JPH0865576A - Camera video switching device - Google Patents

Abstract

PURPOSE: To determine switching timing when switching plural camera videos and to prevent of irregularities of a video or recording omission on a screen by detecting the first fall of a vertical synchronizing signal at the time of inputting a camera switching request signal, and then immediately switching a circuit to a prescribed position. CONSTITUTION: Video signals from cameras 1 to 4 are sent to the switching circuit 6. The cameras 1 to 4 are mutually synchronized by a synchronizing signal S1 generated from a synchronizing signal generating part 5. When a switching request signal S2 is sent to a control part 8 through a detection part 7, the control part 8 allows the detection part 7 to detect the start point of a vertical synchronizing signal and immediately switches the circuit 6 to a prescribed position based upon the request signal S2. Consequently the generation of switching immediately before the end of a vertical blanking interval can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera image switching device, and more particularly, to a switching device for preventing image distortion when switching a plurality of camera images.

[0002]

2. Description of the Related Art When a plurality of camera images are switched and monitored, switching is performed without considering the timing of switching as a conventional general method. Therefore, there is a drawback that the video becomes unsynchronized at the time of switching and the monitor video is difficult to see, and the video during the switching period cannot be recorded as normal video (missing recording).

[0003]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks of the prior art. When switching a plurality of camera images, the switching timing is determined.
It is an object of the present invention to provide a camera image switching device that prevents the disturbance of images on the projected screen and the omission of recording.

[0004]

SUMMARY OF THE INVENTION The present invention is directed to a switching circuit for selecting a desired video signal from among synchronized video signals from a plurality of cameras, and a switching circuit for requesting the switching circuit to switch to a predetermined position. When the request signal is input, the first vertical blanking period start point after the input of the switching request signal is detected, and a detection unit that outputs a detection signal when the same is detected, and the detection unit is controlled, Provided is a camera image switching device including a control unit for switching control of the switching circuit to a predetermined position based on the switching request signal when a detection signal is input from the detection unit.

[0005]

[Function] Each of the plurality of cameras is externally synchronized (horizontal, vertical). When the camera switch request signal is input, the control unit causes the detection unit to fall (vertical blanking period) for the first time after the input of the switch request signal of the vertical synchronization signal (negative polarity) used for the external synchronization. Start point). After this detection, the control unit immediately switches the switching circuit to the predetermined position based on the switching request signal. Alternatively, as an alternative to the above, if the first falling edge of the vertical synchronizing signal is detected, the switching circuit is switched to a predetermined position based on the switching request signal after a predetermined time after the detection. The "predetermined time" in this case is managed as follows. The counter counts the clock signal of a predetermined cycle. The switching circuit is switched when the count reaches a predetermined number. Alternatively, the reference time is stored in the memory unit, the time after the vertical synchronization fall is detected by the clock unit, and the comparison determination unit compares the measured time with the reference time. When both sides match, the switching circuit is switched.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A camera image switching device according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of essential parts showing an embodiment of a camera image switching device according to the present invention.
FIG. 2 shows the case of switching between two cameras.
3 is a block diagram of a main part of another embodiment of the camera image switching device according to the present invention, and FIG. 4 is a vertical sync signal waveform diagram for explaining FIGS. 1 to 3. Shows a negative sync signal, and (B) shows a positive sync signal. FIG.
1 to 4 are video cameras A, B, C and D,
Reference numeral 5 is a sync signal generator for generating external sync signals (horizontal and vertical), 6 is a switching circuit for switching the camera image, 7 is a detector for detecting the start point of the vertical sync signal, 8 is a detector 7 and a switching circuit 6 Is a control unit for controlling. In FIG.
The same components as those in FIG. 1 are denoted by the same reference numerals, 9 is a counter for counting clocks of a predetermined cycle, 10 is a detection unit 7,
It is a control unit that controls the counter 9 and the switching circuit 6. Further, in FIG. 3, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals, 11 is a clock unit for measuring time, 12 is a memory unit that stores a reference time, and 13 is a clock unit. A comparison determination unit that compares the measured time by 11 and the reference time of the memory unit 12 and determines whether they match each other. Reference numeral 14 controls the detection unit 7, the clock unit 11, the memory unit 12, the comparison determination unit 13, and the switching circuit 6. It is a control unit that does.

Next, the operation of the present invention will be described with reference to the drawings. (1) Description of FIG. 1 Video signals from each of the four cameras (1 to 4) are sent to the switching circuit 6. The cameras are synchronized with each other by a synchronization signal (horizontal and vertical) S1 from the synchronization signal generator 5. Further, the vertical synchronizing signal S2 in the synchronizing signal S1 is sent from the synchronizing signal generator 5 to the detector 7. Now, it is assumed that a signal (switch request signal S3) requesting to switch the camera to a predetermined one is sent to the control unit 8. The switching request signal S3 includes one based on manual switching and one based on automatic switching (sequential switching), but the signals themselves are the same. When the switching request signal S3 is input, the controller 8 causes the detector 7 to detect the start point of the vertical synchronizing signal. The detection in this case is the detection of the first starting point after the input of the switching request signal S3. This is done to prevent switching immediately before the end of the vertical blanking period.

As the vertical synchronizing signal S2 used for the detection of the starting point, there are a negative polarity signal shown in FIG. 3A and a positive polarity signal shown in FIG. 3B. In both figures, a and b are vertical synchronization signals, and if the signal is, for example, the NTSC system, the period T1 = 16.7 (mS). Also, pulse width (return period) T2
Is set to T2 = 500 (μS). For example, the start point detected when the input of the switching request signal S3 is at time T3 is T4, and the start point detected when the input is at time T5 during the vertical blanking period is T6. If the vertical synchronizing signal S2 has a negative polarity (A), T4 or T6 is at a position where it changes from H (high level) to L (low level), and if it has a positive polarity (B), T4 or T6. Or, T6 is a place where L (low level) changes to H (high level). As described above, when the detection unit 7 detects T4 or T6, the detection signal is sent to the control unit 8
Send to. The control unit 8 which has detected the detection signal switches the switching circuit 6 to a predetermined position based on the switching request signal S3 by the switching control signal S4 (for example, position b). By this switching, the required camera video signal S5 is selected.

(2) Description of FIG. 2 In FIG. 1, the control unit 8 switches the switching circuit 6 immediately after the start point of the vertical blanking period is detected. However, FIG.
If the switching is completed within the blanking period T2 of the vertical synchronizing signal shown in (4), it is not always necessary to switch immediately after the start point is detected. As long as the switching is completed within the blanking period T2,
This is because the image is not distorted on the screen. FIG. 2 is based on this idea, and counter 9 is different from FIG.
Is provided. The detection unit 7 has the same function as in FIG. Therefore, as in the case of FIG. 1, when the detection unit 7 detects the start point of the vertical blanking period based on the input of the switching request signal S3, the control unit 10 causes the counter 9 to count the clock signal of a predetermined cycle. Here, the count number (predetermined number) that completes the switching within the blanking period T2 is set in advance. When the count reaches the predetermined number (T7 has elapsed), the control unit 10 switches the switching circuit 6 to the predetermined position.
By this switching, the required camera video signal S5 is selected.

In the case of FIG. 2, the time required for switching should be equal to or less than the time (T2-T7) obtained by subtracting the predetermined count number (= T7) from the blanking period T2. Is. If this condition is not satisfied, the vertical blanking period will end before the switching is completed, and image distortion will appear on the screen. If T2 = 500 (μS) in the above example makes it difficult to satisfy the above condition for the time required for switching, T2 may be lengthened.

(3) Description of FIG. 3 The case of FIG. 3 is also based on the same idea as that of FIG. 2, and a clock unit 11, a memory unit 12, and a comparison / discrimination unit 13 are provided in comparison with FIG. There is. The clock unit 11 and the like replace the counter shown in FIG. The detection unit 7 has the same function as in FIGS. Therefore, as in the case of FIG. 1 etc., the switching request signal S3
When the detection unit 7 detects the start point of the vertical blanking period based on the input of, the control unit 14 causes the clock unit to measure the time. On the other hand, the memory unit 12 stores a reference time serving as a reference for the switching timing of the switching circuit 6. The comparison determination unit 13 compares the reference time with the measurement time of the clock unit 11, and determines whether the measurement time is the reference time. And
When the measurement time becomes the reference time (coincidence) (T7), the control unit 14 switches the switching circuit 6 to a predetermined position. By this switching, the required camera video signal S5 is selected.

As in the case of FIG. 2, the switching time must be equal to or less than the time (T2-T7) obtained by subtracting the reference time (= T7) from the blanking period T2. is there. If this condition is not satisfied, the vertical blanking period will end before the switching is completed, and image distortion will appear on the screen. If the time required for switching is difficult to satisfy the above condition with T2 = 500 (μS) in the above example, T2 may be lengthened as in the case of FIG.

(4) Diversion of FIG. 3 In the description of the preceding paragraphs (1), (2) and (3), the detection unit 7 detects the first vertical blanking period start point after the switching request signal S3 is input. However, the following may be performed separately. The detection unit 7 always detects the vertical blanking period start point,
The detection signal is sent to the control unit 14. The clock unit 11 also constantly measures time based on the detection signal. The storage of the reference time in the memory unit 12 is the same as in (2) above. Control unit
When the switching request signal S3 is input, a comparison / discrimination unit 13 compares the time measured by the clock unit 11 with the reference time, and determines whether the measurement time is within the reference time. If it is determined that the measurement time is within the reference time, the switching circuit 6 is switched to the predetermined position. Even in the case of this method, it is necessary that the time required for switching is equal to or less than the time (T2-T7) obtained by subtracting the reference time (= T7) from the blanking period T2. The same as (3) and the like. In other words, this method is based on the assumption that the switching request signal S3
Even if the input is within the vertical blanking period, if the switching can be performed within the remaining blanking time, the switching is immediately performed. The reference time for storage in the memory unit 12 serves as a criterion for this determination. Therefore, the block diagram for this method is the same as in FIG.

[0014]

As described above, according to the present invention, when switching the images from a plurality of cameras, the switching is performed within the vertical blanking period, so that the disorder of the images on the screen can be prevented. In addition, the image before the vertical blanking period is normally recorded, and there is no recording omission. Conventionally, the timing of switching is not specified in particular, so it may switch during the video period, which may result in video disturbance on the screen, and due to the disturbance, the video cannot be recorded normally, resulting in missing recording. In contrast to this, the present invention eliminates the disturbance of the image and the lack of recording, makes it easy for a person who monitors to see the image, and eliminates the drawback of being unable to monitor due to the loss of recording. From the above, the present invention can contribute to improving the performance of the camera image switching device.

[Brief description of drawings]

FIG. 1 is a block diagram of essential parts showing an embodiment of a camera image switching device according to the present invention.

FIG. 2 is a block diagram of a main part of another embodiment of the camera image switching device according to the present invention.

FIG. 3 is a block diagram of a main part of another embodiment of the camera image switching device according to the present invention.

4A and 4B are vertical synchronization signal waveform diagrams for explaining FIGS. 1 to 3, and FIG. 4A is a negative polarity synchronization signal waveform diagram and FIG. 4B is a positive polarity synchronization signal waveform diagram.

[Explanation of symbols]

 1 Camera A 5 Synchronous signal generator 6 Switching circuit 7 Detection unit 8 Control unit 9 Counter 10 Control unit 11 Clock unit 12 Memory unit 13 Comparison determination unit 14 Control unit

Claims (6)

[Claims] 1. A switching circuit for selecting a required video signal from each of the synchronized video signals from a plurality of cameras,
When a switching request signal requesting to switch the switching circuit to a predetermined position is input, the start point of the first vertical blanking period after the input of the switching request signal is detected from the input vertical synchronization signal, and when the same is detected. And a control unit that controls the detection unit and controls switching of the switching circuit to a predetermined position based on the switching request signal when the detection signal is input from the detection unit. A camera image switching device characterized by being configured. 2. A switching circuit for selecting a required video signal from the respective synchronized video signals from a plurality of cameras,
When a switching request signal requesting to switch the switching circuit to a predetermined position is input, the start point of the first vertical blanking period after the input of the switching request signal is detected from the input vertical synchronization signal, and when the same is detected. A detection unit that outputs a detection signal, a counter that starts counting the clock signal when the detection signal is input from the detection unit, the detection unit and the counter, and the count by the counter reaches a predetermined number. A camera image switching device, comprising: a control unit for controlling switching of the switching circuit to a predetermined position based on the switching request signal when the number reaches. 3. A switching circuit for selecting a desired video signal from each of the video signals synchronized from a plurality of cameras,
When a switching request signal requesting to switch the switching circuit to a predetermined position is input, the start point of the first vertical blanking period after the input of the switching request signal is detected from the input vertical synchronization signal, and when the same is detected. A detection unit that outputs a detection signal, a clock unit that starts time measurement when the detection signal is input from the detection unit, a memory unit that stores a reference time, a measurement time by the clock unit, and the reference The comparison determination unit that compares the time with each other and determines the coincidence of both times, and controls the detection unit, the clock unit, the memory unit and the comparison determination unit, and in the comparison determination unit, the measurement time by the clock unit And a reference time, the control circuit controls the switching circuit to switch to a predetermined position based on the switching request signal. . 4. A switching circuit for selecting a desired video signal from each of the video signals synchronized from a plurality of cameras,
A detection unit that detects the vertical blanking period start point from the input vertical synchronization signal and outputs a detection signal when the detection is made, a clock unit that starts time measurement when the detection signal is input from the detection unit, and a reference When a memory unit that stores time and a switching request signal requesting switching of the switching circuit to a predetermined position are input, the time measured by the clock unit is compared with the reference time, and the measured time is compared. While controlling the comparison / determination unit that determines whether or not it is within the same reference time, the detection unit, the clock unit, the memory unit, and the comparison determination unit,
In the comparison / discrimination unit, when the time measured by the clock unit is within the reference time, the control circuit switches the switching circuit to a predetermined position based on the switching request signal. Switching device. 5. The method according to claim 1, wherein the detection unit detects the rising edge of the vertical synchronization signal based on the positive polarity vertical synchronization signal. Alternatively, the camera image switching device according to claim 4. 6. The method according to claim 1, wherein the detection section detects the trailing edge of the vertical synchronizing signal based on the negative vertical synchronizing signal. The camera image switching device according to claim 3 or claim 4.