information.

Problems to be Solved by the Invention In conventional information display devices, the synchronization signal must be manually switched every time a background video signal is no longer input, which is extremely time-consuming. Furthermore, if the synchronization signal is obtained when the quality of the input video signal is poor, the quality of the separated synchronization signal will also be poor, making it impossible to display the information video normally. This may lead to a delay in the transmission of information when important information is displayed (such as the occurrence of a flame), leading to a dangerous situation.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention:
synchronous signal separating means for inputting a video signal; a counter that counts a predetermined clock and is reset by the synchronous signal output from the synchronous signal separating means; an inverting means for logically inverting the output of the counter; a first AND means that receives the output of the signal separation means and the output of the inversion means; a synchronization signal generation means that generates a synchronization signal; and a second logic product that receives the output of the counter and the output of the synchronization signal generation means. It is composed of an AND means and an OR means which inputs the outputs of the two AND means.

Function In the above configuration, the counter outputs a logic 1 when the predetermined count time is reached, and the count time is set longer than the horizontal synchronization, and when the quality of the input video signal is good, the counter outputs a logic 1 signal that is separated from the input video signal. A signal is output, and when the quality is poor, a signal from a synchronizing signal generating means is output.

Embodiment An embodiment of the present invention is shown in FIG. The video signal input from the terminal 10 is input to the synchronization signal separation means 11, where the synchronization signal is separated. This synchronization signal is connected to the reset terminal 13 of the counter 12 and the first
is input to the logical product means 14. counter 12
Also, a clock is constantly inputted from the clock generating means 15, and this clock is counted. The output from the output terminal 16 of the counter 12 is input to an inverting means 17 and a second ANDing means 18. A signal from a synchronizing signal generating means 19 is also input to the second AND means 18 . The outputs of the first AND means 14 and the second AND means 18 are input to the OR means 20, subjected to an OR operation, and outputted from the terminal 21. When the quality of the video signal input from the terminal 10 is good, the synchronization signal separation means 1
The quality of the synchronization signal output from 1 is also good and becomes a regular pulse. The counter 12 always counts the clock of the clock generating means 15, and when a predetermined count time is reached, the output terminal 16
outputs a logic 1, and its count time is set to be longer than the horizontal synchronization period of the input video signal. Therefore, when the quality of the synchronization signal output from the synchronization signal separation means 11 is good, the synchronization signal is periodically input to the reset terminal 13 of the counter 12, and the counter 12 is reset for each horizontal synchronization signal. Therefore, the counter 12 is reset before counting the predetermined count time and the output terminal 16 always remains at logic zero. At this time, the input terminal 22 of the first AND means 14 is at logic 1.
At this time, the input terminal 23 of the second AND means 18 becomes logic 0. Therefore, the synchronizing signal output from the synchronizing signal separating means 11 is outputted from the output terminal 21 via the first AND means 14 and the OR means 20.
When the video signal inputted from the terminal 10 is not clear or of extremely poor quality, the synchronization signal output from the synchronization signal separation means 11 either disappears or becomes irregular. Therefore, since the counter 12 reaches the count time without being reset, a logic 1 is output from the output terminal 16. At this time, the input terminal 22 of the first AND means 14 is at logic 0.
Then, the input terminal 23 of the second AND means 18 becomes logic 1. Therefore, the synchronizing signal outputted from the synchronizing signal generating means 19 is outputted from the output terminal 21 via the second ANDing means 18 and the ORing means 20.
In this way, by determining the presence or absence of an input video signal and switching the synchronization signal, it becomes possible to always output the synchronization signal. By generating an information video using this synchronization signal, it is possible to display a superimposed video when there is a background video signal, and to display at least the information video even when there is no background video signal.

Effects of the Invention In the present invention, since it is possible to determine the presence or absence of a synchronization signal and automatically switch the synchronization signal, the effort required for switching is saved and usability is improved. Furthermore, by adjusting the count time, it is possible to easily adjust the threshold value for switching when the quality of the video signal is poor.
Furthermore, since only information images can be displayed at all times, it is possible to construct a device with good information transmission performance.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a synchronization signal switching device showing an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional information display device. 12... Counter, 14, 18... Logical product means, 17... Inverting means, 20... Logical sum means.

Claims (1)

[Scope of Claims] 1. A synchronizing signal separating means that inputs a video signal, a counter that counts a predetermined clock and is reset by a synchronizing signal outputted from the synchronizing signal separating means, and a logical system that processes the output of the counter. an inverting means for inverting, a first ANDing means for inputting the output of the synchronizing signal separating means and an output of the inverting means, and calculating a logical product thereof; a synchronizing signal generating means for generating a synchronizing signal; a second logical product means which inputs the output of the output and the output of the synchronizing signal generating means and calculates the logical product; a logical sum means for calculating a sum; the counter outputs a logical 1 when a predetermined count time is reached, and the count time is set to be longer than a horizontal synchronization period. 2. The synchronization signal switching device according to claim 1, wherein the counter has a plurality of outputs having different count times, and the threshold value for switching whether the input video signal is good or bad can be changed by selecting the counter output. .