JPS6365274B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a television camera with an improved blanking method.

Conventional configuration and its problems The camera blanking method for television cameras is to keep the beam current control electrode potential below the cut-off potential during the horizontal and vertical retrace periods to prevent the electron beam from being emitted from the triode. _G1 blanking method, which scans the effective scanning area during the retrace period to prevent reading the accumulated charge, or by keeping the cathode potential higher than the target potential during the horizontal and vertical retrace periods. A cathode blanking method is known that prevents the electron beam emitted from the triode from reaching the target, and the cathode blanking method is generally used because it requires a small voltage value of the pulse to be applied to each electrode. has been done.

First, FIG. 1 shows the scanning trajectory of the electron beam on the target surface in these two methods. In the figure, 7 indicates the entire image pickup tube target, and 8
indicates the effective scanning portion. The electron beam scans the screen along the trajectories 1, 1', 2, 2', . . . 5, 5', 6 in the direction of the arrow. Here, 1,
The solid line trajectories labeled 2, 3, 4, 5 indicate the effective scanning trajectories, and the dotted line trajectories labeled 1', 2', 3', 4' and 5', 6. The trajectories of dashed dotted lines with symbols indicate the trajectories in the horizontal retrace period and the trajectories in the vertical retrace period, respectively, assuming that the electron beam reaches the target surface during the retrace period.

Next, the cathode blanking method will be specifically explained.

Figure 2 shows an example of a conventional specific circuit implementing the cathode blanking method, in which negative horizontal pulses and vertical pulses are applied to terminals 9 and 10, respectively, the waveforms of which are shown in Figure 3 a and b. and are led to the base of the switching transistor Tr ₁ via a coupling capacitor C ₁ and a resistor R ₁ and a coupling capacitor C ₂ and a resistor R ₂ , respectively. transistor
The emitter of Tr ₁ is connected to the +B power supply applied to terminal 11, and the base is also biased to the same potential as the emitter by resistor R ₃ , so when a negative pulse is applied to the base, transistor Tr ₁ Conducting, a pulse similar to the waveform shown in FIG. 3c is generated at the collector, which is connected to ground through resistor R ₄ . This pulse is led to the cathode of the image pickup tube from the terminal 12 via the emitter follower transistor _Tr2 , and is used as a cathode blanking pulse.
Note that the resistor _R5 is the emitter resistance of the transistor _Tr2 , and the value of the +B power supply potential +B is set to a value sufficiently higher than the target potential V _T of the image pickup tube, as shown in the waveform diagram in Figure 3c. Therefore, the scanning beam is prevented from reaching the target during the retrace period.

FIG. 3a shows a horizontal pulse, H represents one horizontal scanning period, Hr represents a horizontal retrace period, and Ha represents a horizontal read scanning period. Further, FIG. 5B shows a vertical pulse, where V represents one vertical scanning period, Vr represents a vertical retrace period, and Va represents a vertical read scanning period.
Generally, the Ha and Va periods are made wider than the effective horizontal scanning period and vertical scanning period of the television standard to provide some margin, and blanking processing is performed in an electric circuit to produce a signal that passes the standard. It is true.

This blanking method has been widely used since it is simple, but it allows the transistor to be operated at a relatively high voltage (more than the image pickup tube target voltage (approximately 30 to 40 V), generally more than 50 V). The horizontal blanking period according to the television standard is NTSC.
Since the period is relatively short at approximately 11 μs, there is little margin for increasing the pulse delay and pulse width allowed by the switching transistor, and the collector resistance R ₄ of the switching transistor Tr ₁ shown in Fig. 2 is small. and the emitter resistance of the emitter follower R ₅
The value of must be kept small to some extent to allow current to flow through the transistor. In other words, it requires high voltage and relatively large current, which has the disadvantage of increasing power consumption. This is true for color television cameras such as recent single-tube color television cameras that perform some kind of signal readout such as obtaining information on optical black areas during the horizontal blanking period in the television standard. This is a drawback that cannot be ignored because a very narrow value is required.

OBJECTS OF THE INVENTION The present invention eliminates the above-mentioned drawbacks of the conventional technology and provides a device that can substantially perform camera blanking without using a conventional camera blanking circuit such as a cathode blanking circuit. The purpose is to

Structure of the Invention In the present invention, when scanning the photoelectric conversion surface of an image pickup tube with a scanning electron beam, the operation is particularly special during the retrace period. It is characterized in that the conversion surface is scanned and returned to the next horizontal scanning start position, and at the same time, the portion other than the effective scanning surface is scanned during the vertical retrace period and returned to the next vertical scanning starting position.

DESCRIPTION OF THE EMBODIMENTS The working material of the present invention will be explained with reference to the scanning locus of the electron beam on the target plane shown in FIG. The electron beam is 13, 13', 1 as shown by the arrow.
3″, 13, 14, 14′, 14″, 14,…
...Scan the target surface along the trajectory of 17, 17', 17'', 17.13, 14, 15, 1
The solid lines labeled 6 and 17 indicate the effective scanning locus, which is the same as in the conventional example. 13',1
3'', 13, 14',...16', 16'', 16
The dotted lines labeled with the symbols 17', 17'', and 17 indicate the scanning loci during the horizontal blanking period, and the dashed lines labeled 17', 17'', and 17 indicate the scanning loci during the vertical blanking period. Unlike the retrace period, the electron beam reaches the target surface and reads the charge.

To explain in detail one horizontal scanning period, the locus of the effective scanning period indicated by 14 solid lines is the same as before. After the effective scanning is completed, the target is rapidly scanned vertically as indicated by the dotted line at 14' in the direction of the target that has already been scanned, and then horizontally as indicated by the dotted line at 14''. The target surface that has been scanned (this surface is the target surface that was scanned approximately one horizontal scan period ago) is scanned and returned to the original lateral position. One horizontal scanning period ends with rapid vertical scanning as shown by the dotted line.

When such scanning is performed, even if the electron beam reaches the target during the horizontal retrace period, it will reach the part that has already been properly read.
The signal is barely readable. In other words, assuming that the part for which normal reading was completed n horizontal scanning periods ago is scanned during the horizontal retrace period, and that all the signal charges accumulated up to that point are read in one scan, the NTSC system In this case, only n/262.5 of the signal read during normal scanning (scanning during the effective scanning period) can be read during scanning during the horizontal retrace period, and since the entire screen is scanned in the same way, the uniformity of the screen is affected. has no effect, n is 10
If it is below this level, there is no problem in practical use.

On the other hand, during the vertical retrace period, after the end of the effective scan of 17, it scans suddenly in the horizontal direction to a part other than the effective scanning surface as shown by the locus of the dashed-dotted line at 17', and then moves to the dashed-dotted line of 17'. As shown, the part other than the effective scanning surface is scanned vertically to return to the vertical position at the start of vertical scanning, and again, as shown in the locus of the dashed dotted line in 17, it is rapidly scanned horizontally to complete one vertical scanning period. When such a scan is performed, even if the electron beam reaches the target during the vertical retrace period, it will read the charge in the area other than the effective scanning area, so although the signal will be read, it will not reach the effective scanning area. It does not affect the image in any way and there is no problem. However, the signal is read out and the signal of the part scanned during this period also changes depending on the amount of incident light, so a large signal is output and the signal is There is a possibility that there will be an adverse effect on the processing stage.Therefore, it is desirable that the target surface scanned during this period be a place where the amount of signal read out is as small as possible.For example, as shown in FIG. In the case of an image pickup tube with a part of the optical black part 32, if this part is scanned, only the dark current will be read out, the readout signal will be small, and the above-mentioned problem will be less likely to occur. 3 in the diagram
3 indicates an effective scanning section.

The above screen scanning situation will be further explained using the scanning waveforms shown in FIGS. 5 and 6. FIG. 5a shows a horizontal scanning waveform, and FIG. 5b shows a vertical scanning waveform in one horizontal scanning period. That is, the period 18 to 20 represents one horizontal scanning period H. The period 18 to 19 represents the effective scanning period Ha, and corresponds to the scanning indicated by the solid line 14 in FIG. 4, for example. Reference numeral 19 represents the switching time between the effective scanning period and blanking period of horizontal scanning, and as shown in waveforms 21 and 22 of FIG. This value corresponds to the scanning of the dotted line 14' in FIG. The period 19 to 20 represents the horizontal retrace period Hr, and the vertical scanning waveform during this period is maintained at the value approximately one horizontal scanning period ago, as shown in the waveforms 22 to 23 in FIG. 20 corresponds to the scanning of the dotted line at 14'' in the middle. Also, 20 represents the switching time between the retrace period and the effective scanning period, and as shown in the waveforms 23 to 24 of FIG. , the vertical scanning waveform is returned to the value 24 corresponding to the next effective scanning start position, which corresponds to the dotted line in FIG. In this method, V _v /262.5 indicates the amount of change in vertical scanning in one horizontal scanning period. However, V _v is the vertical scanning waveform in one vertical scanning period V, as shown in the waveform diagram in Figure 6a. represents the change value of

FIG. 6a shows a vertical scanning waveform for one vertical scanning period V, and the fine changes in one horizontal scanning period shown in FIG. 5a are omitted. Also, Figure 6b is 1
Showing the horizontal scanning waveform in the vertical scanning period, 25 to 2
The waveform in the vertical effective scanning period Va represented by period 6 is a continuation of the waveform shown in FIG. 5a, and
13, 13', 13'',...16'', 1 in Figure 4
It corresponds to 6 and 17 scans. 26 represents the switching time between the effective scanning period and blanking period of vertical scanning, and as shown in waveforms 28 to 29 of FIG. 1 in Figure 4.
This corresponds to the scanning of the dashed dotted line 7'. 26-2
The period 7 represents a vertical retrace period, and the fact that the scanning is returned to the starting position in the vertical direction during this period is the same as in the conventional example. On the other hand, the horizontal scanning waveform during this period is maintained at a value that scans the portion other than the effective scanning area, as shown in waveforms 29 to 30 in FIG. 6b, and the scanning during this period is as shown in FIG. 27 corresponds to the scanning of the dashed-dotted line. Also, 27 represents the switching time between the vertical retrace period and the effective scanning period,
As shown in waveforms 30 to 31 in FIG. 6b, during this time the horizontal scanning waveform is momentarily changed from the value that scans the area other than the effective scanning area to the value 31 that starts the next effective scanning. This corresponds to 17 scans in Figure 4.

If the above-described scanning is performed, there is no need to perform an operation to prevent the scanning electron beam from reaching the photoelectric conversion surface during the retrace period.

FIG. 8 shows a block diagram of a deflection circuit for an electrostatic deflection type image pickup tube for performing the above-described scanning operation. A sawtooth wave voltage with a horizontal period as shown in FIG. 9a is applied to the terminal 34 in FIG. 8.
The terminal 35 becomes high level during the vertical effective scanning period Va as shown in FIG.
A vertical periodic pulse that goes low level is applied to the signal. Then, the gate circuit 38 outputs a horizontal sawtooth wave voltage a for the vertical effective scanning period Va, and the vertical retrace period Vr is fixed at the potential at the end of the horizontal effective scanning.The waveform is as shown in FIG. 9e. appears at the output of the gate circuit 38. This output is connected to the amplifier 40 (amplification degree A ₁ ) and the inverting amplifier 41
(The degree of amplification is -A ₁ ) and after being amplified, the signals are guided from terminals 44 and 45, respectively, to a pair of horizontal deflection electrodes of an electrostatic deflection type image pickup tube.

Further, a vertically periodic sawtooth wave voltage as shown in FIG. 9c is applied to the terminal 36. Terminal 37 has a horizontal effective scanning period as shown in FIG. 9d.
A horizontal periodic pulse is applied to Ha which becomes a high level and which becomes a low level during the horizontal retrace period Hr. These two waveforms are then added together by an adder 39, and a vertical sawtooth wave voltage with pulses added during the horizontal retrace period as shown in FIG. 9f is output. This waveform is led to and amplified by an amplifier 42 (amplification degree A ₂ ) and an inverting amplifier 43 (amplification degree -A ₂ ), and then connected to a pair of vertical deflection electrodes of an electrostatic deflection imaging tube from terminals 46 and 47, respectively. guided by.

Therefore, the scanning waveform of this electrostatic deflection type image pickup tube becomes the waveform shown in FIGS. 5 and 6, and the scanning motion as shown in FIG. 4 is realized.

That is, by simply adding the gate circuit 38 and the adder circuit 39, the present apparatus can perform electron beam scanning, making it possible to eliminate the need for a camera blanking circuit such as cathode blanking.

Note that if the addition balance of the two signals in the adder circuit in FIG. 8 is changed, the value of the pulse height V ₂ during the horizontal blanking period of the waveform f in FIG. can change the position of the photoelectric conversion surface scanned by the photoelectric conversion surface, and by changing the voltage value _V1 during the vertical retrace period of the waveform e in FIG. 9, the scanning position during the vertical retrace period can be changed. It can be set at the optimum position (for example, in an image pickup tube in which a part of the photoelectric conversion surface is provided with an optical black part, this part).

Effects of the Invention As described above, according to the present invention, a camera blanking circuit such as a cathode blanking circuit of a television camera can be omitted, and power saving can be achieved.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing how the electron beam scans the photoelectric conversion surface of the image pickup tube in a conventional television camera, and Figure 2 is an example of a conventional television camera achieving camera blanking using the cathode blanking method. The circuit diagram of the cathode blanking circuit for
The figure is a schematic diagram showing how an electron beam is scanned on the photoelectric conversion surface of the image pickup tube of a television camera according to an embodiment of the present invention. The figure is a front view of an image pickup tube target with an optical black part provided on a part of its photoelectric conversion surface, Figure 8 is a circuit diagram of the deflection circuit of the electrostatic deflection type image pickup tube, and Figure 9 is a waveform diagram of each part. It is. 38...gate circuit, 39...addition circuit, 40
~43...Amplifier.

Claims (1)

[Scope of Claims] 1. A first means for scanning a photoelectric conversion surface that has already been read and scanned with a scanning electron beam during a horizontal retrace period and returning it to the next horizontal scan start position, and a first means for effective scanning during a vertical retrace period. and second means for scanning a portion other than the surface and returning it to the next vertical scanning starting position. 2. The photoelectric conversion surface scanned by the first means that has already been read and scanned is the photoelectric conversion surface that has been read and scanned 1 to 10 horizontal scanning periods before. TV camera. 3. As a first means, in an electrostatic deflection type image pickup tube, the vertical deflection electrode potential during the horizontal retrace period is approximately 1 to 10
2. The television camera according to claim 1, wherein the television camera is configured to apply a pulse voltage that makes the potential substantially the same as the potential before the horizontal scanning period. 4. As a second means, in an image pickup tube in which an optical black part is provided on a part of the photoelectric conversion surface, a scanning electron beam is scanned over the optical black part during the vertical retrace period and returned to the next vertical scanning start position. A television camera according to claim 1, characterized in that: 5. As a second means, a patent claim characterized in that in an electrostatic deflection type image pickup tube, the horizontal deflection electrode potential during the vertical retrace period is maintained at a potential at which the scanning electron beam reaches a portion other than the effective scanning surface. A television camera according to item 1. 6. As a second means, in an electrostatic deflection type image pickup tube in which an optical black area is provided on a part of the photoelectric conversion surface, the horizontal deflection electrode potential during the vertical retrace period is set to the potential at which the scanning electron beam reaches the optical black area. The television camera according to claim 1, characterized in that the television camera is configured such that the television camera maintains its position.