JPS615691A - Registration correcting system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a registration correction circuit for a multi-tube type television camera 2. In particular, it relates to a driving method when applying a registration correction signal to deflection.

[Background of the invention]

Conventionally, when television broadcasting or high-quality images are required, each primary color (red, R, green, G,
A so-called three-tube color camera is used, which has an image pickup tube for each color (blue B). In Fig. 1, 11 is an objective lens, 12 is a three-color separation optical system, 13, 14.15
These are image pickup tubes corresponding to R, G, and B, and each output of these image pickup tubes 13°, 14.15 is amplified and subjected to signal processing to produce the final television signal. 3 above
In addition to tube cameras, there are two-tube and four-tube color cameras. A technique common to cameras using these multiple image pickup tubes is to superimpose the output image signals from each tube. There is a so-called registration technology. In general, television cameras that use image pickup tubes suffer from various graphical distortions due to errors in the electron gun processing of the image pickup tube, manufacturing errors in the deflection coil assembly, or related electro-optical distortions unique to the deflection system. Occur. As a method of correcting the above-mentioned graphical distortion, as shown in FIG. 2, a parabolic waveform 22 of a low order is superimposed on a deflection current waveform 21 to obtain a waveform 23, thereby performing registration adjustment. Conventionally, as a method of generating a deflection waveform, a circuit utilizing switching as shown in FIG. 3(a) is often used. In this switching method, the switch 31 is turned on with the pulse shown in FIG.
.

Turn off repeatedly. During the ON period, the DC power supply 34 supplies a stain current. Next, when the switch 31 is opened, the electromagnetic energy accumulated in the coil 32 causes resonance between the inductance of the deflection coil 32 and the capacitor 33, and a flyback pulse as shown in FIG. 3(e) is generated at both ends of the coil. When the switch 31 is closed again during the half period of the flyback pulse, the resonance is damped and the current increases linearly again as shown in FIG. In this switching type horizontal deflection circuit, the energy is transferred to the coil 32.
And between capacitor 33,! Since the power supply only needs to supply energy equal to the loss of the coil and switch, a highly efficient deflection circuit can be realized. Since this switching type deflection circuit consumes little power, it is widely used as a deflection circuit in many television cameras and receivers.

As described above, in conventional cameras, registration is adjusted by superimposing a registration correction waveform on this switching deflection circuit. The registration correction waveform includes relatively low-order distortion correction, that is, linearity between each tube as described above, as well as (a) skew, (b) pincushion distortion, (C) bow, and (d) as shown in Figure 4. 11 adjustments were made by combining amplitude, (e) centering, etc. Dotted lines in the figure indicate the direction and shape of movement on the screen.

However, with the above items, although low-order distortions such as those shown in Figure 4 can be corrected, high-order distortions with even higher frequency components remain, and there are areas where registration cannot be achieved, especially at the corners of the screen. This was causing a lot of problems. Registration accuracy requirements are getting higher year by year, but registration deviations can affect the resolution, especially in high-definition TV cameras where the scanning me is approximately 1000 lines or more, which is about twice the current TV system (525 lines). This has a large influence, and the required accuracy is approximately three times higher in the horizontal direction and approximately twice or more in the vertical direction.

As a countermeasure against this problem, in recent years, a digital registration method has been developed with the aim of correcting even high-order distortion (see Japanese Patent Laid-Open No. 57-2166).

This digital registration method, as shown in FIG. 5, is a method in which a television screen is divided into a horizontally divided sections and vertically divided into b sections, and a correction value is given to each of these squares. The correction values given to each square are sequentially read out in accordance with the scanning cycle. Furthermore, in this method, one correction value is given to each square, so it is necessary to obtain correction values by interpolation when scanning between adjacent correction values in the horizontal and vertical directions.

Interpolation in the horizontal direction is much simpler than in the vertical direction. In other words, the horizontal data sampling frequency is 172
It becomes a multi-continuous signal by passing it through the following low-frequency F wave filter. Although the vertical direction will not be described in detail in the present invention, it is necessary to perform the interpolation operation by combining a digital circuit and a multiplier type D/A converter, etc., as shown in Japanese Patent Application Laid-Open No. 57-2166. . As described above, the digital registration method can create a complex correction waveform corresponding to distortion, and is an extremely effective means for registration adjustment.

In order to correct such high-order distortion, it is necessary to superimpose a high-frequency current on the deflection coil. Furthermore, since the distortion correction current includes a DC component, the deflection coil and the drive circuit must be coupled with DC.

In conventional switching type deflection circuits, it is difficult to use direct current coupling for the distortion correction circuit. Therefore, a negative feedback type linear amplifier as shown in FIG. 6 has conventionally been used for this purpose. This allows the current flowing through the deflection coil 61 to be passed through the resistor 62.
is detected, fed back to the negative terminal of the differential amplifier 63, and causes the same current waveform as the input voltage waveform 64 to flow through the coil. The problem with this type of deflection circuit, compared to conventional switching type deflection circuits, is that it is linear amplification, so the flyback pulse during the retrace period (determined by the coil inductance, retrace period, and deflection current) is not sufficient. Since a covering power supply voltage (50 to 150 V) is not required, power consumption increases significantly. Next, explanation will be given using a specific example. FIG. 7 shows a current waveform (a) flowing through the deflection coil and a voltage waveform (b) across the coil. Now, assume that the deflection period is 30 μS, the retrace period is 5 μs, the coil inductance is 250 μH, and the deflection current is 0.8 App. An example of the configuration of the negative feedback type linear deflection circuit of FIG. 6 is shown in FIG. 7(e). First, the circuit shown in FIG. 7(C) will be briefly explained. The output of differential amplifier 71 is applied to a driver stage 72, and the output of the driver stage is further coupled to a power amplification stage 73. A deflection current (FIG. 7(a)) is supplied from the power amplification stage 73 to the deflection coil 61, the current waveform is detected by the resistor 62, and fed back to the positive terminal of the differential amplifier 71, forming a constant current drive circuit. are doing. As can be seen from the waveform in FIG. 7(b), the region that requires high voltage is only during the retrace period, so in the circuit of FIG. GB is automatically changed. This eliminates the need to constantly apply high voltage, resulting in a significant reduction in power consumption. Next, we will roughly estimate the power consumption of this deflection circuit. Since the current of the high voltage power supply +vI+ flows only in the region marked in FIG. 7(a), the average current is as follows. In reality, it is the through current of the output stage and the driver.

Since power must be supplied to stage 72, the total is about 30
Consumes ~35mA of current.

A similar calculation is performed for the low voltage power supply +Vt.

Low voltage power supply-VL is It is.

In reality, the increase will be 10 to 20% due to the presence of through current. − Next, estimate the required voltage value for each power supply. The high voltage power supply element Vm needs to have a magnitude greater than that of the flyback pulse. In this case, the flyback pulse is about 40V, so the power supply voltage needs to be 50 to 60V or higher with some margin. The low voltage power supplies +VL and -VL are determined by the drive voltage for flowing a high frequency correction current during digital registration, as well as the loss due to the direct current resistance of the coil. Now, if the maximum correction frequency is 5oOKHz and the maximum correction amount is 3%, the voltage to drive the coil is 500KH! Correction current (0.8AX0.63
= 24mA) is required. Therefore, the power supply voltage needs to be 24mAX790Ω-19V or more. Therefore, it is necessary to take a margin and set it to about 24 to 25 cm. When power consumption was calculated under the above conditions, it was approximately 2W for the high voltage section, approximately 5W for both positive and negative voltage sections for the low voltage section, and 7W in total.

Even in the circuit shown in FIG. 7(0), in which power consumption is reduced by switching the power supply during the retrace period between high voltage and low voltage, the power consumption is as high as J)7W per channel.

In contrast, with the Kurabe switching method, the current consumption is 50 to 70 mA (power consumption 350 to soomw) when the power supply voltage is 7V.
)Met.

As described above, the linear deflection circuit consumes much more power than the switching method.

Increased power consumption is an important factor that limits the operating time of small cameras, especially vertical cameras used outdoors (powered by batteries). Therefore, there has been a need for a deflection method that consumes as little power as conventional methods and allows digital registration.

[Purpose of the invention]

An object of the present invention is to provide a distortion correction method that can be applied to digital registration that can perform high-order distortion correction while using a deflection circuit with low power consumption like the conventional switching method.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail using Examples.

FIG. 8 shows an example of the structure of a deflection coil used in the present invention. For convenience of explanation, FIG. 8 shows only the horizontal or vertical deflection coil, and the other orthogonal deflection coil,
Focusing coils, alignment coils, etc. are omitted. It is assumed that the electron beam travels in the Y-axis direction. A sub-deflection coil 82 for registration correction is provided so as to be offset from the center axis X1 of the main deflection coil 81 and such that the coil center (axis X2) is located within a plane constituted by the XY axes. Main deflection coil 8
1 is driven by a conventional switching type deflection circuit. Only the registration correction waveform is applied to the sub-deflection coil 82. The registration correction waveform shares only an amplitude corresponding to several percent of the deflection waveform applied to the main deflection coil 81. By doing this, the main deflection coil 81
The magnetic field generated by the sub-deflection coil 82 is added to the magnetic field generated by the sub-deflection coil 82, and a combined magnetic field acts on the electron beam passing through the coil. By simply connecting the sub-deflection coil 82 and the sub-deflection coil drive circuit with a DC connection, the DC component during digital registration can be applied to the scanning beam. The drive circuit for the sub-deflection coil 82 may be similar to the circuit shown in FIG. Since the drive power of the sub-deflection coil 82 is only a few percent of the main deflection power, the deflection current is also small and does not pose much of a problem in terms of power. As described above, by separating the main deflection coil drive circuit and the sub-deflection circuit for registration correction, the problem of power consumption, which is a drawback of the conventional linear amplification type, can be solved, and it can also be applied to small vertical cameras. It was possible to do so.

i Here, the relationship between the main deflection coil and the sub-deflection coil will be explained in more detail. The central axis Xs of the sub-deflection coil 82 is the central axis X of the main deflection coil 81! If the coils are placed coaxially with the coils, electromagnetic coupling will occur and the coupling coefficient M will become large. Therefore, as described above, it is necessary to arrange both coils offset by a distance t.

This distance t may be determined based on the magnetic field distribution of the deflection coil, etc. FIG. 9 shows an example of the magnetic field distribution of the deflection coil. The vertical axis indicates the magnetic field strength H1, and the horizontal axis Y indicates the position on the tube axis. Magnetic field 91 created by the main deflection coil and magnetic field 92 created by the sub-deflection coil
The distance t from the main deflection coil magnetic field 91 may be set by setting the central axis X2 of the sub-deflection coil magnetic field 92 at a position where the main deflection coil magnetic field 91 is sufficiently reduced.

Next, an embodiment of the present invention using the deflection coil shown in FIG. 8 described above will be described.

First, we will discuss differences in registration correction methods due to differences in focusing methods. There are two types of beam focusing methods: electromagnetic and electrostatic. In the case of electrostatic focusing, as shown in FIG. 10, a horizontal registration correction waveform generator 102 and a vertical registration correction waveform generator 103 are connected to a coil assembly 101 arranged as shown in FIG. Just add a correction current. The main deflection coil has a horizontal
Needless to say, a sawtooth wave current is applied to the vertical deflection circuits 106 and 107.

In the electromagnetic focusing method, a focusing magnetic field Hv is applied in the tube axis direction as shown in FIG. 11(a). Therefore, the scanning electron beam advances toward the target while rotating in the tube axis direction as shown by a trajectory 111. In the present invention, the center of the main deflection coil and the center of the sub-deflection coil are arranged with an offset of t, so when used together with the electromagnetic focusing method, as shown in Fig. 11, etc., the registration correction direction on the screen is the main direction. It deviates from the deflection direction by an angle α.

Therefore, in the case of electromagnetic focusing, as shown in FIG. 12, the outputs of the horizontal correction waveform generator 102 and the vertical correction waveform generator 103 are added to the matrix circuit 108, and the following equation is calculated. Now, let the horizontal correction output be DB1, the vertical correction output be Dv, the matrix outputs be DB/, DV/, respectively, and the angles of main deflection and sub-deflection be α, then Dm'=Dm +Dv tanα...
・・・・・・・・・(1) Dv'=Dv −Da ma
・−・Old−・・・(2). If the outputs Di/ and DV/ passed through the matrix circuit 108 are applied to the drive circuits 104 and 105, respectively, the deflection can be made in the same direction as the main deflection direction.

〔Effect of the invention〕

As described above, if the main deflection and digital registration correction are performed separately as in the present invention, an efficient switching method etc. can be adopted for the main deflection, and the drive power, which has been a problem in the past, can be significantly reduced. can be reduced to In addition, since the main deflection and sub-deflection can be designed separately, it is easy to extend the frequency band, and the inductance of the sub-coil can be reduced to reduce circuit instability caused by oscillation, which is unique to negative feedback amplifiers in the near amplifier method. Therefore, it is possible to take the resonance point out of the band, which is very advantageous.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the basic configuration of the three-tube type, Fig. 2 is an explanatory diagram of conventional registration adjustment, Fig. 3 is an explanatory diagram of a conventional switching type deflection circuit, and Fig. 4 is an explanatory diagram of conventional registration items. Fig. 5 is an explanatory diagram of digital registration, Fig. 6 is an explanatory diagram of a linear amplifier type deflection circuit, Fig. 7 is a waveform and specific circuit diagram of a linear amplification type deflection circuit, and Fig. 8 is an explanatory diagram of the linear amplification type deflection circuit. A structural diagram of one example of a deflection coil used in the present invention, FIG. 9 is a diagram explaining the magnetic field distribution of the coil used in the present invention, and FIG. 10 is a block diagram showing an embodiment of the present invention in the case of an electrostatic focusing method. 11 is an explanatory diagram of the operation in the case of the electromagnetic focusing method, and FIG. 12 is a block diagram of an embodiment of the present invention in the case of the electromagnetic focusing method. 81... Main deflection coil, 82... Sub deflection coil,
101... Coil assembly, 102... Horizontal registration correction waveform generator, 103... Vertical registration correction waveform generator, 104... Horizontal registration drive circuit, 1c5
. . . Vertical register drive circuit, 106 . . . Horizontal deflection circuit, redundancy 1st (α;

Claims (1)

[Scope of Claims] 1. A deflection coil assembly that separately includes a main deflection coil through which a sawtooth wave current flows and a sub-deflection coil for image distortion correction, a drive circuit that supplies the sawtooth-wave current, and the sub-deflection coil. A registration correction method characterized by comprising a drive circuit that supplies a correction current to a deflection coil and a generation circuit that generates a correction current waveform. 2. A registration correction method characterized in that in the deflection coil assembly according to claim 1, the winding centers of the main deflection coil and the sub-deflection coil are deviated in the tube axis direction of the image pickup tube. 3. In the registration correction method described in claim 1, when supplying the waveform to the correction current drive circuit, the waveform is supplied via a matrix circuit that calculates a horizontal correction waveform and a vertical correction waveform. A registration correction method characterized by: