JPS5849065B2 - Television Camera Souchino - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC reproduction system for video signals derived from a television camera head.

Conventionally, video signals derived from a television camera head are transmitted via a transmission cable called a camera cable.
This signal is supplied to a signal processing device including a camera controller and the like that converts it into a television signal.

In the signal processing device, the video signal is subjected to DC reproduction using a DC reproduction pulse signal whose horizontal retrace period, which serves as a reference level for setting the black level, is synchronized with the horizontal drive signal.

Further, a horizontal drive signal is supplied to the television camera device from a camera controller via a camera cable, and the horizontal deflection is drive-controlled based on this signal.

A flyback pulse is generated in response to this horizontal deflection,
Since this flyback pulse is at a high level, it leaks to the image pickup tube output, and in reality, a ripple, which is a substantially differential waveform of this flyback pulse, is superimposed on the above-mentioned video signal in the horizontal synchronization section.

This ripple-containing video signal is transmitted to the signal processing device via the camera cable as described above, so it is slightly delayed by this cable.

This delayed video signal is DC-regenerated by a clamp circuit or the like using a DC-regeneration pulse signal as described above.

Since this signal delay occurs, a horizontal phase adjustment circuit is provided which advances the phase of the horizontal drive signal supplied from the signal processing circuit to the television camera head in advance by delaying the input drive signal.

In DC reproduction, the horizontal retrace part of the video signal reproduced by the DC reproduction pulse signal includes ripples as mentioned above, and if the phase difference of each of these signals is constant, the ripples will be constant. This will result in a black level that is lower than the normal one, and this can be removed by later adjustment.

However, phase changes occur in horizontal phase adjustment circuits, etc. due to temperature changes, power supply fluctuations, etc., and the phase of the DC reproduction pulse signal varies with respect to the phase of the video signal, causing the DC reproduction portion (clamp point) for the ripples to change. As a result, the DC regeneration level is varied.

This variation in the DC level results in a variation in the black level, and particularly in a color television camera device, this causes an imbalance in the black level between the color signals and deteriorates color reproducibility.

In addition, when the camera cable length is changed, the horizontal phase adjustment circuit described above cannot completely compensate for the phase lag due to the change in cable length, resulting in a phase change between the DC reproduction pulse signal and the video signal, and the color Reproducibility has deteriorated.

The present invention provides a DC regeneration method for a television camera device that eliminates such drawbacks.

In this invention, a DC reproduction pulse signal is generated in synchronization with the phase of the above-mentioned flyback pulse and DC reproduction is performed in synchronization with the phase of the video signal, and when the television camera head is disconnected from the signal processing device, It is configured to generate a pulse signal based on the horizontal drive signal and to be capable of direct current reproduction when a test signal is introduced for inspection or the like in a signal processing device.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a circuit configuration, in which a television camera head 2 and a signal processing device 4 such as a camera controller are connected by a camera cable 6. As shown in FIG.

A horizontal drive signal is sent to the television camera head 2 from a signal processing device 4 through a camera cable 6 to a horizontal deflection circuit 8.
supplied to

This horizontal deflection circuit 8 sends a horizontal deflection signal to the image pickup tube 10.
The image signal is supplied to the deflection winding 12 of the image pickup tube 10, and a video signal is derived from the image pickup tube 10.

The video signal is supplied to the signal processing device 4 via an amplifier 14 and a camera cable 6.

Further, the flyback pulse generated by the horizontal deflection is led to the flyback sending circuit 16, and a phase detection signal indicating the phase is generated in synchronization with this pulse, and this phase detection signal is transmitted through the camera cable 6 to the signal processing device 4.
will be introduced in

As described above, the video signal and the phase detection signal are introduced into the signal processing device 4, and the video signal is led out to the output terminal 22 via the switch 17 for introducing the test signal, the amplifier 18, and the clamp circuit 20 for performing DC regeneration.

Further, the phase detection signal is supplied to a crank pulse generation path 24 and a horizontal phase adjustment circuit 26, respectively.

The horizontal phase adjustment circuit 26 is composed of a phase discrimination circuit, a variable delay circuit, etc., and is configured to delay the horizontal drive signal HD introduced to the external terminal 28 by about 1 phase delay and add it to the television camera head 2. The amount of delay is controlled according to the phase difference between the phase detection signal and the input horizontal drive signal HD.

Further, the horizontal drive signal HD is transmitted to the clamp pulse generation circuit 24.
is supplied together with the phase detection signal.

The clamp pulse generation circuit 24 is configured as shown in FIG. is derived.

As shown in FIG. 2, the crank pulse generating circuit 24 is supplied with a horizontal drive signal HD to a first input terminal 30 and a phase detection signal to a second input terminal 32.

The horizontal drive signal HD is supplied to the first pulse circuit 34 by the first pulse circuit 34.
The phase detection signal is made negative in polarity by the second pulse circuit 38 and introduced into the second transistor 40 .

The output of first transistor 36 is directly introduced into AND circuit 42 .

The low level side of the output of the second transistor 40 is held at ground potential by a diode clamp circuit consisting of a capacitor 44 and a diode 46, and is introduced into a third transistor 48 serving as a buffer circuit.

The output of the third transistor 48 is supplied to an inverting shift circuit 50.

From the shift circuit 50, a signal according to the phase detection signal,
When this phase detection signal is not supplied, that is, when the television camera head is disconnected, a signal of a predetermined level is generated.

In the AND circuit 42, the horizontal drive signal and the inversion shift circuit 50
The output is shaped into a predetermined delay and pulse width by a pulse delay shaping circuit 52 consisting of a monostable multivibrator or the like in order to obtain an appropriate clamp phase, and then DC regenerated from the output terminal 54 to the clamp circuit 20. Supplied as a clamp pulse signal.

The operation of the present invention having such a configuration will now be described in detail with reference to the signal waveforms shown in FIG.

FIG. 3a shows a horizontal blanking portion of the video signal S1 derived from the television camera head 2, in which a ripple S2 is superimposed due to the leakage of the flyback pulse S3 in FIG. 3b.

From the television camera head 2, a video signal S1 in FIG. 3a and a phase detection signal S4 in FIG. 3C indicating the phase of the flyback pulse S3 in FIG. 3b are derived.

Further, the horizontal drive signal HD shown in FIG. 3d is supplied to the signal processing device 4.

In the signal processing device 4, the phase detection signal S shown in FIG.
4 and the horizontal drive signal HD of FIG. 3d are introduced into the clamp pulse generation circuit 24 shown in FIG.

These phase detection signal S4 and horizontal drive signal HD are introduced into the AND circuit 42 via the first transistor 36, second and third transistors 40, 48, etc. in FIG.

The AND circuit 42 outputs an AND output signal S of these phase detection signals S4 and the horizontal drive signal HD, as shown in FIG. 3e.
, is derived.

The signal S from the AND circuit 42 is the pulse delay shaping circuit 5
2, a predetermined delayed and shaped DC reproduction pulse signal S6 shown in FIG. 3F is generated.

This DC reproduction pulse signal S6 is supplied to the clamp circuit 20, and the ripple 82 part of the video signal S1 shown in FIG. .

Although this DC level is deviated by the ripple 82 waveform, the amount is constant and this deviation can be removed by subsequent level adjustment.

Further, when the television camera head 2 is disconnected from the signal processing device 4, the clamp pulse generation circuit 24 generates a DC reproduction pulse signal S7 shown in FIG. 3g in synchronization with the horizontal drive signal HD.

That is, since the clamp pulse generation circuit 24 is not supplied with the phase detection signal S4 from the television camera head 2, the output of the second transistor 40 is eliminated, and the diode 46 of the diode clamp circuit is connected to the base of the third transistor 48. It is a constant operation that only allows the bias current to flow, and the output voltage of the third transistor 48 is the same when the output of the second transistor 40 is present (when there is a phase detection signal).
is equal to the low level of the inverting shift circuit 50.
The output will be at a constant high level.

Therefore, the horizontal drive signal HD is derived from the AND circuit 42, and the pulse delay shaping circuit 52 generates the DC reproduction pulse signal S7 shown in FIG. 3g.

The delay and shaping of this DC reproduction pulse S7 is the same as that of the DC reproduction pulse S6, and the DC reproduction of the test signal etc. supplied to the amplifier 18 corresponding to the video signal introduced into the signal processing device 4 by switching the switch 17 is It is done.

Note that the delay amount of the DC reproduction pulse signal S6 may be further increased by the pulse delay shaping circuit 52, and the horizontal synchronization portion after the ripple S2 may be reproduced by DC.

In this DC regeneration, since the ripple S2 is not included, the deviation of the regenerated DC level becomes small, and subsequent adjustment can be made unnecessary.

Therefore, according to the present invention, since the pulse signal for DC reproduction of the video signal from the television camera head 2 is maintained in a constant phase relationship with the phase detection signal S4, the advanced horizontal synchronizing signal supplied to the camera head is Even if the phase of the DC reproduction pulse signal S6 changes, the relative phase of the DC reproduction pulse signal S6 with respect to the video signal does not change.

Therefore, video signals can always be reproduced with constant phase relationship,
It is possible to obtain a video signal with no fluctuation in black level.

Furthermore, the difference in phase between the DC reproduction pulse signal 86'+87 when the television camera head 2 is connected and when it is not connected is such that the test signal that replaces the video signal introduced into the signal processing device 4 when the television camera head 2 is not connected is Since the ripples mentioned above are not included, no actual damage will occur.

As explained above, according to the present invention, it is possible to obtain a DC reproduction method for a television camera device that does not cause DC level fluctuations and can obtain a DC reproduction pulse signal even when the television camera head is connected or disconnected. .

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing an embodiment of the DC regeneration method of a television camera device according to the present invention, FIG. 2 is a circuit configuration diagram showing the clamp pulse generation circuit of FIG. 1, and FIG.
to g are signal waveform diagrams of various parts explaining the circuit operation of FIG. 1. In the figure, 2 is a television camera head, 4 is a signal processing device, 6 is a camera cable, 8 is a horizontal deflection circuit, 10 is an image pickup tube, 12 is a horizontal deflection coil, 14.18 is an amplifier, 1
6 is a flyback pulse sending circuit, 20 is a clamp circuit, 24 is a clamp pulse generating circuit, and 26 is a horizontal phase adjustment circuit.

Claims (1)

[Claims] 1. In a DC reproduction method of a television camera device in which a reference level portion of a video signal derived from a television camera head via a transmission cable is maintained at a predetermined DC level in accordance with a DC reproduction pulse by a signal processing device, the television means for introducing a phase detection signal of pulses generated by horizontal deflection of the camera head into the signal processing device via the transmission cable; and a means for supplying the phase detection signal and the horizontal drive signal to the television camera head to the signal processing device; If connected, means for generating a DC reproduction pulse in synchronization with the phase detection signal, and if the television camera head is disconnected from the signal processing device, means for generating a DC reproduction pulse in synchronization with the horizontal drive signal. 1. A direct current reproduction method for a television camera device, comprising means for generating a reproduction pulse.