JPS5835435B2 - Focusing device for color television camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In a multi-pickup tube color television camera using a magnetically focused pickup tube, it is necessary to accurately control each parameter of the related pickup tubes from the standpoint of positional alignment.

These parameters include the mechanical configuration of the focusing coil, the current in the focusing coil, and the G-37G-4 voltage ratio of each pickup tube.

Here, G-3 represents the voltage of the focusing cylinder, and G-3
4 represents the field mesh voltage.

The present invention relates to an inexpensive device that can easily adjust each of these parameters.

In each pickup tube in a multi-pickup tube camera there is a focusing cylinder G-3 and a field mesh G-3.
-4 is included.

The ratio of the voltages applied to these two electrodes affects the performance and characteristics of the tube, such as beam spotting error, focusing at the center and corners, and the size of the reproduced image.

The electrical focusing of the scanning beam of the pickup tube is (a) G
This is done by either adjusting the -3 voltage and G-4 voltage all at once so as to maintain a constant ratio, or (b) adjusting the current in the focusing coil.

Preferably, the focusing control of the camera is performed remotely by a digital controller using a microprocessor.

Each voltage of G-3 and G-4 is about 1000 volts,
The accuracy required is such that it is impractical to derive a digital signal representative of this high voltage from a low voltage fliljaitl device such as that used in conjunction with a digital controller.

Focusing of the tube is accomplished by individually supplying a splitting current to each focusing coil.

This type of device has the disadvantage that there is a mutually different transition between the currents of the focusing coils, which results in alignment errors.

According to the present invention, these problems can be solved by providing the majority of the focusing field for the vessel by three main focusing coils connected in series to a common regulated current source. .

The adjustable component for focusing the tube device with each focusing coil is provided by a separate sub-focusing coil included in each yoke focusing coil assembly.

As previously mentioned, a digital control device, such as an 8-bit binary code, generates, for example, 256 levels of control voltage.

For typical equipment, the maximum voltage level is 5 volts (-5
to +5 volts).

With electronic focusing, this 5 volts must be expanded to a maximum voltage of around 1000 volts.

The accuracy required for G-3 and G-4 voltage is approximately 0.1%
It is.

Such large voltage magnification factors result in inaccuracies, which makes such an arrangement impractical when such precision is required.

Alternatively, the focusing of the vessels can be achieved by individual current control of each focusing coil.

The advantage of this method is that the control means for controlling each focusing coil at a relatively low voltage can be easily matched to the output of a low voltage digital controller, thus requiring a large voltage magnification factor with inaccuracies. The point is that it does not require .

The disadvantage of this approach is that there is a differential displacement in the current in each focusing coil, resulting in alignment errors because the three color tubes are uncorrelated.

The present invention relates to a focusing device which can largely or completely eliminate the drawbacks of the two systems mentioned above.

Hereinafter, this invention will be explained with reference to the drawings.

A composite focusing coil arrangement is shown in FIG. 1, with a red tube 1-0, a peripheral tube 11, and a blue tube 13 shown.

Also shown are the focusing cylinder and field mesh electrodes for each of these pickup tubes.

The focusing cylinder of tube 10 is 10a. Field of tube 10
The mesh electrode is 10b.

Similarly, the focusing cylinder of tube 11 is 11a, the field mesh electrode is 11b, the focusing cylinder of tube 13 is 13a,
The field mesh electrode is 13b.

15 (G-4) is field mesh electrode 1 (lb
, 11b, and 13b.

This voltage source supplies a voltage directly in parallel to the mesh electrodes.

The voltage from the power supply 15 is also passed to the focusing cylinder electrode 10 via a voltage divider tap of a resistive voltage divider network consisting of resistors R0 and R2.
a, 11a and 13a in parallel.

The voltage ratio of G-3 and G-4 is a function of the ratio of these resistors R1 and R2.

The ratio of these resistors R1 and R2 affects the performance and characteristics such as the beam arrival point error, the focusing state at the center and corners, and the dimensions of the reproduced image, and as described above, the desired G-37G
-4 ratio.

The voltage supplied is approximately 700 volts for the focusing cylinder and approximately 1000 volts for the field mesh electrode.
It is about the size of a bolt.

A focusing magnetic field for the tube is provided by a focusing coil mounted on the yoke structure.

A focusing coil, shown schematically as focusing coil 20 in FIG. 1, is disposed in a yoke provided around the tube 10.

Similarly, the focusing coil 21 is arranged around the tube 11 and the focusing coil 23 is arranged around the tube 13.

According to the invention, these focusing coils 20, 21 and 23 are connected in series to provide a common constant regulated current source 25.
is combined with

According to the technical idea of the invention, the majority of the focusing magnetic field for the vessel is generated by each of the three main focusing coils 20, 21, 23 associated with one another connected in series to a common regulated constant current source 25. generated by one.

This "most of the focusing magnetic field" means, for example, that approximately 95% of the total focusing magnetic field is generated by these three main focusing coils 20 connected in series.
, 21.23.

Additionally, three separate sub-focusing coils are provided in the focusing coil assembly of each yoke.

These sub-focusing coils are indicated schematically by 30, 31, and 33 in FIG.

These sub-focusing coils are connected to independent sub-focusing current sources 40,4.
1, and 43.

Coil 30 is coupled between this secondary source 40 and ground or a reference potential point.

Coil 31 is coupled between sub-focused current source 41 and ground, and coil 33 is coupled between sub-focused current source 43 and ground.

A red copper control signal from digital controller 50 is supplied to sub-focusing current source 40 .

The digital signal supplied to the sub-focusing current source 40 is, for example, an 8-bit signal representing one of 256 levels.
In the form of digital codes, these codes are sensed by sub-focused current source 40 and converted to produce analog current levels corresponding to the binary digital control signal.

Another 8-bit code signal similarly generated by the digital controller 50 is supplied to the green sub-focusing current source 41;
Another 8-bit signal generated from digital control signal 50
The code signal is supplied to the front focused current source 43.

This digital control device 50 may be provided at the operator's location or at the location where the camera device is installed.

The digital control device may, for example, include three analog-to-digital converters, which are responsive to three separate voltage values provided by potentiometer settings.
Generates a bit decile code signal.

Each sub-focusing current source 40, 41, or 43 is provided with a digital-to-analog converter to convert the 8-bit digital code signal to an analog level.

This represents the code that is fed directly to the coil in the form of current levels.

This code can also be converted through a scaler with a certain conversion factor to the appropriate current level that is supplied to the sub-control coil.

Since 95% of the focusing magnetic field of each of the red, green, and blue main focusing coils is supplied by a common bias current source 25 connected in series with the main focusing coils, the phases in the individual focusing magnetic fields of the pickup tubes are The differential drift is reduced to O as far as the main focusing field is concerned.

The sub-focusing fields drift with respect to each other.

However, since these sub-focusing fields account for only a small portion of the total focusing field required, the overall stability problem is significantly reduced.

Because the number of turns on the sub-focusing coil is small, the impedance of the coil is small and can be easily driven by a low level signal provided by the digital controller 50.

Refer now to FIG.

FIG. 2 schematically shows a sectional view of the tube itself and the yoke assembly of the container shown in FIG.

Sub-focusing coils such as 30, 31° and 33 in FIG. 1 are wound by an automatic coil winding machine directly onto the inner surface of a focusing coil spool 60 made of dielectric material and generally in the shape of a spool. It is formed as a single layer consisting of thin wires (for example, wire No. 32).

The single layer can be precisely placed to form a precise cylinder for winding the coil that generates the main or major focusing field.

For example, the main or most focusing magnetic field generating coil consisting of 20, 21, and 22 in Figure 1 is constructed by directly winding a relatively large diameter wire (for example, No. 23 wire) in 6 layers on the sub-focusing coil. This is the remainder and occupies the majority of the total winding amount.

The relatively large diameter of the wire results in a relatively small number of layers and a relatively small number of turns per layer, making it easy and accurate to wind using commercially available automatic winding machines. A winding structure that can be rotated can be realized.

The advantages gained by using large diameter wire to wind the focusing coil are extremely important in achieving a high degree of winding precision.

However, a large diameter wire coil (low impedance) with a non-mixed configuration alone cannot achieve the objectives of the present invention, which are accurate winding, high stability, and easy implementation.

The device with the above-mentioned secondary and main focusing coils has the above-mentioned advantages of being able to reduce manufacturing costs and achieve high accuracy.

As used herein, the term ``majority of the focused magnetic field'' includes proportions other than the aforementioned 95%, meaning that the majority of the focused magnetic field is associated with coils 20, 21, and 23. It should be understood that it includes all percentages that indicate.

That is, the majority collectively refers to the rate at which the amount of shift of the focusing currents in the sub-focusing coils has a negligible effect.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a focusing coil device for a camera according to the present invention, and FIG. 2 is a schematic sectional view of the focusing coil device for a single tube. 10.1113・・・Pickup tube, 20゜2
1.23... Main focusing coil, 25...
Common stabilizing current source, 30, 3L33... Sub-focusing coil, 40.4L43... Width focusing current source (
Means for supplying an adjustable current to each sub-focusing coil. ), 50...Digital control device (means for supplying adjustable current to each sub-focusing coil).

Claims (1)

[Claims] 1 A plurality of video pickup tubes, a plurality of main focusing coils each provided on a yoke structure installed surrounding each video pickup tube, and a common coil to which these main focusing coils are connected in series. a regulated current source, a plurality of sub-focusing coils each mounted on a yoke structure surrounding each of the image pickup tubes, and a low-power, low-voltage source for each sub-focusing coil. means for supplying an adjustable current of 100 to 500 nm, so that each said primary focusing coil generates a majority of the required focusing field for each pick-up tube, and each of said secondary focusing coils generates a majority of the required focusing field for each pick-up tube. A focusing device for a color television camera that generates only a small portion of the focusing magnetic field and is capable of electronic focusing using a low voltage source without stability problems.