JPH01268261A - Camera system - Google Patents

Abstract

PURPOSE:To reduce the influence of a synchronizing signal to a video signal and to prevent the degradation in picture quality, etc., from being generated by causing the synchronizing signal, which is transmitted from a camera control unit to a camera head unit, to be the amplitude modulating signal of a high frequency signal. CONSTITUTION:For the synchronizing signal to be transmitted from a camera control unit 1, the high frequency signal is amplitude-modulated (circuit 11) by the synchronizing signal to be generated in the camera control unit 1. Then, an amplitude modulating signal is demodulated (circuit 14) by a camera head unit 2 and the synchronizing signal is obtained. Thus, by causing the transmitted synchronizing signal to be the amplitude modulating signal of the high frequency signal, the influence of the synchronizing signal is reduced to the video signal and the degradation of the picture quality, etc., due to the influence can be widely improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a camera control unit and a camera control unit.
The present invention relates to a camera system with a separate head unit.

[Summary of the invention]

The present invention relates to a camera system, in which the influence of the synchronization signal on the video signal is reduced by making the synchronization signal transmitted from the camera control unit to the camera head unit an amplitude modulation signal of a high frequency signal. This is to prevent the occurrence of image quality deterioration etc.

[Conventional technology]

For example, a camera head unit that forms a video signal)
There is a camera system in which a CHU (CHU) and a camera control unit (CCU), which processes video signals, are separated. In such a camera system, CHU
and CCU are each provided with a synchronization signal generation circuit,
The synchronization signal from the synchronization signal generator circuit controls internal circuits such as formation and processing of each video signal.

Therefore, when using such a camera system, it is necessary to synchronize the synchronization signal generating circuits. That is, in order to process the video signal formed by the CHU in the CCU, the phase of the video signal transmitted from the CHU to the CCU needs to match the synchronization signal of the CCU.

Therefore, for example, a device as shown in FIG. 5 can be considered. The diagram shows the entire camera system, and the right side of the drawing shows the camera system.
A control unit (CCU) (1) and a camera head unit (CHU) (2) are shown on the left side, and these are connected via a so-called multi-core cable (3).

This CCU (1) is provided with a first synchronization signal generation circuit (52) driven by a reference oscillator (51),
Vertical synchronization signal (pulse) V from this generation circuit (52)
D is transmitted to the second synchronizing signal generating circuit (54) through the reset signal generating circuit (53). Also, the generation circuit (5
The horizontal synchronization signal (pulse) HD from 2) is supplied to a variable oscillator (56) through a phase comparison circuit (55), and this oscillation signal is supplied to a generation circuit (54). The generated composite synchronization signal Sync is then transmitted to the multicore cable (3) through the output circuit (57).

On the other hand, in the CHU (2), the composite synchronization signal Sync transmitted through the multi-core cable (3) is sent to the separation circuit (
58) is supplied to the vertical pulse VD and the horizontal pulse HD.
is separated, and this separated vertical pulse VD is sent to the synchronization signal generation circuit (60) through the reset signal generation circuit (59).
). In addition, the horizontal pulse HD from the separation circuit (58) passes through the phase comparator circuit (61) to the variable oscillator (6
2), and this oscillation signal is supplied to the generation circuit (60). Furthermore, the horizontal synchronizing pulse HD from the generation circuit (60) is supplied to the phase comparison circuit (61).

Further, the horizontal pulse HD from the separation circuit (58) is retransmitted to the multicore cable (3) through the output circuit (63).

Then, the horizontal pulse HD retransmitted at CCU (1)
is supplied to the phase comparison circuit (55) through a correction circuit (64) for waveform shaping, etc.

Thereby, the generation circuit (60) is synchronized so that the retransmitted horizontal pulse HD matches the phase of the original synchronization signal.

The vertical pulse VD and horizontal pulse HD from this generation circuit (60) are supplied to the timing generation circuit (31),
A vertical shift clock φV and a horizontal shift clock φ□ are generated in synchronization with the vertical pulse VD and horizontal pulse HD. This clock φ9 is a CC for forming a video signal.
D (32R) (32G) (32B), and the clock φH is supplied to the CCD output register (33R
) (33G) (33B) The generated video signal is extracted. This video signal is sent to each sample hold circuit (34R) (34G) (34B
), and the sampling pulse from the generation circuit (31) is supplied to this circuit. This sampled video signal is output to the output circuit (35R) (35G) (3
5B) to the multicore cable (3).

Furthermore, the video signal transmitted through the multi-core cable (3) is transferred to the floating amplifier (36R) (36G) (3
6B) is supplied to a process circuit (37) that performs processing such as γ correction and white clipping, and this processed signal is supplied to an encoder (38) to form a predetermined composite signal. This composite signal is supplied to the mixing circuit (39), and the vertical pulse VD and horizontal pulse HD from the generating circuit (52) are combined by the blanking generating circuit (40) and supplied to the mixing circuit (39), which mixes The resulting composite video signal is taken out to an output terminal (41).

In this way, according to the above-described device, the phase of the video signal transmitted from the CHU to the CCU can be made to match the synchronization signal of the CCU, and it is possible to perform good video signal processing.

[Problem to be solved by the invention]

However, in the above-mentioned apparatus, when the length of the multi-core cable was increased to a long distance of, for example, 100 m or more, a phenomenon occurred in which dark and light vertical stripes appeared on the left edge of the screen, significantly degrading the image quality.

This application attempts to elucidate the causes of such image quality deterioration and to develop countermeasures.

[Means to solve the problem]

The present invention transmits the synchronization signal Sync generated by the camera control unit (1) to the camera head unit [2] via the multi-core cable (3), and Generates a pulse synchronized with the synchronization signal transmitted above (circuit (31)) t
,, forms a video signal based on the generated pulses (CCD (
32R) (32G) (32B)) L, in a camera system in which the video signal is transmitted to the camera control unit via the multi-core cable, the synchronization signal transmitted from the camera control unit; The signal is a high frequency signal that is amplitude modulated (
Circuit (11)) signal and none, the above camera head
This camera system is characterized in that the unit demodulates the amplitude modulation signal (circuit (14)) to obtain the synchronization signal.

[Effect]

According to this, by using the amplitude modulation signal of the high-frequency signal as the synchronization signal to be transmitted, the influence of the synchronization signal on the video signal is reduced, and image quality deterioration caused by the synchronization signal can be significantly improved.

〔Example〕

First, we will clarify the cause of image quality deterioration.

Generally, when transmitting signals using a coaxial line, if all return current is returned through the shield of the coaxial line (making the ground completely independent), magnetic flux disturbance to the surrounding areas will not occur.

However, in reality, it is difficult to return all of the return current through the shield of the coaxial line, and this difference generates magnetic flux outside the coaxial line. .

In addition, when using a coaxial line, there is a delay in the transmitted signal, and the delay time is, for example, if the dielectric constant ε of the insulating material between the core wire and the shield is 2.3 (polyethylene), the waveform shortening rate of the coaxial line is Since □=0.66 and f, a delay of approximately 0.5 μsec occurs per 100 m. Therefore, the phase of the sending signal and the phase of the return signal on the signal sending side are 0.5 + 0.5 per 100 m.
= 1.0μsec, and at 300m it will be 3.
It becomes even 0 μsec. Therefore, during this period of deviation, magnetic flux may be generated outside the coaxial line.

When magnetic flux is generated outside the coaxial line in this way, if there is a circuit that couples with it, energy will be transmitted through this magnetic flux, causing mutual effects on the signals flowing through each coaxial line. is possible.

Therefore, in order to reduce such effects, it is conceivable to first separate the coaxial lines that cause the effects.

By the way, the multicore cable (3) that connects CCU (1) and C:HU (2) generally has seven coaxial wires (3a) to (3g) arranged on the circumference, as shown in Figure 3. The one placed is used. Since it is not preferable to perform processing such as level reduction on the video signal, for example, the video signals of the three primary colors (R, G, B) are not adjacent to each other as shown in the figure, R→(3c), G→( 3b), B → (3e)
so that it is transmitted through a coaxial line. However, in this case, the transmission of the synchronization signal from CCU (1) to CHU (2) and the retransmission of horizontal pulses from CHU (2) to CCU (1) are performed using the coaxial line adjacent to any video signal. This will have to be done.

Therefore, we will further consider the influence of the synchronization signal on the video signal.

The reason why energy transmission occurs between two adjacent coaxial wires as described above is considered to be due to the existence of mutual inductance M between the two wires, as shown in FIG. 4A, when considered in terms of an equivalent circuit. In other words, the synchronous pulse has mutual inductance M
The video signal enters the coaxial line through the coaxial line, and the distributed capacitance C of the coaxial line
This can be considered as a phenomenon that occurs in a circuit including the terminating resistor R. 6 Therefore, the above-mentioned circuit is modeled as shown in Figure B, and the pulse waveform shown in Figure C is analyzed.

That is, when the changes after the rear end of the pulse (1=0) are analyzed, we get the following (1). If we transform this into Laplace, we get...(2), and if we rearrange this, we get...(3). Then, by inverse transformation, we solve this...
4] °, ∆-2πJ and V (ii) When k=1...(5) (iii) When k<1...(6)

As is clear from these equations, when the damping coefficient k becomes less than 1, the pulse response becomes an oscillating system, and the oscillating wave appears after t-0. Therefore, this vibration wave affects the video signal, causing image quality deterioration.

By the way, the amplitude (size of influence) of this vibration wave is as described above (
6) is expressed by the formula. Therefore, when formula (6) is considered, this vibration depends on the peak value E and pulse width T of the pulse.

In the device described above, by reducing the peak value and pulse width of the synchronizing signal, the influence of the synchronizing signal on the video signal can be significantly reduced.

However, in the above-mentioned apparatus, since the transmitted synchronization signal is input to a level reproduction switch circuit on the transmission side, a level for performing this switching is required.

That is, in general, when using a transistor switch circuit, 1. OVl, -p (2.0Vp-p on the sending side)
A certain level is required.

Furthermore, if the pulse width of the synchronization signal is narrowed, there is no problem with horizontal synchronization, but vertical synchronization may not be readable.

Therefore, FIG. 1 is a block diagram of an embodiment constructed in consideration of these points.

In this figure, the synchronization signal generation circuit (
The composite synchronization signal Sync from 54) is sent to the modulation circuit (11
), for example, a color subcarrier frequency signal from a reference oscillator (51) is supplied to a modulation circuit (11), and the signal from the oscillator (51) is converted into a composite synchronization signal S yn
The amplitude is modulated by c. The signal from this modulation circuit (11) is sent to the multicore cable (3) through the output circuit (12).
transmitted to.

On the other hand, in the CHU (2), the amplitude modulation signal transmitted through the multi-core cable (3) is supplied to the demodulation circuit (14) through the high frequency amplifier (13), and the demodulated composite synchronization signal Sync is sent to the separation circuit. (58).

Therefore, in this device, the synchronization signal generation circuit (54) of the CCU (1) generates a -composite synchronization signal Sync as shown in FIG. 12) to form an amplitude modulated signal as shown in the figure, which is transmitted to the multicore cable (3).

In this case, since the synchronization signal S'ync transmitted to the multicore cable (3) is a high frequency signal, this pulse width T is extremely small and generates vibration waves that affect the video signal. Therefore, the occurrence of image quality deterioration can be effectively prevented.

Note that the influence between coaxial lines is thought to be caused not only by the mutual inductance mentioned above, but also by capacitive Ll coupling between the lines, especially in the case of high-frequency signals, but since the influence of this capacitive coupling becomes a differential waveform, the synchronous signal By selecting the phase of , it is possible to limit the influence within the blanking period and prevent image quality deterioration during the video period.

In this way, according to the above-mentioned device, by using the amplitude modulation signal of the high frequency signal as the synchronization signal to be transmitted, the influence of the synchronization signal on the video signal is reduced, and image quality deterioration caused by the synchronization signal can be significantly improved.

It has been confirmed through experiments that transmission of 300 m is possible with the above-mentioned device.

〔Effect of the invention〕

According to this invention, by using an amplitude modulated high-frequency signal as the synchronization signal to be transmitted, the influence of the synchronization signal on the video signal is reduced, and image quality deterioration caused by this can be significantly improved. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an example of the present invention, FIGS. 2 to 4 are diagrams for explaining the same, and FIG. 5 is a diagram for explaining the conventional technique. (1) is the camera control unit, (2) is the camera head unit, (3) is the multi-core cable, (1)
1) is a modulation circuit, (14) is a demodulation circuit, (32) is a CC
D. (37) is a process circuit, and (39) is a mixing circuit. Agent Mamukai Ito
Hide Matsukuma Ol 0koku α −〇

Claims (1)

[Claims] A synchronization signal formed by a camera control unit is transmitted to a camera head unit via a multi-core cable, and the camera head unit synchronizes with the transmitted synchronization signal. In a camera system that generates a pulse, forms a video signal based on the generated pulse, and transmits the video signal to the camera control unit via the multi-core cable, the camera control unit The synchronization signal transmitted from the camera control unit is a signal obtained by amplitude modulating a high frequency signal using the synchronization signal generated by the camera control unit, and the camera head unit demodulates the amplitude modulation signal to generate the synchronization signal. A camera system characterized by: