JPS60258832A - Image pickup tube - Google Patents

Abstract

PURPOSE:To improve the registration accuracy and to obtain an image pickup tube for three-tube camera having high resolution by splitting the electrode into four then lapping the micro voltages synchronous with the deflection over respective electrode. CONSTITUTION:A portion of tubular electrode in MM image pickup tube is splitted into four by 90 deg. to provide an electrode I for correcting registration. Min deflection is performed through function of field to be produced by a deflection coil 209 provided at the outside of image pickup tube while the correction of registration is performed through function of electric field by applying bias voltage overlapped with the voltages + or -VH/2, + or -VV/2 onto two pairs of correction electrodes I. Here, the voltages VH, VV required for correcting registration are sufficiently low and easy in view point of drive circuit. Main deflection is facilitated for higher bias voltage thereby the diameter of electron beam can be reduced resulting in high resolution.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an electromagnetic focusing/electromagnetic deflection type image pickup tube, and is particularly used in a three-tube color camera to improve registration (superposition of video signals) N degree. Regarding the image pickup tube that can be used.

[Background of the invention]

FIG. 1 shows the arrangement of the optical lens, color separation optical system, and image pickup tube of a three-tube color camera. Light from object 101 (Y)
is incident on the optical lens 102, and the prisms 103 and 10
4,105. and dichroic filter 106,1
07, the light is separated into three colors of red (R), green (G), and blue (B), and the light is sent to the image pickup tubes 108, 109, and 110, respectively.
imaged onto a photoconductive target. This optical image is scanned by an electron beam within the imaging tube and converted into an electrical video signal corresponding to the optical image.

Figure 2 shows the electromagnetic focusing/electromagnetic deflection (hereinafter abbreviated as MM) of the Jurai used as the image pickup tube of 108, 109, and 110.
2 is a schematic cross-sectional view of a shaped image pickup tube, a focusing coil, and a deflection (2) coil. thermal cathode 2
The electron group emitted from 01 is controlled by the first grating 202, accelerated by the second grating 203, and restricted by a microhole (not shown) of about 10 to 50 μm provided at the center of the beam disk 204. It becomes a narrow electron beam. The electron beam is focused on the photoconductive targeter 1-208 by the action of a magnetic field created by a focusing coil 207 provided outside the vacuum vessel 206, while being accelerated by the third grating 205 of voltage EC3(v). Also, this electron beam
The photoconductive target 208 is deflected by the action of a magnetic field generated by two pairs of deflection coils 209 provided outside the image pickup tube, and the photoconductive target 208 is scanned, and a video signal corresponding to the optical image is read out from the target.

FIG. 3 shows the structure of the deflection coil 209 in detail. The deflection coil is composed of a pair of horizontal deflection coils 301 and a pair of vertical deflection coils. The horizontal deflection coil and the vertical deflection coil are 1. - The coils are rotated 90 degrees around the tube axis as the central axis, and the magnetic fields generated by each coil are orthogonal to each other. Furthermore, the current flowing through each of the deflection coils (3) is basically a sawtooth current as shown in FIG. Note that the horizontal axis in Figure 4 is time;
The vertical axis is current.

In this MM type image pickup tube, when the accelerating voltage EC3 is increased, the current required to deflect the electron beam to the periphery of the scanning area (hereinafter abbreviated as deflection current) gradually decreases in proportion to Ec3 to the 172nd power. Therefore, even at a relatively high acceleration voltage (for example, Ec3=1500V), the deflection current does not increase much, and driving the deflection coil does not pose much of a problem. Therefore, with the MM type image pickup tube, a narrow beam can be obtained and high resolution can be achieved. However, this type of image pickup tube poses a problem in that it is difficult to improve registration accuracy, as will be described in detail below.

FIG. 5 schematically shows an example of signal processing in a three-tube color camera. 108°109.1 in Figure 1
R,G taken out from 10 imager tubes.

The video signals of B are transmitted through amplifiers 501 and 502°50, respectively.
3 and input to the color coder 504. Also, a synchronization signal S is simultaneously input to the color coder from the color synchronization signal generator 505 (4), and R
, G, B video signals are superimposed and modulated,
One video signal is obtained. In particular, this superposition of video signals is called registration.

FIG. 6 schematically shows the shape of the scanning area drawn by the electron beam on the photoconductive target.

The solid line C is the shape of the scanning area that should originally exist, and the broken line C is the shape of the scanning area drawn by the electron beam.

The deviation between the solid line and the broken line represents graphic distortion.

This figure distortion is caused by deflection aberration of the electron beam focusing/deflection system, distortion caused by insufficient assembly precision of the electron gun,
Distortion caused by disturbances in the windings of the deflection coil or focusing coil; distortion caused by misalignment of the respective axes of the deflection coil, focusing coil, and electron gun; and eddy currents generated in the third grating, causing the deflection magnetic field to It is a combination of distortions caused by disturbances, distortions caused by the influence of geomagnetism, etc.

Furthermore, the video signals of each of the R, G, and B channels appear in the form of superimposed distortions caused by geometric distortion and lack of precision (5) in the optical lens and prism system.

The graphical distortion of the video signal explained above has variations in each R, G, and B channel, so simply superimposing the RlG and B video signals will result in a signal with color shift, and the resolution of the camera will also be affected. to degrade. In order to correct this registration error, the current flowing through the horizontal and vertical deflection coils is usually corrected so that the graphic distortion of the G channel video signal matches the graphic distortion of the other R and B channels. The shape of the scanning surface drawn by the electron beam is changed. This is what is called registration correction.

An example of registration correction is given below. R2O,B
There is no graphical distortion in the optical system of each channel.

It is assumed that there is no graphical distortion in the B channel electron beam system. When an electron beam traces a scanning plane as shown in FIG. 7 in an R-channel image pickup tube, a current as shown in FIG. 8 is applied to the vertical deflection coil to perform registration correction.

Such a corrected current waveform includes a component of a high frequency (ω) several times to several tens of times as high as the (6) fundamental frequency of horizontal deflection. Furthermore, an image pickup tube for a high-definition camera with an increased number of scanning lines requires an even higher frequency.

Therefore, the input impedance of the deflection coil 2 (I Z
(l=Lω, L is the self-inductance of the deflection coil), that is, a problem arises in that the load on the deflection current drive circuit increases. In addition, for high frequencies ω, the mutual coupling between the horizontal and vertical deflection coils becomes stronger, and the correction waveform superimposed on the vertical deflection coil jumps into the horizontal deflection coil, causing disturbances in the horizontal deflection waveform and horizontal figure distortion. to occur. Furthermore, eddy currents are more likely to occur in the third grid electrode,
The linearity between the deflection current and the deflection magnetic field is disturbed, making registration correction difficult.

The above is the case where MM type image pickup tubes are used for each of the R, G, and B channels.

FIG. 9 shows the installation of an electromagnetic focusing/electrostatic deflection (hereinafter abbreviated as MS) type image pickup tube and focusing coil used for each of the R, G, and B channels. The operation of this image pickup tube (7) is almost the same as that of the MM type image pickup tube, but the difference is that the electric field created by the pattern yoke 901 is used for deflection.

FIG. 10 is a developed view of the pattern yoke.

Line segments AB and A'B' represent the same part. The pattern yoke has zigzag shaped horizontal deflection electrodes (H+, H-) and vertical deflection electrodes (V+).

It is made up of four electrodes (V-). Horizontal deflection electrode H+
and H− respectively have v o / 2 (V ) = −v
A voltage of H/2 (V) is superimposed on the vertical deflection electrodes V' and V-, respectively, and voltages of vv/2 (V) and -Vy/2 (V) are superimposed on the bias voltage Eca (V). Ru. In the MS type image pickup tube, the deflection voltage vHtvv is changed in a sawtooth pattern to generate a deflection electric field perpendicular to the tube axis to deflect the electron beam.

In the MS type image pickup tube, the four horizontal and vertical electrodes can be formed with good symmetry and high precision. Therefore, the capacitive coupling between the electrodes is balanced, and the registration correction waveform is less likely to jump to other electrodes.

Therefore, in the MS type image pickup tube, registration (8) It is possible to perform correction with high accuracy.

However, in the MS type image pickup tube, when the bias voltage Ec3 is increased in order to obtain high resolution, the deflection voltage vH9vv increases rapidly in proportion to EC3. In a normal deflection circuit, it is desirable that the deflection voltage is about 150 V or less; if it exceeds this value, the size of the circuit will increase rapidly and a transistor with high withstand voltage will be required. E
When C3 is about 500V, the peak value of horizontal deflection voltage vH is about 150V, and MM type image pickup tube (7) EC3=
Compared to 1500V Ic, it is difficult to increase the EC with an MS type image pickup tube. Therefore, it is difficult to obtain higher resolution with an MS type image pickup tube than with an MM type image pickup tube.

[Purpose of the invention]

An object of the present invention is to provide an image pickup tube for a three-tube camera that can improve registration accuracy and at the same time has high resolution.

[Summary of the invention]

The present invention uses an electrostatic registration correction method similar to that of the MS type image pickup tube in order to compensate for the drawbacks in the registration (9) correction of the MM type image pickup tube.

[Embodiments of the invention]

The present invention will be described below with reference to Examples.

As explained in the conventional example, the MMMM imaging tube body can have high resolution, but it is difficult to improve the registration accuracy in terms of circuitry.

On the other hand, in the MS type image pickup tube, in order to improve the resolution,
Although it is difficult to increase the acceleration voltage of the pattern yoke and the deflection voltage in terms of circuitry, it is easy to improve the registration accuracy.

In the present invention, the drawbacks of the two types of image pickup tubes are compensated for by compromising the two types. That is, the main deflection of the electron beam is performed by the action of a magnetic field created by a deflection coil provided outside the imaging tube, and the registration correction is performed by the action of an electric field from two pairs of electrostatic deflection electrodes provided inside the imaging tube.

Figures 11, 12, 13, 14, (10) FIG. 15 shows an embodiment of the present invention.

FIG. 11 shows an example in which a part of the circular fillifa pole of the MM type image pickup tube is divided into four parts each having a 90° angle, and an electrode (one part) for lens correction is provided.

Figure 12 shows the curvad ar
This is a case where 1 part of ro-shaped pattern is used.

FIG. 13 shows an example in which electrodes (one part) are formed on the inner wall of the vacuum container 206 by dividing the cylinder into 90° parts.
The figure shows an example in which a corvw arrow type pattern yoke (i' portion) is formed on the inner wall.

FIG. 15 shows an example in which the middle portion of the cylindrical electrode 215 is divided into four parts as shown in FIG. 16.

In any of the embodiments, the main deflection is performed by the action of a magnetic field created by a deflection coil 209 provided outside the picture tube, and the lens 1 to rayon correction is performed by applying two pairs of opposing electrodes (2) or (r') for correction. , a bias voltage of 1/21/21 is applied to the 1-1 of the bias voltage 1/3, and a voltage of 1/11 is applied to perform this by the action of an electric field.

In the above example, the voltage VH+VV required for registration correction is 4 minutes smaller, which is easier in terms of the drive circuit. Also, bias voltage 1! : When c3 is increased, the main deflection can be performed relatively easily, so the diameter of the electron beam can be reduced and high resolution can be obtained.

In addition, in the image pickup tubes shown in FIGS. 13 and 14, the vacuum container 20
Since it is formed by vapor-depositing metal such as chromium or aluminum on the inner wall of the
The thickness of the metal can be reduced to 1/100 or less compared to a normal MM type image pickup tube configured with a cylindrical electrode having a thickness of 1/1. Therefore, eddy currents within the electrodes caused by the deflection magnetic field can be reduced, the main deflection becomes easier, and graphic distortion caused by eddy current loss is also reduced.

〔Effect of the invention〕

As described above, according to the present invention, registration accuracy can be improved, so a three-tube camera with high resolution and little color shift can be realized. In particular, when used in a high-definition camera with an increased number of scanning lines, the effects of the present invention are extremely significant.

(12)

[Brief explanation of the drawing]

Figure 1 is a layout diagram of the optical lens, color separation optical system, and image pickup tube of a three-tube color camera. Figure 2 is a schematic diagram of an electromagnetic heat flux/electromagnetic deflection type image pickup tube. Figure 3 is a deflection coil. Fig. 4 is a waveform diagram of the deflection current, Fig. 5 is a schematic diagram of signal processing in a three-tube color camera, Figs. 6 and 7 are diagrams showing figure distortion, and Fig. 8 is a diagram showing the shape distortion. , corrected deflection current waveform diagram,
Figure 9 is a schematic diagram of an electromagnetic focusing/electrostatic deflection type image pickup tube,
Figure 0 is a developed view of the pattern yoke, Figures 11 to 15
The figure shows an embodiment of the present invention, and FIG. 16 shows a sectional view taken along line AA' in FIG. 15. 201... Hot cathode, 202... First lattice, 20
3... Second grating, 204... Beam disk, 20
5...Third grid, 206...Vacuum container, 207...
- Focusing coil, 208... Photoconductive target, 209
...Deflection (13) Fig. 1 Fig. 2 Fig. 3 Fig. %4-[21 Deflection%5 Fig. 6'f-J 7 (2) Fig. 6'f-J 7 (2) Fig. 9 Fig. 2θ2'jPl[) (2) vJII Figure VJ12 Figure 13 Figure I Figure 14 Figure 15 Figure I6 (2)

Claims (1)

[Claims] 1. An electron gun unit that includes a vacuum vessel, at least a cathode and an accelerating electrode provided inside the vessel, generates an electron beam, and controls the amount of current and emission angle of the electron beam; It has a target part that generates a corresponding electrical pattern, and an electrode for applying a voltage between the electron gun part and the target part. In an imaging tube that focuses a beam on a target, deflects the electron beam using two pairs of electromagnets provided outside the vacuum container, and extracts an electrical signal corresponding to an optical image from the target part, the electrodes are arranged in at least four. An image pickup tube characterized by dividing the electrodes and superimposing a minute voltage synchronized with the deflection on each electrode. 2. The image pickup tube according to claim 1, wherein the divided electrodes are formed using a conductive film on the inner wall of the vacuum container. (1)